Digitized by tine Internet Arciiive in 2010 with funding from Columbia University Libraries http://www.archive.org/details/humanphysiologypOOraym '■"■'■'^^oni^f;^'- HUMAN PHYSIOLOGY PREPARED WITH SPECIAL REFERENCE TO STUDENTS OF MEDICINE BY JOSEPH HOWARD RAYMOND, A.M., M.D. Professor of Physiology and Hygiene in the Long Island College Hospital, and Director of Physiology in the Hoagland Laboratory, New York City SECOND EDITION. ENTIRELY REWRITTEN 443 Illustrations, some of them in Colors, and 4 full-page Lithographic Plates PHILADELPHIA AND LONDON W. B. SAUNDERS & COMPANY 1 901 Copyright, 1901, by W. B. Saunders & Company Registered at Stationers' Hall, London, England PRESS OF B. SAUNDERS & COMPANY. TO THE MEMORY OF ALEXANDER JOHNSTON CHALMERS SKENE, M.D.. LL.D, COLLEAGUE AND FRIEND FOR MORE THAN A QUARTER OF A CENTURY This Volume is Affectionately Inscribed by THE AUTHOR PREFACE TO THE SECOND EDITION. The extension of the medical curriculum to a period of" four years and the lenj>;tiieniug of the individual courses composing it present o})portunities for the instruction of medical students in physiology which were not possible under the old system of medical education. If, in addition to this, the advances which have been made within recent years in physiologic science are taken into consideration, both the advantage of and the necessity for an enlargement and thorough revision of the first edition of this volume are a})parent. The same subdivision of the subject into Physiologic Chemistry, and Nutritive, Nervous, and Reproductive Functions has been retained, Avliile so much of Histology has been added, not only in a section under that heading, but also throughout the text, as will enable the student better to understand the physiologic anatomy of the organs whose functions he studies. Special attention has been given to the subject of alcohol in connection with its influence upon mouth digestion and gastric digestion, copious references being made to the experiments of Chittenden, Mendel, and Jackson, and to those of Atwater in the work of the Committee of Fifty for the Investigation of the Drink Problem. The experiments of Cannon and Moser in connection with deglutition, and of the former of these investigators in connection with the movements of the stomach, in which use was made of the Rontgen rays to elucidate the questions involved, have received extensive and well-deserved mention. In the discussion of the functions of the stomach, the results of the removal of that organ by Schlatter and Brigham have been described, to which has been added a detailed history of the cases operated upon by them, so far as relates to the points of physio- logic interest connected therewith. The subjects of internal secretion, especially of the thyroid, 9 10 PREFACE TO THE SECOND EDITION. and the rationale of the use of thyroid extract in tlie treatment of myxedema ; the coagulation of the blood ; the absorption of fat ; and the most recent contribution of Chittenden to the genesis of uric acid, have been concisely though not exhaustively considered. A portion of the volume which the author considers as especially worthy of attention is that which describes the results of photo- graphing the larynx by Prof. French, whose labors in this field have revolutionized the theories of voice-production. In the portion of the volume devoted to the Nervous Functions many changes have been necessary by reason of the now generally accepted " neurone theory " ; and the sections devoted to the senses of sight and hearing have been greatly elaborated. In the discussion of the Reproductive Fimctions increased stress has been laid upon the divergent views held by writers as to the relation of menstruation and ovulation. Students desiring fuller knowledge of the human functions are referred to the American Text-book of Physiology, where they will be found discussed in extenm by leading physiologists of the present day. In connection with this, as with any other text-book on phy- siology, thorough laboratory practice is highly recommended for all students who desire to master the subject ; indeed, without it the knowledge obtained must of necessity be incomplete and soon forgotten. The author desires to express his api)reciati()n of the pains- taking care of the publishers in the preparation of this volume and of their liberality in supplying the illustrations, to the number of which they liave set no limit. He also desires to express his thanks to authors and publishers who have permitted the use of their writings and their illustrations, due credit for which he has endeavored to give in the text where they occur. If this has been overlooked in any instance, it has been through inadvertence. PREFACE. The author's experience of twenty years as a teacher of Physiology to medical students has brought him to the con- clusion tliat in the short time allotted to the study of physi- ology in medical schools students can assimilate only the main facts and principles of this branch of medicine, uhich lies at the very foundation of a sound knowledge of the healing art ; and that even if there were time to investigate the more recondite and abstruse parts of the subject, such an investiga- tion would be profitless during this formative period. In his teaching the author has kept this thought constantly in mind, and in this manual has endeavored to put into a concrete and available form the results of his experience. 11 CONTENTS INTRODUCTION 17 Dctinitiiiiis, 17 — Briuulics of Physiology, 19 — Iluiiiiin Physiology Dctiiiod, 20 — Classification of Functions, 21 — Histology of the Human Body, 21 — Physiologic Clieinistry, 21 — Arrangement of Topics, 22. I. HISTOLOGY OF THE HUMAN BODY 23 Cells, 2;5— Division of Cells, 28. Elementary Ti-ssues, 30 — Epithelial Tissue, 30 — Connective Tissue, 34 — Areolar Tissue, 34— Adipose Tissue, 35— Retiform Tissue, 37 — Lymphoid Tissue, 38— Jelly-like Tissue, 38— Cartilage, 38— Bone, 41 — Dentin, 50 — Muscular Tissue, 56 — Voluntary Muscle, 56 — Invol- untary Muscle, 61 — Nervous Tissue, 63— Nerve-fihers, 63— Nerve- cells, 69 — Neuroglia, 72 — Development of Nerve-cells and Nerve- fibers, 73 — Chemistry of Nervous Tissue, 74. n. PHYSIOLOGIC CHEMISTRY 76 Inorganic Ingredients, 77 — Carbohydrates, 87 — Fats, 99 — Proteids, 102— Albumins, 107— Albuminates, 109— Globulins, 110— Nucleopro- teids. 111 — Proteoses and Peptones, 113 -Coagulated Proteids, 113 — Poisonous Proteids, 113 — Albuminoids, 115 — Enzymes, 117 — Metabo- lism, 120— Food, 121— Milk, 138— Mammary Glands, 142— Eggs, 145 — Meat. 147^Cereals, 149— Vegetables, 151— Beverages, 152 — Effects of Alcohol upon the Human Body, 154. m. NUTRITIVE FUNCTIONS 162 DiGKSTION 162 Mouth Digestion, 164— Stomach Digestion, 185 — Coats of the Stom- ach, 186— Quantity of Gastric Juice, 189 — Composition of Human Gastric Juice Mixed with Saliva, 189— Action of the Gastric Juice, 193— Movements of the Stomach, 194— Vomiting, 199— Effect of Nervous Disturbances upon Gastric Digestion, 202 — Self-digestion of the Stomach, 202— Duration of Stomach Digestion, 203— Removal of the Human Stomach, 205— Achylia Gastrica, 213— Artificial Gastric Juice, 214— Intestinal Digestion, 215— Structure of the Small Intes- tine, 215 — Structure of the Large Intestine, 221 — Succus Entericus or Intestinal Juice, 222— The Pancreas, 223 — Structure of the Pancreas, 223 — Pancreatic Juice, 226 — Innervation of the Pancreas, 231 — In- ternal Secreti()n of the Pancreas, 233— The Liver, 233 — Chemical Composition, 233— Structure, 234— Hepatic Artery, 234 — Portal Vein, 234— Hepatic Duct, 235— Gall-bladder, 236— Bile, 237— Innervation, 244— Digestion in the Large Intestine, 244— Bacterial Digestion, 244. Absorption of the Food 245 Mouth Absorption, 246 — Gastric Absorption, 246 — Absorption by the Small Intestine, 247— Glycogenic Function of the Liver, 248 — Formation of Glycogen from Carbohydrates, 248— Formation of Gly- 14 COXTEXTS. PAGE cogen from Proteids. 249— Formation of Glycogen from Fats, 249 — Glycogenic Theory, 249— Diabetes, 251 — Absorption of Proteids, 252 — Absorption of Vegetable and Animal Proteids, 253 — Absorption of Fat, 253-'-Absorption by the Large Intestine, 256. Feces and Defecation 257 Quantity of Feces, 257 — Color of Feces, 257 — Reaction of Feces, 258 — Composition of Feces, 258 — Meconium, 258 — Defecation, 258. Blood 260 Physical Properties of Blood, 260- Distribution. 262— 3Iicroscopic Structure, 262— Blood-serum, 283— Coagulaiiion of Blood, 286— Re- generation of Blood, 291. Lymph 292 Chemical Composition, 292 — Histologic Composition, 292 — Origin, 293— Chyle, 295. CiRCrLATORY SYSTEM 295 The Heart, 295— The Arteries, 298— The Capillaries, 300— The Veins, 300— Circulation of the Blood, 301— Blood-pressure. 308 — Rate of Blood-flow in the Vessels. 312— The Pulse, 315— The Plethysmo- graph, 318 — Circulation in the Veins, 318. Lymphatic System 319 Lymphatic Vessels, 319 — Lymphatic Glands, 321 — Cavities of Ser- ous Membranes, 322 — Circulating Lymph, 323. DrcTLEss Glands 323 The Spleen, 324— The Thyroid and Parathyroid, 328— The Thymus, 335— The Suprarenal Capsules, 336— The Pineal Gland, 340— The Pituitary Body, 340— The Carotid and the Coccygeal Glands, 341. Respiration 341 The Xose, 342— The Larynx, 343— The Trachea, 350— The Bronchi, 351— The Lungs, 351— The Pleura, 354— The Thorax, 354— Respira- tory Movements, 361 — Capacity of the Lungs, 363 — Types of Respira- tion, 364 — Chemistry of Respiration, 365. Voice and Speech 378 Laryngoscope, 379— Resonance, 380 — Intensity, 381 — Pitch, 381 — Quality, 382— Registers, 382— Speech, 382— Vowels, 383— Consonants, 383— Photography of the Larynx, 383. Vital Heat 395 Warm-blooded Animals, 395— Homoiothermal Animals, 396 — Poi- kilothermal Animals. 396 — Temperatures of Different Animals, 396 — Temperature of Different Parts of the Body, 396 — Temperature at Different Ages, 397 — Daily Variations in Temperature, 397 — Remark- able Instances of High and Low Temperature, 397 — Sources of Vital Heat, 398— Channels Through which Vital Heat is Lost, 399— Calor- imetry, 399 — Regulation of Temperature, 401. The Skin 402 Coriurn, 402 -Epidermis, 402 — Perspiratory Glands. 402 — Sebaceous Glands, 405 — Cerumen, 406 — Hairs and Nails, 406 — Functions of the Skin, 407— Care of the Skin, 408. The Urinary Apparatus 410 The Kidneys, 410— Ureteis, 417— Bladder, 418— Urethra, 419. CONThWrs. 15 PAGE TiikUkine 420 (•iuaiitity, 420— Color, 420-Keactioii, 420— Specilic (iravity, 421 — Composition, 421 — Inorganic Constituonts, 428. Trkitahility ; CoNTRACTiMTY ; Elkctkk' Phknomkna ok Musclk . 480 IV. NERVOUS FUNCTIONS 448 (ioiicral Conf-iderations, 448— Nerves, 449 — Ncrve-inipulscs, 4")?) — Tiiu Ner\H)Us System, 4")() — Spinal Cord, 456 — Funotictns of tlii; Spinal Curd, lii") — RcHex Time, 467 — Reflexes in Man, 467 — Special Centers in the Cord, 46!) — Functions of Spinal Nerves, 470. The Brain 471 The Medulla Oblongata, 472 — The Cerebellum, 477— The Cerebrum, 483— Cranial Nerves, ^501. The Sen.ses 515 General Sensibility, 515 — Sense of Touch, 515 — Sense of Pressure, 517 — Muscular Sense, 517 — Sense of Temperature, 517 — Sense of Pain, 518— Sense ot Smell, 518— Olfiictory Nerves, 519— Olfactory Bulb, 519 —Olfactory Tract, 521 — Functions of the Olfactory Nerves, 521 — Sense of Taste, 523— Ci ream vallate Papilla?, 524— Conical Papilhe, 525 — Fungiform Papilhe, 525 — Taste-buds, 525 — Conditions of the Sense of Taste, 528— Sense of Sight, 529— Coats or Tunics, 529— Sclerotic Coat, 529— Cornea, 529— Choroid, 582— Ciliary Processes, 533— Iris, 533 — Ciliary Body, 535 — Retina, 535 — Anterior and Posterior Cham- bers, 542 — Vitreous Body, 542 — Crystalline Lens, 542 — Suspensory Ligament, 548 — Chemistry of the Eye, 543 — Ocular Muscles, 544 — Physiology of Vision, 548 — Defects in the Visual Apparatus, 557 — The Iris^'562— The Ptetina, 563— Light, 568— Form, 570— Identical Points, 570 — Size, 570 — Distance, 571— Color, 571 — Color-blindne.ss or Daltonism, 577 — Fatigue of Retina, 578 — After-images, 578 — Visual Judgment, 579 — Appendages of the Eye, 581 — Lacrimal Apparatus, 581 — Meibomian Glands, 581 — The Sense of Hearing, 582 — External Ear, 582 — Middle Ear, 584— Membrana Tympani, 584 — Tympanic Cavity, 586— Ossicles, 586— Eustachian Tubes, 588— Mastoid Antrum, 589 -Fenestra Ovalis, 589 — Fenestra Rotunda, 590 — Physiology of Hearing, 600— Theories of Hearing, 602— Period, 604 — Amplitude, 604 — Frequency, 604 — Noises, 604 — Musical Sounds, 604 — Intensity, 605— Loudness, 605— Pitch, 605— Quality, 605. V. REPRODUCTIVE FUNCTIONS 608 Reproductive Organs, 608— Genital Organs of the Male, 609 — Testes, 609— Penis, 614— Genital Organs of the Female, 615— Ovary, 615— Fallopian Tubes, 624— IT terus,"624— Ovulation, 626— Menstrua- tion, 629 — Formation of the Corpus Luteum, 638 — Maturatif)n of the Ovum, 638— Impregnation, 635 — Erection of the Penis, 635 — Ejacu- lation, 636 — Ovarian and Abdominal Pregnancy, 637 — ]Method of Fertilization, 639— Segmentation, 640 — Formation of the Embryo, 640— Development of the Chick, 641— Membranes <>f the Embryo, 642— Amnion, 642— Yolk-sac, 643— Allantois, 648— Chorion, 643— Placenta, 648— Circulation in the Embryo, 644 — Changes in the Cir- culation at Birth, 646. Index 649 HUMAN PHYSIOLOGY. INTRODUCTION. Definitions. — Pliysiology is the mience ichich treats of func- tions. J]y the term fuiictioii is meant the eharaeteristic work performed by an organ. An organ may be defined as a structure which performs a function or functions, for the special or char- acteristic work of an organ may not -be limited to a single function : thus the pancreas secretes not only pancreatic juice, whicii is its external secretion, but also another product, which is its internal secretion {i^. 233). Lifeless things perform no functions, hence physiology has no dealings with inanimate things. Rocks, stones, and other members of the mineral kingdom at no time possess life ; consequently they perform no functions, and with them physiology has no concern : we cannot speak of the physi- ology of minerals. Plants and animals are sometimes living and sometimes dead : when living they perform functions, when dead they perform no functions ; in the latter condition they are like the rocks so far as function is concerned, and with them physiology has nothing whatever to do. It is only when they are living that they perform functions, and it is then and only then that with them physiology concerns itself. Another definition which might be given of physiology is, that it is the science ichich treats of vital phenomena. A brief consideration of this definition will bring us to the same conclu- sion as did that of the preceding dcfiniticm. Of life in its essence we know nothing. Metaphysicians have endeavored to ex})laln life, and some have even ventured to point out its seat, but the fact remains that we are utterly ignorant of its nature. We only- know that it exists by certain manifestations which it presents.. AVhen we see a growing plant or a moving animal, we say of each that it is alive. In the higher forms of animals and plants it is. easy, under ordinary circumstances, to determine whether they are living or not ; but in the lower forms this determination is some- times a mo.st difficult task. The evidences upon which reliance is placed to determine the presence or the absence of life are spoken of as vital phenomena. Thus, if in examining an animal we find that its heart beats, we .say that the animal is alive ; but 2 '■ 17 1 8 INTR OD UCTION. if the heart is motionless, we say that tlie animal is dead. This beating of the heart, therefore, is a vital phenomenon — that is, a manifestation of life. We speak also of this beating of the heart as its fnnction ; hence the first definition of physiology, that it is the science which treats of functions, and the second definition, that it is the science which treats of vital phenomena, amount to the same thing. Definition of "Organ." — An organ has already been defined as a structure which performs a function or functions. In speaking of the organs of an animal reference is usually had to such struct- nres as the heart, the lungs, and the stomach, inasmuch as their size and the important work they perforin force them upon our attention. These are indeed organs, for they perform functions ; thus the function of the heart is to receive blood in one portion and to propel it from another portion, that of the Inngs is to aerate the blood, and that of the stomach is to digest certain kinds of food ; but the term organ, as used in physiology, has a mnch broader signification. A muscle, a nerve, and a blood-vessel are as truly organs as are the greater ones above spoken of, for each has its own function. Thus the function of a muscle is to contract, that of a nerve is to transfer nervous impulses, and that of a blood- vessel is to convey blood. At first sight it might seem that these functions were unimportant, and that the structures which per- formeil them were hardly worthy of so dignified a name as organs; but a moment's reflection will show that without the contraction of muscles, the transference of nervous impulses, or the carrying of blood the life of an animal would as certainly cease as if it was deprived of its heart, of its lungs, or of its stomach. Inasmuch as minerals, on the one hand, possess no organs, they perform no work — that is, they have no functions ; therefore we do not speak of the physiology of a mineral. Plants and ani- mals, on tlie other hand, possess organs, each of which performs its special function ; and it is with them, as has l)een said, that physiology has to do. As we find organs in the animal, so do we find them in the plant ; not the same organs, it is true, but struct- ures which are as truly organs, for they respond to the same test. The roots of a plant absorb moisture and nourishment from the soil, this being their function ; the green leaves take up from the air carbonic acid, with which and with water they form starch that is utilized by the plant, while oxygen is set free, this being the function of the leaves ; the anthers and the ovaries of flowers are concerned in reproducing plants by forming new ones, this being their function. Thus we might continue to show that as in animals, so in plants, the diflerent organs have their respective functions. Definition of "Organic" and "Inorganic." — AVe can now under- stand the meaning of two very important terms — organic and BRA^THES OF PHYSIOLOGY. 19 inorf/cniic. These terms are used in two senses : first, as to Mrucf- uir, and, second, as to prodnrt. When we say that a plant or an animal is organic, we mean that it is made up of organs — that is, of structures which perform functions. The })lant or the animal may he simple or may he complex, but, however simple or however com})lex, its parts do something-, that something being: the function of the part which acts. We say, therefore, that the plant or animal is organic, meaning that it is composed of organs — organic, then, as to structure. The rock has no organs, therefore it is no)i-urf/((iiic, or is inorganic. These terms are used also in another sense. Thus we speak of honey as organic. Mani- festly, we do not mean organic as to structure, for honey has no organs, that is, no parts which perform functions, but it is the product of the bee, which is an organic structure ; hence honey is an organic product. The nectary of a flower is organic as to structure, and the nectar which it produces is also organic, inasmuch as it is the product of the nectary. But organs do not act each for itself: they are, as a rule, associated in the performance of a common function, and thus associated form a system. Thus the group of organs which are concerned in digestion forms the digestive system ; those which together accomplish the circulation of the l)lood, the circulatory system. An attempt has been made to distinguish an apparatus from a si/.