uals, )ING. l°" By WM. J. Surgery in, ontains all the d the cumber- in one word — >e, and having nd their subse- k successfully. : once say that .ount of careful •British Medi- By Dr. F. of Munich. Professor of ical College, This\ complet< tical rul< " The . into the h able price. J 3 clearness and ' the best prac- ». r J , "} one to put nds of students. It is issued in a neat and attractive form, and at a very reason- " — Boston Medical and Surgical Journal. No. 3. MIDWIFERY. By ALFRED LEWIS GALABIN, M.A., M.D., Obstetric Physician to, and Lecturer on Midwifery and the Diseases of Women at, Guy's Hospital, London, etc. 227 fine Engravings. "The illustrations are mostly new and well executed, and we heartily commend this book as far superior to any manual upon this subject." — Archives of Gyncecology, New York. " Sensible, practical and complete." — Medical Brief. " I have carefully read it over, and, as a teacher of midwifery, I consider the book ought to become one of the recognized text-books ; the treatment and pathology of the various subjects treated are clear and concise."— -J. Algernon Temple, M.D., Prof, of Midwifery, and Gynacology, Trinity Medical School, Toronto. No. 4. PHYSIOLOGY. Fourth Edition. By GERALD F. YEO, M.D., F.R.C.S., Professor of Physiology in King's College, London. Fourth American from Second English Edition. 321 carefully printed Illustrations. " The work will take a high rank among the smaller text-books of Physiology."— Prof. H. P. Bowditch, Harvard Medical School. " By his excellent manual, Prof. Yeo has supplied a want which must have been felt by every teacher of Physiology." — The Dublin Journal of Medical Science. Jt&- SEE NEXT PAGE. P. BLAKISTON, SON & CO., Publishers and Booksellers, 1012 WALNUT STREET, PHILADELPHIA. Th -d. No. 5. ORl X^-^r^^^Xv RlCHTER, University y^VX^^^N^V Edition by f/(i J J^^^^^t^CP^^%^ ^>k rcf ("Villpcrf* EDGAR F Springfiel >f Pennsyl- vania, etc I Q IXjPfeifc^i&AJ ~)l " I must say \V.Ayo'}y compendious shape."-/. » Y^vvOTfl^iSH^v^y 'cal College, Philadelphia. " This work 1 ^^^^^^^ at in a clear, comprehensive than that of old ^- ^ idily grasped ic when, to a great extent, tt wants of both t tation to the No. 6. CHI HART, M. THE LIBRARY F. GoOD- Ass istant Physician Edited bi OF evised and )f Children in the t Children's Directions THE UNIVERSITY ian to the rmulse, and 1 Digestion of Milk, < " Nothing th OF CALIFORNIA the author's attention. Fro ion, and one reads it with th the bedside. It need scarcel editor are of much value, ne 'ie American Medical Assoc, PRESENTED BY No. 7. PR on. With an Index PROF. CHARLES A. KOFOID AND Rewritten and Revi of Mfedic MRS. PRUDENCE W. KOFOID e Professor " Our admira of the great practical value t. We wish a copy could be itry. Incur estimation, it is tal. "It is, indee ur attention. Combining the i which no young _ " This work! — . ... — _ . .... . _. ms a volume */. No. 8. MEDICAL JURISPRUDENCE AND TOXICOLOGY. Second Edition. By JOHN J. REESE, M.D., Professor of Medical Juris- prudence and Toxicology, University of Pennsylvania, etc. Second Edition. Enlarged. " The production of this admirable text-book by one of the two or three leading teachers of medical jurisprudence in America, will, we hope, give a hew impetus to the study of forensic medicine, which, inviting and important as it is, has heretofore been strangely neglected in both legal and medical schools." — A: nerican Journal of the Medical Sciences. "We heartily second the author's hope that this treatise may encourage an increasing interest in the students for that most important, but too much neglected, subject, forensic medicine." — Boston Medical and Surgical Journal. " We lay this volume aside, after a careful perusal of its pages, with a profound impres- sion 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. *** Other Volumes in Preparation. A complete illustrated circular, with sample pages, sent free, upon application. Price of Each Book, Cloth, $3.00; Leather, $3.50. P. 8LAKISTON, SON & CO., Publishers and Booksellers, 1012 WALNUT STREET, PHILADELPHIA. FROM PROF. J. M. DACOSTA.— " I find it an excellent -work, doing credit to the learning and discrimination of the author." A NEW MEDICAL DICTIONARY. Compact and concise, including all the Words and Phrases used in medicine, with Pronunciation and Definitions. BASED ON RECENT MEDICAL LITERATURE. GEORGE M. GOULD, A.B.,M.D., Ophthalmic Surgeon to the Philadelphia Hospital, Clinical Chief Ophthalmo- logical Dept., German Hospital^ Phila- delphia. SEVERAL THOUSAND NEW WORDS Small, Square 8vo, Half Morocco, as above, NOT CONTAINED IN ANY with Thumb Index, . . . $4.25 Plain Dark Leather, without Thumb Index, 3.25 Among others IT CONTAINS TABLES of the ARTERIES, of the BACILLI, giving the Name, Habitat, etc. ; of GANGLIA, LEUCOMAINES, MICROCOCCI, MUSCLES, NERVES, PLEXUSES, PTOMAINES, with the Name, Formula, Physiological Action, etc.; COMPARISON OF THERMOMETERS; WEIGHTS AND MEASURES, of VITAL STATISTICS, etc. OPINIONS OF PROMINENT MEDICAL TEACHERS. " The compact size of this dictionary, its clear type, and its accuracy are unfailing pointers to its coming popularity."— John B. Hamilton, Supervising Surgeon-General U. S. Marine Hospital Service, Washington. " It is certainly as convenient and as useful a volume as can be found, regarding contents as well as arrangement."— Julius Pohlman, Prof, of Physiology , University of Buffalo. " I have examined it with considerable care, and am very much pleased with it. It is a handy book for reference, and so far as I have examined it, it is accurate in every particular." — E. H. Bartley, Prof, of Chemistry, Long Island College Hospital, Brooklyn. " I consider this the dictionary of all others for the medical student, and shall see that it is placed on our list of text-books. — A. R. Thomas, M.D., Dean Hahnemann Medical College, Philadelphia. " It will be recommended among our text-books in our new catalogue." — S. E. Chaille, M.D., Dean Medical Dept., Tulane University, New Orleans. " Compact, exact, up to date, and the tables are most excellent and instructive. I prefer it to the larger and older books."— Prof. C. B. Parker, Medical Dept., Western Reserve University, Cleveland. " I have given your ' New Medical Dictionary ' a critical examination. Its size has made it convenient to the study table and handy fo/ frequent use. At the same time it is compre- hensive as to the number of words, including those of the latest coinage, and concise in its definitions. The etymology and accentuation materially enhance its value, and help to make it worthy a place with the classical books of reference for medical students."—./. W. Holland, M.D., Dean Jefferson Medical College, Philadelphia. JtST Students will find this an extremely useful book of reference. The ana- tomical tables will be of great use in memorizing the arteries, muscles, etc. ? QUIZ-CO M PEN DS. ? No. 4. 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 ; FELLOW OF THE COLLEGE OF PHYSICIANS OF PHILADELPHIA. SIXTH EDITION, REVISED AND IMPROVED. WITH NEW ILLUSTRATIONS AND A TABLE OF PHYSIOLOGICAL CONSTANTS. PHILADELPHIA: P. BLAKISTON, SON £ CO., 1012 WALNUT STREET. 1891. Entered according to Act of Congress, in the year 1891, by P. BLAKISTON, SON & CO., In the office of the Librarian of Congress, at Washington, D. C. PHESS OF WM. F. FELL & Co., I22O-24 SANSOM Sr., PHILADELPHIA. PREFACE TO SIXTH EDITION. It has been deemed advisable in the preparation of a Sixth Edition of the Compend to insert a number of additional paragraphs upon subjects which appeared to be of interest and importance to medical students. This has accordingly been done, with the result of increasing the size of the book some fifteen pages. It is hoped that the present edition will even more fully meet the needs of the student. ALBERT P. BRUBAKER. Entered according to Act of Congress, in the year 1891, by P. BLAKISTON, SON & CO., In the office of the Librarian of Congress, at Washington, D. C. PKESS OF WM. F. FELL & Co., 1220-24 SANSOM ST., PHILADELPHIA. PREFACE TO SIXTH EDITION. It has been deemed advisable in the preparation of a Sixth Edition of the Compend to insert a number of additional paragraphs upon subjects which appeared to be of interest and importance to medical students. This has accordingly been done, with the result of increasing the size of the book some fifteen pages. It is hoped that the present edition will even more fully meet the needs of the student. ALBERT P. BRUBAKER. PREFACE TO FIFTH EDITION. In the preparation of a Fifth Edition of the Compend of Physiology, the author has taken the opportunity to revise and rewrite a number of sections, to insert a few figures and to add some seventeen pages of new matter which, it is hoped, will further increase its usefulness to the student. While many of the changes that have been made will be found distributed throughout the body of the work, the principal additions will be found in the sections pertaining to the nervous system. Notwithstanding the many additions which have been made in this and previous editions, care has been taken to keep the Compend what it was originally intended to be, viz: A compact and convenient arrangement of the fundamental facts of human physiology. As most medical students enter upon the study of physiology before they have acquired 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 is believed that it will be practically useful to students during their attendance upon lectures and in reviewing the subject prior to examinations. 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. TABLE OF CONTENTS. PAGE INTRODUCTION, 9 CHEMICAL COMPOSITION OF THE BODY, 10 STRUCTURAL COMPOSITION OF THE BODY, 17 FOOD, 19 DIGESTION, 24 ABSORPTION, 37 BLOOD, 45 CIRCULATION OF BLOOD, 51 RESPIRATION, 59 ANIMAL HEAT, 67 SECRETION, t 69 Mammary Glands, 72 Vascular or Ductless Glands, 74 EXCRETION, 76 Kidneys, 76 Liver, . 83 Skin, 88 NERVOUS SYSTEM, 92 Properties and Functions of Nerves, 95 Cranial Nerves, 102 Spinal Cord, 116 Spinal Nerves, 118 Medulla Oblongata, '127 Pons Varolii, 131 Crura Cerebri, 131 Corpora Quadrigemina, 132 Corpora Striata and Optic Thalami, 133 vii Vlii TABLE OF CONTENTS. PAGE Cerebellum, 134 Cerebrum, 136 Sympathetic Nervous System, 147 SENSE OF TOUCH, 151 SENSE OF TASTE, 152 SENSE OF SMELL, 154 SENSE OF SIGHT, 154 SENSE OF HEARING, 165 VOICE AND SPEECH, 173 REPRODUCTION, 176 Generative Organs of the Female, 176 Generative Organs of the Male, 179 Development of Accessory Structures, 180 Development of the Embryo, 185 TABLE OF PHYSIOLOGICAL CONSTANTS, 191 TABLE SHOWING RELATION OF WEIGHTS AND MEASURES OF THE METRIC SYSTEM TO APPROXIMATE WEIGHTS AND MEASURES OF THE U. S., 194 INDEX, 195 COMPEND OF HUMAN PHYSIOLOGY. Physiology, from (pvaig, nature, and Adyof, a discourse, in its original application embraced the study of all natural objects, inorganic as well as organic. In its modern application physiology signifies the 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. A 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. 2. 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. By chemical analysis the solids and fluids of the body can be first reduced to a number of compound substances which are termed proximate principles : these again can be resolved by an ultimate analysis into fifteen chemical elements. The different chemical elements thus obtained, and the proportions in which they exist, are shown in the following table : — 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 { O. H. C. and N. found in most of the fluids Carbon ... 13-50 j and all tissues except fat. Sulphur . . . .147 ... In fibrin, casein, albumin, gelatin; as potas- sium sulpho-cyanide in saliva; as alkaline sulphate in urine and sweat. Phosphorus . 1.15 ... In fibrin and albumin; 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 . .001 . . . 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 gj per cent, of the body, O. H. N. are eminently mobile, elastic, and possess great atomic heat. C. H. N. are distinguised 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 remarkable display of chemical activity. Chemical elements, with the exception of the gases, O. H. and N., do not exist alone in the body, but are combined in characteristic propor- tions to form compounds, the proxi mate princ {files, the ultimate compounds to which the fluids and solids can be reduced. CHEMICAL COMPOSITION OF THE HUMAN BODY. 11 Proximate Principles exist in the body under their own form, and can be extracted without losing their distinctive properties. There are about one h-undred proximate principles, which are divided into four classes, viz : inorganic, organic non-nitrogenized, organic nitro- genized, and principles of waste. 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. 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, "] SllhVph^' [ • • I-l, fluids and solids of the body. Potassium phosphate, J Sodium sulphate, | TT . , M1 ,., , .... Potassium sulphate, } ' ' Umversal exCePl milk» blle and SastnC JU1Ce' Sodium carbonate, ") , , , , , Potassium carbonate, } ' • Bones, blood, lymph, urine, etc. Magnesium carbonate, . . . Blood and sebaceous matter. Oxygen is one of the constituent elements of all the fluids and solids of the body. It is found in a free state in the respiratory passages and intesti- nal tract ; it is held in solution in the lymph and plasma and forms a loose combination with the haemoglobin of the blood corpuscles. The function of the oxygen in the body appears to be the oxidation of albuminous, ole- aginous and saccharine compounds to their ultimate forms, urea, carbonic acid, water, etc. As to whether this is brought about by direct oxidation or by a fermentative process is yet unknown. .As oxygen only enters into combination under a high temperature, it is assumed that it exists in the body under the form of ozone, O3, which possesses remarkably active oxid- izing powers. The seat of oxidation is at present located in the tissues, as the presence of ozone in the blood has not been positively demonstrated. Hydrogen is also a constituent element of almost all the compounds of the body; it exists in a free state in the intestinal tract, where it is produced 12 HUMAN PHYSIOLOGY. by a decomposition of organic substances ; it is also produced within the tis- sues as a result of chemical changes. Its function is unknown, though it is asserted by Hoppe-Seyler that hydrogen unites with neutral oxygen, O2, in the tissues, forming water and liberating oxygen in the nascent state, which becomes the oxidizing agent. The process is represented in the following equation : — HH -f- O2 -f n = H2O + On, in which n represents the oxidizable substance. Water is an essential constituent of all the tissues of the body, consti- tuting 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 essential 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 Monde 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 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 exfst in the proportion to form water, the amount of carbon being variable; 2d, the fats, bodies having the same CHEMICAL COMPOSITION OF THE HUMAN BODY. 13 elements entering into their composition, but with the carbon and hydrogen increased and the oxygen diminished in amount; 3d, fatty acids; 4th, alco-- hols. 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 experi- mental proof that sugar contributes directly to the formation of fat in the animal body. NEUTRAL FATS. C. O. H. Palmitin. Stearin. Olein. 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 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. FATTY ACIDS. C. O. H. Palmitic acid. Propionic acid. Stearic acid. Butyric acid. Oleic acid. . Caproic acid. 14 HUMAN PHYSIOLOGY. The Fatty acids combined with sodium, potassium and calcium, are •found as salts in various fluids of the body, such as blood, 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. ALCOHOLS. Glycerine. Cholesterine. Alcohol. Glycerine is chemically a triatomic alcohol in combination with the neu- tral fats of the body. During pancreatic digestion it is set free. It is supposed by many physiologists to be directly concerned in the production of glycogen. Cholesterine is a crystallizable substance largely present in the bile, though it is found in other fluids and solids. It is supposed to be a waste product of nervous matter. Alcohol has been found in the urine. It is supposed to be the result of an alcoholic fermentation in the intestine. III. ORGANIC NITROGENIZED PRINCIPLES. The nitrogenized or proteid 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 proteids 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 cause starch and albumin to be transformed into sugar and albuminose respectively. Different proteids possess varying proportions of water, which they lose CHEMICAL COMPOSITION OF THE HUMAN BODY. 15 when subjected to desiccation, becoming solid; but upon exposure to moisture they again absorb water, regaining their original condition — 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 nitrogenized compounds undergo putrefactive changes, give rise to carburetted and sulphuretted hydrogen and other gases. In order that these changes may take place it is essential that certain condi- tions be present: viz., atmospheric air or some fluid containing oxygen, moisture, and a temperature varying between 60° and 90° F. The cause of the putrefactive change is the presence of a minute unicellular organ- ism, the bacterium termo. The nitrogenized bodies found in the organism are quite numerous, and although they resemble each other in many particulars, there are yet important differences, and can be arranged into the following groups : — 1. NATIVE ALBUMINS. — Proteid bodies soluble in water, many acids, and usually in alkalies; coagulable at a temperature of from 140° to 163° F. a. Serum Albumin, the principal form of albumin found in the animal fluids and solids. b. Egg albumin, not found in ordinary tissues, but present in white of egg. 2. GLOBULINS. — Proteid bodies insoluble in water, but soluble in solutions of sodium chloride. a. Globulin, found in many tissues, but largely present in crystalline lens. b. Myosin, found in the muscles in life in a fluid condition; after death it undergoes coagulation, giving rise to the rigidity of the muscles. c. Paraglobulin, present in blood and obtained from it by passing a stream of carbon dioxide through it; it is also precipitated by adding sodium chloride. d. Fibrinogen, present in serous fluid and blood, and can be precipi- tated by the prolonged use of carbon dioxide ; it is also precipitated by the addition of 12 to 1 6 per cent, of sodium chloride. 3. DERIVED ALBUMINS. — Proteid bodies which are not coagulable by heat; insoluble in pure water and in salt solutions ; soluble in both acid and alkaline solutions. a. Acid Albumin, found principally in the stomach during first stage of digestion, the result of the action of the hydrochloric acid upon the albumin of the food. 16 HUMAN PHYSIOLOGY. b. Alkali Albumin, found in the intestine during pancreatic digestion, the result of the action, of alkalies upon the albumin of the food. c. Casein, the chief proteid of milk ; it is precipitated by acetic acid and rennet. 4. PEPTONES. — These bodies are formed in the stomach and intestinal tract by the action of the gastric and pancreatic juices upon the albumins of the food. They are very soluble in water, alkaline and acid solutions ; non-coagulable by heat; very diffusible. They are precipitated by tannic acid and alcohol. 5. ALBUMINOIDS. — The albuminoids are the results of various modifica- tions of albumins occurring during the nutritive process, as well as by the action of various external influences. a. Mucin, the characteristic ingredient of mucus secreted by the mucous membranes, giving to it its viscidity. b. Chondrin, found in cartilage. c. Gelatin, found in connective tissue, tendons, ligaments, bones, etc. d. Elastin, found in elastic tissue. e. Keratin, found in skin and epidermic appendages, nails, hair, horn, etc. 6. FIBRIN. — A filamentous albumin obtained by washing blood clots. It is insoluble in water and mineral acids. 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, sugars, 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 greater 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, I Urates Creatinin, Hippuric Acid, Ammonium, Cholesterin, Calcium Oxalate, Calcium, 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. STRUCTURAL COMPOSITION OF THE BODY. 17 Proximate Quantity of the Chemical Elements and Proximate Principles of the Body, Weighing 154 Ibs. Ibs. 07.. 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 tissues 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 of the bocly, and may be classed in three groups, viz : i. Cells possessing a distinct cell wall, cell stibstance 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 g^Vtf to the ^00 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, unstable, insoluble in water, and known as protoplasm, bioplasm, sarcode, etc. ; in older cells the original cell substance undergoes various transform- ations, 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. 18 HUMAN PHYSIOLOGY. 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 bronchial 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. 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., cartilage, bone, dentine, etc. II. Limiting Membrane, a thin homogeneous membrane, structureless, FOOD. ' 19 composed of coagulated albumin, and often not more than the ^T5tf °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 nuchoe, vocal cords, ligamenta subflava, etc. IV. Compound membranes (membrano- cellular or fibro-cellular tissues), cells aggregated into laminse. (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. 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 20 HUMAN PHYSIOLOGY. 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 T4^, 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 Mtiscles 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 anoemia 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 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. FOOD. 21 The different alimentary principles which are appropriated by the system are combined in different proportions in the various articles of food, and are separated from the innutritious substances during the process of diges- tion. 