A New Series of Text-Books. FOR MEDICAL STUDENTS. UNIFORM IN SIZE, PRICE AND BINDING. Price of Each Book, Cloth, $3.00; Leather, $3.50. MIDWI: sician Guy's " The illu as far super! "Sensible. " I have < to become c subjects tre and Gynacc PHYSIO olcgy 301 c; *' The wo H, P. Bowc " By his < every teacht MATER includi cial ar Notes . tions, ; Profess Surgeo This boo other Med of style and yet concise i of facts conv nostic hints, Special 1 treatment of alphabetical ing them, an CHILDR tal for i can E( Profess Pennsy Formul Artifici; " Nothing attention. F reads it with need scarcel} value, neithe cat Associate J^-SEH ] P. BLA MEDICAL ftric Phy- romen at, d this book it; York. book ought the various Midwifery of Physi- 50 pages. y."-Prof. >een felt by ;UTICS, tics, Offi- iFormulae, Examina- k., M.D., |isco, late |28 pages. than any ue features mplete and great mass tiulae, diag- iblished. \dex to the iken up in fcommend- ia Hospi- Ameri- Clinical 'ersity of ?hia. 50 ;, for the tie author's in, and one edside. It re of much {can Medi- iellers, 1012 WALNUT STREET, PHILADELPHIA. The New Series of Text-Books. Continued. PR W AL THERA PEUTICS, with an Index of Diseases By El A'tfta.'ff^sSa; rigSSrSte ----^--f on . C0 m no young physician can afford ,o' *%SS&3&SHSS& 7 * ^^ ^ l ^^-^^^^^^^^^^^^^ both o to, MEDICAL JURISPRUDENCE AND TOXICOT nrv (eSft E v S o E f P "' r eSSOTOf "^Svf^^riBSr'v suy of Pennsylvania, etc. Second Edition. Enlarged. ?SSffi3*&tfSS& win b re k ho D e one of the tw ? or thre < Ieadin s "" cnsic medicine, which, inviting ?1d j^ortent Th F'T a 1 ""P 8 "". to the st dy of for- ^SS^^SfiSS;2&22S?^f L^".^r^v!;^4;r ftSjJ^^S&jSiMs^^j^att the essential points."- C?*c,^T n $ a^ai Condens 'S in 'o a handy volume all BrT C !? E MISTRY. By Prof. VICTOR VON RICHTER, University of Breslau. Translated from Fourth German Edition by EDGAR F SMITH M.A., PH. D Professor of Chemistry, Wittenberg College, Iprinrfeld O 10 f g ' Pneld ^ ^^s V ^p^& n A ^ ele iIIUStoted etoto With Price of Each Book, Cloth, $3.00 ; Leather, $3.50. P. BLAKISTON. SON I^T^iishers and Booksellers, 1012 WALNUT STREET, PHILADELPHIA. MEDICAL BRIEFS. A series of short, concise compends for the medical student and practitionei I2mo. Cloth. Each, Price, $1.00. No. I. POST-MORTEM EXAMINATIONS. Second Edition With Especial Reference to Medico-Legal Practice. By Prof. RUDOLPJ VlRCHOW, of Berlin Charite Hospital, author of Cellular Pathology ; Trans lated by T. P. SMITH, M.D., Member of the Royal College of Surgeons c England. Second American, from the Fourth German Edition. Wit Four Lithographic Plates. " We are informed in precise and exact terms how a post-mortem examination should t made, both with regard to the plan to be pursued, and the manner of making the several cu into the various organs and tissues. The method of recording the results of the investigation . clearly indicated by the addition of the detailed account of the examination of four cases and the value of the objective evidence is accurately stated in the form of the inference drawn concerning the manner and cause of death." -American Journal of Medical Science " For thorough and systematic method in the performance of post-mortem examination there is no guide like it." London Lancet. No. II. MANUAL OF VENEREAL DISEASES. Fourth Editior A Concise Description of those Affections and of their Treatment, includin a list of SIXTY- SEVEN PRESCRIPTIONS for Vapor Bath, Gargles, Injection Lotions, Mixtures, Ointments, Paste, Pills, Powders, Solutions and Suj positories. By BERKELEY HILL, M.D., Professor of Clinical Surgery, i University College; Surgeon to University College and Lock Hospitals and ARTHUR COOPER, M.D., formerly House Surgeon, Lock Hospita Fourth Edition, Revised and Enlarged. " I have examined it with care, and find it to be a practical and useful compendium < knowledge on the subjects discussed, well adapted to the use of medical students and tho; ' physicians in general practice who have occasional need to consult a work of this kind."- James Neven Hyde, M.D., Professor of Skin and Venereal Diseases, Rush Medical Colleg Chicago. " It seems to contain much information in a condensed form. The names of the autho ensure its doctrinal accuracy." Ed. L. Keyes, M.D., Professor of Genito- Urinary Surger^ Syphilology and Dermatology, Bellevue Hospital Medical College, N. Y. " As the work of one of the highest living authorities, it is natural that it should ha< found such favor." Gaillard's Medical Journal. " If you wish to be well informed on this subject, we say, secure this little book." Mea cal Brief. No. III. MEDICAL ELECTRICITY. A Compend of Electricil and its Medical and Surgical Uses. By CHAS. F. MASON, M.D., Assistai Surgeon, United States Army, with an Introduction by CHAS. H. MAY, M.r Instructor in Ophthalmology, New York Polyclinic. With Illustration Just Ready. From, the large amount of literature upon the subject of Medical Electricity, Dr. Mas( has selected and classified the facts and principles that are of practical use to the student ai physician. It is a short, comprehensive statement of this important branch of therapeuti in clear, plain language, with illustrations, where needed, to render the text distinct. OTHER VOLUMES IN PREPARATION. Price of Each Book, Bound in Cloth, $1.00. P. BLAKISTON, SON & CO., Publishers and Booksellers 1012 WALNUT STREET, PHILADELPHIA. HUMAN PHYSIOLOGY. FOURTH EDITION. ILLUSTRATED. BRUBAKER. THE 7QUIZ-COMPENDS? A NEW SERIES OF MANUALS FOR THE USE OF STUDENTS AND PHYSICIANS. Price of each, Cloth, $1.00. Interleaved, for taking Notes, $i 25. ftif These Compends are based on the most popular text books, and the lectures of prominent professors, and are kept constantly revised, so that they may thoroughly represent the present state of the subjects upon which they treat. &&=' The Authors have had large experience as Quiz Masters and attaches of col- leges, and are well acquainted with the wants of students. J&^They are arranged in the most approved form, thorough and concise, containing 231 illustrations, inserted wherever they could be used to advantage. Can be used by students of any college. They contain information nowhere eE>e collected in such a condensed, practical shape. 4If" Size is such that they may be easily carried in the pocket, and the price is low. 4S^ They will be found very serviceable to physicians as remembrancers. LIST OF VOLUI1ES. No. i. HUMAN ANATOMY. Fourth Revised and Enlarged Edition. Including Visceral Anatomy, formerly published separately. 117 Illustrations. By SAMUEL O. L. POTTER, M.D., Professor of the Practice of Medicine, Cooper Medical College, San Francisco, late A. A. Surgeon, U. S. Army. Revised and enlarged. Index. No. 2. PRACTICE OF MEDICINE. Part I. Second Edition. Revised and Enlarged. By DAN'L E. HUGHES, M.D., Demonstrator of Clinical Medicine, Jef- ferson College, Philadelphia. No. 3. PRACTICE OF MEDICINE. Part II. Second Edition. Revised and Enlarged. Same author as No. 2. No. 4. PHYSIOLOGY. Fourth Edition, with Illustrations and a table of Physiological Constants. Enlarged and Revised. By A. P. BRUBAKER, M.D., Professor of Phys- iology and General Pathology in the Pennsylvania College of Dental Surgery; Demonstrator of Physiology, Jefferson Medical College, Philadelphia. Index. No. 5. OBSTETRICS. Third Edition. Enlarged. By HENRY G. LANDIS, M.U., Professor of Obstetrics and Diseases of Women and Children, Starling Medical College, Columbus, Ohio. Illustrated. No. 6. MATERIA MEDICA, THERAPEUTICS, AND PRESCRIPTION WRITING. Fifth Revised Edition. Enlarged. By SAMUEL O. L. POTTER, M.D., Professor of Practice, Cooper Medical College, San Francisco ; late A. A. Surgeon U. S. Army. Index. No. 7. GYNAECOLOGY. A Compend of Diseases of Women. By HENRY MORRIS, M.D., Demonstrator of Obstetrics, Jefferson Medical College, Philadelphia. No. 8. DISEASES OF THE EYE, AND REFRACTION, including Treatment and Surgery. By L. WEBSTER Fox, M.D., Chief Clinical Assistant, Ophthalmo- logical Department, Jefferson Medical College Hospital, and GEO. M. GOULD, A.B. With 60 Illustrations. rio. o. SURGERY. Third Edition. Enlarged and Improved. By ORVILLE HOR- WITZ, B. s., M. D., Demonstrator of Anatomy, Jefferson College, Chief of the Out- Patient Surgical Department, Jefferson College Hospital, late Resident Physician Pennsylvania Hospital, Philadelphia. With many Formulae and 90 Illustrations Index. f . T O.SC. ORGANIC CHEMISTRY, including Medical Chemistry, Urine Analysis and the Analysis of Water and Food. By HENRY LEFFMANN, M.D., D D.S., Pro- fessor of Chemistry and Metallurgy in the Pennsylvania College of Dental Surgery; and of Clinical Chemistry and Hygiene in the Philadelphia Polyclinic, etc., Phila- delphia. revised. Others in preparation. Price, each, Cloth, $1.00. Interleaved, for taking Notes, $1.25. P. BLAKISTON, SON & CO., Medical Publishers and Booksellers. 1012 WALNUT STREET, PHILADELPHIA. ?QUIZ-COMPENDS. ? No. 4. > A COMPEND OF HUMAN PHYSIOLOGY. ESPECIALLY ADAPTED FOR THE USE OF MEDICAL STUDENTS. BY ALBERT P. BRUBAKER, A.M., M.D., DEMONSTRATOR OF PHYSIOLOGY IN THE JEFFERSON MEDICAL COLLEGE; PROFESSOR OF PHYSIOLOGY, PENNSYLVANIA COLLEGE OF DENTAL SURGERY; MEMBER OF THE PATHOLOGICAL SOCIETY OF PHILADELPHIA. FOURTH EDITION, REVISED AND ENLARGED. WITH ILL VSTRA TIONS AND A TABLE OF PHYSIOLOGICAL CONSTANTS. X PHILADELPHIA : P. BLAKISTON, SON & CO., 1012 WALNUT STREET. 1888. Entered according to Act of Congress, in the year 1888, by P. BLAKISTON, SON & CO., In the office of the Librarian of Congress, at Washington, D. C. PRESS OF WM. F. FELL & CO., 1220-24 Sansorn 3-trpet. * 888 PREFACE TO FOURTH EDITION. A fourth edition of the Compend of Physiology having been called for, the author -has taken the opportunity to revise many of the sections, to insert a few figures, and to add some ten pages of additional matter, which, it is hoped, will make the book more complete and increase its usefulness to the student. 1210 Race Street. A. P. BRUBAKER. PREFACE TO SECOND EDITION. This Compend of Physiology is the outgrowth of the author's system of examinations in the Quiz room during a number of years, and was written at the request of medical students who desired a compadt and convenient arrangement of the fundamental facts of human physiology. As most medical students enter upon the study of physiology before they have ac- quired a thorough knowledge of anatomy, it was thought desirable that such anatomical details should also be inserted as would be essential to a clear conception of the functions about to be studied. It was believed that it would be practically useful to students during their attendance upon lectures and in reviewing the subject prior to examinations. The fact that during the first year after its publication the first edition has been exhausted, proves that it has met the needs of students. In preparing a second edition the author has carefully revised the en- tire work, and inserted some fifteen pages of additional matter, which it is hoped will still further increase the usefulness of the book. To those teachers of physiology who have kindly noticed and recom- mended the Compend to their students I tender my thanks, and trust that in its improved condition it will continue to merit their approval. ALBERT P. BRUBAKER. 13513 TO MY FATHER, HENRY BRUBAKER, A.M., M.D., THIS LITTLE VOLUME IS AFFECTIONATELY INSCRIBED. TABLE OF CONTENTS. PAGE INTRODUCTION 9 CHEMICAL COMPOSITION OF THE BODY .'. 10 STRUCTURAL COMPOSITION OF THE BODY 15 FOOD 1 8 DIGESTION 23 ABSORPTION 36 BLOOD 4 1 CIRCULATION OF BLOOD 47 RESPIRATION 54 ANIMAL HEAT : 61 SECRETION 63 Mammary Glands 66 Vascular or Ductless Glands 68 EXCRETION , 69 Kidneys 70 Liver 76 Skin 79 NERVOUS SYSTEM 83 Spinal Nerves 85 Properties and Functions of Nerves 87 Cranial Nerves 91 Spinal Cord 106 M edulla Oblongata . . .*. 114 Pons Varolii 117 Crura Cerebri 118 Corpora Quadrigemina 118 Corpora Striata and Optic Thalami 119 Vlll TABLE OF CONTENTS. PAGE Cerebellum 121 Cerebrum 123 Sympathetic Nervous System 130 SENSE OF TOUCH , 133 SENSE OF TASTE 134 SENSE OF SMELL 136 SENSE OF SIGHT 137 SENSE OF HEARING 144 VOICE AND SPEECH 148 REPRODUCTION 151 Generative Organs of the Female 151 Generative Organs of the Male ; 154 Development of Accessory Structures 155 Development of the Embryo 160 TABLE OF PHYSIOLOGICAL CONSTANTS 166 TABLE SHOWING RELATION OF WEIGHTS AND MEASURES OF THE METRIC SYSTEM TO APPROXIMATE WEIGHTS AND MEASURES OF THE U. S 169 INDEX 170 COMPEND OF HUMAN PHYSIOLOGY. Physiology, from fyvci-, nature, and Attyof , a discourse, in its original application embraced the study of all natural objects, inorganic as well as organic. In its modern application physiology signifies tJie study of life ; the investigation of the vital phenomena exhibited by all organic bodies, vegetable and animal. It may be divided into 1. Vegetable physiology, which treats of the phenomena manifested by the several structures of which the plant is composed. 2. Animal physiology ', which treats of the phenomena manifested by the organs and tissues of which the animal body is composed. Human Physiology is the study of the functions exhibited by the human body in a state of health. PL function is the action of an organ or tissue. The Functions of the Human Body may be classified into three groups, viz.: 1. Nutritive functions, which have for their object the preservation of the individual ; e. g., digestion, absorption, circulation of the blood, respiration, assimilation, animal heat, secretion and excretion. 2. Animal functions, which bring the individual into conscious relation- ship with external nature; e. g., sensation, motion, language, mental and moral manifestations. 3. Reproductive function, which has for its object the preservation of the species. The facts of human physiology have been determined by means of anatomy, chemistry, pathology, comparative anatomy, vivisection, the application of physics, etc. The body may be studied from a chemical and structural point of view. B 9 10 HUMAN PHYSIOLOGY. CHEMICAL COMPOSITION OF THE HUMAN BODY. Of the Sixty-four Chemical Elements, about sixteen enter into the composition of the body, in the following proportions : Oxygen 72.00 "] O. H. and C. are found in all the tissues and Hydrogen 9.10 fluids of the body, without exception. Nitrogen 2.50 f O. H. C. and N. found in most of the fluids Carbon I 3-5 J and all tissues except fat. Sulphur 147 In fibrin, casein, albumen, gelatin; as potas- sium- sulpho- cyanide in saliva; as alkaline sulphate in urine and sweat. Phosphorus... 1.15 In fibrin and albumen ; in brain; as tri -sodium phosphate in blood and saliva, etc. Calcium 1.30 As calcium phosphate in lymph, chyle, blood, saliva, bones and teeth. Sodium 10 As sodium chloride in all fluids and solids of the body, except enamel; as sodium sulphate and phosphate in blood and muscles. Potassium, 026 As potassium chloride in muscles; generally found with sodium as sulphates and phos- phates. Magnesium ooi Generally in association with calcium, as phos- phate, in bones. Chlorine 085 In combination with sodium, potassium and other bases, in all the fluids and solids. fluorine 08 As calcium fluoride in bones, teeth and urine. Iron 01 In blood globules ; as peroxide in muscles. Silicon a trace In blood, bones and hair. Manganesium a trace Probably in hair, bones and nails. Of the four chief elements which together make up 97 per cent, of the body, O. H. N. are eminently mobile, elastic, and possess great atomic heat. C. H. N. are distinguished for the narrow range and feebleness of their affinities and chemical inertia. C. has the greatest atomic cohesion. O. is noted for the number and intensity of its combinations, and its remark- able display of chemical activity. Chemical elements do not exist alone in the body, but are combined in characteristic proportions to form compounds, the proximate principles, which are the ultimate compounds to which the fluids and solids can be reduced. Proximate Principles exist in the body under their own form, and can be extracted without losing their distinctive properties. There are about one hundred proximate principles, which are divided into four classes, viz. : inorganic, organic non-nitrogenized, organic nitro- genized, and principles of waste. CHEMICAL COMPOSITION OF THE HUMAN BODY. 1 I. INORGANIC PROXIMATE PRINCIPLES. SUBSTANCE. WHERE FOUND. Oxygen ........................... Lungs and blood. Hydrogen ........................ Stomach and intestines. Nitrogen ....................... ,. Blood and intestines. Carbonic anhydride ............ Expired air of lungs. Carburetted hydrogen ) T , . . , . OIL. LI. j i. j ? ... Lungs and intestines. Sulphuretted hydrogen / Water ............................ Found in all solids and fluids. Sodium chloride ............... In all fluids and solids except enamel. Potassium chloride ............ In muscles, liver, saliva, gastric juice, etc. Ammonium chloride .......... Gastric juice, saliva, tears, urine. Calcium chloride ............... Bones, teeth, urine. Calcium carbonate ............. Bones, teeth, cartilage, internal ear, blood. Calcium phosphate " - I" -1 ** * -lids of the body. Potassium phosphate } Sodium sulphate ) TT . , Potassium sulphate. j "' Universal, except milk, bile and gastric juice. Sodium carbonate \ ^, Potassium carbonate } - Blood ' bones > ^P^ urlne ' etc ' Magnesium carbonate ........ Blood and sebaceous matter. The inorganic principles enter and leave the body under their own form. Water is an essential constituent of all the tissues of the body, constituting about 70 per cent, of the entire body weight. It is introduced into the body in the form of drink and as a constituent of all kinds of food. The average quantity consumed daily is about four pints. While in the body, water acts as a general solvent, gives pliability to various tissues, and promotes the passage of inorganic and organic matters through animal membranes. It also promotes chemical changes which are essen- tial to absorption and assimilation of food and the elimination of products of waste. It is probable that water is also formed within the body by the union of oxygen with the surplus hydrogen of the food. It is eliminated by the skin, lungs and kidneys. Sodium chloride is present in all the solids and fluids of the body, with the exception of enamel. It regulates osmotic action, holds the albuminous principles of the blood in solution, and preserves the form and consistence of blood corpuscles and the cellular elements of the tissues, by regulating the amount of water entering into their composition. Calcium phosphate is the most abundant of all the inorganic principles with the exception of water, and is present to a great extent in bone, teeth, muscles and milk. It gives the requisite consistency and solidity to the 12 HHMAN PHYSIOLOGY. different tissues and organs. In the blood, it is held in solution by the albuminous constituents. The Sodium and Potassium phosphates are present in most of the solids and fluids, and give to them their alkaline reaction. They are chiefly derived from the food. II. ORGANIC NON-NITROGENIZED PRINCIPLES. The organic non-nitrogenized principles are derived mainly from the vegetable world, but are also produced within the animal body. They are divided into : 1st, the carbo-hydrates, comprising starch and sugar, bodies in which the oxygen and hydrogen exist in the proportion to form water, the amount of carbon being variable ; 2d, the hydro- carbons, comprising fats, bodies having the same elements entering into their composition, but with the carbon and hydrogen increased and the oxygen diminished in amount. SUGARS. C. O. H. Glycogen, or Liver sugar. Lactose, or Milk sugar. Glucose, or Grape sugar. Inosite, or Muscle sugar. Sugar is found in many of the tissues and fluids of the body; e.g., liver, milk, placenta, blood, muscles, etc. The varieties of sugar are soluble in water, assume the crystalline form upon evaporation, and are converted into alcohol and carbonic acid by fermentation. Sugar is derived from the food, converted, in the alimentary canal, into glucose, absorbed by the veins of the portal system, and then stored up in the liver, under the form of glycogen. When the system requires sugar, it is again returned to the cir- culation, and plays its part in the nutritive processes of the body. It is finally oxidized, and thus contributes to the formation of heat. It is finally eliminated under the form of carbonic acid and water. There is no experimental proof that sugar contributes directly to the formation of fat in the animal body. FATS. c. o. H. Palmitin, ") Palmitic acid, ~\ Stearin, > Neutral Fats. Stearic acid, > Fatty Acids. Olein, J Oleic acid, ) The Neutral fats, when combined in proper proportions, constitute a large part of the fatty tissue of the body ; they are soluble in ether, chloro- form and hot alcohol ; insoluble in cold alcohol and water, and liquefy at a high temperature ; when a neutral fat is subjected to a high temperature CHEMICAL COMPOSITION OF THE HUMAN BODY. 13 in the presence of water and an alkali, it is decomposed, with the assimi- lation of the elements of water, into a fatty acid and glycerine. The fatty acid combines with the alkali and forms an oleate, palmitate or stearate, according to the fat used. A similar decomposition of the neutral fats is said to take place in the small intestine during digestion. When thoroughly mixed with pancreatic juice, the fats are reduced to a condition of emulsion, a state in which the fat is minutely subdivided and the small globules held in suspension. The Fatty acids combined with sodium, potassium' ami calcium, are found as salts in various fluids of the body, such as blo6d, chyle, faeces, etc. Phosphorized fats in nervous tissue, butyric acid in milk, propionic acid in sweat, are also constituents of the body. The Fats are derived from the food, both animal and vegetable. They are deposited in the form of small globules in the cells of the different tissues, are suspended in various fluids, are deposited in masses in and around various anatomical structures and beneath the skin. Independent of the fat consumed as food, there is good experimental evidence that fat is also produced within the animal body from a partial decomposition of the albuminous compounds. Fat serves as a non-conductor of heat, gives roundness and form to the body, and protects various structures from injury. The fats are ultimately oxidized, thus giving rise to heat and force, and are finally eliminated as carbonic acid and water. III. ORGANIC NITROGENIZED PRINCIPLES. ALBUMENS. C. O. H. N. S. P. Albumen. Myosin. Mucin. Albuminose. Protagon. Chondrin. Fibrin. Pepsin. Elastin. Casein. Pancreatin. Keratin. Ostein. Salivin. Globulin. The Albuminous compounds are organic in their origin, being derived from the animal and vegetable world; they are taken into the body as food, appropriated by the tissues, and constitute their organic basis ; they differ from the non-nitrogenized substances in not being crystalline, but amorphous, in having a more complex but just as definite composition, and containing in addition to C. O. H., nitrogen, with, at times, sulphur and phosphorus. The albumens possess characteristics which distinguish them from all other substances : viz., a molecular mobility, which permits isomeric modifications to take place with great facility; a catalytic influence, in virtue of which they promote, under favorable conditions, chemical changes in other substances: e.g., during digestion, salivin and pepsin 14 HUMAN PHYSIOLOGY. cause starch an ! albumen to be transformed into sugar and albuminose respectively. Different albumens possess varying proportions of water, which they lose when subjected to desiccation, becoming solid ; but upon exposure to moisture they again absorb water, regaining their original con- dition they are hygroscopic. Another property is that of coagulation, which takes place under certain conditions: e.g., the presence of mineral acids, heat, alcohol, etc. After death the albuminous compounds undergo putrefactive changes, giving rise to -carburetted and sulphuretted hydrogen and other gases. Albumen exists in the blood, lymph, chyle, constituting the pabulum of the tissues; it is coagulated by heat, mineral acids and alcohol. Peptones are found in the stomach from the digestion of albuminous principles of the food ; they are coagulated by tannic acid, chlorine, acetate of lead, and characterized by great diffusibility, which permits them to pass through animal membranes with facility. Fibrin can be obtained from freshly drawn blood by whipping ; it also coagulates spontaneously, and when examined microscopically exhibits a lilamentous structure. Casein is the albuminous principle of milk. Ostein constitutes the organic basis of bone, with which are mingled the salts of lime. Myosin is found in muscles, protagon in brain, pepsin, pancreatin and salivin, in the digestive fluids. Mucin, chondrin, elastin, keratin and globulin, are found in mucus, cartilage, elastic tissues, hair, nails, and red corpuscles, respectively. As the properties of the compounds formed by the union of elements are the resultants of the properties of the elements themselves, it follows that the ternary substances, sugais, starches and fats, possess a great inertia and a notable instability; while in the more complex albuminous compounds, in which sulphur and phosphorus are united to the four chief elements, molecular mobility, resulting in isomerism, exists in a high degree. As these compounds are unstable, of a great molecular mobility, they are well fitted to take part in the composition of organic bodies, in which there is a continual movement of composition and decomposition. IV. PRINCIPLES OF WASTE. Urea, Xanthin, Sodium, 1 Creatin, Tyrosin, Potassium, | Creatinin, Hippuric Acid, Ammonium, Cholesterin, Calcium Oxalate, Calcium, STRUCTURAL COMPOSITION OF THE BODY. 15 These principles, which represent waste, are of organic origin, arising within the body as products of disassimilation or retrograde metamorphosis of the tissues; they are absorbed by the blood, carried to the various excretory organs, and by them eliminated from the body. The excrementitious substances will be fully considered under excretion. Proximate Quantity of the Chemical Elements and Proximate Principles of the Body, Weighing 154 Ibs. Ibs. oz. Ibs. oz. Oxygen in ... Water in ... Hydrogen 14 ... Albuminoids 23 7 Nitrogen 3 8 Fats 12 ... Carbon 21 ... Calcium phosphate 5 13 Calcium 2 .*.. Calcium carbonate I Phosphorus I 12 Calcium fluoride 3 Sodium, etc 12 Sodium sulphate, etc 9 154 ... 154 ... STRUCTURAL COMPOSITION of THE BODY. The Study of the Structure of the body reveals that it is composed of dissimilar parts, e. g., bones, muscles, nerves, lungs, etc.; while these, again, by closer examination, can be resolved into elementary structures, the tissues, e.g., connective tissue, muscular, nervous, epithelial tissue, etc. Microscopical examination of the tissue shows that they are com- posed of fundamental structural elements, termed cells. Cells are living physiological units ; the simplest structural forms capable of manifesting the phenomena of life. Cells vary in their anatomical constitution in the different structures ot the body, and may be classed in three groups, viz.: i. Cells possessing a distinct cell wall, cell substance and a nucleus. 2. Cells possessing a cell substance and a nucleus. 3. Cells possessing the cell substance only. They vary in size, from the jfoy to the J- 7 of an inch in diameter ; when young and free to move in a fluid medium they assume the spherical form; but when subjected to pressure, may become flattened, cylindrical, fusiform or stellate. Structure of Cells. The cell wall is not an essential structure, as many cells are entirely devoid of it. It is a thin, structureless, transparent membrane, permeable to fluids. The Cell Substance in young cells is a soft, viscid, albuminous matter, 16 HUMAN PHYSIOLOGY. unstable, insoluble in water, and known as protoplasm, bioplasm, sarcode, etc.; in older cells the original cell substance undergoes various trans- formations, and is partly replaced by fat globules, pigment and crystals. The Nucleus is a small vesicular body in the interior of the cell sub- stance, and frequently contains smaller bodies, the nucleoli. MANIFESTATIONS OF CELL LIFE. Growth. Cells when newly formed are exceedingly small, but as they approach maturity they increase in size, by the capability which the cells possess of selecting and appropriating new material as food, vitalizing and organizing it. The extent of cell growth varies in different tissues ; in some the cells remain exceedingly small, in others they attain considerable size. In many instances the cell substance undergoes transformation into new compounds destined for some ulterior purpose. Reproduction. Like all organic structures cells have a limited period of life; their continual decay and death necessitates a capability of repro- duction. Cells reproduce themselves in the higher animals mainly by fission. This is seen in the white blood corpuscles of the young embryos of animals ; the corpuscle here consists of a cell substance and nucleus. When division of the cell is about to take place, the nucleus elongates, the cell substance assumes the oval form, a constriction occurs, which gradually deepens, until the original cell is completely divided and two new cells are formed, each of which soon grows to the size of the parent cell. In cells provided with a cell membrane the process is somewhat different. In the ova of the inferior animals, after fertilization has taken place, a furrow appears on the opposite sides of the cell substance, which deepens until the cell is divided into two equal halves, each containing a nucleus; this process is again repeated until there are four cells, then eight, and so on until the entire cell substance is divided into a mulberry mass of cells, completely occupying the interior of the cell membrane. The whole pro- cess of segmentation takes place with great rapidity, occupying not more than a few minutes, in all probability. Motion. Spontaneous movement has been observed in many of the cells of the body. It may be studied, for example, in the movements of the spermatozoids, the waving of the cilia covering the cells of the bron- chial mucous membrane, the white corpuscles of the blood, etc. By a combination and transformation of these original structural elements, and material derived from them, all the tissues are formed which enter into the structure of the human body. STRUCTURAL COMPOSITION OF THE BODY. 17 CLASSIFICATION OF TISSUES. I. Homogeneous Substance, a more or less solid, albuminous struc- ture, filling the spaces between the cells and fibres of various tissues, e. g. t cartilage, bone, dentine, etc. II. Limiting Membrane, a thin, homogeneous membrane, structureless, composed of coagulated albumen, and often not more than the 2 wo^ f an inch in thickness, found lining the blood vessels and lymphatics, forming the basement membrane of the skin and mucous membranes, the posterior layer of the cornea, the capsule of the crystalline lens, etc. III. Simple fibrous or filamentous tissue the elements of which are real or apparent filaments. (a) Connective or areolar ; white fibrous tissue ; constituting tendons, ligaments, aponeuroses, periosteum, dura mater, synovial membranes, vascular tunics, etc. (b) Yellow elastic tissue, found in the middle coats of arteries, veins, lymphatics, ligamentum nuchse, vocal cords, ligamenta subflava, etc. IV. Compound membranes (membrano- cellular or fibro- cellular tissues), cells aggregated into laminae. (a) Epidermic tissue ; (b) epithelial tissue; (c) glandular tissue ; (d) cornea. V. Cells containing coloring matter, or pigment cells, e. g., skin, choroid membrane, etc. VI. Cells coalesced or consolidated by internal deposits, e. g., hair, nails, bone, teeth, etc. VII. Cells imbedded in an intercellular substance, e. g., cartilage, crystalline lens, etc. VIII. Cells aggregated in clusters, forming tissues more or less solid, e.g., adipose tissue, lymphatic glands. IX. Cells imbedded in a matrix of capillaries, e. g., gray or vesicular nervous matter. X. Cells whose coalesced cavities form tubes containing liquids or secondary solid deposits, e. g., vascular tissue, dentine. XI. Cells free, isolated, or floating fluid tissue e.g., red and white blood corpuscles, lymph and chyle corpuscles. 18 HUMAN PHYSIOLOGY. FOOD. A Food may be defined to be any substance capable of playing a part in the nutrition of the body. Food is required for the repair of the waste of the tissues consequent on their functional activity, for the generation of heat and the evolution of force. Hunger and Thirst are sensations which indicate the necessity for taking food ; they arise in the tissues at large, and are referred to the stomach and fauces, respectively, through the sympathetic nervous system. Inanition or Starvation results from an insufficiency or absence of food, the physiological effects of which are hunger, intense thirst, intestinal uneasiness, weakness and emaciation ; the quantity of carbonic acid ex- haled diminishes and the urine is lessened in amount ; the volume of the blood diminishes; a fetid odor is exhaled from the body; vertigo, stupor followed by delirium, and at times convulsions, result from a disturbance of the nerve centres; a marked fall of the bodily temperature occurs, from a diminished activity of the nutritive process. Death usually takes place, from exhaustion. During starvation the loss of different tissues, before death occurs, aver- ages T %, or 40 per cent, of their weight. Those tissues which lose more than 40 per cent, are fat, 93.3 ; blood, 75 ; spleen, 71.4; pancreas, 64.1; liver. 52; heart, 44.8; intestines, 42.4; muscles, 42.3. Those which lose less than 40 per cent, are the muscular coat of the stomach, 39.7 ; pharynx and oesophagus, 34.2 ; skin, 33.3 ; kidneys, 31.9; respiratory apparatus, 22.2; bones, 16.7; eyes, 10; nervous system, 1.9. The Fat entirely disappears, with the exception of a small quantity which remains in the posterior portion of the orbits and around the kid- neys. The Blood diminishes in volume and loses its nutritive properties. The Muscles undergo a marked diminution in volume and become soft and flabby. The Nervous system is last to suffer, not more than two per cent, disappearing before death occurs. The appearances presented by the body after death from starvation are those of anaemia and great emaciation ; almost total absence of fat ; blood- lessness ; a diminution in the volume of the organs; an empty condition of the stomach and bowels, the coats of which are thin and transparent. There is a marked disposition of the body to undergo decomposition, giving rise to a very fetid odor. The duration of life after a complete deprivation of food varies from eight to thirteen days, though life can be maintained much longer if a FOOD. 19 quantity of water be obtained. The water is more essential under these circumstances than the solid matters, which can be supplied by the organism itself. The food consumed daily is a heterogeneous compound consisting of both nutritious and innutritious portions. The nutritious portions are known as the alimentary principles, while the food, as a whole, is known as aliment. The different alimentary principles which are appropriated by the system are combined dn different proportions in the various articles of food, and are separated from the innutritious substances during the process of digestion. They belong to the organic and inorganic worlds, and may be classified, according to their chemical composition, as follows : CLASSIFICATION OF ALIMENTARY PRINCIPLES. 1. Albuminous group nitrogenized, C. O. H. N. S. P. PRINCIPLE. WHERE FOUND. Myosin, syntonin Flesh of animals. Vitellin, albumen Yolk of egg, white of egg. Fibrin, globulin Blood contained in meat. Casein Milk, cheese. Gluten Grain of wheat and other cereals. Vegetable albumen Soft growing vegetables. Legumin Peas, beans, lentils, etc. Gelatin Bones. 2. Saccharine group non-nitrogenized, C. O. H. Cane sugar, beet root sugar Sugar cane, beets, etc. Glucose, grape sugar Fruits. Inosite, liver sugar, glycogen M uscles, liver, etc . Lactose or milk sugar , Milk. Starch Cereals, tuberous roots and leguminous plants. 3. Oleaginous group non-nitrogenized, C. O. H. Animal fats and oils ~\ Found in the adipose tissue of animals, Stearin, olein >- seeds, grains, nuts, fruits, and other Palmatin, fatty acids J vegetable tissues. 4. Inorganic group. Water, sodium and potassium chlorides, sodium, calcium, magnesium and potassium phosphates, calcium carbonate and iron. 5. Vegetable acid group. Malic, citric, tartaric and other acids, found principally in fruits. 6. Accessory foods. Tea, coffee, alcohol, cocoa, etc. The Albuminous principles enter largely into the composition of the body, and constitute the organic bases of the different tissues; they are 20 HUMAN PHYSIOLOGY. mainly required for the growth and repair of the tissues. There is good reason to believe that the albuminous principles are decomposed in the body into fat and urea, and the former when oxidized gives rise to the evolution of heat and force, while the latter is eliminated by the kidneys. Muscular work, however, does not result from a destruction of the albu- minous compounds. The oxidation of the carbonaceous compounds, sugars and oils, furnishing the force which is transformed by the muscular system into motor power. When employed exclusively as food for any length of time, the albuminous substances are incapable of supporting life. The Saccharine principles are important to the process of nutrition, but the changes which they undergo are not fully understood ; they form but a small proportion of the animal tissues, and by oxidation generate heat and force. Starch undergoes conversion into dextrin and grape sugar. The Oleaginous principles form a large part of the tissues of the body. They are introduced into the system as food, and are formed also from a transformation of albuminous matter during the nutritive process; they enter into the composition of nervous and muscular tissue, and are stored up as adipose tissue in the visceral cavities and subcutaneous connective tissue, thus giving roundness to the form and preventing, to some extent, the radiation of heat. While they aid in the reconstruction of tissue, they mainly undergo oxidation, giving rise to the production of heat and the evolution of muscular and nervous force. The Inorganic principles constitute an essential part of all animal tissues, and are introduced with the food. Water is present in all fluids and solids of the body, holding their ingredients in solution, promoting the absorption of new material into the blood and tissues, and the removal of waste ingredients. Sodium chloride is an essential constituent of all tissues, regulating the passage of fluids through animal membranes (endosmosis and exosmosis). Calcium phosphate gives solidity to bones and teeth, constituting more than one-half their substance. Iron is a constituent of the coloring matter of the blood. The Vegetable acids are important to nutrition, and tend to prevent the scorbutic diathesis. The Accessory foods also influence the process of nutrition. Tea excites the respiratory function, increasing the elimination of carbonic acid. Coffee is a stimulant to the nervous system ; increases the force of the heart's action, increases the arterial tension and retards waste. Alcohol, when introduced into the system in small quantities, undergoes FOOD. 21 oxidation and contributes to the production of force, and is thus far a food. It excites the gastric glands to increased secretion, improves the digestion, accelerates the action of the heart and stimulates the activities of the nervous centres. In zymotic diseases, and all cases of depression of the vital powers, it is most useful as a restorative agent. When taken in excessive quantities, it is eliminated by the lungs and kidneys. The metamorphosis of the tissues is retarded, the elimination of urea and carbonic acid is lessened, the temperature lowered, the muscular powers impaired and the resistance to depressing external influences diminished. When taken through a long period of time, alcohol impairs digestion, produces gastric catarrh, disorders the secreting power of the hepatic cells. It also diminishes the muscular power and destroys the structure and composition of the cells of the brain and spinal cord. The connective tissue of the body increases in amount, and subsequently contracting, gives rise to sclerosis. A proper combination of different alimentary principles is essential for healthy nutrition ; no one class being capable of maintaining life for any definite length of time. The Albuminous food in excess promotes the arthritic diathesis, mani- festing itself as gout, gravel, etc. The Oleaginous food in excess gives rise to the bilious diathesis, while a deficiency of it promotes the scrofulous. The Farinaceous food, when long continued in excess, favors the rheu- matic diathesis by the development of lactic acid. The Alimentary Principles are not introduced into the body as such, but are combined in proper proportions to form compound substances, termed foods, e.g., bread, milk, eggs, meat, etc., the nutritive value of each depending upon the extent to which these principles exist. PERCENTAGE COMPOSITION OF DIFFERENT FOODS. WATER. ALBUMEN. STARCH. SUGAR. FATS. SALTS. Bread 37 8.1 47.4 3.6 1.6 2.3 Milk..... 86 4.1 ... 5.2 3.9 0.8 Eggs 74 14.0 ... ... 10.5 1.5 Mea t 54 27.6 ... ... 15.45 2.95 Potatoes 75 2.1 18.8 3.2 0.2 0.7 Corn 14 ii. i 64.7 0.4 8.1 1.7 Oatmeal 15 12.6 58.4 5.4 5.6 3 Turnips 91 1.2 5.1 2.1 ... 6 Carrots 83 1.3 8.4 6.1 0.2 i.o Rice 13 6.3 79.1 0.4 0.7 0.5 X 22 HUMAN PHYSIOLOGY. The amount of food required in 24 hours is estimated from the total quantity of carbon and nitrogen excreted from the body in 24 hours ; these two elements representing the waste or destruction of the carbonaceous and nitrogenized compounds. It has been determined by experimentation that about 4600 grains of carbon and about 300 grains of nitrogen are eliminated from the body daily; the ratio being about 15 to I. That the body may be kept in its normal condition, a proper proportion of carbon- aceous (bread) to nitrogenized (meat) food should be observed in the diet. The method of determining the proper amounts of both kinds of food is as follows : 1000 grains of bread (2 oz.) contain 300 grs. C. and 10 grs. N. To obtain the requisite amount of nitrogen from bread, 30,000 grains, or about 4 Ibs., containing 9000 grains of carbon and 300 of nitrogen, would have to be consumed. Under such a diet there would be a large excess of carbon, which would be undesirable. On a meat diet the reverse obtains : looo grains of meat (2 oz.) contain 100 grs. C. and 30 grs. N. To obtain the requisite amounts of carbon from meat, 45,000 grains, or about 6^ Ibs. , containing 4500 grains of carbon and 1350 grains of nitro- gen, would have to be consumed. Under such circumstances there would arise an excess of nitrogen in the system, which would be equally undesir- able and injurious. By combining these two articles, however, in proper proportion, the requisite amounts of carbon and nitrogen can be obtained without any excess of either, e. g. : * 2 Ibs. of bread contain 4630 grs. C. and 154 grs. N. ^f " meat " 463 " " " 154 " " 5093 C. 308 N. The amount of carbon and nitrogen necessary to compensate for the loss to the system daily would be contained in the above amounts of food. As about 3^ oz. of oil or butter are consumed daily, the quantity of bread can be reduced to 19 oz. In the quantities of bread and meat above men- tioned, there are 4.2 oz. albumen, 9.3 oz. sugar and starch. DIGESTION. 23 COMPARISON OF INGESTA AND EGESTA IN 24 HOURS. FOOD, DRINK, AIR. OZ. EXCRETIONS. OZ. - ..... 43.40 Water (6 pints) 93-OO Urine 66.31 Oxygen 26.24 Solid excreta 6.07 Total 13940 Total 13940 DIGESTION. Digestion is a physical and chemical process, by which the food intro- duced into the alimentary canal is liquefied and its nutritive principles transformed by the digestive fluids into new substances capable of being absorbed into the blood. The Digestive Apparatus consists of the alimentary canal and its appendages, viz. : teeth, salivary, gastric and intestinal glands, liver and pancreas. Digestion may be divided into seven stages : prehension, mastication, insalivation, deglutition, gastric and intestinal digestion and defecation. Prehension, the act of conveying food into the mouth, is accomplished by the hands, lips and teeth. Mastication is the trituration of the food, and is accomplished by the teeth and lower jaw, under the influence of muscular contraction. When thoroughly divided, the food presents a greater surface for the solvent action of the digestive fluids, thus aiding the general process of digestion. The Teeth are thirty-two in number, sixteen in each jaw, and divided into four incisors or cutting teeth, two canines, four bicuspids, and six molars or grinding teeth; each tooth consists of a crown covered by enamel, a neck, and a root surrounded by the crusta petrosa, and imbedded in the alveolar process ; a section through a tooth shows that its substance is made of dentine, in the centre of which is the pulp cavity, containing blood vessels and nerves. The lower jaw is capable of making a downward and an upward, a lateral and an antero-posterior movement, dependent upon the construction of the temporo-maxillary articulation. The jaw is depressed by the contraction of the digastric, genio-hyoia, mylo-hyoid and platysma myoides muscles; elevated by the temporal, 24 HUMAN PHYSIOLOGY. masseter and internal pterygoid muscles; moved laterally by the alternate contraction of the external pterygoid muscles ; moved anteriorly by the pterygoid and posteriorly by the united actions of the genio-hyoid, mylo- hyoid and posterior fibres of the temporal muscle. The food is kept between the teeth by the intrinsic and extrinsic mus- cles of the tongue from within, and the orbicularis oris and buccinator muscles from without. The Movements of Mastication, though originating in an effort of the will and under its control, are, for the most part, of an automatic or reflex character, taking place through the medulla oblongata and induced by the presence of food within the mouth. The nerves and nerve centres involved in this mechanism are shown in the following table : NERVOUS CIRCLE OF MASTICATION. AFFERENT OR EXCITOR NERVES. EFFERENT OR MOTOR NEKVES. 1. Lingual branch of 5th pair. I. 3d branch of 5th pair. 2. Glosso-pharyngeal. 2. Hypo-glossal. 3. Facial. The impressions made upon the terminal filaments of the sensory nerves are transmitted to the medulla ; motor impulses are here generated which are transmitted through motor nerves to the muscles involved in the move- ments of the lower jaw. The medulla not only generates motor impulses, but coordinates them in such a manner that the movements of mastication may be directed toward the accomplishment of a definite purpose. Insalivation is the incorporation of the food with the saliva secreted by fat parotid^ sub-maxillary and sub-lingual glands ; \\\t parotid saliva, thin and watery, is poured into the mouth through Steno's duct ; the sub- maxillary and sub-lingual salivas, thick and viscid, are poured into the mouth through Wharton's and Bartholini's ducts. In their minute structure the salivary glands resemble each other. They belong to the racemose variety, and consist of small sacs or vesicles, which are the terminal expansions of the smallest salivary ducts. Each vesicle or acinus consists of a basement membrane surrounded by blood vessels and lined with epithelial cells. In the parotid gland the lining cells are granular and nucleated ; in the sub-maxillary and sub-lingual glands the cells are large, clear, and contain a quantity of mucigen. During and after secretion very remarkable changes take place in the cells lining the acini, which are in some way connected with the essential constituents of the salivary fluids. In a living serous gland, e. g. y parotid, during rest, the secretory cells DIGESTION. 25 lining the acini of the gland are seen to be filled with fine granules, which are often so abundant as to obscure the nucleus and enlarge the cells until the lumen of the acinus is almost obliterated (Fig. i). When the gland begins to secrete the saliva, the granules disappear from the outer boundary FIG. i. Cells of the alveoli of a serous or watery salivary gland. A. After rest. B. After a short period of activity. C. After prolonged period of activity. From Yeo's Text- Book of Physiology. of the cells, which then become clear and distinct. At the end of the secretory activity, the cells have become free of granules, have become smaller and more distinct in outline. It would seem that the granular FIG. 2. Section of a u mucous " gland. A. In a state of rest. B. After it has been for some time actively secreting. After Lavdoiusky. matter is formed in the cells during the rest, and discharged into the ducts during the activity of the gland. In the mucous glands, e. g., sub-maxillary and sub-lingual, the changes that occur in the cells are somewhat different (Fig. 2). During the inter- 26 HUMAN PHYSIOLOGY. vals of digestion, the cells lining the gland are large, clear and highly refractive, and contain a large quantity of mucigen. After secretion has taken place, the cells exhibit a marked change. The mucigen cells have disappeared, and in their place are cells which are small, dark and com- posed of protoplasm. It would appear that the cells, during rest, elaborate the mucigen which is discharged into the tubules during secretory activity, to become part of the secretion. Saliva is an opalescent, slightly viscid, alkaline fluid, having a specific gravity of 1.005. Microscopical examination reveals the presence of salivary corpuscles and epithelial cells. Chemically it is composed ol \/ water, proteid matter, a ferment (ptyalin) and inorganic salts. The amount secreted in 24 hours is about 2.% Ibs. Its function is twofold : 1. Physical. Softens and moistens the food, glues it together, and facilitates swallowing. 2. Chemical. Converts starch into grape sugar. This action is due to the presence of the organic ferment, ptyalin. The change consists in the assumption of a molecule of water. Starch. Water. Grape Sugar. C 6 H 10 5 + H a O = C 6 H la 6 . NERVOUS CIRCLE OF INSALIVATION. AFFERENT OR EXCITOR NERVES. EFFERENT OR MOTOR NERVES. 1. Lingual branch of 5th pair. I. Auriculo-temporal branch of 5th 2. Glosso-pharyngeal. pair, for parotid gland. 