-r the lerforms its function in an abnormal manner, and to succeed in correcting the diseased condition one must first be able to recognize this abnormal action, which can only be done by knowing how the organ acts in health — that is, by understanding its physiology. Even with this knowledge one may be unable to accomplish the desired object, for the structure of the organ may be so changed that no means can be applied which will restore it to its normal condition ; but one is certainly more likely to succeed if possessed of a knowledge of its physiology than if ignorant of it. The study of human physiology is but the study of the human fiHictions, and when these functions are thoroughly understood the science is mastered. Classification of Functions. — The functions of the body may be classified as follows : 1. Nutritive Function.'^, which include those concerned directly with the maintenance of the individual, such as digestion, res])iration, circulation, etc.; 2. Nervo^is Func- tions, which include those that bring the different organs of the body into harmonious relations with one another, and, in addition, bring the individual, through the special senses — sight, hearing, etc. — into relation with the world outside him ; and 3. Reproductive Functions, which are concerned not with the individual, but with the species, which they perpetuate. Histology of the Human Body. — Anatomy, as we have already learned, is the science which treats of structure ; and this is true as well of the minute or microscopic as of the gross or macroscopic structure ; but it will be of advantage to the student of physiology to have distinctly in mind so much of the histology or minute structure of the body as is necessary to a full under- standing of its functions, and to appreciate the discussion of them. With this end in view, the histology of each organ will be given in connection with its function, but preliminary to all this ^^'e shall discuss the tissues of the body which go to make up these organs. For fuller details the student is referred to the many excellent treatises on human histology. Physiologic Chemistry. — Although physiology, strictly speaking, has nothing to do with composition, still, as a matter of necessity as well as of convenience, it is usual to preface the study of the functions of the human body with a greater or lesser consideration of its composition. This consideration" is necessary, because, as a rule, medical students have an insufficient knowledge of this branch of chemistry — physiologic chemistry— to take up at once the study of the ifunctions with profit, and should the 22 INTRODUCTION. attempt be made confusion and loss of time would inevitably result. As an illustration we may refer to the function or series of functions by which the food is prepared for absorption — that is, dio;estion. Food is the material which is taken into the body to supply the waste of its tissues, and it must be of such a composi- tion as will meet this want. To select the proper food-materials we must know of what the body is composed, and what are the changes which take place in its composition — what parts are wasted. For these reasons a study of physiologic chemistry must precede a study of the functions of digestion. This is but one of many illustrations which might l)e given to show the importance of prefacing tlie study of physiology proper with a study of the chemistry of the liody and of the food. Arrangement of Topics. — The topics treated of in this work will therefore be arranged in the following order : I. Histology of the Human Body ; II. Physiologic Chemistry ; III. Nutritive Functions; IV. Nervous Functions; V. Reproductive Functions. I. HISTOLOGY OF THE HUMAN BODY. Organs on minute examination are found to be made up of tissues, or elementary tissues as they are sometimes called. Of elementary tissues there are four: 1. Epithelial; 2. Con- nective ; 3. Muscular ; and 4. Nervous. Some oro-ans contain all four kinds of tissues, while others, more simple in their structure, contain but one or two. If these tissues are still further analyzed, they are seen to con- sist of cells or fibers, or of both together in varying proportions : thus the epithelial tissues are made up of cells alone ; the con- nective tissue, principally of fibers ; and the nervous, of both cells and fil)ers. Cells (Fig. 1). — A cell consists of protoplasm, a nucleus, and a centrosome*' and attraction-sphere, A cell-membrane euclos- Vaciioles Chromatin networ Linin network Nuclear fluid Nuclear membrane. - Cell-membraue. - . Exoplasm Spongioplasm. Hyaloplasm. Nucleolus Chromatin net-knot. l._ii-J-J Centrosome. Centrosphere. Foreign inclosures. Mctaplasm. Fig. 1. ^Diagram of a cell (Huber). ing the protoplasm may or may not be present ; it is not an essential part of a cell as are the other structures. A centrosome 23 24 CELLS. and attraction-sphere have l>een found in so many cells that they mav be regarded as essential constituents of every cell. Protoplasm. — This is the principal ])art of a cell, and is of an albuminous nature. Chemically it consists of water (75 per cent, or more), proteids, lecithin, cholesterin, and phosphates and chlo- rids of .sodium, potassium, and calcium, and sometimes fat and glvcogen. Microscopically examined it is found to be made up of spongioplasni and hyaloplasm. Spoiif/ioplasiii. — Under high powers of the microscope the pro- toplasm of a cell presents the appearance of a fine network, called reticulum, sponrjeicork, or spongioplasm. This network has in it knots, which give to it a granular appearance. These knots or granules are of the same chemic nature as the network — that i.s, are albuminous or proteid. It is still undecided whether these granules are constituent parts of the protoplasm or are its products. Collectively they are denominated granulopla-im. Other granules mav be present which are not connected with the network, and which are not proteid in character, but fatty or starchy or con- tain coloring-matter. In some instances they are of an inor- ganic natin-e. Granules of this latter kind constitute paraplasm ; by which is meant any and all material contained in a cell, not being an actual part of it, whether there as pabulum or food for the cell, or as waste material to be excreted. Hyaloplasm, — In the meshes of the spongioplasm is the hyalo- plasm, a clear substance differing but slightly in its consistence from the spongio])lasm, although it is less .solid. Ameboid Movement. — Protoplasm is endowed with the power of motion, which from its resemblance to the motion of the anieba, a minute animal, which is but a mass of protoplasm, is called ameboid. Examined under the microscope the ameba puts out from its sides projections of its protoplasm — pseudopodia ; and later the whole mass flows into one or more of these projections, thus changing its position and its shape. This ameboid movement takes place in the white l)lood-corpuscle, and in some other cells as well as in the ameba. The pseudopodia are frequently drawn hack into the protoplasm, or retract, thus illustrating the posses- sion by the protoplasm of contractility. Their formation is due to an outflowing of the hyaloplasm, and their retraction to return of the hyaloplasm to the interstices of the reticulum." Ameboid movement is said to be spontaneous ; but if so, it can also be pro- duced by the action of heat, by dilute solutions of salt, by mod- erate currents of electricity, and by many other agents, all of ■which are called stimuli, because of their power to stimulate this movement. On the other hand, certain agents have the power of stopping or inhil)iting the movement if it has begun. Thus a temperature above 40'^ C. or below 0° C. acts as an inhibitant, Avhile if the high temperature is continued the protoplasm is coag- CJbJM'llUiiOME. 25 iilatod and its life destroyed. Acids and strong alkalies have the power of destroying the movement altogether, while chloroform inhil)its it ti'mporarily. This property of responding to a stinndiis is known as irrit(ibi/ifi/,i\ud the fact that a stimulns a])plied to (»ne part of a mass of protoplasm will produce results in other and distant parts demonstrates the presence of co)idactlviti/. Nutrition. — Another property possessed by living protoplasm is that of nutrition ; by which is meant the power to absorb mate- rial, to convert it into protoplasm, and to get rid of such waste products as have served their purpose or are formed as a result of the activity of the protoplasm. Tliat portion of the process which is concerned iu the building up of the protoplasm is assimilation or anaboUsm, while that concerned with its breaking down or destruction is dis(i'^situi/afio)i or katabolism. A fourth property of protoplasm is that of reprodudion, which will be treated of under the heading Division of Cells. Nucleus. — Eml)edded in the protoplasm is a vesicle of various shapes — spherical, oval, or irregular — which is to be regarded as of great importance, especially in the process of cell-subdivision by which new cells are formed and growth thus brought about. It consists of an external enveloping membrane, the nuclear membrane, enclosing the chromoplasm or intranuclear network, a material resembling spongioplasm, and in the interstices of this is the nuclear matrix. In addition to these there are micleoli, some of which are thickenings of the network like the knots in the spongioplasm, and are called pseudonucleoli, while others are free, the latter being the nucleoli proper, or the true nucleoli. A single true nucleolus is usually found, although this is not always the case. Chromatin and Achromatin. — AVhen cells are stained with hema- toxylin the nuclear membrane, the chromoplasm, and the nucleoli take up the staining-fluid readily, while the nuclear matrix does not ; hence the former are said to be made up of chromatin, or to be chromatic ; while the latter is achromatin, or is said to be achro- matic. Other dyes, such as safranin, methyl-green, and carmine, produce the same effect. Chromatin is but another name for nuclein, which is the principal constituent of the nucleus. It is closely allied to the proteids, but is characterized by containing a consideral)le percentage of phosphorus ; some analyses give as much as 8 per cent. Nuclein is a compound of nucleic acid with proteids, and it is to the affinity of this acid for the coloring- matter that the staining of chromatin is due. It is more correct to speak of nucleins rather than of a single substance, as the compo- sition of nuclein is not always the same. For a further discussion of this subject the reader is referred to the chapter dealing with Proteids. Centrosome. — As already stated, this is probably to be regarded 26 CELLS. -Centrosome. Centrosphere. Chromosomes. "Centrosome. Fig. Fig Fig. Figs. 2-7.— Diagrammatic representation of the processes of mitotic cell- and nuclear division (Bohm and Davidoflf ). Figs. 2-4, Prophases : Figs. 6. 7, metaphases. Fig 2 Eesting nucleus : Fig. 3, coarse skein or spirem : Fig. 4, hne sfcein or spirem ■ Fig. 5, segmentation of the spirem into single chromosomes ; Fig. 6, longi- tudinal" division of the chromosomes ; Fig. 7, bipolar arrangement of the separated chromosomes. DIVISKJN OF CELLS. 27 Fig. 8. Fig. 9. — Chromo- somes. Fig. V2. Figs. 8-12. — Diagrammatie representation of the processes of mitotic cell- and nuclear division (Bohm and Davidoflf). Figs. 8-11. Anaphases ; Fig. 12, telophases. Fig. 8, wandering of the chromosomes toward the poles; FiG. 9, diaster; Figs. 10 and 11, formation of the dispirem ; Fig. 12, two daughter-cells with resting nuclei. To simplify the figures 5-10, we have sketched in only a few chromosomes. In Fig. 9 it is seen that the cell-body is also beginning to divide. 28 CELLS. as an essential element of the cell, inasmuch as the more the sub- ject is investigated the more frequently is this structure found. It is also known by the name of aUraction-partide. Radiating from it as a center are fine fibers, which together with it constitute the centrosphere (Fig. 2). Usually there are two of these spheres in a cell ; especially is this the case Avhen the cell is about to divide, and they are connected by fibers forming an achromutie or- central spindle. Division of Cells. — Cells divide and then multiply in two ways : 1. By direct division ; 2. By indirect division. Direct Division of Cells. — This may be either by gemmation or by fission. In the former a portion of the nucleus and proto- plasm forms a bud-like projection from the parent cell, from which it subsequently separates. The bud develops into a cell similar in all respects to that from which it had its origin. In Jission the original nucleus divides into two, and then the protoplasm divides in such manner tiiat each half shall possess its own nucleus, and two new cells are thus produced. Direct division is, however, not the method by which cells, as a rule, reproduce their kind ; indeed, it is regarded as very infrequent. Indirect Division, Karyokinesis, Karyomitosis, Mitosis (Figs. 2-17). — It is to this method of division that we must look for the com- prehension of the processes by which the tissues produce and re- produce themselves. It has been studied in them all — epithelial, connective, muscular, and nervous. While in direct division the nucleus divides into two equal halves, in karyokinesis the changes which take place in the nucleus are complicated, and it is only after a long series that new cells are produced. The statement is made by some authors that the division of a cell is preceded by the division of its attraction-sphere, and that the division of the nucleus follows ; indeed, some regard the change taking place in the attraction-sphere as determining or causing the division of the nucleus ; but inasmuch as instances have been observed in which the nuclear changes preceded, they are evidently not under all circumstances dependent upon the influence of the attraction-sphere. The changes which take place in the process of karyokinesis may be concisely described as follows : Prior to the beginning of the process the cell consists of protoplasm containing a nucleus, with one or more contained nucleoli, and enclosed by the nuclear membrane, and a centrosome and attraction-sphere. A close ex- amination of the chromoplasm of the nucleus shows it to be made up of some fibers which form loops at the ends or poles of tlie nucleus, and are the primary loops, while others less prominent and which help to give to the chromoplasm its reticular or net- work form are secondary fibers. When indirect division begins the first change usually, though INDIRECT DIVISION. 29 not always, consists in the division of the centrosome and of the attraction-sphere into two ; then the following changes take place in the nuclens : The nncleoli and the secondary fibers disappear, while the primary loops remain as chromosomes. These latter become less twisted, forming a sjjireia or skein, and split into two sets, forming a dis^jirem or double skein, thus doubling the number ,:^r1f?0WW- Fig, 13. Fig. 14. Fig. 15. Fig. 16. Fig. 17. Figs. 13-17. — Mitotic cell-division of fertilized wbitefish eggs — Coregonus albus (Huber). Fig. 13. Cell with resting nucleus, centrosome, and centrosphere to the right of the nucleus; Fig. 14, cell with two centrospheres, with polar rays at opposite poles of nucleus; Fig. 15, spirem ; Fig. 16, monaster; Fig. 17, metakinesis stage. of chromosomes (Fig. 10, 11). The number of chromosomes is subject to considerable variation in different animal cells. In some, four have been seen, in others as many as twenty-four. The achromatic spind/e (Fig. 6) now appears. This consists of a spindle-shaped structure, at each end of which is a centro- some, the two having been formed from the original centrosome of the cell. These are connected by achromatin fibers — i. e., fibers which are not colored by the staining-material used in the study 30 EPITHELIAL TISSUE. of the karyokinetic i)rocess. Whether these fibers are formed from the attraction-sphere or from tlie achromatin of the nucleus is unknown. Each of these centrosomes forms a pole of the spindle. The nuclear membrane now disappears, and there is nothing between the protoplasm of the cell and the nuclear matrix. The protoplasm in contact with the nucleus is clear, while that outside of this clear space is granular. In some cells these gran- ules have the appearance of fine fibers radiating from the centro- somes or poles, and constitute the amphiaster. The next stage is characterized by the settling of the chromo- somes to the equator of the spindle, where they form a star or aster, which being single is called )noiuister : this is known as the equatorial stage. The chromosomes now separate so as to form two distinct groups, constituting the stage of metakinesis. One group passes to one end or pole and the other to the other, thus forming a star at each end and giving rise to the term diaster or double star. This passage of the chromosome from the equator to the poles is believed to be accomplished by the contraction of the achromatin fibers of the spindle. Thus from the chromoplasm of the nucleus two new nuclei, or daughter-nuclei, are formed, each aster passing into a resting nucleus by a process the reverse of that by which it was fi)rmed, through the dispirem stage. A nuclear membrane forms around each new nucleus, and the protoplasm of the original cell subdivides into two, each half enclosing a new nucleus : at the same time the spindle disappears. ELEMENTARY TISSUES. EPITHELIAL TISSUE. Distributed over the surface of the body, lining its many cavities and canals, and in the ducts of glands, epithelium is found of several varieties and arrangement. The varieties are as follows: Pavement or scaly, cubical, columnar, goblet-cell, spheroidal or glandular, and ciliated. Pavement or Scaly Epithelium (Fig. 18). — As its name imjilies, the cells of this variety of epithelium are thin and flat, and are arranged like the stones of a pavement. They are bound together by a small amount of cement-substance. They are fi)und in the lung-alveoli, in the ducts of the mammary glands, and in the kidney in the tubes of Henle, and lining Bowman's capsules. These cells are also found covering serous membranes, as the peri- cardium, and lining blood-vessels and lymphatics, and in that case receive the name of endothelium. Cubical Epithelium. — This kind of epithelium is of a COLUMNAR EPITHELIUM. 31 cubical shaj>e, and occurs iu the tubulos of the testis aud in the alveoli ot" the thyroid iiland. Fig. 18. — Isolated cells of squamous epithelium (surface cells of the stratified squamous epithelium lining the mouth): a, a, cells presenting under surface; 6, cell with two nuclei (Huber). Columnar Bpithelium (Fig. 20). — Columnar ej^itlieliura is sometimes described as ciflindrie epithelium. The cells are of a prismatic shape, and usually rest upon a basement-membrane, ^\'hen looked at from the free end, they present the appearance of a mosaic ; when ob- served from the side, the free edge is seen to be striated. This variety of epithelium lines the stomach and intestines, and the glands which open into these cavi- ties. It covers the mucous mem- brane of most of the urethra, the vas ^ig. 19 -Surface view of squa- - p ^ > 1 1 mous epithelium from skin of a deferens, prostate, Cowper s glands, frog ; x 400 (Bohm and Davidoflf). and the ducts of most glands. The germinal epilJiflimn which covers the ovary is of this type. Goblet-cell (Fig. 22). — A peculiar modification of columnar Goblet-cell. Ciiticular border. Fig. 20. — Simple columnar epithelium from the small intestine of man : a, isolated cells ; 6, surface view ; c, longitudinal section (Huber). 