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. Afyosin, syntonin, Flesh of animals. Vitellin, albumin, Yolk of egg, white of egg. Fibrin, globulin, Blood contained in meat. Casein, Milk, cheese. Gluten, Grain of wheat and other cereals. Vegetable albumin, 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. Itiosite, liver sugar, glycogen, . Muscles, 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 Palm itin, 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 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 ris'e 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 22 HUMAN PHYSIOLOGY. 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 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 meta- morphosis of the tissue is retarded, the elimination of urea and carbonic FOOD. 23 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- fecting 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. Bread, WATER. 77 ALBUMIN. 8.1 STARCH. 47.4 SUGAR. 7.6 FATS. 1.6 SALTS. 2-3 Milk, 86 4.1 ^ / *T^ o C.2 •3.Q 0.8 Eggs, • 74 I4.O 0 O y IO.C I.e Meat, . , Potatoes, , Corn, Oatmeal, Turnips, Carrots, Rice, . ... 54 ... 75 . ... 14 . ... 15 . . . .91 . . . .83 . n 27.6 2.1 II. I 12.6 1.2 i-3 6.T 18.8 64.7 58-4 % 7Q.I 3-2 0.4 5-4 2.1 6.1 0.4 * v» j 15-45 0.2 8.1 5-6 0.2 0.7 *.j 2-95 0.7 i-7 6 I.O O.S 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 elimi- nated 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 carbonaceous (bread) to nitrogenized (meat) food should be observed in the diet. 24 HUMAN PHYSIOLOGY. 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 : — 1000 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*4 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. #" 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 amount 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 mentioned, there are 4.2 oz. albumin, 9.3 sugar and starch. 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 maybe divided into seven stages: prehension, mastication, insalivatioa, deglutition, gastric and intestinal digestion and defecation. DIGESTION. 25 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-hyoid, mylo-hyoid and platysma myoitles muscles ; elevated by the temporal, 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 NERVES. 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 C 26 HUMAN PHYSIOLOGY. 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 the parotid, sub-ma xillary and sub-lingttal glands ; the pa rotid 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 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 a prolonged period of activity.— From Yeo's Text-Book of Physiology. 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., parotid, during rest, the secretory cells 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 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 DIGESTION. 27 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- 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, elabor- ate the mucigen which is discharged into the tubules during secretory activity, to become part of the secretion. FIG. 2. SECTION OF A " MUCOUS " GLAND. A. In a state of rest. B. After it has been for some time actively secreting. — After LM vdowsky . 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 of 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 stigar. This action is due to the presence of the organic ferment, ptyalin. Ptyalin is an amorphous nitrogenized substance, which can be precipitated from the saliva by calcium phosphate. Its power of converting starch into grape sugar is manifested most decidedly at the temperature of the living body and in a slightly HUMAN PHYSIOLOGY. alkaline medium. The change consists in the assumption of a molecule of water. Starch. Water. Grape Sugar. C6H1005 + H20 = C6H1206 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 submaxillary 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 vase-con- strictor nerve) and a diminution of the secretion, which now becomes thick 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 2d stage, which is entirely reflex, the palate is made tense and directed upward and backward by the levatores-palati and tensores-palati DIGESTION. 29 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 curvature, 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. One variety consists of 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 composed is finely granular. During the stage of active secretion the cells 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 gastric juice, begin to exude upon its surface, which gradually run together and trickle down the sides of the stomach. 30 HUMAN PHYSIOLOGY. 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 pneumogastric nerve. If during digestion, when the peristaltic movements 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 epi- thelium, viz., above cylindrical cells: small, pale cells in the lumen, outside which are the dark ovoid cells. — From Yea's Text-Book of Physiology. 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. 31 digestion afferent impulses are passing up the pneumogastrics to the medulla ; efferent impulses, in all probability, pass through the fibres of the sym- pathetic 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 to i.oio. COMPOSITION OF GASTRIC JUICE. Water, 975-°° 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 nitrogenized ferment of the gastric juice, and is formed, during the intervals of digestion, by the peptic cells. In the presence of a small per cent, of an acid, it acquires the property of con- verting the albumin 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 hydrochloro-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 21. 32 HUMAN PHYSIOLOGY. 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 albumin into acid albtimin or parapcptone ; while this intermediate product is being formed, the pepsin converts it at once into peptone. In order that the digestion of albumin 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. 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. 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 gastric juice. As soon as any portion of the food is digested, it passes through the pylorus into the intestine. DIGESTION. 33 TABLE SHOWING DIGESTIBILITY OF VARIOUS ARTICLES OF FOOD. HOURS. MINUTES. Eggs, whipped, I 20 " soft boiled, 3 " hard boiled, 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 « beans, " 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 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, \yz 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 valvuhe connivences. 34 HUMAN PHYSIOLOGY. 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, pan- creatic juice and bile. Throughout the mucous coat are imbedded the intestinal follicles, the glands of Brunner and Lieberkiihn. They secrete the true intestinal juice , which is an alkaline, viscid fluid, composed of water, organic matter and salts. \\s> function is to convert starch into glucose, and assist in the diges- tion 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. FIG. 4. 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, i. e., the part of the cells (a) next the lumen (c), is broad and filled with fine granules. B. After the gland has poured out its secretion, when the cell out- lines (d) are clearer, the granular zone (a) is smaller, and the clear outer zone is wider. —From Yto's Text-Book of Physiology, after Kiihne and Lea. The pancreas is similar in structure to the salivary glands, consisting ot 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 oziter parietal zone, which is transparent and appar- ently homogeneous, staining Vapidly 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. 35 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. 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 100000 The pancreatic juice is characterized by its action : ist. Upon starch. 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 albumin. The albuminous bodies are changed by the juice into, first, an alkali albumin, and then into peptone. The albumin 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 etnulsification 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 albumin present, combined with the intestinal movements. The neutral fats are also decomposed into their cor responding fatty 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. 36 HUMAN PHYSIOLOGY. 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 alkaline reaction and a specific gravity of 1.020. COMPOSITION OF BILE. Water, 859.2 Sodium glycocholate, ^ Sodium taurocholate, j 9I-4 Fat, 9.2 Cholesterine, 2.6 Mucus and coloring matter, 29.8 Salts, 7.8 1000.00 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. 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 cholesterczmia, attended with severe nervous symptoms. It is given off in the feces under the form of stercorine. The Coloring matters which give the tints to the bile are biliverdin and bilirubiny 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 2^ pounds. Functions of the Bile, (i) It assists in the emulsifi cation of the fats and promotes their absorption. (2) It tends to prevent putrefactive changes ABSORPTION. 37 in the food. (3) It stimulates the secretions of the intestinal glands, and excites the normal peristaltic movement 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, slercorin and salts ; varying in amount from 4 to 7 ozs. 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. ABSORPTION. The term absorption is applied to the passage or transference of material into the blood from the tissues, from the serous cavities, and from the mucous surfaces of the body. The most important of these surfaces, espe- cially in its relation to the formation of the blood, is the mucous surface of the alimentary canal ; for it is from this organ that new materials are de- rived which maintain the quality and quantity of the blood. The absorp- tion of materials from the interstices of the tissues is to be regarded rather as a return to the blood of liquid nutritive material which has escaped from the blood vessels for nutritive purposes, and which, if not returned, would lead to an accumulation of such fluid and the development of dropsical conditions. The anatomical mechanisms involved in the absorptive process are primarily, the lymph spaces, the lymph capillaries and blood capillaries ; secondarily, the lymphatic vessels and larger blood vessels. Lymph spaces, Lymph capillaries, Blood capillaries. Every- where throughout the body, in the intervals of connective tissue bundles, and in the interstices of the several structures of which an organ is composed, 38 HUMAN PHYSIOLOGY. are found spaces of irregular shape and size, determined largely by the nature of the organ in which they are found, which have been termed lymph spaces or lacuna, from the fact that during the living condition they are continu- ally receiving the lymph which has escaped from the blood vessels through- out the body. In addition to the connective tissue lymph spaces, various observers have described special lymph spaces in the testicle, kidney, liver, thymus gland, and spleen; in all secreting glands between the basement membrane and blood vessels; around blood vessels (perivascular spaces) and around nerves. The serous cavities 01 the body, peritoneal, pleura], pericardial, etc., may also be regarded as lymph spaces, which are in direct communication by open mouths or stomata with the lymphatic capillaries. This method of communication is not only true of serous membranes, but to some extent also of mucous membranes. The cylindrical sheaths and endothelial cells surrounding the brain, spinal cord and nerves, can also be looked upon as lymph spaces in connection with lymph capillaries. The lymphatic capillaries, in which the lymphatic vessels proper take their origin, are arranged in the form of plexuses of quite irregular shape. In most situations they are intimately interwoven with the blood vessels, from which, however, they can be readily distinguished by their larger calibre and irregular expansions. The wall of the lymph capillary is formed by a single layer of epithelioid cells, with sinuous outlines, and which accurately dove'tail with each other. In no instance are valves found. In the villus of the small intestine the beginning of the lacteal is to be regarded as a lymph capillary, generally club-shaped, which at the base of the villus enters a true lymphatic ; at this point a valve is present, which prevents regurgitation. The lymphatic capillaries anastomose freely with each other, and communicate on the one hand with the lymph spaces, and on the other with the lymphatic vessels proper. As the shape, size, etc., of both lymph spaces and capillaries are deter- mined largely by the nature of the tissues in which they are contained, it is not always possible to separate the one from the other. Their function, however, may be regarded as similar, viz : — the collection of the lymph which has escaped from the blood vessels, and its transmission onward into the regular lymphatic vessels. * The blood capillaries not only permit the escape of the liquid nutritive portions of the blood through their delicate walls, but are also engaged in the reabsorption of this transudate as well as in the absorption of hew materials from the alimentary canal. The extensive capillary network which is formed by the ultimate subdivision of the arterioles in the sub- mucous tissue and villi of the small intestine forms an anatomical arrange- ABSORPTION. 39 raent well adapted for absorption. It is now well known that in the absorption of the products of digestion the blood capillaries are more active than the lymphatic capillaries. Lymphatic Vessels. The lymphatic vessels constitute a system of minute, delicate, transparent vessels, found in nearly all the organs and tissues of the body. Having their origin at the periphery in the lymphatic capil- laries and spaces, they gradually converge toward the trunk of the body and empty into the thoracic duct. In their course they pass through numerous small ovoid bodies, the lymphatic glands. The lymphatic vessels of the small intestine (M°4° foot 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 opening 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 Pneumogastric (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- 56 HUMAN PHYSIOLOGY. 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. 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. ARTERIES. 57 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 peri- pheral resistance, lower the pressure. 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 oblongata. 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 ^Vtf to ^e 3uW °f an inch; their walls consist of a delicate homogeneous membrane, the E 58 HUMAN PHYSIOLOGY. 2(jtf(HF °f an *nch *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 adhere to the walls of the vessel, and at times can be seen to pass through the walls of the vessel by amoeboid movements. 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 — I . 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 inter- nal 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 respiration. 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 RESPIRATION. 69 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 Jj that of the carotid artery. The 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. 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 process ; 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. 60 HUMAN PHYSIOLOGY. 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 diminishing 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 branches, which penetrate the lung in every direction until they finally terminate in the pulmonary lobules. As the bronchial tubes become smaller their walls become thinner ; the cartilaginous rings disappear, but are replaced by irregular angular plates 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 distract 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 vesssls surrounding the air cells; the air and blood are thus brought into intimate relationship, being separated only by the delicate walls of the air cells and capillaries. The Diagram of the respiratory organs. "he windpipe leading down from th larynx is seen to branch into tw large bronchi, which subdivide after they enter their respective lungs. the wo RESPIRATION. 61 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, the 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. 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 accommodate 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 62 HUMAN PHYSIOLOGY. 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 calcu- lated 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. : — 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 elvation and rotation of the ribs upon their axes. In ordinary tranquil inspiration the muscles which elevate the ribs and thrust the sternum forward, and so increase the diameters of the chest, are the external inter costals, running from above downward and forward, the sternal portion of the internal intercostah 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 infracostal*, and the triangularis sterni. In the extraordinary efforts of expiration certain auxiliary muscles are brought into plaj, 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. RESPIRATION. 63 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 air from the chest. Nervous Mechanism of Respiration. The movements of Respira- tory 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, travel- ing outward through the phrenic and intercostal nerves, excite contractions 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 — 1. Directly ', by the condition of the blood. An increase of carbonic acid or a diminution of oxygen in the blood causes an acceleration of the respi- ratory 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 irritation of the terminal branches; and through the nerves of general sensibility. In either case this centre reflects motor impulses to the respiratory muscles through the 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 yth 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 arid 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. 64 HUMAN PHYSIOLOGY. 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 vesiciilar 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 Complemental 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 ordi- nary efforts of expiration, but which can be expelled by forcible expiration. The volume of reserve air is about 100 cubic inches. The Residual air is that portion which remains in the chest and cannot be expelled after the most forcible expiratory efforts, and which amounts, according to Dr. Hutchinson, to about 100 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. Chemistry of Respiration. As the inspired air undergoes a change RESPIRATION. 65 in composition during its stay in the lungs which renders it unfit for further respiration, it becomes requisite, for the correct understanding of respiration, to ascertain the composition of both inspired and expired air. Composition of Air. Chemical analysis has shown that every 100 vols. of air contains 20.81 vols. of oxygen, and 70.19 vols. of nitrogen, and 0.03 vol. of carbonic acid. Aqueous vapor is also present, though the quantity is variable. The higher the temperature the greater the amount. 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 water vapor and organic matter. Elevation of temperature. Increase and at times decrease of nitrogen. Gain of ammonia. The total qtiantity 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 1080 inches, and in 24 hours, 25,920 cubic inches or 15 cubic feet, weighing 18 oz. To obtain this quantity, 300 cubic feet of air are necessary. The quantity of oxygen consumed daily is subject to considerable varia- tion. It is increased by exercise, digestion and lowered temperature, and decreased by the opposite conditions. 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 ~f- 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. 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. As there is always more oxygen consumed than carbonic acid exhaled, and as oxygen unites with carbon to form an equal volume of carbonic acid, it is evident that a certain quantity of oxygen disappears within the body. In all probability it unites with the sulphur hydrogen of the food to form water. 66 HUMAN PHYSIOLOGY. The amount of watery vapor which passes out of the body with the expired air amounts to from one to two pounds. The organic matter, though slight in amount, gives the odor to the breath. In a room with defective ventilation, the organic matter accumulates and gives rise to headache, nausea, drowsiness, etc. Long continued breathing of such air produces general ill health. It is not so much the presence of CO2 in increased amount, as the presence of organic matter which neces- sitates thorough ventilation. 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 bi'carbonates. Nitrogen is simply held in solution in the plasma. Exchange of Gases in the Air Cells. From the difference in tension of the oxygen in the air cells (27.44 mm. of Hg), and of the oxygen in the venous blood (22 mm. Hg), and of the difference of the carbonic acid tension in the venous blood (41 mm. Hg), and in the air cells (27 mm. Hg), it might be concluded that the passage of the gases might be due solely to pressure. The absorption of oxygen, however, does not follow absolutely the law of pressures ; that chemical processes are involved is shown by the union of oxygen with the haemoglobin of the blood corpuscles. The exhalation of CO 2 is also partly a chemical process, as it has been shown that the quan- tity excreted is greatly increased when oxygen is simultaneously absorbed. Oxygen not only favors the exhalation of loosely combined CO2, but favors the expulsion of that which can only be excreted by the addition of acids to the blood. 