2. Chorda tympani, for sub- maxil- lary and sub-lingual glands. The centres regulating the secretion are two, viz. : The medulla oblon- gata and the sub-maxillary ganglion of the sympathetic ; the latter acting antagonistically to the former. Impressions excited by the food in the mouth reach the medulla oblongata through the afferent nerves ; motor im- pulses are there generated which pass outward through the efferent nerves. Stimulation of the auriculo-temporal branch increases the flow of saliva from the parotid gland ; division arrests it. Stimulation of the chorda tympani is followed by a dilation of the blood vessels of the sub-maxillary gland, increased flow of blood (thus acting as a vaso-dilator nerve) and an abundant discharge of a thin saliva; division of the nerve arrests the secretion. Stimulation of the cervical sympathetic is followed by a contraction of the blood vessels, diminishing the flow of blood (thus acting as a vaso-con- strictor nerve) and a diminution of the secretion, which now becomes thick DIGESTION. 27 and viscid ; division of the sympathetic does not, however, completely dilate the vessels. There is evidence of the existence of a local vaso- motor mechanism, which is inhibited by the chorda tympani ; exalted by the sympathetic. Deglutition is the act of transferring food from the mouth into the stomach, and may be divided into three stages : 1. The passage of the bolus from the mouth into the pharynx. 2. From the pharynx into the oesophagus. 3. From the oesophagus into the stomach. In the ist stage, which is entirely voluntary, the mouth is closed and respiration momentarily suspended; the tongue, placed against the roof of the mouth, arches upward and backward, and forces the bolus into the fauces. In the sd stage, which is entirely reflex, the palate is made tense and directed upward and backward by the levatores-palati and tensores-palati muscles ; the bolus is grasped by the superior constrictor muscle of the pharynx and rapidly forced into the oesophagus. The food is prevented from entering the posterior nares by the uvula and the closure of the posterior half-arches (the palato-pharyngei muscles); from entering the larynx by its ascent under the base of the tongue and the action of the epiglottis. In the $d stage, the longitudinal and circular muscular fibres, contracting from above downward, strip the bolus into the stomach. [For nervous mechanism of Deglutition, see Medulla Oblongata.] Gastric Digestion. The stomach is a dilation of the alimentary canal, 13 inches long, 5 inches deep, having a capacity of about 5 pints ; there ' can be distinguished a cardiac and pyloric orifice, a greater and lesser curva- ture, a greater and lesser pouch. It possesses three coats : 1. Serous, a reflection of the peritoneum. 2. Muscular, the fibres of which are arranged longitudinally, transversely and obliquely. 3. Mucous, thrown into folds, forming the rugae. Imbedded in the mucous coat are immense numbers of mucous and true gastric glands. In the pyloric end of the stomach are found the mucous glands, which are lined with columnar epithelium throughout their extent. In the cardiac end are found the true peptic glands (Fig. 3), the ducts of which are also lined with columnar cells, while the secretory parts are lined with two distinct -varieties of cells. Oije variety consists ot 28 HUMAN PHYSIOLOGY. small spheroidal, granular cells, which border the lumen of the gland, and are known as the chief cells ; the other variety consists of large, oval, well- defined granular cells, much less abundant, and are situated between the basement membrane of the gland and the chief cells. From their position they have been termed parietal cells. During the intervals of digestion the chief cells are pale, and the hyaline substance of which they are com- posed is finely granular. During the stage of active secretion the cells FIG. 3. Diagram showing the relation of the ultimate twigs of the blood vessels, V and A, and of the absorbent radicles to the glands of the stomach and the different kinds of epithe- lium, viz., above cylindrical cells ; small, pale cells in the lumen, outside which are the dark ovoid cells. From Yeo's Text-Book of PJiysiology. become swollen and turbid, and are then said to be rich in pepsin. Toward the end of digestion the granules disappear, the cells become pale and return to their former size. During the intervals of digestion, the mucous membrane of the stomach is pale and covered with a layer of mucus. Upon the introduction of food, the blood vessels dilate and become filled with blood, and the mucous membrane becomes, red. At the same time small drops of a fluid, the DIGESTION. 29 gastric juice, begin to exude upon its surface, which gradually run together and trickle down the sides of the stomach. The secretion of gastric juice is a reflex act, taking place through the central nervous system and called forth in response to the stimulus of food in the stomach. That the central nervous system also directly influences the production of the secretion is shown by the fact that mental emotion, such as fear and anger, will arrest or vitiate the normal secretion. The reflex nature of the process can be shown by experimentation upon the pneumo- gastric nerve. If during digestion, when the peristaltic movements are active and the gastric mucous membrane flushed and covered with gastric juice, the pneumogastric nerves are divided on both sides, the mucous membrane becomes pale, the secretion is arrested and the peristaltic movements become less marked. Stimulation of the peripheral end produces no constant effects ; stimulation of the central end, however, is at once followed by dilatation of the vessels, flushing of the mucous membrane and a re- establishment of the secretion. It is evident, therefore, that during digestion afferent impulses are passing up thepneumogastrics to the medulla ; efferent impulses, in all proba- bility, pass through the fibres of the sympathetic nervous system to the blood vessels and glands concerned in the elaboration of the gastric juice. After all the nervous connections of the stomach are divided, a small quantity of juice continues to be secreted for several days. This has been attributed to the action of a local nervous mechanism and to the direct action of the food upon the protoplasm of the secreting cells. The Gastric Juice is a secretion of the true peptic glands, and when obtained from the stomach through a fistulous opening, is a clear, straw- colored fluid, decidedly acid, with a specific gravity of 1.005 t i.oio. COMPOSITION OF GASTRIC JUICE. Water 975o Pepsin 15.00 Hydrochloric acid 4.78 Inorganic salts 5.22 1000.00 The water forms the largest part of the fluid, and holds in solution the other ingredients. It results from a transudation from the blood vessels under the increased blood supply. Of the inorganic salts the chlorides of sodium and potassium are the most abundant. Pepsin is the organic nitrogenize.d ferment of the gastric juice, and is formed, during the intervals of digestion, by the peptic cells. In the X 30 HUMAN PHYSIOLOGY. presence of a small per cent, of an acid, it acquires the property of con- verting the albumen of the food into albuminose or peptones. Hydrochloric acid is present in small quantity, and gives the juice its acidity. In all probability, its production is due to the activity of the parietal cells. These two characteristic ingredients of the gastric juice exist in a state of combination as hydrocliloro-peptic acid, and the presence of both is absolutely essential for the complete digestion of the food. When the food enters the stomach, it is subjected to the peristaltic action of the muscular coat, and thoroughly incorporated with the gastric juice. This fluid has a twofold action upon the food : 1st. A physical action, by which the fibrous tissues of meats, the cellulose and hard parts of grains and vegetables, are dissolved away until the food is disintegrated and reduced to the liquid condition. 2d. A chemical action, by which the albuminous principles are transformed into peptones. The more important foods with their contained albuminous principles are shown on page 19. Upon meat the gastric juice has a decidedly disintegrating action. The connective tissue is first dissolved, the fibres are separated, the sarcolemma softened, and the whole reduced to a grumous, pultaceous mass. Milk undergoes coagulation in from ten to fifteen minutes, the casein being precipitated in the form of soft flocculi, which are easy of transformation into peptone. Upon Vegetable tissues, the gastric juice exerts also a dis- integrating action ; the cellulose and woody fibres are dissolved and the nutritive principles liberated. Bread undergoes liquefaction quite readily. The Principal Action of the gastric juice, however, is to transform the different albuminous principles of the food into peptones or albuminose, the different stages of which are due to the acid and pepsin respectively. When freed from its combination, the hydrochloric acid converts the albumen into acid albtimen or parapeptone ; while this intermediate product is being formed, the pepsin converts it at once into peptone. In order that the digestion of albumen may be complete, it is necessary that both the acid and pepsin be present in proper quantity. Before digestion, the albuminous principles are insoluble in water and incapable of being absorbed. After digestion, they become soluble and are readily absorbed. Peptones differ from the albumins in being 1 . Diffusible, passing rapidly through the mucous membrane and walls of the blood vessels. 2. Non-coagulable by heat, nitric or acetic acids; but are readily precipi- tated by tannic acid. 3. Soluble in water and saline solutions. DIGESTION. 31 4. Assimilable by the blood ; when injected into it, they do not reappear in the urine. Gastric juice exerts no influence either upon grape sugar, cane sugar, starch or fat. Gastric Digestion occupies on the average from 3 to 5 hours, but varies in duration according to the nature and quantity of the food, exercise, temperature, etc. TABLE SHOWING DIGESTIBILITY OF VARIOUS ARTICLES OF FOOD. HOURS. MINUTES. Eggs, whipped, I 30 " soft boiled, 3 " hardboiled, 3 30 Oysters, raw, 2 55 " stewed, 3 30 Lamb, broiled, 2 30 Veal, broiled, 4 Pork, roasted, 5 15 Beefsteak, broiled, 3 Turkey, roasted, 2 25 Chicken, boiled, 4 " fricasseed, 2 45 Duck, roasted, ,..., 4 Soup, barley, boiled, I 30 " bean, " 3 " chicken, " 3 " mutton, " 3 30 Liver, beef, broiled, 2 Sausage, " 3 20 Green corn, boiled, 3 45 Beans, " 2 30 Potatoes, roasted, 2 30 " boiled, ,, 3 30 Cabbage, " 4 30 Turnips, " 3 30 Beets " 3 45 Parsnips, " 2 30 The Amount of gastric juice secreted in 24 hours varies, under normal conditions, from 8 to 14 pounds. Movements of the Stomach. As soon as digestion commences, the cardiac and pyloric orifices are closed ; the walls of the stomach contract upon the food, and a peristaltic action begins, which carries the food along the greater and lesser curvatures, and thoroughly incorporates it with the 32 HUMAN PHYSIOLOGY. gastric juice. As soon as any portion of the food is digested, it passes through the pylorus into the intestine. Vomiting. The act of vomiting is usually preceded by nausea and a discharge of saliva into the mouth. This is then swallowed, and carries into the stomach a quantity of air which facilitates the ejection of the con- tents of the stomach by aiding the relaxation of the cardiac sphincter. A deep inspiration is then taken, during which the lower ribs are drawn in and the diaphragm descends and remains contracted. At the same time the glottis is closed. A sudden expiratory effort is now made, and the cardiac orifice being open, the abdominal muscles contracting, press upon the stomach and forcibly eject its contents into the mouth. Intestinal Digestion. The intestine is about 20 feet long, \}/ 2 inches in diameter, and possesses three coats : 1. Serous (peritoneal). 2. Muscular, the fibres of which are arranged longitudinally and trans- versely. 3. Mucous, thrown into folds, forming the valvula conniventes. This stage of digestion is probably the most complex and important; here the different alimentary principles are further elaborated and prepared for absorption into the blood by being acted upon by the intestinal juice, pancreatic juice and bile. Throughout the mucous coat are imbedded the intestinal follicles, the glands of Brunner and Lieberklihn. They secrete the true intestinal juice, which is an alkaline, viscid fluid, composed of water, organic matter and salts. Its function is to convert starch into glucose, and assist in the digestion of the albuminoids. The Pancreatic Juice is secreted by the pancreas, a flattened gland about six inches long, running transversely across the posterior wall of the abdomen, behind the stomach ; its duct opens into the duodenum. The pancreas is similar in structure to the salivary glands, consisting of a system of ducts terminating in acini. The acini are tubular or flask- shaped, and consist of a basement membrane lined by a layer of cylindrical, conical cells, which encroach upon the lumen of the acini. The cells exhibit a difference in their structure (Fig. 4), and may be said to consist of two zones, viz., an ottter parietal zone, which is transparent and appar- ently homogeneous, staining rapidly with carmine ; an inner zone, which borders the lumen, and is distinctly granular and stains but slightly with carmine. These cells undergo changes similar to those exhibited by the cells of the salivary glands during and after active secretion. As soon as DIGESTION. 33 the secretory activity of the pancreas is established, the granules disappear, and the inner granular layer becomes reduced to a very narrow border while the outer zone increases in size and occupies nearly the entire cell. During the intervals of secretion, however, the granular layer reappears and increases in size until the outer zone is reduced to a minimum. It would seem that the granular matter is formed by the nutritive processes occurring in the gland during rest, and is discharged during secretory activity into the ducts and takes part in the formation of the pancreatic secretion. FIG. 4. d One saccule of the pancreas of the rabbit in different states of activity. A. After a period of rest, in which case the outlines of the cells are indistinct, and the inner zone, VlP Dart nf thp rells (a.\ next tVlf llimpn ( /~\ ic KrrQr1 Qnrl fill crrarni1p Book of Physiology, after Kuhne and Lea The pancreatic juice is transparent, colorless, strongly alkaline and viscid, and has a specific gravity of 1.040. It is one of the most important of the digestive fluids, as it exerts a transforming influence upon all the classes of alimentary principles, and has been shown to contain at least three distinct ferments. It has the following composition : COMPOSITION OF PANCREATIC JUICE. Water 900.76 Albuminoid substances 90.44 Inorganic- salts 8.80 1000.00 The pancreatic juice is characterized by its action: 1st Upon starch. X 34 HUMAN PHYSIOLOGY. When starch is subjected to the action of the juice, it is at once transformed into glucose ; the change takes place more rapidly than when saliva is added. This action is caused by the presence of a special ferment, amyl- opsin. 2d. Upon albumen. The albuminous bodies are changed by the juice into, first, an alkali albumen, and then into peptone. The albumen does not swell up, as is the case in gastric digestion, but is gradually cor- roded and dissolved. This change is due to the presence of the ferment, trypsin. Long- continued action of trypsin converts the peptones into two crystalline bodies, leucine and tyrosin. 3d. Upon fats. The most striking action of the pancreatic juice is the emulsification of the fats or their sub- division into minute particles of microscopic size. This change takes place rapidly and depends upon the alkalinity of the fluid and the quantity of albumen present, combined with the intestinal movements. The neutral fats are also decomposed into their corresponding/^/// acids and glycerine ; the acids thus set free unite with the alkaline bases present in the intestine and form soaps. This decomposition of the neutral fats is caused by the ferment, steapsin. 4th. Upon cane sugar the juice also exerts a special influence, converting it readily into glucose. The total quantity of this fluid secreted in twenty-four hours has not been accurately determined ; it varies from one to two pounds ; it is poured out most abundantly an hour after meals. The Bile has an important influence in the elaboration of the food and its preparation for absorption. It is a golden-brown, viscid fluid, having a neutral or slightly alkaline reaction and a specific gravity of 1 .020. COMPOSITION OF BILE. Water 859.2 Sodium glycocholate \ Sodium taurocholate J Fat 9.2 Cholesterine 2.6 Mucus and coloring matter 29.8 Salts 7.8 The Biliary salts, sodium glycocholate and taurocholate, are character- istic ingredients, and are formed in the liver by the process of secretion, from materials furnished by the blood. It is probable that they are derived from the nitrogenized compounds, though the stages in the process are unknown. They are reabsorbed from the small intestine to play some ulterior part in nutrition. X DIGESTION. 35 Cholesterine is a product of waste taken up by the blood from the nervous tissues and excreted by the liver. It crystallizes in the form of rhombic plates, which are quite transparent. When retained within the blood, it gives rise to the condition of cholesteramia, attended with severe nervous symptoms. It is given off in the faeces under the form of stercorine. The Coloring matters which give the tints to the bile are biliverdin and bilirubin, and are probably derived from the coloring matter of the blood. Their presence in any fluid can be recognized by adding to it nitric acid containing nitrous acid, when a play of colors is observed, beginning with green, blue, violet, red and yellow. The Bile is both a secretion and an excretion ; it is constantly being formed and discharged by the hepatic ducts into the gall bladder, in which it is stored up, during the intervals of digestion. As soon as food enters the intestines, it is poured out abundantly, by the contraction of the walls of the gall bladder. The Amount secreted in 24 hours is about 2j^ pounds. Functions of the Bile, (i) It assists in the emulsification of the fats and promotes their absorption. (2) It tends to prevent putrefactive changes in the food. (3) It stimulates- the secretions of the intestinal glands, and excites the normal peristaltic movements of the bowels. The digested food, the chyme, is a grayish, pultaceous mass, but as it passes through the intestines it becomes yellow, from admixture with the bile. It is propelled onward by vermicular motion ; by the contraction of the circular and longitudinal muscular fibres. As the digested food passes through the intestines, the nutritious mat- ters are absorbed into the blood, and the residue enters the large intestine. The Faeces consist chiefly of indigestible matters, excretin, stercorin and salts; varying in amount from 4 to 7 oz. in 24 hours. Defecation is the voluntary act of extruding the faeces from the body ; accomplished by a relaxation of the sphincter muscle, the contraction of the walls of the rectum, assisted by the abdominal muscles. The Gases contained in the stomach and small intestine are oxygen, nitrogen, hydrogen and carbonic acid. In the large intestine, carbonic acid, sulphuretted and carburetted hydrogen. They are introduced with the food, and also developed by chemical changes in the alimentary canal. They distend the intestines, aid capillary circulation, and tend to prevent pressure. 36 HUMAN PHYSIOLOGY. ABSORPTION. Absorption has for its object the introduction of new materials into the blood, and takes place mainly from the alimentary tract, but also to some extent from the skin, respiratory surface and closed cavities of the body. The Agents of Absorption are the veins and lymphatics. As a result of the process of digestion, the different alimentary substances FIG. 5. Di iagram of the portal vein (/z/) arising in the alimentary tract and spleen (s), and car- rying the blood from these organs to the liver. From Yeo's Text-Book of Physiology. > are converted into forms which are capable of being absorbed into the blood, e. g., albuminose, glucose and fatty emulsion, water and inorganic matters undergoing no change, being already in a condition to be absorbed and to play a part in the nutritive process. The blood vessels which are most active as absorbents, are the gastric, superior and inferior mesenteric veins. They arise in the coats of the ABSORPTION. 37 alimentary canal, and as they converge, unite with the splenic vein to form \\\z portal vein, which enters the liver (Fig. 5). As the digested mass of food, the chyme, passes through the alimentary canal, a large portion of it disappears; the veins absorb water, albuminose, glucose, and inorganic salts, and convey them directly into the liver; the blood of the portal vein being especially rich in these substances. At times, after the ingestion of large quantities of oleaginous food, the blood vessels take up, in addition, a certain quantity of fatty matter ; but this is not usually the case ; the fats being absorbed by special vessels, the lymphatics or lacteals. General Anatomy of the Lymphatic System. The lymphatics constitute a system of minute, delicate, transparent vessels, which, having their origin at the periphery of the body, pass forward toward the centre and empty into the veins at the base of the neck, by means of the thoracic duct. In their course they pass through small ovoid bodies, the lymphatic glands. Origin of the Lymphatics. The lymphatic vessels arise in several distinct ways : I . In lymph spaces or juice canals. Throughout the con- nective tissues of the body are found numbers of small, irregular, stellate spaces, which communicate freely with each other, and represent the ultimate radicles of the lymphatic vessels. They frequently contain lymph corpuscles. These spaces communicate with the lymph trunks, through the medium of the plexuses of lymph capillaries, which are much larger than capillary blood vessels, and are lined with endothelial cells with sinuous margins. 2. In openings on the surface of serous membranes. The sur- faces of the serous membranes are covered with a layer of endothelial cells. At intervals between these cells are found openings the stomata. These stomata communicate directly, through short canals, with the lymph capil- laries. The serous cavities may be thus regarded as large lymph spaces. 3. In perivascular lymph spaces. In the brain and spinal cord the capil- lary blood vessels are surrounded by a sheath, formed of endothelial cells, and which contains lymph. This space is in free communication with the lymphatics. By this means the blood vessel is bathed by the lymph stream. The lymphatic vessels of the small intestine (the lacteals] arise within the villous processes which project from the inner surface of the intestine throughout its entire extent. The wall of the villus is formed by an eleva- tion of the basement membrane, and covered by a layer of columnar epithelial cells. The basis of the villus consists of adenoid tissue, fine plexus of blood vessels, unstriped muscular fibres and the lacteal vessel. The adenoid tissue consists of a number of intercommunicating spaces, 38 HUMAN PHYSIOLOGY. containing leucocytes. The lacteal vessel possesses a thin, but distinct wall, composed of endothelial plates, with here and there openings, which bring the interior of the villus into communication with the spaces of the adenoid tissue. The structure of the larger vessels resembles that of the veins, consisting of three coats I. External, composed of fibrous tissue and muscular fibres, arranged longitudinally. 2. Middle, consisting of white fibrous and yellow elastic tissue, non- striated muscular fibres, arranged transversely. 3. Internal, composed of an elastic membrane, lined by endothelial cells. Throughout their course are found numerous semilunar valves, looking toward the larger vessels, formed by a folding of the inner coat and strengthened by connective tissue. Lymphatic Glands consist of an external fibrous covering, from the inner surface of which partitions of fibrous tissue, the trabeculce, pass into the substance of the gland, forming a stroma or network, in the meshes of which are found the true lymph corpuscles. The lymphatics which enter the gland are called the afferent vessels ; those which leave it, the efferent vessels. The Thoracic Duct is the general trunk of the lymphatic system, into which the vessels of the lower extremities, of the abdominal organs, of the left side of the head and left arm empty their contents, it is about twenty inches in length, arises in the abdomen, opposite the third lumbar vertebra, by a dilatation, the receptaculum chyli; ascends along the vertebral column to the seventh cervical vertebra, and terminates in the venous system at the junction of the internal jugular and subclavian veins on the left side. The lymphatics of the right side of the head, of the right arm and the right side of the thorax, terminate in the right thoracic duct, about one inch in length, which joins the venous system at the junction of the internal jugular and subclavian on the right side. Lymph is a clear, transparent fluid, slightly alkaline, having a saline taste and a specific gravity of 1.022. It is found in the lymphatic vessels throughout the body. Lymph contains a number of corpuscles (the leucocytes) resembling the white corpuscles of the blood, which increase in number as it passes through the lymphatic glands. They are about ^^ of an inch in diameter and somewhat granular; they are discharged into the blood, but their function is obscure. When withdrawn from the vessels, lymph undergoes sponta- neous coagulation, separating into serum and clot, as in the case of the blood. ABSORPTION. 39 COMPOSITION OF LYMPH. DR. OWEN REES. Water 9 6 -53 6 Proteids (serum- albumen, fibrin, globulin) 1.320 Extractives (urea, sugar, cholesterine) r -559 Fatty matter a trace Salts 0.585 IOO.OOO Origin of Lymph. Lymph is undoubtedly a transudation from the ?\ capillary blood vessels, occurring during the process of nutrition, and is \ identical, for the most part, with the liquor sanguinis, or plasma. As new material is constantly exuded, the old is absorbed by the lymphatics, and returned again to the circulation. Excrementitious matters, as urea, cholesterine, etc., are also taken up from the tissues by the lymphatics and emptied into the blood. The total quantity of lymph poured into the thoracic duct in 24 hours has been estimated at 3^ Ibs. , Chyle. As a result of the process of digestion, the oleaginous matters j which have been acted upon by the pancreatic juice and bile are trans- l formed into a condition of emulsion, forming an opaque, milky fluid, termed chyle, which adheres to the folds of the mucous membrane and villi. The Molecules of the fat are first absorbed by the epithelial cells, upon the surface of the villi, through which they pass and enter the lymphatics. Absorption by the Lacteals. The lacteals, or lymphatics of the small intestine, have their origin in the interior of the villi, from which they emerge and form a lymphatic plexus ; the larger branches of which pass through the layers of the mesentery, and finally terminate in the thoracic duct (Fig. 6). * In the intervals of digestion the lacteals contain clear, transparent lymph, and are invisible on account of their small size and delicacy. But during digestion these vessels become filled, from absorption of the chyle, and form a visible network of white vessels ramifying through the mesentery, and converging toward the receptaculum chyli. The lacteal vessels also absorb a small quantity of water, albuminose, ghicose and salts. COMPOSITION OF CHYLE. Water 902.37 Albumen 35. 1 6 Fibrin 3.70 Extractives J 5-65 Fatty m atters 36.01 Salts 7.11 1000.00 40 HUMAN PHYSIOLOGY. The Products of digestion find their way into the general circulation by two routes : I. Water > albuminose, glucose and salts, are mainly absorbed by the gas- FIG. 6. cl Diagram showing the course of the lacteals through the mesentery, and their termina- tion in the thoracic duct. The course of the thoracic duct and its termination at the junction of the internal jugular and subclavian veins. trie and mesenteric veins, carried into the liver, through the capillaries of which they pass, and enter the inferior vena cava by the hepatic veins. BLOOD. 41 2. The Fats are absorbed by the lacteals, emptied into the thoracic duct, and enter the blood at the junction of the internal jugular and subclavian veins. Forces aiding the movements of Lymph and Chyle. 1. Endosmosis. The continued transudation of matter from the capil- laries, and its absorption into the lymphatics by endosmosis, constitutes the main cause, the vis-a-tergo y of the movement of the lymph ; it is so con- siderable as to rupture the walls of the vessels if they are ligated. 2. Contraction of the non-striated muscular fibres in the walls of the lymphatic vessels, especially when fully distended, aided by the action of the valves, promotes the onward flow of the fluids. 3. Muscular contraction in all parts of the body, by exerting intermit- tent pressure upon the lymphatic vessels, hastens the current onward ; regurgitation being prevented by the closure of the valves. 4. The inspiratory movement, by expanding the chest, causes a dilation of the thoracic duct, and a rapid flow of lymph and chyle into it ; during expiration it is compressed, and the fluids forcibly expelled into the venous system. BLOOD. The Blood is a nutritive fluid containing all the elements necessary for the repair of the tissues ; it also contains principles of waste absorbed from the tissues, which are conveyed to the various excretory organs and by them eliminated from the body. The total amount of blood in the body is estimated to be about one- eighth of the body weight; from 16 to 18 pounds in an individual of aver- age physical development. The quantity varies during the 24 hours ; the maximum being reached in the afternoon, the minimum in the early morning hours. Blood is a heterogeneous, opaque red fluid, having an alkaline reaction, a saline taste, and a specific gravity of 1.055. The opacity is due to the refraction of the rays of light by the elements which the blood is composed. The color varies in hue, from a bright :arlet in the arteries to a deep purple in the veins, due to the presence of coloring matter, hemoglobin, in different degrees of oxidation. The alkalinity is constant, and depends upon the presence of the alka- ie sodium phosphate, Na 2 H PO 4 . The saline taste is due to the amount of sodium chloride present. The specific gravity ranges within the limits of health, from 1.045 to 1.075. D 42 HUMAN PHYSIOLOGY. The odor of the blood is characteristic, and varies with the animal from which it is drawn, due to the presence of caproic acid. The temperature of the blood ranges from 98 Fahr. at the surface to 107 Fahr. in the hepatic vein ; it loses heat by radiation and evaporation as it approaches the extremities, and as it passes through the lungs. Blood consists of two portions : 1. The Liquor Sanguinis or Plasma, a transparent, colorless fluid, in which are floating 2. Red and white corpuscles ; these constituting by weightless than one- half, 40 per cent., of the entire amount of blood. COMPOSITION OF PLASMA. DALTON. Water 902.00 Albumen 53. oo Paraglobulin , 22.00 Fibrinogen 3.00 Fatty matters 2.50 Crystallizable nitrogenous matters 4.00 Other organic matter 5.00 Mineral salts 8.50 Water acts as a solvent for the inorganic matters and holds in suspension the corpuscular elements. Albumen is the nutritious principle of the blood ; it is absorbed by the tissues to repair their waste and is transformed into the organic basis charactertistic of each structure. Paraglobulin or Jibrinoplastin is a soft amorphous substance precipitated by sodium chloride in excess, or by passing a stream of carbonic acid through dilute serum. Fibrinogen can also be obtained by strongly diluting the serum and passing carbonic acid through it for a long time, when it is precipitated as a viscous deposit. Fatty matters exist in small proportion, except in pathological conditions and after the ingestion of food rich in oleaginous matters ; it soon disap- pears, undergoing oxidation, generating heat and force, or is deposited as adipose tissue. Sugar is represented by glucose, a product of the digestion of saccharine matter and starches in the alimentary canal ; glycogenic matter is derived from the liver. The Saline constituents aid the process of osmosis, give alkalinity to the BLOOD. 43 blood, promote the absorption of carbonic acid from the tissues into the blood, and hold other substances in solution ; the most important are the sodium and potassium chlorides, the calcium and magnesium phosphates. Excrementitious matters are represented by carbonic acid, urea, creatin, creatinin, urates, oxalates, etc.; they are absorbed from the tissues by the blood and conveyed to the excretory organs, lungs, kidneys, etc. Gases. Oxygen, nitrogen, and carbonic acid exist in varying proportions. BLOOD CORPUSCLES. The corpuscular elements of the blood occur under two distinct forms, which, from their color, are known as the red and white c^puscles. The Red Corpuscles, as they float in a thin layer of the Liquor Sanguinis, are of a pale straw color; it is only when aggregated in masses that they assume the bright red color. In form they are circular and biconcave ; they have an average diameter of the ^Vtf ^ an i ncn - In mammals, birds, reptiles, amphibia and fish the corpuscles vary in size and number, gradually becoming larger and less numerous as the scale of animal life is descended, e. g. : TABLE SHOWING COMPARATIVE DIAMETER OF RED CORPUSCLES. Mammals. Birds. Reptiles. Amphibia. Fish. Man, y fa. Eagle, T1 fo Turtle, T ^, r . Frog, T ^ B . Perch, &. Chimpanzee, ^jVi- Owl, Ourang, 7353- Sparrow, i, Dog, W?u- Swallow, 7 Cat, ntW- Pigeon, 1 H g 1^30- Turkey, , Horse, jeW Goose, , Ox, laVr- Swan, -j Tortoise,^,. Toad, T0 ' 53 . Carp, Lizard, rK V*. Proteus, fo. Pike, Viper, T5 Vj. Siren, ,^. Eel, Amphiuma, 3 3 . In man and the mammals the red corpuscles present neither a nucleus nor a cell wall, and are universally of a small size. They can be readily distinguished from the corpuscles of birds, reptiles and fish, in which they \ are larger, oval in shape and possess a well-defined nucleus. The red corpuscles are exceedingly numerous, amounting to about 5,000,000 in a cubic millimetre of blood. In structure they consist of a firm, elastic, colorless framework, the stroma, in the meshes of which is entangled the coloring matter, the hemoglobin. CHEMICAL COMPOSITION OF RED CORPUSCLES. Water 688.00 Globulin 282.22 Haemoglobin 16.75 Fatty matter 2.31 Extractives 2.60 Mineral salts 8.12 44 HUMAN PHYSIOLOGY. H&moglobin, the coloring matter of the corpuscles, is an albuminous compound, composed of C. O. H. N. S. and iron. It may exist either in an amorphous or crystalline form. When deprived of all its oxygen, except the quantity entering into its intimate composition, the haemoglobin becomes darker in color, somewhat purple in hue, and is known as reduced hemoglobin. When exposed to the action of oxygen, it again absorbs a definite amount and becomes scarlet in color, and is known as oxy-hcemo- globin. The amount of oxygen absorbed is 1.76 c.cm. ( T 7 7 cubic inch) for i milligramme (^) grain of haemoglobin. It is this su^tance which gives the color to the venous and arterial blood. As the venous blood passes through the capillaries of the lungs, the reduced hemoglobin absorbs the oxygen from the pulmonary air and becomes oxy- hemoglobin, scarlet in color, and the blood becomes arterial. When the arterial blood passes into the systemic capillaries, the oxygen is absorbed by the tissues, the haemoglobin becomes reduced, purple in color, and the blood becomes venous. A dilute solution of oxy-hsemo- globin gives two absorption bands between the lines D and E of the solar spectrum. Reduced haemoglobin gives but one absorption band, occupying the space existing between the two bands of the oxy-haemo- globin spectrum. The Function of the red corpuscles is, therefore, to absorb oxygen and carry it to the tissues; the smaller the corpuscles, and the greater the number, the greater is the quantity of oxygen absorbed ; and, consequently, all the vital functions of the body become more active. The White Corpuscles are far less numerous than the red, the proportion being, on an average, about I white to 350 or 400 red ; they are globular in shape, and measure the ^-Vo f an i nc h i* 1 diameter, and consist of a soft, granular, colorless substance, containing several nuclei. The white corpuscles possess the power of spontaneous movement, alter- nately contracting and expanding, throwing out processes of their substance and quickly withdrawing them, thus changing their shape from moment to moment. These movements resemble those of the amceba, and for this reason are termed amoeboid. They also possess the capability of moving from place to place. In the interior of the vessels they adhere to the inner surface, while the red corpuscles move through the centre of the stream. The white corpuscles are identical with the leucocytes, and are found in milk, lymph, chyle and other fluids. Origin of Corpuscles. The red corpuscles take their origin from the mesoblastic cells in the vascular area of the developing embryo. In the adult they are produced from colorless nucleated corpuscles BLOOD. 45 resembling the white corpuscles. The spleen is the organ in which they are finally destroyed. The white corpuscles originate from the leucocytes of the adenoid tissue, and subsequently give rise to the red corpuscles and partly to new tissues that result from inflammatory action. COAGULATION OF THE BLOOD. When blood is withdrawn from the body and allowed to remain at rest, it becomes somewhat thick and viscid in from three to five minutes ; this viscidity gradually increases until the entire volume of blood assumes a jelly-like consistence, which occupies from five to fifteen minutes. As soon as coagulation is completed, a second process begins, which consists in the contraction of the coagulum and the oozing of a clear, straw-colored liquid, the serum, which gradually increases in quantity as the clot diminishes in size, by contraction, until the separation is completed, which occupies from 12 to 24 hours. The changes in the blood are as follows : Before coagulation. f Liq. Sanguinis 1 f Water. & /-. L - r Albumen. T . 1 1 i or > Consisting of 4 ^. u . Living blood. \ pl | Fibrmogen. I Salts [ Corpuscles. Red and white. After coagulation. f Crassamentum. "I r . . f Fibrin. I Clot or coagulum. } Containing <{ Corpuscles. Dead blood. { f Water. Serum. Containing -j Albumen. ( Salts. The serum, therefore, differs from the Liquor Sanguinis in not containing fibrin. In from 12 to 24 hours the upper surface of the clot presents a grayish appearance, the huffy coat, which is due to the rapid sinking of the red corpuscles beneath the surface, permitting the fibrin to coagulate without them, which then assumes a grayish -yellow tint. Inasmuch as the white corpuscles possess a lighter specific gravity than the red, they do not sink so rapidly, and becoming entangled in the fibrin, assist in forming the buffy coat. Continued contraction gives a cupped appearance to the surface of the clot. Inflammatory shites of the blood produce a marked increase in the 46 HUMAN PHYSIOLOGY. buffed and cupped condition, on account of the aggregation of the cor- puscles, and their tendency to rapid sinking. Nature of Coagulation. Coagulated fibrin does not preexist in the blood, but is formed at the moment blood is withdrawn from the vessels. According to Denis, a liquid substance, plasmine, exists in the blood, which, when withdrawn from the circulation, decomposes into fibrin and met-albumen. According to Schmidt, fibrin results from the union of fibrinoplastin (paraglobulin) and fibrinogen, brought about by the presence of a third substance, the fibrin ferment. According to Hammersten and others, the fibrin obtained from the blood after coagulation, comes from the fibrinogen alone, the conversion being brought about by the presence of a ferment substance, paraglobulin in this case having nothing to do with the change. This view is supported by the fact that the quantity of fibrin obtained from the blood is never greater than the quantity of fibrinogen previously present. The origin of the ferment is obscure, but there is reason to believe that it comes from the injured vascular coats or from the breaking up of the white corpuscles. Conditions Influencing Coagulation. The process is retarded by cold, retention within living vessels, neutral salts in excess, inflammatory conditions of the system, imperfect aeration, exclusion from air, etc. It is hastened by a temperature of 1 00 F., contact with air, rough sur- faces and rest. Blood coagulates in the body after the arrest of the circulation in the course of 12 to 24 hours; local arrest of the circulation, from compression or a ligature, will cause coagulation, thus preventing hemorrhages from wounded vessels. The Composition of the Blood varies in different portions of the body. The arterial differs from the venous, in being more coagulable, in containing more oxygen and less carbonic acid, in having a bright scarlet color, from the union of oxygen with haemoglobin; the purple hue of venous blood results from the deoxidation of the coloring matter. The blood of the portal vein differs in constitution, according to different stages of the digestive process ; during digestion it is richer in water, albuminous matter and sugar ; occasionally it contains fat ; corpuscles are diminished, and there is an absence of biliary substances. The blood of the hepatic vein contains a larger proportion of red and white corpuscles ; the sugar is augmented, while albumen, fat and fibrin are diminished. CIRCULATION OF THE BLOOD. 47 Pathological conditions of the Blood. 1. Plethora increase in the volume or quantity of blood. 2. Anemia deficiency of red globules with increase of water. 3. Leticocythemia increase of white and diminution of red corpuscles. 4. Glycohamia excess of sugar in the blood. 5. Urcemia increase in the amount of urea. 6. Cholesteramia an excess of cholesterine in the blood. 7. Thrombosis and embolism clotting of blood in the vessels and dissemination of coagula. 8. Lipcemia an excess of fat. 9. Melanczmia pigment in the blood. CIRCULATION OF THE BLOOD. The Object of the Circulation is to distribute nutritious blood to all portions of the system and to carry waste materials from the tissues to the various eliminating organs. The Circulatory Apparatus consists of the heart, arteries, capillaries and veins. The Heart is a hollow, muscular organ, pyramidal in shape, measuring 5^ inches in length and weighing from 10 to 12 ozs. in the male, and 8 to 10 ozs. in the female. It is invested externally by a closed fibro- serous sac, the pericardium, containing a small amount of fluid, which prevents friction as the visceral and parietal layers glide over each other, during the movements of the heart and lungs. The heart consists of four cavities, a right auricle and ventricle, and a left auricle and ventricle, completely separated by a vertical partition. The right is the venous side, receiving the blood from the venae cavee, and propelling it through the pulmonary artery into the lungs ; the left is the arterial side, receiving the arterial blood from the lungs by the pulmonary veins, and propelling it through the aorta to the system at large. The Auriculo-ventricular orifices are guarded on the right and left sides by the tricuspid and mitral valves respectively, while they are so arranged as to permit the flow of blood in the forward direction only; the orifices of the pulmonary artery and aorta are guarded by the semilunar valves. The Endocardium is a delicate, shining membrane, lining the interior of the heart, and continuous with the lining membrane of the blood vessels. The walls of the left ventricle are nearly half an inch in diameter, being two or three times thicker than the walls of the right; the force of its contraction is, therefore, much greater. 48 HUMAN PHYSIOLOGY. The Function of the Heart is to propel the blood to all portions of the vascular system; accomplished by successive alternate contractions and relaxations of its muscular walls, constituting the systole and diastole. Course of the blood through the Heart. The venous blood returned to the heart by the superior and inferior venae cavae is emptied, during the diastole, into the right auricle, on the contraction of which it is forced through the right auriculo-ventricular opening into the right ventricle and distends it. Upon contraction of the ventricle, the blood is propelled through the pulmonary artery into the lungs, where it undergoes aeration and is changed in color. The arterial blood is now collected by the pulmonary veins and poured into the left auricle ; thence it passes into the left ventricle, which becomes fully distended. Upon the contraction of the ventricle, the blood is pro- pelled into the aorta, and by it distributed to the system at large, to be again returned to the heart by the veins. Regurgitation from the ventricles into the auricles during the systole is prevented by the closure of the tricuspid and mitral valves ; regurgitation from the pulmonary artery and aorta into the ventricles during the diastole is prevented by the closure of the semilunar valves. Movements of the Heart. At each revolution, during the systole, the heart hardens and becomes shortened in its long diameter; its apex is raised up, rotated on its axis from left to right and thrown forward against the walls of the chest. The impulse of the heart, observed about two inches below the nipple, and one inch to the sternal side, between the fifth and sixth ribs, is caused mainly by the apex of the heart striking against the chest walls, assisted by the distention of the great vessels about the base of the heart. Sounds of the Heart. If the ear be placed over the cardiac region, two distinct sounds are heard during each revolution of the heart, closely following each other and which differ in character. The sound coinciding with the systole in point of time, the first sound, is long and dull, and caused by the closure and vibration of the auriculo- ventricular valves, the contraction of the walls of the ventricles and the apex beat ; the second sound, occurring during the diastole, is short and sharp, and caused by the closure of the semilunar valves. The capacity of the left ventricle when fully distended is estimated at from four to seven ounces. The frequency of the heart's action varies at different periods of life, but in the adult male it beats about 72 times per minute. It is influ- enced by age, exercise, posture, digestion, etc. CIRCULATION OF THE BLOOD. 49 Age. Before birth, the number of 'pulsations per minute averages 140 During the first year it diminishes to 128 During the third year diminishes to 95 From the eighth to the fourteenth years averages 84 In adult life the average is 72 Exercise and digestion increase the frequency of the heart's action. Posture influences the number of pulsations per minute ; in the male, standing, the average is 81 ; sitting, 71; lying, 66; independent, for the most part, of muscular effort. The Rhythmical movements of the heart are dependent upon I. An inherent irritability of the muscular fibre, which manifests itself as long as the nutrition is maintained. 2. The continuous flow of blood through its cavities, distending them and stimulating the endocardium. The force exerted by the left ventricle at each contraction has been ^estimated at 52 pounds. If a tube be inserted into the aorta, the pressure there will be sufficient to support a column of blood nine feet or a column of mercury six inches in height, the weight in either case being about four pounds. The estimation of the force which the heart is required to exert to support this column of blood, is arrived at by multiplying the pressure in the aorta (4 pounds) by the area of the internal surface of the left ventricle (about 13 inches). Each inch of the ventricle being capable of supporting a downward pressure of 4 pounds. Work done by the Heart. The work done by the heart is estimated by multiplying the amount of blood sent out from the right and left ventricles at each contraction, by the pressure in the pulmonary artery and aorta respectively, e. g. t when the right ventricle contracts, it forces out one- quarter pound of blood, and in so doing must overcome a pressure in the pulmonary artery sufficient to support a column of blood three feet in height; that is, must exert energy sufficient to raise ^ Ib. 3 feet, or % X 3 or % Ib. one foot. When the left ventricle contracts, it sends out % Ib. ol blood, and in so doing, the left ventricle must overcome a pressure in the aorta sufficient to support a column of blood nine feet in height; that is must exert energy sufficient to raise J^ Ib. 9 feet, or ^ X 9 or 2 X ^ s - one foot. Work done is estimated by the amount of energy required to raise a definite weight a definite height, the unit, the foot pound, being that required to raise one pound one foot. The heart, therefore, at each systole exerts energy sufficient to raise 3 foot pounds, and as it contracts 72 times per minute, it would raise in that time 3 X 7 2 or 216 foot pounds ; and in one hour 216 X or 12,960 foot 50 HUMAN PHYSIOLOGY. pounds; and in 24 hours 12,960 X 2 4 r S 11 ^ f ot pounds or 138.5 foot tons. Influence of the Nervous System upon the Heart. When the heart of a frog is removed from the body, it continues to beat for a variable length of time, depending upon the nature of the conditions surrounding it. The heart of warm-blooded animals continues to beat but for a very short time. The cause of the continued pulsations of the frog heart is the presence of nervous ganglia in its substance. These ganglia have not been shown to exist in the mammalian heart, but there is reason to believe that the nervous mechanism is fundamentally the same. The ganglia of the heart are three in number, one situated at the open- ing of the inferior vena cava (the ganglion of Remak), a second situated in the auriculo- ventricular septum (the ganglion of Bidder), and a third situated in the inter-auricular septum (the ganglion of Ludwig). The first two are motor in function and excite the pulsations of the heart ; the third is inhibitory in function and retards the action of the heart. The actions of these ganglia, though for the most part automatic, are modified by im- pressions coming through nerves from the medulla oblongata. When the inhibitory centre is stimulated by muscarin, the heart is arrested in diastole ; when atropia is applied, the heart recommences to ^beat, because atropia paralyzes the inhibitory centre. The nerves modifying the action of the heart are the Pneutnogastric (Vagus) and the Accelerator nerves. The Pneumogastric nerve, after emerging from the medulla, receives motor fibres from the spinal accessory nerve. It then passes downward, giving off branches, some of which terminate in the inhibitory ganglion. Stimulation of the vagus by increasing the activity of the inhibitory centre arrests the heart in diastole with its cavities full of blood ; but as the stimu- lation is only temporary, after a few seconds the heart recommences to beat; at first the pulsations are weak and feeble, but soon regain their original vigor. After the administration of atropia in sufficient doses to de- stroy the termination of the pneumogastric, stimulation of its trunk has no effect upon the heart. The inhibitory fibres in the vagus are constantly in action, for division of the nerve on both sides is always followed by an increase in the frequency of the heart's pulsations. The Accelerator fibres arise in the medulla, pass down the cord, emerge in the cervical region, pass to the last cervical and first dorsal ganglia of the sympathetic, and thence to the heart. Stimulation of these fibres causes an increased frequency of the heart's pulsations, but they are diminished in force. ARTERIES. 