32 EPITHELIAL TISSUE. epithelium is seen in the (jobkt-ccU. This occurs in the intestine, for example ; the mucin, which is the product of the cell, distends the upper part of it, and the cell bursts (Fig. 22). The mucin is discharged as mucus, and the open, cup-like end of the cell gives to it the peculiar appearance characteristic of the goblet-cell. Goblet-cell. -Cilia. Fig. 21. — Cross-section of stratified ciliated columnar epithelium from the trachea of a rabbit (Huber). Formerly regarded as a simple modification of the columnar cell, these goblet-cells are probably more properly to be considered as a special kind of epithelium which is of a permanent nature, and whose function is to secrete mucus ; hence they are sometimes called mucus-secretliK/ ccUs. Spheroidal or Glandular Epithelium. — This is charac- terized by its polyhedral or spheroidal shape, and occurs in secreting Cilia. Mucin. Nucleus Basal process - Fig. 22.— Goblct-cclls from the bronchus of a dog: the middle cell still pos- sesses its cilia : that to the right has already emptied its mucous contents (collapsed goblet-cell) ; X 600 (Bohm and Davidoff). glands; as, the .salivary glands, liver, and pancreas. The secretion of these glands is the ]>roduct of the protoplasm of the glandular epitlielium. Ciliated Epithelium (Fig. 23). — The characteristic of this variety is the cilia or hair-like or eyelash-like appendages attached C'JIJMIY MOTION. 33 ['ilia. - Nucleus. Fig. 23.— Ciliated cells from the bron- chus of the dog, the left cell with two nuclei ; X 600 ( Bohm and Davidott'j. to tlio tVco surfaco of tlu- cells. Tlic cells wiiicli bear the cilia are iisiinlly of the columnar variety. Ciliated e])itheliuni covers the mucous membrane of the respir- atory tract, which bctrins with the nose and ends in the alveoli of the liniir, witli tiie followino; exceptions: The olfactory membrane (that part of the mucous mem- brane of the nose to which the olfactory nerves are distributed), the lower part of the pharynx, the surface of the vocal cords, the idtimate bronchi, and the luntr-alveoli. It covers also tile mucous meml)rane of tiie tympanum, except the roof, promontory, o.ssicles, and mem- brana tympani, where the epi- thelium is of the pavement variety and non-ciliated. Cil- iated epithelium occurs also in the £;ustachian tube, the Fal- lopian tube, the cavity of the body of the uterus and of the upper two-thirds of the cervix, the vasa eiferentia and coni va.sculosi of the testicle, the ventricles of the brain, and the central canal of the spinal cord. Some observers have seen ciliated epithelium in the convoluted tubules of the kidney. Ciliary Motion. — Cilia are composed of protoplasm, and, like other protoplasm, have the power of motion ; but ciliary motion, though in some respects like that known as ameboid, is in other respects quite different. Instead of being slow, it is very rapid — ten times and more a second — so much so that when active, the individual cilia which produce it are indistinguishable. It has been likened to the movement of a field of wheat over which a breeze is passing. The effect of this movement is to produce a current always in one direction, and this current is often of con- siderable physiologic imjxjrtance : thus it is to its influence that the ovum is carried down the Fallopian tube in the human female ; and, according to some authors, were it not for the ciliated epithe- lium in this canal the ovum would not find its way into the tube, l)Ut at the time it escapes from the ovary would fall into the peritoneal cavity and degenerate. Various explanations have been given to account for ciliary motion. One which seems reasonable is that it is due to the same cause which produces ameboid movement, namely, the flow of the hyaloplasm into and out of the spongioplasm. It is a well-known fact that if cilia are severed from the cells of which they form a part, this motion cea.ses, so that intimate connection with the 3 34 CONNECTIVE TISSUE. cells is essential. The protoplasm composing the cilia being thus in direct communication with that of the epithelium, being in fact a prolongation of it, the hyalo})lasm can flow in and out witiiout hindrance ; the inflow causing tliem to straighten, the outflow causing them to resume their m'iginal condition, which is curved ; this rapid inflow and outflow produce the characteristic motion. External agencies affect this motion as they do that of other protoplasm. Chloroform inhibits it, as do temperatures above 40° C. or below 0° C. ; while dilute alkalies favor it. Simple Bpithelium. — ^Mien epithelium of either of these varieties is arranged in a single layer it is known as simple epi- thelium. Stratified Bpithelium (Fig. 21). — When the epithelial cells are arranged in many layers they form stratified epithelium, the cells of each layer differing in shape. Thus in the epidermis, the epithelium of which is of this variety, the deepest layer is columnar in character ; next to this is a granular layer of spindle-shaped cells ; then one of closely packed cells ; and, most superficial of all, are several layers of dry, horny scales. Stratified epithelium is also found covering the mucous mem- brane of the mouth, the lower part of the pharynx, the esophagus, vagina, and outer third of the cavity of the cervix uteri, and the conjunctiva. Transitional Bpithelium. — This term is applied to epithe- lium which is arranged in a few layers — two, three, or four. The line of demarcation between stratified and transitional epithelium is not very distinct. This variety exists in the ureters and bladder in three layers. The inner layer is composed of cuboidal cells, the next of pear-shaped cells, between the lower elongated ends of which is a third layer of small cells. The hair, the nails, and the enamel of the teeth are of an epithelial nature, though in a much modified form. Epithelium is nourished by lymph, and with few rare exce})tions is not sup- plied with nerves : such exceptions are the epithelium covering the cornea and that in the deep layers of the epidermis. CONNECTIVE TISSUE. The term ''connective" as applied to this large group of tissues implies that they are concerned in binding the body together into one organic whole, without which the tissues would be disconnected and the body lack the support which these structures afford. The following are the varieties : 1. Areolar; 2. Adipose ; 3. Retiform ; 4. Lymphoid ; 5. Elastic ; 6. Fibrous ; 7. Jelly-like ; 8. Cartilage ; 9. Bone; 10. Dentin, Areolar Tissue. — Areolar tissue consists of bundles of fibers presenting a wavy aj^pearance (Fig. 24) running in various direc- ADIPOSE TISSUE. 35 tions, together with ohistit- fibers (Fig. 25) which do not form bundles and are not wavv, Tlieso fibers are bound together bv a cenienting-nuiterial or ground-substance. The irregular crossing of the fibers leaves spaces, called areoUe, which give the name to the tissue. In these are connective-tissue cells or corjniscles, of which there are several varieties, the protoplasm of which pro- duces the fibers and the ground-substance. These varieties are : Fig. 24. — Cell-spaces in the ground-sub- stance of areolar connective tissue (subcu- taneous) of a young rat; stained in silver nitrate (Huber). Fig. 25. — Elastic fibers from the ligamentum nuchseof the ox, teased fresh ; X 500. At a the fiber is curved in a characteristic manner (Bohm and Davidoif ). 1. Lamellar cells; 2. Plasma-cells of AValdeyer; 3. Granule-cells. Lymph-corpuscles are not infrequently seen, and in some places, as in the choroid coat of the eye, the corpuscles contain coloring- matter or pigment. Areolar tissue occurs under the skin as subcutaneous ti.ssue, beneath serous membranes as subserous, and beneath mucous mem- Nucleus. Protoplasm. Fat-drop. Cell-membrane. Fig. 26.— Scheme of a fat-cell (Bohm and Davidoff). branes as submucous, connecting these membranes loosely to the structures upon which they lie. Enclosing muscle, blood-vessels, and nerves, it forms their sheaths. It is also found in glands con- necting the various jxirts with one another. Adipose Tissue (Fig. 27). — AVhen the areolre of areolar tissue contain fat-cells, the tissue is called adipose. These fat- cells or adipose vesicles consist of an envelope or sac, protoplasmic 36 CONNECTIVE TISSUE. in character, within which is the fat in a fluid form. The tem- perature of the body during life is believed to keep this fat fluid ; >^. Fig. 27. — Adipose tissue (Leroy ; : a, fibrous tissue ; 6, fat-cells ; c, nucleus of fat-cells ; d, fatty acid crystals in fat-cells. but after death, when the temperature falls, the fat becomes solid. Free adipose vesicles would doubtless assume a spheroidal *tv^ »# -1( , &^ .^r O* «>'G >^. . s# #^ ■^. €'■ -di?. Reticulum. Nucleus of cunnuc- tive-tissue cell. Blood- vessel. Fig. 28. — Eeticular connective tissue from lymph-gland of man ; Brush prepara- tion (Bohm and Davidoffj. shape, but by compression, either of contiguous vesicles or other structures, they assume various shapes, oval or polyhedral. ELASTIC TISSUE. 37 Adipose tissue is widely tlistribiiti'd through the body ; indeed, it is an exception to find areohir tissue without some fat in its areohe. The {)rineipal exceptions arc the areolar tissue beneath the skin of tiie eyelids^ the penis, the scrotum, and the hibia minora. There is also no adipose tissue within the cranium, in the liver, or in the lunt^, except near its root. It is to be understood that this statement does not apply to fat, but to adipose tissue, which is characterized by the fact that the fat is enclosed in a protoplasmic envelope. The fat is formed from the protoplasmic connective-tissue corpuscles, the cell-wall of whicii forms the wall of the vesicle. The nucleus of the cell remains, althouuh it is not always readily discernible. Retifortn Tissue (Fig. 28). — This may be defined as areolar tissue whose oround-substance is fluid, and in which but few, if anv, elastic fibers exist, and the white fibers form a close network. Authorities differ as to the identity of the white fibers of areolar and those of retiform tissue ; some claim that their different be- havior to certain reagents demonstrates them not to be the same. Retiform tissue exists in mucous membranes. I/ymphoid Tissue. — When the areolae of retiform tissue contain lymph-eorpuseles, which will be described in connection with the blood, the tis- sue is li/mphoid or ade- noid. It is found in lym- phatic glands, the thy- mus gland, the tonsils, solitary glands, patches of Peyer, and Malpigh- ian corpuscles of the spleen. Blastic Tissue (Fig. 25). — This tissue is composed of fibers or meml)ranes which are characterized by their elasticity and a yellow color. By elasticity is defined "that property of matter by virtue of which a body tends to return to a former or normal size, shape, or attitude, after being de- flected or disturbed." The tissue exists in the ligamenta subflava of the vertel)r?e, the vocal cords, between the cartilages of the larynx, in the longitudinal coat of the bronchi, the lungs, the middle coat of the larger arteries (such as the aorta and caro- Teudon-cell. -A — Teudon-fibers. Fig. 29.— Longitudinal section of tendon ; X 270 (Bohm and Davidoff). 38 CONNECTIVE TISSUE. tids), and in the stylohyoid, thyrohyoid, aud cricothyroid liga- ments. Fibrous Tissue (Fig. 29). — By reason of its color this kind of tissue is also called white Jibrous tissue. It is made up of white and glistening non-elastic fibers, which give to it great strength. It is widely distributed, occurring in ligaments, tendons, muscular fascia, periosteum, perichondrium, pericardium, and dura mater, sclerotic coat of the eye, tunica albuginea of the testis, capsule of the kidney, epineurium, and the sheaths of the corpora cavernosa and corpus spongiosum of the penis. In the ligaments and tendons the fibers are arranged in bundles, between which are many flat connective-tissue corpuscles, the tendon-cells (Fig. 29). Matrix 1^ Cartilage- cell. m- (£a^ l> .Fig. 30.— Hyaline cartilage (costal cartilage of the ox); alcohol preparation; X 300 (Bohm and Davidoff ). The cells are inclosed in their capsules. In the figure a are represented fre(juent but by no means characteristic radiate structures. Jelly-like Connective Tissue. — This consists of a soft matrix, with a few spheroidal cells and a few fibers. It is found in the embryo, as in the jelly of Wharton in the umbilical cord. The only structure in the adult made of this material is the vitreous humor of the eye. It consists chemically of water and mucinogen, with a small amoimt of proteid and salts. Cartilage. — This tissue exi.sts in the human body in several varieties ; a. Hyaline ; 6. White fibrous ; c. Yellow ela.stic ; d. Cellular. Hyaline Cartilage (Fig. 30). — This variety is sometimes called tnie cartilage. It varies in structure according to the location in which it occurs, and by reason of this its location receives different names : articular and costal. CARTILAGE. 39 Artlcnl<(r Cartildyc (Fig. -31). — Tlic cartilagv-eells oftliis vari- ety are usually arranged in small groups in a groimd-suhstance or vKtirix, which is clear except when examined under a high power of the microscope, when it aiijx'ars granular. In this matrix there arc no fibers except at the edges, where some fibers may be found and where the cells are branched. At the edges the cartilage is in White fibrous con- , nective tissue. W-L' , White fibrocarti- lage. ^/^ /%: 'J Insertion of liga- mentum teres. ■ Hyaline cartilage. Fig. 31. — Insertion of the ligamentum teres into the head of the femur; longi- tudinal section; X 650 (Bohm and Davidoflf). communication with the synorial membrane (Fig. 31), and the cells of the cartilage are branched and resemble the branched cells of the connective tissue of the synovial membrane, from Avhich fact thev give to the cartilage the name transitioned. Although hyaline cartilage is described as having a matrix free from fibers, still, under proper treatment, a fibrous character can be made out. Articular cartilage covers the ends of bones in the joints 40 CONNECT I VE TISSUE. Fig. 31), where it serves the chnible purpose of reducing coucussion by virtue of its elasticity, and of forming a smooth surface for the motion of the joint. It has no blood-vessels, but is nourished from both the synovial membrane and the bone. It does not ossify — that is, become bone. Costal CaiiUwje (Fig. 30). — Cartilage of this kind is hyaline, though in old age a fibrous character is observed. Its individual cells are larger, and the groups of them are larger than in articular cartilage. Its tendency to ossify is anotiier difference when com- pared Avith the articular variety. OsHificatioii and calcification must be very oarefullv distinguished. In the former a formation -Cartilage-cell. ---Elastic fibers. Fig. 32. — Elastic cartilage from the external ear of man : a, fine elastic network in the immediate neighborhood of a capsule ; ^ 760 (Bohm and Davidotf). of bone occurs ; in the latter there is simply a deposition of lime .salts. Costal cartilage is found in connection with the ril)s, and also in the larynx, excepting in those minute structures, the cornicula kiryngis or the cartilages of Santorini. It also forms the carti- laginous structure in the trachea, the nose, and the external audi- tory meatus. White Fibrous Cartilage or Fibrocartilage (Fig. 31). — White fibrous connective tissue, with cartilage-cells between the bundles, characterizes this tissue. It is described as of four kinds, principally by reason of the office it serves ; interaHicular, flat plates between BOSK. 41 tlic articular cartilages of some joints, as the knee and the wrist ; connecting, as between the bodies of the vertebrae; circumferaitial, as in the cotyloitl cavity of the hip-joint, which it makes deeper ; anil fifnififonn, where it lines i^rooves in bone thronji:!! which tendons ]kiss. It also occurs in some tendons, as in that of tiie peroneus lonu'us. Yellow Elastic Cartilage (Fig. 32). — The presence of elastic libers in tiie niiitrix is the distinguishing feature of tiiis variety of cartilage, which is found in the pinna of the ear, the Eustachian tube, the epiglottis, and the cornicula laryngis. Cellular Cartilage. — This kind is made up almost wholly of cells ; sometimes fine fibers are present. The only structure in which it is found in the human body is the cJiorda dorsa/is or notuchord of the embryo. Chemical Composition of Cartilage. — The following analyses were made by Hoppe-Seyler, and represent parts per 1000 : Costal Cartilage. Articular Cartilage. Water 676.6 735.9 Solids, organic 301.3 248.7 Solids, inorganic 22.0 15 .4 999.9 1000.0 Organic Solids of Cartilage. — The cells contain, besides the proteid contents of cells generally, fat and glycogen. The matrix contains chondrigen, which on boiling yields chondrin. This is the generally accepted theory as to cartilage, but the most recent analvses seem to show that chondrin is not a simple substance, but a mixture, and that in the matrix are four sul)Stances : 1. Col- lagen; 2. An alburninoid, which exists only in later adult life, and is like elastin, but contains more sulphur ; 3. Chondroraucoid ; and 4. Chondroit in-sulphuric acid. Inorganic Solids of Cartilage. — Potassium and sodium sul- phates, sodium chlorid, and sodium, calcium, and magnesium phosphates represent the inorganic class of physiologic ingredients of cartilage. Perichondrium. — This is a fibrous membrane which envelops cartilage except at the articular ends of bones : it contains blood- vessels, which as.sist in nourishing the cartilage. Bone. — There are two varieties of bone : compact and can- cellous or cancellated. The former is firm and dense, and occurs on the exterior of bones ; the latter is spongy and more open in structure, and occupies the interior. The differences between the two are not such as to justify their being regarded as two distinct varieties, for in all es.«ential points they are identical. Practically, however, it seems wise to describe them separately. When a cross-section of a bone is examined under the microscope (Fig. .33) Haversian cancds are .seen, averaging O.Oo mm. in diameter : 42 COyyECTI ] 'E TI&S UE. arouml these the boue is arranged in rings, lamellce ; between these are spaces, lacume, in which are bone-corpuscles (Fig. 34). Each canal is connected with the lacuna which are concentric Outer circum- ferential lamellse. ■^v^.. • -O^ It .4^: Haversian or ~= — concentric lamellae. lameiia. Fig 33 —Segment of a transversely ground section from the shaft of a long bone, showing all the lamellar .systems; metacarpus of man: X 06 (Bohm and Davidoff). with it. and the lacunje with one another by means of fine canals, connUoidi, into which project proQCSses of the bone-corpu.