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 red 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 ANIMAL HEAT. 67 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- 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 normal tem- 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 diurnal variation of the temperature occurs from 1.8° F. to 3.6° F. (Jiirgensen); 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 68 HUMAN PHYSIOLOGY. 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. 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 i° 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. : — I. During mental activity the brain receives nearly one-fifth of the SECRETION. 69 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. 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 tfcat 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 70 HUMAN PHYSIOLOGY. organs, ) Centripetal or afferent if in the reverse direction. 98 HUMAN PHYSIOLOGY. Special stimuli : — 1. Light or ethereal vibrations acting upon the end organs of the optic nerve in the retina. 2. Sound or atmospheric undulations acting upon the end organs of the auditory nerve. 3. Heat or vibrations of the air acting upon the end organs in the skin. 4. Chemical agencies acting upon the end organs of the olfactory and gustatory nerves. As to the nature of the nerve impulse generated by the above stimuli but little is known. It is supposed to be a mode of motion, molecular or vibratory in character, which passes through the axis cylinder with a definite velocity. Rapidity of Transmission of Nerve Force. The passage of a nervous impulse, either from the brain to the periphery or in the reverse direction, requires an appreciable period of time. The velocity with which the impulse travels in human sensory nerves has been estimated at about 190 feet per second, and for motor nerves at from 100 to 200 feet per second. The rate of movement is, however, somewhat modified by temperature, cold lessening and heat increasing the rapidity ; it is also modified by electrical conditions, by the action of drugs, the strength of the stimulus, etc. The rate of transmission through the spinal cord is considerably slower than in nerves, the average velocity for voluntary motor impulses being only 33 feet per second, for sensitive impressions 40 feet, and for tactile impressions 146 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 I ^ inches long, and possesses a delicate homogeneous membrane, the sarcolemma, in the interior 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 PROPERTIES AND FUNCTIONS OF NERVES. 99 inorganic salts. When at rest the muscle is alkaline in reaction, but during and after contraction it becomes acfd. 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^ff of a second, but varies with the temperature, the strength of the stimulus, the animal, etc. The muscular movements of the body, however, are occasioned by contractions of a much longer duration, depend- ing 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, a change from an alkaline to an acid reaction, from the development of sarcolactic acid; a disappearance of the natural muscle currents, which under 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 Currents in Muscles and Nerves. If a muscle or nerve be divided and non-polarizable electrodes be placed upon the natural longitudinal surface at the equator, and upon the transverse section, electri- 100 HUMAN PHYSIOLOGY. cal currents are observed with the aid of a delicate galvanometer. The direction of the current is always from the positive equatorial surface to the negative transverse surface. The strength of the current increases or dimin- ishes according as the positive electrode is moved toward or from the equator. When the electrodes are placed on the two transverse ends of a nerve, an axial current will be observed whose direction is opposite to that of the normal impulse in the nerve. The electromotive force of the strongest nerve current has been estimated to be equal to the 0.026 of a Daniell battery ; the force of the current of the frog muscle about 0.05 to 0.08 of a Daniell. Negative Variation of Currents in Muscles and Nerves. If a muscle or nerve be thrown into a condition of tetanus, it will be observed that the currents undergo a diminution or negative variation, a change which passes along the nerve in the form of a wave and with a velocity equal to the rate of transmission of the nerve impulse. The wave length of a single negative variation has been estimated to be 18 millimetres; the period of its duration being from 0.0005 to 0.0008 of a second. It is asserted by Hermann that perfectly fresh, uninjured muscles and nerves are devoid of currents, and that the currents observed are the result of a molecular death at the point of section, this point becoming negative to the equatorial point. He applies the term " action currents " to the cur- rents obtained when a muscle is thrown into a state of activity. 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 current 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 PROPERTIES AND FUNCTIONS OF NERVES. 101 or negative pole; the increase of excitability in the katelectrotonic 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 katelectrotonic 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 tempera- ture, chemical composition or physical condition. The natural nerve cur- rents, 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, under- going a negative variation. 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 excita- bility to the galvanic current. The synchronous diminished excitability of the nerves is the same for either current. The term partial reaction 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. 102 HUMAN PHYSIOLOGY. 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 : — 1st 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. I ith Pair, or Spinal accessory. 6th Pair, or Abducens. 1 2th 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. 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 cerebrum ; an internal white root, from the most posterior part of the anterior lobe ; &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 downward, 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. CRANIAL NERVES. 103 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 a broad 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. 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. Hemiopia and Hemianopsia. Owing to the decussation of the fibres in the optic chiasm 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, the blind part being separated from the normal part by a vertical line. The term hemiopia is applied to the loss of function or paralysis of the one-half of the retina; hemianopsia is applied to the blind- ness in the field of vision. If, for example, the right optic tract be divided, there will be hemiopia in the outer half of the right eye and inner half of left eye, thus causing left lateral hemianopsia, and as the two halves are affected which correspond in normal vision, it is spoken of as homonymous hemianopsia. Lesion of the anterior part of the optic chiasm causes blind- ness in the inner half of the two eyes. 104 HUMAN PHYSIOLOGY. 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 three sets of filaments coming from the oculo-motorius nucleus, which lies under the aqueduct of Sylvius; these three groups of filaments are destined for the innervation of the muscles of the eyeball, the sphincter pupilbe, and the ciliary muscle. By filaments coining 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 levator palpebra 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 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 CRANIAL NERVES. 105 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. 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 * 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. H 106 HUMAN PHYSIOLOGY. 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 Varolli. 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- maxillary ganglion, the parotid and sub-lingual glands, external auditory meatus, mucous membrane of the mouth, 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 to 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 CRANIAL NERVES. 107 root, which then divides into an anterior and posterior branch, the former of which is distributed to the muscles 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 motion. The integument, mucous membranes and .the eye may be lacerated, cut or bruised, 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 discharged, 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. 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. 108 HUMAN PHYSIOLOGY. 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 margin of the pons Varolii. Deep Origin. From a nucleus of large cells in the floor of the 4th ventricle, 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. 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 ternporo-fadal and cervico-facial branches, which are distributed to the superficial muscles of the face, viz. ; occipito-frontalis, corrugator supercilii, orbicularis palpebrarum, levator labii superioris et alaeque nasi, buccinator, levator anguli oris, orbicularis oris, zygomatici, depressor anguli oris, platysma myoides, etc. CRANIAL NERVES. 109 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 o(f 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 uvulae 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 Tympanitic branch animates the stapSdius 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 and 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 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 oblongata, just below the margin of the pons Varolii. 110 HUMAN PHYSIOLOGY. 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 membrane of the pharynx. 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). CRANIAL NERVES. Ill Function. Governs sensibility of pharynx, presides partly over the sense of taste, and controls reflex movements of deglutition and vomiting. roth 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. 3. Inferior laryngeal, which sends its ultimate branches to all the intrinsic muscles of the larynx except the crico-thyroid, and to the inferior constrictor of the pharynx. 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. 112 HUMAN PHYSIOLOGY. From the right pneumogastrlc 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 membrane 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. The Pulmonary branches give sensibility to the bronchial mucous membrane, and govern the movements of respiration. Division of both pneumogastrics in the neck diminishes the frequency of the respiratory movements, 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 CRANIAL NERVES. 113 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 medtdlary 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 elongated 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, 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 114 HUMAN PHYSIOLOGY. 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 pneumogostric 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 andsterno-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. I2th 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 filament CEREBRO-SPINAL AXIS. 115 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- gastrtc 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, 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. 116 HUMAN PHYSIOLOGY. 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 processes inward, forming the falx cerebri, falx cerebelli, and tentorium cerebelli, 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 albumen, glucose and mineral salts. It is secreted by the pia mater; the quantity is estimated from two to four fluid ozs. The 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. SPINAL CORD. The Spinal Cord varies from 16 to 18 inches in length; is half an inch in thickness, weighs i^ oz., and extends from the atlas to the 2d lumbar vertebra, terminating in the filum terminale. 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 SPINAL CORD. 117 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: (i) An Anterior column, comprising that portion between the anterior roots and the anterior fissure, which is again subdivided into two parts : (#) an inner portion, bordering the anterior median fissure, the direct pyramidal tract, or column of Turck, containing motor fibres which do not decussate, and which extends as far down as the middle of the dorsal region ; (£) 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, occupy- ing the posterior portion of the lateral column, and containing all those fibres of the motor tract which have decussated at the medulla oblongata ; it is com- posed of longitudinally running fibres which are connected with the multipolar nerve cells of the anterior cornua ; (b} the direct cerebellar tract, situated upon the surface of the lateral column, consisting of longitudinal fibres which terminate in the cere- bellum ; 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 SCHEME OF THE CONDUCTING PATHS IN THE SPINAL CORD AT THE 3D DORSAL NERVE. The black part is the gray matter, v, anterior, hw, posterior, root ; a, direct, and g, crossed, pyramidal 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. 118 HUMAN PHYSIOLOGY. portion, the postero-internal column, or the column of Goll, bordering the posterior median fissure, and (<5) an external portion, the poster o- external column, the column of Burdach, lying just behind the posterior roots. They are composed of long and short commissural fibres which connect together different segments of the spinal cord. Structure of the Gray Matter. The gray matter, arranged 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 frame work 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 margin, and in the caput cornu. Small cells are also found in the posterior vesicular columns, and in the intermediary lateral tract. 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 nerve; for if the nerve be separated from the ganglion, it undergoes degeneration 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 SPINAL NERVES. 119 degeneration. 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. 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 corptts 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 (l) through the substantia gelatinosa, (2) through the posterior columns; of the former, some bend upward and downward, and become connected with the anterior cornuae ; 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. Decussation of Motor and Sensory Fibres. The Motor fibres, which conduct volitional impulses from the brain outward to the anterior cornuae, 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 Tiirck. 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. 120 HUMAN PHYSIOLOGY. FIG. 32. 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 l 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 matter and become connected with the muscles, M, through the multipolar cells ; the smaller Portion, three per cent., does not cross over, but descends on the same side of the cord in the anterior column and supplies the muscles, m. The same is true for the 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. PROPERTIES OF THE SPINAL CORD. 121 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 decus- sation 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 posterior median fissure. The sensibility is due, however, not to its own proper fibres, but to the fibres of the posterior root which traverse it. Division of the antero-lateral columns abolishes all power of voluntary movement in the lower extremities. Division of i\\e 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 : — (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 ; hypersesthesia 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 part's 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. 122 HUMAN PHYSIOLOGY. FUNCTIONS OF THE SPINAL CORD, 1. As a 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 move- ments in walking, standing, running, etc. Degeneration of the posterior columns gives rise to the lack of muscular coordination observed in loco- motor 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 cornua 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 muscu- lar fibres to which they are distributed. The anterior roots give passage to the vaso-constrictor and vaso dilator fibres which exert an influence 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 move- ments. 2. As an Independent Nerve Centre. The spinal cord, by virtue of its contaiaing 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. FUNCTIONS OF THE SPINAL CORD. 123 The reflex excitability of the cord may be — 1. 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 depressing its reflex activity. 2. Inhibited \yy destructive lesions of the cord, e.g., locomotor ataxia, atrophy of the anterior cornuae, 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 movement 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 idea- 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. g., tetanus, vomiting, epilepsy, which take place both centripetally and centrifugally, 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 metaslatic ', e.g., ophthalmia, coryza, orchitis, which depend on a reflex hypersemia; 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 obscure reflex actions which preside over the secretions of the intestinal fluids, which unite the phenomena of the generative organs, the dilatation 124 HUMAN PHYSIOLOGY. 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 gen- eral, and it 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 Reflex Movements. There are a number of reflex movements taking place through the spinal cord, a study of which enables the physician to determine the condition of its different segments. They may be divided into, I. Skin or superficial, and 2. Tendon or deep reflexes. The skin reflexes are induced by irritation of the skin and mucous membranes, e.g., pricking, pinching, scratching, etc. The following are the principal skin reflexes : — 1. Plantar reflex, consisting of contraction of the muscles of the foot, induced by stimulation of the sole of the foot ; it involves the integrity of the reflex arc through the lower end of the cord. 2. Ghiteal reflex, consisting of contraction of the glutei muscles when the skin over the buttock is stimulated ; it takes place through the segments giving origin to the fourth and fifth lumbar nerves. 3. Cremasteric reflex, consisting of a contraction of the cremaster muscle, and a retraction of the testicle toward the abdominal ring, when the skin on the .inner side of the thigh is stimulated; it depends upon the integrity of the segments giving origin to the first and second lumbar nerves. 4. Abdominal reflex, consisting of a contraction of the abdominal mus- cles when the skin upon the side of the abdomen is gently scratched ; its FUNCTIONS OF THE SPINAL CORD. 125 production requires the integrity of the spinal segments from the eighth to the twelfth. 5. Epigastric reflex, consisting of a slight muscular contraction in the neighborhood of the epigastrium when the skin between the fourth and sixth ribs is stimulated ; it requires the integrity of the cord between the fourth and seventh dorsal nerves. 6. Scapular reflex consists of a contraction of the scapular muscles when the skin between the scapula is stimulated; it depends upon the integrity of the cord between the fifth cervical and third dorsal nerves. The superficial reflexes, though variable, are generally present in health. They are increased or exaggerated when the gray matter of the cord is abnormally excited, as in tetanus, strychnia poisoning, and in disease of the lateral columns, leading to arrest of their normal functions. The Ten- don or deep reflexes are also of great value in diagnosing the condition of the spinal segments. They are induced by a sharp blow upon a tendon. The following are the principal forms : — 1. Patella reflex or Knee jerk, consisting of a contraction of the extensor muscles of the thigh when the »ligamentum patella is struck between the patella and tibia. This reflex is best observed when the legs are freely hanging over the edge of a table. The patella reflex is generally present in health, being absent in only 2. per cent. ; it is greatly exaggerated in lateral sclerosis, in descending degeneration of the cord ; it is absent in locomotor ataxia and in atrophic lesions of the anterior gray cornuse. 2. Ankle jerk or rejlex. If the extensor muscles of the leg be placed upon the stretch and the tendo-achillis be sharply struck, a quick extension of the foot will take place. 3. Ankle clonus. This consists of a series of rhythmical reflex con- tractions of the gastrocnemius muscle, varying in frequency from 6 to 10 per second. To elicit this reflex, pressure is made upon the sole so as to suddenly and energetically flex the foot at the ankle, thus putting the tendo- achillis upon the stretch. The rhythmical movements thus produced con- tinue so long as the tension is maintained. Ankle clonus is never present in health, but is very marked in lateral sclerosis of the cord. The toe reflex, peroneal reflex, wrist reflex are also present in sclerosis of the lateral columns and in the late rigidity of hemiplegia. Special Nerve Centres in Spinal Cord. Throughout the spinal cord there are a number of special nerve centres, capable of being excited reflexly and producing complex coordinated movements. Though for the most part independent in action they are subject to the controlling influences of the medulla and brain. 126 HUMAN PHYSIOLOGY. 1. Cilio-spinal centre, situated in the cord between the lower cervical and .third dorsal vertebra. It is connected with the dilatation of the pupil through fibres which emerge in this region and enter the cervical sympa- thetic. Stimulation of the cord in this locality causes dilatation of the pupil on the same side ; destruction of the cord is followed by contraction of the pupil. 2. Genito-spinal centre, situated in the lower part of the cord. This is a complex centre and comprises a series of subordinate centres for the con- trol of the muscular movements involved in the acts of defecation, micturi- tion, ejaculation of semen, the movements of the uterus during parturition, etc. 3. Vasomotor centres, giving origin to both vaso-constrictor and vaso- dilator fibres, which are distributed throughout the cord. Though acting reflexly they are under the dominating influence of the centre in the me- dulla. 