51 ARTERIES. The Arteries are a series of branching tubes conveying blood to all portions of the body. They are composed of three coats 1. External, formed of areolar and elastic tissue. 2. Middle, contains both elastic and muscular fibres, arranged trans- versely to the long axis of the artery. The elastic tissue is more abundant in the larger vessels, the muscular in the smaller. 3. Internal, composed of a thin homogeneous membrane, covered with a layer of elongated endothelial cells. The arteries possess both elasticity and contractility. The Property of Elasticity allows the arteries already full to accommo- date themselves to the incoming amount of blood, and to convert the intermittent acceleration of blood in the large vessels into a steady and continuous stream in the capillaries. The Contractility of the smaller vessels equalizes the current of blood, regulates the amount going to each part, and promotes the onward flow of blood. Blood Pressure. Under the influence of the ventricular systole, the recoil of the elastic walls of the arteries, and the resistance offered by the capillaries, the blood is constantly being subjected to a certain amount of pressure. If a large artery of an animal be divided, and a glass tube of the same calibre be inserted into its orifice, the blood will rise to a height of about nine feet ; or if it be connected with a mercurial manometer, the mercury will rise to a height of six inches. This height will be a measure of the pressure in the vessel. The absolute quantity of mercury sustained by an artery can be arrived at by multiplying the height of the column by the area of a transverse section of that artery. The pressure of the blood is greatest in the large arteries, but gradually decreases toward the capillaries. The blood pressure is increased or diminished by influences acting upon the heart or upon the peripheral resistance of the capillaries, viz. : If, while the force of the heart remains the same, the number of pulsa- tions per minute increases, thus increasing the volume of blood in the arteries, the pressure rises. If the rate remains the same, but the force increases, the pressure again rises. Causes that increase the peripheral resistance by contracting the arterioles, e. g., vasomotor nerves, cold, etc., produce an increase of the pressure. On the other hand, influences which diminish either the volume of the blood, or the number of pulsations, or the force of the heart, or the pe- ripheral resistance, lower the pressure. 52 HUMAN PHYSIOLOGY. The Pulse is the sudden distention of the artery in a transverse and longitudinal direction, due to the injection of a volume of blood into the arteries at the time of the ventricular systole. As the vessels are already full of blood, they must expand in order to accommodate themselves to the incoming volume of blood. The blood pressure is thus increased, and the pressure originating at the ventricle excites a pulse wave, which passes from the heart toward the capillaries at the rate of about twenty-nine feet per second. It is this wave that is appreciated by the finger. The Velocity with which the blood flows in the arteries diminishes from the heart to the capillaries, owing to an increase of the united sectional area of the vessels, and increases in rapidity from the capillaries toward the heart. It moves most rapidly in the large vessels, and especially under the influence of the ventricular systole. From experiments on animals, it has been estimated to move in the carotid of man at the rate of sixteen inches per second, and in the large veins at the rate of four inches per second. The Calibre of the blood vessels is regulated by the vasomotor nerves, which have their origin in the gray matter of the medulla oblon- gata. They issue from the spinal cord through the anterior roots of spinal nerves, pass through the sympathetic ganglia, and ultimately are distributed to the coats of the blood vessels. They exert, at different times, a constricting and dilating action upon the vessels, thus keeping up the arterial tonus. Capillaries. The capillaries constitute a network of vessels of micro- scopic size, which distribute the blood to the inmost recesses of the tissues, inosculating with the arteries on the one hand and the veins on the other; they branch and communicate in every possible direction. The diameter of a capillary vessel varies from the -^^ to the -g^j of an inch ; their walls consist of a delicate homogeneous membrane, the TffffTnr f an i nc h * n thickness, lined by flattened, elongated, endothelial cells, between which, here and there, are observed stomata. It is through the agency of the capillary- vessels that the phenomena of nutrition and secretion takes place, for here the blood flows in an equable and continuous current, and is brought into intimate relationship with the tissues, two of the essential conditions for proper nutrition. The rate of movement in the capillary vessels is estimated at one inch in thirty seconds. In the capillary current the red corpuscles may be seen hurrying down the centre of the stream, while the white corpuscles in the still layer ad- here to the walls of the vessel, and at times can be seen to pass through the walls of the vessel by amoeboid movements. ARTERIES. 53 The passage of the blood through the capillaries is mainly due to the force of the ventricular systole and the elasticity of the arteries ; but it is probably also aided by a power resident in the capillaries themselves, the result of a vital relation between the blood and the tissues. The Veins are the vessels which return the blood to the heart ; they have their origin in the venous radicles, and as they approach the heart, converge to form larger trunks, and terminate finally in the venae cavae. They possess three coats 1 . External, made up of areolar tissue. 2. Middle, composed of non-striated muscular fibres, yellow, elastic and fibrous tissue. 3. Internal, an endothelial membrane, similar to that of the arteries. Veins are distinguished by the possession of valves throughout their course, which are arranged in pairs, and formed by a reflection of the internal coat, strengthened by fibrous tissues ; they always look toward the heart, and when closed prevent a return of blood in the veins. Valves are most numerous in the veins of the extremities, but are entirely absent in many others. The onward flow of blood in the veins is mainly due to the action of the heart ; but is assisted by the contraction of the voluntary muscles and the force of aspiration. Muscular contraction, which is intermittent, aids the flow of blood in the veins, by compressing them. As regurgitation is prevented by the closure of the valves, the blood is forced onward toward the heart. Rhythmical movements of veins have been observed in some of the lower animals, aiding the onward current of blood. During the movement of inspiration the thorax is enlarged in all its diameters, and the pressure on its contents at once diminishes. Under these circumstances a suction force is exerted upon the great venous trunks, which causes the blood to flow with increased rapidity and volume toward the heart. Venous pressure. As the force of the heart is nearly expended in driving the blood through the capillaries, the pressure in the venous system is not very marked, not amounting in the jugular vein of a dog to more than y 1 ^ that of the carotid artery. 7^he time required for a complete circulation of the blood throughout the vascular system has been estimated to be from 20 to 30 seconds, while for the entire mass of blood to pass through the heart 58 pulsations would be required, occupying 48 seconds. 54 HUMAN PHYSIOLOGY. The Forces keeping the blood in circulation are 1 . Action of the heart. 2. Elasticity of the arteries. 3. Capillary force. 4. Contraction of the voluntary muscles upon the veins. 5. Respiratory movements. RESPIRATION. Respiration is the function by which oxygen is absorbed into the blood and carbonic acid exhaled. The appropriation of the oxygen and the evolution of carbonic acid takes place in the tissues as a part of the general nutritive processs ; the blood and respiratory apparatus constituting the media by means of which the interchange of gases is accomplished. The Respiratory Apparatus consists of the larynx, trachea and lungs. The Larynx is composed of firm cartilages, united together by liga- ments and muscles ; running antero-posteriorly across the upper opening are four ligamentous bands, the two superior or false vocal cords, and the two inferior or true vocal cords, formed by folds of the mucous membrane. They are attached anteriorly to the thyroid cartilages and posteriorly to the arytenoid cartilages, and are capable of being separated by the contraction of the posterior crico-arytenoid muscles, so as to admit the passage of air into and from the lungs. The Trachea is a tube from four to five inches in length, three- quarters of an inch in diameter, extending from the cricoid cartilage of the larynx to the third dorsal vertebra, where it divides into the right and left bronchi. It is composed of a series of cartilaginous rings, which extend about two- thirds around its circumference, the posterior third being occupied by fibrous tissue and non-striated muscular fibres which are capable of dimin- ishing its calibre. The trachea is covered externally by a tough, fibre-elastic membrane, and internally by mucous membrane, lined by columnar ciliated epithelial cells. The cilia are always waving from within outward. When the two bronchi enter the lungs they divide and subdivide into numerous and smaller branch'es, which penetrate the lung in every direction until they finally terminate in i\it pulmonary lobules. As the bronchial tubes become smaller their walls become thinner ; the cartilaginous rings disappear, but are replaced by irregular angular plates RESPIRATION. 55 FIG. of cartilage ; when the tube becomes less than the ^ of an inch in di- ameter they wholly disappear, and the fibrous and mucous coats blend together, forming a delicate, elastic membrane, with circular muscular fibres. The Lungs occupy the cavity of the thorax, are conical in shape, of a pink color and a spongy texture. They are composed of a great number of distinct lobules, the pulmonary lobules, con- nected together by interlobular con- nective tissue. These lobules vary in size, are of an oblong shape, and are composed of the ultimate ramifications of the bronchial tubes, within which are contained the air vesicles or cells. The walls of the air vesicles, exceedingly thin and delicate, are lined internally by a layer of tessellated epithelium, exter- nally covered by elastic fibres, which give the lungs their elasticity and dis- tensibility. The Venous Blood is distributed to the lungs for aeration by the pulmonary artery, the terminal branches of which form a rich plexus of capillary vessels surrounding the air cells; the air and blood are thus brought into intimate relationship, bein by the delicate walls of the air cells and capillaries. The thoracic cavity in which the respiratory organs are lodged is of a conical shape, having its apex directed upward, its base downward. Its framework is formed posteriorly by the spinal column, anteriorly by the sternum, and laterally by the ribs and costal cartilages. Between and over the ribs lie muscles, fascia and skin; above the thorax is completely closed by the structures passing into it and by the cervical fascia and skin; below it is closed by the diaphragm. It is therefore an air-tight cavity. The Pleura. Each lung is surrounded by a closed serous membrane, the pleura, one layer of which, the visceral, is reflected over the lung, the other, \\-\t parietal, reflected over the wall of the thorax; between the two layers is a small amount of fluid which prevents friction during the play of the lungs in respiration. Diagram of the respiratory organs. The windpipe leading down from the larynx is seen to branch into two large bronchi, which subdivide after they enter their respective lungs. < separated only 56 HUMAN PHYSIOLOGY. Owing to the elastic tissue which is present in the lungs, they are very readily distensible, so much so, indeed, that the pressure of the air inside the trachea and lungs is sufficient to distend them until they completely fill all parts of the thoracic cavity not occupied by the heart and great vessels. The elastic tissue endows them not only with distensibility, but also with the power of elastic recoil, by which they are enabled to accom- modate themselves to all variations in the size of the thoracic cavity. When the chest walls recede, the air within the lungs expands and presses them against the ribs ; when the chest walls contract, the air being driven out, the elastic tissue recoils and the lungs return to their original condition. The movements of the lungs are therefore entirely passive. As the capacity of the chest in a state of rest is greater than the volume of the lungs after they are collapsed, it is quite evident that in the living condition the lungs are distended and in a state of elastic tension, which is greater or less in proportion as the thoracic cavity is increased or dimin- ished in size. The elastic tissue, always on the stretch, is endeavoring to pull the visceral layer of the pleura away from the parietal layer, but is antagonized by the pressure of the air within the air passages. This con- dition of things persists as long as the thoracic cavity remains air-tight ; but if an opening be made in the thoracic wall, the pressure of the external air which was previously supported by the practically rigid walls of the thorax now presses upon the lung with as much force as the air within the lung. The two pressures being neutralized, there is nothing to prevent the elastic tissue from recoiling, driving the air out and collapsing. The elastic ten- sion of the lungs can be readily measured in man after death by inserting a manometer into the trachea. Upon opening the thorax and allowing the tissue to recoil, the air presses upon the mercury and elevates it, the extent to which it is raised being the index of the pressure. Hutchinson calculated the pressure to be one-half pound to the square inch of the lung surface. Respiratory movements. The movements of respiration are two, and consist of an alternate dilatation and contraction of the chest, known as inspiration and expiration. 1. Inspiration is an active process, the result of the expansion of the thorax, whereby air is introduced into the lungs. 2. Expiration is a partially passive process, the result of the recoil of the elastic walls of the thorax, and the recoil of the elastic tissue of the lungs, whereby the carbonic acid is expelled. In Inspiration the chest is enlarged by an increase in all its diameters, viz. : RESPIRATION. 57 1. The vertical is increased by the contraction and descent of the dia- phragm when it approximates a straight line. 2. The antero-posterior and transverse diameters are increased by the elevation and rotation of the ribs upon their axes. In ordinary tranqziil inspiration the muscles which elevate the ribs and thrust the sternum forward, and so increase the diameters of the chest, are the external intercostals, running from above downward and forward, the sternal portion of the internal intercostals and the levatores costarum. In the extraordinary efforts of inspiration certain auxiliary muscles are brought into play, viz. : the sterno-mastoid, pectorales, serratus magnus, which increase the capacity of the thorax to its utmost limit. In Expiration the diameters of the chest are all diminished, viz. : 1. The vertical, by the ascent of the diaphragm. 2. The antero-posterior, by a depression of the ribs and sternum. In ordinary tranquil expiration the diameters of the thorax are dimin- ished by the recoil of the elastic tissue of the lungs and the ribs ; but in forcible expiration the muscles which depress the ribs and sternum, and thus further diminish the diameter of the chest, are the internal inter- costals, the infracostals, and the triangularis sterni. In the extraordinary efforts of expiration certain auxiliary muscles are brought into play, viz. : the abdominal and sacro-lumbalis muscles, which diminish the capacity of the thorax to its utmost limit. Expiration is aided by the recoil of the elastic tissue of the lungs and ribs and the pressure of the air. Movements of the Glottis. At each inspiration the rima glottidis is dilated by a separation of the vocal cords, produced by the contraction of the crico-arytenoid muscles, so as to freely admit the passage of air into the lungs : in expiration they fall passively together, but do not interfere with the exit of the air from the chest. Nervous Mechanism of Respiration. The movements of Respi- ratory muscles, though capable of being modified to a certain extent by efforts of the will, are of an automatic character, and called forth by nervous impulses emanating from the medulla oblongata. The Respiratory centre, the so-called vital point, generates the nerve impulses, which, trav- eling outward through the phrenic and intercostal nerves, excite contrac- tions of the diaphragm and intercostal muscles respectively. This centre is for the most part automatic in its action, though it is capable of being modified by impulses reflected to it .through various sensory nerves. This centre may be stimulated E 58 HUMAN PHYSIOLOGY. 1. Directly i by the condition of the blood. An increase of carbonic acid or a diminution of oxygen in the blood causes an acceleration of the respiratory movements ; the reverse of these conditions causes a diminution of the respiratory movements. 2. Indirectly ', by reflex action. The medulla may be excited to action through the pneumogastric nerve, by the presence of carbonic acid in the lungs irritating its terminal filaments ; through the fifth nerve, by irrita- tion of the terminal branches ; and through the nerves of general sensibility. In either case this centre reflects motor impulses to the respiratory muscles through \\\e phrenic, intercostals, inferior laryngeal and other nerves. Types of Respiration. The abdominal type is most marked in young children, irrespective of sex ; the respiratory movements being effected by the diaphragm and abdominal muscles. In the superior costal type, exhibited by the adult female, the respiratory movements are more marked in the upper part of the chest, from the 1st to the 7th ribs, permitting the uterus to ascend in the abdomen during preg- nancy without interfering with respiration. In the inferior costal type, manifested by the male, the movements are largely produced by the muscles of the lower portion of the chest, from the 7th rib downward, assisted by the diaphragm. The respiratory movements vary according to age, sleep and exercise, being most frequent in early life, but averaging 20 per minute in adult life. They are diminished by sleep and increased by exercise. There are about four pulsations of the heart to each respiratory act. During inspiration two sounds are produced ; the one, heard in the thorax, in the trachea and larger bronchial tubes, is tubular in character; the other, heard in the substance of the lungs, is vesicular in character. AMOUNT OF AIR EXCHANGED IN RESPIRATION, AND CAPACITY OF LUNGS. The Tidal or breathing volume of air, that which passes in and out of the lungs at each inspiration and expiration, is estimated at from 20 to 30 cubic inches. The Complemented air is that amount which can be taken into the lungs by a forced inspiration, in addition to the ordinary tidal volume, and amounts to about no cubic inches. The Reserve air is that which usually remains in the chest after the ordinary efforts of expiration, but which can be expelled by forcible expira- tion. The volume of reserve air is abojit loo cubic inches. The Residual air is that portion which remains in the chest and cannot RESPIRATION. 59 be expelled after the most forcible expiratory efforts, and which amounts, according to Dr. Hutchinson, to about loo cubic inches. The Vital Capacity of the chest indicates the amount of air that can be forcibly expelled from the lungs after the deepest possible inspiration, and is an index of an individual's power of breathing in disease and pro- longed severe exercise. The combined amounts of the tidal, the comple- mental and reserve air, 230 cubic inches, represents the vital capacity of an individual 5 feet 7 inches in height. The vital capacity varies chiefly with stature. It is increased 8 cubic inches for every inch in height above this standard, and diminishes 8 cubic inches for each inch below it. The Tidal Volume of air is carried only into the trachea and larger bronchial tubes by the inspiratory movements. It reaches the deeper portions of the lungs in obedience to the law of diffusion of gases, which is inversely proportionate to the square root of their densities. The ciliary action of the columnar cells lining the bronchial tubes also assists in the interchange of air and carbonic acid. The entire volume of air passing in and out of the thorax in 24 hours is subject to great variation, but can be readily estimated from the tidal volume and the number of respirations per minute. Assuming that an individual takes into the chest 20 cubic inches at each inspiration, and breathes 18 times per minute, in 24 hours there would pass in and out of the lungs 518,400 cubic inches or 300 cubic feet. Composition of Air : Oxygen, 20.81 parts; nitrogen, 79.19, forming a mechanical mixture in which exist traces of carbonic acid and watery vapor. The changes in the air effected by respiration are Loss of oxygen, to the extent of 5 cubic inches per 100 of air, or I in 20. Gain of carbonic acid, to the extent of 4.66 cubic inches per 100 of air or .93 inch in 20. , Increase of watery vapor and organic matter. Elevation of temperature. Increase and at times decrease of nitrogen. Gain of ammonia. The total quantity of oxygen withdrawn from the air and consumed by the body in 24 hours amounts to 15 cubic feet, and can be readily esti- mated from the amount consumed at each respiration. Assuming that one inch of oxygen remains in the lungs at each respiration, in one hour there are consumed 18 inches, and in 24 hours, 25,920 cubic inches or 15 cubic Y X 60 HUMAN PHYSIOLOGY. feet, weighing 18 oz. To obtain this quantity, 300 cubic feet of air are necessary. The quantity of carbonic acid exhaled in 24 hours varies greatly. It can be estimated in the same way. Assuming that an individual exhales 93 ~h cubic inch at each respiration, in one hour there are eliminated 1008 cubic inches, and in 24 hours 24,192 cubic inches or 14 cubic feet, contain- ing 7 ozs. of pure carbon. As oxygen and carbon unite to form an equal volume of carbonic acid gas, there disappears daily in the body one cubic foot of oxygen, which in all probability unites with the surplus hydrogen of the food to form water. The exhalation of carbonic acid is increased by muscular exercise; nitrogenous food ; tea, coffee and rice ; age, and by muscular development ; decreased by a lowering of temperature ; repose ; gin and brandy, and a dry condition of the air. Condition of the Gases in the Blood. Oxygen is absorbed from the lungs into the arterial blood by the coloring matter, hemoglobin, with which it exists in a state of loose combination, and is disengaged during the process of nutrition. Carbonic acid, arising in the tissues, is absorbed into the blood, in conse- quence of its alkalinity ; where it exists in a state of simple solution and also in a state of feeble combination with the carbonates, soda and potassa, forming the bicarbonates ; it is liberated by pneumic acid in the pulmonary tissue. Nitrogen is simply held in solution in the plasma. The amount of watery vapor thrown off from the lungs daily is about one pound, with which is mingled organic matter and ammonia. Changes in the Blood during Respiration. As the blood passes through the lungs it is changed in color, from the dark purple hue of venous blood to the bright scarlet of arterial blood. The heterogeneous composition of venous blood is exchanged for the uniform composition of the arterial. It gains oxygen and loses carbonic acid. Its coagulability is increased. Temperature is diminished. Asphyxia. If the supply of oxygen to the lungs be diminished and the carbonic acid retained in the blood, the normal respiratory movements cease, the condition of asphyxia ensues, which soon terminates in death. The phenomena of asphyxia are, violent spasmodic action of the respi- ANIMAL HEAT. 61 ratory muscles, attended by convulsions of the muscles of the extremities, engorgement of the venous system, lividity of the skin, abolition of sensi- bility and reflex action, and death. The cause of death is a paralysis of the heart, from over distention by blood. The passage of the blood through the capillaries is prevented by contraction of the smaller arteries, from irritation of the vasomotor centre. The heart is enfeebled by a want of oxygen and inhibited in its action by the inhibitory centres. ANIMAL HEAT. The Functional Activity of all the organs and tissues of the body is attended by the evolution of heat, which is independent, for the most part, of external conditions. Heat is a necessary condition for the due perform- ance of all vital actions ; though the body constantly loses heat by radia- tion and evaporation, it possesses the capability of renewing it and main- taining it at a fixed standard. The normal temperature of the body in the adult, as shown by means of a delicate thermometer placed in the axilla, ranges from 97.25 Fahr. to 99.5 Fahr., though the mean normalizm.- perature is estimated by Wunderlich at 98.6 Fahr. The temperature varies in different portions of the body, according to the degree in which oxidation takes place ; being the highest in the muscles during exercise, in the brain, blood, liver, etc. The conditions which produce variations in the normal temperature of the body are : age, period of the day, exercise, food and drink, climate, season and disease. Age. At birth the temperature of the infant is about i F. above that of the adult, but in a few hours falls to 95.5 F., to be followed in the course of 24 hours by a rise to the normal or a degree beyond. During childhood the temperature approaches that of the adult; in aged persons the tempera- ture remains about the same, though they are not as capable of resisting the depressing effects of external cold as adults. A dittrnal variation of the temperature occurs from 1.8 F. to 3.6 F. (Jurgensen) ; the maximum occurring late in the afternoon, from 4 to 9 P. M., the minimum, early in the morning, from I to 7 A. M. Exercise. The temperature is raised from i to 2 F. during active contractions of the muscular masses, and is probably due to the increased activity of chemical changes ; a rise beyond this point being prevented by its diffusion to the surface, consequent on a more rapid circulation, radia- tion, more rapid breathing, etc. 62 HUMAN PHYSIOLOGY. Food and drink. The ingestion of a hearty meal increases the tempera- ture but slightly; an absence of food, as in starvation, produces a marked decrease. Alcoholic drinks, in large amounts, in persons unaccustomed to their use, cause a depression of the temperature, amounting from l to 2 F. Tea causes a slight elevation. External temperature. Long continued exposure to cold, especially if the body is at rest, diminishes the temperature from i to 2 F., while exposure to a great heat slightly increases it. Disease frequently causes a marked variation in the normal temperature of the body, rising as high as 107 F. in typhoid fever, and 105 F. in pneumonia ; in cholera it falls as low as 80 F. Death usually occurs when the heat remains high and persistent, from 106 to 110 F. ; the increase of heat in disease is due to excessive production rather than to diminished elimination. The source of heat is to be sought for in the chemical decompositions and hydrations taking place during the general process of nutrition, and the combustion of the carbonaceous compounds by the oxygen of the inspired air ; the amount of its production is in proportion to the activity of the internal changes. Every contraction of a muscle, every act of secretion, each exhibition of nerve force, is accompanied by a change in the chemical composition of the tissues and an evolution of heat. The reduction of the disintegrated tissues to their simplest form by oxidation; the combination of the oxygen of the inspired air with the carbon and hydrogen of the blood and tissues, results in the formation of carbonic acid and water and the generation of a large amount of heat. Certain elements of the food, particularly the non-nitrogenized substances, undergo oxidation without taking part in the formation of the tissues, being transformed into carbonic acid and water, and thus increase the sum of heat in the body. Heat-producing Tissues. All the tissues of the body add to the general amount of heat, according to the degree of their activity. But special structures, on account of their mass and the large amount of blood they receive, are particularly to be regarded as heat producers ; e.g. : 1. During mental activity the brain receives nearly one-fifth of the entire volume of blood, and the venous blood returning from it is charged with waste matters, and its temperature is increased. 2. The muscular tissue, on account of the many chemical changes occur- ring during active contractions, must be regarded as the chief heat- producing tissue. SECRETION. 63 3. The secreting glands, during their functional activity, add largely to the amount of heat. The entire quantity of heat generated within the body has been demon- strated experimentally to be about 2300 calories, a calorie or heat unit being that amount of heat required to raise the temperature of one kilo, of water (2.2 Ibs.) one degree Centigrade. This quantity of heat if not utilized and retained within the body would elevate its temperature in 24 hours about 60 F. That this volume of heat depends very largely upon the oxidation of the food stuffs can be shown experimentally. The normal temperature of the body is maintained by a constant expen- diture of the heat in several directions. 1. In warming the food, drink and air that are consumed in 24 hours. For this purpose about 157 heat units are required. 2. In evaporating water from the skin and lungs; 619 heat units being utilized for this purpose. 3. In radiation and conduction. By these processes the body loses at least 50 per cent, of its heat, or 1156 heat units. 4. In the production of work ; the work of the circulatory, respiratory, muscular, and nervous apparatus being performed by the transformation of 369 heat units into units of work. The nervous system influences the production of heat in a part, by increasing the amount of blood going through it by its action upon the vasomotor nerves. Whether there exists a special heat centre has not been satisfactorily determined, though this is probable. SECRETION. The Process of Secretion consists in the separation of materials from the blood, which are either to be again utilized to fulfill some special pur- pose in the economy, or are to be removed from the body as excrementi- tious matter; in the former case they constitute the secretions, in the latter, the excretions. The materials which enter into the composition of the secretions are derived from the nutritive principles of the blood, and require special organs, e. g., gastric glands, mammary glands, etc., for their proper elaboration. The materials which compose the excretions preexist in the blood, and are the results- of the activities of the nutritive process; if retained within the body they exert a deleterious influence upon the composition of the blood. 64 HUMAN PHYSIOLOGY. Destruction of a secreting gland abolishes the secretion peculiar to it, and it cannot be formed by any other gland ; but among the excreting organs there exists a complementary relation, so that if the function of one organ be interfered with, another performs it, to a certain extent. CLASSIFICATION OF THE SECRETIONS. PERMANENT FLUIDS. Serous fluids. Vitreous humor of the eye. Synovial fluid. Fluid of the labyrinth of the internal Aqueous humor of the eye. ear. Cerebro- spinal fluid. TRANSITORY FLUIDS. Mucus. Gastric juice. Sebaceous matter. Pancreatic juice. Cerumen (external meatus). Secretion from Brunner's glands. Meibomian fluid. Secretion from Leiberkuhn's glands. Milk and colostrum. Secretion from follicles of the large Tears. intestine. Saliva. Bile (also an excretion). EXCRETIONS. Perspiration and the secretion of Urine. the axillary glands. Bile (also a secretion). FLUIDS CONTAINING FORMED ANATOMICAL ELEMENTS. Seminal fluid, containing spermatozoids. Fluid of the Graafian follicles. The essential apparatus for secretion is a delicate, homogeneous, structureless membrane, on one side of which, in close contact, is a capil- lary plexus of blood vessels, and on the other side a layer of cells whose physiological function varies in different situations. Secreting organs may be divided into membranes and glands. Serous membranes usually exist as closed sacs, the inner surface of which is covered by pale, nucleated epithelium, containing a small amount of secretion. The serous membranes are the pleura, peritoneum, pericardium, synovia! sacs, etc. The serous fluids are of a pale amber color, somewhat viscid, alkaline, coagulable by heat, and resemble the serum of the blood; their amount is but small ; the pleural varies from 4 to 7 drachms ; the peritoneal from I to 4 ounces ; the pericardial from I to 3 drachms. The synovia I fluid is colorless, alkaline, and extremely viscid, from the presence of synovine. SECRETION. 65 The function of serous fluids is to moisten the opposing surfaces, so as to prevent friction during the play of the viscera. The mucous membranes are soft and velvety in character, and line the cavities and passages leading to the exterior of the body, e.g., the gastro- intestinal, pulmonary and genito-urinary. They consist of a primary basement membrane covered with epithelial cells, which, in some situa- tions, are tessellated, in others, columnar. Mucus is a pale, semi-transparent, alkaline fluid, containing epithelial cells and leucocytes. It is composed, chemically, of water, an albuminous principle, mucosine, and mineral salts ; the principal varieties are nasal, bronchial, vaginal and urinary. Secreting Glands are formed of the same elements as the secreting membranes ; but instead of presenting flat surfaces, are involuted, forming tubules, which may be simple follicles, e.g., mucous, uterine or intestinal ; or compound follicles, e.g., gastric glands, mammary glands; or racemose glands, e.g., salivary glands and pancreas. They are composed of a basement membrane, enveloped by a plexus of blood vessels, and are lined by epithelial and true secreting cells, which in different glands possess the capability of elaborating elements characteristic of their secretions. In the production of the secretions two essentially different processes are concerned : 1. Chemical. The formation and elaboration of the characteristic organic ingredients of the secreting fluids, e.g., pepsin, pancreatin, takes place during the intervals of glandular activity, as a part of the general function of nutrition. They are formed by the cells lining the glands, and can often be seen in their interior with the aid of the microscope, e.g., bile in the liver cells, fat in the cells of the mammary gland. 2. Physical. Consisting of a transudation of water and mineral salts from the blood into the interior of the gland. During the intervals of glandular activity, only that amount of blood passes through the gland sufficient for proper nutrition ; when the gland begins to secrete, under the influence of an appropriate stimulus, the blood vessels dilate and the quantity of blood becomes greatly increased beyond that flowing through the gland during its repose. Under these conditions a transudation of water and salts takes place, washing out the characteristic ingredients, which are discharged by the gland ducts. The discharge of the secretions is intermittent ; they are retained in the glands until they receive the appropriate stimulus, when 66 HUMAN PHYSIOLOGY. they pass into the larger ducts by the vis-a-tergo, and are then discharged by the contraction of the muscular walls of the ducts. The activity of glandular secretion is hastened by an increase in the blood pressure and retarded by a diminution. The nervous centres in the medulla oblongata influence secretion, (i) by increasing or diminishing the amount of blood entering a gland; (2) by exerting a direct influence upon the secreting cells themselves, the centres being excited by reflex irritation, mental emotion, etc. MAMMARY GLANDS. The Mammary Glands secrete the milk, and undergo at different periods of life remarkable changes in structure. Though rudimentary in childhood, they gradually increase in size as the young female approaches puberty. The gland presents, at its convexity, a small prominence of skin, the nipple, surrounded by an areola of a deeper tint. It is covered anteriorly by a layer of adipose tissue and posteriorly by a fibrous structure which attaches it loosely to the pectoralis muscle. During utero-gestation the mammae become large, firm, well-developed and lobulated ; the areola becomes darker and the veins more prominent. In the intervals of lactation the glands gradually shrink in size to their original condition, undergo involution, and become non-secreting organs. Structure of the Mammae. The mamma is a conglomerate gland, consisting of a number of lobes, from 15 to 20 in number, each of which is subdivided into lobules made up of gland vesicles or acini. The ducts which convey the secretion to the exterior, the lactiferous ducts, open by 15 to 20 orifices upon the surface of the nipple, at the base of which they are dilated to form little reservoirs in which the milk collects during the periods of active secretion. . The walls of the lacteal duct consist of white, fibrous tissue, and non- striated muscular fibres, lined by short columnar cells, which disappear during active lactation. The ducts measure about the j 1 ^ of an inch in diameter ; as they pass into the substance of the gland, each duct divides into a number of branches, which are distributed to distinct lobules and terminate in the acini. An acinus is made up of a number of vesicles composed of a homoge- neous membrane, lined by pavement epithelium. The gland vesicles are held together by white, fibrous tissue, which unites the lobules into lobes. MILK. 67 MILK. Milk has a pale blue color, is almost inodorous, of a sweetish taste, an alkaline reaction, and a specific gravity varying from 1.025 to 1.046. Examined microscopically it is seen to contain an immense number of globules, measuring the T o^o"o ^ an ^ 11CQ in diameter, suspended in a clear fluid; these are the milk globules, formed of a small mass of oily matter covered by a layer of albumen. The quantity of milk secreted by the human female in 24 hours, during the period of lactation, is about two to three pints; the quantity removed by the infant from a full breast at one time being about two ounces. COMPOSITION OF MILK. Water 890.00 Proteids, including casein and serum albumen 35- Fatty matter (butter) 25.00 Sugar (lactose) with extractives 48.00 Salts..., 2.00 1000.00 Casein is the nutritive principle of milk, and constitutes its most import- ant ingredient. It is held in solution by an alkali, but upon the addition of an acid it undergoes coagulation, passing into a semi-solid form. The presence of lactic acid, resulting from a transformation of milk sugar, causes spontaneous coagulation to take place. The Fatty matter is more or less solid at ordinary temperature, and con- sists of margarine and oleine; when subjected to the churning process the globules run together and form a coherent mass, the butter. When milk is allowed to stand for a varying length of time the fat glob- ules rise to the surface, forming a layer more or less thick, the cream. Milk sugar or lactose is an important ingredient in the food of the young child ; it is readily transformed into lactic acid in the presence of nitro- genized ferments. Influences modifying the secretion. During lactation there is a demand for an increased amount of fluid, and if not supplied, the amount of milk secreted is diminished. Good food in sufficient quantity is neces- sary for the proper elaboration of milk, though no particular article influ- ences its production. Mental emotion at times influences the character of the milk, decreasing the amount of its different constituents. Mechanism of Secretion. The water and salts preexist in the blood and pass into the gland vesicles by osmosis. The casein, fatty matter and 68 HUMAN PHYSIOLOGY. sugar appear only in the mammary gland, but the mechanism of their for- mation is not understood. Colostrum is a yellowish, opaque fluid, formed in the mammary glands toward the latter period of utero-gestation ; it consists of water, albumen, fat, sugar and salts, and acts as a laxative to the newly-born infant. VASCULAR OR DUCTLESS GLANDS. The Vascular Glands are regarded as possessing the power of acting upon certain elements of the food and aiding the process of sanguinifica- tion ; of modifying the composition of the blood as it flows through their substance, by some act of secretion. The vascular glands are the spleen, supra-renal capsules, thyroid and thymus glands. The Spleen is about 5 inches in length, 6 ounces in weight, of a dark bluish color, and situated in the left hypochondriac region. It is covered externally by a reflection of the peritoneum, beneath which is the proper fibrous coat, composed of areolar and elastic tissue and non-striated muscu- lar fibres. From the inner surface of the fibrous envelope processes or trabeculae are given off, which penetrate the substance of the gland, form- ing a network, in the meshes of which is contained the spleen pulp. The splenic artery divides into a number of branches, some of which, when they become very minute, pass directly into veins, while others terminate in true capillaries. As the capillary vessels ramify through the substance of the gland, their walls frequently disappear and the blood passes from the arteries into the veins through lacuna (Gray). The splenic or Malpighian corpuscles are small bodies, spherical or ovoid in shape, the -fa of an inch in diameter, situated upon the sheaths of the small arteries. They consist of a delicate membrane, containing a semi-fluid substance composed of numerous small cells resembling lymph corpuscles. The spleen pulp is a dark red, semi-fluid substance, of a soft consistence, contained in the meshes of the trabeculae. In it are found numerous corpuscles, like those observed in the Malpighian bodies, blood corpuscles in a natural and altered condition, nuclei and pigment granules. Function of the Spleen. Probably influences the preparation of the albuminous food for nutrition ; during digestion the spleen becomes larger, its contents are increased in amount, and after digestion it gradually dimin- ishes in size, returning to the normal condition. EXCRETION. 69 The red corpuscles are here disintegrated, after having fulfilled their function in the blood ; the splenic venous blood containing relatively a small quantity. The white corpuscles appear to be increased in number, the blood of the splenic vein containing an unusually large proportion. The spleen serves also as a reservoir for blood when the portal circula- tion becomes obstructed. The nervous system controls the enlargement of the spleen ; division of the nerve produces dilatation of the vessels, stimulation contracts them. The Supra-renal Capsules are triangular, flattened bodies, situated above the kidney. They are invested by a fibrous capsule sending in trabeculse, forming the framework. The glandular tissue is composed of two portions, a cortical and medullary. The cortical being made up of small cylinders lined by cells and containing an opaque mass, nuclei and granular matter. The medullary consists of a fibrous network containing in the alveoli nucleated protoplasm. The Thyroid gland consists of a fibrous stroma, containing ovoid closed sacs, measuring on the average -fa of an inch, formed of a delicate membrane lined by cells ; the contents of the sacs consist of yellowish albuminous fluid. The Thymus gland is most developed in early life and almost disap- pears in the adult. It is divided by processes of fibrous tissue into lobules, and these again into follicles which contain lymphoid corpuscles. The functions vi the vascular glands appear to be the more complete elaboration of the blood necessary for proper nutrition; they are most highly developed during infancy and embryonic life, when growth and development are most active. EXCRETION. The Principal Excrementitious Fluids discharged from the body are the urine, perspiration and bile ; they hold in solution principles of waste which are generated during the activity of the nutritive process, and are the ultimate forms to which the organic constituents are reduced in the body. They also contain inorganic salts. The Urinary Apparatus consists of the kidneys, ureters and bladder. 70 HUMAN PHYSIOLOGY. KIDNEYS. The Kidneys are the organs for the secretion of urine ; they resemble a bean in shape, are from four to five inches in length, two in breadth, and weigh from four to six ounces. FIG. 8. 1" . Longitudinal section through the kidney, the pelvis of the kidney, and a number of renal calyces. A, branch of the renal artery; U, ureter; C, renal calyx ; i, cortex ; i', medullary rays; i", labyrinth, or cortex proper; 2, medulla; 2', papillary portion of medulla, or medulla proper; 2", border layer of the medirila; 3, 3, transverse section through the axes of the tubules of the border layer ; 4, fat of the renal sinus ; 5, 5, arterial branches ; *, transversely coursing medulla rays. 7ysen, after Henle. They are situated in the lumbar region, one on each side of the vertebral column, behind the peritoneum, and extend from the nth rib to the crest KIDNEYS. 71 of the ilium ; the anterior surface is convex, the posterior concave, and presents a deep notch, the hilum. The kidney is surrounded by a thick layer of fat, beneath which is the fibrous coat, thin and smooth, composed of dense white fibrous tissue with which are intermingled elastic fibres. It is adherent to the surface of the organ, but can easily be removed by dissection. The Substance of the Kidney is dense, but friable ; upon making a longitudinal section, and dividing it, there is presented a cavity, \he pelvis, lined by the proper fibrous coat and occupied by the expanded portion of the ureter. The kidney exhibits two structures, viz. : 1. An external or cortical portion, about */ of an inch in diameter, of a reddish color, and somewhat granular. 