•%. Fig. 35. — From a section through human red bone-marrow : a, /, normoblasts ", 6, reticulum ; c, mitosis in giant cell ; rf, giant cell ; e, h, myelocytes ; g, mitosis ; t, space containing fat-cells; X680 (Bohm and Davidotf). carbonate, chlorid, and fluorid ; magnesium phosphate, sodium chlorid, and some sulphates. Of the.se inorganic constituents, calcium phosphate exists to the amount of 83.88 per cent., and calcium carl)onate to the amount of 13 per cent. Development of Bone. — O.^ffification, the process by which bone is formed, occurs in two forms : intramcmbranous and intracarti- Uif/inous or endochondrdl. The subperiosteal variety described by some authors is, in all essential particulars, identical with the intramembranous. By the intrameml)ranous are formed the parietal, frontal, and upper portions of the tabular surface of the 46 CONNECTIVE TISSUE. occipital bone ; while by the intracartilaginous, the humerus, femur, and other long bones are formed. Intramembranous Ossification (Fig. 37). — This process may be studied in the parietal bone, which, prior to the beginning of ossification, about the seventh or eighth week of fetal life, is a fibrous membrane containing blood-vessels and osteoblasts (Fig. 37). The process begins in the center of ossification, which, in the parietal bone, is single, at the parietal eminence. The number of these centers varies in different bones ; in the frontal there are two. The embryonic membrane is composed of bundles of fibers, osteogenic fibers, with a granular matrix between them. Both the ^ ^^^sm^ ;^ci' Fig. 36. — Cover-glass preparation from the bone-marrow of dog ; X 1200 (from preparation of H. F. Miiller) (Bohm and Davidoff ) : a, mast-cell; i, lymphocyte; c, eosinophile cell ; d, red blood-cell ; e, erythroblast in process of division ; /, /, nor- moblast ; g, erythroblast. Myelocyte not shown in this figure. fibers and the matrix become calcified by the deposition in them of lime salts, and there is produced in them a calcareous mass enclosing blood-vessels and osteoblasts, which latter become bone- corpuscles, and the spaces in which they lie form the lacunae. The blood-vessels permeate the whole, the channels which they form being Haversian canals. It will be observed that in this variety of ossification a membranous structure precedes the bone ; hence the bone is said to he formed iii membrane. Intracarfi/ar/inous or Endochondral Ossification (Fig. 37). — In this form cartilage precedes the bone, and the changes which result in bone-formation take place within it and practically convert it into bone. First Stage. — In the first stage the cartilage-cells at the center Connective tissue. BONE. Outer fibrous liiyer of periosteum. Osteoblasts Marrow space. Blood-ves sel. Osteoblast Remnants ot cartilage- matrix. Bone-celh Osteoblasts Fig. 37. — From a cross-section of a shaft (tibia of a sheep) ; X 550 (Bohm and Davidoff ) : in the lower part of the figure is endochondral bone-formation (the black cords are the remains of the cartilaginous matrix) ; in the upper portion is bone developed from the periosteum. of ossification become larger and arranged in rows ; in the matrix or gronnd-substance, between these rows of cells, lime salts are deposited in .snch manner as to form longitudinal rows of cells, separated by the calcified matrix ; in the matrix, between 48 COySFXTIVE TISSUE. adjacent cells, at right angles to these calcareous columns, lime salts are also de]X)sitefl, thus forming spaces containing cartilage- cells, the boundaries of which are composed of the calcified matrix. These spaces or cavities are primrrry areokr-. AVhile this process is taking place at the center of the cartilage, beneath the mem- brane which envelops the cartilage, the perichondrium, or, as it is subsequently called, the periosteum, the osteoblasts form fibrous .Vesicular cartilage- cells. Primary periosteal bone-lamella. Periosteal bud. Periosteum. Unaltered hyaline cartilage Fig. 3S. — Longitudinal section through a long bone 'phalanx') of a lizard embryo (Bohm and DavidoflFi. The primary bone-lamella originating from the periosteum is broken through by the periosteal bud. Connected with the bud is a periosteal blood-vessel containing red blood-corpuscles. lamellae on the surface of the bone, which become calcified by the deposit in them of lime .salts. Some osteoblasts are clo.sed in by the lamella and become bone-corpuscles. These changes which take place on the surface beneath the periosteum constitute sub- periosteal or intramembranous ossification, which has already been described ; thus, both kinds of ossification take place in the long bones. BONE. 49 Second Stage or Stayc of Jrraption. — In this stage the hlood- vessels and osteoblasts of the periosteum form processes which al)S()rl) portions of the bone recently made by intramenibranous ossilication, and of the walls of the primary areohe, thus Dro- ducing larger spaces or cavities, .wc- ondart/ (urolce or mcdalUiry spaces; these contain osteol)lasts and blood- vessels, which constitute embryonic marrow. Authorities differ as to the ultimate fate of the cartilage-cells; some think they become osteoblasts, while others teach that they are ab- sorbed. Third Stage. — The osteoblasts of the embryonic matrix, increased In num- ber by division, form a layer of bone on the surfaces of the walls of the secondary areola?. On this bony wall another layer of osteoblasts forms a second layer of bone, and thus the process continues until only a small canal remains, the Haversian canal. The layers of bone, produced in the manner described, are the lamellae ; while such of the osteoblasts as remain between the lamelhe become the bone- corpuscles. No satisfactory explanation has been given of the method of pro- duction of the canaliculi. During this stage the process of ossification which began in the center of the bone extends toward the extremities, and thus the en- tire shaft becomes ossified. Histologists describe the multinucleated cells (sim- iliar to the myeloplaxes of the marrow) which are concerned in the absorption of the calcified matrix and bone under the name osteoclasts, reserving the term osteoblasts for the cells which form the bone. The shaft of the bone and its ex- tremities remain separated for a period of time which varies in different bones, and increase in length takes place by a growth of cartilage between the shaft and its epiphyses. This intermediate cartilage later ossi- fies, and the union of shaft and extremities is complete. Cartilagi- nous at first like the shaft, the epiphyses undergo ossification in Fig. 39. — Longitudinal sec- tion through area of ossifica- tion from long bone of human embryo (Huber). 50 CONNECTIVE TISSUE. 'Enamel. Pulp-cavity. the same manner. The bone becomes of greater circumference by the deposits made by the periosteum externally, and the medul- lary canal is made larger by the absorption of a portion of its walls. In the re})air of bones, as after fractures, the j)eriosteum performs the same office as in the original formation of bone. Dentin. — The con- sideration of this sub- stance calls for a de- scription of the teeth, of which it forms an important part. A tooth (Fig. 40) is divided anatomically into the crown, the vis- ible portion, which pro- jects above the gum ; the rooty the portion out of sight within the alveolus or socket ; and the neck, the constricted portion joining tlie crown and the root. In the center of the crown and extending into the roots is the pulp-chamber , the openings of which, at the tip of the roots, are apical foramina, through which pass b 1 o o d-v e s s e 1 s and nerves into the pulp- chamber, which con- tains dental pulp. This latter is com- posed of a gelatinous connective tissue with branched cells, to- gether with the blood- vessels and nerves just mentioned ; lymphatic vessels are absent. Some of the cells are in contact with the dentin of the tooth, and having been concerned in its formation are called deniin-forming cells or odoniohlasts. The solid part of a tooth, excluding the pulp-chamber and its Dentin. . r'omentum. Fig. 40. — Scheme of a longitudinal section through a human tooth ; in the enamel are seen the "lines of Eetzius" (Bohm and Davidoflf). ni'jyTiN. -51 contonts, is made up of (Iciidii or ivory, enamel, and cement or cnit^td jH-trosa. Jhiiii)!. — The uuiin portion of a tooth is composed of dentin, whieii forms the walls of the pulp-eiiamber. It bears some resem- blance to bone, thongh the Haversian canals and lacunae, which characterize the latter, are not jn-esent ; it is, however, regarded as modified bone. Chemically it consists of 10 per cent, water and 90 ]>er cent, solids, of which latter 27.70 per cent, is organic, collagen and elastin, and 72.30 per cent, inorganic. Of this, calcium carbonate and phosphate form 72 per cent., and magne- sium phosphate and calcium tiuorid the rest. Microscopically, dentin is made up of dentinal tubuli, hollow tubes, which present a wavy appearance, between which is inter- tubular tissue. In general, the tubules are parallel with one Cementum. < >- 1^- Dentin. Fig. 41. — Cross-section of human tooth, showing cement and dentin ; X 212 (Bohm and Davidofl'). At a are seen small interglobular spaces (Tomes' granular layer). another, although in the upper part of the crown they are arranged vertically, Avhile in the neck and root they are oblique. They extend from the enamel and cement to the pulp-chamber, into' which they open, and from the odontoblasts of which they receive processes ; the dentin thus resembling bone in which bone- corpuscles send processes into the canaliculi. At the ends, Mliich open into the pulp-chamber, the tubules are unbranched, but as- they extend toward the enamel and cement they divide dicho- tonlously — i. e., into two branches, each of which again divides in the same manner. They terminate beneath the enamel and cement in irregular communicating spaces, interglobular spaces or the granular layer. The intertubular tissue contains the greater portion of the inorganic constituents of the dentin. Fig. 42. Fig. 43. S^S?V/-', ;■.-.. -fci^.^^ '^^^>>^^S^ Fig. 44. i^. 'I-^- "i:*-- - i-.' ■ -T,-l_-^i.-^i.X».. ,.8 y. Fi«+. 45. FTP": 4''-45 —Four stages in the development of a tooth in a sheep embryo (from'^Se'lower S Sm and Davidoff f. Fig. 42. anlage of tje -ame -.erm connected with the oral epithelium by the enamel-edge ■. Fig. ^^ -^fsttrace ( t he dentinal papilla: Fig. 44. advanced stage with larger papilla and differentianng onamd P^p Fig 4.5 buddine from the enamel-edge of the anlage of the enamel geXUiih latL goes to form the enamel of a permanent tooth ; at tbe peripheY of the papilla the odontoblasts are beginning to differeiit.ate Fig>^42, J'^. f ^ «, V 110- Fig 45 ^ 40. a. a. a. a. Epithelium of the oral cavity ■ h b. b. b. "^ ^a^ layer" c c e the superficial cells of the enamel-organ; .1 ,1. d ^'•enamel-pulp ««; dentinal papilla : ... s. enamel-forming elements (enamel-cells) : oodont<^ Wafts'^' .Senamel?Jrm of the permanent tooth; r, part of the enamel-edge ol a temporary tooth ; h, surrounding connective tissue. 52 DENTIN. 53 J'JiHiiiu'l. — This covers the crown uikI extends to the root. It is the lianlest part of a tootli — indeed, it is the hardest tissue in the human l)ody — and ])rolects the softer and more sensitive portion hencath in the [)rocess of mastication or che\vin<^. It is made up of eh)n>::itt(l hexai^onal prisms, outnu'l-prianis, which are placed at right angles to the dentin (Fig. 4G). Chemical analyses of enamel vary to a considerable extent. Hoppe-Seyler gives the following : Calcium carbonate and phos- phate, 96 per cent. ; magnesium phos})hate, 1 per cent. ; and organic substances, 3 per cent. Otiier chemists state the amount of organic matter to be from 2 to 10 per cent. ; but the most recent •0i-y :n :;'^l;- taiiiiii w^m. — Enamel. — Branching of the dentinal tubules. Dentinal tubules. Interglohular space. Fig. 46. — A portion of a ground tooth from man, showing enamel and dentin ; X 170 (Bohm and Davidoff). analyses seem to show that the organic matter present in the enamel of a fully formed tooth is too minute to be weighed. Cement or Crusta Petrosa. — At the point where the enamel ends the cement begins, and forms a covering of the dentin as far as the tip of the root. It is both structurally and chemically identical with bone, possessing both lacunae and canaliculi. The presence of Haversian canals is claimed by some histologists, es- pecially in the thicker portions ; while others deny it in normal teeth. Like bone, the cement is covered with periosteum, which 54 CONNECTIVE TISSUE. lines the alveolus and holds the tooth in its place. It is here called pericemciduin. Development of Teeth (Figs. 42— 45). — Al)0ut the seventh week of fetal life the germinal epitheliinn which covers the mucous mem- brane of the gums of the embryo, grows so as to form an elevated ridge, the maxillary rampart. A similar growth occurs downward into the tissue of the mucous membrane, forming the common dental germ or dental lamina. From this lamina ten cellular proc- esses, the special dental germs, are given off in each jaw, corre- sponding to the number of teeth. Each special germ becomes ^^ i ^J <4.^« J ^''■^\f--— Enamel-pulp. -Enamel-cells. "Odontoblasts. Fig. 47. — A portion of a cross-section through a developing tooth (later stage than in Kg. 45) : X 720 (Bohm and Davidoff ). The dentin is formed, but has become homogeneous from calcification. Bleu de Lyon ditferentiates it into zones (a and 6). At c is seen the intimate relationship of the odontoblasts to the tissue of the dental pulp. flask-shaped, and later flattened, and still later indented on its under side. The special germ becomes the enamel-organ of the future tooth, as from it the enamel is produced. From the corium of the mucous membrane grows a vascular papilla, the dental papilla, which, as it grows, increases the indentation of the .special germ and is covered by it. This papilla becomes the dentin and pulp of the tooth, the odontoblasts which cover it forming the dentin and the other portion the pulp. From the tissue which produces the papilla a vascular sac, the dental sac, is formed, which surrounds the special germ and its papilla. The dental sac and all the structures within it constitute the dental follicle. DEyriN. 5o The epithelial cells of the s|wcial dental germ become changed into three kinds of cells: (1) Columnar ceWs, (Khniiantoblasta or am'hich the heart consists differs from that just described in having its strife less marked, in being without sar- colemma, and in the fact that its fibers are short, each possessing a nucleus, and that they branch and join the fiber- cells contiguous to them. The nerves supplying cardiac muscle end in pk^xuses or networks. Involuntary Muscle (Fig. 57). — This is also called plain and non-striated. It consists of flat, fusiform cells, contrac- tile fiber-cells, having lengths varying considerably, each possessing a nucleus and one or two nucleoli, and having longitudinal striae. The cells are joined together by m.eans of an intercellular material. Involuntary muscular tissue is widely disseminated over the body ; it is found in the following locations : esophagus, muscular and mucous coats of the alimentary canal, bladder, ureter, uterus, Fallopian tubes, spleen, ciliary muscle, iris, ducts of glands, arte- FiG. 57. — Smooth muscle- cells from the intestine of a cat : in 1, isolated ; in 2 and 3, in cross-section ; X 300. At a the cell is cut in the plane of the nucleus ; at c, in the neigh- borhood of the pointed end. In 3 (from Barfurth) is seen the manner in which neigh- boring cells are joined to one another by intercellular bridges (Bohm and Davidoff ). 62 MUSCULAR TISSUE. ries, veins, lymphatics, sweat-glands connected with hair-follicles, scrotum, and areola of the nipple of the breast. The nerves of involuntary muscle end in plexuses or networks, as in the cardiac muscle. Development of Involuntary Muscular Tissue. — The contractile fiber-cells wiiich compose this tissue are formed from cells of the mesoblast, which elongate, the nuclei also elongating. The muscular tissue of the sweat-glands is formed from the epiblast. When new muscular tissue of the plain variety is formed, as when the uterus enlarges in pregnancy, growing from an organ weighing from 30 to 40 grams to one weighing from 900 to 1100 grams, this is accomplished by an increase in the size of the original fibers, and by the formation of new fibers from small cells which lie between the original ones. In the process of involution, that process by which the uterus returns to its original size, the fibers become fatty and are absorbed. Chemical Composition of Striated Muscular Tissue. — The sarco- lemma resembles elastin. When the contractile substance is pressed, a fluid is expressed, the muscle-plasma, which coagulates, the clot being myosin. A similar change takes place after death, producing rigor mortis or cadaveric rigidity. During life muscular tissue has an alkaline reaction ; while after death, owing par- tially, at least, to the formation of sarcolactic acid, it becomes acid. This also occurs after the muscles have been very active. Percentage Composition of Human Muscles. Water 73.5 Proteid.?, including the sarcolemma, proteids of connective tissue, vessels, and pigments 18.02 Gelatin 1.99 Fat 2.27 Extractives 0.22 Inorganic salts 3.12 The proteids in muscle-plasma are three in number: 1. Para- myosinogen, which coagulates at 47°— 50° C, constituting 17 to 22 per cent, of the total proteid ; 2. Myosinogcn or Myogen, coag- ulating at 56° C, 77 to 83 per cent. ; and traces of an albumin, 3Iyo-albumin. Both paramyosinogen and myosinogen enter into the clot which forms when the plasma coagulates. This ch^t is called myogen-jibrin or myosin-fibrin. The extractives are very numerous, creatin, creatinin, xan- thin, hypoxanthin, carnin, carnic acid, uric acid, tannin, and inosinic acid, all containing nitrogen and fats, glycogen, inosit, dextrose, and sarcolactic acid. This acid is attributed by some authorities to the glycogen, while others trace it to the proteids. The presence of urea in mammalian muscular tissue is still a matter of dispute. Muscular tissue always contains fat, and there is excellent authority for believing that, while some of this comes yKRVK-l'IllERS. 