4. Sweat centres are also present in various parts of the cord. Paralysis from Injuries of the Spinal Cord. Seat of Lesion. If it be in the lower phrt of the sacral canal, there is paralysis of the compressor urethrse, accelerator urinre, 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. MEDULLA OBLONGATA. 127 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 FIG. 13. VIEW OF CEREBELLUM IN SECTION, AND OF FOURTH VENTRICLE, WITH THE NEIGHBORING PARTS. (From Sappey.) i. Median groove fourth ventricle, ending below in the calamus scriptorius, with the longitudinal eminences formed by the fasciculi teretes, one on each side. 2. The same groove, at the place where the white streaks of the auditory nerve emerge from it to cross the floor of the ventricle. 3. Inferior peduncle of the cerebellum, formed by the restiform body. 4. Posterior pyramid : above this is the calamus scriptorius. 5. Supe- rior peduncle of cerebellum, or processus e cerebello ad testes. 6 6. Fillet to the side of the crura cerebri. 77. Lateral grooves of the crura cerebri. 8. Corpora quad- rigemina, — After Hirschfeld and Leveille. half is again subdivided by minor grooves, into four columns, viz. : anterior pyramid, lateral tract and olivary body, restiform body and posterior pyramid. I. 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 128 HUMAN PHYSIOLOGY. 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 ; 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 pyramid ; a middle bundle ascends beneath the olivary body, behind the pons, to the cerebrum, as \\~\o. 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 exter- nally 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 sen- sitive 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 conductor of coordinating impulses from the cerebellum, through the 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. : — I. A centre which controls the movements of mastication, through afferent and efferent nerves. (See page 25.) Motor or MEDULLA OBLONGATA. 129 2. A centre reflecting impressions which influence the secretion of saliva. (See page 28.) 3. A centre for sucking, mastication and deglutition, whence are derived 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 (" Palatal branch of 5th pair. or Pharyngeal branches of the glosso pharyngeal. Centripetal Superior laryngeal branches of the pneumogastric. Nerves. [ (Esophageal branches of the pneumogastric. Pharyngeal branches of the pneumogastric, derived from the spinal accessory. Hypoglossal and branches of the cervical plexus. Centrifugal Inferior or recurrent laryngeal. Nerves. Motor filaments of the 3d division of the 5th pair. Portio dura. 4. A centre which coordinates the muscles concerned in the act ot 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. The cardio-inhibitory centre is in a state of tonic excitement and continuously sending impulses to the heart which exert an inhibitory influence upon its action. It may be stimulated directly by ancemia as well as venous hyperaetniaof the blood vessels of the medulla and increased venosity of the blood. It is excited reflexly by the stimula- tion of the central end of the vagus, sciatic and splanchnic nerves. 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 quadrigemina 130 HUMAN PHYSIOLOGY. 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 sympathetic, and thence pass to the walls of the blood vessels, and maintain the arterial tonus ; they may be divided into two classes, viz.; vaso-dilators, e.g., chorda tympani, and vase-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- sure. Galvanic stimtdation of the divided surface of the cord is followed by a contraction of the blood vessels and a rise in the blood pressure. The vasomotor centre is stimulated directly by the condition of the blood in the medulla oblongata. When it is highly venous it becomes very active and the blood vessels throughout the body are contracted and the blood current becomes swifter; sudden anaemia of the medulla has a similar effect. This centre may be increased in action with attendant rise of blood pressure, by irritation of certain afferent nerve fibres. These are known as pressor fibres. On the other hand, its action may be depressed by other afferent fibres with attendant fall of blood pressure. These are known as depressor fibres. 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 dimin- ishing 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. or I Superior laryngeal. n . \ Trifacial, or 5th pair. Nerves Nerves of &™^ sensibility- [ Sympathetic nerve. CRURA CEREBRI. 131 -_ f Phrenic, distributed to the diaphragm. | Intercostals, distributed to the intercostal muscles. r °.rf , -j Facial nerve, or portio dura, to the facial muscles. Centntuga External branch of spinal accessory, to the trapezius erves. an(j 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 longfaidinal 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, 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 portion 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 impressions into conscious sensations, and originate motor impulses, these taking place independent of any intellectual process; they are the seat of instinctive reflex acts; the centres which assist in the coordination of the automatic 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, constitute the motor tract, which terminates, for the most part, in the corpus 132 HUMAN PHYSIOLOGY. striatum, but to some extent, also, in the cerebrum; the deep portion, 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 muscular movements; section of one crus 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 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 genictilata 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- CORPORA STRIATA AND OPTIC THALAMI. 133 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 narrow band of white matter, into two portions, viz : — 1. The Caudate nucleus, the intraventricular portion, which is conical in shape, having its apex directed backward, as a narrow, tail-like process. 2. The Lenticular mtcleus, 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; and between it and the convolutions of the island of Reil, a thin band of gray matter, the claustrum ; 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 o/ 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, 134 HUMAN PHYSIOLOGY. 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 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 opposite 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 fossae 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 CEREBELLUM. 135 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 quadrigemina and the optic thalami, and then forming part of the diverging cerebral 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 denlatum. From the external surface of the stem of white matter processes are given off, forming the lamince, 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 the pia mater, contain- ing rounded corpuscles, and branching fibres passing toward the external surface. 2. The cells of Purkinje, forming a layer of la-ge, nucleated, branched nerve cells sending off processes to the external layer. 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 cerebullum is not followed 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 movements become more irregular, and the pigeon becomes restless ; when the last portions are removed, all power Q{ 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 evacua- tions. Forced Movements. Division of one crus cerebelli causes the animal 136 HUMAN PHYSIOLOGY. 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 \r\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 character, 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. The Cerebrum is the largest portion of the encephalic mass, constituting 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 dis- tributed to it by the carotid and vertebral arteries. These vessels anastomose 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 sus- pension of its functional activity. The cerebrum is connected with the pons Varolii and medulla oblongata through the crura cerebri, and with the cerebellum, through the superior 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 CEREBRUM. 137 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 frojiial 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 down- ward toward the fissure of Sylvius, but does not enter it. It separates the frontal from the pajietal lobe. 3. The Parietal fissure, arising a short distance behind the fissure of ^ Rolando, upon the convexity of the hemisphere, runs downward and back- ward to its posterior extremity. 4. The Parieto-occipilal fissure separating the occipital from the parietal lobes. Beginning upon the outer surface of the cerebrum, it is continued on the mesial aspect downward and forward until it terminates in the calca- rine fissure. \ 5. The Calloso-marginal fissure lying upon the mesial surface, where it runs parallel with the corpus callosum. 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 ; in the temporo-sphenoidal lobes are found the first and second temporo- sphenoidal fissures ; in the occipital lobe, the calca rine and hippo-campal 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. 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. J 138 HUMAN PHYSIOLOGY. The Inferior frontal convolution winds around the ascending branch of the fissure of Sylvius, in the anterior and inferior portion of the cerebrum. Parietal Lobe. The Ascending parietal convolution is situated just behind 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. FIG. 14. DIAGRAM SHOWING FISSURES AND CONVOLUTIONS OF THE LEFT SIDE OF THE HUMAN BRAIN. F, frontal ; P, parietal ; O, occipital ; T, temporo-sphenoidal lobe ; S, fissure of Sylvius ; S', horizontal ; S", ascending ramus of S ; c, sulcus centralis, or fissure of Rolando; A, ascending frontal, and B, ascending parietal, convolution ; FI, superior ; F2, middle, and F3, inferior frontal convolutions ; f1; superior, f2, inferior, frontal fissures ; fg. sulcus praecentralis ; P, superior parietal lobule ; P2, inferior parietal lobule, con- sisting of p2, supra-marginal gyrus, and P'2, angular gyrus ; z"/, sulcus interparietalis ; c m, termination of calloso-marginal fissure; Oj, first, O2, second, O3, third, occipital convolutions ; p , inferior longitudinal occipital fissure; Tj, first, T2, second, T3, temporo-sphenoidal, convolu- tions,^, first, /3, second, temporo-sphenoidal fissures. — Landois' Physiology. CEREBRUM. 139 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. Temporo-sphenoidal Lobe. Contains three well-marked convolu- tions, 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 con- tains 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 temporo-sphenoidal lobes. Upon the inner or mesial aspect of the hemisphere are found (Fig. 15) — 1. The Par acentral lobule, lying in the region of the upper extremity of the fissure of Rolando; it contains the large giant cells of Betz. Injury to this convolution is followed by degeneration of the motor tract. 2. The Gyrus fornicatus, lying below the calloso-marginal fissure. Running parallel with the corpus callosum, it terminates at its posterior border in the hippocampal gyms. 3. The Gyrus hippocampus (H) is formed by the union of the preceding convolution with the occipito-temporal. It runs forward and terminates in a hooked extremity — uncus. 4. The Quadrate lobule or precuneus lies between the upper extremity of the calloso marginal fissure and the parieto-occipital. 5. The Cuneus lies posteriorly to the quadrate lobule. It is a wedge- shaped mass enclosed by the calcarine and parieto-occipital fissures. 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 formation 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 140 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. FIG. 15. * c B po DIAGRAM SHOWING FISSURES AND CONVOLUTIONS ON MESIAL ASPECT OF THE RIGHT HEMISPHERE. Median aspect of the right hemisphere. CC, corpus callosum divided longitudinally : Gf, gyrus fornicatus ; H, gyms hippocampi; h, sulcus hippocampi; TJ, uncinate gyms ; cm, calloso-marginal fissure ; F, first frontal convolution ; c, terminal portion of fissure of Rolando ; A, ascending frontal ; B, ascending parietal convolution and paracentral lobule; PI', praecuneus or quadrate lobule; Oz, cuneus ; Po, parieto- occipital fissure; o\, transverse occipital fissure; oc, calcarine fissure; oc' , superior, oc" , inferior ramus of the same ; D, gyrus descendens ; T4, gyrus occipito-temporalis lateralis (lobulus fusiformis) ; T5, gyrus occipito-temporalis medialis (lobulus lin- gualis). 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. FIG. 16. SIDE VIEW OF THH 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. (6) 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 oppo- site side. (9), (10) Opening of the mouth, with (9) protrusion and (10) retraction of the tongue; region of aphasia, bilateral action. (n) 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. 141 142 HUMAN PHYSIOLOGY. 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 functions 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 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 move- ments. 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- CEREBRAL LOCALIZATION OF FUNCTION. 143 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 phenomena 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 paralysis, 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 arranged along either side of the fissure of Rolando. This area is known as the motor area or motor zone, stimulation of which is followed by convulsive movements of the muscles of the opposite side of the body, while destruc- tion of the gray matter of this area is followed by permanent paralysis of the muscles of the opposite side. From experiments made upon monkeys, Ferrier has mapped out a number of motor centres which he has transferred to corresponding localities on the human brain (see Fig. 16). The descrip- tive test of the figure renders his results intelligible. Pathological studies have largely confirmed his deductions. In a general way it may be said that 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 experiments of Horsley and Schafer have enabled them to furnish a new diagrammatic representation of the motor area and to more accurately define the special areas upon the lateral and mesial aspects of the brain of the monkey. The boundaries of the general and special areas as deter- 144 HUMAN PHYSIOLOGY. mined by these observers will be readily understood by an examination of Figures 17 and 18. For diagnostic purposes the motor areas for the face and limbs have been subdivided as follows : — 1. The face area may be divided into an upper part comprising about one-third, and a lower part comprising the remaining two-thirds. In the upper part are centres governing the movements of the muscles of the oppo- site angle of the mouth and of the lower face. The anterior portion of the lower two-thirds controls the movements of the vocal cords and may be regarded as a laryngeal centre; the posterior portion governs the opening and shutting of the mouth and the protrusion and retraction of the tongue. 2. The upper limb area may be subdivided as follows : The upper part FIG. 17. DIAGRAM OF THE MOTOR AREAS ON THE OUTER SURFACE OF A MONKEY S BRAIN. Horsley and Schafer. controls the movements of the shoulder; posterior and below this point are centres for the elbow ; below and anteriorly, centres for the wrist and finger movements, while lowest and posteriorly centres governing the thumb. 3. The leg area may be subdivided as follows : The anterior part, both on the mesial and lateral surfaces, contains centres governing the hip and thigh movements; in the posterior part are centres for the movements of the leg and toes. The centre for the big toe has been located in the para- central lobule. 4. The trunk area, situated largely on the mesial surface, contains anteriorly centres governing the rotation and arching of the spine, while posteriorly are found centres governing movements of the tail and pelvis. 5. The head area, or area for visual direction, contains centres, excita- CEREBRAL LOCALIZATION OF FUNCTION. 145 tion of which causes " opening of the eyes, dilatation of the pupils and turning of the head to the opposite side with conjugate deviation of the eyes to that side." The centres of origin of the nerves for the ocular muscles lie in the gray matter of the aqueduct of Sylvius. Destruction of 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. Cerebral or Jacksonian epilepsy is a result of local cortical disease. Centre for Speech. Pathological investigations have demonstrated that the left third frontal convolution is of essential importance for speech. FIG. 18. DIAGRAM OF THE MOTOR AREAS ON THE MARGINAL CONVOLUTION OF A MONKEY'S BRAIN. — Horsley and Schafer. Adjoining this convolution are the centres controlling the motility of the lips, tongue, etc. In the majority of the cases the speech centres are on the left side of the brain, though in exceptional cases it is on the right side, especially in left-handed people. In deaf-mutes this convolution is very imperfectly developed, while in monkeys it is quite rudimentary. 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 com- plete loss of the power of articulate speech. Aphasia is of many degrees and kinds. In ataxic aphasia the patient is unable to communicate his thoughts by words, there being an inability to execute the movements of the mouth, etc., necessary for speech. In 146 HUMAN PHYSIOLOGY. FIG. 19. agraphic aphasia there is an inability to execute the movements necessary for writing, though the mental processes are retained. In the ataxic form the lesion is in the 3d frontal convolution, and in the agraphic form it is in the arm centre. In Amnesic Aphasia there is a loss of the memory of words, the purest examples of which consist of the affections known as word deafness and word blindness. In word deafness the patient cannot understand vocal speech, though he is capable of hearing other sounds. This condition is associated with lesion of the first temporal convolution. In word blindness the patient cannot name a letter or a word when printed or written, though he can see all other objects. This condition is associated with impairment of the visual centres. Figure 19 will illustrate the conditions in the various forms of aphasia. Impres- sions are constantly passing from eye and ear to the visual and auditory centres and there registered. Com- missural fibres connect these centres with the arm and speech centres, which in turn are connected by efferent fibres with the muscles of the hand and vocal appa- ratus. Muscular movements of the eyes, hand and mouth are also registered by means of the afferent fibres s, s', s". Sensory Centres. These are the centres in which the sensory impressions are co- ordinated, 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 SYMPATHETIC NERVOUS SYSTEM. 147 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 hemispheres 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 complete 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 centre for tactile impressions was located by Ferrier in the hippo- campal region. Horsley and Schafer found that destructive lesions of the gyrus fornicatus was followed by hemianaesthesia of the opposite side of the body, which was more or less marked and persistent. These observers conclude that the limbic lobe " is largely, if not exclusively, concerned in the appreciation of sensations painful and tactile." The Superior and Middle Frontal convolutions appear to be the seat of the reason, intelligence and will. Destruction of these parts is fol- lowed by proportional hebetude, without any impairment of sensation or motion. 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 ganglionic cords are connected together in the interior of the cranium by the ganglion of Ribes, on the anterior communicating artery, and terminate in the gan- glion impar, situated at the top 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, bundles of non-medullated nerve fibres, imbedded in a capsule of connective tissue. 148 HUMAN PHYSIOLOGY. The ganglia are reinforced by motor and sensory fibres from the cerebro- spinal nervous system. The Ganglia have distinct nerve fibres from which branches are dis- tributed to the 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 distribution are the ciliary nerves, which consist of — 1. Motor fibres for the circular fibres of the iris and ciliary muscle. 2. Sensory fibres for the cornea, iris and associated parts. 3. Vasomotor fibres for the blood vessels of the choroid, iris and retina. 4. Motor fibres for the dilator fibres of the iris. 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 filaments from the chorda tympani, sensory filaments from the lin- gual branch of the 5th nerve, and filaments from the sympathetic. The chorda tympani nerve supplies vaso-dilator and secretory fibres to the sub- maxillary and sub-lingual glands. The fifth nerve endows the glands with sensibility, while the sympathetic supplies secretory or trophic fibres. 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 SYMPATHETIC NERVOUS SYSTEM. 149 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 cceliac 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 vertebrae; 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 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 150 HUMAN PHYSIOLOGY. 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. Galvanization ot the upper end of the divided nerve causes all of the preceding 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 fol- lowed by a dilatation of the vessels, an increased rapidity of the circulation, and an elevation of temperature in the anterior and posterior limbs ; gal- vanization of the peripheral ends of these nerves causes all of these phe- nomena 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- obi ongata, 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 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 vasomoter nerves, producing a con- dition of physiological ancemia and sleep; during this state waste products are removed, force is stored up, nutrition is restored, and waking finally occurs. THE SENSE OF TOUCH. 