2. An internal or medullary portion, of a dark red color, arranged in the form of pyramids, the bases of which are directed toward the cortical portion, and the apices toward the pelvis, into which they project, and are covered by the calyces. The Cortical portion of the kidney consists of a delicate matrix containing an immense number of tubules, having a markedly convoluted appearance, and interlacing in every direction (the tubules of Ferrein). Throughout its structure are numerous ovoid bodies, the Malpighian bodies, which are the flask-like terminations of the convoluted tubules ; these tubes are composed of a delicate homogeneous membrane lined by nucleated cells. After pursuing a most intricate course in the cortical portion, they become narrower and form loops which dip into the pyramidal portion (Henle's tubules), returning upon themselves, to finally terminate in the straight tubes of the pyramids. Diagrammatic exposi-* The Malpighian bodies, the dilated extremities tion of the method in .. f A. v , , , , , the convoluted tubes, consist of a little sac (the capsule of Miiller), which is ovoid in shape, measuring about the ^1^ of an inch in diameter, and contains a tufted mass of minute blood vessels, over the surface of which is reflected a layer of cells. Medullary Substance. The conical masses, the pyramids of Mai- which the uriniferous tubes unite to form 72 HUMAN PHYSIOLOGY. pighi, consist of a number of straight tubes, which commence at the apex by from 10 to 20 openings; and as they pass toward the cortical portion, they divide and subdivide at acute angles, until a large mass of tubes is produced. These tubes are on the average about -5-^ of an inch in diameter, and composed of a thin, but firm, elastic, structureless membrane, lined by polygonal nucleated cells, which reduce the diameter of the lumen of the tube about two-thirds ; these are the straight tubes of Bellini. Blood vessels of the Kidney. The renal artery is of large size and enters the organ at the hilum ; it divides into several large branches, which penetrate the substance of the kidney, between the pyramids, at the base of which they form an anastomosing plexus, which completely surrounds them. From this plexus vessels follow the straight tubes toward the apex, while others, entering the cortical portion, divide into small twigs which enter the Malpighian body and form a mass of convoluted vessels, the glomerulus. After circulating through the Malpighian tuft the blood is gathered together by two or three small veins, which again subdivide and form a fine capillary plexus, which envelops the convoluted tubules ; from this plexus the veins converge to form the emulgent vein, which empties into the vena cava. The nerves of the kidney follow the course of the blood vessels and are derived from the renal plexus. The Ureter is a membranous tube, situated behind the peritoneum, about the diameter of a goose quill, 18 inches in length, and extends from the pelvis of the kidney to the base of the bladder, which it perforates in an oblique direction. It is composed of 3 coats, fibrous, muscular and mucous. The Bladder is a reservoir for the temporary reception of the urine prior to its expulsion from the body ; when fully distended it is ovoid in shape, and holds about one pint. It is composed of four coats, serous, muscular, the fibres of which are arranged longitudinally and circularly, areolar and mucous. The orifice of the bladder is controlled by the sphincter vesica, a muscular band about half an inch in width. As soon as the urine is formed it passes through the tubuli uriniferi into the pelvis, and from thence through the ureters into the bladder, which it enters at an irregular rate. Shortly after a meal, after the ingestion of large quantities of fluid, and after exercise, the urine flows into the blad- der quite rapidly, while it is reduced to a few drops during the intervals of digestion. It is prevented from regurgitating into the ureters on account of the oblique direction they take between the mucous and muscular coats. URINE. 73 Nervous Mechanism of Urination. When the urine has passed into the bladder, it is there retained by the sphincter vesicae muscle, kept in a state of tonic contraction by the action of a nerve centre in the lumbar region of the spinal cord. This centre can be inhibited and the sphincter relaxed, either reflexly, by impressions coming through sensory nerves from the mucous membrane of the bladder, or directly, by a voluntary impulse descending the spinal cord. When the desire to urinate is experienced, impressions made upon the vesical sensory nerves are carried to the centres governing the sphincter and detrusor urintz muscles and to the brain. If now the act of urination is to take place, a voluntary impulse, originating in the brain, passes down the spinal cord and still further inhibits the sphincter vesicse centre, with the effect of relaxing the muscle, and of stimulating the centre governing the detrusor muscle, with the effect of con- tracting the muscle and expelling the urine. If the act is to be sup- pressed, voluntary impulses inhibit the detrusor centre and possibly stimu- late the sphincter centre. The genito-spinal centre controlling these movements is situated in that portion of the spinal cord corresponding to the origin of the 3d, 4th and 5th sacral nerves. URINE. Normal Urine is of a pale yellow or amber color, perfectly transparent, with an aromatic odor, an acid reaction, a specific gravity of 1.020, and a temperature when first discharged of 100 Fahr. The color varies considerably in health, from a pale yellow to a brown hue, due to the presence of the coloring matter, urobilin or urochrome. The transparency is diminished by the presence of mucus, the calcium and magnesium phosphates and the mixed urates. The reaction is slightly acid, caused by the acid phosphate of sodium. After standing for a short time, an increased acidity is observed, due to an acid fermentation, from the presence of mucus. The urea is converted into ammonium carbonate, giving rise to a strong ammoniacal odor. The specific gravity varies from l.oio to 1.025. The quantity of urine excreted in 24 hours is between 40 and 50 fluid ounces, but ranges above and below this standard. The odor is characteristic, and caused by the presence of taurylic and phenylic acids, but is influenced by vegetable foods and other substances eliminated by the kidneys. 74 HUMAN PHYSIOLOGY. COMPOSITION OF URINE. Water 967. Urea ; 14.230 Other nitrogenized crystalline bodies, uric acid, prin- ~] cipally in the form of alkaline urates. Creatin, creatinin, xanthin, hypoxanthin. ,- Hippuric acid, leucin, tyrosin, taurin, cystin, all in j small amounts, and not constant. Mucus and pigment. Salts : Inorganic, principally sodium and potassium sul- ") phates, phosphates and chlorides, with magnesium j and calcium phosphates, traces of silicates and chlorides. 8 -'35 Organic: lactates, hippurates, acetates, formates, which appear only occasionally. Sugar a trace. Gases (nitrogen and carbonic acid principally). 1000.00 The Average Quantity of the principal constituents excreted in 24 hours is as follows : Water 52 fluid oz. Urea 512.4 grains. Uric acid 8.5 Phosphoric acid 45.0 Sulphuric acid 31.11 Inorganic salts 3 2 3- 2 5 Lime and magnesia 6.5 To Determine the amount of solid matters in any given amount of urine, multiply the last two figures of the specific gravity by the coefficient of Hseser, 2.33 ; e. g., in 1000 grains of urine having a specific gravity 1.022, there are contained 22 X 2 -33 = 51.26 grains of solid matter. The Elimination of the urinary constituents is accomplished by the two processes of filtration and secretion. i. By Filtration the water and mineral salts are removed from the blood ; this takes place, for the most part, in the Malpighian corpuscles, by the process of osmosis. The amount of these constituents eliminated varies with the pressure of blood in the renal arteries. All of the agencies which increase the general blood pressure increase the quantity of urine. Season. In summer, while the capillary vessels of the skin are dilated, and perspiration is abundant, there is a diminished blood pressure, and a consequent diminution in the amount of urine ; in winter the reverse takes place. COMPOSITION OF URINE. 75 During sleep the renal excretion is diminished, but increased in the morning hours, and especially after the ingestion of hearty meals. The nervous system influences the secretion of urine. Irritation of the medulla oblongata, a little above the origin of the pneumogastric and auditory nerves, increases the quantity ; division of the renal nerves destroys the nutrition of the kidney, and thus interferes with the elimina- tion of the urine. Mental emotion, fear, anxiety, etc., increase the amount secreted. 2. Secretion. While it is established that the Malpighian corpuscles permit the filtration of water and salts, it has also been shown that the renal epithelial cells lining the convoluted tubes are the agencies by which the solid matters, urea, creatin, etc., are removed from the blood, by a process of true secretion, which is independent of blood pressure and caused by the presence of these ingredients in the blood. Urea is the most important of the organic constituents of the urine. It is a colorless, neutral substance, crystallizing in four-sided prisms, soluble in boiling alcohol and water; when subjected to prolonged boiling it is decom- posed,' with the production of ammonium carbonate. Urea is not formed in the kidneys, but pre-exists in the blood. The Amount of Urea excreted in 24 hours is estimated at about 500 grains ; it is increased during the waking hours, by an animal diet and by prolonged muscular exertion ; diminished during sleep and by non-nitrogen- ized food. Source. Urea results from an imperfect oxidation of the albuminous principles of the food, and from a disintegration of the organic constituents of the tissues. Uric acid, or lit hie acid, is a constant ingredient of the urine; the amount excreted daily is about 8 grains; it is increased by nitrogenized, decreased by non-nitrogenized food. It exists in the urine in a free state, and as the urate of soda. It arises from the disassimilation of albuminous compounds, and when secreted in excess is deposited in a crystalline form, as a brown or " brick- red " sediment, with the sodium and ammonium urates. Creatin is a colorless, transparent substance, crystallizing in prisms ; found in blood, kidneys, and muscular tissue ; by boiling in acid solutions it is transformed into Creatinin, which resembles creatin chemically. It is soluble in water and alcohol, and crystallizes in colorless prisms. About 15 grains are excreted daily. 76 HUMAN PHYSIOLOGY. The Earthy phosphates are insoluble in water but held in solution in the urine by the acid reaction. If the urine becomes alkaline, they are deposited copiously, and yet may not be increased in quantity ; from 1 5 to 25 grains are excreted in 24 hours. The sulphates are those of sodium and potassium ; they are very soluble and do not appear as a precipitate ; the average quantity excreted in 24 hours is about 60 grains. Abnormal ingredients appear in the urine at times, in pathological con- ditions, e. g., sugar, albumen, biliary salts, etc. The Gases of the urine are carbonic acid and nitrogen. LIVER. The Liver is a highly vascular, conglomerate gland, appended to the alimentary canal, and performs the triple office of (i) excreting bile, (2) elaborating blood and (3) secreting glycogen. It is the largest gland in the body, weighing about 4^ pounds; it is situated in the right hypochondriac region, and retained in position by five ligaments, four of which are formed by duplicatures of the peritoneal investment. The proper coat of the liver is a thin but firm fibrous membrane, closely adherent to the surface of the organ, which it penetrates at the transverse fissure, and follows the vessels in their ramifications through its substance, constituting Glissorts capsule. Structure of the Liver. The liver is made up of a large number of small bodies, the lobules, rounded or ovoid in shape, measuring the -fa of an inch in diameter, separated by a space in which are situated blood vessels, nerves, hepatic ducts and lymphatics*. The lobules are composed of cells, which, when examined microscopi- cally, exhibit a rounded or polygonal shape, and measure, on the average, the fl fav of an inch in diameter ; they possess one, and at times two, nuclei ; they also contain globules of fat, pigment matter, and animal starch. The cells constitute the secreting structure of the liver, and are the true hepatic cells. The Blood vessels which enter the liver are (l) The portal vein, made up of \he gastric, splenic, superior and inferior mesenteric veins ; (2) the hepatic artery, a branch of the cceliac axis ; both of which are invested by a sheath of areolar tissue; the vessels which leave the liver are the hepatic veins, originating in its interior, collecting the blood distributed by the portal vein and hepatic artery, and conducting it to the ascending vena LIVER. 77 Distribution of Vessels. The portal vein and hepatic artery, upon entering the liver, penetrate its substance, divide into smaller and smaller branches, occupy the spaces between the lobules, completely surrounding and limiting them, and constitute the interlobular vessels. The hepatic artery, in its course, gives off branches to the walls of the portal vein and Glisson's capsule, and finally empties into the small branches of the porta I vein in the interlobular spaces. The interlobular vessels form a rich plexus around the lobules, from which branches pass to neighboring lobules and enter their substance, where they form a very fine network of capillary vessels, ramifying over the hepatic cells, in which the various functions of the liver are performed. The blood is then collected by small veins, converging toward the centre of the lobule, to form the intralobular vein, which runs through its long axis and empties into the sub-lobular vein. The hepatic veins are formed by the union of the sub-lobular veins, and carry the blood to the ascending vena cava; their walls are thin and adherent to the substance of the hepatic tissue. The Hepatic Ducts or Bile Capillaries originate within the lobules, in a very fine plexus lying between the hepatic cells ; whether the smallest vessels have distinct membranous walls, or whether they originate in the spaces between the cells by open orifices, has not been satisfactorily deter- mined. The Bile Channels empty into the interlobular ducts, which measure about ^Vo f an mc ^ m diameter, and are composed of a thin homogeneous membrane lined by flattened epithelial cells. As the interlobular bile ducts unite to form larger trunks, they receive an external coat of fibrous tissue, which strengthens their walls; they finally unite to form one large duct, the hepatic duct, which joins the cystic duct ; the union of the two forms the ductus communis choledochus, which is about three inches in length, the size of a goose quill, and opens into the duodenum. The Gall Bladder is a pear-shaped sack, about four inches in length, situated in a fossa on the under surface of the liver. It is a reservoir for the bile, and is capable of holding about one ounce and a half of fluid. It is composed of three coats, (i) serous, a reflection of the peritoneum, (2) fibrous and muscular, (3) mucous. (i) Bile. Mechanism of its Secretion. Bile does not preexist in the blood, but is formed in the interior of the hepatic cells, from materials derived from the venous as well as arterial blood. The secreted bile is 78 HUMAN PHYSIOLOGY. then taken up by the delicate plexus of vessels, from which it passes into the larger ducts, and finally either empties into the intestine or is regurgi- tated backward into the gall bladder, in which it is stored up during the intervals of digestion. Although the secretion of bile is constantly taking place, it is only when the food passes into the intestinal canal that this fluid is discharged abund- antly, under the influence of the contraction of the walls of the gall blad- der ; it increases in amount during the period of active digestion, from the second to the eighth hour, and then gradually diminishes. The Bile is both a secretion and an excretion ; it contains new constitu- ents which are formed only in the substance of the liver, and are destined to play an important part ultimately in nutrition ; it contains also waste ingredients which are discharged into the intestinal canal and eliminated from the body. The physical properties and functions of bile have been considered under the head of digestion (see page 34). (2) Elaboration of Blood. Besides the capability of secreting bile, the liver possesses the property of so acting upon and modifying the chemi- cal composition of the products of digestion, as they traverse its substance, that they readily assimilate with the blood, and are transformed into mate- rials capable of being converted into the elements of the blood and solid tissues. The albuminose particularly requires the modifying influence of the liver ; for if it be removed from the portal vein and introduced into the jugular vein, it is at once removed from the blood by the action of the kidneys. The blood of the hepatic vein differs from the blood of the portal vein, in being richer in blood corpuscles, both red and white ; its plasma is more dense, containing a less percentage of water and a greater amount of solid constituents, but no fibrin ; its serum contains less albumen, fat and salts, but its sugar is increased. (3) Glycogenic Function. In addition to the two preceding func- tions, Bernard, in 1848, demonstrated the fact that the liver, during life, normally produces a sugar-forming substance, analogous in its chemical composition to starch, which he termed glycogen ; also that when the liver is removed from the body, and its blood vessels thoroughly washed out, after a few hours sugar again makes its appearance, in abundance. It can be shown to exist in the blood of the hepatic vein as well as in a decoction of the liver substance, by means of either Trommer's or Fehling's SKIN. 79 tests, even when the blood of the portal vein does not contain a trace of sugar. Origin and Destination of Glycogen. Glycogen appears to be formed de novo in the liver cells, from materials derived from the food, whether the diet be animal or vegetable, though a larger per cent, is formed when the animal is fed on starchy and saccharine, than when fed on animal food. The glucose, which is one of the products of digestion, is absorbed by the blood vessels, and carried directly into the liver; as it does not appear in the urine, as it would if injected at once into the general circulation, it is probable that it is detained in the liver, dehydrated and stored up as glycogen. The change is shown by the following formula : Glucose. Water. Glycogen. C 6 H 12 S - H 2 = C 6 H 10 6 . The glycogen thus formed is stored up in the hepatic cells for the future requirements of the system. When it is carried from the liver it is again transformed into glucose by the agency of a ferment. Glycogen does not undergo oxidation in the Hood ; this takes place in the tissues, particularly in the muscles, where it generates heat and contributes to the development of muscular force. Glycogen, when obtained from the liver, is an amorphous, starch-like substance, of a white color, tasteless and odorless, and soluble in water; by boiling with dilute acids, or subjected to the action of an animal ferment, it is easily converted into glucose. When an excess of sugar is generated by the liver, it can be found, not only in the blood of the hepatic vein, but also in other portions of the body; under these circumstances it is eliminated by the kidneys, appearing in the urine, constituting the condition of glycosuria. The Nervous System influences the production of the glycogenic matter ; irritation of the medulla oblongata, between the auditory and pneu- mogastric nerves, is followed by an increase in the production of sugar, and its appearance in the urine, which, however, is only temporary. SKIN. The Skin, the external investment of the body, is a most complex and important structure, serving (l) as a protective covering ; (2) an organ for tactile sensibility ; (3) an organ for the elimination of excrementitious matters. The Amount of Skin investing the body of a man of average size is 80 HUMAN PHYSIOLOGY. about twenty feet, and varies in thickness, in different situations, from the Y% to the T J^ of an inch. The skin consists of two principal layers, viz., a deeper portion, the Corium, and a superficial portion, the Epidermis. The Corium, or Cutis Vera, may be subdivided into a reticulated and a papillary layer. The former is composed of white fibrous tissue, non- striated muscular fibres and elastic tissize, interwoven in every direction, forming an areolar network, in the meshes of which are deposited masses of fat, and a structureless amorphous matter; the latter is formed mainly of club-shaped elevations or projections of the amorphous matter, constituting the papilla ; they are most abundant, and well developed, upon the palms of the hands and the soles of the feet ; they average the y l^ of an inch in length, and may be simple or compound ; they are well supplied with nerves, blood vessels and lymphatics. The Epidermis or Scarf Skin is an extra-vascular structure, a product of the true skin, and composed of several layers of cells. It may be divided into two layers, the rete mucosum or the Malpighian layer, and the horny or corneous. The former closely applies itself to the papillary layer of the true skin, and is composed of large, nucleated cells, the lowest layer of which, the " prickle cells," contain pigment granules, which give to the skin its varying tints in different individuals and in different races of men ; the more superficial cells are large, colorless, and semi-transparent. The latter, the corneous layer, is composed of flattened cells, which, from their exposure to the atmosphere, are hard and horny in texture ; it varies in thickness from */ of an inch on the palms of the hands and feet, to the F i0 of an inch in the external auditory canal. APPENDAGES OF THE SKIN. Hairs are found in almost all portions of the body, and can be divided into (l) long, soft hairs, on the head; (2) short, stiff hairs, along the edges of the eyelids and nostrils ; (3) soft, downy hairs, on the general cutaneous surface. They consist of a root and a shaft, which is oval in shape, and about the ? l^ of an inch in diameter ; it consists of fibrous tissue, covered externally by a layer of imbricated cells, and internally by cells containing granular and pigment material. The Root of the hair is embedded in the hair follicle, formed by a tubular depression of the skin, extending nearly through to the subcutaneous tissue ; its walls are formed by the layers of the corium, covered by epidermic cells. APPENDAGES OF THE SKIN. 81 At the bottom of the follicle is a papillary projection of amorphous matter, corresponding to a papilla of the true skin, containing blood vessels and nerves, upon which the hair root rests. The investments of the hair roots are formed of epithelial cells, constituting the internal and external root sheaths. The hair protects the head from the heat of the sun and cold, retains the heat of the body, prevents the entrance of foreign matter into the lungs, nose, ears, etc. The color is due to the pigment matter, which, in old age, becomes more or less whitened. The Sebaceous Glands, imbedded in the true skin, are simple and compound racemose glands, opening, by a common excretory duct, upon the surface of the epidermis or into the hair follicle. They are found in all portions of the body, most abundantly in the face, and are formed by a delicate, structureless membrane, lined by flattened polyhedral cells. The sebaceous glands secrete a peculiar oily matter, the sebum, by which the skin is lubricated and the hairs softened ; it is quite abundant in the region of the nose and forehead, which often present a greasy, glistening appear- ance ; it consists of water, mineral salts, fatty globules, and epithelial cells. The Vernix caseosa which frequently covers the surface of the foetus at birth consists of the residue of the sebaceous matters, containing epithelial cells and fatty matters ; it seems to keep the skin soft and supple, and guards it from the effects of the long continued action of water. The Sudoriparous Glands excrete the sweat ; they consist of a mass or coil of a tubular gland duct, situated in the derma and in the subcutane- ous tissue; average the -^ of an inch in diameter, and are surrounded by a rich plexus of capillary blood vessels. From this coil the duct passes in a straight direction up through the skin to the epidermis, where it makes a few spiral turns and opens obliquely upon the surface. The sweat glands consist of a delicate homogeneous membrane lined by epithelial cells, whose function is to extract from the blood the elements existing in the perspiration. The glands are very abundant all over the cutaneous surface, as many as 3528 to the square inch, according to Erasmus Wilson. The Perspiration is an excrementitious fluid, clear, colorless, almost odorless, slightly acid in reaction, with a specific gravity of 1.003 or J-OO4- The total quantity of perspiration excreted daily has been estimated at about two pounds, though the amount varies with the nature of the food and drink, exercise, external temperature, season, etc. The elimination of the sweat is not intermittent, but continuous ; but it 82 HUMAN PHYSIOLOGY. takes place so gradually that as fast as it is formed it passes off by evapora- tion as insensible perspiration. Under exposure to great heat and exercise the evaporation is not sufficiently rapid, and it appears as sensible perspi- ration. COMPOSITION OF SWEAT. Water 995-573 Urea . 0.043 Fatty matters ... 0.014 Alkaline lactates O-3i7 Alkaline sudorates 1.562 Inorganic salts .... 2.491 Urea is a constant ingredient. Carbonic acid is also exhaled from the skin, the amount being about zfa of that from the lungs. Perspiration regulates the temperature, and removes waste matters from the blood ; it is so important, that if elimination be prevented death occurs in a short time. The nervous system influences the secretion of watery vapor by causing a dilatation of the capillary blood vessels around the tubular coil. It is increased by mental emotions ; section of the sympathetic fibres in the neck is followed by a copious perspiration; stimulation of the nerves pro- ducing contraction of the vessels is followed by an arrestation of the elimi nation of the sweat. NERVOUS SYSTEM. 83 NERVOUS SYSTEM. The Nervous System coordinates all the various organs and tissues of the body, and brings the individual into conscious relationship with external nature by means of sensation, motion, language, mental and moral manifestations. The Nervous Tissue may be divided into two systems, the Cerebro- spinal and the Sympathetic. (1) The Cerebro-spinal System occupies the cavities of the cranium and spinal canal, and consists of the brain, the spinal cord, the cranial and spinal nerves. It is the system of animal life, and presides over the func- tions of sensation, motion, etc. (2) The Sympathetic System, situated along each side of the spinal column, consists (i) of a double chain of ganglia, united together by nerve cords, and extends from the base of the cranium to the coccyx ; (2) of various ganglia, situated in the head and face, thorax, abdomen, pelvis, etc. All the ganglia are united together by numerous communicating fibres, many of which anastomose with the fibres of the cerebro- spinal system. It is the nervous system of organic life, and governs the functions of nutrition, growth, etc. Nervous Tissue is composed of two kinds of matter, the gray and white^ which differ in their color, structure and physiological endowments ; the former consists of vesicles or cells which receive and generate nerve force ; the latter consists Q{ fibres which simply conduct it, either from the periphery to the centre or the reverse. Structure of Gray Matter. The gray matter, found on the surface of the brain in the convolutions, in the interior of the spinal cord, and in the various ganglia of the cerebro -spinal and sympathetic nervous systems, consists of a fine connective tissue stroma, the neuroglia, in the meshes of which are embedded the gray cells or vesicles. The cells are grayish in color, and consist of a delicate investing capsule containing a soft, granular, albuminous matter, a nucleus, and sometimes a nudeolus. Some of the cells are spherical or oval in shape, while others have an interrupted outline, on account of having one, two or more pro- cesses issuing from them, constituting the uni-polar, bi-polar or multi-polar nerve cells. Cells vary in size ; the smallest being found in the brain, the 84 HUMAN PHYSIOLOGY. largest in the anterior horns of gray matter of the spinal cord. Some of the cell processes become continuous with the fibres of the white matter, while others anastomose with those of adjoining cells and form a plexus. Structure of the White Matter. The white matter, found for the most part in the interior of the brain, on the surface of the spinal cord, and in almost all the nerves of the cerebro- spinal and sympathetic systems, consists of minute tubules or fibres, the ultimate nerve filaments, which in the perfectly fresh condition, are apparently structureless and homogeneous ; but when carefully examined after death are seen to consist of three distinct portions, (i) a tubular membrane; (2) the white substance of Schwann; (3) the axis cylinder. The Tubular membrane, investing the nerve filament, is thin, homoge- neous, and lined by large, oval nuclei, and presents, in its course, annular constrictions; it serves to keep the internal parts of the fibre in position, and protects them from injury. The White substance of Schwann, or the medullary layer, is situated immediately within the tubular membrane, and gives to the nerves their peculiar white and glistening appearance. It is composed of oleaginous matter in a more or less fluid condition; after death it undergoes coagula- tion, giving to the fibre a knotted or varicose appearance. It serves to insulate the axis cylinder, and prevents the diffusion of the nerve force. The Axis cylinder occupies the centre of the medullary substance. In the natural condition it is transparent and invisible, but when treated with proper reagents, it presents itself as a pale, granular, flattened band, albu- minous in character, more or less solid, and somewhat elastic. It is com- posed of a number of minute fibrillae united together to form a single bundle. (Schultze.) Nerve fibres in which these three structural elements coexist are known as the medtillated nerve fibres. In the sympathetic system, and in the gray substance of the cerebro- spinal system, many nerves are destitute of a me- dullary layer, and are known as the non-medullated nerve fibres. Gray or Gelatinous nerve fibres, found principally in the sympathetic system, are gray in color, semi-transparent, flattened, with distinct borders, finely granular, and present oval nuclei. The diameter of the gelatinous fibres is about the-g^ 1 ^ of an inch; of the medullated fibres from ^^Q- to T ^Q^ of an inch. Ganglia are small bodies, varying considerably in size, situated on the posterior roots of spinal nerves, on the sensory cranial nerves, alongside of the vertebral column, forming a connecting chain, and in the different vis- SPINAL NERVES. 85 cera. They consist of a dense, investing, fibrous membrane, containing in its interior gray or vesicular cells, among which are found white and gela- tinous nerve fibres. They may be regarded as independent nerve centres. Structures of Nerves. Nerves are rounded or flattened cords extend- ing from the centres to the periphery ; they are surrounded externally by a sheath, the neurilemma, composed of fibrous and elastic tissue forming a stroma, in which blood vessels ramify, from which the nerves derive their nourishment. A Nerve consists of a greater or less number of ultimate nerve filaments ', separated into bundles by fibrous septa given off from the neurilemma. The nerve filaments pursue an uninterrupted course, from their origin to their termination; branches pass from one nerve trunk into the sheath of another, but there is no anastomosis or coalescence with adjoining nerve fibres. A Plexus is formed by a number of branches of different nerves inter- lacing in every direction, in the most intricate manner, but from which fibres are again given off to pursue their independent course, e.g., brachial, cervical, lumbar, sacral, cardiac plexuses, etc. SPINAL NERVES. Origin. The spinal nerves are thirty-one in number on each side of the spinal cord, and arise by two roots, an anterior and posterior, from the anterior and posterior aspects of the cord respectively : the posterior roots present near their emergence from the cord a small ganglionic enlargement ; outside of the spinal canal the two roots unite to form a main trunk, which is ultimately distributed to the skin, muscles and viscera. The Function of the Anterior Roots is to transmit motor impulses from the centres outward to the periphery. Irritation of these roots, from whatever cause, excites convulsive movements in the muscles to which they are distributed ; disease or division of these roots induces a condition of paresis or paralysis. - The Function of the Posterior Roots is to transmit the impressions made upon the periphery to the centres in the spinal cord, where they excite motor impulses ; or to the brain, in which they are translated into conscious sensations. Irritation of these roots gives rise to painful sensa- tions ; division of the roots abolishes all sensation in the parts to which they are distributed. The ganglion on the posterior root influences the nutrition of the sensory 86 HUMAN PHYSIOLOGY. nerve; for if the nerve be separated from the ganglion, it undergoes degene- ration in the course of a few days, in the direction in which it carries impressions, i. e., from the periphery to the centres; if the nerve be divided between the ganglion and the cord, the central end only undergoes degene- ration. The nutrition of the anterior root is governed by nerve cells in the gray matter of the cord ; for if these cells undergo atrophy, or if the nerve be divided, it undergoes degeneration outward. Nerve Terminations. (l) Central. Both motor and sensory nerve fibres, as they enter the spinal cord and brain, lose their external invest- ments, and retaining only the axis cylinder, ultimately become connected with the processes of the gray cells. (2) Peripheral. As the nerves approach the tissues to which they are to be distributed, they inosculate freely, forming a plexus from which the ultimate fibres proceed to individual tissues. Motor Nerves. In the voluntary or striped muscles the motor nerves are connected with the contractile substance by means of the " motorial end plates ; " when the nerve enters the muscular fibre the tubular mem- brane blends with the sarcolemma, the medullary layer disappears, and the axis cylinder spreads out into the form of a little plate, granular in character, and containing oval nuclei. In the unstriped or involuntary muscles, the terminal nerve fibres form a plexus on the muscular fibre cells, and become connected with the granular contents of the nuclei. In the glands nerve fibres have been traced to the glandular cells, where they form a branching plexus from which fibres pass into their interior and become connected with their substance, and thus influence secretion. Sensitive Nerves terminate in the skin and mucous membranes, in three distinct modes, e. g. t as tactile corpuscles, Pacinian corpuscles, and as end bulbs. The tactile corpuscles are found in the papillae of the true skin, especially on the palmar surface of the hands and fingers, feet and toes ; they are oblong bodies, measuring about -$fa of an inch in length, consisting of a central bulb of homogeneous connective tissue surrounded by elastic fibres and elongated nuclei. The nerve fibre approaches the base of the corpuscle, makes two or three spiral turns around it, and terminates in loops. They are connected with the sense of touch. The Pacinian corpuscles are found chiefly in the subcutaneous cellular tissue, on the nerves of the hands and feet, the intercostal nerves, the cutaneous nerves, and in many other situations. They are oval in shape, PROPERTIES AND FUNCTIONS OF NERVES. 87 measure about the T ^ of an inch in length on the average, and consist of concentric layers of connective tissue; the nerve fibre penetrates the cor- puscle and terminates in a rounded knob in the central bulb. Their function is Unknown. The end bulbs of Krause are formed of a capsule of connective tissue in which the nerve fibre terminates in a coiled mass or bulbous extremity ; they exist in the conjunctiva, tongue, glans penis, clitoris, etc. Many sensitive nerves terminate in the papillae at the base of the hair follicle ; but in the skin, mucous membranes, and organs of special sense their mode of termination is not well understood. PROPERTIES AND FUNCTIONS OF NERVES. Classification. Nerves may be divided into two groups, viz. : (1) Afferent or centripetal, as when they convey to the nerve centres the impressions which are made upon their peripheral extremities or parts of their course. They may be sensitive, when they transmit impressions which give rise to sensations ; reflective or excitant ', when the impression carried to the nerve centre is reflected outward by an efferent nerve and produces motion or some other effect in the part to which the nerve is distributed. (2) Efferent or centrifugal, as when the impulses generated in the centres are transmitted outward to the muscles and various organs. They may be motor, as when they convey impulses to the voluntary and invol- untary muscles ; vasomotor, when they regulate the calibre of the small blood vessels, increasing or diminishing the amount of blood to a part ; secretory, when they influence secretion; trophic, when they influence nutrition ; inhibitory, when they conduct impulses which produce a re- straining or inhibiting action. Stimuli of Nerves. Nerves respond to stimulation according to their habitual function ; thus, stimulation of a sensory nerve, if sufficiently strong, results in the sensation of pain; of the optic nerve, in the sensation of light; of a motor nerve, in contraction of the muscle to which it is distributed; of a secretory nerve, in the activity of the related gland, etc. It is, therefore, evident that peculiarity of nervous function depends neither upon any special construction or activity of the nerve itself, nor upon the nature of the stimulus, but entirely upon the peculiarities of its central and peripheral end organs. Nerves react to the following kinds of stimuli : 1. Mechanical : as from a blow, pressure, tension, puncture, etc. 2. Thermal: heating a nerve at first increases and then decreases its excita- bility. 88 HUMAN PHYSIOLOGY. 3. Chemical : Sensory nerves respond somewhat less promptly than motor nerves to this form of irritation. 4. Electrical : Either the constant or interrupted current. 5. The normal physiological stimulus : (a) Centrifugal or efferent if proceeding from the centre toward the periphery. (b) Centripetal or afferent if in the reverse direction. (c) Reflex, a combination of the two preceding. The Axis Cylinder is the essential conducting agent, the white substance of Schwann and tubular membrane being probably accessory structures, protecting the axis from injury, and preventing the diffusion of nerve force to adjoining nerves. The properties of sensation and motion reside in different nerve fibres. Motor nerves can be destroyed or paralyzed by the introduction of woorara under the skin, without affecting sensation; the sensibility of nerves can be abolished by the employment of anaesthetics without destroying motion. Irritability. Nerves conduct peripheral impressions to the centres, and motor impulses to the periphery, in virtue of their possessing an ultimate and inherent property, denominated neurility, nervous irritability ', or excitability, which is manifested as long as the physical and chemical integrity of the nerve is maintained. Nerve Degeneration. When nerves are separated from their trophic or nutritive centres, they degenerate progressively in the direction in which they conduct impressions. In motor nerves, from the centre to the pe- riphery ; in sensory nerves, from the periphery to the centres. Nerve force is not identical with electricity. Nerves do not possess the power of generating force, or of originating impulses within themselves, but propagate only the nervous impulses which are called forth by chemical, physical and mechanical stimuli from without, and by volitional acts, normal and pathological conditions from within. Velocity of Nerve Force. This is slightly modified by temperature, cold lessening the rapidity, heat increasing it ; it is also modified by electrical conditions, by the action of drugs and by the strength of the stimulus. The average velocity for human sensory nerves has been estimated at about 190 feet per second, and for motor nerves 100 to 120 feet per second. Phenomena of Muscles and Nerves. The muscles are the motor organs of the body and constitute a large per cent, of the body weight. Muscles are of two kinds, striated and non-striated or involuntary. The striated muscles consist of bundles of fibres, the fasciculi, held together by connective tissue. Each muscle fibre is about ]/% to \y z inches long, and PROPERTIES AND FUNCTIONS OF NERVES. 89 possesses a delicate homogeneous membrane, the sarcolemma, in the inte- rior of which is contained the contractile substance, which presents a striated appearance. During life this substance is in a fluid condition, but after death undergoes stiffening. The non-striated muscles form membranes which surround cavities, e.g., stomach, arteries, bladder, etc. They are composed of elongated cells without striations, and contain in their interior one or more nuclei. Muscular tissue is composed of water, an organic contractile substance, myosin, non-nitrogenized substances, such as glycogen, inosite, fat, and inorganic salts. When at rest the muscle is alkaline in reaction, but during and after contraction it becomes acid. Muscles possess the properties of (i) Contractility, which is the capa- bility of shortening themselves in the direction of their long axis, and at the same time becoming thicker and more rigid. (2) Extensibility, by means of which they are -lengthened in proportion to weights attached. (3) Elasticity, in virtue of which they return to their original shape when the force applied is removed. The contractility of muscles is called forth mainly by nervous impulses, descending motor nerves, which originate in the central nervous system ; but it can also be excited by the electric current, the application of strong acids, heat, or by mechanical means. Phenomena of a Muscular Contraction. When a single induction shock is propagated through a nerve, the muscle to which it is distributed undergoes a quick pulsation, and speedily returns to its former condition. As is shown by the muscle curve, the contraction, which is at first slow, increases in rapidity to its maximum, gradually relaxes and is again at rest, the entire pulsation not occupying more than the ^ of a second. The muscular contraction does not instantly follow the induction shock, even when the electrodes are placed directly upon the muscular fibres themselves ; an appreciable period intervenes before the contraction, during which certain chemical changes are taking place preparatory to the mani- festation of force. This is the " latent period," which has an average dura- tion of the T ^ 7 of a second, but varies with the temperature, the strength of the stimulus, the animal, etc. The muscular movements of the body, how- ever, are occasioned by contractions of a much longer duration, depending upon the number (the average, 20) of nervous impulses passing to the muscles in a second. During the muscular contraction the following phenomena are observed, viz. : a change in form, a rise in temperature, a consumption of oxygen and an evolution of carbonic acid ; the production of a distinct musical sound, 90 HUMAN PHYSIOLOGY. a change from an alkaline to an acid reaction, from the development of sarcolactic acid ; a disappearance of the natural muscle currents, which undergo a negative variation in the "latent period," just after the nervous impulse reaches the termination of the nerve, and before the appearance of the muscular contraction wave. Electrical Properties of Nerves. When a galvanic current is made to flow along a motor nerve from the centre to the periphery, from the positive to the negative pole, it is known as the direct, descending or centri- fugal current. When it is made to flow in the reverse direction it is known as the inverse, ascending or centripetal current. The passage of a direct current enfeebles the excitability of a nerve ; the passage of the inverse current increases it. The excitability of a nerve may be exhausted by the repeated applications of electricity ; when thus exhausted it may be restored by repose, or by the passage of the inverse current if the nerve has been exhausted by the direct current or vice versa. During the actual passage of a feeble constant current in either direction neither pain nor muscular contraction is ordinarily manifested; if the cur- rent be very intense the nerve may be disorganized and its excitability destroyed. Electrotonus. The passage of a direct galvanic current through a por- tion of a nerve excites in the parts beyond the electrodes a condition of electric tension or electrotonus, during which the excitability of the nerve is decreased near the anode or positive pole, and increased near the kathode or negative pole ; the increase of excitability in the kathelectrotonic area, that nearest the muscle, being manifested by a more marked contraction of the muscle than the normal, when the nerve is irritated in this region. The passage of an inverse galvanic current excites the same condition of electrotonus ; and the diminution of excitability near the anode, the anelec- trotonic area, that now nearest the muscle, being manifested by a less marked contraction than the normal when the nerve is stimulated in this region. Between the electrodes is a neutral point where the kathelectro- tonic area emerges into the anelectrotonic area. If the current be a strong one, the neutral point approaches the kathode ; if weak, it approaches the anode. When a nervous impulse passes along a nerve, the only appreciable effect is a change in its electrical condition, there being no change in its temperature, chemical composition or physical condition. The natural nerve currents, which are always present in a living nerve as a result of its nutritive activity, in great part disappear during the passage of an impulse, undergoing a negative variation. CRANIAL NERVES. 91 Law of Contraction. If a feeble galvanic current be applied to a recent and excitable nerve, contraction is produced in the muscles only upon the making of the circuit with both the direct and inverse currents. If the current be moderate in intensity, the contraction is produced in the muscle both upon the making and breaking of the circuit, with both the direct and inverse currents. If the current be intense, contraction is produced only when the circuit is made with the direct current, and only when it is broken with the inverse current. The Reaction of Degeneration. Two different applications of elec- tricity are used in electro-physiology and electro-therapeutics the constant or galvanic, and the interrupted or faradic currents. Injured and paralyzed muscles and nerves react differently to these two kinds of stimuli, and the facts are of the greatest importance in the diagnosis and therapeutics of the precedent lesions. The principal difference of behavior relates to the reaction of degeneration a condition produced by paralysis of any kind. It is characterized by a diminished or abolished excitability of the muscles to the faradic current, while there is at the same time an increased excitability to the galvanic current. The synchronous diminished excita- bility of the nerves is the same for either current. The term partial reac- tion of degeneration is used when there is a normal reaction of the nerves, but the muscles show the degenerative reaction. This condition is a characteristic of progressive muscular atrophy. CRANIAL NERVES. The Cranial Nerves come off from the base of the brain, pass through the foramina in the walls of the cranium, and are distributed to the skin, muscles and organs of sense in the face and head. According to the classification of Soemmering, there are 12 pairs of nerves, enumerating them from before backward, as follows, viz. : ist Pair, or Olfactory. 7th Pair, or Facial, Portio dura. 2d Pair, or Optic. 8th Pair, or Auditory, Portio mollis. 3d Pair, or Motor oculi communis. Qth Pair, or Glosso-pharyngeal. 4th Pair, or Patheticus, Trochlearis. loth Pair, or Pneumogastric. 5th Pair, or Trifacial, Trigeminus. nth Pair, or Spinal accessory. 6th Pair, or Abducens. I2th Pair, or Hypoglossal. The Cranial Nerves may also be classified physiologically, according to their function, into three groups : I . Nerves of special sense. 2. Nerves of motion. 3. Nerves of general sensibility. 92 HUMAN PHYSIOLOGY. ist Pair. Olfactory. Apparent Origin. From the inferior and internal portion of the ante- rior lobes of the cerebrum by three roots, viz. : an external white root, which passes across the fissure of Sylvius to the middle lobe of the cere- brum ; an internal white root, from the most posterior part of the anterior lobe ; a gray root, from the gray matter in the posterior and inner portion of the inferior surface of the anterior lobe. Deep Origin. Not satisfactorily determined. Distribution. The olfactory nerve, formed by the union of the three roots, passes forward along the under surface of the anterior lobe to the ethmoid bone, where it expands into the olfactory bulb. This bulb con- tains ganglionic cells, is grayish in color and soft in consistence ; it gives off from its under surface from fifteen to twenty nerve filaments, the true olfactory nerves, which pass through the cribriform plate of the ethmoid bone, and are distributed to the schneiderian mucous membrane. This membrane extends from the cribriform plate of the ethmoid bone down- ward, about one inch. Properties. The olfactory nerves give rise to neither motor nor sensory phenomena when stimulated. They carry simply the special impressions of odorous substances. Destruction or injury of the olfactory bulbs is attended by a loss of the sense of smell. Function. Governs the sense of smell. Conducts the impressions which give rise to odorous sensations. 2d Pair. Optic. Apparent Origin. From the anterior portion of the optic commissure. Deep Origin. The origins and connections of the optic tract are very complex. The immediate origins are bands of fibres from the thalamus opticus and anterior corpora quadrigemina. The corpora geniculata are interposed ganglia. The ultimate roots are traced 1. By abroad band of fibres "the optic radiation of Gratiolet " to the psycho-optic centres in the occipital lobes. 2. To the gyrus hippocampi and sphenoidal lobes. 3. Through the corpus callosum to the motor areas of the opposite cere- bral hemispheres. 4. To the frontal region by " Meynert's Commissure." 5. To the spinal cord. 6. To the corpora geniculata, pulvinar, and anterior corpora geniculata by ganglionic roots. CRANIAL NERVES. 