63 from the adipose tissue wliieh cannot he separated from the true miiscuhir tissue, fat is also a constituent part of muscle-plasma. The colorinii-matter of the red muscle is iDi/nJirmafin, which is prol>al)lv j)roduced from the hemoi!;lol)iu of the blood. Thi' inorfjanic salts are principally those of })otassium, the most abundant beinii' potassium phosphate. Composition of (he Cardiac Muscle. — This variety of muscular tissue contains paramyosinogen and myosinogen, and undergoes cadaveric rigidity. Composition of Involnntary Masoi/ar Tissue. — Cadaveric rigidity has been observed in the stomach and uterus ; and from plain muscular tissue a proteid has been obtained which resembles mvosinogcn. NERVOUS TISSUE. The nervous tissue of the body is made up of nerve-fibers, nerve-cells, and neuroglia. Nerve-fibers (Fig. 58). — This kind of nervous tissue is also called fibrous and tc/titc nervous matter. Fibrous nervous matter should not be confounded with fibrous connective tis- sue ; the term " fibrous" simply implies that the nervous substance is arranged in fibers. Nerve-fibers are medullated and non- medullatcd. Medullated Nerve-fibers (Fig. 58) are Medullary sheath. Fibrils of axial cord. r-— Neurilemma. - Segment of Lantermann. Axis-cylin- . der. Fig. 58. Fig. 5y. Fig. 58. — Longitudinal section through a nerve-fiber from the sciatic nerve of a frog ; X 830 (Biihm and Davidoff ). Fig. 59. — Mcdullate nerve-fiber from sciatic nerve of a frog; in two places the medullary sheath has been pulled away by teasing, showing the "naked axis- cylinder"; X 212 (Bohm and Davidoff). G4 NERVOUS TISSUE. characterized by possessing a medullary sheath or white substance of Schicann, Avliich gives the white color to the nerve-fiber. Tliis is a protective covering to the essential part of a nerve, the axis- cylinder. The space inside the medullary sheath is the axial space, which is filled by the axial cord. This consists of axis-fibrils em- bedded in the neuroplasm, a material of semi-fluid consistency, both fibrils and neuroplasm being covered by a delicate mem- brane, the axoleinma. When nerve-fibers have been prepared for microscopic examination the axial cord changes its appearance l)y the coagulation of the neuroplasm, and the altered cord is what is commonly called the axis-cylinder. The prindtive sheath, nucleated sheath of Schwann, or neurilemma, is a membrane which encloses the white substance of the nerves, except- ing those within the nerve-center. Neuri- lemma (also written neurolemma) is a term formerly applied to what is now called ji^^ri- neurium. The medullary sheath is not continuous; at regular intervals it is absent, and only the primitive sheath and axis-cylinder are present. This gives to the nerve the ap- pearance of constrictions, known also as the nodes of Ranvier. The portion of nerve between these constrictions is an internode, in the middle of which is a nu- cleus. Medullated fibers make up the white part of the brain and spinal cord, and the nerves that have their origin in these struct- ures, the cerebrospnncd nerves. In size they vary from 2 // to 19 //. This variety never branches except near the termination. NonmeduUated Nerve-fibers (Fig. 60). — These are also known as gray, gelatinous, and fibers of Remak. These have no white sub- stance, but are composed of fibrillse, which are probably enclosed in a sheath, the neurilemma, in which are nuclei, NonmeduUated fii)ers, unlike those that are medullated, fre- quently branch. Nerve-fibers are associated together in bundles, funiculi (Fig. 61), each of which bundles is enclosed in a sheath of connective tissue, penneurium. The funiculi are surrounded by a similar sheath, the epineuriuyn, which binds them together and in which are the blood-vessels, lymphatics, and nerves of the nerves, the last being the nervi nervorum. Within the funiculi is connective tissue, embedded in which are the nerve-fibers. Modes of Termination of Nerve-fibers. — The nerves which supply striated muscle subdivide near their ends, and one of the Xucleus. J Fig. 60.— Remak's fibers (nonmedullated fibers) from the pneumogastric nerve of a rabbit ; X 360 (Bcihm and Davidoff). Xh'llVh'-Fini'JRS. G5 branches ooos to a iiuisciilar liber. Its primitive sheath is con- tinuous with the sarcoleninui, and the medullary sheath terminates. The axis-ovlinder breaks up into fine ramifications, which are em- bedded in granular nucleated prott)j)lasm ; this is a motor end-organ or end-plate (Figs, G2-().")). In involuntary muscle the nerve-fibers end in plexuses, from which fine branches pass to the contractile fiber-cells. Xerve-fibers also end in special organs, of which there are various kinds : End-bnlbs of Krause, tactile corpuscles, Pacinian corjiuscles, orga)is of Golgi, and muscle-spindles. End-bulbs (Fig. 67). — An end-bulb consists of a cylindrical, oblong, or spheroidal body formed from the connective-tissue sheath of a medullated nerve-fiber. Within this is a core with many nucleated cells, in which the axis-cylinder terminates. End- Fibrils of axial - - i^ cord. Medullary sbeath. Fig. 61. — Transverse section through the sciatic nerve of a frog ; X 820; at a and 6 is a diagonal fissure between two Lanterraann segments; as a result, the medullary sheath here appears double (Bohm and DavidofF). (Compare Fig. 60.) bulbs are found in the conjunctiva, in the papillae of the lips and tongue, the skin and mucous membrane of the penis, the clitoris, vagina, epineurium of nerve-trunks, and in tendon. In the synovial membrane of some joints, as in the fingers, end-bulbs also occur, and are here called articular end-bulbs. Tactile Corpuscles. — These consist of connective tissue which forms a capside, from which are given off membranous partitions or septa. After winding around the corpuscle the axis-cylinder enters it, and terminates in an enlargement. Tactile corpuscles occur in the papillae of the skin of the hand, foot, front of the forearm, lips, and nipple ; also in the mucous membrane of the tip of the tongue and the conjunctiva lining the eyelids. Pacinian Corpuscles (Fig. 70). — These are also called corpuscles of Vater. Each corpu.scle consists of concentrically arranged layers of connective tissue, with nucleated cells, A medullary 5 66 NERVOUS TISSUE. Nerve. Fig. 62. Fig. 63. Nerve. So-called granular sole. End-brush. So-called ■sf - granular ».' sole. — End-brush. »-ji ^Muscle- ' i\ fiber. Figs. 64 and 65. Fig. 66. Figs. 62-65.— Motor endings in striated voluntary muscles. Fig. 62, from Pseudopus Pallasii : X 160. Fig. 63, from Laca-ta riridis ; X 160. Figs. 64 and 65. from a guinea-pig; X 700. Fig. 66. from a hedgehog; X 1200. Asa consequence of the treatment (T. 182, I) the arhorescence is shrunken and in- terrupted in its continuity. In Figs. 62 and 6.3 the end-plate is considerably larsrer than in Figs. 64 and 65. ' In Fig. 62 it is in connection with two nerve-branches. Fig. 66 shows a section through an end-plate. The latter is bounded externally by a sharply defined line, which can be traced along the surfoce of the muscle-fiber. This is to be regarded as the sarcolemma (Bohm and DavidofiF). NERVE-FIBERS. 67 ncrve-liber enters at one cikI and passes into an interior space which contains a transparent substance ; here only the axis- FlG. 67.— Etid-bulb of Krausc from conjunctiva of man ; methyleue-blue stain (Dogiel). Fig. 68. — Cylindric end-bulb of Krause from intermuscular fibrous tissue septum of cat; metbylene-blue stain (Huber). cylinder is present. This terminates at the end of the corpuscles in an enlargement or in minute branches, an arborization. These corpuscles exist in the subcutaneous tissue of the palm - Nucleus of lamellse. - End-cell of core. Lamellse. j. I 1.- Axis-cylinder in core. - Cubic cells of core. Termination of medul- lary sheath. Axis-cylinder of nerve- fiber. Medullary sheath of nerve-fiber. Neurilemma and sheath of Henle. Fig. 69.— Corpuscle of Herbst from bill of duck ; x 600 (Bohm and Davidoff). of the hand and sole of the foot, and in the penis. Observers have also found them in the pancreas, lymphatic glands, and thyroid. 68 NERVOUS TISSUE. Fig. 70. — Pacinian corpuscles from mesorectum of kittoi : A, showing the fine branches on central nerve-fiber; B, the network of fine nerve-fibers about the cen- tral fiber ; methylene-blue preparation (Sala). Fig. 71. — Genital corpuscle from the glans penis of man ; methvleue-blue stain (Dogiel). Fig. 72. — Meissner's tactile corpus- cle; methylene-blue stain (Dogiel). NERVE-CELLS. 69 On/an of Golr/i (Fig. 7."}). — At the point where muscles and their tendons join, the tcndon-hundlos present an enhirgcinent, between the fasciculi of which one, two, or more nervt'-HlxTs enter to terminate in an arl)ori/ati(in which is cliaractcrized bv varicositii's. The term " oruan of Golgi " inchides tlie enlargement and the arborizations. Muscle-spindles. — These are de- scribed under the name neuro-mus- cular spindles. A spindle is a fusi- form body having a length of from 0.75 mm. to 4 nnn. Externally is a sheath of connective tissue within which is the interposed bundle, con- sisting of from ten to twelve muscle- fibers, resembling embryonic fibers. The nerve-fibers distributed to these spindles divide, and the axis-cylin- ders clasp the fibers by flattened ex- pansion. Xone of these spindles has been found in either the muscles of the eye or the tongue. They are con- sidered to be sensory nerve-endings in the muscles. Nerve-cells (Figs. 75-78). — This kind of nervous tissue is also called (/i'fij/, cineritious, cellular, vesicular, nervous rnafler. Nerve-cells are of different sizes, varying from 4 // to 150 12. Their shape also varies greatlv, some being ovoid, while others are very irregular in outline. Each cell contains a large, distinct, and spheroidal nucleus, with a single nucleolus, and fibrillated pro- toplasm. In the protoplasm are some- times angular granules, Kissl's f/ran- ules, which are stained by methylene- blue. From nerve-cells are given off two kinds of processes : axis-cylinder pro- cesses or neuraxes, and protoplasmic processes or dendrites. These are the principal elements in nerve-fibers. The number of these processes or Fig. 73. — Neurotendinous nerve end-organ from rabbit ; teased preparation of tissue stained in methylene-blue (Huber and De Witt, Jour, of Comp. Neurol., vol. 70 NERVOUS TISSrK. poles determines the name of the cell : thus u cell Avith one pole Fig. 74. — Cross-section of neurotendinous nerve end-organ of rabbit, from tissue stained in methylene-blue : »?, muscle-fibers; t, tendon; c, capsule of neurotendi- nous end-organ ; m n, medullated nerve-fiber (Huber and DeWitt, Jour, of Camp. Neurol., vol. X.). is unipolar; one with two poles, bipolar ; and one with three or more, multipolar. Nucleus. Nucleolus. Fibrillar structure. Medullary sheath. Fig. 75. — Bipolar ganglion-cell from the ganglion acusticum of a teleost (longi- tudinal section) ; the medullary sheath of the neuraxis and dendrite is continued over the ganglion-cell ; X 800 (Bohm and Davidoff ). The process in a so-called " unipolar" cell is, in reality, two processes which have become united. Such cells occur in the spinal ganglia (Fig. 78). NERVE-CELLS. 71 Axis-cylinder Process. — Kvcrv nerve-cell has an axis-cylin(l(.'r process, which, in the meduUated nerve-fiber, becomes the axis- cylinder, and in the non-meduUated is the nerve-tiber itself. This Dendrite. Neuraxis. Fig. 76.— a ganglion-cell from anterior horn of the spinal cord of calf; teased preparation ; X 140 ; by this method only the coarsest ramifications of the dendrites are preserved; the rest are torn ofl' (Bohm and Davidoff). process is characterized by the fact that it gives off a few side-shoots, collaterals in its course ; thus its branching is very limited. To this process some histologists apply the term neuron, — Dendrite. Neuraxis Neuraxis. Dendrite." Fig. 77. — Motor neurones from the anterior horn of the spinal cord of a newborn cat; chrome-silver method (Huber). while others call it neuraxon, or axon, and reserve the term "neuron" for the whole nerve-unit — that is, the cell and all its processes, for which the term neurone is more commonly used. 72 XERVOrS TISSUE. Cells which have but one axis-cylinder process are mononeuric ; those having two such processes are dineunc; and trineuric is applied to those having three. Most nerve-cells are mononeuric. Ganglia. — A ganglion is a collection or group of nerve-cells. These occur upon the posterior roots of the spinal nerves (Fig. 78), upon some of the cranial nerves, and in connection with the svmpathetic nervous system. In these structures the cells have a nucleated sheath continuous with that of the nerve-fibers con- nected with them. From each cell in the ganglion, upon the roots of the spinal cord, and among the cranial nerves is given off but one process, the axis-cylinder process. Passing in a convoluted form from the cell, this process, before it leaves the ganglion, divides into two, one going to the nerve-center, the other to the periphery. From this descrip- tion it will be seen that these cells have no dendrons. In the cells of the sympathetic ganglion, besides the axis-cylin- der process, there are also sev- eral dendrons. Protoplasmic Process. — Unlike the axis-cylinder process, this va- rietv is characterized by its fre- quent branching. The larger branches are called dendi'0)is, and the finer ones dendrites. The idea that the axis-cylin- der process alone conveys ner- vous impulses, and that the den- drons and dendrites are nutritive organs exclusively, is at the present time replaced by the belief that nervous impulses also travel along the branches of the protoplasmic process. The anatomic fact that the fibrils of the axis-cylinder have been traced through the body of the cell into the dendrons, seems to substantiate this theory. It is a most important fact that the nerve-unit, or the " neu- rone^' of some writers — that is, the nerve-cell and its branches — does not anastomose or join with any other nerve-unit, but the terminal twigs or arborizations of one intertwine with those of another, and nerve-impulses may thus pass from one to the other. This inter- twining is called synapse, a word literally meaning a clasping. This subject will be again referred to when the physiology of nerves is discussed. Neuroglia (Fig. 79). — This is sometimes spoken of as a con- nective tissue, but it is in structure unlike connective tissue as we have studied it. It is also unlike it chemically, consisting of -• Xiicleiis. Fig. 78. — Granglion-cell with a pro- cess dividing at a ( T-shaped process i : from a spinal ganglion of the frog; X230 I Bohm and Davidoff i. NFAJROdlJA. 73 neurokeratin. Its origin iVotn the epiblast also differentiates it from connective tissue, which arises from the mesohlast. Neuroglia is the sup|K)rting tissue of tiie nerve-cells and nerve- fibers of the brain and spinal cord. It consists of cells and fibers. In describing ciliated ej)ithclium it will be remembered that among the locations in which it was foimd the ventricles of the brain and the central canal of the spinal cord were mentioned. From the attached ends of these cells branching neuroglia-fibers pass to the surface of the brain and the cord, and terminate at the pia mater in enlargements. Other fibers of the neuroglia arise from cells, )i(iirof//i(i, glin- or spiiUv-ceUs, which are stellate in shape. These filxTs aid in supporting the nerve-cells and nervc-tibcrs. Development of Nerve-cells and Nerve-fibers. — The following description is from Schafer : " All nerve-cells in the body are developed from the cells of the neural groove and neural crest of the early embryo ; the neural groove closing to form the neural canal, the cells of which form the spinal cord and brain, and the neural crest giving ofl', at intervals, sprouts which become the rudiments of the ganglia. The cells which line the neural canal are at first all long, columnar cells, but among these, and probably produced by a metamorphosis of some of these, rounded cells {neuroblasts) make their appearance, and presently from each one a process begins to grow out. This is the axis-cylinder process (neuron) and is char- acterized by its enlarged ex- tremity. As it grows, it may emerge from the anterolateral regions of the canal and be- come a motor neuron or ante- rior root-fiber. The dendrons appear somewhat later than the n e u r o n . The axis-cylinder processes of some of the neu- roblasts remain within the nerve-centers, and are devel- oped into association or intra- central fibers. " The sprouts from the neural crest contain the neu- roblasts from which the pos- terior root-fibers are devel- oped. Neurons grow out from these neuroblasts in two directions, so that the cells become bipo- lar, one set, forming the posterior root-fibers, grow into the pos- terolateral portion of th(! spinal cord, and ramify in the develop- ing gray matter ; the other set, containing the afferent fibers of the Fig. 79. — Neurogliar cells : a, from spinal cord of embryo of cat ; h, from brain of adult cat; stained in chrome silver (Huber). 74 NERVOUS TISSUE. mixed nerves, grow toward the developing anterior roots, and eventually mingle with them to form the mixed nerves. As development proceeds, the bipolar ganglion-cells become gradu- ally transformed in most vertebrates by the shifting of the two neurons, into unipolar cells ; but in many fibers the cells remain permanently bipolar. '' The ganglia on the sympathetic and on other peripheral nerves are formed from small masses of neuroblast-cells, which separate off from the rudiments of the spinal ganglia and give origin to neurons and dendrons much in the same May as do the neuroblasts within the central nervous system. " The manner in which the medullary sheath and neurolemma of the nerve-fibers are formed is not well understood. The neuroglia- cells appear to be developed from cells which are at first similar to the neuroblasts, but, in place of giving off a neuron and den- drons, a num])er of fine processes grow out from the cell in all directions, forming the Hbers of the neuroglia." Chemistry of Nervous Tissue. — The following is the analysis of the brain of an ox by Petrowsky : Gray Matter. WTiite Matter. Water 81.60 per cent. 68.30 per cent. Solids 18.40 '• " 31.70 " " 100.00 100.00 The percentage composition of the solids is as follows : Gray Matter. White Matter. Proteids 55.37 24.72 Lecithin 17.24 9.90 Cholesterin and fat 18.68 51.91 Cerebrins 0.53 9.55 Other organic compounds (including neurokera- tin and protagon) 6.71 3.34 Salts 1.45 0.57 Halliburton divides the solid con.?tituents of the nervous tissues into the following classes : a. Proteids. — These comprise a very considerable percentage of the solids, especially in the gray matter (over 50 per cent.). h. Xeurokeratin and nuclein. c. Phosphorized constituents, especially jirotagon and lecithin. d. Cerebrins. — Nitrogenous substances of unknown constitu- tion. e. Cholesterin. — Especially abundant in white matter, /. Extractives. — Creatin, xanthin, hypoxanthin, inosit, lactic acid, leucin, uric acid, and urea. fj. Gelatin and Fat. — From the adherent connective tissue. /(. Inorganic Salts. — The total mineral matter varies, according to different writers, from 0.1 to 1 per cent. Percentage of proteids Solids. in solids. 16.533 51 30.088 33 20.191 42 28.354 31 27.471 31 30.245 28 27.631 33 38.684 29 cni'.MisTiiY OF yFJivors Tissri:. 