151 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 structures 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., 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 enable 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 smoothness, is estimated by the impressions made upon the tactile papillae. Appreciation of Temperature. The general surface of the body is more 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. 152 HUMAN PHYSIOLOGY. The 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 sensitive 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 tem- peratures most readily appreciated are those between 50° F. and 115° F. The sensations 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 movements 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 papillae 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. Tb& 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 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 THE SENSE OF TASTE. 153 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 3-^ of an inch in length, situated in the epithelial covering of the mucous membrane, on the circumvallate papillce. 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 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. K 154 HUMAN PHYSIOLOGY. 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 odorous impressions is the part lining the upper one-third of the fossse. 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. The Eyeball. The eyeball or organ of vision is situated at the fore part of the orbital cavity and supported by a cushion of fat; it is protected from injury by the bony walls of the cavity, the lids and lashes, and is so THE SENSE OF SIGHT. 155 situated as to permit of an extensive range of vision. The eyeball is loosely held in position by a fibrous membrane, the capsule of Tenon, which is attached on the one hand to the eyeball itself and on the other to the walls of the cavity. Thus suspended, the eyeball is capable of being moved in any direction by the contraction of the muscles attached to it. Structure. The eyeball is spheroidal in shape and measures about nine- tenths of an inch in its antero-posterior diameter, and a little less in its transverse diameter. When viewed in profile it is seen to consist of the segments of two spheres, of which the posterior is the larger, occupying five-sixths, and the anterior the smaller, occupying one-sixth of the ball. The eye is made up of several membranes concentrically arranged, within which are enclosed the refracting media essential to vision. These mem- branes enumerated from without inwards, are : 1st, the sclerotic and cornea ; 2d, the choroid and iris; 3d, the retina; the refracting media are the aqueous humor, the crystalline lens and vitreous humor. The Sclerotic and Cornea. The sclerotic is the opaque fibrous mem- brane covering the posterior five-sixths of the ball. It is composed of con- nective tissue arranged in layers which run both transversely and longitudi- nally; it is pierced posteriorly by the optic nerve about one-tenth of an inch internal to the optic axis. The sclerotic by its density gives form to the eye and protects the delicate structures within it, and serves for the attachment of the muscles by which the ball is moved. The cornea is a transparent non-vascular membrane covering the anterior one-sixth of the eyeball. It is nearly circular in shape and is continuous at the circumference with the sclerotic, from which it cannot be separated. The substance of the cornea is made up of thin layers of delicate trans- parent fibrils of connective tissue more or less united together; between these layers are found a number of inter-communicating lymph spaces lined by endothelium, which are in connection with lymphatics. Leucocytes or lymph corpuscles are often found in these spaces. The anterior surface of the cornea is covered by several layers of nucleated epithelium which rest upon a structureless membrane known as the anterior elastic lamina. The posterior surface is covered by a similar membrane, the membrane of Decemet, which becomes continuous at its periphery with the iris; it is also covered by a layer of epithelial cells. At the junction of the cornea and sclerotic is found a circular groove, the canal of Schlemm. The Choroid, the Iris, the Ciliary Muscle and Ciliary processes, together constitute the second or middle coat of the eyeball. The choroid is a dark brown membrane which extends forward nearly 156 HUMAN PHYSIOLOGY. to the cornea, where it terminates in a series of folds, the ciliary processes. In its structure the choroid is highly vascular, consisting.of both arteries and veins. Externally it is connected with the sclerotic by connective tissue ; internally it is lined by a layer of hexagonal pigment cells which, though usually classed as belonging to the choroid, is now known to belong embryo- logically and physiologically to the retina. From without inward may be distinguished the following layers : — 1. The lamina supra-choroidea. 2. The elastic layer of Sattler, consisting of two endothelial layers. 3. The chorio-capilfaris, choroid proper, or membrane of Ruysch, a thick elastic network of arterioles and capillaries lying within the , outer layer of veins and arteries called the vena vorticosse. 4. The lamina vitrea or internal limiting membrane. The choroid with its contained blood vessels bears an important relation to the nutrition of the eye ; it provides for the blood supply, for drainage from the body of the eye, and presents an uniform and high temperature to the retina. The Iris is the circular variously-colored membrane placed in the an- terior portion of the eye just behind the cornea. It is perforated a little to the nasal side of the centre by a circular opening, the pupil. The outer or circumferential border is connected with the cornea, ciliary muscle and ciliary processes ; the free inner edge forms the boundary of the pupil, the size of which is constantly changing. The framework of the iris is com- posed of connective tissue, blood vessels, muscular fibres and pigmented connective-tissue corpuscles. The anterior surface is covered with a layer of epithelial cells continuous with those covering the posterior surface of the cornea; the posterior surface is lined by a limiting membrane bearing pigment epithelial cells continuous with those of the choroid. The various colors which the iris assumes in different individuals depend upon the quantity and disposition of the pigmentary granules. The muscular fibres of the iris, which are of the non-striated variety, are arranged in two sets, — the sphincter and dilator. The sphincter pupillce is a circular flat band of muscular fibres surround- ing the pupil close to its posterior surface ; by its contraction and relaxa- tion, the pupil is diminished or increased in size. The dilator pupilla consists of a thin layer of fibres arranged in a radiate manner ; at the mar- gin of the pupil they blend with those of the sphincter muscle, while at the outer border they arch to form a circular muscular layer. T\\z ciliary muscle is a gray circular band consisting of unstriped muscu- lar fibres about one-tenth of an inch long running from before backward. THE SENSE OF SIGHT. 157 It is attached anteriorly to the inner surface of the sclerotic and cornea, and posteriorly to the choroid coat opposite the ciliary processes. At the anterior border of the radiating fibres and internally are found bundles of circular muscular fibres, constituting the annular muscle of Miiller. The ciliary muscle thus consists of two sets of fibres, a radiating and circular, both of which are concerned in effecting a change in the convexity of the lens in the accommodation of the eye to near vision. The Retina forms the internal coat of the eye. In the fresh state it is a delicate transparent membrane of a pink color, but after death soon becomes FIG. 20. d - 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 Holden's Anatomy. opaque; it extends forward almost to the ciliary processes, where it termi- nates in an indented border, the ora serrata. In the posterior part of the retina at a point corresponding to the axis of vision is a yellow spot, the macula lutea, which is somewhat oval in shape and tinged with yellow pigment. It presents in its centre a depression, the fovea centralis, corres- ponding to a decrease in thickness of the retina ; about one-tenth of an inch to the inner side of the macula is the point of entrance of the optic nerve. The arleria centralis retince pierces the optic nerve near the sclerotic, runs forward in its substance and is distributed in the retina as far forward as the ciliary processes. 158 HUMAN PHYSIOLOGY. The retina is remarkably complex, consisting of ten distinct layers, from within outward, supported by connective tissue. These are as follows, viz.: i. Membrana limitans interna. 2. Fibres of optic nerve. 3. Layers of ganglionic corpuscles, 4. Molecular layer. 5. Internal granu- lar layer. 6. Molecular layer. 7. External granular layer. 8. Mem- brana limitans externa. 9. Jacobson's membrane or layer of rods and cones. 10. The layer of pigment cells. The most important of these, however, is the layer of rods and cones in the external portion of the retina. The rods are straight elongated cylinders extending through the entire thickness of Jacobson's membrane. They consist of an external portion which is clear, homogeneous and highly re- fracting, and of an internal portion which is slightly granular and less refractive; the outer end of each rod is in direct contact with the pig- mentary epithelium lining the choroid, while the inner end tapering to a fine thread, pierces the external limiting membrane and passes into the external granular layer. The cones consist also of two portions, the inner of which is somewhat thicker than the rod and rests upon the limiting membrane ; the outer portion tapers to a fine point which is known as the cone-style. The cones, as a rule, are somewhat shorter than the rods. The propor- tion of rods to cones varies in different parts of the retina, though there are on the average about fourteen rods to one cone. In the macula lutea, where vision is most acute, the rods are almost entirely absent, cones alone being present. All the retinal elements at this point are changed. The nerve fibre layer is absent, the axis cylinders radiating in such a manner as to leave the spot free from their covering. The remaining layers are all thinned and the stroma reduced to a minimum. The optic nerve after passing forward from the brain penetrates in succession the sclerotic, choroid, and retina ; the nerve fibres then spread out over the anterior surface of the retina and become connected with the large ganglionic cells, the third layer of the retina. 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, one hundred 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 pig- mentary layer. They, with the pigment layer, are the elements interme- diating the change of the ethereal vibrations into nerve force; out of these nerve vibrations the brain fashions the sensations of light, form and color. The vitreous humor, which supports the retina, is the largest of the re- fracting media; it is globular in form and constitutes about four-fifths of the ball ; it is hollowed out anteriorly for the reception of the crystalline lens. THE SENSE OF SIGHT. 159 The outer surface of the vitreous is covered by a delicate transparent mem- brane, termed the hyaloid membrane, which serves to maintain its globular form. The aqueous humor found in the anterior chamber of the eye is a clear alkaline fluid, having a specific gravity of 1.003-1.009. It is secreted most probably by the blood vessels of the iris and ciliary processes. It passes from the interior of the eye, through the canal of Schlemm and the meshes at the base of the iris, into the anterior circular vein. The crystalline lens enclosed within its capsule, is a transparent bi-con- vex body, situated just behind the iris and resting in the depression in the anterior part of the vitreous. The two convexities are not quite alike, the curvature of the posterior surface being slightly greater than that of the an- terior. The lens measures about one-third of an inch in the transverse diameter and one-fifth of an inch in the antero-posterior diameter. The suspensory ligament, by which the lens is held in position, is a firm transparent membrane, united to the ciliary processes. A short distance beyond its origin, it splits into two layers, the anterior of which is inserted into the capsule of the lens and blends with it ; the posterior passing inward behind the lens, becomes united to its capsule. The anterior layer pre- sents a series of foldings, Zone of Zinn, which are inserted into the intervals of the folds of the ciliary processes. The triangular space between the two layers is the canal of Petit. Blood vessels and Nerves. The structures composing the eyeball are supplied with blood by the long and short ciliary arteries, branches of the ophthalmic ; they pierce the sclerotic at various points and are ultimately distributed to all tissues within the ball. The nerve supply comes largely from the ophthalmic or ciliary ganglion. This is a small body, situated in the posterior part of the orbit; it receives motor fibres from a branch of the motor- oculi, or third nerve; a sensory branch from the ophthalmic division of the fifth nerve and fibres from the cavernous plexus of the sympathetic. From the anterior border of the ganglion proceed the ciliary nerves which, entering the eyeball, endow its structures with motion and sensation. The Eyeball a Living Camera Obscura. The eyeball may be com- pared in a general way to a camera obscura. The anatomical arrangement of its structures reveal many points of similarity. The sclerotic and choroid may be compared with the walls of the chamber; the combined refractive media, cornea, aqueous humor, lens, and vitreous humor, to the lens for focusing the rays of light ; the retina to the sensitive plate receiving the 160 HUMAN PHYSIOLOGY. image formed at the focal point ; the iris to the diaphragm, which by cutting off the marginal rays prevents spherical aberration and at the same time regulates the amount of light entering the eye; the ciliary muscle to the adjusting screw by which distinct images are thrown upon the retina in spite of varying distances of the object from which the light rays emanate. The structures just enumerated are those essential for normal vision. The relationship of the various structures composing the eyeball is shown by the following figure : — DIAGRAM OF A VERTICAL SECTION OF THE EYE. i. Anterior chamber filled with aqueous humor. 2. Posterior Chamber. 3. Canal o* 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. /. Ciliary muscle. — From Holden' s Anatomy. The Dioptric or Refracting apparatus by which the rays of light enter- ing the eye are so manipulated as to produce an image on the retina, consists of the cornea, aqueous humor, crystalline lens and vitreous humor. A ray of light in passing through each of these media will undergo refrac- tion at their surfaces and ultimately be brought to a focus at the retina. Inasmuch as the two surfaces of the cornea are parallel and its refractive power practically the same as the aqueous humor, the media may be re- duced to three, viz : I. Cornea and aqueous humor. 2. The lens. 3. The vitreous humor. The refracting surfaces may also be reduced to three, THE SENSE OF SIGHT. 161 viz : i. Anterior surface of the cornea. 2. Anterior surface of lens. 3. Posterior surface of lens. The refraction effected by the cornea is very great, owing to the passage of the light from the air into a comparatively dense medium, and is sufficient of itself to bring parallel rays of light to a focus about 10 millimetres behind the retina. This would be the condition in an eye in which the lens was congenitally absent. Perfect vision requires, however, that the convergence of the light shall be great enough that the image may fall upon the retina. This is accomplished by the crystalline lens, a body denser than the cornea and possessing a higher refractive power. The manner in which a biconvex lens focuses both parallel and divergent rays is shown in the following figures : — FIG. 22. DIAGRAM SHOWING THE COURSE OF PARALLEL RAYS OF LIGHT FROM A IN THEIR PASSAGE THROUGH A BICONVEX LENS L, IN WHICH THEY ARE SO REFRACTED AS TO BEND TOWARD AND COME TO A FOCUS AT A POINT F '.—From Yeo' s Text-Book of Physiology. FIG. 23. DIAGRAM SHOWING THE COURSE OF DIVERGING RAYS WHICH ARE BENT TO A POINT FURTHER FROM THE LENS THAN THE PARALLEL RAYS IN PRECEDING FIGURE. — From Yea's Text-Book of Physiology. The function of the crystalline lens, therefore, is to focus the rays of light with the formation of an image on the retina. The Retinal Image corresponds in all respects to the object from which the light proceeds. The existence of this image can be demonstrated by removing from the eye of a recently killed animal a circular portion of the sclerotic and choroid posteriorly and then placing at the proper distance in front of the cornea a lighted candle ; an inverted image of the candle will be 162 HUMAN PHYSIOLOGY. seen upon the retina. The size of the retinal image depends upon the visual angle, which in turn depends upon the size of the object and its distance from the eye. At a distance of 15.2596 metres the image of an object I metre high would be I millimetre, or a thousand times smaller than the object. Accommodation. By accommodation is understood the power which the eye possesses of adjusting itself to vision at different distances. In a normal or emmetropic eye parallel rays of light are brought to a focus on the retina ; but divergent rays, that is rays coming from a near luminous point, will be brought to a focus behind the retina, provided the refractive media remain the same ; as a result vision would be indistinct, from the formation of diffusion circles. It is impossible to see distinctly, therefore, a near and distant object at the same time. We must alternately direct the vision from one to the other. A normal eye does not require adjust- ing for parallel rays ; but for divergent rays a change in the eye is necessi- tated ; this is termed accommodation. In the accommodation for near vision the lens becomes more convex, particularly on its anterior surface ; the increase in convexity increases its refractive power ; the greater the degree of divergence of the rays previous to entering the eye, the greater the increase of convexity of the lens and convergence of the rays after passing through it. By this alteration in the shape of the lens we are enable to focus light rays coming from, and to see distinctly, near as well as distant objects. Function of the Ciliary Muscle. Though it is admitted that the change in the convexity of the lens is caused by the contraction of the ciliary muscle and the relaxation of the suspensory ligament, the exact manner in which it does so is not understood. When the eye is in repose as in distant vision, the suspensory ligament is tense and the lens possesses that degree of curvature necessary for focusing parallel rays. In the voluntary efforts to accommodate the eye for near vision, the ciliary muscle contracts, the suspensory ligament relaxes and the lens, inherently elastic, bulges for- ward and once again focuses the rays upon the retina. It is, therefore, termed the muscle of accommodation, and by its alternate contraction and relaxation the lens is rendered more or less convex, according to the requirements for near and distant vision. Range of accommodation. Parallel rays coming from a luminous point, distant not less than 200 feet, do not require adjustment : from this point up to infinity no accommodation is required for perfect vision. This is termed \\iepunctum remotum, and indicates the distance to which an object THE SENSE OF SIGHT. 