93 Distribution. The two roots unite to form a flattened band, the optic tract, which winds around the crus cerebri to decussate with the nerve of the opposite side, forming the optic chiasm. The decussation of fibres is not complete ; some of the fibres of the left optic tract going to the outer half of the eye of the same side, and to the inner half of the eye of the opposite side ; the same holds true for the right optic tract. The optic nerves proper arise from the commissure, pass forward through the optic foramina, and are finally distributed in the retina. Properties. They are insensible to ordinary impressions, and convey only the special impressions of light. Division of one of the nerves is attended by complete blindness in the eye of the corresponding side ; division of the optic tract produces loss of sight in the outer half of the eye of the same side, and in the inner half of the eye of the opposite side. Lesion of the anterior part of the optic chiasm causes blindness in the inner half of the two eyes. Functions. Governs the sense of sight. Receives and conveys to the brain the luminous impressions which give rise to the sensation of sight. The reflex movements of the iris are called forth by the optic nerve. When an excess of light falls upon the retina the impression is carried back to the tubercula quadrigemina, where it is transformed into a motor impulse, which then passes outward through the motor oculi nerve to the contractile fibres of the iris and diminishes the size of the pupil. The absence of light is followed by a dilatation of the pupil. 3d Pair. Motor Oculi Communis. Apparent Origin. From the inner surface of the crura cerebri. Deep Origin. By filaments coming from the lenticular nucleus, corpora quadrigemina, optic thalamus; these filaments converge to form a main trunk, which winds around the crus cerebri, in front of the pons Varolii. Distribution. The nerve then passes forward, and enters the orbit through the sphenoidal fissure, where it divides into a superior branch distributed to the superior rectus and lev at or palp ebr a muscles; an inferior branch sending branches to the internal 'and inferior recti, and the inferior oblique muscles ; filaments also pass into the ciliary or ophthalmic ganglion ; from this ganglion the ciliary nerves arise which enter the eyeball, and are distributed to the circular fibres of the iris and the ciliary muscle. The 3d nerve also receives filaments from the cavernous plexus of the sympa- thetic and from the fifth nerve. Properties. Irritation of the root of the nerve produces contraction 94 HUMAN PHYSIOLOGY. of the pupil, internal strabismus, muscular movements of eye, but no pain. Division of the nerve is followed by ptosis (falling of the upper eyelid), external strabismus, due to the unopposed action of the external rectus muscle ; paralysis of the accommodation of the eye ; dilatation of the pupil from paralysis of the circular fibres of the iris and ciliary muscle; and inability to rotate the eye, slight protrusion ^and double vision. The images are crossed; that of the paralyzed eye is a little above that of the sound, and its upper end inclined toward it. Function. Governs movements of the eyeball by animating all the muscles except the external rectus and superior oblique, the movements of the iris, elevates the upper lid, influences the accommodation of the eye for distances. Can be called into action by ( I ) voluntary stimuli, ( 2 ) by reflex action through irritation of the optic nerve. 4th Pair. Patheticus. Apparent Origin. From the superior peduncles of the cerebellum. Deep Origin. By fibres terminating in the corpora quadrigemina, lenticular nucleus, valve of Vieussens, and in the substance of the cere- bellar peduncles; some filaments pass over the median line and decussate with fibres of the opposite side. Distribution. The nerve enters the orbital cavity through the sphe- noidal fissure, and is distributed to the superior oblique muscle ; in its course receives filaments from the ophthalmic branch of the 5th pair and the sympathetic. Properties. When the nerve is irritated muscular movements are pro- duced in the superior oblique muscle, and the pupil of the eye is turned downward and outward. Division or paralysis lessens the movements and rotation of the globe downward and outward. The diplopia conse- quent upon this paralysis is homonymous, one image appearing above the other. The image of the paralyzed eye is below, its upper end inclined toward that of the sound eye. Function. Governs the movements of the eyeball produced by the action of the superior oblique muscles. 6th Pair.* Abducens. Motor Oculi Externus. Apparent Origin. From the groove between the anterior pyramidal body and the pons Varolii, where it arises by two roots. * The 6th nerve is considered in connection with the 3d and 4th nerves, since they together constitute the motor apparatus by which the ocular muscles are excited to action. CRANIAL NERVES. 95 Deep Origin. From the gray matter of the medulla oblongata. Distribution. The nerve then passes into the orbit through the sphe- noidal fissure, and is distributed to the external rectus muscle. Receives filaments from the cervical portion of the sympathetic, through the carotid plexus and spheno-palatine ganglion. Properties. When irritated, the external rectus muscle is thrown into convulsive movements, and the eyeball is turned outward. When divided or paralyzed, this muscle is paralyzed ; motion of the eyeball outward past the median line is impossible, and the homonymous diplopia increases as the object is moved outward past this line. The images are upon the same plane and parallel. Internal strabismus results because of the unopposed action of the internal rectus. Function. To turn the eyeball outward. 5th Pair. Trifacial. Trigeminal. Apparent Origin. By two roots from the side of the pons Varolii. Deep Origin. The deep origin of the two roots is the upper part of the floor and anterior wall of the 4th ventricle, by three bundles of fila- ments, one of which anastomoses with the auditory nerve ; another passes to the lateral tract of the medulla ; while a third, grayish in color, goes to the restiform bodies, and may be traced to the point of the calamus scrip- torius. Filaments of origin have been traced to the "trigeminal sensory nucleus," located on a level with the point of exit of the nerve, and to the posterior gray horns of the cord, as low down as the middle of the neck. Distribution. The large root of the nerve passes obliquely upward and forward to the ganglion of Gasser, which receives filaments of com- munication from the carotid plexus of the sympathetic. It then divides into three branches. 1. Ophthalmic branch, which receives communicating filaments from the sympathetic, and sends sensitive fibres to all the motor nerves of the eyeball. It is distributed to the ciliary ganglion, lachrymal gland, sac and caruncle, conjunctiva, integument of the upper eyelid, forehead, side of head and nose, anterior portion of the scalp, ciliary muscle and iris. 2. Superior maxillary branch, sends branches to the spheno-palatine ganglion, integument of the temple and lower eyelid, side of forehead, nose, cheek and upper lip, teeth of the upper jaw, and alveolar processes. 3. Inferior maxillary branch, which, after receiving in its course fila- ments from the small root and from the facial, is distributed to the sub- 96 HUMAN PHYSIOLOGY. maxillary ganglion, the parotid and sub-lingual glands, external auditory meatus, mucous membrane of the month, anterior two-thirds of the tongue (lingual branch), gums, arches of the palate, teeth of the lower jaw, and integument of the lower part of the face, and t the muscles of mastication. The small root passes forward beneath the ganglion of Gasser, through the foramen ovale, and joins the inferior maxillary division of the large root, which then divides into an anterior and posterior branch, the former of which is distributed to the musdes of mastication, viz. : temporal, mas- seter, internal and external pterygoid muscles. Properties. It is the most acutely sensitive nerve in the body, and endows all the parts to which it is distributed with general sensibility. Irritation of the large root, or any of its branches, will give rise to marked evidence of pain ; the various forms of neuralgia of the head and face being occasioned by compression, disease, or exposure of some of its terminal branches. Division of the large root within the cranium is followed at once by a complete abolition of all sensibility in the head and face, but is not attended by any loss of Hiotioa. The integument, mucous membranes and the eye may be lacerated, cut or bruise d r without the animal exhibiting any evidence of pain. At the same time the lachrymal secretion is diminished, the pupil becomes contracted, the eyeball is protruded, and the sensibility of the tongue is abolished. The reflex movements of deglutition are also somewhat impaired ; the impression of the food being unable to reach and excite the nerve centre in the medulla oblongata. Galvanization of the small root produces movements of the muscles of mastication ; section of the root causes paralysis of these muscles, and the jaw is drawn to the opposite side, by the action of the opposing muscles. Influence upon the Special Senses. After division of the large root within the cranium, a disturbance in the nutrition of the special senses sooner or later manifests itself. Sight. In the course of twenty-four hours the eye becomes very vascular and inflamed, the cornea becomes opaque and ulcerates, the humors are dis- charged, and the eye is totally destroyed. Smell. The nasal mucous membrane swells up, becomes fungous, and is liable to bleed on the slightest irritation. The mucus is increased in amount, so as to obstruct the nasal passages; the sense of smell is finally abolished. CRANIAL NERVES. 97 Hearing. At times the hearing is impaired, from disorders of nutrition in the middle ear and external auditory meatus. Alteration in the nutrition of the special senses is not marked if the sec- tion is made posterior to the ganglion of Gasser, and to the anastomosing filaments of the sympathetic which join the nerve at this point ; but if the ganglion be divided, these effects are very noticeable, due to the section of the sympathetic filaments. Function. Gives sensibility to all parts of the head and face to which it is distributed ; through the small root endows the masticatory muscles with motion ; through fibres from the sympathetic governs the nutrition of the special senses. 7th Pair. Portio Dura. Facial Nerve. Apparent Origin. From the groove between the olivary and restiform bodies at the lateral portion of the medulla oblongata, and below the mar- gin of the pons Varolii. Deep Origin. From a nucleus of large cells in the floor of the 4th ventri- cle, below the nucleus of origin of the 6th pair, with which it is connected. Some filaments are traceable to the lenticular nucleus of the opposite side. Some of the fibres cross the median line and decussate. It is intimately associated with the nerve of Wrisberg at its origin. Distribution. From its origin the facial nerve passes into the internal auditory meatus, and then, in company with the nerve of Wrisberg, enters the aqueduct of Fallopius. The filaments of the nerve of Wrisberg are supplied with a ganglion, of a reddish color, having nerve cells. These filaments unite with those of the root of the facial, to form a common trunk, which emerges at the stylo-mastoid foramen. In the aqueduct the facial gives off the following branches, viz.: 1. Large petrosal nerve, which passes forward to the spheno-palatine, or Meckel's ganglion, and through this to the levator palati and azygos uvulae muscles, which receive motor influence from this source. 2. Small petrosal nerve, passing to the otic ganglion and thence to the tensor-tympani muscle, endowing it with motion. 3. Tympanic branch, giving motion to the stapedius muscle. 4. Chorda tympani nerve, which after entering the posterior part of the tympanic cavity, passes forward between the malleus and incus bones, through the Glasserian fissure, and joins the lingual branch of the 5th nerve. It is then distributed to the mucous membrane of the anterior two-thirds of the tongue and the sub-maxillary glands. 98 HUMAN PHYSIOLOGY. After emerging from the stylo-mastoid foramen, the facial nerve sends branches to the muscles of the ear, the occipito-frontalis, the digastric, the palato-glossi, and palato-pharyngei ; after which it passes through the parotid gland and divides into the temporo-fadal 'and cervico-facial branches, which are distributed to the superficial muscles of the face, viz. : occipito- frontalis, corrugator supercilii, orbicularis palpebrarum, levator labii superio- ris et alseque nasi, buccinator, levator anguli oris, orbicularis oris, zygoma- tici, depressor anguli oris, platysma myoides, etc. Properties. Undoubtedly a motor nerve at its origin, but in its course receives sensitive filaments from the 5th pair and the pneumogastric. Irritation of the nerve, after its emergence from the stylo-mastoid fora- men, produces convulsive movements in all the superficial muscles of the face. Division of the nerve at this point causes paralysis of these muscles on the side of the section, constituting facial paralysis ; the phenomena of which are, a relaxed and immobile condition of the same side of the face ; the eyelids remain open, from paralysis of the orbicularis palpebrarum ; the act of winking is abolished ; the angle of the mouth droops, and saliva constantly drains away ; the face is drawn over to the sound side ; the face becomes distorted upon talking or laughing ; mastication is interfered with, the food accumulating between the gums and cheek, from paralysis of the buccinator muscle ; fluids escape from the mouth in drinking ; articulation is impaired, the labial sounds being imperfectly pronounced. Properties of the branches given off in the aqueduct of Fallopius. The Large petrosal, when irritated, throws the levator palati and azygos uvulce muscles into contraction. Paralysis of this nerve, from deep-seated lesions, produces a deviation of the uvula to the sound side, a drooping of the palate, and an inability to elevate it. The Small petrosal influences hearing by animating the tensor tympani muscle ; when paralyzed, there occurs partial deafness and an increased sensibility to sonorous impressions. The Tympanic branch animates the stapedius muscle, and influences audition. The Chorda tympani influences the circulation and the secretion of saliva, in the sub-maxillary glands, and governs the sense of taste in the anterior two-thirds of the tongue. Galvanization of the chorda tympani dilates the blood vessels, increases the quantity aAd rapidity of the stream of blood, and increases the secretion of saliva. Division of the nerve is followed by contraction of the vessels, an arrestation of the secretion, and a diminution of the sense of taste, on the same side. Function. The facial is the nerve of expression, and coordinates the CRANIAL NERVES. 99 muscles employed to delineate the various emotions, influences the sense of taste, deglutition, movements of the uvula and soft palate, the tension of the membrana tympani, and the secretions of the sub-maxillary and parotid glands. Indirectly influences smell, hearing and vision. 8th Pair. Portio Mollis. Auditory Nerve. Apparent Origin. From the upper and lateral portion of the medulla oblongatajust below the margin of the pons Varolii. Deep Origin. By two roots from the floor of the 4th ventricle, each root consisting of a number of gray filaments, some of which decussate in the median line; the external root has a gangliform enlargement contain- ing fusiform nerve cells. Distribution. The two roots wind around the restiform bodies and enter the internal auditory meatus, and divide into an anterior branch distributed to the cochlea, and a posterior branch distributed to the vesti- bule and semicircular canals. Properties. They are soft in consistence, grayish in color, consisting of axis cylinders with a medullary sheath only; they are not sensible to ordinary impressions, but convey the impression of sound. Function. Governs the sense of hearing. Receives and conducts to the brain the impression of sound, which gives rise to the sensations of hearing. gth Pair. Glosso-pharyngeal. Apparent Origin. Partly from the medulla oblongata and the inferior peduncles of the cerebellum. Deep Origin. From the lower portion of the gray substance in the floor of the 4th ventricle. This nerve has two ganglia ; the jugular ganglion includes only a por- tion of the root filaments ; the ganglion of Andersch includes all the fibres of the trunk. Distribution. The trunk of the nerve passes downward and forward, receiving near the ganglion of Andersch fibres from the facial and pneu- mogastric nerves. It divides into two large branches, one of which is distributed to the base of the tongue, the other to the pharynx. In its course it sends filaments to the otic ganglion ; a tympanic branch which gives sensibility to the mucous membrane of the fenestra rotunda, fenestra ovalis, and Eustachian tube ; lingual branches to the base of the tongue ; palatal branches to the soft palate, uvula and tonsils ; pharyngeal branches to the mucous rrNembfaue of tfae pharynx. 100 HUMAN PHYSIOLOGY. Properties. Irritation of the roots at their origin calls forth evidences of pain ; it is, therefore, a sensory nerve, but its sensibility is not so acute as that of the trifacial. Irritation of the trunk after its exit from the cranium produces contraction of the muscles of the palate and pharynx, due to the presence of anastomosing motor fibres. Division of the nerve abolishes sensibility in the structures to which it is distributed, and impairs the sense of taste in the posterior third of the tongue (see Sense of Taste). Function. Governs sensibility of pharynx, presides partly over the sense of taste, and controls reflex movements of deglutition and vomiting. loth Pair. Pneumogastric. Par Vagum Apparent Origin. From the lateral side of the medulla oblongata, just behind the olivary body. Deep Origin. In the gray nuclei in the lower half of the floor of the 4th ventricle, and in the substance of the restiform body. Some' filaments are traced along the restiform tract, toward the cerebellum, and others to the median line of the floor of the 4th ventricle, where many of them decussate. This nerve has two ganglia ; one in the jugular foramen, called the gan- glion of the root, and another outside of the cranial cavity on the trunk, the ganglion of the trunk. Distribution. The filaments from the root unite to form a single trunk, which leaves the cavity of the cranium, through the jugular foramen, in company with the spinal accessory and glosso-pharyngeal. It soon receives an anastomotic branch from the spinal accessory, and afterward branches from the facial, the hypoglossal and the anterior branches of the two upper cervical nerves. As the nerve passes down the neck it sends off the following main branches : 1. Pharyngeal nerves, which assist in forming the pharyngeal plexus, which is distributed to the mucous membrane and muscles of the pharynx. 2. Superior laryngeal nerve, which enters the larynx through the thyro- hyoid membrane, and is distributed to the mucous membrane lining the interior of the larynx, and to the crico-thyroid muscle and the inferior con- strictor of the pharynx. The " depressor nerve" found in the rabbit, is formed by the union of two branches, one from the superior laryngeal, the other from the main trunk; it passes downward to be distributed to the heart. r < - , - - - : f CRANIAL NERVES. 101 3. Inferior laryngeal, which sends its ultimate branches to all the in- trinsic muscles ol the larynx except the crico-thyroid, and to the inferior constrictor of the pharnyx. 4. Cardiac branches given off from the nerve throughout its course, which unite with the sympathetic fibres to form the cardiac plexus, to be distributed to the heart. 5. Pulmonary branches, which form a plexus of nerves and are dis- tributed to the bronchi and their ultimate terminations, the lobules and air cells. From the right pneumogastric nerve branches are distributed to the mucous membrane and muscular coats of the stomach and intestines, to the liver, spleen, kidneys, and supra-renal capsules. Properties. At its origin the pneumogastric nerve is sensory, as shown by direct irritation or galvanization, though its sensibility is not very marked. In its course exhibits motor properties, from anastomosis with motor nerves. The Pharyngeal branches assist in giving sensibility to the mucous mem- brane of the pharynx, and influence reflex phenomena of deglutition through motor fibres which they contain, derived from the spinal accessory. The Superior laryngeal nerve endows the upper portion of the larynx with sensibility; protects it from the entrance of foreign bodies ; by con- ducting impressions to the medulla, excites the reflex movements of deglu- tition and respiration; through the motor filaments it contains produces contraction of the crico-thyroid muscle. Division of the " Depressor nerve" and galvanization of the central end, retards and even arrests the pulsations of the heart, and by depressing the vasomotor centre diminishes the pressure of blood in the large vessels, by causing dilatation of the intestinal vessels through the splanchnic nerves. The Inferior laryngeal contains, for the most part, motor fibres from the spinal accessory. When irritated, produces movement in the laryn- geal muscles. When divided, is followed by paralysis of these muscles, except the crico-thyroid, impairment of phonation, and an embarrassment of the respiratory movements of the larynx, and finally death, from suffo- cation. The Cardiac branches, through filaments derived from the spinal acces- sory, exert a direct inhibitory action upon the heart. Division of the pneumogastrics in the neck increases the frequency of the heart's action. Galvanization of the peripheral ends diminishes the heart's pulsation, and, if sufficiently powerful, paralyzes it in diastole. 102 HUMAN PHYSIOLOGY. The Pulmonary branches give sensibility to the bronchial mucous mem- brane, and govern the movements of respiration. Division of both pneu- mogastrics in the neck diminishes the frequency of the respiratory move- ments, falling as low as four to six per minute ; death usually occurs in from five to eight days. Feeble galvanization of the central ends of the divided nerves accelerates respiration ; powerful galvanization retards, and may even arrest the respiratory movements. The Gastric branches give sensibility to the mucous coat, and through sympathetic filaments, which join the pneumogastrics high up in the neck, give motion to the muscular coat of the stomach. They influence the secretion of gastric juice, aid the process of digestion and absorption from the stomach. The Hepatic branches, probably through anastomosing sympathetic fila- ments, influence the secretion of bile, and the glycogenic function of the liver ; division of the pneumogastrics in the neck produces congestion of the liver, diminishes the density of the bile, and arrests the glycogenic function ; galvanization of the central ends exaggerates the glycogenic function, and makes the animal diabetic. The Intestinal branches give sensibility and motion to the small intes- tines, and when divided, purgatives generally fail to produce purgation. Function. A great sensitive nerve, which, through anastomotic fila- ments from motor sources, influences deglutition, the action of the heart, the circulatory and respiratory systems, voice, the secretions of the stomach, intestines, and various glandular organs. nth Pair. Spinal Accessory. Apparent Origin. By two sets of filaments : 1. A bulbar or medullary set, four or five in number, from the lateral or motor tract of the lower half of the medulla oblongata, below the origin of the pneumogastric. 2. A spinal set, from six to eight in number, from the lateral portion of the spinal cord, between the anterior and posterior roots of the upper four or five cervical nerves. Deep Origin. The medullary portion arises in a nucleus in the lower half of the floor of the 4th ventricle, common to the pneumogastric and glosso-pharyngeal nerves. The spinal portion has its origin in an elon- gated nucleus lying along the external surface of the anterior cornua of the spinal cord, extending down to the 5th cervical vertebra. Distribution. From this origin the fibres unite to form a main trunk, CRANIAL NERVES. 103 which enters the cranial cavity through the foramen magnum, where it is at times joined by fibres from the posterior roots of the two upper cervical nerves, and sends filaments to the ganglion of the root of the pneumo- gastric. After emerging from the cranial cavity through the jugular fora- men, it sends a branch to the pneumogastric, and receives others in return, and also from the 2d, 3d and 4th cervical nerves. It divides into two branches: (i) An internal or anastomotic branch, made up of filaments coming principally from the medulla oblongata, and is distributed to the muscles of the pharynx through the pharyngeal nerves coming from the pneumogastric ; to all the muscles of the larynx, except the crico-thyroid through the inferior laryngeal nerve ; to the heart, by filaments which reach it through the pneumogastric nerve. (2) An external branch, which is distributed to the sterno-cleido-mastoid and trapezius muscles ; these muscles also receiving filaments from the cervical nerves. Properties. At its origin it is a purely motor nerve, but in its course exhibits some sensibility from anastomosing fibres. Destruction of the medullary root, by tearing it from its attachment by means of forceps, impairs the action of the muscles of deglutition, and destroys the power of producing vocal sounds by paralysis of the laryngeal muscles, without, however, interfering with'the respiratory movements of the larynx ; these being controlled by other motor nerves. The normal rate of movement of the heart is also impaired by destruction of the medullary root. Irritation of the external branch' throws the trapezius and sterno-mastoid muscles into convulsive movements, though section of the nerve does not produce complete paralysis, as they are also supplied with motor influence from the cervical nerves. The sterno-mastoid and trapezius muscles per- form movements antagonistic to those of respiration, fixing the head, neck and upper part of the thorax, and delaying the expiratory movement during the acts of pushing, pulling, straining, etc. , and in the production of a pro- longed vocal sound, as in singing. When the external branch alone is divided, in animals, they experience shortness of breath during exercise, from a want of coordination of the muscles of the limbs and respiration ; and while they can make a vocal sound, it cannot be prolonged. Function. Governs phonation by its influence upon the vocal move- ments of the glottis ; influences the movements of deglutition, inhibits the action of the heart and controls certain respiratory movements associated with sustained or prolonged muscular efforts and phonation. 104 HUMAN PHYSIOLOGY. 1 2th Pair. Hypoglossal or Sublingual. Apparent Origin. By two groups of filaments from the medulla ob- longata, in the grooves between the olivary body and the anterior pyramid. Deep Origin. From the hypoglossal nucleus situated deeply in the substance of the medulla, on a level with the lowest portion of the floor of the 4th ventricle ; some decussating filaments have been traced to a higher encephalic centre. Distribution. The trunk formed by a union of the root filaments passes out of the cranial cavity through the anterior condyloid foramen, occasionally receiving a filament from the lateral and posterior portion of the medulla oblongata. After emerging from the cranium, it sends filaments to the sympathetic and pneumogastric ; it anastomoses with the lingual branch of the 5th pair, and receives and sends filaments to the upper cer- vical nerves. The nerve is finally distributed to the sterno-hyoid, sterno- thyroid, omo-hyoid, thyro-hyoid, stylo-glossi, hyo-glossi, genio-hyoid, genio- hyo-glossi, and the intrinsic muscles of the tongue. Properties. A purely motor nerve at its origin, but derives sensibility outside the cranial cavity, from anastomosis with the cervical, pneumo- gastric and 5th nerves. Irritation of the nerve gives rise to convulsive movements of the tongue and slight evidences of sensibility. Division of the nerve abolishes all movements of the tongue, and inter- feres considerably with the act of deglutition. When the hypoglossal nerve is involved in hemiplegia, the tip of the tongue is directed to the paralyzed side when the tongue is protruded ; due to the unopposed action of the genio-hyo-glossus on the sound side. Articulation is considerably impaired in paralysis of this nerve ; great difficulty being experienced in the pronunciation of the consonantal sounds. Mastication is performed with difficulty, from inability to retain the food between the teeth until it is completely triturated. Function. Governs all the movements of the tongue and influences the functions of mastication, deglutition and articulate language. CEREBRO-SPINAL AXIS. The Cerebro-Spinal Axis consists of the spinal cord, medulla oblon- gata, pons Varolii, cerebellum and cerebrum, exclusive of the spinal and cranial nerves. It is contained within the cavities of the cranium and spinal column, and surrounded by three membranes, the dura mater, MEMBRANES. 105 arachnoid and pia mater, which protect it from injury and supply it with blood vessels. The Brain and Spinal Cord are composed of both white fibres and collections of gray cells, and are, therefore, to be regarded as conductors of impressions and motor impulses, as well as generators of nerve force. MEMBRANES. The Dura Mater, the most external of the three, is a tough membrane, composed of white fibrous tissue, arranged in bundles, which interlace in every direction. In the cranial cavity it lines the inner surface of the bones, and is attached to the edge of the foramen magnum ; sends pro- cesses inward, forming the falx cerebri, falx cerebelli, and tentorium cere- belli, supporting and protecting parts of the brain. In the spinal canal it loosely invests the cord, and is separated from the walls of the canal by areolar tissue. The Arachnoid, the middle membrane, is a delicate serous structure which envelopes the brain and cord, forming the visceral layer, and is then reflected to the inner surface of the dura mater, forming the parietal layer. Between the two layers there is a small quantity of fluid which prevents friction by lubricating the two surfaces. The Pia Mater, the most internal of the three, composed of areolar tissue and blood vessels, covers the entire surface of the brain and cord, to which it is closely adherent, dipping down between the convolutions and fissures. It is exceedingly vascular, sending small blood vessels some dis- tance into the brain and cord. The Cerebro-spinal Fluid occupies the sub-arachnoid space, and the general ventricular cavities of the brain, which communicate by an opening, the foramen of Magendie, in the pia mater, at the lower portion of the 4th ventricle. This fluid is clear, transparent, alkaline, possesses a salt taste and a low specific gravity ; it is composed largely of water, traces of albu- men, glucose and mineral salts. It is secreted by the pia mater; the quantity is estimated from two to four fluid ozs. ^fo function of the cerebro-spinal fluid is to protect the brain and cord, by preventing concussion from without ; by being easily displaced into the spinal canal, prevents undue pressure and insufficiency of blood to the brain. 106 HUMAN PHYSIOLOGY. SPINAL CORD. The Spinal Cord varies from 16 to 18 inches in length ; is half an inch in thickness, weighs l^ oz., and extends from the atlas to the 2d lumbar vertebra, terminating in the filum terminate. It is cylindrical in shape, and presents an enlargement in the lower cervical and lower dorsal regions, corresponding to the origin of the nerves which are distributed to the upper and lower extremities. The cord is divided into two lateral halves by the anterior and posterior fissures. It is composed of both white or fibrous and gray or vesicular matter, the former occupying the exterior of the cord, the latter the interior, where it is arranged in the form of two crescents, one in each lateral half, united together by the central mass, the gray commissure ; the white matter being united in front by the white commissure. Structure of the White Matter. The white matter surrounding each lateral half of the cord is made up of nerve fibres, some of which are con- tinuations of the nerves which enter the cord, while others are derived from different sources. It is subdivided into: (l) An Anterior column, comprising that portion between the anterior roots and the anterior fissure, which is again subdivided into two parts : (a) an inner portion, bordering the anterior median fissure, the direct pyramidal tract, or column of Tiirck, containing motor fibres which do not decussate, and which extends as far down as the middle of the dorsal region ; (b] an outer portion, surrounding the anterior cornua, known as the anterior root zone, composed of short longitudinal fibres which serve to connect together different segments of the spinal cord. (2) A Lateral column, the portion between the anterior and posterior roots, which is divisible into [a] the crossed pyramidal tract, occupying the posterior portion of the lateral column, and containing all those fibres of the motor tract which have decussated at the medulla ob- longata; it is composed of longitudinally running fibres which are con- nected with the multipolar nerve cells of the anterior cornua ; (<$) the direct cerebellar tract, situated upon the surface of the lateral column, consisting of longitudinal fibres which terminate in the cerebellum ; it first appears in the lumbar region, and increases as it passes upward; (c) the anterior tract, lying just posterior to the anterior cornua. (3) A Posterior column, the portion included between the posterior roots and the posterior fissure, also divisible into two portions, (a) an inner portion, the postero- internal column, or the column of Goll, bordering the posterior median fissure, and (b} an external portion, the postero-external column, the column of Burdach, lying just behind the posterior roots. They are com- SPINAL CORD. 107 posed of long and short commissu segments of the spinal cord. Structure of the Gray Matter. The gray matter, ar- ranged in the form of two crescents, presents an anterior and posterior horn. It is made up of a delicate network of fine nerve fibres (axis cylinders) ? supported by a connective tissue framework of nucleated nerve cells, which in the anterior horns are large and multipolar, and connected with the anterior roots of spinal nerves ; in the posterior horns the nerve cells are smaller, and situated along the inner mar- gin, and in the caput cormi. Small cells are also found in the pos- terior vesicular columns, and in the intermediary lateral tract. ral fibres which connect together different FIG. 10. a b h. Scheme of the conducting paths in the spinal cord at the 3d dorsal nerve. The black part is the gray matter, v, anterior, h, w, pos- terior, root; a, direct, and g, crossed, pyra- midal tracts ; b, anterior column, ground bundle ; c, Coil's column ; d, postero-exter- nal column ; e and f, mixed lateral paths ; h, direct cerebellar tracts {Landois). COURSE OF THE ANTERIOR AND POSTERIOR ROOTS. The Anterior Roots pass through the anterior columns, horizontally, in straight -and distinct bundles, and enter the anterior cornuae, where they diverge in four directions, (i) Many become connected with the prolon- gations of the multipolar nerve cells. (2) Others leave the gray matter, pass through the anterior white commissure, and enter the anterior columns of the opposite side. (3) A considerable number enter the lateral columns of the same side, through which they pass to the medulla oblongata, where they decussate and finally terminate in the corpus striatum of the opposite side. (4) Others traverse the gray matter horizontally, and come into relation with the posterior roots. The Posterior Roots enter the posterior horns of the gray matter (i) through the substantia gelatinosa, (2) through the posterior columns ; of the former, some bend upward and downward, and become connected with the anterior cornuse ; others pass through the posterior commissure to the opposite side ; of the latter, fibres pass into the gray matter, to the posterior vesicular columns, passing obliquely through the posterior white columns upward and downward for some distance, and enter the gray matter at different heights. 108 HUMAN PHYSIOLOGY. FIG. ii. Diagram showing the course, through the spinal cord, of the motor and sensory nerve fibres. B and B' represent the right and left hemispheres of the brain, from which the motor fibres take their origin, and in which the sensory fibres terminate. The motor tract from the right side * passes down through the crus, through the pons to the medulla oblongata, where it divides into two portions ; ist, the larger portion, ninety- seven per cent., crosses over to the opposite side of the cord and passes down through the lateral column. It gives off fibres at different levels, which pass into the gray motor tract for the left hemisphere. The sensory fibres from the left side of the body enter the gray matter through the posterior roots. They then cross over at once to the opposite side of the cord and ascend to the hemisphere partly in the gray matter, partly in the posterior column. The same is true for the sensory nerves of the right side of the body. SPINAL CORD. 109 Decussation of Motor and Sensory Fibres. The Motor fibres, which conduct volitional impulses from the brain outward to the anterior cormice, arise in the motor centres of the cerebrum ; they then pass down- ward through the corona radiata, the internal capsule, the inferior portions of the crura cerebri, the pons Varolii, to the medulla oblongata, where the motor tract of each side divides into two portions, viz. : I. The larger ; containing 91 to 97 per cent, of the fibres, which decussates at the lower border of the medulla and passes down in the lateral column of the oppo- site side, and constitutes the crossed pyramidal tract. 2. The smaller, containing 3 to 9 per cent, of the fibres, does not decussate, but passes down the anterior column of the same side, and constitutes the direct pyramidal tract, or the column of Ttirck. Some of the motor fibres of these two tracts, after entering the anterior cornuae of the gray matter, become con- nected with the large multipolar nerve cells, while others pass directly into the anterior roots. Through this decussation each half of the brain governs the muscular movements of the opposite side of the body. The Sensory fibres, which convey the impression made upon the peri- phery to the cord and brain, pass into the cord through the posterior roots of spinal nerves ; they then diverge and enter the gray matter at different levels, and at once decussate, passing to the opposite side of the gray matter. The sensory tract passes upward, through the cord, the medulla, pons Varolii, the superior portion of the crura cerebri, the posterior third of the internal capsule, to the sensory perceptive centre, located in the hippocampus major and unciate convolution (Ferrier). Through this de- cussation each half of the brain governs the sensibility of the opposite half of the body. Properties of the Spinal Cord. Irritation applied directly to the antero- lateral white columns produces muscular movements but no pain; they are, therefore, excitable but insensible. The surface of the posterior columns is very sensitive to direct irritation, especially near the origin of the posterior roots; less so toward the pos- terior median fissure. The sensibility is due, however, not to its own proper fibres, but to the fibres of the posterior roots which traverse it. Division of the antero-lateral columns abolishes all power of voluntary movement in the lower extremities. Division of \ht posterior columns impairs the power of muscular coordi- nation, such as is witnessed in locomotor ataxia. The gray matter is probably both insensible and inexcitable under the influence of direct stimulation. A transverse section of one lateral half of the cord produces : 110 HUMAN PHYSIOLOGY. (1) On the same side, paralysis of voluntary motion and a relative or absolute elevation of temperature and an increased flow of blood in the paralyzed parts ; hyperaesthesia for the sense of contact, tickling, pain and temperature. (2) On the opposite side, complete anaesthesia as regards contact, and tickling and temperature, in the parts corresponding to those which are paralyzed in the opposite side. Complete preservation of voluntary power and of the muscular sense. A vertical section through the middle of the gray matter results in the loss of sensation on both sides of the body below the section, but no loss of voluntary power. FUNCTIONS OF THE SPINAL CORD. i. Asa Conductor. The Lateral columns, particularly the posterior portions, the " pyramidal tracts," and the columns of Tiirck, are the chan- nels through which pass the voluntary motor impulses from the brain to the large multipolar nerve cells in the anterior cornuae of gray matter, and through them become connected with the anterior roots which transmit the motor stimuli to the muscles. The Anterior columns, especially the portion surrounding the anterior cornuae, the " anterior radicular zones," are composed of short longitudinal commissural fibres, which serve to connect together different segments of the spinal cord, a condition required for the coordination of muscular movements. The Posterior columns are composed of short and long commissural fibres which connect together different segments of the cord. They are insensible to direct irritation, but aid in the coordination of muscular movements in walking, standing, running, etc. Degeneration of the pos- terior columns give rise to the lack of muscular coordination observed in locomotor ataxia. The Gray matter, and especially that portion immediately surrounding the central canal, transmits the sensory nerve fibres from the posterior roots up to the brain. Decussation of the sensory fibres takes place throughout the whole length of the gray matter. The Multipolar cells of the anterior cornuce are connected with the generation and transmission of motor impulses outward ; are centres for reflex movements ; are the trophic centres for the motor nerves and mus- cular fibres to which they are distributed. The anterior roots give passage to the vaso- constrictor and vaso-dilator fibres which exert an influence FUNCTIONS OF THE SPINAL CORD. Ill upon the calibre of the blood vessels. Complete destruction of the anterior horns is followed by a paralysis of motion, degeneration of the anterior roots, atrophy of muscles and bones and an abolition of reflex movements. 2. As an Independent Nerve Centre. The spinal cord, by virtue of its containing ganglionic nerve matter, is capable of transforming impressions made upon the centripetal nerves into motor impulses, which are reflected outward through centrifugal nerves to muscles, producing movements. These reflex movements taking place through the gray matter, are independent of sensation and volition. The mechanism involved in every reflex act is a sentient surface, a sensory nerve, a nerve centre, a motor nerve and muscle. The reflex excitability of the cord may be (i) Increased by disease of the lateral columns, the administration of strychnia, and in frogs, by a separation of the cord from the brain, the latter apparently exerting an inhibitory influence over the former and de- pressing its reflex activity. 2. Inhibited by destructive lesions of the cord, e. g., locomotor ataxia, atrophy of the anterior cornuse, the administration of various drugs, and, in the frog, by irritation of certain regions of the brain. When the cerebrum alone is removed and the optic lobes stimulated, the time elapsing between the application of an irritant to a sensory surface and the resulting move- ment will be considerably prolonged. The optic lobes (Setchenow's centre) apparently generating impulses which, descending the cord, retard its reflex movements. All movements taking place through the nervous system are of this reflex character, and may be divided into excito-motor, sensori-motor, and ideo-motor. Classification of Reflex Movements. (Kiiss.) They may be divided into four groups, according to the route through which the centripetal and centrifugal impulses pass. 1. Those normal reflex acts, e.g., deglutition, coughing, sneezing, walk- ing, etc., pathological reflex acts, e. ., tetanus, vomiting, epilepsy, which take place both centripetally and certrifugally, through spinal nerves. 2. Reflex acts which take place in a centripetal direction through a cerebro- spinal sensory nerve, and in a centrifugal direction through a sym- pathetic motor nerve, usually a vasomotor nerve, e. g.> the normal reflex acts, which give rise to most of the secretions, pallor and blushing of the skin, certain movements of the iris, certain modifications in the beat of the heart ; the pathological, which, on account of the difficulty in explaining their production, are termed metastatic, e. g., ophthalmia, coryza, orchitis, 112 HUMAN PHYSIOLOGY. which depend on a reflex hyperaemia; amaurosis, paralysis, paraplegia, etc., due to a reflex anaemia. 3. Reflex movements, in which the centripetal impulse passes through a sympathetic nerve, and the centrifugal through a cerebro-spinal nerve ; most of these phenomena are pathological, e. g., convulsions from intestinal irritation produced by the presence of worms, eclampsia, hysteria, etc. 4. Reflex actions, in which both the centripetal and centrifugal impulses pass through filaments of the sympathetic nervous system, e. g., those ob- scure reflex actions which preside over the secretions of the intestinal fluids, which unite the phenomena of the generative organs, the dilatation of the pupils from intestinal irritation (worms), and many pathological phenomena. Laws of Reflex Action. (Pfluger.) 1. Law of Unilaterality. If a feeble irritation be applied to one or more sensory nerves, movement takes place usually on one side only, and that upon the same side as the irritation. 2. Law of Symmetry. If the irritation becomes sufficiently intense, motor reaction is manifested, in addition, in corresponding muscles of the opposite side of the body. 3. Law of Intensity. Reflex movements are usually more intense on the side of the irritation ; at times the movements of the opposite side equal them in intensity, but they are usually less pronounced. 4. Law of Radiation. If the excitation still continues to increase, it is propagated upward, and motor reaction takes place through centrifugal nerves coming from segments of the cord higher up. 5. Law of Generalization. When the irritation becomes very intense, it is propagated to the medulla oblongata; motor reaction then becomes general, and is propagated up and down the cord, so that all the muscles of the body are thrown into action, the medulla oblongata acting as a focus whence radiate all reflex movements. Special Centres in the Spinal Cord. Genito-spinal centre. In the lower portion of the spinal cord are located the centres which control the sphincter muscles of the rectum and bladder, the erection of the penis, the emission of the semen, the action of the uterus during parturition, etc. Cilio-spinal centre. Situated in the spinal cord between the 6th cervical and 2d dorsal nerves ; stimulation of the cord in this situation produces a dilatation of both pupils through filaments of the sympathetic, which take their origin from this region of the cord. FUNCTIONS OF THE SPINAL CORD. 113 Throughout the spinal cord are situated numerous centres which preside over the following reflexes, viz. : The patellar tendon reflex takes place through the segments from which arise the 2d, 3d and 4th lumbar nerves ; the cremasteric reflex through the segment from which arise the 1st and 2d lumbar nerves; the abdominal reflex through the segments between the 8th and I2th dorsal nerves; the epigastric reflex through the segments from which arise the 4th, 5th and 6th dorsal nerves. Paralysis from Disease of the Spinal Cord. Seat of Lesion. If it be in the lower part of the sacral canal, there is paralysis of the compressor urethrse, accelerator urinse, and sphincter ani muscles ; no paralysis of the muscles of the leg. At the upper limit of the sacral region. Paralysis of the muscles of the bladder, rectum and anus ; loss of sensation and motion in the muscles of the legs, except those supplied by the anterior crural and obturator, viz. : psoas iliacus, Sartorius, pectineus, adductor longus, magnus and brevis, obturator, vastus externus and internus, etc. At the upper limit of the lumbar region. Sensation and motion para- lyzed in both legs ; loss of power over the rectum and bladder ; paralysis of the muscular walls of the abdomen interfering with expiratory move- ments. At the lower portion of the cervical region. Paralysis of the legs, etc., as above ; in addition, paralysis of all the intercostal muscles and conse- quent interference with respiratory movements ; paralysis of muscles of the upper extremities, except those of the shoulders. Above the middle of the cervical region. In addition to the preceding, difficulty of deglutition and vocalization, contraction of the pupils, paralysis of the diaphragm, scalene muscles, intercostals, and many of the accessory respiratory muscles ; death resulting immediately, from arrest of respiratory movements. Anterior half of spinal cord. Paraplegia developing symmetrically. Posterior half of spinal cord. Characteristic symptoms of locomotor ataxia or tabes dorsalis. In the gray substance in the vicinity of the central canal and anterior horns. If the lesion be acute, symptoms characteristic of acute spinal paralysis manifest themselves ; if chronic, symptoms characteristic of pro- gressive muscular atrophy. 114 HUMAN PHYSIOLOGY. MEDULLA OBLONGATA. The Medulla Oblongata is the expanded portion of the upper part of the spinal cord. It is pyramidal in form and measures one and a half inches in length, three-quarters of an inch in breadth, half an inch in thickness, and is divided into two lateral halves by the anterior and pos- terior median fissures, which are continuous with those of the cord. Each half is again subdivided by minor grooves, into four columus, viz. : anterior FIG. 12. n, and of Fourth Ventricle, with the neighboring parts. (From Sappey.) pyramid, lateral tract and olivary body, restiform body and posterior pyramid. 