75 Googliogan ^ivt'S tlie Ibllow inii: ii-^ representing parts per 1U(JU of brain : Total a.ers of this group have the chemical formula CgHjoOg. Those which are of special interest are Dextrose, Levulose, and Galactose. Dextrose (glucose, grape-sugar, diabetic sugar) is normally found in the blood, chyle, lymph, and in very small amount in the urine. It occurs in grapes and some other fruits, and also in honey. Dextrose and levulose usually occur together. In the disease known as " diabetes mellitus " the quantity of dextrose in the blood and urine is very much increased. It is a substance of ranch interest, as it is in the form of dextrose that the carbo- hydrates of the food find their way into the blood. In its pure state dextrose is colorless and readily crystallizes ; it is soluble in cold, more so in hot water. It is dextrorotatory, whence it derives its name. In alkaline solutions dextrose reduces metallic oxids, a property which is made use of in determining its pres- ence and in measuring its quantity. Various tests are employed for the detection of dextrose ; among these are Trommer's, the fermentation-test, and Fehling's. Trommer's Test. — The method of applying this test is as follows : If the presence of dextro.se in an organ is to be ascertained, this should be cut into small pieces and boiled with water and sulphate of sodium, and the mixture filtered in order to have a clear solu- tion, which is essential. Some of this should be poured into a test-tube, and a few drops of a solution of sulphate of copper added. To this a solution of caustic potash should be added, so as to make the contents of the tui)e distinctly alkaline. The tube should now be heated, when, if dextrose is present, just before the 88 CARBOHYDRATES. boiling-point is reached, a reddish precipitate, consisting of cup- rous oxide, will form. Levnlose, galactose, lactose, and maltose have reducing power similar to that of dextrose, but ditiering in degree ; thus, the power of lactose as compared with dextrose is but that of 7 to 10, while maltose has one-third less power than dextrose. Cane-, maple-, and beet-sugar have no reducing power, and must first be converted into dextrose before the reaction will take place. Fermentation-test. — This test depends upon the fact that under the influence of yeast dextrose is decomposed into ethyl alcoiiol and carbonic anhydrid. Fehlinr/s Test. — This test is based on the same principle as that of Trommer, namely, the property possessed by dextrose to reduce metallic oxids. It is employed not only to determine the ]iresence of dextro.se, but also to measure the quantity present. The te.st- solution is liable to undergo changes which invalidate the result ; it should, therefore, be freshly prepared, or at least be boiled be- fore it is used. The principal change wliich takes place is the formation of racemic acid from the tartaric acid of the solution, and this has the same reducing action as the sugar. If after boiling the solution is clear, it may be inferred that decomposition has not taken place, and it may be used. The solution is ])repared in the following manner : 34.639 irrams of pure recrystallized copper sulphate are dis- solved in distilled water, which is made up to 500 c.c. This solu- tion should be kept separate from the second solution, which is made by dissolving 175 grams of crystallized Rochelle salts and 60 grams of sodium hydroxid in distilled water, and likewise made up to 500 c.c. It is found by experience that when these two solutions are mixed the resulting mixture does not keep well. When the test is to be made equal quantities of the two solu- tions are mixed. Prof. Bartley's method of applying this test in urine is as follows : 10 c.c. of the solution are measured into a suitable flask. To this 10 c.c. of a freshly prepared 10 per cent, solution of potassium ferrocyanid are added, and about 30 c.c. of water. The mixture is heated on a water-bath, and the urine, previouslv diluted with water if it contains mucii sugar, is run in from a faucet, drop by drop, until the blue color just dis- appears. The addition of the slightest excess of sugar shows itself bv the solution becoming quickly l)rown. By careful com- parative tests Prof. Bartley has found this method to be reliable and accurate provided the solution is not boiled during the reduc- tion. The best temperature he finds to be between 80° and 90° C. • Polanscope. — Tiiis is also known as a polarimeter. It may be emploved to determine the presence of dextrose. In order to understand the use of this instrument it will be necessary to con- sider briefly the subject of the polanzation of light. MOSOSACCHARIDS OR GLUCOSES. «9 Cunimon \\^^\\X. is duo to vibratory clisturl)auc'es in tlio ether, which are propag^ated through it as waves, the direction of the vibrations being transverse to tliat 3 Inosit or imi.sclc-.siigar has been tbiiiul in the muscles, lungs, liver, spleen, kidneys, and brain, and patholugieally in urine. It occurs also in beans and — i)li/iic of li\ duo to an enzyme, ami/lopsin. Erythrodextrin. — If the action of either of these enzymes u]ion starch is not arrested in the soluble-starch stage, erythrodexti-in is formed. The blue color caused by the action of iodin on starch ii'radually changes into violet, reddish violet, and then to reddi.-h brown as the starch gradually changes to erythrodextrin. 'J'liis reddish-brown color produced by iodin is the test for erythro- dextrin. Achroodextrin. — If the action of these enzymes is continued, a still i'urthcr change in the starch takes place. It passes into the condition of achroixlextrin, and iodin fails to produce any color. A further change into maltose follows the formation of achroii- dextrin. In the action of these enzymes uj)on starch outside the body the first product is a mixture of dextrin with the sugar, but within the body there is little doubt that all the starch is converted into sugar, and as such is absorbed. If starch is treated with boiling dilute acids instead of with these enzymes, the changes just described take place with far greater rapidity, and d(;xtrose results. Maltodextrin. — If diastase, the enzyme contained in malt extract, is used instead of saliva or pancreatic juice, maltodextrin is formed ; and indeed it is not certain that the latter sul)stance is not Ibrmed in addition to the erythrodextrin and achroodextrin when saliva and pancreatic juice are employed. jNIaltodextrin differs from the dextrins already described in being more soluble in alcohol, in being diffusible, and in responding to Fehling's test. It also passes over into maltose by the continued action of the diastase. Glycogen. — The similarity between glycogen and starch has led to the term "animal starch" being applied to the former. Glycogen was first discovered in the liver, where it is normally found to the amount of between 1.5 and 4 per cent, of the Aveight of the organ,, which may in man be increased to 10 per cent. It also exists in muscles to the amount of from 0.5 to 0.9 per cent., and it is estimated that all the muscles of the body contain as much glyco- gen as does the liver. It occurs also in the integument and the mucous membranes of the human embryo, in the placenta and the amnion, in white blood-corpuscles and in pus-corpuscles, in oysters and in other mollusca. For purposes of study it is usu- ally obtained from the liver of an animal (a rabbit or a dog), in which it is stored up in amorphous granules around the nuclei of the liver-cells. Glycogen is soluble in water, and with iodin gives a port-wine color. This color does not distinguish it from erythro- dextrin ; but when it exists pure, as ordinarily it does not, it is 7 98 CARBOHYDRATES. precipitated by 60 per cent, alcohol, ^vllile the dextrins are not precipitated. Watery solutions are dextrorotatory. In i^eneral it may be said that the action of the enzymes and of boiling acids upon glycogen is the same as upon starch. The glycogen oi' the liver becomes converted, by physiologic processes, into liver-sugar, which is regarded as identical with dextrose. In this process probably no maltose is formed, such as occurs in the artificial hydrolysis already described. This difference would seem to indicate that in the liver-cells there is no enzyme to which this action can be attributed ; for, so far as can be judged, most enzymes produce maltose, and not dextrose, and up to the present time no dextrose-producing enzyme has been obtained from the liver. Cellulose. — Nowhere in the animal body is cellulose found, but it exists in many of the vegetable alimentary principles upon Avhich man relies for his nutrition. As has already been stated, it is a constituent of the starch-granule, and so covers the granulose that the digestive fluids cannot reach it. A¥hen starch is boiled the granules burst, and thus access to the granulose is given. It has recently been suggested that there is in the intestinal canal, formed by the epithelial cells, an enzyme which has the power of causing: a dijyestion of the cellulose. But the evidence of the existence of such an enzyme is very meagre. The disappearance of the cellulose is probably due to the action of bacteria, all the products being unknown, though marsh-gas, acetic and butyric acids are among them. This change takes place especially when vegetables, such as celery and lettuce, and fruits are eaten whose cell-walls are tender and have not yet become lignified or woody in character. Lignin is the name applied to cellulose in this advanced stage. In the human intestine from 4 to (>0 per cent, of the cellulose taken in is dissolved. It doubtless has very little nutritive value, but is regarded as increasing by its local action intestinal peristalsis and keeping the bowels free. In the rabbit its absence from the food results in death, inflammation of the intestine being caused thereby ; but if horn-shavings, which are excreted unchanged, are substituted for cellulose, the animal maintains its health. The cellulose of some plants, such as the date, is regarded as a reserve material to be made use of in germination. The presence of cellulose is recognized by the fact that when treated with strong sulphuric acid it becomes converted into a sub- stance that is colored blue by iodin. Schulze's reagent is another test for its presence. This test consists in the production of a blue color when the substance is treated with iodin dissolved to satura- tion in a solution of chlorid of zinc to which potassium iodid has been added. ADII'OVKRE. ij'j THE FATS. The chemical eleinents entering into the composition of the fats are carbon, hydrogen, and oxygen. The fats are witlely dis- tributed throughout the human body. The percentage in theeolids and thiids is a.s Ibllows : Sweat 0.001 ■ Cartilage 1.3 Vitrodus humor 0.002 I Bono 1.4 Saliva 0.02 j Crvstallino lens 2.0 Lynipli 0.05 Synovia 0.06 Li(iuor amnii 0.06 Chvle 0.2 .AIucus 0.3 Blood 0.4 Bile 1.4 Milk 4.3 Liver 2.4 Mu.seles 3.3 Hair 4.2 Brain 8.0 Nerves 22.1 Adipose tissue 82.7 Marrow 96.0 F'ats are regarded by chemists as composed of fatty acids and glycerin, and are called glycerids or glyceric ethers. \Mien treated with superh(>atcd steam and mineral acids, and in the human body under the influence of steapsin, the lipolytic enzyme of the pancreatic juice, the fats are decomposed into glycerin and the respective fatty acid. This change is expressed by the follow- ing formula, palmitin being taken as an example : C3H,(O.C,,H3,CO)3 + 3H.p = C3H,(OH)3 + 3C\,H3,CO.OH Palmitin. Water. Glycerin. Palmitic acid. There are three varieties of fats: Olein, C3H5(OCi-H33CO)3 ; palmitin, C3H,(OCi5H3iCO)3 ; and stearin, C3H5(OC„H3.CO)3. These differ in several particulars, one of the most important being their melting-points : Olein melts at 5° C. ; palmitin, at 45° C. ; and stearin, at from 53° to (36° C. Their respective acids are oleic, palmitic, and stearic. Fats are characterized by being insolul)le in water, slightly soluble in alcohol, and very soluble in ether and chloroform. All fats are mixtures of the three varieties, the difference in the con- sistency of any given fat depending u])on the proportion in which the neutral fats are present. Thus in the more solid fats, such as suet, stearin predominates, while in the fluid fats it is olein which is in excess. The latter exists in human fat to the amount of from 67 to 80 per cent. When fats decompose or become " rancid," propionic, acetic, and formic acids are produced. Adipocere. — It sometimes happens that when bodies are dis- interred, instead of being found in a condition of putrefaction, they are discovered to have been changed into adipocere or r/rave- wax. This is a peculiar substance of a waxy nature, and consists of calcium soaps, of which the fatty acids are palmitic and stearic. Acid ammonium soap has been found in some cases. This change 100 THE FATS. occurs in bodies which have been interred in moist soils, or have been in water for a considerable time after death. Source of Fat in the Human Body. — Human fat is de- rived from the fats, the carl)()hydrates, and the proteids of the food. In fatty meats, nuts, eggs, milk, and other foods more or less fat exists as a constituent, and undoubtedly contributes to the forma- tion of the fat of the body. That the fat of the food can be deposited as such in the tissues was for a time denied, but it has been shown by feeding starved dogs upon such fatty foods as rape- seed oil, linseed oil, or mutton talhnv, that tliey will not only take on fat, but that some of the kind of fat which enters into their food is deposited as such in their tissues. Food containing starch and sugar is also fattening in its nature, and persons who have an excess of fat are placed upon a diet containing a minimum of these ingredients. Herbivorous animals — the cow, for instance — rely entirely upon vegetable food for their support, and it is the carbo- hydrates which this contains that are converted into the fat of their milk and that which covers their muscles. It is doubtless from the carbohydrates that most of the fat is produced. That proteid food will also produce fat is shown by the amount of the latter which carnivorous animals put on. Offices of Pat. — Tlie offices which fat subserves in the human body are manifold : (1) It protects the underlying parts from in- jury, as in the palm of the hand and the sole of the foot ; (2) it serves as a lubricator, as in the sebaceous matter poured out upon the skin, wiiich it keeps soft and pliable ; (3) it acts as a non- conductor of heat, aiding in the retention within the body of the vital heat which would otherwise be lost so rapiotassinni are "soft." In tlie discussion of intestinal digestion it will he seen that the process of sa{)()niHeation takes place in the small intestine, and that the soaj) there formed aids in the important functions of that portion of the alinientarv canal (p. 2.30). Emulsification. — Hesides being saponifiable, fats are also emul- sitiahle — capable of forming an emulsion. If oil and water are poured into a test-tube, they w'ill at once separate, the oil floating on the water. If the mouth of the tube is closed by the thumb aiul the tube tirinly shaken, the oil and water will form a milky mixture, but will separate again when the agitation ceases; if a small amount of an alkali is added and the tube is again shaken, separation will not take place as before, but the milky ap])ear- ance will continue for some consideral^le time. If a drop of the mixture is placed under the microscope, it will be found that the oil-globules have been broken uj) into an exceedingly tine state of subdivision, some of the ])articles being too small to measure even with a very high magnitying power. This more or less permanent subdivision and suspension of the oil-globules constitutes an emul- sion. The change is not a chemical one, but purely physical. A similar process takes place in the small intestine during intestinal digestion (p. 231) and is regarded by some as a necessary prelimi- nary to the al)sorption of fat (p. 253). The flit in milk is in an emulsified condition ; consequently milk may be regarded as a natural emulsion. I/CCithin. — This substance may be regarded as a flit, and from the fact that it contains phosjihorus it has been spoken of as " phos- phorized fat." Its formula is C42Hs^XPO,,. It is decomposable into glycerin, stearic acid, phosphoric acid, and an alkaloid, cholin. Lecithin occurs in the brain and other nervous tissues, consid- ered by some authorities as here produced by decomposition of protagon, in yolk of egs^s, blood-corpuscles, semen, bile, and milk. It is also one of the constituents of protoplasm. Cholesterin. — This substance bears some resemblance to the fats in that it is insoluble in water, but soluble in ether, hot alco- hol, and chloroform. It is a constituent of protoplasm, and is also found in blood-corpuscles, bile, serum, and white substance of Schwann. In the blood it is in combination with oleic and pal- mitic acids. It forms esters with fatty acids, and as such exists in the fatty secretions of the skin. Lanolin, the fat obtained from sheeps' wool, is said to be rich in esters, and these are very resist- ant to the action of bacteria. 102 PEOTEIDS. PROTEIDS. These ingredients are the iiKjst important constituents of mus- cles, gkinds, nervous tissue, and bhjod ; indeed, it has l)een said of them that none of the phenomena of life occurs without their presence. Of them Gamgee says : " They are highly complex, and, for the most part, uncrystallizable compounds of carbon, hvdrogen, oxygen, nitrogen, and sulphur (phosphorus is also some- times present), occurring in a solid, viscous condition, or in solu- tion in nearly all the solids and liquids of the organism. The different members of the group present differences in physical, and to a certain extent even in chemical properties. They all pos- sess, however, certain common chemical reactions, and are united by a close genetic relationsliip." Tlieir percentage-composition is as follows : Carbon 50 to 55 Nitrogen 15 "18 Hvdrogen 6.9 •' 7.3 Oxygen 20 '• 23.5 Sulphur 0.8 '■ 2 AVhen proteids are burned there is found in the ash a certain quantity of salts ; from the ignition of egg-albumin, for instance, chlorids of sodium and jiotassium result, and salts of calcium, magnesium, and iron. It is still undecided whether these salts are integral parts of proteids or impurities, probably the latter. The percentage of proteids in some of the .solids and liquids of the body, and their wide distribution, are shown by the follow- ing table : Cerebrospinal fluid 0.09 Chyle 4.09 Aqueous humor 0.14 Blood 8.56 Liquor amnii 0.70 Spinal cord 7.49 Intestinal juice 0.95 Brain 8.63 Pericardial fluid 2.36 Liver 11.64 Lymph 2.46 Thymus 12.29 Pancreatic juice 3.33 Muscle 16.18 Svnovia 3.91 Tunica media of arteries . . . . 27.38 Milk 3.94 Crystalline lens 38.30 Various attem]ns have been made to ascertain the constitution of the proteids and give a formula for them, but the differences in the results obtained by equally com]ietent chemists have been so great that practically nothing worthy of quoting is on record. There is no douijt. however, that the molecules are very large. General Properties of Proteids. — All are insoluble in alcohol and ether. They are also said to be soluble with the aid of heat in concentrated mineral acids and caustic alkalies ; but inasmuch as this is accompanied with decompositien of the pro- COL OR-REA CTIONS. 1 03 toids it is a question wlu'thcr it can be regarded as a true solu- tion. Action on Polarised I^ight. — All proteids are levorotatory (see p. 81>), l)ut the degree of rotation varies considerably. The following table gives the speeitic rotatory power of several of the proteids : I'roteid. Value of {a)d. Serum-albumin — 56° to - 68° Eir<;-all)uniin _ 3.5.50 u _ 38.08° Laotalbuinin - 36° " - 37° Seruin-jrlobulin — 59.75° Fibrinogen — 43° Alil)ulins Xueleoproteids Proteoses Peptones Coagulated Proteids Poisonous Proteids. Serum-album ill. Egg-albumin. Lactalbuniin. ]\lv()-all)umiu. f Acid-albumin. )^ Alkali-albumin. r Sorum-globulin (paraglobulin). Fibrinogen. ! Paramyosinogen. 