163 may be removed and yet distinctly seen. If the object be brought nearer to the eye than 200 feet the accommodative power must come into play : the nearer the object the more energetic must be the contraction of the ciliary muscle and the consequent increase in the convexity of the lens. At a distance of five inches, however, the power of accommodation reaches its maximum : this is termed the punctum proximum, and indicates the nearest point at which an object may be seen distinctly. The distance between these two points is the range of accommodation. Optical Defects. Astigmatism is a condition of the eye which prevents vertical and horizontal lines from being focused at the same time, and is due to a greater curvature of the cornea in one meridian than another. Spherical aberration is a condition in which there is an indistinctness of an image from the unequal refraction of the rays of light passing through the circumference and the centre of the lens; it is corrected mainly by the iris, which cuts off the marginal rays, and only transmits those passing through the centre. Chromatic aberration is a condition in which the image is surrounded by a colored margin, from the decomposition of the rays of light into their elementary parts. Myopia, or short-sightedness, is caused by an abnormal increase in the antero-posterior diameter of the eyeball, or by a subnormal refracting power of the lens; it is generally due to the first cause; the lens being too far removed from the retina, forms the image in front of it, and the perception becomes dim and blurred. Concave glasses correct this defect, by prevent- ing the rays from converging too soon. Hyper met ropia, or long-sightedness, is caused by a shortening of the antero-posterior diameter, or by an excessive refractive power of the lens ; the focus of the rays of light would, therefore, be behind the retina. Con- vex glasses correct this defect, by converging the rays of light more anteri- orly. Presbyopia is a loss of the power of accommodation of the eye to near objects, and usually occurs between the ages of 40 and 60 ; it is remedied by the use of convex glasses. The Iris. The iris plays the part of a diaphragm, and by means of its central aperture the pupil regulates the quantity of light entering the interior of the eye ; by preventing rays from passing through the margin of the lens it diminishes spherical aberration. The size of the pupil depends upon the relative degree of contraction of the circular and radiating fibres ; 164 HUMAN PHYSIOLOGY. the variations in size of the pupil from variations in the degree of contrac- tion depend upon different intensities of light. If the light be intense the circular fibres contract and diminish the size of the pupil; if the light diminishes in intensity the circular fibres relax and the pupil enlarges. Point of most distinct Vision. While all portions of the retina are sensitive to light, their sensibility varies within wide limits. At the macula lutea and more especially in its most central depression, the fovea, where the retinal elements are reduced practically to the layer of rods and cones, the sensibility reaches its maximum. It is at this point that the image is found when vision is most distinct. The macula and fovea are always in the line of direct vision. From the macula towards the periphery of the retina there is a gradual diminution in sensibility and a corresponding decline in the distinctness of vision. In those portions of the retina lying outside the macula, the indistinctness of vision depends not only on diminished sensibility, but also upon inaccurate focusing of the rays. Blind Spot. Although the optic nerve transmits the impulses excited in the retina by the ethereal vibration, the nerve fibres themselves are insen- sitive to light. At the point of entrance of the optic nerve, owing to the absence of the rods and cones, the rays of light make no impression. This is the blind spot. As this spot is not in the line of vision, no dark point is ordinarily observed in the field of vision, that circular space before a fixed eye within which objects are perceptible. The rods and cones are the most sensitive portions of the retina. A ray of light entering the eye passes entirely through the various layers of the retina and is arrested only upon reaching the pigmentary epithelium in which the rods and cones are imbedded. As to the manner in which the objective stimuli, light and color so-called, are transformed into nerve im- pulses, but little is known. It is probable that the ethereal vibrations are transformed into heat, which excites the rods and cones. These acting as highly specialized end organs of the optic nerve, start the impulses on their way to the brain where the seeing process takes place. As to the relative function of the rods and cones, it has been suggested, from the study of the facts of comparative anatomy, that the rods are impressed only by differences in the intensity of light, while the cones in addition are im- pressed by qualitative differences or color. Accessory Structures. The muscles which move the eyeball are six in number; the superior and inferior recti, the external and internal recti, the superior and inferior oblique muscles. The four recti muscles, arising from the apex of the orbit, pass forward and are inserted into the sides of THE SENSE OF HEARING. 165 the sclerotic coat ; the superior and inferior muscles rotate the eye around a horizontal axis ; the external and internal rotate it around a vertical axis. The Superior oblique muscle, having the same origin, passes forward to the inner and upper angle of the orbital cavity, where its tendon passes through a cartilaginous pulley; it is then reflected backward and inserted into the sclerotic just behind the transverse diameter. Its function is to rotate the eyeball in such a manner as to direct the pupil downward and outward. The Inferior oblique muscle arises at the inner angle of the orbit and then passes outward and backward, to be inserted into the sclerotic. Its function is to rotate the eyeball and direct the pupil upward and outward. By the associated action of all these muscles, the eyeball is capable of performing all the varied and complex movements necessary for distinct vision. The Eyelids, bordered with short, stiff hairs, shade the eye and protect it from injury. On the posterior surface, just beneath the conjunctiva, are the Meibomian glands, which secrete an oily fluid ; it covers the edge of the lids, and prevents the tears from flowing over the cheek. The Lachrymal Glands are ovoid in shape, and situated at the upper and outer part of the orbital cavity ; they open by from six to eight ducts at the outer portion of the upper lids. The Tears, secreted by the lachrymal glands, are distributed over the cornea by the lids during the act of winking, and keep it moist and free from dust. The excess of tears passes into the lachrymal ducts, which begin by two minute orifices, one on each lid, at the inner canthus. They conduct the tears into the nasal duct, and so into the nose. THE SENSE OF HEARING. The Ear or Organ of Hearing is lodged within the petrous portion of the temporal bone. It may be, for convenience of description, divided into three portions, viz : I. The external ear. 2. The middle ear. 3. The internal ear or labyrinth. The External Ear consists of the pinna or auricle and the external au- ditory canal. The pinna consists of a thin layer of cartilage, presenting a series of elevations and depressions ; it is attached by fibrous tissue to the outer bony edge of the auditory canal ; it is covered by a layer of integu- ment continuous with that covering the side of the head. The general 166 HUMAN PHYSIOLOGY. shape of the pinna is concave and presents a little below the centre a deep depression, the concha. The external auditory canal extends from the concha inward for a distance of about one and a quarter inches. It is directed somewhat forward and upward, passing over a convexity of bone, and then dips downward to its termination ; it is composed of both bone and cartilage and lined by a reflection of the skin covering the pinna. At the external portion of the canal the skin contains a number of tubular glands, the ceruminous glands, which in their conformation resemble the perspiratory glands. They secrete the cerumen or ear wax. The Middle Ear or Tympanum is an irregularly shaped cavity hollowed out of the temporal bone and situated between the external ear and the labyrinth. It is narrow from side to side but relatively long in its vertical and antero- posterior diameters; it is separated from the external auditory canal by a membrane, the membrana tympani ; from the internal ear it is separated by an osseo-membranous partition which forms a common wall for both cavities. The middle ear communicates posteriorly with the mastoid cells, anteriorly with the naso-pharynx by means of the Eustachian tube. The interior of this cavity is lined by mucous membrane continuous with that lining the pharynx. The membrana tympani is a thin, translucent, nearly circular membrane, measuring about two-fifths of an inch in diameter, placed at the inner ter- mination of the external auditory canal. The membrane is enclosed within a ring of bone which, in the foetal condition, can be easily removed, but in the adult condition becomes consolidated with the surrounding bone. The membrana tympani consists primarily of a layer of fibrous tissue, arranged both circularly and radially, and forms the membrana propria ; externally, it is covered by a thin layer of skin continuous with that lining the auditory canal ; internally, it is covered by a thin mucous membrane. The tympanic membrane is placed obliquely at the bottom of the auditory canal, inclining at an angle of 45°, being directed from behind and above downward and inward. On its external surface this membrane presents a funnel-shaped depression, the sides of which are somewhat convex. The Ear-bones. Running across the tympanic cavity and forming an irregular line of jointed levers, is a chain of bones which articulate with each other at their extremities. They are known as the malleus, incus and stapes. The form and position of these bones are shown in Fig. 24. The malleus consists of a head, neck and handle, of which the latter is attached to the inner surface of the membrana tympani ; the incus, or anvil THE SENSE OF HEARING. 167 bone presents a concave, articular surface, which receives the head of the malleus; the stapes, or stirrup bone, articulates externally with the long pro- cess of the incus, and internally, by its oval base, with the edges of the fora- men ovale. The tensor tympani muscle consists of a fleshy, tapering portion, half an inch in length, which terminates in a slender tendon ; it arises from the 11 TYMPANUM AND AUDITORY OSSICLES (LEFT) MAGNIFIED. A.G., external meatus ; M, membrana tympani, which is attached to the handle of the malleus, n, and near it the short process, /; h, head of the malleus; a, incus ; k, its short process with its ligament ; /, long process ; s, Sylvian ossicle ; S, stapes ; A.X, A-r, is the axis of rotation of the ossicles ; it is shown in perspective, and must be imagined to penetrate the plane of the paper ; t, line of traction of the tensor tympani. The other arrows indicate the movement of the ossicles when the tensor contracts. cartilaginous portion of the Eustachian tube and adjacent surface of the sphenoid bone. From this origin the muscle passes nearly horizontally backward to the tympanic cavity ; just opposite to the fenestra ovalis its tendon bends at a right angle over the processus cochleariformis and then passes outward across the cavity to be inserted into the handle of the mal- leus near the neck. 168 HUMAN PHYSIOLOGY. The stapedius muscle emerges from the cavity of a pyramid of bone projecting from the posterior wall of the tympanum; the tendon passes forward and is inserted into the neck of the stapes bone posteriorly near its point of articulation with the incus. The laxator tympani muscle, so-called, is now generally regarded as liga- mentous in nature, and not muscular. The Eustachian tube, by means of which a free communication is established between the middle ear and pharynx, is partly bony and partly cartilaginous in structure. It measures about an inch and a half in length ; commencing at its opening into the naso-pharynx it passes upward and out- ward to the spine of the sphenoid bone, at which point it becomes some- what contracted ; the tube then dilates as it passes backward into the middle ear cavity ; it is lined by mucous membrane, which is continued into the middle ear and mastoid cells. The Function of the Ear, as a whole, is the reception and transmis- sion of aerial vibrations to the terminal organs concealed within the in- ternal ear and which are connected with the auditory nerve fibres. The excitation of these end organs caused by the impact of the vibrations, arouses in the auditory nerve impulses which are then transmitted to the brain, where the hearing process takes place. In order to appreciate the functions of the individual parts of the ear a few of the characteristics of sound waves must be kept in mind. Sound Waves. All sounds are caused by vibrations in the atmosphere which have been communicated to it by vibrating elastic bodies, such as membranes, strings, rods, etc. These vibrating bodies produce in the air a to and fro movement of its particles, resulting in a series of alternate condensations and rarefactions which are propagated in all directions. A complete oscillation of a particle of air forward and backward constitutes a sound-wave. Musical sounds are caused by a succession of regular waves which follow each other with a certain rapidity. Noises are caused by the impact of a series of irregular waves. All sound waves possess intensity, pitch, and quality. The intensity, or loudness, of a sound depends upon the amplitude of the vibration, or the extent of its excursion. The//&v£ depends upon the number of vibrations which affect the auditory nerve in a second of time ; the pitch of the note C, the first below the leger line of the musical scale, is caused by 256 vibrations per second ; the pitch of the same note an octave higher is caused by 512 vibrations per second. If the vibrations are too few per second they fail to be perceived as a continuous sound ; the minimum THE SENSE OF HEARING. 109 number of vibrations capable of producing a sound has been fixed at 1 6 per second ; the highest pitched musical note capable of being heard has been shown to be due to 38,000 vibrations per second. In the ascent of the musical scale there is, therefore, a gradual increase in the number of vibra- tions and a gradual increase in the pitch of the sounds. Between the two extreme limits lies the range of audibility, which embraces eleven octaves, of which seven are employed in the musical scale. The quality of sound depends upon a combination of the fundamental vibration with certain secondary vibrations of sub divisions of the vibrating body. These so-called over-tones vary in intensity and pitch, and by modifying the form of the primary wave produce that which is termed the quality of sound. Function of the Pinna and External Auditory Canal. In those animals possessing movable ears, the pinna plays an important part in the collection of sound-waves. In man, in whom the capability of moving the pinna has been lost, it is doubtful if it is at all necessary for hearing. Never- theless an individual with dull hearing may have the perception of sound increased by placing the pinna at an angle of 45° to the side of the head. The external auditory canal transmits the sonorous vibrations to the tym- panic membrane. Owing to the obliquity of this canal it has been sup- posed that the waves, concentrated at the concha, undergo a series of re- flections on their way to the tympanic membrane, and, owing to the position of this membrane, strike it almost perpendicularly. Function of the Tympanic Membrane. The function of the tym- panic membrane appears to be the reception of sound vibrations by being thrown by them into reciprocal vibrations which correspond in intensity and amplitude. That this membrane actually reproduces all vibrations within the range of audibility has been experimentally demonstrated. The mem- brane not being fixed, as far as its tension is concerned, does not possess a fixed fundamental note, like a stationary fixed membrane, and is therefore just as well adapted for the reception of one set of vibrations as another. This is made possible by variations in its tension in accordance with the pitch of the sounds. In the absence of all sound the membrane is in a condition of relaxation ; with the advent of sound-waves possessing a gradual increase of pitch, as in the ascent of the musical scale, the tension of the tympanic membrane is gradually increased until its maximum ten- sion is reached at the upper limit of the range of audibility. By this change in tension certain tones become perceptible and distinct, while others become indistinct and inaudible. L 170 HUMAN PHYSIOLOGY. Function of the Tensor Tympani Muscle. The function of this muscle is, as its name indicates, to increase the tension of the membrane in accordance with the pitch of the sound wave. The tendon of this muscle playing over the processus cochleariformis and attached at almost a right angle to the handle of the malleus, will, when the muscle contracts, pull the handle inwards, increase the convexity of the membrane, and at the same time increase its tension ; with the relaxation of this muscle, the handle of the malleus passes outward and the tension is diminished. The contractions of the tensor muscle are reflex in character and excited by nerve impulses reaching it through the small petrosal nerve and otic ganglion. The number of nerve stimuli passing to the muscle and determining the degree of con- traction will depend upon the pitch of the Sound wave and the subsequent excitation of the auditory nerve. The tensor tympani muscle may be re- garded as an accommodative apparatus by which the tympanic membrane is adjusted to enable it to receive vibrations of varying degrees of pitch. Function of the Ossicles. The function of the chain of bones is to transmit the sound waves across the tympanic cavity to the internal ear. The first of these bones, the malleus, being attached to the tympanic mem- brane will take up the vibrations much more readily than if no membrane intervened. Owing to the character of the articulations, when the handle of the malleus is drawn inward, the position of the bones is so changed that they form practically a solid rod, and are therefore much better adapted for the transmission of molecular vibrations than if the articulations remained loose. As the stapes bone is somewhat shorter than the malleus, its vibrations are smaller than those of the tympanic membrane, and by this arrangement the amplitude of the vibrations is diminished but their force increased. The Function of the Stapedius Muscle is, according to Henle, to fix the stapes bone so as to prevent too great a movement from being com- municated to it from the incus and transmitted to the perilymph. It may be looked upon therefore, as a protective muscle. The Function of the Eustachian tube is to maintain a free communi- cation between the cavity of the middle ear and naso-pharynx. The pressure of air within and without the ear is thus equalized, and the vibra- tions of the tympanic membrane permitted to attain their maximum ; one of the conditions essential for the reception of sound waves. The impair- ment in the acuteness of hearing which is caused by an unequal pressure of the air in the middle ear can be shown : I. By closing the mouth and nose and forcing air from the lungs through the Eustachian tube into the ear, producing an increase in pressure. 2. By closing the nose and mouth, and THE SENSE OF HEARING. 171 making efforts at deglutition, which withdraws the air from the ear and diminishes its pressure. In both instances the free vibrations of the tympanic membrane are .interfered with. The pharyngeal orifice of the Eustachian tube is opened by the action of certain of the muscles of deglutition, viz : the levator palati, tensor palati, and the palato-pharyngei muscles. The Internal Ear, or Labyrinth, is located in the petrous portion of the temporal bone, and consists of an osseous and membranous portion. The Osseous Labyrinth is divisible into three parts, viz : the vesti- bule, the semicircular canals and the cochlea. The vestibule is a small, triangular cavity, which communicates with the middle ear by the foramen ovale; in the natural condition it is closed by the base of the stapes bone. The filaments of the auditory nerve enter the vestibule through small foramina in the inner wall, at the fovea hemi- spherica. The Semicircular canals are three in number ; the superior vertical, the inferior vertical and the horizontal, each of which opens into the cavity of the vestibule by two openings, with the exception of the two vertical, which at one extremity open by a common orifice. The Cochlea forms the anterior part of the internal ear. It is a gradually tapering canal, about one and a half inches in length, which winds spirally around a central axis, the modiolus, two and a half times. The interior of the cochlea is partly divided into two passages by a thin plate of bone, the lamina osseous spiralis, which projects from the central axis two-thirds across the canal. These passages are termed the scala vestibuli and the scala tympani, from their communication with the vestibule and tympanum. The scala tympani communicates with the middle ear through fat foramen rotundum, which, in the natural condition, is closed by the second mem- brana tympani ; superiorly they are united by an opening, the helicotrema. The whole anterior of the labyrinth, the vestibule, the semicircular canals, and the scala of the cochlea, contains a clear, limpid fluid, the peri- lymph, secreted by the periosteum lining the osseous walls. The Membranous Labyrinth corresponds to the osseous labyrinth with respect to form, though somewhat smaller in size. The Vestibular portion consists of two small sacs, the titricle and saccule. The Semicircular canals communicate with the utricle in the same manner as the bony canals communicate with the vestibule. The saccule communicates with the membranous cochlea by the canalis reuniens. In the interior of the utricle and saccule, at the entrance of the auditory nerve, 172 HUMAN PHYSIOLOGY. are small masses of carbonate of lime crystals, constituting the otoliths. Their function is unknown. The Membranous cochlea is a closed tube, commencing by a blind extremity at the first turn of the cochlea, and terminating at its apex by a blind extremity also. It is situated between the edge of the osseous lamina spiralis and the outer wall of the bony cochlea, and follows it in its turns around the modiolus. A transverse section of the cochlea shows that it is divided into two portions by the osseous lamina and the basilar membrane: I. The scala vestibuli, bounded by the periosteum and membrane of Reissner. 2. The scala tympani, occupying the inferior portion, and bounded above by the septum, composed of the osseous lamina and the membrana basilaris. The true membranous canal is situated between the membrane of Reiss- ner and the basilar membrane. It is triangular in shape, but is partly divided into a triangular portion and a quadrilateral portion by the tectorial membrane. The Organ of Corti is situated in the quadrilateral portion of the canal, and consists of pillars of rods, of the consistence of cartilage. They are arranged in two rows ; the one internal, the other external ; these rods rest upon the basilar membrane; their bases are separated from each other, but their upper extremities are united, forming an arcade. In the internal row it is estimated there are about 3500, and in the external row about 5200 of these rods. On the inner side of the internal row is a single layer of elongated hair cells ; on the outer surface of the external row are three such layers of hair cells. Nothing definite is known as to their function. The Endolymph occupies the interior of the utricle, saccule, membranous canals, and bathes the strictures in the interior of the membranous cochlea, throughout its entire extent. The Auditory Nerve at the bottom of the internal auditory meatus divides into (l) a vestibular branch, which is distributed to the utricle and semicircular canals ; (2) a cochlear branch, which passes into the central axis at its base, and ascends to its apex ; as it ascends, fibres are given off, which pass between the plates of the osseous lamina, to be ultimately con- nected with the organ of Corti. The Function of the semicircular canals appears to be to assist in main- taining the equilibrium of the body ; destruction of the vertical canal is followed by an oscillation of the head upward and downward ; destruction of the horizontal canal is followed by oscillations from left to right. When VOICE AND SPEECH. 