1. The anterior pyramid is composed partly of fibres continuous with those of the anterior column of the spinal cord ; but mainly of fibres de- rived from the lateral tract of the opposite side, by decussation. The united fibres then pass upward through the pons Varolii and crura cerebri, and for the most part terminate in the corpus striatum and cerebrum. 2. The lateral tract is continuous with the lateral columns of the cord ; MEDULLA OBLONGATA. 115 its fibres in passing upward take three directions, viz. : an external bundle joins the restiform body, and passes into the cerebellum ; an internal bundle decussates at the median line and joins the opposite anterior pyra- mid ; a middle bundle ascends beneath the olivary body, behind the pons, to the cerebrum, as the fasciculus teres. The olivary body of each side is an oval mass, situated between the anterior pyramid and restiform body; it is composed of white matter ex- ternally and gray matter internally, forming the corpus dentatum. 3. The restiform body, continuous with the posterior column of the cord, also receives fibres from the lateral column. As the restiform bodies pass upward they diverge and form a space, the 4th ventricle, the floor of which is formed by gray matter, and then turn backward and enter the cerebellum. 4. The posterior pyramid 'is a narrow, white cord bordering the posterior median fissure ; it is continued upward, in connection with the fasciculus teres, to the cerebrum. The Gray Matter of the medulla is continuous with that of the cord. It is arranged with much less regularity, becoming blended with the white matter of the different columns, with the exception of the anterior. By the separation of the posterior columns, the transverse commissure is exposed, forming part of the floor of the 4th ventricle; special collections of gray matter are found in the posterior portions of the medulla, connected with the roots of origin of different cranial nerves. Properties and Functions. The medulla is excitable anteriorly, and sensitive posteriorly to direct irritation. It serves (i) as a conductor of sensitive impressions upward from the cord, through the gray matter to the cerebrum ; (2) as a conductor of voluntary impulses from the brain to the spinal cord and nerves, through its anterior pyramids ; (3) as a con- ductor of coordinating impulses from the cerebellum, through fhe restiform bodies to the spinal cord. As an Independent Reflex Centre. The medulla oblongata con- tains special collections of gray matter, which constitute independent nerve centres which preside over different functions, some of which are as follows, viz. : 1. A centre which controls the movements of mastication, through afferent and efferent nerves. (See page 24.) 2. A centre reflecting impressions which influence the secretion of saliva. (See page 26.) 3. A centre for sucking, mastication and deglutition, whence are derived 116 HUMAN PHYSIOLOGY. motor stimuli exciting to action and coordinating the muscles of the palate, pharynx and oesophagus, necessary for the swallowing of the food. The secretion of saliva is also controlled by a centre in the medulla. NERVOUS CIRCLE OF DEGLUTITION. (2d and 3d Stages.) Excitor f Palatal branch of 5th pair. or j Pharnygeal branches of the glosso-pharyngeal. Centripetal 1 Superior laryngeal branches of the pneumogastric. Nerves. .[_ CEsophageal branches of the pneumogastric. Pharyngeal branches of the pneumogastric, derived Motor or Centrifugal Nerves. from the spinal accessory. Hypoglossal and branches of the cervical plexus. Inferior or recurrent laryngeal. Motor filaments of the 3d division of the 5th pair. Portio dura. 4. A centre which coordinates the muscles concerned in the act of vomiting. 5. A^ Speech centre, coordinating the various muscles necessary for the accomplishment of articulation through the hypoglossal, facial nerves and the 2d division of the 5th pair. 6. A centre for the harmonization of muscles concerned in expression, reflecting its impulses through the facial nerve. 7. A Cardiac centre, which exerts (i) an accelerating influence over the heart's pulsations through accelerating nerve fibres emerging from the cer- vical portion of the cord, entering the inferior cervical ganglion, and thence passing to the heart ; (2) an inhibitory or retarding influence upon the action of the heart, through fibres of the spinal accessory nerve running in the trunk of the pneumogastric. 8. A Vasomotor centre, which, by alternately contracting and dilating the blood vessels through nerves distributed in their walls, regulates the quantity of blood distributed to an organ or tissue, and thus influences nutrition, secretion and calorification. The vasomotor centre is situated in the medulla oblongata and pons Varolii, between the corpora quadri- gemina and the calamus scriptorius. The vasomotor fibres having their origin in this centre descend through the interior of the cord, emerge through the anterior roots of spinal nerves, enter the ganglia of the sympa- thetic, and thence pass to the walls of the blood vessels, and maintain the arterial tomis\ they may be divided into two classes, viz. : vaso-dilators, e. g., chorda tympani, and vaso-constrictors, e. g., sympathetic fibres. Division of the cord at the lower border of the medulla is followed by a dilatation of the entire vascular system and a marked fall of the blood pres- TONS VAROLII. 117 sure. Galvanic stimulation of the divided surface of the cord is followed by a contraction of the blood vessels and a rise in the blood pressure. 9. A Diabetic centre, irritation of which causes an increase in the amount of urine secreted, and the appearance of a considerable quantity of sugar. 10. Respiratory centre, situated near the origin of the pneumogastric nerves, presides over the movements of respiration and its modifications, laughing, sighing, sobbing, sneezing, etc. It may be excited reflexly by the presence of carbonic acid in the lungs irritating the terminal pneumo- gastric filaments ; or automatically, according to the character of the blood circulating through it ; an excess of carbonic acid or a diminution of oxygen increasing the number of respiratory movements ; a reverse condition di- minishing the respiratory movements. 11. A Spasm centre, stimulation of which gives rise to convulsive phe- nomena, such as coughing, sneezing, etc. 12. A centre for certain ocular functions, governing the closure of the eyelids and dilatation of the pupil. 13. A Sweat centre is also localized in the medulla. NERVOUS CIRCLE OF RESPIRATION (ENTIRELY REFLEX). -p . f Pulmonary branches of the pneumogastric. Superior laryngeal. Centripetal \ Trifacia1 ' or 5th pair. jx v I Nerves of general sensibility. [ Sympathetic nerve. j, [ Phrenic, distributed to the diaphragm. | Intercostals, distributed to the intercostal muscles. p t -f i ~\ Facial nerve, or portio dura, to the facial muscles. en n uga External branch of spinal accessory, to the trapezius erves " and sterno-cleido-mastoid muscles. PONS VAROLII. The Pons Varolii unites together the cerebrum above, the cerebellum behind, and the medulla oblongata below. It consists of transverse and longitudinal fibres, amidst which are irregularly scattered collections of gray or vesicular nervous matter. The transverse fibres unite the two lateral halves of the cerebellum. The longitudinal fibres are continuous (i) with the anterior pyramids of the medulla oblongata, which interlacing with the deep layers of the transverse fibres, ascend to the crura cerebri, forming their superficial or fasciculated portions ; (2) with fibres derived from the olivary fasciculus, 118 HUMAN PHYSIOLOGY. some of which pass to the tubercula quadrigemina, while others, uniting with fibres from the lateral and posterior columns of the medulla, ascend in the deep or posterior portions of the crura cerebri. Properties and Functions. The superficial portion is insensible and inexcitable to direct irritation ; the deeper portions appear to be excitable, consisting of descending motor fibres ; the posterior portions are sensible but inexcitable to irritation. Transmits motor impulses and sensory impressions from and to the cerebrum. The. gray ganglionic matter consists of centres which convert impres- sions into conscious sensations, and originate motor impulses, these taking place independent of any intellectual process ; they are the seat of instinct- ive reflex acts ; the centres which assist in the coordination of the auto- matic movements of station and progression. CRURA CEREBRI. The Crura Cerebri are largely composed of the longitudinal fibres of the pons (anterior pyramids, fasciculi teretes) ; after emerging from the pons they increase in size, and become separated into two portions by a layer of dark gray matter, the locus niger. The superficial portion, the crusta, composed of the anterior pyramids, constitutes the motor tract, which terminates, for the most part, in the corpus striatum, but to some extent, also, in the cerebrum ; the deep por- tion, made up of the fasciculi teretes and posterior pyramids and accessory fibres from the cerebellum, constitute the sensory tract (the tegmentum], which terminates in the optic thalamus and cerebrum. Function. The crura are conductors of motor impulses and sensory impressions ; the gray matter, the locus niger, assists in the coordination of the complicated movements of the eyeball and iris, through the motor oculi communis nerve. They also assist in the harmonization of general muscu- lar movements ; section of one cms giving rise to peculiar movements of rotation and somersaults forward and backward. CORPORA QUADRIGEMINA. The Corpora Quadrigemina are four small, rounded eminences, two on each side of the median line, situated immediately behind the third ventricle, and beneath the posterior border of the corpus callosum. The anterior tubercles are oblong from before backward, and larger than CORPORA STRIATA AND OPTIC THALAMI. 119 the posterior, which are hemispherical in shape ; they are grayish in color, but consist of white matter externally and gray matter internally. Both the anterior and posterior tubercles are connected with the optic thalami by commissural bands named the anterior and posterior brachia, respectively. They receive fibres from the olivary fasciculus and fibres from the cerebellum, which pass upward to enter the optic thalami. The corpora geniculata are situated, one on the inner side and one on the outer side of each optic tract, behind and beneath the optic thalamus, and from their position are named the corpora geniculata interna and externa ; they give origin to fibres of the optic nerve. Functions. The Tubercula quadrigemina are the physical centres of sight, translating the luminous impressions into visual sensations. Destruc- tion of these tubercles is immediately followed by a loss of the sense of sight ; moreover, their action in vision is crossed, owing to the decussation of the optic tracts, so that if the tubercle of the right side be destroyed by disease or extirpated, in a pigeon, the sight is lost in the eye of the oppo- site side, and the iris loses its mobility. The tubercula quadrigemina as nerve centres preside over the reflex movements which cause a dilation or contraction of the iris ; irritation of the tubercles causing contraction, destruction causing dilatation. Removal of the tubercles on one side produces a temporary loss of power of the opposite side of the body, and a tendency to move around an axis is mani- fested, as after a section of one crus cerebri, which, however, may be due to giddiness and loss of sight. They also assist in the coordination of the complex movements of the eye, and regulate the movements of the iris during the movements of accommodation for distance. CORPORA STRIATA AND OPTIC THALAMI. The Corpora Striata are two large ovoid collections of gray matter, situated at the base of the cerebrum, the larger portions of which are imbedded in the white matter, the smaller portions projecting into the anterior part of the lateral ventricle. Each striated body is divided, by a narrowband of white matter, into two portions, viz.: 1. The Caudate micleus, the intra ventricular portion, which is conical in shape, having its apex directed backward, as a narrow, tail-like process. 2. The Lenticular nucleus, imbedded in the white matter, and for the most part external to the ventricle ; on the outer side of the lenticular nucleus is found a narrow band of white matter, the external capsule ; 120 HUMAN PHYSIOLOGY. and between it and the convolutions of the island of Reil, a thin band of gray matter, the daustrum; the corpora striata are grayish in color, and when divided present transverse striations, from the intermingling of white fibres and gray cells. The Optic Thalami are two oblong masses situated in the ventricles posterior to the corpora striata, and resting upon the posterior portion of the crura cerebri. The internal surface projecting into the lateral ven- tricles is white, but the interior is grayish, from a commingling of both white fibres and gray cells. Separating the lenticular nucleus from the caudate nucleus and the optic thalamus, is a band of white tissue, the internal capsule. The internal capsule is a narrow, bent tract of white matter, and is, for the most part, an expansion of the motor tract of the crura cerebri. It consists of two segments, an anterior, situated between the caudate nucleus and the anterior surface of the lenticular nucleus, and a posterior, situated between the optic thalamus and the posterior surface of the len- ticular nucleus. These two segments unite at an obtuse angle, which is directed toward the median line. Pathological observation has shown that the nerve fibres of the direct and crossed pyramidal tracts can be traced upward through the anterior two-thirds of the posterior segment, into the centrum ovale, where, for the most part, they are lost ; a portion, however, remaining united, ascend higher and terminate in the paracentral lobule, the superior extremity of the ascending frontal and parietal convo- lutions. The sensory tract can be traced upward, through the posterior third, into the cerebrum, where they probably terminate in the hippo- campus major and unciate convolution. Functions. The Corpora striata are the centres in which terminate some of the fibres of the superficial or motor tract of the crura cerebri ; others pass upward through the internal capsule, to be distributed to the cerebrum. It might be inferred, from their anatomical relations, that they are motor centres. Irritation by a weak galvanic current produces mus- cular movements of the opposite side of the body; destruction of their substance by a hemorrhage, as in apoplexy, is followed by a paralysis of motion of the opposite side of the body, but there is no loss of sensation. When the hemorrhagic destruction involves the fibres of the anterior two- thirds of the posterior segment of the internal capsule, and thus separates them from their trophic centres in the cortical motor region, a descending degeneration is established, which involves the direct pyramidal tract of the same side and the crossed pyramidal tract of the opposite side. Destruction of the posterior one-third of the posterior segment of the CEREBELLUM. 121 internal capsule is followed by a loss of sensation on the opposite side of the body, and a loss of the senses of smell and vision on the same side (Charcot). The precise function of the corpora striata is unknown, but they are in some way connected with motion. The Optic thalami receives the fibres of the tegmentum, the posterior portion of the crura cerebri. They are insensible and inexcitable to direct irritation. Removal of one optic thalamus, or destruction of its substance by disease or hemorrhage, is followed by a loss of sensibility of the oppo- site side of the body, but there is no loss of motion ; their precise function is also unknown, but in some way connected with sensation. In both cases their action is crossed. CEREBELLUM. The Cerebellum is situated in the inferior fossoe of the occipital bone, beneath the posterior lobes of the cerebrum. It attains its maximum weight, which is about 5 ozs., between the twenty-fifth and fortieth years ; the proportion between the cerebellum and cerebrum being I to 8|-. It is composed of two lateral hemispheres and a central elongated lobe, the vermiform process ; the two hemispheres are connected with each other by the fibres of the middle peduncle forming the superficial portion of the pons Varolii. It is brought into connection with the medulla oblongata and spinal cord, through the prolongation of the restiform bodies ; with the cerebrum, by fibres passing upward beneath the corpora quadri- gemina and the optic thalami, and then forming part of the diverging cere- bral fibres. Structure. It is composed of both white and gray matter, the former being internal, the latter external, and convoluted, for economy of space. The White matter consists of a central stem, the interior of which is a dentated capsule of gray matter, the corpus dentatum. From the external surface of the stem of white matter processes are given off, forming the lamina , which are covered with gray matter. The Gray matter is convoluted and covers externally the laminated pro- cesses ; a vertical section through the gray matter reveals the following structures :. 1. A delicate connective tissue layer ', just beneath tlie pia mater, contain- ing rounded corpuscles, and branching fibres passing toward the external surface. 2. The cells of Purkinje, forming a layer of large, nucleated, branched nerve cells sending off processes to the external layer. I 122 HUMAN PHYSIOLOGY. 3. A granular layer of small, but numerous corpuscles. 4. Nerve fibre layer, formed by a portion of the white matter. Properties and Functions. Irritation of the cerebellum is not fol- lowed by any evidences either of pain or convulsive movements; it is, therefore, insensible and inexcitable. Co-ordination of Movements. Removal of the superficial portions of the cerebellum in pigeons produces feebleness and want of harmony in the muscular movements ; as successive slices are removed, the move- ments become more irregular, and the pigeon becomes restless ; when the last portions are removed, all power of flying, -walking, standing, etc., is entirely gone, and the equilibrium cannot be maintained, the power of coordinating muscular movements being entirely gone. The same results have been obtained by operating on all classes of animals. The following symptoms were noticed by Wagner, after removing the whole or a large part of the cerebellum. I. A tendency on the part of the animal to throw itself on one side, and to extend the legs as far as possible. 2. Torsion of the head on the neck. 3. Trembling of the muscles of the body, which was general. 4. Vomiting and occasionally liquid evacuations. Forced Movements. Division of one crus cerebelli causes the animal to fall on one side and roll rapidly on its longitudinal axis. According to Schiff, if the peduncle be divided from behind, the animal falls on the same side as the injury ; if the section be made in front, the animal turns to the opposite side. Disease of the cerebellum partially corroborates the result of experi- ments ; in many cases symptoms of unsteadiness of gait, from a want of coordination, have been noticed. Comparative anatomy reveals a remarkable correspondence between the development of the cerebellum and the complexity of muscular actions. It attains a much greater development, relatively to the rest of the brain, in those animals whose movements are very complex and varied in char- acter, such as the kangaroo, shark and swallow. The cerebellum may possibly exert some influence over the sexual func- tion, but physiological and pathological facts are opposed to the idea of its being the seat of the sexual instinct. It appears to be simply a centre for the coordination and equilibration of muscular movements. CEREBRUM. 123 CEREBRUM. The Cerebrum is the largest portion of the encephalic mass, constitut- ing about four-fifths of its weight; the average weight in the adult male is from 48 to 50 ozs., or about three pounds, while in the adult female it is about five ozs. less. After the age of forty the weight of the cerebrum gradually diminishes at the rate of one ounce every ten years. In idiots the brain weight is often below the normal, at times not amounting to more than twenty ounces. The Blood Supply to the cerebrum is unusually large, considering its comparative bulk; nearly one-fifth of the entire volume of blood being distributed to it by the carotid and vertebral arteries. These vessels anas- tomose so freely, and are so arranged within the cavity of the cranium, that an obstruction in one vessel will not interfere with the regular supply of blood to the parts to which its branches are distributed. A diminished amount, or complete cessation, of the supply of blood is at once followed by a suspension of its functional activity. The cerebrum is connected with the pons Varolii and medulla oblon- gata through the crura cerebri, and with the cerebellum, through the supe- rior peduncles. It is divided into two lateral halves, or hemispheres, by the longitudinal fissure running from before backward in the median line ; each hemisphere is composed of both white and gray matter, the former being internal, the latter external ; it covers the surfaces of the hemisphere which are infolded, forming convolutions, for economy of space. Fissures. 1. The Fissure of Sylvius is one of the most important; it is the first to appear in the development of the foetal brain, being visible at about the third month ; in the adult it is quite deep and well marked, running from the under surface of the brain upward, outward and backward, and forms a boundary between the frontal and temporo-sphenoidal lobes. 2. The Fissure of Rolando is second in importance, and runs from a point on the convexity near the median line transversely outward and downward toward the fissure of Sylvius, but does not enter it. It sepa- rates the frontal from the parietal lobe. 3. The Parietal 'fissure ', arising a short distance behind the fissure of Ro- lando, upon the convexity of the hemisphere, runs downward and back- ward to its posterior extremity. Secondary fissures of importance are found in different lobes of the cerebrum, separating the various convolutions. In the anterior lobe are found the pre-central, superior frontal and inferior frontal fissures ; 124 HUMAN PHYSIOLOGY. in the occipital lobe are found the parieto occipital and the calcarine fissures. Convolutions. Frontal lobe. The Ascending frontal convolution^ situated in front of the fissure of Rolando, runs downward and forward ; it is continuous above with the anterior frontal, and below with the inferior frontal convolution. FIG. 13. LEFT SIDE OF THE HUMAN BRAIN (DIAGRAMMATIC). F, frontal ; P, parietal; O, occipital ; T, temporo-sphenoidal lobe ; S, fis ure of Sylvius S', horizontal; S", ascending ramus of S ; c, sulcus centralis, or fissi re of Rolando A, ascending frontal, and B, ascending parietal, convolution; F 1( supe ior, F 2 , m ddle and FS, inferior, frontal convolutions; fj, superior, and f 2 , inferior, f ontal fiss ires f 3 , sulcus praecentralis ; P, superior parietal lobule ; P 2 , inferior parietal lobule con , sisting of P 2 , supra-marginal gyrus, and P' 2 , angular gyrus ; ip, sulcus interparie cm, termination of calloso-marginal fissure; Oi, first, Og, second, 03, third, occ alis ; pital , , , , , , , convolutions ; p o, parieto-occipital fissure ; second, temporo-sphenoidal fissues. {Landois' Physiology.} CEREBRUM. 125 The Superior frontal convolution is bounded internally by the longitu- dinal fissure, and externally by the superior frontal fissure ; it is connected with the superior end of the frontal convolution, and runs downward and forward to the anterior extremity of the frontal lobe, where it turns back- ward, and rests upon the orbital plate of the frontal bone. The Middle frontal convolution, the largest of the three, runs from be- hind forward, along the sides of the lobe, to its anterior part ; it is bounded above by the superior and below by the inferior frontal fissures. The Inferior frontal convolution winds around the ascending branch of the fissure of Sylvius, in the anterior and inferior portion of the cerebrum. 4- Parietal Lobe. The Ascending parietal convolution is situated just be- hind the fissure of Rolando, running downward and forward; above, it becomes continuous with the upper parietal convolution, and below, winds around to be united with the ascending frontal. The Upper parietal convolution is situated between the parietal and longitudinal fissures. The Supra-marginal convolution winds around the superior extremity of the fissure of Sylvius. The Angular convolution, a continuation of the preceding, follows the parietal fissure to its posterior extremity, and then makes a sharp angle downward and forward. Te7nporo-sphenoidal Lobe. Contains three well-marked convolutions, the superior, middle and inferior, separated by well-defined fissures, and continuous posteriorly with the convolutions of the parietal lobe. The Occipital Lobe lies behind the parieto- occipital fissure, and contains the superior, middle and inferior convolutions, not well marked. The Central Lobe, or Island of Reil, situated at the bifurcation of the fissure of Sylvius, is a triangular shaped cluster of six convolutions, the gyri operti, which are connected with those of the frontal, parietal, and tem- poro-sphenoidal lobes. Structure. The Gray matter of the cerebrum, about one-eighth of an inch thick, is composed of five layers of nerve cells: (i) a superficial layer, containing few small multipolar ganglion cells; (2) small ganglion cells, pyramidal in shape; (3) a layer of large pyramidal ganglion cells with processes running off superiorly and laterally ; (4) the granular for- mation containing nerve cells ; (5) spindle-shaped and branching nerve cells of moderate size. The White matter consists of three distinct sets of fibres : I. The diverging or peduncular fibres are mainly derived from the 126 HUMAN PHYSIOLOGY. columns of the cord and medulla oblongata ; passing upward through the crura cerebri, they receive accessory fibres from the olivary fasciculus, cor- pora quadrigemina and cerebellum. Some of the fibres terminate in the optic thalami and corpora striata, while others radiate into the anterior middle and posterior lobes of the cerebrum. 2. The transverse commissural fibres connect together the two hemi- spheres, through the corpus callosum and anterior and posterior commis- sures. 3. The longitudinal commissural fibres connect together different parts of the same hemisphere. Functions. The cerebral hemispheres are the centres of the nervous system through which are manifested all the phenomena of the mind ; they are the centres in which impressions are registered, and reproduced subsequently as ideas; they are the seat of intelligence, reason and will. However important a centre the cerebrum may be, for the exhibition of this highest form of nervous action, it is not directly essential for the con- tinuance of life ; for it does not exert any control over those automatic reflex acts, such as respiration, circulation, etc., which regulate the func- tions of organic life. From the study of comparative anatomy, pathology, vivisection, etc., evidence has been obtained which throws some light upon the physiology of the cerebral hemispheres. 1. Comparative Anatomy shows that there is a general connection be- tween the size of the brain, its texture, the depth and number of convolu- tions, and the exhibition of mental power. Throughout the entire animal series, the increase in intelligence goes hand in hand with an increase in the development of the brain. In man there is an enormous increase in size over that of the highest animals, the anthropoids. The most cultivated races of men have the greatest cranial capacity; that of the educated European being about 116 cubic inches, that of the Australian being about 60 cubic inches, a difference of 56 cubic inches. Men distinguished for great mental power usually have large and well-developed brains; that of Cuvier weighed 64 ozs.; that of Abercrombie 63 ozs.; the average being about 48 to 50 ozs.; not only the size, but above all, the texture of the brain, must be taken into consideration. 2. Pathology. Any severe injury or disease disorganizing the hemi- spheres is at once attended by a disturbance, or entire suspension of mental activity. A blow on the head producing concussion, or undue pressure from cerebral hemorrhage destroys consciousness; physical and chemical alterations in the gray matter have been shown to coexist with insanity, FIG. 14. SIDE VIEW OF THE BRAIN OF MAN, WITH THE AREAS OF THE CEREBRAL CONVOLUTIONS, ACCORDING TO FERRIER. The figures are constructed by marking on the brain of man, in their respective situations, the areas of the brain of the monkey as determined by experiment, and the description of the effects of stimulating the various areas refers to the brain of the monkey. (i) Advance of the opposite hind limb, as in walking. (2), (3), (4) Complex movements of the opposite leg and arm, and of the trunk, as in swimming. (a), (b), (c), (d) Individual and combined movements of the fingers and wrist of the opposite hand. Prehensile movements. 5) Extension forward of the opposite arm and hand. 1 , Supination and flexion of the opposite forearm. 7) Retraction and elevation of the opposite angle of the mouth, by means of the zygo- matic muscles. (8) Elevation of the ala nasi and upper lip, with depression of the lower lip on the opposite side. (9), do) Opening at the mouth, with (9) protrusion and (10) retraction of the tongue; region of aphasia, bilateral action. (u) Retraction of the opposite angle of the mouth, the head turned slightly to one side. (12) The eyes open widely, the pupils dilate, and the head and eyes turn toward the opposite side. (13), (13') The eyes move toward the opposite side with an upward (13) or downward (13') deviation. The pupils are generally contracted. (14) Pricking of the opposite ear, the head and eyes turn to the opposite side, and the pupils dilate largely. 128 HUMAN PHYSIOLOGY. loss of memory, speech, etc. Congenital defects of organization from im- perfect development are usually accompanied by a corresponding deficiency of intellectual power and the higher instincts. Under these circumstances no great advance in mental development can be possible, and the intelli- gence remains at a low grade. In congenital idiocy not only is the brain of small size, but it is wanting in proper chemical composition ; phosphorus , a characteristic ingredient of the nervous tissue, being largely diminished in amount. 3. Experimentation upon the lower animals by removing the cerebral hemispheres is attended by results similar to those observed in disease and injury. Removal of the cerebrum in pigeons produces complete abolition of intelligence, and destroys the capability of performing spontaneous movements. The pigeon remains in a condition of profound stupor, which is not accompanied, however, by a loss of sensation, or of the power of pro- ducing reflex or instinctive movements. The pigeon can be temporarily aroused by pinching the feet, loud noises, light placed before the eyes, etc., but soon relapses into a state of quietude, being unable to remember im- pressions and connect them with any train of ideas ; the faculties of memory, reason and judgment being completely abolished. CEREBRAL LOCALIZATION OF FUNCTION. From experiments made upon animals, and the results of clinical and post-mortem observations upon men, it has been shown that the phe- nomena of organic and psychical life are presided over by anatomically localized centres in the brain. A knowledge of the position of these centres becomes of the highest importance in localizing the seat of lesions, thrombi, hemorrhages, new growths, etc., which show themselves in paralyses, epilepsies, etc. It has not been possible to thus localize all functions, and to many parts of the brain no special use can be assigned. The following are the centres most definitely mapped out and that are of paramount importance : Motor Centres. These are in the cortical gray matter, and are ar- ranged along either side of the fissure of Rolando. The upper third of the ascending frontal and parietal convolutions about this fissure preside over the movements of the leg of the opposite side of the body ; the middle third controls the movements of the arm ; the upper part of the inferior third is the facial area. The lowest part of the inferior third governs the motility of the lips and tongue, and this space, with the posterior extremity of the third frontal convolution, constitutes the speech centre. The centres for the ocular muscles lie in the floor of the 4th ventricle. Destruction of CEREBRAL LOCALIZATION OF FUNCTION. 129 the gray matter at these points is followed by paralysis of the muscles of the opposite side of the body, and morbid growths, hemorrhages or thrombi of the vessels of the parts, result in abnormal stimulation or interference of the functions corresponding to the nature and extent of the lesion. Cere- bral or Jacksonian epilepsy is a result of local cortical disease. Lesions of the third frontal convolution on the left side, if the patient be right handed, produce the various forms of aphasia or the partial or complete loss of the power of articulate speech. In deaf mutes this con- volution is very imperfectly developed. Aphasia is of many degrees and kinds ; ataxic, when there is inability to execute the movements of the mouth, etc., necessary to speech; agraphic, if there be loss of the power of writing ; amnesic, when there is loss of memory of words ; paraphasic, if there is loss of the power to connect rightly the ideas with the proper use of words, etc. In word blindness the person cannot name a letter or a word when printed or written ; and in ivord deafness the patient hears sounds but does not hear words. Conditions of these kinds are apt to coexist with hemiplegia. Sensory Centres. These are the centres in which the sensory im- pressions are coordinated, and in which they probably become parts of our consciousness. The most important are : The Visual Centre, located in the occipital lobe and especially in the cuneus. Unilateral destruction of this area results in hemianopsia, or blindness of the corresponding halves of the two retinae. Destruction of both occipital lobes in man results in total blindness. Stimulation or irri- tation of the visual centre causes photopsia, or hallucinations of sight, in corresponding halves of the retinae. There have been instances of injury of these parts when sensations of color were abolished with preservation of those of space and light, thus showing a special localization of the color centre. Late experiments show that the centres of the two hemipheres are united, as ocular fatigue of a non-used eye was proportional to the fatigue of the exercised one. The Auditory Centres are located in the temporo-sphenoidal lobes. Word deafness is associated with softening of these parts, and their com- plete removal results in deafness. The Gustatory and Olfactory Centres are located in the uncinate gyrus, on the inner side of the temporo-sphenoidal lobes. There does not seem to be any differentiation, up to this time, of these two centres. " The Superior and Middle Frontal convolutions appear to be the seat of the reason, intelligence and will. Destruction of these parts is followed by proportional hebetude, without any impairment of sensation or motion. 130 HUMAN PHYSIOLOGY. SYMPATHETIC NERVOUS SYSTEM. The Sympathetic Nervous System consists of a chain of ganglia connected together by longitudinal nerve filaments, situated on each side of the spinal column, running from above downward. The two gangli- onic cords are connected together in the interior of the cranium by the ganglion of Ribes, on the anterior communicating artery, and terminate in the ganglion impar, situated at the tip of the coccyx. The chain of ganglia is divided into groups, and named according to the location in which they are found, viz. : cranial, four in number; cervical, three ; thoracic, twelve ; lumbar, five ; sacral, five ; coccygeal, one. Each ganglion consists of a collection of vesicular nervous matter, among which are found tubular and gelatinous nerve fibres. The ganglia are reinforced by motor and sensory fibres from the cerebro- spinal nervous system. The Ganglia are distinct nerve fibres, from which branches are dis- tributed to glands, arteries, muscles, and to the cerebral and spinal nerves ; many pass, also, to the visceral ganglia, e.g., cardiac, semilunar, pelvic, etc. Cephalic Ganglia. 1. The Ophthalmic or Ciliary ganglion is situated in the orbital cavity posterior to the eyeball; it is of small size, and of a reddish-gray color; receives filaments of communication from the motor oculi, ophthalmic branch of the 5th pair, and the carotid plexus. Its filaments of distribu- tion are the ciliary nerves which pass to the iris and ciliary muscle. Function. It is the centre through which the reflex acts take place by which the pupil is contracted or dilated; controls the movement of accommodation for vision at different distances. 2. The Spheno-palatine, or Meckel's ganglion, triangular in shape, is situated in the spheno-maxillary fossa ; receives filaments from the facial (Vidian nerve), and the superior maxillary branch of the 5th nerve. Its filaments of distribution pass to the gums, the soft palate, levator palati and azygos uvulae muscles. 3. The Otic, or Arnold's ganglion, is of small size, oval in shape, and situated beneath the foramen ovale ; receives a motor filament from the facial and sensory filaments from the glosso-pharyngeal and 5th nerve ; sends filaments to the mucous membrane of the tympanic cavity and to the tensor tympani muscle. 4. The Submaxillary ganglion, situated in the submaxillary gland, receives motor filaments from the chorda tympani, and sensory filaments from the lingual branch of the 5th nerve. Regulates to some extent the secretion of saliva. SYMPATHETIC NERVOUS SYSTEM. 131 Cervical Ganglia. The Superior cervical ganglion is fusiform in shape, of a grayish-red color, and situate opposite the 2d and 3d cervical vertebrae; it sends branches to form the carotid and cavernous plexuses which follow the course of the carotid arteries to their distribution; also sends branches to join the glosso-pharyngeal and pneumogastric, to form the pharyngeal plexus. The Middle cervical ganglion, the smallest of the three, is occasionally wanting ; it is situated opposite the 5th cervical vertebra ; sends branches to the superior and inferior cervical ganglion, and to the thyroid artery. The Inferior cervical ganglion, irregular in form, is situated opposite the last cervical vertebra; it is frequently fused with the first thoracic ganglion. The superior, middle and inferior cardiac nerves, arising from these cervical ganglia, pass downward and forward to form the deep and super- ficial cardiac plexuses located at the bifurcation of the trachea, from which branches are distributed to the heart, coronary arteries, etc. The Thoracic Ganglia are usually twelve in number, placed against the heads of the ribs behind the pleura ; they are small in size and gray in color ; they communicate with the cerebro-spinal nerves by two filaments, one of which is white, the other gray. The great splanchnic nerve is formed by the union of branches from the sixth, seventh, eighth and ninth ganglia; it passes through the diaphragm to the semilunar ganglion. The lesser splanchnic nerve is formed by the union of filaments from the tenth and eleventh ganglia, and is distributed to the coeliac plexus. The renal splanchnic nerve arises from the last thoracic ganglion and terminates in the renal plexus. The semilunar ganglia, the largest of the sympathetic, are situated by the side of the coeliac axis ; they send radiating branches to form the solar plexus; from the various plexuses, nerves follow the gastric, splenic, hepatic, renal, etc., arteries, into the different abdominal viscera. The Lumbar Ganglia, four in number, are placed upon the bodies of the vertebra ; they give off branches which unite to form the aortic lumbar plexus and the hypogastric plexus, and follow the blood vessels to their terminations. The Sacral and Coccygeal Ganglia send filaments of distribution to all the blood vessels of the pelvic viscera. Properties and Functions. The sympathetic nerve possesses both sensibility and the power of exciting motion, but these properties are much 132 HUMAN PHYSIOLOGY. less decided than in the cerebro- spinal system. Irritation of the ganglia does not produce any evidence of pain until some time has elapsed. If caustic soda be applied to the semilunar ganglia, or a galvanic current be passed through the splanchnic nerves, no instantaneous effect is noticed, as in the case of the cerebro-spinal nerves ; but in the course of a few seconds a slow, progressive contraction of the muscular coat of the intestines is established, which continues for some time after the irritation is removed. Division of the sympathetic nerve in the neck is followed by a vascular congestion of the parts above the section on the corresponding side, attended by an increase in the temperature ; not only is there an increase in the amount of blood, but the rapidity of the blood current is very much hastened, and the blood in the veins becomes of a brighter color. Gal- vanization of the upper end of the divided nerve causes all of the preced- ing phenomena to disappear ; the congestion decreases, the temperature falls, and the venous blood becomes dark again. The sympathetic exerts a similar influence upon the circulation of the limbs and the glandular organs ; destruction of the first thoracic ganglion and division of the nerves forming the lumbar and sacral plexuses is followed by a dilatation of the vessels, an increased rapidity of the circu- lation, and an elevation of temperature in the anterior and posterior limbs ; galvanization of the peripheral ends of these nerves causes all of these phenomena to disappear. Division of the splanchnic nerve causes a dilatation of the blood vessels of the intestine. These phenomena of the sympathetic nerve system are dependent upon the presence of vasomotor nerves which, under normal circumstances, exert a tonic influence upon the blood vessels. These nerves, derived from the cerebro-spinal system, the medulla oblongata, leave the spinal cord by the rami communicantes, enter the sympathetic ganglia, and finally terminate in the muscular wall of the blood vessels. Sleep is a periodical condition of the nervous system, in which there is a partial or complete cessation of the activities of the higher nerve centres. The cause of sleep is a diminution in the quantity of blood, occasioned by a contraction of the smaller arteries under the influence of the vasomotor nerves. During the waking state the brain undergoes a physiological waste, as a result of the exercise of its functions ; after a certain length of time its activities become enfeebled, and a period of repose ensues, during which a regeneration of its substance takes place. When the brain becomes enfeebled there is a diminished molecular activity and an accumulation of waste products ; under these circumstances THE SENSE OF TOUCH. 133 it ceases to dominate the medulla oblongata and the spinal cord. These centres then act more vigorously, and diminish the calibre of the cerebral blood vessels through the action of the vasomotor nerves, producing a con- dition of physiological anaemia and sleep; during this state waste products are removed, force is stored up, nutrition is restored, and waking finally occurs. THE SENSE OF TOUCH. The Sense of Touch is a modification of general sensibility, and located in the skin, which is especially adapted for this purpose, on account of the number of nerves and papillary elevations it possesses. The struc- tures of the skin and the modes of termination of the sensory nerves have already been considered. The Tactile Sensibility varies in acuteness in different portions of the body; being most marked in those regions in which the tactile corpuscles are most abundant, e. g. t the palmar surface of the third phalanges of the fingers and thumb. The relative sensibility of different portions of the body has been ascer- tained by means of a pair of compasses, the points of which are guarded by cork, and then determining how closely they could be brought together, and yet be felt at two distinct points. The following are some of the measurements : Point of tongue ^ of a line. Palmar surface of third phalanx I line. Red surface of lips 2 lines. Palmar surface of metacarpus 3 " Tip of the nose 3 " Part of lips covered by skin , 4 " Palm of hand 5 " Lower part of forehead 10 " Back of hand 14 " Dorsum of foot 18 " Middle of the thigh 30 " The sense of touch communicates to the mind the idea of resistance only, and the varying degrees of resistance offered to the sensory nerves enables us to estimate, with the aid of the muscular sense, the qualities of hardness and softness of external objects. The idea of space or extension is obtained when the sensory surface or the external object changes its place in regard to the other, the character of the surface, its roughness or smooth- ness^ is estimated by the impressions made upon the tactile papillae. Appreciation of Temperature. The general surface of the body is more 134 HUMAN PHYSIOLOGY. or less sensitive to differences of temperature, though this sensation is separate from that of touch; whether there are nerves especially adapted for the conduction of this sensation has not been fully determined. Under pathological conditions, however, the sense of touch may be abolished, while the appreciation of changes in temperature may remain normal. This cutaneous surface varies in its sensibility to temperature in different parts of the body, and depends, to some extent, upon the thickness of the skin, exposure, habit, etc. ; the inner surface of the elbow is more sensi- tive to changes in temperature than the outer portion of the arm ; the left hand is more sensitive than the right; the mucous membrane less so than the skin. Excessive heat or. cold has the same effect upon the sensibility ; the temperatures most readily appreciated are those between 50 F. and 1 15 F. The sensation of pain and tickling appear to be conducted to the brain, also, by nerves different from those of touch ; in abnormal conditions the appreciation of pain may be entirely lost, while touch remains unimpaired. THE SENSE OF TASTE. The Sense of Taste is localized mainly in the mucous membrane covering the superior surface of the tongue. The Tongue is situated in the floor of the mouth ; its base is directed backward, and connected with the hyoid bone, by numerous muscles, with the epiglottis and soft palate ; its apex is directed forward against the pos- terior surface of the teeth. The substance of the tongue is made up of intrinsic muscular fibres, the linguales ; it is attached to surrounding parts, and its various move- ments performed by the extrinsic muscles, e. g., stylo-glossus, genio-hyo- glossus, etc. The mucous membrane covering the tongue is continuous with that lining the commencement of the alimentary canal, and is furnished with vascular and nervous papillae. The papilla are analogous in their structure to those of the skin, and are distributed over the dorsum of the tongue, giving it its characteristic roughness. There are three principal varieties : 1. Tht filiform papilla are most numerous, and cover the anterior two- thirds of the tongue ; they are conical or filiform in shape, often prolonged into filamentous tufts, of a whitish color, and covered by horny epithelium. 2. The fungiform papilla are found chiefly at the tip and sides of the THE SENSE OF TASTE. 135 tongue ; they are larger than the preceding, and may be recognized by their deep red color. 3. The circumvallate papilla are rounded eminences, from eight to ten in number, situated at the base of the tongue, where they form a V-shaped figure. They are quite large, and consist of a central projection of mucous membrane, surrounded by a wall, or circumvallation, from which they derive their name. The Taste Beakers, supposed to be the true organs of taste, are flask- like bodies, ovoid in form, about the 1 ? of an inch in length, situated in the epithelial covering of the mucous membrane, on the circumvallate papillae. They consist of a number of fusiform, narrow cells, and curved so as to form the walls of this flask-like body ; in the interior are elongated cells, with large, clear nuclei, the taste cells. Nerves of Taste. The chorda tympani nerve, a branch of the facial, after leaving the cavity of the tympanum, joins the 3d division of the 5th nerve between the two pterygoid muscles, and then passes forward in the lingual branches, to be distributed to the mucous membrane of the anterior two-thirds of the tongue. Division or disease of this nerve is followed by a loss of taste in the part to which it is distributed. The glosso-pharyngeal enters the tongue at the posterior border of the hyo-glossus muscle, and is distributed to the mucous membrane of the base and sides of the tongue, fauces, etc. The lingual branch of the trifacial nerve endows the tongue with gen- eral sensibility; the hypoglossal endows it with motion. The nerves of taste in the superficial layer of the mucous membrane form a fine plexus, from which branches pass to the epithelium and pene- trate it ; others enter the taste beakers, and are directly connected with the taste cells. The seat of the sense of taste has been shown by experiment to be the whole of the mucous membrane over the dorsum of the tongue, soft palate, fauces, and upper part of the pharynx. The Sense of Taste enables us to distinguish the savor of substances introduced into the mouth, which is different from tactile sensibility. The sapid quality of substances appreciated by the tongue are designated as bitter, sweet, alkaline, sour, salt, etc. The Essential Conditions for the production of the impressions of taste are (i) a state of solubility of the food; (2) a free secretion of the saliva, and (3) active movements on the part of the tongue, exciting pres- sure against the roof of the mouth, gums, etc., thus aiding the solution of 136 HUMAN PHYSIOLOGY. various articles and their osmosis into the lingual papillae. Sapid substances, when in a state of solution, pass into the interior of the taste beakers and come into contact, through the medium of the taste cells, with the terminal filaments of the gustatory nerves. THE SENSE OF SMELL. The Sense of Smell is located in the mucous membrane lining the upper part of the nasal cavity, in which the olfactory nerves are distributed. The Nasal Fossae are two cavities, irregular in shape, separated by the vomer, the perpendicular plate of the ethmoid bone, and the triangular cartilage. They open anteriorly and posteriorly by the anterior and pos- terior nares, the latter communicating with the pharynx. They are lined by mucous membrane, of which the only portion capable of receiving odor- ous impressions is the part lining the upper one-third of the fossae. The Olfactory Nerves, arising by three roots from the posterior and inferior surface of the anterior lobes, pass forward to the cribriform plate of the ethmoid bone, where they each expand into an oblong body, the olfactory bulb. From its under surface from fifteen to twenty filaments pass downward through the foramina, to be distributed to the olfactory mucous membrane, where they terminate in long, delicate, spindle-shaped cells, the olfactory cells, situated between the ordinary epithelial cells. The olfactory bulbs are the centres in which odorous impressions are perceived as sensations ; destruction of these bulbs being attended by an abolition of the sense of smell. In animals which possess an acute sense of smell, there is a correspond- ing increase in the development of the olfactory bulbs. The Essential Conditions for the sense of smell are, (i) a special nerve centre capable of receiving impressions and transforming them into odorous sensations. (2) Emanations from bodies which are in a gaseous or vaporous condition. (3) The odorous emanations must be drawn freely through the nasal fossae ; if the odor be very faint, a peculiar inspiratory movement is made, by which the air is forcibly brought into contact with the olfactory filaments. The secretions of the nasal fossae probably dissolve the odorous particles. Various substances, as ammonia, horseradish, etc., excite the sensibility of the mucous membrane, which must be distinguished from the perception of true odors. THE SENSE OF SIGHT. 