1 Myosinogen. Lactoglobulin. [ Cry.stallin. f Caseinogen. t Vitellin. ^ Alburaoses. Globuloses. Vitel loses. I Caseoses. (^ Myosinoses, etc. r Parapeptone. J Propetone. j He mi peptone. [ Antipeptone, etc. ( Fibrin. < Myosin. I Casein. ALBUMINS. These are sometimes described under the name of native albumins. They are soluble in water, dilute saline solutions, and saturated solutions of sodium chlorid and magnesium sulpiiate. When their solutions are saturated with ammonium sulphate the albumins are precipitated, and when heated to a temperature of about 70° C. they are coagulated. It is important to distinguish between precipitation and coar/nlafion. As just stated, the albu- mins are precipitated by ammonium sulphate ; but they still retain their identity and solubility. AVhen, however, they are coagulated they become insoluble and are changed into a form known as 108 PEOrElDS. coagulated proteid. Some proteids are precipitated by certain reagents, and not by others, and this fact is made use of to dis- tinguish the proteids from one another. The following table gives the temperature at which the differ- ent albumins coagulate : Albumins. Temperature. Serum-albumin («) 73° C. (;i) 77° {7) 84° Egg-albumin 73° Lactalbuiiiin 77° Myo-albuiiiin 73° Serum-albumin. — The fluid of blood in its normal condi- tion is plasma; after coagulation, serum. The albumin of blood remains in the serum after blood has coagulated, and hence is known as serum-albumin. AVhen to plasma or serum is added an equal amount of a saturated solution of ammonium sulphate, the fluid is said to be half saturated with ammonium sulphate. In this condition the globulins and nucleoproteids are precipitated, but not the albumin. The same result is obtained by completely saturating it with magnesium sulphate. If now^ the fluid is filtered, the globulins and nucleoproteids will be filtered out, and the fil- trate (the liquid which has ])assed through the filter) may l)e put into a dialyzer, and the salts will thus be removed, leaving only the serum-albumin. The fact that exposure of serum-albumin to different temperatures (about 73° C, 77° C, and 84° C.) results in three separate coagulations indicates that what is called serum- all)umin is in reality three different substances or forms, which are called respectively «-albumin. which coagulates at 72° to 75° C ; /J-alljumin, coagulating at 77° to 78° C ; and ;. -albumin, coagulating at 83 to 86° C. Halliburton, to whom we owe this information, has ascertained that in the plasma of the horse, ox, and sheep a-alburain is absent, while /i'-albumin and v-albumin are present ; in the rep- tiles, amphil>ians, and fishes, the blood of whicli he examined, only «-albumin was normally found, while in that of man and of all other mammals and birds all three were present. Magnesium sulphate does not precipitate serum-albumin, while it does serum-globulin, so that by this reagent the two may be separated, the salt being added in crystals until the solution is completely saturated ; or, as stated, half-saturation Avith ammo- nium sulphate will bring about the same result. The specific rotatorv power of solutions of serum-albumin is -56°. Hsfg-albumin. — As its name implies, egg-albumin is obtained from the wiiite of eirg. If much of it is taken in the food, or if it is injected into the blood, part of it appears in the urine. When shaken with ether it is precipitated. Nitric acid, heat, and ALKMJ-ALB UMIN. 109 tlio prolongcil action of alcohol coagulate ci2:g-all)uniin ; and mer- curic chlorid, nitrate of silver, and lead acetate precipitate it, forniiiiij: insolul)le compoinids. I/actalbumin. — This physiologic ingredient occurs in the milk together with two other j>roteids, caseinogen and lactoglobu- lin. Halt-saturation with ainnioniuin sulphate precipitates the caseinogen anil lactogloi)ulin, and the lactalbuniin which remains in solution niav be precipitated by saturation -svitli sodium sulphate. A temperature between 70° and 80° C. (about 77° C) will coagu- late it. Unlike serum-all)nmin, it consists of but a single proteid. Its percentaue comj)osition is: C, 52.19; H, 7.18 ; X, 15.77; S, 1.73; (). 23. 13. Myo-albumin. — This is the albumin of muscle, and resembles serum-albuiuin. ALBUMINATES. The members of this group are sometimes described under tlie name derived albutni)is, because they are derived from albumin bv the action of acids or alkalies. Globulins, when treated in the same manner, also produce albuminates. When a mineral sub- stance is added to a solution of albumin, a new compound is formed, which is denominated an albuminate of the mineral, but as such products are not physiologic ingredients we shall not con- sider them. Albuminates are insoluble in water and neutral solu- tions containing no salt ; soluble in acids, alkalies, and dilute saline solutions ; precipitated when saturated with sodium chlorid or magnesium s»dphate ; and are not coagulated by heat. Acid-albumin. — This is the product of the action of a dilute acid — hydrochloric, for instance — upon an albumin. In this con- version the proteid undergoes important changes. Its solution is not coagulated by heat, and when it is neutralized the proteid is precipitated. The conversion from the native to the acid-albumin is gradual, and is hastened by heat, care being taken that the tem- perature is not sufficiently high to coagulate it. Globulins are likewise converted into acid-albumins by the same means, but more readily, wdiile coagulated proteids or fibrin require the acid to be concentrated. By some writers the term syntonin is applied to the particular acid-albumin resulting from the globulin myosinogen ; while others use it as a synonym for acid-albumin in general. The point of special physiologic interest in connection with acid-albumin is that in the process of stomach-digestion it is one of the products. Alkali-albumin. — As acids acting upon albumins and globu- lins produce acid-albumin, in a similar manner alkalies produce alkali-alliumin. There is an interesting historic point in connec- tion with this proteid. Mulder found that by heating albumin 110 PROTEIDS. with caustic potash a product was obtained which he regarded as the basis of all albuminous substances, and to which he gave the name of " protein." Under this theory proteids are supposed to be modifications of protein, but the theory is an obsolete one, and Mulder's protein is nothing more than alkali-albumin. Alkali- albumin is produced in the small intestine when the albumins and globulins of the food are acted upon by the alkali of the pancreatic juice. GLOBULINS. The members of this group are soluble in dilute saline solu- tions, as, for instance, ] per cent, sodium chhn'id, insoluble in water, concentrated solutions of sodium chlorid, magnesium sul- phate, and ammonium sulphate, and are coagulated by heat. The following table gives the temperatures at which the im- portant globulins coagulate : Globulins. Temperature. Serum-globulin 75° C. Fibrinogen .56° Myosinogen 56° Crystalli'n 73° Serum-globulin (Paraglobulin). — Fibrinoplastin is another name for this proteid, given to it at a time when it was believed that it was connected with the process by which fibrin was formed, as in the coagulation of blood. It exists in human plasma to the extent of about 3 per cent. It exists also in lymph and chyle. Fibrinogen. — This globulin is associated with serum-globulin in plasma, lymph, and chyle. It is a substance of great interest, inasmuch as upon its presence the coagulability of blood depends, a process in Avhich the soluble fibrinogen becomes insoluble fibrin. It is precipitated by half-saturating with sodium chlorid, and by this means may be separated from serum-globulin. F'ibrin. — Fibrin is obtained by whipping blood with twigs or wires. The material that clings to these is fibrin together with some of the blood-corpuscles, which become entangled in its meshes. These may be washed out in running water. When ex- amined with the microscope fibrin is seen to be made up of threads which intertwine with one another, forming a network. Drv fibrin is obtainable from blood to the amount of from 0.2 to 0.4 per cent, of its weight. Its percentage-composition is C, 52.68 ; H, 6.83; N, 16.91 ; S, 1.10; O, 22.48. It is soluble in 5 to 10 per cent, solutions of sodium chlorid, sodium sulphate, magnesium sulphate, and some other salts. It swells in hydrochloric acid of 0.2 per cent, strength and becomes acid-albumin and proteoses. If pepsin is also present, this change takes place more quickly, the fibrin becoming converted into two globulins, one coagulating at 56° C. and the other at 75° C, and then becoming acid-albu- TRUE NUCLEI NS. 1 1 1 mill, jiroteo.ses, ami finally ])('j)t(nio,s. 'rrvpsiii acts as does pepsin, except that tlic reaction must he alkaline, not acid, the products being- alkali-allMunin, proteoses, and pei)tones. In speaking of the ash produced when fibrin is burnt, Schiifer says that it invariably contains lime, but not more than other pro- teids, nor more than the iibrinogen from which it is Ibrmed. This fact comj)letely disposes of tlu; theories of coagulation wiiich as- sume that librin is merely a combination of fibrinogen with lime, such as those of Freund, Arthus, Pekelharing, and Lilienfeld. Myosinogen. — This globulin occurs in muscular tissue, and in the condition called ric/or mortis coagulates, and in this condi- tion is iiii/osin or muscle-clot. A similar change, Jie(it-vi(/or, occtn's when jnuscle is heated, coagulation taking place when the temper- ature reaches 47° to 50° C. ; and a second coagulation at oG° C. This is due to the fact that there are two globulins: paramyo- sinogen which coagulates at the lower, and myosinogen at the higher tem])ernture. I/actoglobulin. — This proteid is found in cows' milk in such minute quantity that it has escaped the analyses of excellent chemists. Its amount in colostrum is considerable. Crystallin. — The proteid matter of the crystalline lens is crystallin, and exists in that structure to the amount of 34.93 per cent. Two varieties of crystallin are described : a-crystallin and ^^'-crystallin, differing in composition, specific rotatory power, and coagulation-point. The former is more abundant in the outer portion of the lens ; the latter, in the inner. NUCLEOPROTEIDS. These substances are composed of nucleins and proteids, and occur in the nuclei and ])rotoplasm of cells. Nucleins have been obtained from the nuclei of ])us-corpuscles, spermatozoa, yolk of Qg^, yeast, liver, brain, and cows' milk. The term nucleins is used rather than nuclein because there are several of these substances, differing in solubility and chemical composition. They are divided by Ho])pe-Seyler into three grou])s : 1. Nucleins which consist only of nucleic acid, whose formula is not definitely known, but is approximately C4oH5^N^O,-(P20:;)2. Indeed, nucleic acid is itself probably not a single substance, no less than four having been found by investigators. This acid does not give the reactions of proteid, but is characterized by its great affinity for basic dyes, such as methyl-green (see Karvo- kinesis, p. 28). Nucleins of this group occur in spermatozoa. 2. True Nucleins. — These occur in the nuclei of cells, and on decomposition yield proteid, xanthin bases (hypoxanthin, xanthin, guanin, adenin), and phosphoric acid. The true nucleins, which contain the most nucleic acid, are obtainable from the 112 PROTEIDS. chromatin libers of the nucleus ; those which occur in the nucleoli contain less nucleic acid. 3. Pseud onucleins. — These are sometimes called paranucle- ins, and are ol^tainable from the nucleoproteids, such as caseinogen and vitellin. They yield none of the bases as do the true nucleius, but only proteid and phosphoric acid. The nucleoproteids are divided into two groups : 1. Those which yield true nucleins on gastric digestion, and to Avhich Ham- marsten restricts the name "nucleoproteids;" and 2. Those which yield pseudonucleins on gastric digestion, called by Hammarsten ^' nucleo-albumins." In this latter group are caseinogen and vitellin. To make this resume complete, mention should be made of the phospho-glucoproteids. A glucoproteid is a compound of proteid with a carbohydrate, and includes mucins among other substances. From mucins a carbohydrate may be obtained called animal gum, which when acted upon by a dilute mineral acid is converted into a reducible but non-iermentable sugar having the formula CgHjoOg. Most of the glucoproteids contain no phosphorus, but some do, and these constitute the phospho-glucoproteids. There is some evidence to show that from many of the proteids (acid- and alkali- albumin, serum-albumin, serum-globulin) a reducing substance may be obtained, which may be a carbohydrate. Caseinogen. — This was formerly regarded as an alkali- albumin, but is now placed among the nucleoproteids ; and if we accept the classification of Hammarsten, it \\ould be placed among the nucleo-albumins, for the reason that on gastric digestion it yields pseudonuclein. Caseinogen is the most abundant proteid of milk, the two other proteids being lactoglobulin and laetalljumin, and may be obtained from it bv saturation with sodium chlorid or magnesium sulphate, or 1)V half-saturation with ammonium sulphate. It is not coagu- lated bv heat. Human caseinogen has the following percenta2:e- composition: C, 52.24; H, 7.31 ; N, 14.9; P, 0.68; S, l.f?; (), 23.66 ; and yields no pseudonuclein on gastric digestion. AVhen acted upon by rennet caseinogen coagulates, becoming casein, which is soluble in dilute alkalies, such as lime-water. Rennet is obtained from the stomach of the calf, and owes its property of coagulating caseinogen to the enzyme rennin, also called chymosin. Upon the addition of rennet to cows' milk a curd or clot is formed, which consists of casein and the fat of the milk ; the liquid portion of the milk, after the curd is formed, is irJiey, consisting of water holding in solution the proteids, lacto- globulin and laetalbumin. lactose, and the salts. Another proteid, vhey-proteici, is produced from the decomposition of that portion of the caseinogen which is not changed into casein. The curd of human milk is of a softer and more flocculent character than that of cows' milk, and to render the curd of the latter more like that POISONOUS PROTEIDS. 113 of the former, ami thus aid di<;c'.sti<>n in the infant, lime-water or barley-water is sometimes added, simple dilution with water or hoiliui^ the milk producini:; the same elfect. One essential condition for eoaopula- tion was between 8000 and 9000. Of this numl)or, 1153 con- tracted the fever, and 114 of these died. A careful investigation showed that the water-supply of this mining-town had become in- fected by the stools of a single case of typhoid fever. These stools, in an undisinfected condition, had been deposited on the ground during the winter, and it was not until sjn-ing, when the snow melted and warm showers occurred, tiiat these infected dejecta were washed into the water-supply. The first case occurred within two or three weeks after. This instance demonstrates not only the infecting power of a single case of disease, but also the resisting power which the typhoid bacillus possesses against cold, for these stools had been frozen for several months. Indeed, from laboratory experiments we know that the Bacillus typhosus retains its vitality even after having been frozen for one hundred and ten days. But, while infection is not destroyed by freezing, it is by boil- ing, and there is no surer way of destroying the germs which Avater may contain than by boiling it for half an hour. Boiled water is not as iinpalatable as is generally supposed. Even if it Avas, nnpalatability is less objectionable than infection, and in all doubtful cases water should be boiled. Another lesson to be learned from this epidemic and from the laboratory experiments referred to is that ice may be a source CA RBOIIYDRA TES. 1 23 of infootion as well as water, and even though the water is boiled this will l)e of no avail if infeeted ice is useil to cool it. The writer investigated an epidemic of dysentery in which the disease was traced to ice used in drinking-water. The ice had been cut from a pond in which during the summer hogs wallowed, and in which they tlepositcd their excreta. When melted this ice had a most offensive odor. Other instances might be given show- ing the danger from the use of impure ice, but the one cited will suffice. Fortunately, there is now furnished for use in many of our cities artificial ice, which, if pro})erly prepared, is free from all contamination. In this process of manufacturing ice the water is not only boiled, but is distilled, and when ready for freezing is absolutely pure. But even this ice is not always what it claims to be. Unscrupulous dealers will often supply river ice when they are supposed to deliver the artificial protluct, and manufacturers of the latter are sometimes careless, ^\'ith boiled water and prop- erly manufactured artificial ice, all danger of infection through these channels will surely be prevented. Salts. — The list of salts taken in with the food has already been given, the most important being sodium chlorid, calcium phosphate, and the alkaline carbonates and phosphates. The offices which these salts perform in the economy of the body vary. By some of them the solubility of certain ingredients is made possible, such as the globulin of the blood by virtue of the presence of sodium chlorid. From the chlorids the hydrochloric acid of the gastric juice is produced. Salts are stimulants also to the glands, causing the latter to secrete more actively ; thus the diges- tive fluids are more abundantly poured out when the food is prop- erly salted, and the kidneys more completely perform their func- tions under the stimulation of the salts. If salts are removed from the food of a pigeon, it will die in three weeks ; the same deprivation of salts in the case of a dog will cause its death in six weeks. Carbohydrates. — These food-stuffs, in the form of starch and sugar, are especially abundant in vegetable foods and in milk, and less so in animal foods. Cane-sugar is an article of diet which is used to an enormous extent throughout the world. For an exceedingly interesting and valuable contribution to the literature of this suijject the reader is referred to Farmers' Bulletin, Xo. 93, issued by the United States Department of Agriculture, entitled " Sugar as Food," by Mary Hinman Abel. From this we have derived much information. Between seven and eight million tons of cane-sugar are used amiually in the different countries of the world ; England con- suming in 1895, 86 pounds per capita; the United States, 64 pounds; while Italy, Greece, and Turkey consumed less than 7 pounds. xVbout two-thirds of the cane-sugar now used is derived 124 FOOD. from the sugar-beet, Avhich lias becoiue so developed that Avhile the beet of 180(3 contained but per cent, of sugar, that of to-day contains 15 per cent. The following table gives the average composition of raw sugar from different sources : Anerage Composition of Raio Sugar. Sources from which obtained. Water. Cane- sugar. Other or- ganic sub- stances. Ash. Sugar-cane Per cent. 2.16 2.90 1.71 2.50 1.86 Per cent. 93.33 92.90 93.05 88.42 87.97 82.80 Per cent. 4.24 2.59 4.55 7.62 9.65 Per cent. 1 27 Sugar-beet " Sorghum Maize 2.56 0.68 1.47 0.50 Palm Maple . . The cane-sugar obtained from these sources is identical, and the popular opinion that beet-sugar is not as sweetening and not as good a preservative as that derived from the cane is erroneous. It is a satisfaction to know that the cane-sugar of commerce is as pure as is possible ; of five hundred samples examined by the United States Government chemists, not one was adulterated. The value of sugar as food has been abundantly demonstrated ; its office being to furnish energy to the body in the form of heat and muscular work, in which process it undergoes oxidation and becomes converted into COj and HoO (p. 249). Experiments con- ducted in Berlin and elsewhere show that sugar is " well adapted to help men to perform extraordinary muscular labor ;" and it has been used in the German army M'ith such excellent results in ap- peasing hunger, mitigating thirst, and preventing exhaustion, that an increase of the sugar ration to sixty grams a da^y has been recommended. The general conclusions drawn by Abel in the bulletin above referred to are as follows : " One may say in general that the wholesomeness of sweetened foods and their utilization by the system are largely a question of quantity and concentration. For instance, a simple pudding flavored with sugar rather than heavily sweetened is considered easv of digestion; but when more sugar is used, with the addition of eggs and fat, we have, as the result, highly concentrated forms of food which can be utilized by the system only in moderate quantities and which are always forbidden to children and in- valids. ''It is true that the harvester, lumberman, and others who do hard work in the open air consume groat amounts of food contain- ing considerable ((uantities of sugar, such as ^tie and doughnuts, and apparently with impunity; but it is equally true that people PROTKIDS. 