173 the canals are injured on both sides, the animal loses the power of main- taining equilibrium upon making muscular movements. Function of the Cochlea. It is regarded as possessing the power of appreciating the quality of pitch and the shades of different musical tones. The elements of the organ of Corti are analogous, in some respects, to a musical instrument, and are supposed, by Helmholtz, to be tuned so as to vibrate in unison with the different tones conveyed to the internal ear. Summary. The waves of sound are gathered together by the pinna and external auditory meatus, and conveyed to the membrana tympani. This membrane, made tense or lax by the action of the tensor tympani and laxator tympani muscles, is enabled to receive sound waves of either a high or low pitch. The vibrations are conducted across the middle ear by a chain of bones to the foramen ovale, and by the column of air of the tympanum to the foramen rotundum, which is closed by the second membrana tympani; the pressure of the air in the tympanum being regu- lated by the Eustachian tube. The internal ear finally receives the vibrations, which excite vibrations successively in the perilymph, the walls of the membranous labyrinth, the endolymph, and, lastly, the terminal filaments of the auditory nerve, by which they are conveyed to the brain. VOICE AND SPEECH. The Larynx is the organ of voice. Speech is a modification of voice, and is produced by the teeth and the muscles of the lips and tongue, co- ordinated in their action by stimuli derived from the cerebrum. The Structures entering into the formation of the larynx are mainly the thyroid, cricoid and arytenoid cartilages ; they are so situated and united by means of ligaments and muscles as to form a firm cartilaginous box. The larynx is covered externally by fibrous tissue, and lined inter- nally with mucous membrane. The Vocal Cords are four ligamentous bands, running antero-posteri- orly across the upper portion of the larynx, and are divided into the two superior or false vocal cords, and the two inferior or true vocal cords ; they are attached anteriorly to the receding angle of the thyroid cartilages and posteriorly to the anterior part of the base of the arytenoid cartilages. The space between the true vocal cords is the rinia glottidis. The Muscles which have a direct action upon the movements of the 174 HUMAN PHYSIOLOGY. vocal cords are nine in number, and take their names from their points of origin and insertion, viz : the two crico-thyroid, two thyro-arytenoid, two posterior crico-arytenoid, two lateral crico-arytenoid, and one arytenoid muscles. The crico-thyroid muscles, by their contraction, render the vocal cords more tense by drawing down the anterior portion of the thyroid cartilage and approximating it to the cricoid, and at the same time tilting the pos- terior portion of the cricoid and arytenoid cartilages backward. The thyro-arytenoid, by their contraction, relax the vocal cords by draw- ing the arytenoid cartilage forward and the thyroid backward. The posterior crico-arytenoid muscles, by their contraction, rotate the arytenoid cartilages outward and thus separate the vocal cords and enlarge the aperture of the glottis. They principally aid the respiratory movements during inspiration. The lateral crico-arytenoid muscles are antagonistic to the former, and by their contraction rotate the arytenoid cartilages so as to approximate the vocal cords and constrict the glottis. The arytenoid muscle assists in the closure of the aperture of the glottis. The inferior laryngeal nerve animates all the muscles of the larynx, with the exception of the crico thyroid. Movements of the Vocal Cords. During respiration the move- ments of the vocal cords differ from those occurring during the production of voice. At each inspiration, the true vocal cords are widely separated, and the aperture of the glottis is enlarged by the action of the crico-arytenoid muscles, which rotate outward the anterior angle of the base of the aryte- noid cartilages; at each expiration the larynx becomes passive; the elasticity of the vocal cords returns them to their original position, and the air is forced out by the elasticity of the lungs and the walls of the thorax. Phonation. As soon as phonation is about to be accomplished a marked change in the glottis is noticed with the aid of the laryngoscope. The true vocal cords suddenly become approximated and are made parallel, giving to the glottis the appearance of a narrow slit, the edges of which are capable of vibrating accurately and rapidly; at the same time their tension is much increased. With the vocal cords thus prepared, the expiratory muscles force the column of air into the lungs and trachea through the glottis, throwing the edges of the cords into vibration. The //A:/; of sounds depends upon the extent to which the vocal cords are made tense and the length of the aperture through which the air passes. VOICE AND SPEECH. 175 In the production of sounds of a high pitch the tension of the vocal cords becomes very marked, and the glottis diminished in length. When grave sounds, having a low pitch, are omitted from the larynx, the vocal cords are less tense and their vibrations are large and loose. The quality of voice depends upon the length, size and thickness of the cords, and the size, form and construction of the trachea, larynx and the resonant cavities of the pharynx, nose and mouth. The compass of the voice comprehends from two to three octaves. The range is different in the two sexes ; the lowest note of the male being about one octave lower than the lowest note of the female : while the highest note of the male is an octave less than the highest note of the female. The varieties of voices, e.g., bass, baritone, tenor, contralto, mezzo- soprano and soprano, are due to the length of the vocal cords ; being longer when the voice has a low pitch, and shorter when it has a high pitch. Speech is the faculty of expressing ideas by means of combinations of sounds, in obedience to the dictates of the cerebrum. Articulate sozinds may be divided into vcnvels and consonants. The vowel sounds, a, e, i, o, u, are produced in the larynx by the vocal cords. The consonantal sounds are produced in the air passages above the larynx by an interruption of the current of air by the lips, tongue and teeth ; the consonants may be divided into: (i) mutes, b, d, /£,/, t, c,g; (2) dentals, blood Reflex movements of spinal cord . action, laws of Reproduction Respiration movements of nervous mechanism of ... types of nervous circle of ...... Retina . . PAGE ii 17 27 57 119 47 123 124 176 59 62 63 63 130 eALIVA ^ Sebaceous glands Secretion Semi-circular canals Semen Sight, sense of Skin .. relative sensibility of .... Smell, sense of Sounds of heart Spermatozoa Spheno-palatine ganglion Spinal accessory nerve Spinal cord membranes of structure of white matter . . . — — — structure of gray matter . . . properties of function of as a conductor . . as an independent centre . . decussation of motor and sen- sory fibres reflex action of • special centres of paralysis, from injuries of . . nerves, origin of course of anterior and posterior roots of Spleen Starvation, phenomena of Stomach • Structural composition of the body . Submaxillary ganglion Sugar, uses of in the body Supra-renal capsules Sudoriparous glands Sympathetic nervous system .... properties and functions of . . 27 |9 69 171 180 154 116 117 118 121 122 122 II9 I23 125 126 I19 II9 74 20 29 H8? 13 75 90 147- 149 198 INDEX. I 'JVA.STE, SENSE OF AGE 152 153 25 170 179 41 62 18 152 153 '53 151 119 183 81 82 80 80 81 Urination, nervous mechanism of . Uterus VAPOR, WATERY, OF v breath . . PAGE • 79 • "7 66 Teeth Tensor tympani muscle Testicles Thoracic duct Thorax, enlargement of in inspiration Tissues, classification of Vascular glands 74 188 . 129 • 58 . 179 132 146 64 174 173 12 1 88 Tongue . . Vaso-motor nerves, origin of . Veins Touch, sense of Tiirck, column of UMBILICAL CORD . Urea Uric acid Urine Vesiculae seminales Vision, physical centre for .... Vital capacity of lungs Vocal cords . . Voice WATER, AMOUNT OF IN body Wolffian bodies ents secreted daily REDUCED FAC-SIMILE I A N F\V OF TITLE PAGE. j MEDICAL DICTIONARY INCLUDING ALL THE WORDS AND PHRASES GENERALLY USED IN MEDICINE, WITH THEIR PROPER PRO- NUNCIATION AND DEFINITIONS. BASED ON RECENT MEDICAL, LITERATURE. GEORGE M. GOULD, B.A., M.D., OPHTHALMIC SURGEON TO THE PHILADELPHIA HOSPITAL AND CLINICAL CHIEF OFHTHALMOLOCICAL DEPARTMENT, GERMAN HOSPITAL, WITH ELABORATE TABLES OP THB BACILLI, MICROCOCCI, LEUCOMA'l'NES, PTOMAINES, ETC.; OP THE ARTERIES, GANGLIA, MUSCLES, NERVES AND PLEXUSES; OP WEIGHTS AND MEASURES, THERMOMETERS, ETC.; AND APPENDICES CONTAINING CLASSIFIED TABLES WITH ANALYSES, OF THE WATERS OP THE MINERAL SPRINGS OP THB V. S., AND TABUS OF VITAL STATISTICS. PHILADELPHIA: P. BLAKISTON, SON fc CO. 1012 WALNUT STREET. Full Page reduced about one-half. Declared THE STANDARD by the Journal of the American Medical Association. " So far as a careful examination enables us to judge, it faithfully represents the standard medical literature of to-day." Octavo, Half Morocco, as above, with Thumb Index, $4.25 Plain Dark Leather, without Thumb Index, .... 3.25 A prospectus containing descriptions and full-size sample pages will be mailed to any address upon application. P. 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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. ISO Illus. NEW EDITION. The Diseases of Women. Including Diseases of the Bladder and Urethra. By DR. F. WINCKEL, Professor of Gynaecology and Director of the Royal University Clinic for Women, in Munich. Second Edition. Re- vised and Edited by Theophilus Parvin, M.D., Professor of Obstetrics and Diseases of Women and Children in Jefferson Medical College. 150 Engrav- ings, most of which are original. " 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 Surgical 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. PHYSIOLOGY. Fifth 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. Fifth American from last 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. "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. Lewis A. Stimson, M.D.. 37 East 33d Street, New York. Price of each Book, Cloth, $3.00; Leather, $3.50. THE NEW SERIES OF MANUALS. No. 5. DISEASES OF CHILDREN. SECOND EDITION. A Manual. By J. F. GOODHART, M.D., Phys. to the Evelina Hospital for Children; Asst. Phys. to Guy's Hospital, London. Second American Edition. Edited and Rearranged 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 Hos- pital, Phila. Containing many new Prescriptions, a list of over 50 Formulae, conforming to the U. S. Pharma- copoeia, and Directions for making Artificial Human Milk, for the Artificial Digestion of Milk, etc. Illus. " The merits of the book are many. Aside from the praiseworthy •work of the printer and binder, which gives us a print and page that delights the eye, there is the added charm of a style of writ- ing that is not wearisome, that makes its statements clearly and forcibly, and that knows when to stop when it has said enough. The insertion of typical temperature charts certainly enhances the value of the book. It is rare, too, to find in any text-book so many topics treated of. All the rarer and out-of-the-way diseases are given consideration. This we commend. It makes the work valuable." — Archives of Pedriatics , July , i8qo. " The author has avoided the not uncommon error of writing a. book on general medicine and labeling it ' Diseases of Children,' but has steadily kept in view the diseases which seemed to be incidental to childhood, or such points in disease as appear to be so peculiar to or pronounced in children as to justify insistence upon them. * * * A safe and reliable guide, and in many ways admirably adapted to the wants of the student and practitioner." — American Journal of Medical Science. " Thoroughly individual, original and earnest, the work evi- dently of a close observer and an independent thinker, this book, though small, as a handbook or compendium is by no means made up of bare outlines or standard facts." — The Therapeutic Ga- zette. "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 (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. Price of each Book, Cloth, $3.00 : Leather, $3.50. THE NEW SERIES OF MANUALS. No. 6. 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. " Dr. Waring's Therapeutics has long been known as one of the most thorough and valuable of medical works. The amount of actual intellectual labor it represents is immense. . . . An in- dex of diseases, with the remedies appropriate for their treatment, closes the volume." — Boston Medical and Surgical Reporter. " The plan of this work is an admirable one, and one well calcu- lated to meet the wants of busy practitioners. There is a remark- able amount of information, accompanied with judicious comments, imparted in a concise yet agreeable style." — Medical Record. No. 7. MEDICAL JURISPRUDENCE AND TOXICOLOGY. THIRD REVISED EDITION. 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. ; Third Edition, Revised and Enlarged. " This admirable text-book." — Amer.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. " The book before us will, we think, be found to answer the ex- pectations of the student or practitioner seeking a manual of juris- prudence, and the call for a second edition is a flattering testimony to the value of the author's present effort. The medical portion of this volume seems to be uniformly excellent, leaving little for adverse criticism. The information on the subject matter treated has been carefully compiled, in accordance with recent knowledge. The lexicological portion appears specially excellent. Of that por- tion of the work treating of the legal relations of the practitioner and medical witness, we can express a generally favorable ver- dict."— Physician and Surgeon, Ann Arbor, Mich. Price of each Book, Cloth. $3,00; Leather, $3.50. 6 STUDENTS' TEXT-BOOKS AND MANUALS. ANATOMY. Macalister's Human Anatomy. 816 Illustrations. A new Text-book for Students and Practitioners, Systematic and Topo- graphical, including the Embryology, Histology and Morphology of Man. With special reference to the requirements of Practical Surgery and Medicine. With 816 Illustrations, 400 of which are original. Octavo. Cloth, 7.50; Leather, 8.50 Ballou's Veterinary Anatomy and Physiology. Illustrated. By Wm. R. Ballou, M.U., Professor of Equine Anatomy at New York College of Veterinary Surgeons. 29 graphic Illustrations. i2ino. Cloth, i. oo; Interleaved for notes, 1.25 Holden's Anatomy. A manual of Dissection of the Human Body. Fifth Edition. Enlarged, with Marginal References and over 200 Illustrations. Octavo. 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." — Ne-w 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. Clo., 1.25 Heath's Practical Anatomy. Sixth London Edition. 24 Col- ored Plates, and nearly 300 other Illustrations. Cloth, 5.00 Potter's Compe'nd of Anatomy. Fifth Edition. Enlarged. 16 Lithographic Plates. 117 Illustrations. Cloth, i.oo; Interleaved for Notes, 1.25 CHEMISTRY. Hartley's Medical Chemistry. Second Edition. A text-book prepared specially for Medical, Pharmaceutical and Dental Stu- dents. With 50 Illustrations, Plate of Absorption Spectra and Glossary of Chemical Terms. Revised and Enlarged. Cloth, 2. 50 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. Third Edition. 8vo. Cloth, 1.50 4EJ- See pages 2 to 5 for list of Students' Manuals. STUDENTS' TEXT-BOOKS AND MANUALS. 7 Chemistry : — Continued. Bloxam's Chemistry, Inorganic and Organic, with Experiments. Seventh Edition. Enlarged and Rewritten. 281 Illustrations. 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 Plate of Spectra. Cloth, 2.00 Richter's Organic Chemistry, or Chemistry of the Carbon Compounds. Illustrated. Second Edition. In Press. Symonds. Manual of Chemistry, for the special use of Medi- cal Students. By BKANDRETH SYMONDS, A.M., M.D., Asst. Physician Roosevelt Hospital, Out- Patient Department; Attend- ing Physician Northwestern Dispensary, New York. i2mo. Cloth, 2.00; Interleaved for Notes, 2.40 Leffmann's Compend of Chemistry. Inorganic and Organic. Including Urinary Analysis. Third Edition. Revised. Cloth, i.oo; Interleaved for Notes, 1.25 Leffmann and Beam. Progressive Exercises in Practical Chemistry. i2mo. Illustrated. Cloth, i.oo Muter. Practical and Analytical Chemistry. Third Edi- tion. Revised and Illustrated. Nearly Ready. Holland. The Urine, Common Poisons, and Milk Analysis, Chemical and Microscopical. For Laboratory Use. Fourth Edition, Enlarged. Illustrated. Cloth, i.oo Van Niiys. Urine Analysis. Illus. Cloth, 2.00 Wolff's Applied Medical Chemistry. By Lawrence Wolff, M.D., Dem. of Chemistry in Jefferson Medical College. Clo., i.oo CHILDREN. Goodhart and Starr. The Diseases of Children. Second Edition. By J. F. Goodhart, M.D., Physician to the Evelina Hospital for Children; Assistant Physician to Guy's Hospital, London. Revised and Edited by Louis Starr, M.D., Clinical Professor of Diseases of Children in the Hospital of the Univer- sity of Pennsylvania; Physician to the Children's Hospital, Philadelphia. Containing many Prescriptions and Formulae, conforming to the U. S. Pharmacopoeia, Directions for making Artificial Human Milk, for the Artificial Digestion of Milk, etc. Illustrated. Cloth, 3.00; Leather, 3.50 Hatfield. Diseases of Children. By M. P. Hatfield, M.D., Professor of Diseases of Children, Chicago Medical College. Colored Plate. i2mo. Cloth, i.oo; Interleaved, 1.25 4^" See pages 14 and IJ for list of f Quiz- Compends f 8 STUDENTS' TEXT-BOOKS AND MANUALS. Children:— Continued. Starr. Diseases of the Digestive Organs in Infancy and Childhood. With chapters on the Investigation of Disease, and on the General Management of Children." By Louis Starr, M.D., Clinical Professor of Diseases of Children in the Univer- sity of Pennsylvania. Illus. Second Edition. Cloth, 2.25 DENTISTRY. Fillebrown. Operative Dentistry. 330 Illus. Cloth, 2.50 Flagg's Plastics and Plastic Filling. 4th Ed. Cloth, 4.00 Gorgas. Dental Medicine. A Manual of Materia Medica and Therapeutics. Third Edition. Cloth, 3.50 Harris. Principles and Practice of Dentistry. Including Anatomy, Physiology, Pathology, Therapeutics, Dental Surgery and Mechanism. Twelfth Edition. Revised and enlarged by Professor Gorgas. 1028 Illustrations. Cloth, 7.00 ; Leather, 8.00 Richardson's Mechanical Dentistry. Fifth Edition. 569 Illustrations. 8vo. Cloth, 4.50; Leather, 5.50 Sewill. Dental Surgery. 200 Illustrations. 3d Ed. Clo., 3.00 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. Second Edition. Cloth, 3.00 Tomes' Dental Anatomy. Third Ed. 191 Illus. Cloth, 4.00 Tomes' Dental Surgery. 3d Edition. Revised. 292 Illus. 772 Pages. Cloth, 5.00 Warren. Compend of Dental Pathology and Dental Medi- cine. Illustrated. Cloth, i.oo; Interleaved, 1.25 DICTIONARIES. Gould's New Medical Dictionary. Containing the Definition and Pronunciation of all words in Medicine, with many useful Tables etc. % Dark Leather, 3.25; yz Mor., Thumb Index 4.25 Harris' Dictionary of Dentistry. Fifth Edition. Completely revised and brought up to date by Prof. Gorgas. Cloth, 5.00; Leather, 6.00 Cleaveland's Pronouncing Pocket Medical Lexicon, sist Edition. Giving correct Pronunciation and Definition. 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 j9®=- See pages 2 to 5 for list of Students' Manuals, STUDENTS' TEXT-BOOKS AND MANUALS. 9 EYE. Hartridge on Refraction. 4th Ed. Cloth, 2.00 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 Swanzy. Diseases of the Eye and their Treatment. 158 Illustrations. Third Edition. Cloth, 300 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 ELECTRICITY. Bigelow. Plain Talks on Medical Electricity and Batteries. Illustrated. Cloth, i.oo Mason's Compend of Medical and Surgical Electricity. With numerous Illustrations. i2mo. Cloth, i.oo HYGIENE. Parkes' (Ed. A.) Practical Hygiene. Seventh Edition, en- larged. Illustrated. 8vo. Cloth, 4.50 Parkes' (L. C.) Manual of Hygiene and Public Health. Second Edition. i2mo. Cloth, 2.50 Wilson's Handbook of Hygiene and Sanitary Science. Seventh Edition. Revised and Illustrated. In Press. 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. Eleventh Edition. By the late John B. Biddle, M.D., Professor of Materia Medica in Jefferson Medical College, Philadelphia. Revised, and rewritten, by Clement Biddle, M.D., Assist. Surgeon, U. S. N., assisted by Henry Morris, M.D. 8vo., illustrated. Cloth, 4.25; Leather, 5.00 Potter. Materia Medica, Pharmacy and Therapeutics. Including Action of Medicines, Special Therapeutics, Pharma- cology, etc. Second Edition. Cloth, 4.00; Leather, 5.00 Waring. Therapeutics. With an Index of Diseases and Remedies. 4th Edition. Revised. Cloth, 3.00; Leather, 3.50 Jttt" See pages 14 and /jr for list of TQuiz-Contpends ? 10 STUDENTS' TEXT-BOOKS AND MANUALS. 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- STidence Society of Philadelphia; Physician to St. Joseph's ospital ; Corresponding Member of The New York Medico- legal Society. Third Edition. Cloth, 3.00; Leather, 3.50 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 Cazeaux and Tarnier's Midwifery. 'With Appendix, by Munde. The Theory and Practice of Obstetrics ; including the Diseases of Pregnancy and Parturition, Obstetrical Operations, etc. By P. Cazeaux. Remodeled and rearranged, with revi- sions and additions, by S. Tarnier, M.D., Professor of Obstetrics and Diseases of Women and Children in the Faculty of Medicine of Paris. Eighth American, from the Eighth French and First Italian Edition. Edited by Robert J. Hess, M.D., Physician to the Northern Dispensary, Philadelphia, with an appendix by Paul F. Munde, M.D., Professor of Gynaecology at the N. Y. Polyclinic. Illustrated by Chromo-Lithographs, Lithographs, and other Full-page Plates, seven of which are beautifully colored, and numerous Wood Engravings. Students' Edition. One Vol., 8vo. Cloth, 5.00; Leather, 6.00 Lewers' Diseases of 'Women. A Practical Text-Book. 139 Illustrations. Second Edition. Cloth, 2.50 Parvin's Winckel's Diseases of Women. Second Edition. Including a Section on Diseases of the Bladder and Urethra. 