137 THE SENSE OF SIGHT. The Eyeball. The eyeball, or organ of vision, is situated within the orbital cavity, and loosely held in position by the fibrous capsule of Tenon. It rests upon a cushion of fat, which never disappears, except in cases of extreme starvation ; it is protected from injury by the bony orbital walls, the lids and lashes, and is so situated as to permit an extensive range of vision. Blood vessels and Nerves. The structures of the eyeball are supplied with blood by the ciliary arteries, which pierce the posterior surface around the optic nerve. The Ciliary or Ophthalmic ganglion, about the size of a pin's head, situated in the posterior portion of the orbital cavity, receives filaments of communication from the trifacial or 5th nerve, the motor oculi or 3d nerve, and the sympathetic. From its anterior portion are given off the ciliary nerves, which enter the ball posteriorly and are distributed to the structures of which it is composed. Structure. The form of the eyeball is that of a sphere ; it is about one inch in the transverse diameter, and a little longer in the antero-posterior diameter, on account of its having the segment of a smaller sphere inserted into the anterior surface. The Sclerotic and Cornea together form the external coat of the eye ; the former covering the posterior J, the latter, the anterior \. The sclerotic is a dense, opaque, fibrous membrane, varying in thickness from the JQ- to the -^ of an inch ; it is composed of connective tissue and is slightly vascular. Posteriorly it is continuous with the sheath of the optic nerve, and is pierced by that nerve, as well as by the ciliary vessels and nerves ; anteriorly its fibres become quite pale, and after passing into the cornea, transparent. It is a protective covering, and gives attachment to the tendons of the muscles by which the eyeball is moved. The Cornea is a non- vascular, transparent membrane, composed for the most part of connective tissue in which are contained stellate corpuscles filled with a clear fluid. It is covered anteriorly by the basement mem- brane of the conjunctiva, upon which rests several layers of epithelial cells ; posteriorly it is lined by the membrane of Descemet, which is reflected on to the anterior surface of the iris. The Choroid, the Iris, the Ciliary Muscle and Ciliary Processes, together constitute the middle coat of the eye. The Choroid coat, about the ^ of an inch in thickness, is the vascular tunic ; it is connected with the sclerotic by the lamina fusca. From within outward we distinguish the following layers : J 138 HUMAN PHYSIOLOGY. 1. The lamina supra-choroidea. 2. The elastic layer of Sattler, consisting of two endothelial layers. 3. The chorio-capillaris, choroid proper, or membrane of Ruysch, a thick elastic network of arterioles and capillaries lying within the outer layer of veins and larger vessels, called the vena vorticosse. 4. The lamina vitrea, or internal limiting membrane. (The pigmentary layer, formerly classed as belonging to the choroid, is now known to belong, embryologically and physiologically, to the retina.) The Function of the Choroid is to provide for the vascular supply and drainage of the body of the eye, and to furnish an uniform and high temperature to the retina. FIG. 15. SCLEROTIC COAT REMOVED TO SHOW THE CHOROID, CILIARY MUSCLE AND NERVES. a. Sclerotic coat. b. Veins of the choroid. c. Ciliary nerves, d. Veins of the choroid. e. Ciliary muscle, f. Iris. (From Holders Anatomy.} The Iris is a circular, muscular diaphragm, placed in the anterior por- tion of the eye, and perforated a little to the nasal side of the centre by a circular opening, the pupil; it is attached by its periphery to the point of junction of the sclerotic and cornea. It is composed of a connective- tissue stroma, blood vessels and non-striated muscular fibres, circular and radiat- ing. The circular fibres surround the margin of the pupil like a sphincter, and are controlled by the 3d pair of nerves ; the radiating fibres (dilators of the pupil) radiate from the centre toward its circumference, and are controlled by the sympathetic system of nerves. The Ciliary muscle is a grayish circular band, consisting of unstriped THE SENSE OF SIGHT. 139 muscular, fibres, about one-eighth of an inch long, running from before backward; beneath the radiating fibres are small bands of circular fibres running around the eye. It arises from the line of junction of the sclerotic, cornea and iris ; passing backward it is attached to the outer surface of the choroid ; it is the principal agent in accommodation, and innervated by the 3d pair of nerves. The Retina forms the internal coat of the eye ; in the fresh state it is a delicate, transparent membrane, but soon becomes opaque and of a pinkish tint ; it extends forward almost to the ciliary processes, where it terminates in the ora serrata. In the posterior portion of the retina, at a point cor- responding to the axis of vision, is a rounded, elevated yellow spot, the limbus luteus, having a central depression, ihefovea centralis ; about -^ of an inch to the inner side is the point of entrance of the optic nerve, where it spreads out to assist in the formation of the retina. The arteria centralis retina pierces the optic nerve near the sclerotic, runs forward in its sub- stance and is distributed in the retina as far forward as the ciliary processes. The Retina consists of ten distinct layers, from within outward, sup- ported by connective tissue. I. Membrana limitans interna. 2. Fibres of optic nerve. 3. Layers of ganglionic corpuscles. 4. Molecular layer. 5. Internal granular layer. 6. Molecular layer. 7. External granular layer. 8. Membrana limitans externa. 9. Layer of rods and cones. 10. The layer of pigment cells. The number of optic nerve fibres in the retina is estimated to be about 800,000, and for each fibre there are about seven cones, 100 rods, and seven pigment cells. The points of the rods and cones are directed toward the choroid, or away from the entering light, and dip into the pigmentary layer. They, with the pigment layer, are the elements inter- mediating the change of the ethereal vibrations into nervous force. Out of these nerve messages the centre in the occipital lobe fashions the sensations of light, color and form. In the Fovea centralis^ at the point of most distinct vision, all of the layers disappear except the layer of rods and cones, which becomes some- what longer and more slender. The Aqueous humor is a clear fluid, alkaline in reaction, occupying the anterior chamber of the eye; this chamber is bounded in front by the cornea, posteriorly by the iris. The Vitreous humor forms about four-fifths of the entire ball. It sup- ports the retina, and is excavated anteriorly for the reception of the lens ; it is transparent, of a jelly-like consistence, and surrounded by a structure- less, transparent membrane, the hyaloid membrane. 140 HUMAN PHYSIOLOGY. The Crystalline lens is situated immediately behind the pupil, in the concavity of the vitreous humor. It is inclosed in a highly elastic, trans- parent membrane, the capsule. The lens is a transparent, double- convex body, y of an inch transversely, * of an inch antero-posteriorly ; it is held in position by the suspensory ligament, formed by a splitting of the hyaloid tunic, the external layer of which passes in front of the lens, the internal layer behind it. Its function is to aid in refracting the rays of light and bring them to a focus upon the retina. FIG. 16. DIAGRAM OF A VERTICAL SECTION OF THE EYE. i. Anterior chamber filled with aqueous humor. 2. Posterior Chamber. 3. Canal of Petit. a. Hyaloid membrane. b. Retina (dotted line). c, Choroid coat (black line). d. Sclerotic coat. e. Cornea, f. Iris. g. Ciliary processes, h. Canal of Schlemm or Fontana. z. Ciliary muscle. {From Holden' s Anatomy.) Vision. The eye may be regarded as a camera obscura, in which images of external objects are thrown upon a screen, the retina, by means of a double convex lens. The Essential Conditions for proper vision are : I. Certain refract- ing media, g ; (2) dentals, d,j, s, t, z ; (3) nasals, m, n, ng ; (4) labials, ^, /,_/",#, m ; (5) gutturals, /, g, c> and g hard ; (6) liquids, /, m, n, r. GENERATIVE ORGANS OF THE FEMALE. 151 REPRODUCTION. Reproduction is the function by which the species is preserved, and is accomplished by the organs of generation in the two sexes. GENERATIVE ORGANS OF THE FEMALE. The Generative Organs of the Female consist of the ovaries, Fal- lopian tubes, uterus and vagina. The Ovaries are two small, ovoid, flattened bodies, measuring one inch and a half in length and three-quarters of an inch in width ; they are situated in the cavity of the pelvis, and imbedded in the posterior layer of the broad ligament ; attached to the uterus by a round ligament, and to the extremities of the Fallopian tubes by the fimbriae. The ovary consists of an external membrane of fibrous tissue, the cortical portion, in which are imbedded the Graafian vesicles, and an internal portion, the stroma, containing blood vessels. The Graafian Vesicles are exceedingly numerous, but situated only in the cortical portion. Although the ovary contains the vesicles from the period of birth, it is only at the period of puberty that they attain their full development. From this time onward to the catamenial period, there is a constant growth and maturation of the Graafian vesicles. They consist of an external investment, composed of fibrous tissue and blood vessels, in the interior of which is a layer of cells forming the membrana granulosa ; at its lower portion there is an accumulation of cells, the proligerous disc, in which the ovum is contained. The cavity of the vesicle contains a slightly yellowish, alkaline, albuminous fluid. The Ovum is a globular body, measuring about the T ^j- of an inch in diameter; it consists of an external investing membrane, the vitelline mem- brane, a central granular substance, the vitellus, or yelk, a nucleus, the germinal vesicle, in the interior of which is imbedded the nucleolus, or germinal spot. The Fallopian Tubes are about four inches in length, and extend outward from the upper angles of the uterus, between the folds of the broad ligaments, and terminate in a fringed extremity, which is attached by one of the fringes to the ovary. They consist of three coats : (l) the 152 HUMAN PHYSIOLOGY. external, or peritoneal, (2) middle, or muscular, the fibres of which are arranged in a circular or longitudinal direction, (3) internal, or mucous, covered with ciliated epithelial cells, which are always waving from the ovary toward the uterus. The Uterus is pyriform in shape, and may be divided into a body and neck ; it measures about three inches in length and two inches in breadth in the unimpregnated state. At the lower extremity of the neck is the os externum ; at the junction of the neck with the body is a constriction, the os internum. The cavity of the uterus is triangular in shape, the walls of which are almost in contact. The walls of the uterus are made up of several layers of non-striated muscular fibres, covered externally by peritoneum, and lined internally by mucous membrane, containing numerous tubular glands, and covered by ciliated epithelial cells. The Vagina is a membranous canal, from five to six inches in length, situated between the rectum and bladder. It extends obliquely upward from the surface, almost to the brim of the pelvis, and embraces at its upper extremity the neck of the uterus. Discharge of the Ovum. As the Graafian vesicle matures, it increases in size, from an augmentation of its liquid contents, and approaches the surface of the ovary, where it forms a projection, measuring from one-fourth to one-half an inch in size. The maturation of the vesicle occurs periodic- ally, about every twenty-eight days, and is attended by the phenomena of menstruation. During this period of active congestion of the reproductive organs the Graafian vesicle ruptures, the ovum and liquid contents escape, and are caught by the fimbriated extremity of the Fallopian tube, which has adapted itself to the posterior surface of the ovary. The passage of the ovum through the Fallopian tube into the uterus occupies from ten to four- teen days, and is accomplished by muscular contraction and the action of the ciliated epithelium. Menstruation is a periodical discharge of blood from the mucous mem- brane of the uterus, due to a fatty degeneration of the small blood vessels. Under the pressure of an increased amount of blood in the reproductive organs, attending the process of ovulation, the blood vessels rupture, and a hemorrhage takes place into the uterine cavity ; thence it passes into the vagina. Menstruation lasts from five to six days, and the amount of blood discharged averages about five ounces. Corpus Luteum. For some time anterior to the rupture of a Graafian vesicle, it increases in size and becomes vascular ; its walls become thick- GENERATIVE ORGANS OF THE FEMALE. 153 ened, from the deposition of a reddish-yellow, glutinous substance, a product of cell growth from the proper coat of the follicle and the membrana granulosa. After the ovum escapes, there is usually a small effusion of blood into the cavity of the follicle, which soon coagulates, loses its coloring matter, and acquires the characteristics of fibrin, but it takes no part in the formation of the corpus luteum. The walls of the follicle become convo- luted, vascular, and undergo hypertrophy, until they occupy the whole of the follicular cavity. At its period of fullest development, the corpus luteum measures three-fourths of an inch in length and half an inch in depth. In a few weeks the mass loses its red color, and becomes yellow, constitut- ing the corpus luteum, or yellow body. It then begins to retract, and becomes pale ; and at the end of two months nothing remains but a small cicatrix upon the surface of the ovary. Such are the changes in the follicle, if the ovum has not been impregnated. The corpus luteum, after impregnation has taken place, undergoes a much slower development, becomes larger, and continues during the entire period of gestation. The difference between the corpus luteum of the unimpregnated and pregnant condition is expressed in the following table by Dalton : Corpus Luteum of Menstruation. Corpus Luteum of Pregnancy. Three-quarters of an inch in diameter; central clot reddish ; convoluted wall pale. At the end of three weeks. One month. Two months. Four months. Six months. Nine months. Smaller ; convoluted wall bright yellow ; clot still reddish. Reduced to the condi- tion of an insignificant, cicatrix. Absent able. Absent. Absent. or unnotice- Larger ; convoluted wall bright yellow ; clot still red- dish. Seven-eighths of an inch in diameter ; convoluted wall bright yellow ; clot perfectly decolorized. Seven-eighths of an inch in diameter; clot pale and fibrinous ; convoluted wall dull yellow. Still as large as at the end of second month; clot fibrin- ous ; convoluted wall paler. Half an inch in diameter ; central clot converted into a radiating cicatrix; external wall tolerably thick and con- voluted, but without any bright yellow color. 154 HUMAN PHYSIOLOGY. GENERATIVE ORGANS OF THE MALE. The Generative Organs of the Male consist of the testicles, vasa deferentia, vesiculae seminales and penis. The Testicles, the essential organs of reproduction in the male, are two oblong glands, about an inch and a half in length, compressed from side to side, and situated in the cavity of the scrotum. The proper coat of the testicle, the tunica albuginea, is a white, fibrous structure, about the -j=% of an inch in thickness; after enveloping the testicle, it is reflected into its interior at the posterior border, and forms a vertical process, the mediastinum testes, from which septa are given off, dividing the testicle in lobules. The substance of the testicle is made up of the seminiferous tubules, which exist to the number of 840 ; they are exceedingly convoluted, and when unraveled are about 30 inches in length. As they pass toward the apices of the lobules they become less convoluted, and terminate in from 20 to 30 straight ducts, the vasa recta, which pass upward through the mediastinum and constitute the rete testis. At the upper part of the mediastinum the tubules unite to form from 9 to 30 small ducts, the vasa efferentia, which become convoluted, and form the globus major of the epididymis ; the continuation of the tubes downward behind the testicle and a second convolution constitutes the body and globus minor. The seminal tubule consists of a basement membrane lined by granular nucleated epithelium. The Vas Deferens, the excretory duct of the testicle, is about two feet in length, and may be traced upward from the epididymis to the under sur- face of the base of the bladder, where it unites with the duct of the vesicula seminalis, to form the ejaculatory duct. The Vesiculse Seminales are two lobulated, pyriform bodies, about two inches in length, situated on the under surface of the bladder. They have an external fibrous coat, a middle muscular coat, and an in- ternal mucous coat, covered by epithelium, which secretes a mucous fluid. The vesiculae seminales serve as reservoirs, in which the seminal fluid is temporarily stored up. The Ejaculatory Duct, about % of an inch in length, opens into the urethra, and is formed by the union of the vasa deferentia and the ducts of the vesiculae seminales. The Prostate Gland surrounds the posterior extremity of the urethra, and opens into it by from twenty to thirty openings, the orifices of the pros- DEVELOPMENT OF ACCESSORY STRUCTURES. 155 tatic tubules. The gland secretes a fluid which forms part of the semen, and assists in maintaining the vitality of the spermatozoa. Semen is a complex fluid, made up of the secretions from the testicles, the vesiculse seminales, the prostatic and urethral glands. It is grayish- white in color, mucilaginous in consistence, of a characteristic odor, and somewhat heavier than water. From half a drachm to a drachm is ejacu- lated at each orgasm. The Spermatozoa are peculiar anatomical elements, developed within the seminal tubules, and possess the power of spontaneous movement. The spermatozoa consist of a conoidal head and a long filamentous tail, which is in continuous and active motion ; as long as they remain in the vas deferens they are quiescent, but when free to move in the fluid of the vesiculse seminales, become very active. Origin. The spermatozoa appear at the age of puberty, and are then constantly formed until an advanced age. They are developed from the nuclei of large, round cells contained in the interior of the seminal tubules, as many as fifteen to twenty developing in a single cell. When the spermatozoa are introduced into the vagina, they pass readily into the uterus and through the Fallopian tubes toward the ovaries, where they remain and retain their vitality for a period of from 8 to 10 days. Fecundation is the union of the spermatozoa with the ovum during its passage toward the uterus, and usually takes place in the Fallopian tube, just outside of the womb. After floating around the ovum in an active man- ner, they penetrate the vitelline membrane, pass into the interior of the vitellus, where they lose their vitality, and along with the germinal vesicle entirely disappear. DEVELOPMENT OF ACCESSORY STRUCTURES. Segmentation of the Vitellus. After the disappearance of the spermatozoa and the germinal vesicle there remains a transparent, granular, albuminous substance, in the centre of which a new nucleus soon appears ; this constitutes the parent cell, and is the first stage in the development of the new being. Following this, the vitellus undergoes segmentation; a constriction appears on the opposite sides of the vitellus, which gradually deepens, until the yelk is divided into two segments, each of which has a distinct nucleus and nucleolus ; these two segments undergo a further division into four, the four into eight, the eight into others, and so on, until the entire 156 . HUMAN PHYSIOLOGY. vitellus is divided into a great number of cells, each of which contains a nucleus and nucleolus. The peripheral cells of this "mulberry mass" then arrange themselves so as to form a membrane, and as they are subjected to mutual pressure, assume a polyhedral shape, which gives to the membrane a mosaic appear- ance. The central part of the vitellus becomes filled with a clear fluid. A secondary membrane shortly appears within the first, and the two to- gether constitute the external and internal blastodermic membranes, Germinal Area. At about this period there is an accumulation of cells at a certain spot upon the surface of the blastodermic membranes, which marks the position of the future embryo. This spot, at first circular, soon becomes elongated, and forms \ht primitive trace, around which is a clear space, the area pelludda, which is itself surrounded by a darker region, the area opaca. The primitive trace soon disappears, and the area pellucida becomes guitar-shaped; a new groove, the medullary groove^ now formed, which develops from before backward, and becomes the neural canal. Blastodermic Membranes. The embryo, at this period, consists of three layers, viz.: the external and internal blastodermic membranes, and a middle membrane formed by a genesis of cells from their internal surfaces. These layers are known as the epiblast, mesoblast and hypoblast. The Epiblast gives rise to the central nervous system, the epidermis of the skin and its appendages, and the primitive kidneys. The Mesoblast gives rise to the dermis, muscles, bones, nerves, blood vessels, sympathetic nervous system, connective tissue, the urinary and reproductive apparatus and the walls of the alimentary canal. The Hypoblast gives rise to the epithelial lining of the alimentary canal and its glandular appendages, the liver and pancreas, and the epithelium of the respiratory tract. Dorsal Laminae. As development advances, the true medullary groove deepens, and there arise two longitudinal elevations of the epiblast, the dorsal lamina i one on either side of the groove, which grow u*p, arch over and unite so as to form a closed tube, the primitive central nervous system. The Chorda Dorsalis is a cylindrical rod running almost throughout the entire length of the embryo. It is formed by an aggregation of meso- blastic cells, and situated immediately beneath the medullary groove. Primitive Vertebras. On either side of the neural canal the cells of the mesoblast undergo a longitudinal thickening, which develops and DEVELOPMENT OF ACCESSORY STRUCTURES. 157 extends around the neural canal and the chorda dorsalis, and forms the arches and bodies of the vertebrae. They become divided transversely into four-sided segments. The Mesoblast now separates into two layers ; the external, joining with the epiblast, forms the somatople ure ; the internal, joining with the hypo - blast, forms the splanchnopleure ; the space between them constituting the pleuro-peritoneal cavity. Visceral Laminae. The walls of the pleuro-peritoneal cavity are formed by a downward prolongation of the somatopleure (the visceral lamina], which, as they extend around in front, pinch off a portion of the yelk sac (formed by the splanchnopleure), which becomes the primitive alimentary canal ; the lower portion, remaining outside of the body cavity, forms the umbilical vesicle, which after a time disappears. Formation of Foetal Membranes. The Amnion appears shortly after the embryo begins to develop, and is formed by folds of the epiblast and external layer of the mesoblast, rising up in front and behind, and on each side; these amniotic folds gradually extend over the back of the embryo to a certain point, where they coalesce, and enclose a cavity, the amniotic cavity. The membranous partition between the folds disappears, and the outer layer recedes and becomes blended with the vitelline mem- brane, constituting the chorion, the external covering of the embryo. The Allan tois. As the amnion develops, there grows out from the posterior portion of the alimentary canal a pouch, or diverticulum, the allantois, which carries bloodvessels derived from the intestinal circulation. As it gradually enlarges, it becomes more vascular, and inserts itself be- tween the two layers of the amnion, coming into intimate contact with the external layer. Finally, from increased growth, it completely surrounds the embryo, and its edges become fused together. In the bird, the allantois is a respiratory organ, absorbing oxygen and exhaling carbonic acid ; it also absorbs nutritious matter from the interior of the egg. Amniotic Fluid. The amnion, when first formed, is in close contact with the surface of the ovum ; but it soon enlarges, and becomes filled with a clear, transparent fluid, containing albumen, glucose, fatty matters, urea and inorganic salts. It increases in amount up to the latter period of gestation, when it amounts to about two pints. In the space between the amnion and allantois is a gelatinous material, which is encroached upon, and finally disappears as the amnion and allantois come in contact, at about the fifth month. 158 HUMAN PHYSIOLOGY. The Chorion, the external investment of the embryo, is formed by a fusion of the original vitelline membrane, the external layer of the amnion, and the allantois. The external surface now becomes covered with villous processes, which increase in number and size by the continual budding and growth of club-shaped processes from the main stem, and give to the chorion a shaggy appearance. They consist of a homogeneous granular matter, and are penetrated by branches of the blood vessels derived from the aorta. The presence of villous processes in the uterine cavity is proof positive of the previous existence of a foetus. They are characteristic of the chorion, and are found under no other circumstances. At about the end of the second month the villosities begin to atrophy and disappear from the surface of the chorion, with the exception of those situated at the points of entrance of the foetal blood vessels, which occupy about one-third of its surface, where they continue to grow longer, become more vascular, and ultimately assist in the formation of the placenta ; the remaining two-thirds of the surface loses its villi and blood vessels, and becomes a simple membrane. The Umbilical Cord connects the foetus with that portion of the chorion which forms the foetal side of the placenta. It is a process of the allantois, and contains two arteries and a vein, which have a more or less spiral direction. It appears at the end of the first month, and gradually increases in length, until, at the end of gestation, it measures about twenty inches. The cord is also surrounded by a process of the amnion. Development of the Decidual Membrane. The interior of the uterus is lined by a thin, delicate, mucous membrane, in which are im- bedded immense numbers of tubules, terminating in blind extremities, the uterine tubules. At each period of menstruation the mucous membrane becomes thickened and vascular, which condition, however, disappears after the usual menstrual discharge. When the ovum becomes fecundated, the mucous membrane takes on an increased growth, becomes more hyper- trophied and vascular, sends up little processes, or elevations from its sur- face, and constitutes the decidua vera. As the ovum passes from the Fallopian tube into the interior of the uterus, the primitive vitelline membrane, covered with villosities, becomes entangled with the processes of the mucous membrane. A portion of the decidua vera then grows up on all sides, and encloses the ovum, forming the decidua reflexa, while the viilous processes of the chorion insert them- selves into the uterine tubules, and in the mucous membrane between them. DEVELOPMENT OF ACCESSORY STRUCTURES. 159 As development advances the decidua reflexa increases in size, and at about the end of the fourth month comes in contact with the decidua vera, with which it is ultimately fused. The Placenta. Of all the embryonic structures, the placenta is the most important. It is formed in the third month, and then increases in size until the seventh month, when a retrogressive metamorphosis takes place until its separation during labor, at which time it is of an oval or rounded shape, and measures from seven to nine inches in length, six to eight inches in breadth, and weighs from fifteen to twenty ounces. It is most frequently situated at the upper and posterior part of the inner surface of the uterus. The placenta consists of two portions, a foetal and a maternal. The Feet al portion is formed by the villi of the chorion, which, by devel- oping, rapidly increase in size and number. They become branched and penetrate the uterine tubules, which enlarge and receive their many ramifi- cations. The capillary blood vessels in the anterior of the villi also en- large and freely anastomose with each other. The Maternal portion is formed from that part of the hypertrophied and vascular decidual membrane between the ovum and the uterus, the decidua serotina. As the placenta increases in size, the maternal blood vessels around the tubules become more and more numerous, and gradually fuse together, forming great lakes, which constitute sinuses in the walls of the uterus. As the latter period of gestation approaches, the villi extend deeper into the decidua, while the sinuses in the maternal portion become larger and extend further into the chorion. Finally, from excessive development of the blood vessels, the structures between them disappear, and as their walls come in contact, they fuse together, so that, ultimately, the maternal and foetal blood are only separated by a thin layer of a homogeneous substance. When fully formed, the placenta consists principally of blood vessels inter- lacing in every direction. The blood of the mother passes from the ute- rine vessels into the lakes surrounding the villi ; the blood from the child flows from the umbilical arteries into the interior of the villi ; but there is not at any time an intermingling of blood, the two being separated by a delicate membrane formed by a fusion of the walls of the blood vessels and the walls of the villi and uterine sinuses. The function of the placenta, besides nutrition, is that of a respiratory organ, permitting the oxygen of the maternal blood to pass by osmosis through the delicate placental membrane into the blood of the foetus ; at the same time permitting the carbonic acid and other waste products, the 160 HUMAN PHYSIOLOGY. result of nutritive changes in the foetus, to pass into the maternal blood, and so to be carried to the various eliminating organs. Through the placenta also passes all the nutritious materials of the maternal blood which are essential for the development of the embryo. At about the middle of gestation there develops beneath the decidual membrane a new mucous membrane, destined to perform the functions of the old when it is extruded from the womb, along with the other embryonic structures, during parturition. DEVELOPMENT OF THE EMBRYO. Nervous System. The cerebro-spinal axis is formed within the me- dullary canal by the development of cells from its inner surfaces, which as they increase fill up the canal, and there remains only the central canal of the cord. The external surface gives rise to the dura mater and pia mater. The neural canal thus formed is a tubular membrane ; it termi- nates posteriorly in an oval dilatation, and anteriorly in a bulbous extremity, which soon becomes partially contracted, and forms the anterior, middle and posterior cerebral vesicles, from which are ultimately developed the cerebrum, the corpora quadrigemina, and medulla oblongata, respectively. The anterior vesicle soon subdivides into two secondary vesicles, the larger of which becomes the hemispheres, the smaller, the optic thalami ; the posterior vesicle also divides into two; the anterior becoming the cerebellum, the posterior, the pons Varolii and medulla oblongata. About the seventh week the straight chain of cerebral vesicles becomes curved from behind forward and forms three prominent angles. As devel- opment advances, the relative size of the encephalic masses changes. The cerebrum developing more rapidly than the posterior portion of the brain, soon grows backward and arches over the optic thalami and the tubercula quadrigemina ; the cerebellum overlaps the medulla oblongata. The surface of the cerebral hemispheres.is at first smooth, but at about the fourth month begins to be marked by the future fissures and convolutions. The Eye is formed by a little bud projecting from the side of the anterior vesicle. It is at first hollow, but becomes lined with nervous matter, forming the optic nerve and retina ; the remainder of the cavity is occupied by the vitreous body. The anterior portion of the pouch becomes invaginated and receives the crystalline /ens, which is a product of the epiblast, as is also the cornea. The iris appears as a circular membrane without a central aperture, about the seventh week ; the eyelids are formed between the second and third months. DEVELOPMENT OF THE EMBRYO. 161 The Internal Ear is developed from the auditory vesicle, budding from the third cerebral vesicle; the membranous vestibule appears first, and from it diverticula are given off, which become the semicircular canals and cochlea. The cavity of the tympanum, the Eustachian tube, and the external auditory canal are the remains of the first branchial cleft; the cavity of this cleft being subdivided into the tympanum and external auditory meatus by the membrana tympani. The Skeleton. The chorda dorsalis, the primitive part of the verte- bral column, is a cartilaginous rod situated beneath the medullary groove. It is a temporary structure, and disappears as the true bony vertebrae develop. On either side are the quadrate masses of the mesoblast, the primitive vertebrae, which send processes upward and around the medul- lary groove, and downward and around the chorda dorsalis, forming in these situations the arches and bodies of the future vertebrae. More externally the outer layer of the mesoblast and epiblast arch downward and forward, forming the ventral laminae, in which develop the muscles and bones of the abdominal walls. The true cranium is an anterior development of the vertebral column, and consists of the occipital, parietal and frontal segments, which corre- spond to the three cerebral vesicles. The base of the cranium consists, at this period, of a cartilaginous rod on either side of the anterior extremity of the chorda dorsalis, in which three centres of ossification appear, the basi-occipital, the basi-sphenoidal, and the pre-sphenoidal. They ultimately develop into the basilar process of the occipital bone and the body of the sphenoid. The entire skeleton is at first either membranous or cartilaginous. At the beginning of the second month centres of ossification appear in the jaws and clavicle; as development advances, the ossific points in all the future bones extend, until ossification is completed. The limbs develop from four little buds projecting from the sides of the embryo, which, as they increase in length, separate into the thigh, leg and foot, and the arm, forearm and hand ; the extremities of the limbs undergo subdivision, to form the fingers and toes. Face and Visceral Arches. In the facial and cervical regions the visceral laminae send up three processes, the visceral arches, separated by clefts, the visceral clefts. The first, or the mandibular arches, unite in the median line to form the lower jaw, and superiorly form the malleus. A process jutting from its base grows forward, unites with the fronto-nasal process growing from 162 HUMAN PHYSIOLOGY. above, and forms the upper jaw. When the superior maxillary processes* fail to unite, there results the cleft-palate deformity ; if the integument also fails to unite, there results the hare-lip deformity. The space above the mandibular arch becomes the mouth. The second arch develops the incus and stapes bones, the styloid process and ligament, and the lesser cornu of the hyoid bone. The cleft between the first and second arches partially closes up, but there remains an open- ing at the side which becomes the Eustachian tube, tympanic cavity, and external auditory meatus. The third arch develops the body and greater cornu of the hyoid bone. Alimentary Canal and its Appendages. The alimentary canal is formed by a pinching off of the yelk sac by the visceral plates as they grow downward and forward. It consists of three distinct portions, the fore gut, the hind gut, and the central part, which communicates for some time with the yelk sac. It is at first a straight tube, closed at both extremities, lying just beneath the vertebral column. The canal gradually increases in length, and becomes more or less convoluted ; at its anterior portion two pouches appear, which become the cardiac and pyloric extremities of the stomach. At about the seventh week the inferior extremity of the intestine is brought into communication with the exterior, by an opening, the anus. Anteriorly the mouth and pharynx are formed by an involution of epiblast, which deepens until it communicates with the fore gut. The Liver appears as a slight protrusion from the sides of the alimen- tary canal, about the end of the first month ; it grows very rapidly, attains a large size, and almost fills up the abdominal cavity. The hepatic cells are derived from the intestinal epithelium, the vessels and connective tissue from the mesoblast. The Pancreas is formed by the hypoblastic membrane. It originates in two small ducts budding from the duodenum, which divide and subdivide, and develop the glandular structure. The Lungs are developed from the anterior part of the oesophagus. At first a small bud appears, which, as it lengthens, divides into two branches ; secondary and tertiary processes are given off these, which form the bron- chial tubes and air cells. The lungs originally extended into the abdomi- nal cavity, but became confined to the thorax by the development of the diaphragm. The Bladder is formed by a dilatation of that portion of the allantois remaining within the abdominal cavity. It is at first pear-shaped, and communicates with the intestine, but later becomes separated, and opens DEVELOPMENT OF THE EMBRYO. 163 exteriorly by the urethra. It is attached to the abdominal walls by a rounded cord, the urachus, the remains of a portion of the allantois. Genito- urinary Apparatus. The Wolffian bodies appear about the thirtieth day, as long hollow tubes running along each side of the primi- tive vertebral column. They are temporary structures, and are sometimes called the primordial kidneys. The Wolffian bodies consist of tubules which run transversely and are lined with epithelium ; internally they become invaginated to receive tufts of blood vessels ; externally they open into a common excretory duct, the duct of the Wolffian body, which unites with the duct of the opposite body, and empties into the intestinal canal at a point opposite the allantois. On the outer side of the Wolffian body there appears another duct, the duct of Miiller, which also opens into the intestine. Behind the Wolffian bodies are developed the structures which become either the ovaries or testicles. In the development of the female, the Wolffian bodies and their ducts disappear ; the extremities of the Miillerian ducts dilate and form the fimbriated extremity of the Fallopian tubes, while the lower portions coalesce to form the body of the uterus and vagina, which now separate themselves from the intestine. In the development of the male, the Miillerian ducts atrophy, and the ducts of the Wolffian body ultimately form the epididymis and vas deferens. About the seventh month the testicles begin to descend, and by the ninth month have passed through the abdominal ring into the scrotum. The Kidneys are developed out of the Wolffian bodies. They consist of little pyramidal lobules, composed of tubules which open at the apex into the pelvis. As they pass outward they become convoluted and cup-shaped at their extremities, receive a tuft of blood vessels, and form the Mal- pighian bodies. The ureters are developed from the kidneys, and pass downward to be connected with the bladder. The Circulatory Apparatus assumes three different forms at different periods of life, all having reference to the manner in which the embryo receives nutritious matter and is freed of waste products. The Vitelline circulation appears first and absorbs nutritious material from the vitellus. It is formed by blood vessels which emerge from the body and ramify over a portion of the vitelline membrane, constituting the area vasculosa. The heart, lying in the median line, gives off two arches which unite to form the abdominal aorta, from which two large arteries are given off, passing into the vascular area ; the venous blood is returned 164 HUMAN PHYSIOLOGY. by veins which enter the heart. These vessels are known as the omphalo- mesenteric arteries and veins. The vitelline circulation is of short dura- tion in the mammals, as the supply of nutritious matter in the vitellus soon becomes exhausted. The Placental circulation becomes established when the blood vessels in the allantois enter the villous processes of the chorion and come into close relationship with the maternal blood vessels. This circulation lasts during the whole of intra-uterine life, but gives way at birth to the adult circulation, the change being made possible by the development of the circulatory apparatus. The Heart appears as a mass of cells coming off from the anterior por- tion of the intestine ; its central part liquefies, and pulsations soon begin. The heart is at first tubular, receiving posteriorly the venous trunks and giving off anteriorly the arterial trunks. It soon becomes twisted upon itself, so that the two extremities lie upon the same plane. The heart now consists of a single auricle and a single ventricle. A septum growing from the apex of the ventricle divides it into two cavities, a right and a left. The auricles also become partly separated by a septum which is perforated by the foramen ovale. The arterial trunk becomes separated by a partition, into two canals, which become, ultimately, the aorta and pulmonary artery. The auricles are separated from the ventri- cles by incomplete septa, through which the blood passes into the ventricles. Arteries. The aorta arises from the cephalic extremity of the heart and divides into two branches which ascend, one on each side of the intestine, and unite posteriorly to form the main aorta ; posteriorly to these first aortic arches four others are developed, so that there are five altogether running along the visceral arches. The two anterior soon disappear. The third arch becomes the internal carotid and the external carotid ; a part of the fourth arch, on the right side, becomes the subclavian artery, and the remainder atrophies and disappears, but on the left side it enlarges and becomes the permanent aorta ; the fifth arch becomes the pulmonary artery on the left side. The communication between the pulmonary artery and the aorta, the ductus arteriosus, disappears at an early period. Veins. The venous system appears first as two short, transverse veins , the canals of Cuvier, formed by the union of the vertebral veins and the cardinal veins, which empty into the auricle. The inferior vena cava is formed as the kidneys develop, by the union of the renal veins, which, in a short time, receive branches from the lower extremities. The subclavian veins join the jugular as the upp^r extremities develop. The heart descends in the thorax, and the canals of Cuvier become oblique ; they shortly DEVELOPMENT OF THE EMBRYO. 165 % communicate by a transverse duct, which ultimately becomes the left innominate vein. The left canal of Cuvier atrophies and becomes a fibrous cord. A transverse branch now appears, which carries the blood from the left cardinal vein into the right, and becomes the vena azygos minor ; the right cardinal vein becomes the vena azygos major. Circulation of Blood in the Foetus. The blood returning from the placenta, after having received oxygen, and being freed from carbonic acid, is carried by the umbilical vein to the under surface of the liver ; here a portion of it passes through the ductus venosus into the ascending vena cava, while the remainder flows through the liver, and passes into the vena cava by the hepatic veins. When the blood is emptied into the right auricle, it is directed by the Eustachian valve, through the foramen ovale, into the left auricle, thence into the left ventricle, and so into the aorta to all parts of the system. The venous blood returning from the head and upper extremities is emptied, by the superior vena cava, into the right auricle, from which it passes into the right ventricle, and thence into the pulmonary artery. Owing to the condition of the lung, only a small por- tion flows through the pulmonary capillaries, the greater part passing through the ductus arteriosus, which opens into the aorta at a point below the origin of the carotid and subclavian arteries. The mixed blood now passes down the aorta to supply the lower extremities, but a portion of it is directed, by the hypogastric arteries, to the placenta, to be again oxygenated. At birth, the placental circulation gives way to the circulation of the adult. As soon as the child begins to breathe, the lungs expand, blood flows freely through the pulmonary capillaries, and the ductus arteriosus begins to contract. The foramen ovale closes about the tenth day. The umbilical vein, the ductus venosus, and the hypogastric arteries become impervious in several days, and ultimately form rounded cords. 166 HUMAN PHYSIOLOGY. TABLE OF PHYSIOLOGICAL CONSTANTS. Mean height of male, 5 feet 6^ inches ; of female, 5 feet 2 inches. Mean weight of male, 145 pounds ; of female, 121 pounds. Number of chemical elements in the human body; from 16 to 18. Number of proximate principles in the human body ; about 100. Amount of water in the body weighing 145 pounds; 108 pounds. Amount of solids in the body weighing 145 pounds; 36 pounds. Amount of food required daily; 16 ounces meat, 19 ounces of bread, 3^ ounces of fat, 52 ounces of water. Amount of saliva secreted in 24 hours ; about 3^ pounds. / Function of saliva ; converts starch into glucose. Active principle of saliva ; ptyalin. Amount of gastric juice secreted in 24 hours; from 8 to 14 pounds. Functions of gastric juice ; converts albumen into albuminose. Active principles of gastric juice ; pepsin and hydrochloric acid. Duration of digestion ; from 3 to 5 hours. Amount of intestinal juice secreted in 24 hours; about I pound. Function of intestinal juice ; converts starch into glucose. Amount of pancreatic juice secreted in 24 hours; about i^ pounds. Active principles of pancreatic juice ; pancreatin and trypsin. C I. Emulsifies fats. Functions : \ 2. Converts albumen into albuminose. ( 3. Converts starch into glucose. Amount of bile poured into the intestines daily ; about 2J^ pounds. f i. Assists in the emulsification of fats. -p, . j 2. Stimulates the peristaltic movements. 1 3. Prevents putrefactive changes in the food. L 4. Promotes the absorption of the fat. Amount of blood in the body ; from 16 to 18 pounds. Size of red corpuscles ; -3 ^Vo f an i ncn - Size of white corpuscles ; ^W ^ an i ncn - Shape of red corpuscles ; circular biconcave disks. Shape of white corpuscles ; globular. Number of red corpuscles in a cubic millimetre of blood (the cubic ^ of an inch) ; 5,000,000. TABLE OF PHYSICAL CONSTANTS. 167 Function of red corpuscles ; to carry oxygen from the lungs to the tissues. Frequency of the heart's pulsations per minute ; 72, on the average. Velocity of the blood movement in the arteries; about 16 inches per second. Length of time required for the blood to make an entire circuit of the vascular system ; about 20 seconds. Amount of air passing in and out of the lungs at each respiratory act ; from 20 to 30 cubic inches. Amount of air that can be taken into the lungs on a forced inspiration ; no cubic inches. Amount of reserve air in the lungs after an ordinary expiration ; 100 cubic inches. Amount of residual air always remaining in the lungs ; about 100 cubic inches. Vital capacity of the lungs ; 230 cubic inches. Entire volume of air passing in and out of the lungs in 24 hours ; about 400 cubic feet. Composition of the air; nitrogen, 79.19, oxygen, 20.81, per 100 parts. Amount of oxygen absorbed in 24 hours; 1 8 cubic feet. Amount of carbonic acid exhaled in 24 hours ; 14 cubic feet. Temperature of the human body at the surface ; 98 1 6 ^ F. Amount of urine excreted daily ; from 40 to 50 ounces. Amount of urea excreted daily; 512 grains. Specific gravity of urine ; from i.oio to 1.0*5. Number of spinal nerves; 31 pairs. '' r Number of roots of origin; two; ist, anterior, motor; 2d, posterior, sensory. Rate of transmission of nerve force ; about 100 feet per second. Number of cranial nerves ; 12 pairs. f i. Olfactory, or ist pair. 2. Optic, or 2d pair. Nerves of special sense : 3- Auditory, or 8th pair. I 4. Chorda tympani for anterior % of tongue. Branches of glosso-pharyngeal, or 8th pair, for posterior y of tongue. Motor nerves to eyeball and accessory structures ; motor oculi, or 3d pair j pathetic, or 4th pair ; abducens, or 6th pair. Motor nerves to facial muscles ; portio dura, facial, or 7th pair. Motor nerve to tongue; hypoglossal or I2th pair. Motor nerve to laryngeal muscles ; spinal accessory or nth pair. Sensory nerve of the face ; trifacial or 5th pair. 168 HUMAN PHYSIOLOGY. Sensory nerve of the pharynx ; glosso-pharyngeal or 9th pair. Sensory nerves of the lungs, stomach, etc.; pneumogastric or roth pair. Length of spinal cord; i6to 1 8 inches, weight i^ ounces. Point of decussation of motor fibres ; at the medulla oblongata. Point of decussation of sensory fibres ; throughout the spinal cord. Function of antero-lateral columns of spinal cord ; transmit motor im- pulses from the brain to the muscles. Functions of the posterior columns ; assist in the coordination of mus- cular movements. Functions of the medulla oblongata ; controls the functions of insaliva- tion, mastication, deglutition, respiration, circulation, etc. Functions of the corpora quadrigemina ; physical centres for sight. Functions of the corpora striata ; centres for motion. Functions of the optic thalami ; centres for sensation. Function of the cerebellum ; centre for the coordination of muscular movement. Function of the cerebrum ; centre for intelligence, reason and will. Centre for articulate language ; 3d frontal convolution on left side of cerebrum. Number of coats to the eye ; three ; 1st, cornea and sclerotic ; 2d, choroid ; 3d, retina. Function of iris ; regulates the amount of light entering the eye. Function of crystalline lens ; refracts the rays of light so as to form an image on the retina. Function of retina ; receives the impressions of light. Function of membrana tympani ; receives and transmits waves of sound to internal ear. Function of Eustachian tube ; regulates the passage of air into and from the middle ear. Function of semicircular canals ; assist in maintaining the equipoise of the body. Function of the cochlea ; appreciates the shades and combinations of musical tones. Size of human ovum ; T J^ of an inch in diameter. Size of spermatozoa ; ^^ o f an inch in length. Function of the placenta ; acts as a respiratory and digestive organ for the foetus. Duration of pregnancy ; 280 days. TABLE SHOWING RELATION OF WEIGHTS AND MEASURES OF THE METRIC SYSTEM TO APPROX- IMATE WEIGHTS AND MEASURES OF THE U. S. One Myriametre = One Kilometre = One Hectometre = One Decametre One METRE One Decimetre = One Centimetre = One Millimetre = One Myriagramme One Kilogramme One Hectogramme One Decagramme One GRAMME MEASURES OF LENGTH. 10,000 metres 1,000 " = 100 " 10 " f the ten millionth part of a -j quarter of the Meridian of ( the Earth the tenth part of one metre J the one hundredth part of > \ one metre j f the one thousandth part ofl 1 one metre f WEIGHTS. 10,000 grammes 1,000 " 100 " : 32800. feet. = 3280. " = 328.0 " = 32.80 39'368 inches. = 3.936 = -393(1) " 39 (A) " = 26^ pounds Troy. One Decigramme One Centigramme One Milligramme One Myrialitre One Kilolitre One Hectolitre One Decalitre One LITRE One Decilitre One Centilitre One Millilitre -f: f the weight of a cubic centi- \ \ metre of water at 4 C. j the tenth part of one gramme f the hundredth part of one 1 \ gramme / ( the thousandth part of one 1 \ gramme / MEASURES OF CAPACITY 10 cubic Metres or the ^ measure of 10 Milliers of V ( water J _ ? I cubic Metre or the meas- \ _ ~ \ ure of i Millier of water / ~~ f 100 cubic Decimetres orS = -j the measure of I Quintal > = ( of water J f 10 cubic Decimetres = -j the measure of i Myria ( gramme of water C i cubic Decimetre or the 1 = ! measure of I Kilogramme > [ of water T 100 cubic Centimetres or = -j the measure of I Hecto- ( gramme of water {10 cubic Centimetres or the measure of I Deca- gramme of water {I cubic Centimetre or the ~| measure of I gramme of V water J = 3^4 ounces 2*4 drachms " = 15434 grains. = 1-543 ( 11 A] " = - J 54 (i) " = -015 (A) " 2600. gallons. 260. " 26. " "I na- > = 2.6 " 2.1 pints. 3.3 ounces. 2.7 drachms. 16.2 minims. INDEX. ABDUCENS NERVE 94 " Aberration, chromatic 142 ' spherical 142 Absorption 36 by the lacteals 39 by the blood vessels 36 of oxygen in respiration 59 Accommodation of the eye 142 Adipose tissue, uses of in the body 12 Adult circulation, establishment of at birth 165 Air, atmospheric, composition of. 59 amount exchanged in respira- tion 58 ' changes in during respiration... 59 Albumen, uses of in the body 13 Albuminoid substances 13 Alcohol, action of. 21 Alimentary principles, classification of 19 albuminous principles 19 saccharine principles 19 oleaginous principles 19 inorganic principles 20 Alimentary canal, development of. 162 Allantois, development and function of 157 Amnion, formation of. 157 Animal heat-, 61 Anterior columns of spinal cord no Area, germinal 156 Arteries, properties of. 51 Asphyxia 60 Astigmatism 135 Axis, cerebro-spinal 104 cylinder of nerves 84 RILE 77 ^^ Bladder, urinary 72 Blastodermic membranes 148 Blood 41 composition of plasma 42 1 coagulation of. 45 coloring matter of. 44 changes in, during respiration.. 60 circulation of 47 rapidity of flow in arteries 52 rapidity of flow in capillaries... 52 pathological conditions of. 47 corpuscles 43 origin of. 44 - pressure 51 Burdach, column of. 106 (CANALS OFCUVIER 164 ^^ Capillary blood vessels .*. 52 Capsule, internal 120 external 120 Caudate nucleus 120 Cells, structure of. 16 manifestations of life by 16 of anterior horns of gray matter 107 Centre for articulate language 128 Cerebrum 123 fissures and convolutions 123 functions of. 126 localization of functions 128 motor area of. 128 special centres of. 128 Cerebellum 121 forced movements of. 122 Cerebral vesicles of embryo 160 Chemical composition of human body 10 elements, proximate quantity of in body 15 Chorda dorsalis , 156 tympani nerve, course and func- tion of.. 171 Chorion 157 Chyle , 39 Ciliary muscle 138 Circulation of blood 47 Claustrum 120 Cochlea 146 Columns of spinal cord 106 Corium 80 Corpora Wolffiana 163 quadrigemina 118 Corpus luteum 152 striatum 119 Corti, organ of 147 Cranial nerves 91 Crura cerebri 118 Crystalline lens 140 T)ECIDUAL MEMBRANE 158 ^^ Decussation of motor and sen- sory fibres 109 Deglutition 27 nervous circle of. 116 Development of accessory structures of embryo 155 Digestion 23 Ductus arteriosus 164 venosus 164 172 INDEX. PAGE 144 Electrotonus ............................ 90 Embryo, development of ................ ... 160 Endolymph ...................................... 147 Epidermis ........................................ 80 Epididymis ...................................... 154 Epiglottis ........................................ 27 Eustachian tube ............................. 145 Excretion ........................................ 69 Eye ................................................ 137 - refracting apparatus of. .......... 141 - blind spot of ........................... 141 PAGE Heart, work done by 49 course of blood through 48 influence of nervous system upon 50 Hyaloid membrane 14 NERVE ...................... 97 ^ - paralysis, symptoms of... 98 Fallopian tubes ................................ 151 Faeces ............................................ 35 Fat, uses of in the body .................... 13 Female organs of generation .............. 151 Fissures and convolutions of brain ..... 123 Food .............................. ... .............. 18 - percentage composition of. ...... 22 - daily amount required ............. 22 - albuminous principles of ......... 20 - saccharine principles of. ......... 20 - oleaginous principles of. ........ ., 20 - inorganic principles of ............ 19 Fovea centralis .......... . ..................... 141 GALVANIC CURRENTS, EF- fect on nerves Ganglia ophthalmic Gasserian spheno-palatine otic sub-maxillary semi-lunar. Hypermetropia 142 Hypoglossal nerve 104 TNCUS BONE 144 * Ingesta and egesta, comparison of in 24 hours 22 Insalivation 25 nervous circle of. 26 Inspiration, movements of thorax in... 56 Internal capsule - results of injury to Intestinal juice.. Iris.. 38 Island of Reil 25 - action of.. T^IDNEYS 7 ** excretion of urine by 73 LABYRINTH OF INTERNAL ear 146 function of cochlea 148 function of semicircular canals.. 146 Language, articulate, centre for 128 Larynx 148 Lateral columns of spinal cord 106 Laws of muscular contraction 91 Laxator tympani muscle 145 Lens, crystalline 140 Li me phosphate Gases of the intestine condition of, in blood Gastric juice action of. Generation, male organs of. female organs of , Globules of the blood - of the lymph. 130 35 60 29 3 154 15* 43 38 72 99 57 79 78 106 151 83 TJAIR 80 ** Haemoglobin 44 Hearing, sense of. 144 Heart 47 valves of 47 sounds of 48 influence of pneumogastric nerve upon 50 ganglia of. 50 force exerted by left ventricle... 49 9 1 84 130 95 130 130 , 130 Liver. Glomeruli of the kidneys Glosso-phary ngeal nerve Glottis, respiratory movements of Glycogen Glycogenic function of liver Goll, column of. Graafian follicles Gray matter of nervous system 76 - secretion of bile by 77 - glycogenic function of. 77 - elaboration of blood 78 -cells 76 Localization of functions in cerebrum.. 128 Lungs 54 changes in blood while passing through 60 Lymph 38 Lymphatic glands 38 vessels, origin and course of 37 MAMMARY GLANDS ............ 66 Malleus bone .......................... 144 Mastication ...................................... 24 - nervous circle of ..................... 24 -- muscles of ............................. 24 Medulla oblongata ........................... i*4 - properties and functions of ----- 115 Membrana basilaris ......................... 147 tympani Menstruation ................................... J 5 2 Middle ear ....................................... 144 Milk.. 67 Motor centres of cerebrum 128 Muscles, properties of 88 Myopia *4 2 INDEX. 173 N PAGE ERVE, OLFACTORY 92 optic 92 motor oculi 93 pathetic 94 trigeminal 95 abducens 94 facial 97 auditory 99 glosso-pharyngeal 99 pneumogastric 100 spinal accessory 102 hypoglossal 104 cells, structure of 83 fibres, terminations of 86 force, rate of transmission of... 88 roots, function of anterior and posterior 85 Nerves, centrifugal and centripetal.... 87 cranial 92 decussation of motor and sen- sory 109 vaso-motor 116 properties and functions of 87 spinal 87 Nervous system 83 white and gray matter of. 83 cerebro-spinal 83 - sympathetic 130 Nucleus caudatus 120 lenticularis 120 QLFACTORY NERVES 92 ^^ Ophthalmic ganglion 123 Optic nerves 92 thalamus 120 function of 120 Organs of Corti 148 Otic ganglion 130 Ovaries 151 Ovum , 151 discharge of from the ovary 152 Oxygen, absorption of by haemoglobin 59 pACINIAN CORPUSCLES 86 * Pancreatic juice 32 Patheticus nerve 93 Peptones 30 Perilymph 146 Perspiration 81 Petrosal nerves, large and small 97 Phonation 148 Physiology, definition of 9 Placenta, formation and function of... 159 Pneumogastric nerve 100 Pons varolii 117 Portal vein 37 Posterior columns of spinal cord 106 - functions of no Prehension 23 Presbyopia 143 Pressure of blood in arteries 51 Proximate principles n inorganic n organic, non-nitrogenized 12 organic, nitrogenized 13 of waste 15 PAGE Proximate quantity of chemical ele- ments in body 15 Ptyalin 26 Pulse 52 Pyramidal tracts 106 RED CORPUSCLES OF blood 43 Reflex movements of spinal cord in action, laws of. 112 Reproduction 151 Respiration 54 movements of 56 nervous mechanism of 57 types of. 58 nervous circle of. 117 OALIVA 25 ^ Sebaceous glands 81 Secretion 63 Semi-circular canals 146 Semen 155 Sight, sense of. 137 Skin 79 relative sensibility of 133 appendages of 80 Smell, sense of 136 Sounds of heart 48 Spermatozoa 155 Spheno-palantine ganglion 130 Spinal accessory nerve 102 Spinal cord 106 membranes of. 105 structure of white matter 106 structure of gray matter 107 properties of. 109 function of as a conductor no as an independent centre in decussation of motor and sen- sory fibres 109 reflex action of. in special centres of. 112 paralysis, from disease of. 113 nerves, origin of 107 course of anterior and posterior roots of. 107 Spleen 68 Stapes bone 145 Starvation, phenomena of. 18 Stomach 27 Structural composition of the body 15 Submaxillary ganglion 130 Sugar, uses of in the body 12 Supra-renal capsules 69 Sudoriparous glands 81 Sympathetic nervous system 130 properties and functions of. 131 , SENSE OF 134 nerve of 135 Tensor tympani muscle 145 Testicles 154 Thoracic duct 38 Thorax, enlargement of in inspiration 56 174 INDEX. Tissues, classification of 17 Tongue 134 motor nerve of. 135 sensory nerve of. 135 Touch, sense of. 133 Turck column 106 UMBILICAL CORD 158 Urea 75 Uric acid 75 Urine 74 composition of. 74 average quantity of constitu- ents secreted daily 74 Urination, nervous mechanism of. 73 Uterus 152 WAPOR, WATERY, O F *' v breath 60 Vascular glands 68 system, development of. 163 Vaso-motor nerves, origin of. , ... 116 Veins Vesiculse seminales 154 Vision, psychical centre for 129 physical centre for n Vital capacity of lungs 59 Vocal cords 148 Voice 148 XX7ATER, AMOUNT OF IN vv body ii Wolffian bodies 163 CATALOGUE No. 7. NOVEMBER, 1888. A CATALOGUE OF . BOOKS FOR STUDENTS. CONTENTS. PAGES New Series of Manuals, 2,3,4,5 Miscellaneous, . PAGES 10 Obstetrics. . IO Biology, ii Pathology, . II Chemistry, . Children's Diseas s, 6 Pharmacy, Physical Diagnosis, 13 ir Dentistry, Dictionaries, 8 Physiology, . Practice of Medicine, ii 12 Eye Diseases, Electricity, . Gynaecology, 8 9 10 Prescription Books, PQuiz-Compends? Skin Diseases, 12 16 Histology, ii 13 Hygiene, 9 Therapeutics, 9 Materia Medica, 9 Throat, 14 Medical Briefs, Medical Jurisprud ence i5 9 Urine and Urinary Organs, 14 Venereal Diseases, . . 14 PUBLISHED BY P. BLAKISTON, SON & CO., Medical Booksellers, Importers and Publishers. LARGE STOCK OF ALL STUDENTS' BOOKS, AT THE LOWEST PRICES. 1012 Walnut Street, Philadelphia. *#* For sale by all Booksellers, or any book will be sent by mail, postpaid, upon receipt of price. Catalogues of books on all branches of Medicine, Dentistry, Pharmacy, etc., supplied upon application. "An excellent Series of Manuals." Archives of Gynaecology. A NEW SERIES OF STUDENTS' MANUALS On the various Branches of Medicine and Surgery. Can be used by Students of any College. Price of each, Handsome Cloth, $3.00. Full Leather, $3.50. The object of this series is to furnish good manuals for the medical student, that will strike the medium between the compend on one hand and the prolix text- book on the other to contain all that is necessary for the student, without embarrassing him with a flood of theory and involved statements. They have been pre- pared by well-known men, who have had large experience as teachers and writers, and who are, therefore, well informed as to the needs of the student. Their mechanical execution is of the best good type and paper, handsomely illustrated whenever illustrations are of use, and strongly bound in uniform style. Each book is sold separately at a remarkably low price, and the immediate success of several of the volumes shows that the series has met with popular favor. No. 1. SURGERY. 236 Illustrations. A Manual of the Practice of Surgery. By WM. J. WALSHAM, M.D., Asst. Surg. to, and Demonstrator of Surg. in, St. Bartholomew's Hospital, London, etc. 228 Illustrations. Presents the introductory facts in Surgery in clear, precise language, and contains all the latest advances in Pathology, Antiseptics, etc. " It aims to occupy a position midway between the pretentious manual and the cumbersome System of Surgery, and its general character may be summed up in one word practical." The Medi- cal Bulletin. " Walsham, besides being an excellent surgeon, is a teacher in its best sense, and having had very great experience in the preparation of candidates for examination, and their subsequent professional career, may be relied upon to have carried out his work successfully. Without following out in detail his arrange- ment, which is excellent, we can at once say that his book is an embodiment of modern ideas neatly strung together, with an amount of careful organization well suited to the candidate, and, indeed, to the practitioner." British Medical Journal. Price of each Book, Cloth, $3.00. Leather, $3.50. THE NEW SERIES OF MANUALS. No. 2. DISEASES OF WOMEN. 13O Illus. The Diseases of Women. By DR. F. WINCKEL, Professor of Gynaecology and Director of the Royal University Clinic for Women, in Munich. Translated from the German by DR. J. H. WILLIAMSON, Resident Physician Allegheny General Hospital, Allegheny, Penn'a, under the supervision of, and with an intro- duction by, Theophilus Parvin, M.D., Professor of Obstetrics and Diseases of Women and Children in Jefferson Medical College. Illustrated by 132 fine Engravings on Wood, most of which are new. " The book will be a valuable one to physicians, and a safe and satisfactory one to put into the hands of students. It is issued in a neat and attractive form, and at a very reasonable price." Boston Medical and Siirgl. Journal, No. 3. OBSTETRICS. 227 Illustrations. A Manual of Midwifery. By ALFRED LEWIS GALABIN, M.A., M.D., Obstetric Physician and Lecturer on Mid- wifery and the Diseases of Women at Guy's Hospital, London; Examiner in Midwifery to the Conjoint Examining Board of England, etc. With 227 Illus. " This manual is one we can strongly recommend to all who desire to study the science as well as the practice of midwifery. Students at the present time not only are expected to know the principles of diagnosis, and the treatment of the various emergen- cies and complications that occur in the practice of midwifery, but find that the tendency is for examiners to ask more questions relating to the science of the subject than was the custom a few years ago. * * * The general standard of the manual is high ; and wherever the science and practice of midwifery are well taught, it will be regarded as one of the most important text-books on the subject." London Practitioner. No. 4. PHYSIOLOG-Y. Third Edition. 321 ILLUSTRATIONS AND A GLOSSARY. A Manual of Physiology. By GERALD F. YEO, M.D., F.R.C.S., Professor of Physiology in King's College, London. 321 Illustrations and a Glossary of Terms. Third American from second English Edition, revised and improved. 758 Pages. This volume was specially prepared to furnish students with a new text-book of Physiology, elementary so far as to avoid theories which have not borne the test of time and such details of methods as are unnecessary for students in our medical colleges. While endeavoring to save the student from doubtful and erroneous doctrines, great care has been taken not to omit any important facts that are necessary to an acquirement of a clear idea of the Price of each Book, Cloth, $3.00. Leather, $3.50. THE NEW SERIES OF MANUALS. principles of Physiology. Such subjects as are useful in the practice of medicine and surgery are treated more fully than those which are essential only to an abstract physiological knowledge. ' ' The brief examination I have given it was so favorable that I placed it in the list of text-books recommended in the circular of the University Medical College." Prof. Le^vis A. Stimson, M.D., 57 East 33d Street, New York. No. 5. POTTER'S MATBRIA MEDIC A, PHARMACY AND THERAPEUTICS. OVER 600 PRESCRIPTIONS, FORMULAE, ETC. A Handbook of Materia Medica, Pharmacy and Therapeutics including the Physiological Action of Drugs, Special Therapeutics of Diseases, Official and Extemporaneous Pharmacy, etc., etc. By SAM'L O. L. POTTER, M.A., M.D., Professor of the Practice of Medicine in Cooper Medical College, San Francisco, Late A. A. Surg., U. S. A., Author of the " Quiz. . Compends" of Anatomy and Materia Medica, etc. This book contains many unique features of style and arrange- ment ; no time or trouble has been spared to make it most complete and yet concise in all its parts. It contains many prescriptions of practical worth, a great mass of facts conveniently and concisely put together, also many tables, dose lists, diagnostic hints, etc., all rendering it the most complete manual ever published. ft Dr. Potter's handbook will find a place, and a very important one, in our colleges and the libraries of our practitioners." N. Y. Medical Journal. No. 6. DISEASES OF CHILDREN. A Manual. By J. F. GOODHART, M.D., Phys. to the Evelina Hospital for Children ; Asst. Phys. to Guy's Hospital, London. American Edition. Edited by Louis STARR, M.D., Clinical Prof, of Dis. of Children in the Hospital of the Univ. of Pennsylvania, and Physician to the Children's Hospital, Phila. Containing many new Prescriptions, a list of over 50 Formulae, conforming to the U. S. Pharmacopoeia, and Directions for making Artificial Human Milk, for the Artificial Digestion of Milk, etc. "As it is said of some men, so it might be said of some books, that they are 'born to greatness.' This new volume has, we believe, a mission, particularly in the hands of the younger members of the profession. In these days of prolixity in medical literature, it is refreshing to meet with an author who knows both what to say and when he has said it. The work of Dr. Goodhart Price of each Book, Cloth, $3.00. Leather, $3.50. THE NEW SERIES OF MANUALS. (admirably conformed, by Dr. Starr, to meet American require- ments) is the nearest approach to clinical teaching without the actual presence of clinical material that we have yet seen." New York Medical Record. No. 7. PRACTICAL THERAPEUTICS. FOURTH EDITION, WITH AN INDEX OF DISEASES. Practical Therapeutics, considered with reference to Articles of the Materia Medica. Containing, also, an Index of Diseases, with a list of the Medicines applicable as Remedies. By EDWARD JOHN WARING, M.D., F.R.C.P. Fourth Edition. Rewritten and Re- vised. By DUDLEY W. BUXTON, M.D., Asst. to the Prof, of Medicine at University College Hospital. " We wish a copy could be put in the hands of every Student or Practitioner in the country. In our estimation, it is the best book of the kind ever written." N. Y. Medical Journal. No. 8. MEDICAL JURISPRUDENCE AND TOXICOLOGY. New Ed. By John J. Reese, M.D., Professor of Medical Jurispru- dence and Toxicology in the University of Pennsyl- vania ; President of the Medical Jurisprudence Society of Phila. ; 2d Edition, Revised and Enlarged. "This admirable text-book." Atner. Jour, of Med. Sciences. " We lay this volume aside, after a careful 'perusal of its pages, with the profound impression that it should be in the hands of every doctor and lawyer. It fully meets the wants of all students He has succeeded in admirably condensing into a handy volume all the essential points." Cincinnati Lancet and Clinic. No. 9. ORG-ANIC CHEMISTRY. Or the Chemistry of the Carbon Compounds. By Prof. VICTOR VON RICHTER, University of Breslau. Au- thorized translation, from the Fourth German Edition. By EDGAR F. SMITH, M.A., PH.D. ; Prof, of Chemistry in University of Pennsylvania; Member of the Chem. Socs. of Berlin and Paris. " I must say that this standard treatise is here presented in a remarkably compendious shape." y. W. Holland, M.D., Professor of Chemistry, Jej^er son Medical College, Philadelphia. " This work brings the whole matter, in simple, plain language, to the student in a clear, comprehensive manner. The whole method of the work is one that is more readily grasped than that of older and more famed text-books, and we look forward to the time when, to a great extent, this work will supersede others, on the score of its better adaptation to the wants of both teacher and student." Pharmaceutical Record. Price of each Book, Cloth, $3.00. Leather, $3.50. 6 STUDENTS' TEXT-BOOKS AND MANUALS. ANATOMY. Holden's Anatomy. A manual of Dissection of the Human Body. Fifth Edition. Enlarged, with Marginal References and over 200 Illustrations. Octavo. Cloth, 5.00; Leather, 6.00 Bound in Oilcloth, for the Dissecting Room, $4.50. " No student of Anatomy can take up this book without being pleased and instructed. Its Diagrams are original, striking and suggestive, giving more at a glance than pages of text description. * * * The text matches the illustrations in directness of prac- tical application and clearness of detail." New York Medical Record. Holden's Human Osteology. Comprising a Description of the Bones, with Colored Delineations of the Attachments of the Muscles. The General and Microscopical Structure of Bone and its Development. With Lithographic Plates and Numerous Illus- trations. Seventh Edition. 8vo. Cloth, 6.00 Holden's Landmarks, Medical and Surgical. 4th ed. Cloth, 1.25 Heath's Practical Anatomy. Sixth London Edition. 24 Col- ored Plates, and nearly 300 other Illustrations. Cloth, 5.00 Potter's Compend of Anatomy. Fourth Edition. 117 Illus- trations. Cloth, i.oo; Interleaved for Notes, 1.25 CHEMISTRY. Hartley's Medical Chemistry. A text-book prepared specially for Medical, Pharmaceutical and Dental Students. With 40 Illustrations, Plate of Absorption Spectra and Glossary of Chemi- cal Terms. Cloth, 2.50 *#* This book has been written especially for students and phy- sicians. It is practical and concise, dealing only with those parts of chemistry pertaining to medicine ; no time being wasted in long descriptions of substances and theories of interest only to the advanced chemical student. Bloxam's Chemistry, Inorganic and Organic, with Experiments. Sixth Edition. Enlarged and Rewritten. Nearly 300 Illus- trations. Cloth, 4.50; Leather, 5.50 Richter's Inorganic Chemistry. A text-book for Students. Third American, from Fifth German Edition. Translated by Prof. Edgar F. Smith, PH.D. 89 Wood Engravings and Colored Hate of Spectra. Cloth, 2.00 Richter's Organic Chemistry, or Chemistry of the Carbon Compounds. Translated by Prof. Edgar F. Smith, PH.D. Illustrated. Cloth, 3.00; Leather, 3.50 %S~See pages 2 to 5 for list of Students' Manuals. STUDENTS' TEXT-BOOKS AND MANUALS. 7 Chemistry : Continued. Trimble. Practical and Analytical Chemistry. A Course in Chemical Analysis, by Henry Trimble, Prof, of Analytical Chem- istry in the Phila. College of Pharmacy. Illustrated. Second Edition. 8vo. Cloth, 1.50 Tidy. Modern Chemistry. 2d Ed. Cloth, 5.50 Leffmann's Compend of Chemistry. Inorganic and Organic. Including Urinary Analysis and the Sanitary Examination of Water. New Edition. Cloth, i.oo; Interleaved for Notes, 1.25 Muter. Practical and Analytical Chemistry. Second Edi- tion, Revised and Illustrated. Cloth, 2.00 Holland. The Urine, and Common Poisons, Chemical and Microscopical. For Laboratory Use. 2d Edition, Enlarged. Illustrated. Cloth, .75 Van Nuys. Urine Analysis. Illus. Cloth, 2.00 Wolff's Applied Medical Chemistry. By Lawrence Wolff, M.D., Demonstrator of Chemistry in Jefferson Medical College, Philadelphia. Cloth, i.oo CHILDREN. Goodhart and Starr. The Diseases of Children. A Manual for Students and Physicians. By J. F. Goodhart, M.D., Physi- cian to the Evelina Hospital for Children ; Assistant Physician to Guy's Hospital, London. American Edition, Revised and Edited by Louis Starr, M.D., Clinical Professor of Diseases of Children in the Hospital of the University of Pennsylvania ; Physician to the Children's Hospital, Philadelphia. Containing many new Prescriptions, a List of over 50 Formulae, conforming to the U. S. Pharmacopoeia, and Directions for making Arti- ficial Human Milk, for the Artificial Digestion of Milk, etc. Cloth, 3.00; Leather, 3.50 Day. On Children. A Practical and Systematic Treatise. Second Edition. 8vo. 752 pages. Cloth, 3.00; Leather, 4.00 Meigs and Pepper. The Diseases of Children. Seventh Edition. 8vo. Cloth, 5.00; Leather, 6.00 Starr. Diseases of the Digestive Organs in Infancy and Childhood. With chapters on the Investigation of Disease, and on the General Management of Children. Illus. Cloth, 2.50 Keating and Edwards. Diseases of the Heart and Circulation in Infancy and Adolescence. Illustrated with Wood Engravings, Photographs and one Colored Plate. 8vo. Cloth, 1.50 4^" See page ib for list of ? Quiz- Commends ? 8 STUDENTS' TEXT-BOOKS AND MANUALS. DENTISTRY. Flagg's Plastics and Plastic Filling, sd Ed. Preparing. Gorgas. Dental Medicine. A Manual of Materia Medica and Therapeutics. Second Edition. Cloth, 3.25 Harris. Principles and Practice of Dentistry. Including Anatomy, Physiology, Pathology, Therapeutics, Dental Surgery and Mechanism. Twelfth Edition. Revised and enlarged by Professor Gorgas. 744 Illustrations. Cloth, 6.50 ; Leather, 7.50 Richardson's Mechanical Dentistry. Fifth Edition. 569 Illustrations. 8vo. Cloth, 4.50; Leather, 5.50 Stocken's Dental Materia Medica. Third Edition. Cloth, 2.50 Taft's Operative Dentistry. Dental Students and Practitioners. Fourth Edition. 100 Illustrations. Cloth, 4.25 ; Leather, 5.00 Talbot. Irregularities of the Teeth, and their Treatment. Illustrated. 8vo. Cloth, 2.00 Tomes' Dental Anatomy, Human and Comparative. Third Edition. 191 Illustrations. Preparing. Tomes' Dental Surgery. Third Edition. Revised. 292 Illustrations. 772 Pages. Cloth, 5.00 DICTIONARIES. Cleaveland's Pocket Medical Lexicon. Thirty-first Edition. Giving correct Pronunciation and Definition of Terms used in Medicine and the Collateral Sciences. Very small pocket size, Cloth, red edges .75 ; pocket-book style, i.oo Longley's Pocket Dictionary. The Student's Medical Lexicon, giving Definition and Pronunciation of all Terms used in Medi- cine, with an Appendix giving Poisons and Their Antidotes, Abbreviations used in Prescriptions, Metric Scale of Doses, etc. 24mo. Cloth, i.oo; pocket-book style, 1.25 EYE. Arlt. Diseases of the Eye. Including those of the Conjunc- tiva, Cornea, Sclerotic, Iris and Ciliary Body. By Prof. Von Arlt. Translated by Dr. Lyman Ware. Illus. 8vo. Cloth, 2.50 Hartridge on Refraction. $d Ed. Cloth, 2.00 Macnamara. Diseases of the Eye. 4th Edition. Revised. Colored Plates and Wood Cuts and Test Types. Cloth, 4.00 Meyer. Diseases of the Eye. A complete Manual for Stu- dents and Physicians. 270 Illustrations and two Colored Plates. 8vo. Cloth, 4.50; Leather, 5.50 Morton. Refraction of the Eye. Third Ed. Illus. Cloth, i.oo Fox and Gould. Compend of Diseases of the Eye and Refraction. 2d Ed. Enlarged. 71 Illus. 39 Formulae. Cloth, i.oo; Interleaved for Notes, 1.25 fSee pages 2 to 5 for list of Students' Manuals. STUDENTS' TEXT-BOOKS AND MANUALS. 9 ELECTRICITY. Mason's Compend of Medical and Surgical Electricity. With numerous Illustrations. i2mo. See page 75. Cloth, i.oo HYGIENE. Parkes' Practical Hygiene. Seventh Edition, enlarged. Illus- trated. 8vo. Cloth, 4.50 Wilson's Handbook of Hygiene and Sanitary Science. Sixth Edition. Revised and Illustrated. Cloth, 2.75 MATERIA MEDICA AND THERAPEUTICS. Potter's Compend of Materia Medica, Therapeutics and Prescription Writing. Fifth Edition, revised and improved. Cloth, i.oo; Interleaved for Notes, 1.25 Biddle's Materia Medica. Tenth Edition. For the use of Students and Physicians. By the late Prof. John B. Biddle, M. D. , Professor of Materia Medica in Jefferson Medical College, Phila- delphia. The Eleventh Edition, thoroughly revised, and in many parts rewritten, by his son, Clement Biddle, M.D., Past Assistant Surgeon, U. S. Navy, assisted by Henry Morris, M.D., Demon- strator of Obstetrics in Jefferson Medical College. 8vo., illus- trated. Cloth, 4.00 ; Leather, 4.75 Headland's Action of Medicines, gth Ed. 8vo. Cloth, 3.00 Potter. Materia Medica, Pharmacy and Therapeutics. Including Action of Medicines, Special Therapeutics, Pharma- cology, etc. Page 4. Cloth, 3.00; Leather, 3.50 Roberts' Compend of Materia Medica and Pharmacy. By the author of " Roberts' Practice." Cloth, 2.00 Starr, Walker and Powell. Synopsis of Physiological Action of Medicines, based upon Prof. H. C. Wood's " Materia Medica and Therapeutics." 3d Ed. Enlarged. Cloth, .75 Waring. Therapeutics. With an Index of Diseases and an Index of Remedies. A Practical Manual. Fourth Edition. Revised and Enlarged. Cloth, 3.00; Leather, 3.50 MEDICAL JURISPRUDENCE. Reese. A Text-book of Medical Jurisprudence and Toxi- cology. By John J. Reese, M.D., Professor of Medical Juris- prudence and Toxicology in the Medical Department of the University of Pennsylvania ; President of the Medical Juris- prudence Society of Philadelphia; Physician to St. Joseph's Hospital ; Corresponding Member of The New York Medico- legal Society. 2d Edition. Cloth, 3.00; Leather, 3.50 tiffi* See page ib for list of ? Quiz- Compends ? 10 STUDENTS' TEXT-BOOKS AND MANUALS. Medical Jurisprudence : Continued. Abercrombie's Students' Guide to Medical Jurisprudence. i2mo. Cloth, 2.50 Mann's Manual of Psychological Medicine, and Allied Ner- vous Diseases. Their Diagnosis, Pathology and Treatment, and their Medico-Legal Aspects. Illus. Cloth, 5.00; Leather, 6.00 Woodman and Tidy's Medical Jurisprudence and Toxi- cology. Chromo-Lithographic Plates and 116 Wood engravings. Cloth, 7.50; Leather, 8.50 MISCELLANEOUS. Allingham. Diseases of the Rectum. Fourth Edition. Illus- trated. 8vo. Paper covers, .75; Cloth, 1.25 Beale. Slight Ailments. Their Nature and Treatment. Illus- trated. 8vo. Paper cover, .75 ; Cloth, 1.25 Domville on Nursing. 6th Edition. Cloth, .75 Fothergill. Diseases of the Heart, and Their Treatment. Second Edition. 8vo. Cloth, 3.50 Gowers. Diseases of the Nervous System. 341 Illus- trations. Cloth, 6.50; Leather, 7.50 Tanner. Memoranda of Poisons. Their Antidotes and Tests. Sixth Edition. Revised by Henry Leffmann, M.D. Cloth, .75 OBSTETRICS AND GYNAECOLOGY. Byford. Diseases of Women. The Practice of Medicine and Surgery, as applied to the Diseases and Accidents Incident to Women. By W. H. Byford, A.M., M.D., Professor of Gynaecology in Rush Medical College and of Obstetrics in the Woman's Med- ical College, etc., and Henry T. Byford, M.D. , Surgeon to the Woman's Hospital of Chicago ; Gynaecologist to St. Luke's Hospital, etc. Fourth Edition. Revised, Rewritten and En- larged. With 306 Illustrations, over 100 of which are original. Octavo. 832 pages. Cloth, 5.00 ; Leather, 6.00 Lewer's Diseases of Women. A Practical Text-Book. 139 Illustrations. Cloth, 2.25 Parvin's Winckel's Diseases of Women. Edited by Prof. Theophilus Parvin, Jefferson Medical College, Philadelphia. 117 Illustrations. See page 3. Cloth, 3.00; Leather, 3.50 Morris. Compend of Gynaecology. Illustrated. In Press, ee Pages 2 to j 'for list of New Manuals. STUDENTS' TEXT-BOOKS AND MANUALS. 11 Obstetrics and Gynaecology : Continued. Landis' Compend of Obstetrics. Illustrated. 3d edition. Cloth, i.oo; Interleaved for Notes, 1.25 Galabin's Midwifery. A New Manual for Students. By A. Lewis Galabin, M.D., F.R.C.P., Obstetric Physician to Guy's Hospital, London, and Professor of Obstetrics in the same Insti- tution. 227 Illustrations Cloth, 3.00; Leather, 3.50 Glisan's Modern Midwifery. 2d Edition. Cloth, 3.00 Rigby's Obstetric Memoranda. By Alfred Meadows, M.D. 4th Edition. Cloth, .50 Meadows' Manual of Midwifery. Including the Signs and Symptoms of Pregnancy, Obstetric Operations, Diseases of the Puerperal State, etc. 145 Illustrations. 494 pages. Cloth, 2.00 Swayne's Obstetric Aphorisms. For the use of Students commencing Midwifery Practice. 8th Ed. i2mo. Cloth, 1.25 PATHOLOGY. HISTOLOGY. BIOLOGY. Bowlby. Surgical Pathology and Morbid Anatomy, for Students. 135 Illustrations. i2mo. Cloth, 2.00 Davis' Elementary Biology. Illustrated. Cloth, 4.00 Rindfleisch's General Pathology. By Tyson. For Students and Physicians. By Prof. Edward Rindfleisch, of Wiirzburg. Translated by Wm. H. Mercur, M.D., of Pittsburgh, Pa. Edited by James Tyson, M.D., Professor of Pathology and Morbid Anatomy in the University of Pennsylvania. i2mo. Cloth, 2.00 Gilliam's Essentials of Pathology. A Handbook for Students. 47 Illustrations. i2mo. Cloth, 2.00 *#* The object of this book is to unfold to the beginner the funda- mentals of pathology in a plain, practical way, and by bringing them within easy comprehension to increase his interest in the study of the subject. Gibbes' Practical Histology and Pathology. Third Edition. Enlarged. i2mo. Cloth, 1.75 PHYSICAL DIAGNOSIS. Bruen's Physical Diagnosis of the Heart and Lungs. By Dr. Edward T. Bruen, Assistant Professor of Clinical Medicine in the University of Pennsylvania. Second Edition, revised. With new Illustrations. i2mo. Cloth, 1.50 PHYSIOLOGY. Yeo's Physiology. Third Edition. The most Popular Stu- dents' Book. By Gerald F. Yeo, M.D., F.R.C.S., Professor of Physiology in King's College, London. Small Octavo. 758 pages. 321 carefully printed Illustrations. With a Full Glossary and Index. See Page 3. Cloth, 3.00; Leather, 3.50 See page ib for list of ?Quiz-Compends ? 12 STUDENTS' TEXT-BOOKS AND MANUALS. Physiology : Continued. Brubaker's Compend of Physiology. Illustrated. Fourth Edition. Cloth, i.oo; Interleaved for Notes, 1.25 Stirling. Practical Physiology, including Chemical and Ex- perimental Physiology. 142 Illustrations. Cloth, 2 25 Kirke's Physiology. i2th Ed. Revised and Enlarged. Illus. Cloth, 4.00; Leather, 5.00 Landois' Human Physiology. Including Histology and Micro- scopical Anatomy, and with special reference to Practical Medi- cine. Second Edition. Translated and Edited by Prof. Stirling. 583 Illustrations. Cloth, 6.50; Leather, 7.50 " So great are the advantages offered by Prof. Landois' Text- book, from the exhaustive and eminently practical manner in which the subject is treated, that, notwithstanding it is one of the largest works on Physiology, it has yet passed through four large editions in the same number of years. Dr. Stirling's annotations have materially added to the value of the work. . . . Admirably adapted for the practitioner. . . . With this Text-book at his command, no student could fail in his examination." Lancet. Sanderson's Physiological Laboratory. Being Practical Ex- ercises for the Student. 350 Illustrations. 8vo. Cloth, 5.00 Tyson's Cell Doctrine. Its History and Present State. Illus- trated. Second Edition. Cloth, 2.00 PRACTICE. Roberts' Practice. New Revised Edition. A Handbook of the Theory and Practice of Medicine. By Frederick T. Roberts, M.D. ; M.R.C.P., Professor of Clinical Medicine and Therapeutics in University College Hospital, London. Seventh Edition. Octavo. Cloth, 5.50 ; Sheep, 6.50 Hughes. Compend of the Practice of Medicine. 3d Ed. Two parts, each, Cloth, i.oo; Interleaved for Notes, 1.25 PART i. Continued, Eruptive and Periodical Fevers, Diseases of the Stomach, Intestines, Peritoneum, Biliary Passages, Liver, Kidneys, etc., and General Diseases, etc. PART n. Diseases of the Respiratory System, Circulatory System and Nervous System ; Diseases of the Blood, etc. Tanner's Index of Diseases, and Their Treatment. Cloth, 3.00 " This work has won for itself a reputation. ... It is, in truth, what its Title indicates." N. Y. Medical Record. PRESCRIPTION BOOKS. Wythe's Dose and Symptom Book. Containing the Doses and Uses of all the principal Articles of the Materia Medica, etc. Seventeenth Edition. Completely Revised and Rewritten. Just Ready. 32mo. Cloth, i.oo; Pocket-book style, 1.25 Pereira's Physician's Prescription Book. Containing Lists of Terms, Phrases, Contractions and Abbreviations used in Prescriptions, Explanatory Notes, Grammatical Construction of Prescriptions, etc., etc. By Professor Jonathan Pereira, M.D. Sixteenth Edition. 321110. Cloth, i.oo ; Pocket-book style, 1.25 pages 2 to 3 for list of New Manuals. STUDENTS' TEXT-BOOKS AND MANUALS. 13 PHARMACY. Stewart's Compend of Pharmacy. Based upon Remington's Text-Book of Pharmacy. Second Edition, Revised. Cloth, i. oo ; Interleaved for Notes, 1.25 SKIN DISEASES. Anderson, (McCall) Skin Diseases. A complete Text-Book, with Colored Plates and numerous Wood Engravings. 8vo. Just Ready. Cloth, 4.50; Leather, 5.50 " We welcome Dr. Anderson's work not only as a friend, but as a benefactor to the profession, because the author has stricken off mediaeval shackles of insuperable nomenclature and made crooked ways straight in the diagnosis and treatment of this hitherto but little understood class of diseases. The chapter on Eczema is alone worth the price of the book." Nashville Medical News. " Worthy its distinguished author in every respect; a work whose practical value commends it not only to the practitioner and stu- dent of medicine, but also to the dermatologist." Jcwes Nevens Hyde, M.D., Prof, of Skin and Venereal Diseases, Rush Medical College, Chicago. Van Harlingen on Skin Diseases. A Handbook of the Dis- eases of the Skin, their Diagnosis and Treatment. By Arthur Van Harlingen, M.D., Prof, of Diseases of the Skin in the Phila- delphia Polyclinic ; Consulting Physician to the Dispensary for Skin Diseases, etc. With colored plates. i2mo. Cloth, 1.75 Bulkley. The Skin in Health and Disease. By L. Duncan Bulkley, Physician to the N. Y. Hospital. Illus. Cloth, .50 SURGERY. Heath's Minor Surgery, and Bandaging. Eighth Edition. 142 Illustrations. 60 Formulae and Diet Lists. Cloth, 2.00 Horwitz's Compend of Surgery, including Minor Surgery, Amputations, Fractures, Dislocations, Surgical Diseases, and the Latest Antiseptic Rules, etc., with Differential Diagnosis and A Very much Enlarged and Rearranged. 91 Illustrations and 77 Formulae. i2mo. No. q ? Quiz- Compend ? Series. Cloth, i. oo ; Interleaved for the addition of Notes, 1.25. Pye's Surgical Handicraft. A Manual of Surgical Manipula- tions, Minor Surgery, Bandaging, Dressing, etc., etc. With special chapters on Aural Surgery, Extraction of Teeth, Anaes- thetics, etc. 208 Illustrations. 8vo. Cloth, 5.00 Swain's Surgical Emergencies. New Edition. Illus. Clo.,i.5o Walsham. Manual of Practical Surgery. For Students and Physicians. By WM. J. WALSHAM, M.D., F.R c.s., Asst. Surg. to, and Dem. of Practical Surg. in, St. Bartholomew's Hospital, Surgeon to Metropolitan Free Hospital, London. With 236 Engravings. See Page 2. Cloth, 3.00; Leather, 3.50 Watson on Amputation of the Extremities, and their Compli cations. 2 colored plates and 250 wood cuts. 8vo. Cloth, 5.50 e page ibfor list of ? Quiz- Comp ends* 14 STUDENTS' TEXT-BOOKS AND MANUALS. THROAT. Mackenzie on the Throat and Nose. New Edition. By Morell Mackenzie, M.D., Senior Physician to the Hospital for Diseases of the Chest and Throat; Lecturer on Diseases of the Throat at the London Hospital, etc. Revised and Edited by D. Bryson Delavan, M.D., Prof, of Laryngology and Rhinology in the N. Y. Polyclinic; Chief of Clinic, Department of Diseases of the Throat, College of Physicians and Surgeons, N. Y. ; Sec'y of the Amer. Laryngological Assoc., etc. Complete in one vol- ume, over 200 Illustrations, and many formulae. Preparing. Diseases of the QEsophagus, Nose and Naso-Pharynx, with Formulas and 93 Illustrations. Cloth, 3.00; Leather, 4.00 " It is both practical and learned ; abundantly and well illustrated ; its descriptions of disease are graphic and the diagnosis the best we have anywhere seen." Philadelphia Medical Times. Cohen. The Throat and Voice. Illustrated. Cloth, .50 James. Sore Throat. Its Nature, Varieties and Treatment. i2mo. Illustrated. Paper cover, .75; Cloth, 1.25 URINE, URINARY ORGANS, ETC. Acton. The Reproductive Organs. In Childhood, Youth, Adult Life and Old Age. Sixth Edition. Cloth, 2.00 Beale. Urinary and Renal Diseases and Calculous Disorders. Hints on Diagnosis and Treatment. i2mo. Cloth, 1.75 Holland. The Urine, and Common Poisons. Chemical and Microscopical, for Laboratory Use. Illustrated. 2d Edition. Cloth, .75 Ralfe. Kidney Diseases and Urinary Derangements. 42 Illus- trations. i2mo. 572 pages. Cloth, 2.75 Legg. On the Urine. A Practical Guide. 6th Ed. Cloth, .75 Marshall and Smith. On the Urine. The Chemical Analysis ot the Urine. By John Marshall, M.D., Chemical Laboratory, Univ. of Penna; and Prof. E. F. Smith, PH.D. Col. Plates. Cloth, i.oo Thompson. Diseases of the Urinary Organs. Seventh Edition. Illustrated. Cloth, 1.25 Tyson. On the Urine. A Practical Guide to the Examination of Urine. With Colored Plates and Wood Engravings. 6th Ed. Enlarged. i2mo. Cloth, 1.50 Van Niiys, Urine Analysis. Illus. Cloth, 2.00 VENEREAL DISEASES. Hill and Cooper. Student's Manual of Venereal Diseases, with Formulae. Fourth Edition. i2mo. Cloth, i.oo Durkee. On Gonorrhoea and Syphilis. Illus. Cloth, 3.50 See page ib for list of ? Quiz-Compends t MEDICAL BRIEFS. A new series of short, concise compends for the Med- ical Student and Practitioner. i2mo. Cloth. Price of Each Book, $1.00. No. i. POST-MORTEM EXAMINATIONS. -With Especial Reference to Medico- Legal Practice. By Prof. RUDOLPH VIRCHOW, of Berlin Charite Hos- pital, author of Cellular Pathology ; Translated by T. P. SMITH, M.D., Member of the Royal College of Sur- geons of England. 2d American, from the 4th German Edition. With new Plates. Illustrated by Four Litho- graphs. " We are informed in precise and exact terms how a post-mortem examination should be made, both with regard to the plan to be pursued, and the manner of making the several cuts into the various organs and tissues. The method of recording the results of the investigation is clearly indicated by the addition of the detailed account of the examination of four cases ; and the value of the ob- jective evidence is accurately stated in the form of the inferences drawn concerning the manner and cause of death." American Journal of Medical Sciences. No. 2. MANUAL OF VENEREAL DISEASES. A Concise Description of those Affections and of their Treatment, including a list of SIXTY-SEVEN PRESCRIP- TIONS for Vapor Bath, Gargles, Injections, Lotions, Mixtures, Ointments, Paste, Pills, Powders, Solutions and Suppositories. By BERKELEY HILL, M.D., Pro fessor of Clinical Surgery in University College ; Sur- geon to University College and Lock Hospitals; and ARTHUR COOPER, M.D., formerly House Surgeon, Lock Hospital, London. 4th Edition, Revised and Enlarged. " I have examined it with care, and find it to be a practical and useful compendium of knowledge on the subjects discussed, well adapted to the use of medical students and those physicians in general practice who have occasional need to consult a work of this kind." -James Nei'ens Hyde, M.D., Professor of Skin and Venereal Diseases^ Rush Medical College, Chicago. No. 3. MEDICAL ELECTRICITY. A Com- pend of Electricity and its Medical and Surgical Uses. By CHAS. F. MASON, M.D., Ass't Surg. U. S. Army; with an introduction by CHARLES H. MAY, M.D., Instructor in Ophthalmology, New York Polyclinic. Illustrated. OTHER VOLUMES IN PREPARATION. Price of Each Book, bound in Cloth, $1.00. PQUIZ-COMPENDS? A new series of books for Students' use in the Quiz Class and when preparing for Examinations. Price of each Book, Cloth, $1.00 ; Interleaved, 1.25. I. ANATOMY. By Prof. S. O. L. POTTER, Late A. A. Surg. U. S. A. Fourth Edition. 117 Illustrations. II. PRACTICE. Part i. By DAN'L E. HUGHES, M.D., late Demonstrator of Clinical Medicine in Jefferson College. Third Edition, Enlarged. III. PRACTICE. Part 11. Same author as above. Third Edition, Enlarged. IV. PHYSIOLOGY. By A. P. BRUBAKER, Demon- strator of Physiology in Jeff. Med. College, Philadel- phia. Fourth Edition, Improved. New Illustrations. V. OBSTETRICS. By Prof. HENRY G. Landis. Third Edition. Illustrated. VI. MATERIA MEDICA, THERAPEUTICS AND PRESCRIPTION WRITING. By Prof. SAM'L O. L. POTTER. 5th Ed., Enlarged and Imp. VII. GYNAECOLOGY. By HENRY MORRIS, M.D., Demonstrator of Obstetrics and Diseases of Women and Children, Jeff. Medical College. Illus. In Press. VIII. DISEASES OF THE EYE AND RE- FRACTION. By L. 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PBICE OF EACH BOOE, CLOTH, $1.00; INTEBLEAVED, $1.25. Medical Students' Handbooks. HARTLEY'S MEDICAL CHEMISTRY. A Text-book for Medical and Pharmaceutical Students. By E. H. HARTLEY, M.D., Professor of Chemistry and Toxicology at the Long Island College Hospital; President of the American Society of Public Analysts ; Chief Chemist, Board of Health, of Brooklyn, N. Y. With Illustrations, Glossary, and Complete Index. I2mo. Cloth, $2.50. " Probably the best chemistry for medical students." -Journal of the American Medi- cal Association. " I especially like the first part, dealing with chemical physics and elementary chemistry." Prof.J. W. Holland, Jefferson Medical College, Phila. VAN HARLINGEN ON SKIN DISEASES. Their Diagnosis and Treatment. 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THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW Pr: be< c. ks. iman Physi- ~th special By DrrL. ogical Insti- nan Edition, Professor of ersity, Man- rsity of Ox- "1 lustrations. MINATION." ' bridge ' be- ipleteness and itish Medical Physiology to that has ever i Revised The Theory aiancy and Member of anged, with jstetrics and ic of Paris, .n Editions. he Northern [JNDE, M.D., ce-President aphs, Litho- blly colored, [ther, $6.00. bf Ophthal- le la Facult6 ! Translated lithor, by Dr. y. With 267 tection of Dr. ling the eyes, ophthalmo- \ Each dis- k being pre- etiology and B systematic, and concise the seventh language into which Meyer's book has been translated. P. BLAKISTON, SON & CO., Publishers and Booksellers, 1012 WALNUT STREET, PHILADELPHIA. e: sc e! * c< 1m 4/29 Standard Text-Books. HOLDEN'S ANATOMY. A Manual of the Dissections of the Human Body. By LUTHER HOLDEN, F.R.C.S. Fifth Edition. Carefully Revised and. Enlarged, specially concerning the Anatomy of the Nervous System Organs of Special Sense, etc. By JOHN LANGTON, F.R.C.S., Surgeon to, and Lecturer on Anatomy at, St. Bartholomew's Hospital. 208 Illustrations. 8vo. Cloth, #5^ ^ J *^ QQ r-~-___ ' _Q J*>t 1 V\ ~. 1 ' O. ' IP^T'J The popularity of tW QdQ bly used more extensi; ing, and does not ret; carefully printed an<' " No student of a diagrams are origin; description. All th work ; but it is sinv these points be empj illustrations in direi teal Record. ANDERSON Diseases. University ored and st This aims to of treatment, an extensive ex] GOWERS SYST Professoj Nation 400 111 BYFORD Surge: By" Colle the etc., of c: "if I -words, i " The best tear any other, whi' P. BL * so few age, or of ,^_ ellers,