150 Illus. Revised. Seepages. Cloth, 3.00 ; Leather, 3.50 Morris. Compend of Gynaecology. Illustrated. Cloth, i.oo Winckel's Obstetrics. A Text-book on Midwifery, includ- ing the Diseases of Childbed. By Dr. F. Winckel, Professor of Gynaecology, and Director of the Royal University Clinic for Women, in Munich. Authorized Translation, by J. Clifton Edgar, M.D., Lecturer on Obstetrics, University Medical Col- lege, New York, with nearly 200 handsome illustrations, the majority of which are original with this work. Octavo. Cloth, 6.00; Leather, 7.00 Landis' Compend of Obstetrics. Illustrated. 4th edition, enlarged. Cloth, i.oo; Interleaved for Notes, 1.25 JKg~ See pages 2 to 5 for list of New Manuals. STUDENTS' TEXT-BOOKS AND MANUALS. 11 Obstetrics and Gyncecology : — Continued. Galabin's Midwifery. By A. Lewis Galabin, M.D., F.R.C.P. 227 Illustrations. Seepages. Cloth, 3.00; Leather, 3.50 Rigby's Obstetric Memoranda. 4th Edition. Cloth, .50 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 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 Virchow's Post-Mortem Examinations, sd Ed. Cloth, i.oo PHYSIOLOGY. Yeo's Physiology. Fifth 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 Brubaker's Compend of Physiology. Illustrated. Sixth 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. New i2th Ed. Thoroughly Revised and Enlarged. 502 Illustrations. Cloth, 4.00 ; Leather, 5.00 Landois' Human Physiology. Including Histology and Micro- scopical Anatomy, and with special reference to Practical Medi- cine. Third Edition. Translated and Edited by Prof. Stirling. 692 Illustrations. Cloth, 6.50; Leather, 7.50 " 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 PRACTICE. Taylor. Practice of Medicine. A Manual. By Frederick Taylor, M.D., Physician to, and Lecturer on Medicine at, Guy's Hospital, London ; Physician to Evelina Hospital for Sick Chil- dren, and Examiner in Materia Medica and Pharmaceutical Chemistry, University of London. Cloth, 4.00 ; Leather, 5.00 4®- See pages 14 and 13 for list of ? Quiz- Compends f 12 STUDENTS' TEXT-BOOKS AND MANUALS. Practice : — Continued. 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. 4th Edi- tion. 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. Physicians' Edition. Fourth Edition. Including a Section on Skin Diseases. With Index, i vol. Full Morocco, Gilt, 2.50 From John A. Robinson, M.D., Assistant^ to Chair of Clinical Medicine, now Lecturer on Mater ia Medica, Rush Medical Col- lege, Chicago. " Meets with my hearty approbation as a substitute for the ordinary note books almost universally used by medical students. It is concise, accurate, well arranged and lucid, . . . just the thing for students to use while studying physical diagnosis and the more practical departments of medicine." 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 ot Prescriptions, etc., etc. By Professor Jonathan Pereira, M.D. Sixteenth Edition. 32mo. Cloth, i.oo; Pocket-book style, 1.25 PHARMACY. Stewart's Compend of Pharmacy. Based upon Remington's Text-Book of Pharmacy. Third Edition, Revised. With new Tables, Index, Etc. Cloth, i.oo ; Interleaved for Notes, 1.25 Robinson. Latin Grammar of Pharmacy and Medicine. By H. D. Robinson, PH.D., Professor of Latin Language and Literature, University of Kansas, Lawrence. With an Intro- duction by L. E. Sayre, PH.G., Professor of Pharmacy in, and Dean of, the Dept. of Pharmacy, University of Kansas. i2mo. Cloth, 2.00 SKIN DISEASES. Anderson, (McCall) Skin Diseases. A complete Text-Book, with Colored Plates and numerous Wood Engravings. 8vo. Cloth, 4.50; Leather, 5.50 Van Harlingen on Skin Diseases. A Handbook of the Dis- eases of the Skin, their Diagnosis and Treatment (arranged alpha- betically). By Arthur Van Harlingen, M.D., Clinical Lecturer on Dermatology, Jefferson Medical College ; Prof, of Diseases of the Skin in the Philadelphia Polyclinic. 2d Edition. Enlarged. With colored and other plates and illustrations. i2mo. Cloth, 2.50 ee pages 2 to 5 for list of New Manuals. STUDENTS' TEXT-BOOKS AND MANUALS. IS SURGERY AND BANDAGING. Moullin's Surgery, A new Text-Book. 500 Illustrations, 200 of which are original. Cloth, 7.00; Leather, 8.00 Jacobson. Operations in Surgery. A Systematic Handbook for Physicians, Students and Hospital Surgeons; By W. H. A. Jacobson, B A., Oxon. F.R.C.S. Eng.; Ass't Surgeon Guy's Hos- pital ; Surgeon at Royal Hospital for Children and Women, etc. 199 Illustrations. 1006 pages. 8vo. Cloth. 5.00 ; Leather, 6.00 Heath's Minor Surgery, and Bandaging. Ninth Edition. 142 Illustrations. 60 Formulae and Diet Lists. Cloth, 2.00 Horwitz's Compend of Surgery, Minor Surgery and Bandaging, Amputations, Fractures, Dislocations, Surgical Diseases, and the Latest Antiseptic Rules, etc., with Differential Diagnosis and Treatment. By ORVILLE HOKWITZ, B.S., M.D., Demonstrator of Surgery, Jefferson Medical College. 4th edition. Enlarged and Rearranged. 136 Illustrations and 84 Formulae. 12010. Cloth, i.oo ; Interleaved for the addition of Notes, 1.25 *** The new Section on Bandaging and Surgical Dressings, con- sists of 32 Pages and 41 Illustrations. Every Bandage of any importance is figured. This, with the Section on Ligation ol Arteries, forms an ample Text-book for the Surgical Laboratory. 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 URINE, URINARY ORGANS, ETC. Holland. The Urine, and Common Poisons and The Milk. Chemical and Microscopical, for Laboratory Use. Illus- trated. Fourth Edition. i2mo. Interleaved. Cloth, i.oo Ralfe. Kidney Diseases and Urinary Derangements. 42 Illus- trations. i2mo. 572 pages. Cloth, 2.75 Marshall and Smith. On the Urine. The Chemical Analysis of the Urine. By John Marshall, M.D., Chemical Laboratory, Univ. of Penna ; and Prof. E. F. Smith, PH.D. Col. Plates. Cloth, i.oo Tyson. On the Urine. A Practical Guide to the Examination of Urine. With Colored Plates and Wood Engravings. 7th Ed. Enlarged. i2mo. Cloth, 1.50 Van Niiys, Urine Analysis. Illus. Cloth, 2.00 VENEREAL DISEASES. >per. Student's Manual of Venere Tulae. Fourth Edition. i2mo. 4&~ See pages 14 and ij for list of f Qmt-Compends f Hill and Cooper. Student's Manual of Venereal Diseases, with Formulae. Fourth Edition. i2mo. Cloth, i.oo NEW AND REVISED EDITIONS. PQUIZ-COMPENDS? The Best Compends for Students' Use in the Quiz Class, and when Pre- paring for Examinations. Compiled in accordance with the latest teachings of promi- nent lecturers and the most popular Text-books. They form a most complete, practical and exhaustive set of manuals, containing information nowhere else col- lected in such a condensed, practical shape. Thoroughly up to the times in every respect, containing many new prescriptions and formulae, and over two hundred and fifty illustrations, many of which have been drawn and engraved specially for this series. The authors have had large experience as quiz-masters and attaches of colleges, with exceptional opportunities for noting the most recent advances and methods. Cloth, each $1.00. Interleaved for Notes, $1.25. No. x. HUMAN ANATOMY, " Based upon Gray." Fifth Enlarged Edition, including Visceral Anatomy, formerly published separately. 16 Lithograph Plates, New Tables and 117 other Illustrations. By SAMUEL O. L. POTTER, M.A., M.D., M.R.C.P. (Lond.,) late A. A. Surgeon U. S. Army. Professor of Practice, Cooper Medical College, San Fran- cisco. Nos. 2 and 3. -PRACTICE OF MEDICINE. Fourth Edi- tion. By DANIEL E. HUGHES, M.D., Demonstrator of Clinical Medicine in Jefferson Medical College, Philadelphia. In two parts. PART I. — Continued, Eruptive and Periodical Fevers, Diseases of the Stomach, Intestines, Peritoneum, Biliary Passages, Liver, Kidneys, etc. (including Tests for Urine), General Diseases, etc. , . , , . PART II. — Diseases of the Respiratory System (including Phy- scal Diagnosis), Circulatory System and Nervous System; Dis- eases of the Blood, etc. *#* These little books can be regarded as a full set of notes upon the Practice of Medicine, containing the Synonyms, Definitions, Causes, Symptoms, Prognosis, Diagnosis, Treatment, etc., of each disease, and including a number of prescriptions hitherto unpub- lished. No. 4. PHYSIOLOGY, including Embryology. Sixth Edition. By ALBERT P. BRUBAKER, M.D., Prof, of Physiology, Penn'a College of Dental Surgery ; Demonstrator of Physiology in Jefferson Medical College, Philadelphia. Revised, Enlarged, with new Illustrations. No. 5. OBSTETRICS. Illustrated. Fourth Edition. By HENRY G. LANDIS, M.D., Prof, of Obstetrics and Diseases of Women, in Starling Medical College, Columbus, O. Revised Edition. New Illustrations. BLAKISTON'S ? QUIZ-COMPENDS ? No. 6. MATERIA MEDICA, THERAPEUTICS AND PRESCRIPTION WRITING. Fifth Revised Edition. With especial Reference to the Physiological Action of Drugs, and a complete article on Prescription Writing. Based on the Last Revision of the U. S. Pharmacopoeia, and including many unofficial remedies. By SAMUEL O. L. POTTER, M.A., M.D., M.R.C.P. (Lond.,) late A. A. Surg. U. S. Army ; Prof, of Practice, Cooper Medical College, San Francisco. Improved and Enlarged, with Index. No. 7. GYNAECOLOGY. A Compend of Diseases of Women. By HENRY MORRIS, M.D., Demonstrator of Obstetrics, Jefferson Medical College, Philadelphia. 45 Illustrations. No. 8. DISEASES OF THE EYE AND REFRACTION, including Treatment and Surgery. By L. WEBSTER Fox, M.D., Chief Clinical Assistant Ophthalmological Dept., Jefferson Med- ical College, etc., and GEO. M. GOULD, M.D. 71 Illustrations, 39 Formulae. Second Enlarged and Improved Edition. Index. No. 9. SURGERY, Minor Surgery and Bandaging. Illus- trated. Fourth Edition. Including Fractures, Wounds, Dislocations, Sprains, Amputations and other operations ; Inflam- mation, Suppuration, Ulcers, Syphilis, Tumors, Shock, etc. Diseases of the Spine, Ear, Bladder, Testicles, Anus, and other Surgical Diseases. By ORVILLE HORWITZ, A.M., M.D., Demonstrator of Surgery, Jefferson Medical College. Revised and Enlarged. 84 Formulae and 136 Illustrations. No. 10. CHEMISTRY. Inorganic and Organic. For Medical and Dental Students. Including Urinary Analysis and Medical Chemistry. By HENRY LEFFMANN, M.D., Prof, of Chemistry in Penn'a College of Dental Surgery, Phila. Third Edition, Revised and Rewritten, with Index. No. ii. PHARMACY. Based upon " Remington's Text-book of Pharmacy." By F. E. STEWART, M.D. , PH. G., Quiz-Master at Philadelphia College of Pharmacy. Third Edition, Revised. No. 12. VETERINARY ANATOMY AND PHYSIOL- OGY. 29 Illustrations. By WM. R. BALLOU, M.D., Prof, of Equine Anatomy at N. Y. College of Veterinary Surgeons. No. 13. DENTAL PATHOLOGY AND DENTAL MEDI- CINE. Containing all the most noteworthy points of interest to the Dental student. By GEO. W. WARREN, D.D.S., Clinical Chief, Penn'a College of Dental Surgery, Philadelphia. Illus. No. 14. DISEASES OF CHILDREN. By DR. MARCUS P. HATFIELD, Prof, of Diseases of Children, Chicago Medical College. Colored Plate. Bound in Cloth, $1. Interleaved, for the Addition of Notes, $1.25. Jg^0 These books are constantly revised to keep up -with the latest teachings and discoveries, so that they contain all the new methods and principles. No series of books are so complete in detail^ concise in language ', or so well printed and bound. Each one forms a complete set of notes upon the subject under consideration. : Illustrated Descriptive Circular ( JUST PUBLISHED. GOULD'S NEW MEDICAL DICTIONARY COMPACT. CONCISE. PRACTICAL. ACCURATE. COMPREHENSIVE UP TO DATE. It contains Tables of the Arteries, Bacilli, Gan- glia, Leucomames, Micrococci, Muscles, Nerves, Plexuses, Ptomaines, etc., etc., that will be found of great use to the student. Small octavo, 520 pages, Half-Dark Leather, . $3.25 With Thumb Index, Half Morocco, marbled edges, 4.25 From J. M. DACOSTA, M. D., Professor of Practice and Clinical Medicine, Jefferson Medical College, Philadelphia. "I find it an excellent -work, doing credit to the learning and discrimination of the author" *** Sample Pages free. A UNIQUE BOOK. POTTER'S MATERIA MEDICA, PHARMACY AND THERA- PEUTICS. Second Edition. Revised and Enlarged. A Hand- book; including the Physiological Action of Drugs, Special Therapeutics of Diseases, Official and Extemporaneous Pharmacy, etc. By S. O. L. POTTER, M.A., M.D., Professor of the Practice of Medicine in Cooper Medical College, San Francisco; Late A. A. Surgeon, U. S. Army, etc. A new Edition in larger type. Octavo. Cloth, $4.00; Leather, $5.00. DR. POTTER has become well known as an able compiler, by his Compends of Anatomy, and of Materia Medica, both of which have reached four editions. In this book, more elaborate in its design, he has shown his literary abilities to much better advantage, and all who examine or use it will agree that he has produced a work containing more correct information in a practical, concise form than any other publication of the kind. The plan of the work is new, and its contents have been combined and arranged in such a way that it offers a compact statement of the subject in hand. PART I. — MATERIA MEDICA and THERAPEUTICS, the drugs being arranged in alphabetical order, with the synonym of each first; then the description of the plant, its preparations, physiological action, and lastly its Therapeutics. This part is preceded by a section on the classification of medicines as follows: Agents acting on the Nervous System, Organs of Sense, Respiration, Circu- lation, Digestive System, on Metabolism (including Restoratives, Alteratives, Astringents, Antipyretics, Antiphlogistics and Antiperiodics, etc.). Agents act- ing upon Excretion, the Generative System, the Cutaneous Surfaces, Microbes and Ferments, and upon each other. PART II. — PHARMACY AND PRESCRIPTION WRITING. Written for the use of physicians who put up their own prescriptions. It includes — Weights and Measures, English and the Metric Systems. Specific Gravity and Volume. Prescriptions. — Their principles and combinations ; proper methods of writing them; abbreviations used, etc. Stock solutions and preparations, such as a doctor should have to compound his own prescriptions. Incompatibility, Pharmaceutical and Therapeutical. Liquid, Solid and Gaseous Extempo- raneous Prescriptions. PART III. — SPECIAL THERAPEUTICS, an alphabetical List of Diseases — a real INDEX OF DISEASES — giving the drugs that have been found serviceable in each disease, and the authority recommending the use of each ; a very im- portant feature, as it gives an authoritative character to the book that is unusual in works on Therapeutics, and displays an immense amount of research on the part of the author. 600 prescriptions are given in this part, many being over the names of eminent men. THE APPENDIX contains lists of Latin words, phrases and abbreviations, with their English equivalents, used in medicine, Genitive Case Endings, etc. 36 Formulae for Hypodermic Injections; a comparison of 10 Formulae of Chloro- dyne; Formulae of prominent patent medicines; Poisons and their Antidotes; Differential Diagnosis ; Notes on Temperature in Disease ; Obstetrical Memo- randa; Clinical Examination of Urine; Medical Ethics; Table of Specific Gravities and Volumes ; Table showing the number of drops in a fluidrachm of various liquids and the weight of one fluidrachm in grains, and a table for converting apothecaries' weights and measures into grams. A MINE OF WEALTH FOR THE STUDENT. Standard Text-Books. LANDOIS' HUMAN PHYSIOLOGY. A Text-Book of Human Physi- ology, including Histology and Microscopical Anatomy, with special reference to the requirements of Practical Medicine. By Dr. L. LANDOIS, Professor of Physiology and Director of the Physiological Insti- tute, University of Greifswald. Translated from the Fifth German Edition, with additions by WM. STIRLING, M.D., SC.D,, Brackenburg, Professor of Physiology and Histology in Owen's College and Victoria University, Man- chester; Examiner in the Honors' School of Science, University of Ox- ford, England. Third Edition, revised and enlarged. 692 Illustrations. One Volume. Royal Octavo. Cloth, $6.50; Leather, $7.50. " With this Text-book at command, NO STUDENT COULD FAIL IN HIS EXAMINATION." — Tlu Lancet. " One of the MOST PRACTICAL WORKS on Physiology ever written, forming a ' bridge ' be- tween Physiology and Practical Medicine. . . .Its chief merits are its completeness and conciseness. . . . EXCELLENTLY CLEAR, ATTRACTIVE AND SUCCINCT." — British Medical Journal. " Unquestionably the most admirable exposition of the relations of Human Physiology to Practical Medicine ever laid before English readers."— Students' Journal. " Landois' Physiology is, without question, the best text-book on the subject that has ever been written."— W«* York Medical Record. CAZEAUX AND TARNIER'S MIDWIFERY. Eighth Revised and Enlarged Edition. With Appendix, by Munde. The Theory and Practice of Obstetrics; including the Diseases of Pregnancy and Parturition, Obstetrical Operations, etc. By P. CAZEAUX, Member of the Imperial Academy of Medicine. Remodeled and rearranged, with revisions and additions, by S. TARNIER, M.D., Prof, of Obstetrics and Diseases of Women and Children in the Faculty of Medicine of Paris. Eighth American, from the Eighth French and First Italian Editions. Edited and Enlarged by ROBERT J. HESS, M.D., Physician to the Northern Dispensary, Phila., etc., with an Appendix by PAUL F. MUNDE, M.D., Professor of Gynaecology at the New York Poly clinic, Vice -President American Gynaecological Society, etc. With Chromo-Lithographs, Litho- graphs, and other Full-page Plates, seven of which are beautifully colored, and numerous Wood Engravings. One Volume, octavo. Cloth, $5.00; Full Leather, £6.00. MEYER ON DISEASES OF THE EYE. ,„ ...^nual of Ophthal- mology. By Dr. EDOUARD MEYER, Prof, a 1'Ecole Pratique de la Faculte Medecine de Paris; Chevalier of the Legion of Honor, etc. Translated from the Third French Edition, with the assistance of the author, by Dr. FREELAND FERGUS, Assistant Surgeon, Glasgow Eye Infirmary. With 267 Illustrations and three Colored Plates. Prepared under the direction of Dr. R. Liebreich. 8vo. Cloth, $4.50; Leather, $5.50. The first chapter is an explanation of the best means for examining the eyes, externally and internally, with a view to diagnosis, the various ophthalmo- scopes, general considerations on the treatment of ophthalmia, etc. Each dis- ease is then taken up in its proper order; the anatomy of the part being pre- sented first, followed by the diagnosis, causes, progress, prognosis, etiology and Jreatment. The arrangement of the work will thus be seen to be systematic, commending itself to all physicians and students for the logical and concise way in which the facts are given. This English edition makes the eighth language into which Meyer's book has been translated. P. BLAKISTON, SON & CO., Publishers and Booksellers, 1012 WALNUT STREET, PHILADELPHIA, W 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 Anatorry at, St. Bartholomew's Hospital. 208 Illustrations. 8vo. Cloth, $$.00-, Leather, $6.00. Oil-cloth Covers, for the Dissecting Room, $4.50. The popularity of this work has steadily increased during the past few years. It is proba- bly used more extensively than any other dissector. The Oil-cloth binding allows of wash- ing, and does not retain the dirt and odor of the dissecting table. This edition has been carefully printed and bound, and lays open flat at any page. " 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 ith this stuy and r these points be emphasized to such as are commencing their studies. The text matches the description. All this is known to those who are already acquainted with this admirable work ; but it is simpe justice to its value, as a work for careful study and reference, that illustrations in directness of practical application and clearness of detail." — New York Med- ical Record. ANDERSON ON SKIN DISEASES. A complete Treatise on Skin Diseases. By McCALL ANDERSON, M.D., Professor of Clinical Medicine, University of Glasgow. With numerous wood engravings and several col- ored and steel plates. Octavo. Cloth, $4.50. Leather, $5.50. Just Ready. This aims to be a complete text-book. It will be found to contain all the latest methods of treatment. The subject is dealt with in a systematic, practical manner, and is based on an extensive experience of nearly twenty-five yean. GOWERS' MANUAL OF DISEASES OF THE NERVOUS SYSTEM. A Complete Text-book. By WILLIAM R. GOWERS, M.D., Professor Clinical Medicine, University College, London. Physician to National Hospital for the Paralyzed and Epileptic. Comprising over 400 Illustrations and 1 360 pages. Octavo. Cloth, $6.50; Leather, $7.50. 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 Medical College ; Surgeon to the Woman's Hospital; Ex- President American Gynaecological Society, etc. ; and HENRY T. BYFORD, M.D., Surgeon to the Woman's Hospital of Chicago ; Gynaecologist to St. Luke's Hospital ; President Chicago Gynaecological Society, etc. Fourth Edition, Revised, Rewritten and Enlarged. With 306 Illustrations, over 100 of which are original. Octavo. 832 pages. Cloth, $5.00; Leather, $6.00. " In short, the book is brought up to the standard of to-day, and in most respects may be considered a reliable, practical text-book, written by an earnest worker anp) practical man." <— American Journal of Medical Sciences. ROBERTS. PRACTICE OF MEDICINE. The Theory and Prac- tice of Medicine. By FREDERICK ROBERTS, M.D., Professor of Thera- peutics at University College, London. Seventh American Edition, thoroughly revised and enlarged, with new Illustrations. 8vo. Cloth, £5.50; Leather, #6.50. " If there is a book in the whole of medical literature in which so much is said in so few words, it has never come within our reach." — Chicago Medical Journal. " The best text-book for students. We know of no work in the English language, or of •By other, which competes with this one."— Edinburgh Medical Journal. P. BLAKISTON, SON & CO., Publishers and Books«ll«rs. 1012 WALNUT SHEET, PHILADELPHIA.