125 livint; an indoor life find that nndne amounts of pie, cake, and pudding, with iiiiihly swri'tened preserved fruit, and sugar in hirge amounts on cooked cereals, Wring indigestion sooner or later. '' From a gastronomic point of view it would seem also that in the American cuisine sugar is used with too many kinds of food, with a consequent loss in variety and piipiancy of flavor in the different dishes. The nutty flavor of grains and the natural taste of wiKl fruits is concealed h\ the addition of large quantities of sugar. " In the diet of the under-nourished large amounts of sugar woukl doubtless help to full nutrition. This point is often urged by European hygienists. In the food of the well-to-do it is often the case, however, that starch is not diminished in proportion as sugar is added. That sugar on account of its agreeable flavor is a temptation to take more carbohydrate food than the system needs cannot be denied. The vigor of digestion in each particular case would seem to suggest the limit. A lump of sugar represents about as much nutriment as an ounce of potato, but while the potato will be eaten only because hunger prompts, the sugar, be- cause of its taste, may be taken when the appetite has been fully satisfied. " Sugar is a useful and valuable food. It must, however, be remembered that it is a concentrated food, and therefore should be eaten in modemte quantities. Further, like other concentrated foods, sugar seems best fitted for assimilation by the body when supplied with other materials which dilute it or give it the neces- sary bulk. " Persons of active habit and good digestion will add sugar to their food almost at pleasure without inconvenience, while those of sedentary life, of delicate digestion, or of a tendencv to corpulency would do better to use sugar very moderately. It is generally assumed that four or five ounces of sugar per day are as much as it is well for the average adult to eat under ordinary conditions." Pats or Oils. — These food-stuffs are found in milk, in butter, in cheese, in the fatty tissues of meat, and also in some vegetables, such as nuts. The following table shows the amount in some of the ordinary foods : Meat 5 to 10 per cent. Milk 3 to 4 " " Ecrcrs 12 " " Chee.<^e ..........'. 8 to 30 " " Butter 85 to 90 " " Proteids. — This class contains some of the most valuable of the fooil-stuffs. The importance of the class is readily understood wdien it is recalled that the principal ingredients of the blood and the muscles are supplied by the proteids of the food. This is the only class whose members contain nitrogen, and it has therefore 126 FOOD. been sometimes spoken of as the "nitrogenous" class. The albu- minoids contain nitrogen also, but this class has little nutritive value, except gelatin, which is valuable, but, as has already been stated, its nitrogen is not available for tissue-forming. The proteids are represented in eggs by albumin, in milk by casein, in meat by myosin, in peas and in beans by legumin, and in the cereals by gluten. The amount of proteids varies in different foods ; thus there is in Meat 15 to 23 per cent. Milk 3 to 4 " " Peas and beans 23 to 27 " " Grains (flour) 8 to 11 " " Bread 6 to 9 " " Potato 1 to 4 " " The following diagram (Fig. 85) shows the amount of the principal food-stuffs in some of the more generally used foods : Explanation. Proteids. VM< r'nrhohvilratc Water. Human milk. Cows' milk. Meat. Fish Leguminous fruits. Potato., Green vegetables.. Bread.. A2J.A 83 ■ lllii^ s^^^^^^s^s^^=^=^^s=ss^=^g^^^^m^^^ siAtu 86 ■ .■^^^^ '= ^^-=--=^=r^^=^-^=^-^^^-^=^ ^=3=^. --=^ 20 JI 68 ^I^^^^H : ]]g?>rF::^^=.-^=_-^b=::=z^^jr-^^^^^'^-^^-=^^^=^^g 18 7 62 1^^^^-:^^-= ^^^-=---:- . .r-=:^-^^^--==^-^^^^.j^ j l^r-=^^=^^:TT= .-^r-:!-:^ =^ SSi ? 1 15 HH^^^^iHiiiiiiiiiiiyiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii^^^^^^^ 2 20l 75i 2i5 88 ■i^.^ = ^- : ^ «- i Sf! S6 ■illllllllilllll Illlllllllllllllllllllllllllllllllllllllllllll^^^^^.^^^^^^^ Fig. 85. — Diagram showing proimrtioo ot the principal food-stufls in a f w typical comestibles. The numbers indicate percentages, tialts and iuuige^tible materials omitted (after Yeo). From the above consideration of the food-stuffs it is seen that they are in most respects the same as the tissues of the body ; yet it would be erroneous to infer that the fats and the proteids of the food go directly into the tissues as such, and take the ])lace of the fats and the proteids wliich are Avasted. There are many inter- mediate steps, some of which are known and will be discussed, and others of which we are entirely ignorant. Experience has abundantlv demonstrated that in order to maintain the bodv at PllOTEIDS. 127 its pliysiolduic stMiidard representatives from all these four classes of tood-stiilfs iini>t he siipplied. Jf man is deprived of water, death speedily residts; it comes as surely, thoii«^h not so qnieklv, if fats or earhohydrates or ])roteids are cut off from the food- supjily. Indeed, a man may be starved to death hv withholding the silts. Whenever, theref(jre, it is foimd that life can he maintained physioloj^ieally for a lon<; j)eri()d of time on any diet, it is certain that this diet contains representatives of all the classes enumer- ated. Thus, milk, which is the sole food of young children — among some of the Eskimos to the sixth year of life — is found on analysis to contain such re})resentatives ; the inorganic class being represented by water and salts, the carbohydrates by milk-sugar, the fats by butter, and the proteids by casein and some albumin. It is not, however, sufficient that each class should be represented, but the proportions of the ingredients must l)e proper. It is possi- ble that any given food may have the requisite constituents, but may have too much of one and too little of anf)ther. It has been determined that the daily waste of the body is 250 to 280 grams of carbon and 15 to 18 grams of nitrogen, or about 16 to 1. The carbon given oiF is principally in the form of carbonic acid in the expired air, while the urea of the urine contains most of the nitrogen eliminated. To supply the waste of the body, then, the proportion in the food of carbon to nitrogen should be as 16 to 1. In proteids, however, the ])rop()rtiut 20 grams of nitrogen, but 700 of carbon. Oatmeal contains carbon and nitrogen in the proportion of 15 to 1. If the diet was exclusively of meat, then in order to supply the bodv with the necessarv amount of carbonaceous material a 128 FOOD. very large quantity of meat would be required, aud to meet this requirement there would be taken in an excess of nitrogenous constituents, thus placing a serious burden on the eliminating organs to get rid of them. Experience demonstrates that a mixt- ure of foods is the true physiologic method of supplying the wants of the human body ; from meat are obtained the proteids necessary for nutrition ; from the potato is derived the starch ; and from butter is secured the fot. Experience shows also that a higher standard of efficiency is maintained by a variety of food, a change being made from one kind of meat to another and from one vegetable to another, always, however, giving the body the food-stutfs in the proper quantities to supply its demands. There are individuals who believe that meat-eating is not onlv unnecessary to, but that it tends also to degrade man ; they conse- quently confine themselves to vegetable diet : this exclusive dietarv practice is called *' vegetarianism." It is true that vegetables contain all the physiologic ingredients necessary for nutrition, but, as above noted in the case of the potato, the proportion is not such as will subserve the best interests of the body, and physiologists have decried the system as being irrational. The following ex- tract from a letter of Dr. Alanus, a vegetarian, published in the Medical and Sutr/ica/ Reporter, gives his experience in this matter : '' Having lived for a long time as a vegetarian without feeling any better or worse than formerly with mixed food, I made one day the disagreeable discovery that my arteries began to show signs of atheromatous degeneration. Particularly in the temporal and radial arteries this morbid process was unmistakable. Being still under forty, I could not interpret this symptom as a mani- festation of old age, and being, furthermore, not addicted to drink, I was utterly unable to explain the matter. I turned it over and ov^er in my mind without finding a solution of the enigma. I, however, found the explanation quite accidentally in a work of that excellent physician, Dr. E. Monin, of Paris. The following is the verbal translation of the passage in question : ' In order to continue the criticism of vegetarianism we must not ignore the work of the late lamented Gubler on the influence of a vegetable diet on the chalky degeneration of the arteries. Vegetable food, richer in mineral salts than that of animal origin, introduces more mineral salts into the blood. Raymond has observed numerous cases of atheroma in a monastery of vegetarian friars, amongst others that of the prior, a man scarcely thirty-two years old, whose arteries were already considerably indurated. The naval surgeon, Treille, has seen numerous cases of atheromatous degeneration in Bombay and Calcutta, where many people live exclusively on rice. A vegetable diet, therefore, ruins the blood-vessels and makes one prematurely old, if it is true that a man is as old as his arteries. It must produce at the same time tartar, the senile arch of the r ROT KIDS. 129 oornoa, and ])Ii(»spliatiiria.' IIa\iiig-, niifortiinatcly, seen these newest results oC medical iiivestiiiatioii eoiilirnie^l l)V my own ease, I liiive, as a matter ot" eonrse, returned to a mixed diet. I can no longer consider purely vegetable food as the normal diet of man, but only as a curative method which is of the greatest service in various morbid states. Some patients may follow this diet for weeks and months, but it is not adapted for everyl^ody's continued use. It is the same as with the starvation cure, which cures some patients, but is not tit to be used (tontinually by tiie healthy. I have become richer by one experience, which has shown me that a single brutal fact can knock down the most beautiful theoretic structure." From the above consideration of the sul))ect we learn that a proper diet must contain not only the various food-stuffs, but must contain them in the proper proportion. These ])roportions will vary considerably according to the age of the individual and his occupation, and also according to the climate in which he lives. A glance at the chemical composition of milk, which is the sole food of the infant, shows that the amount of j)roteids and fats is very much above that in the food of the adult. Another factor to determine the nutritive value of any food is its digestibility. The chemical analysis of cheese would place it high among the foods, but experience shows that its constitution is such as not readily to permit the action of the digestive fluids, and its availability as a food is therefore low. The following table represents a daily diet as recommended by two authorities : Moleschott. Ranke. Proteids 120 (grains. 100 (grains. Fats 90 " " lOO'' '• Carbohydrates 333 " 250 " Ranke's diet, which he regarded as sufficient for himself, Aveigh- ing 74 kilos, corresponds to 230 grams of carbon and 14 grams of nitrogen. AVhile such diets as these are undoubtedly " adequate," they are, after all, to be regarded as general averages only, to be varied according to the needs of those for whose maintenance provision is to be made. Thus, Voit would supply to a man weighing 70 to 75 kilos, and working ten hours a day, 118 grams of proteid,. 56 grams of fat, and 500 grams of carbohydrates : this diet would give him 328 grams of carbon and 18.3 grams of nitrogen. Stewart regards 500 grams of l)read and 250 grams of lean meat as a fair quantity ifbr a man fit for hard work. To this ho adds 500 grams of milk, 75 grams of oatmeal in the form of porridge, 30 grams of butter, 30 grams of fat either in the meat or otherwise, and 450 grams of potatoes. From this would be obtained 20 grams of nitrogen and 300 grams of carbon, contained 130 FOOD. in 135 grams of protcid, ratlier less than 100 grams of fat and somewhat more tluin 400 grams of carboliydrates. In the form of a table this would appear as follows: Quantity in Grams. Grams of Food. Nitrogen. Carbon. Proteids. Fat. Carbo- hydrates. Salts. Lean Meat Bread . . Milk . . Butter . . Fat . . . Potato . Oatmeal . 250 500 500 30 30 450 75 8 "l.'5' 1.7 33 112 35 20 22 47 30 55 40 20 io' 10 8.5 7.5 20 27 30 ' i ' 245 " 25 '95 ' 48 4 6.5 3.5 0.5 4.5 2 20.2 299 135 97 413 21 The following is the ration of the English soldier Bread G80 grams. Meat 340 " Potatoes 453 " Veo-etables 226 " Milk 92 " Su-rar 37.7 grams. Coffee 9.4 '■ Tea 4.6 " Salt 7 " The ration of the German soldier varies considerably from this In peace. In war. Bread • • 750 g rams. Bread . . 750 grams Meat . . l."30 Biscuit Meat Smoked meat .... . . 500 " Eice . . 50 . . 375 " or Barley groats . . . 120 . . 250 " Legumes . . 2.30 or Fat . . 170 " Potatoes . . 1500 Pvice or Barley groats . . Lesrumes . . 125 " . . 125 " . . 250 " The following tables show the net and approximate gross weights of 1000 rations (and of 1 ration) as usually issued by the United States Subsistence Department: Table I.— The '^Emergency" Ration. 1000 Complete Rations. Net weiglit. Approxi- mate gross weight. Hard Bread Pounds. 1000 625 250 125 0.58 40 2.5 31.25 Pounds. 1000 625 250 Coffee, roasted and ground 125 0.58 <^alt 40 2.5 31.25 Baa:?, wrappers, etc 100 1000 rations 2074.33 2.07 2174.33 2.17 PRO TEWS. i;3i Table II.— TAc "Field" Ration. 1000 Complotu Rations. Bacon . . Hard I } read Ik'aii.s . . Potatoes, Unions, and Canned Tomatoes, when possible Coti'oo, roasted Sunar Vinegar Candles Soap Salt Pepper, black . 1000 rations 1 ration . . Net Approxi- weight. mate KfOSS weight. Pounds. Pounds. 750 883 1000 1125 150 1G2 1000 1158 80 92 150 IGl 80 97 15 17 40 44 40 44 2.5 3 3307.5 3786 3.31 3.79 When flour is issued instead of hard bread, 40 pounds of balclng-powder or dry yeast. Table III. — The "Travel" Ration, used on Journeys by Railroads, Stages, or Steamboats. 1000 Complete Rations. Net weight. Approxi- mate gross weight. For first four days : Hard Bread Pounds. 1000 750 450 80 . 150 Pounds. 1125 Beef, canned . . . . 875 Bean;:, baked, 3-pound cans 520 Coffee, roasted 92 Su-ar 161 1000 rations 2430 2.43 1000 2773 1 ration 2 77 After fourtli day add : Tomatoes (sjallon cans) 1360 1000 rations 3430 3.43 4133 1 ration 4 13 Table IV. — The "Travel" Ration for Journeys when Liquid Coffee is furnished. 1000 Complete Rations. Net weight. Approxi- mate gross weight. Hard Bread Pounds. 1000 750 450 Pounds. 1125 Beef, canned 875 Beans, baked, 3-pound cans 520 1000 rations 2200 2.2 2520 1 ration 2.52 Twenty-one cents per ration are allowed for purchase of liquid coffee. 132 FOOD. Table V. — The "Garrison" Ration, icith the usual ProportioTis of Fresh and Salted Meats and Vegetables. 1000 Complete Rations. Net weight. Approxi- mate gross weight. Meat : Pork, J^ Bacon, -J-^ Fresh Beef, fg, 875 lbs., or fresh Beef, 750 lbs., and Canned Salmon, 100 lbs Flour Vegetables : Dry — Beans or Peas Or Rice or Hominv Fresh— Potatoes, 800 Ibs.'i (Potatoes . . . .700 lbs. Onions . 200 lbs. / °'' \ Canned Tomatoes, 300 lbs. Coffee, green Sugar Vinegar Candles Soap Salt Pepper, black 1000 rations 1 ration Pounds. 75 150 875 1125 75 50 ) 800 / 300 100 150 80 15 40 40 2.5 Pounds. 125 177 . 885 1507 81 54 808 350 122 161 97 17 44 44 3 3877.5 3.88 4475 4.48 The table on page 133 shows the chemical composition and nutrient value of these foods. Until the Spanish-American War the United States had no occasion to provide a ration especially adapted to the soldier in the tropics, and as a result it is conceded that the present ration is inadequate to his needs. A court of inquiry appointed to investi- gate the character of the food issued to the troops during the war with Spain reported that " it seems to be clearly estaldished that the armv ration as supplied, Avithout modification, to the troops serving in the West Indies, was by no means well adapted for use in a tropical climate." A most admirable essay on the subject of " The Ideal Ration for an Army in the Tropics," written l)y Captain E. L. INIunson, Surgeon in the United States Army, and to which was awarded a prize, appeared in the Journal of tJte Mi/itar)/ Service Institution of the United States for May, 1900, to which our readers are referred for an excellent and exhaustive consideration of the subject of diet in hot countries. From this essay we desire to make some quotations. Dr. Munson conclude.- " that the present United States Army ration is made up of admirably selected articles in more than suf- ficient variety, and that it is not only wholly unnecessary, but quite inadvisable to consider any nutritive substances outside those articles legally established as components of the food for the United States soldier. He thinks, however, that the proportion in which these are issued should be materially altered. The diet- aries which he recommends are given on pages 134 and 135. ]' nor KIDS. 133 o ex "^ O C_3C05;0COtij' O Z C C Ti Artici.i 9 C will IIP IIIMi 5~5=~5=-» "1 — p 5 • 2 - " -■ M Is X n ^ — ' ■ 5 2 • X-m m re • • C T.- ■5 "£," ^'z^ ■ y-.^ — p p. c ~ pi ■ ■ < ■ P 1 (T 3 h5 ■ g^ • . 52 . ■05. . . f ■ ■ c£? 5. 1 ' 1 1 o1^ otsio K J5 to a, e> _fj^to c5a5'x :n!irrre = c S — " OIU01U9(U0«S Cr C — ^^ 1 • S C h3 00 ^I *j— ^^j^J»_i CCi-» cc *-*. — — .fcen P 1 yi Jo tC X 00 — CliW tiOw-IO 00 p 5= p p cc p bi <5> be ;£ «5 be i- to i= ic '*- 30 ^ cc cs be io be bn re to ro •-* H-* „ ►0 3 *'x lO K-- h- IC X*.-Jio po^top?': C- i— p p p ^ * T3 ^ c — 1 -' tOl-'l-• ►-• to to _>-' to to to -1 re X -^ M CC "w CC bo ic bi *. 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Quantity, Fats, hvdrates Protein, Nitrogen, in ounces. ! gm. , ^g^. | &'^- i Sm- Fuel-value, calories. Fresh Beef Flour . . . 10 18 2.4 16.0 3.0 3.5 44.75 5.60 1.22 0.45 1.53 380.46 40.18 81.70 33.80 94.25 41.68 55.08 15.16 9.50 1.77 6.67 7.90 2.42 1.52 0.27 590 1850 Beans . . . 240 Potatoes Dried Fruit Sugar . . . 380 220 397 Total . 52.9 53.55 630.39 123.19 18.78 3677 Total carbon, 395.14 gm. Nitrogen to carbon, 1 : 19.6. " This table shows the nutrient vahie of a proposed dietary for the tropics, containing the greatest amount of food-material, which might be drawn l)v the soldier. " The following table shows a proposed dietary for the tropics, especially applicable to field service, in which the fatty constitu- ents attain their maximum and the potential energy is high. Tropical Dietary. II. Articles. Quantity in ounces. Fats, gm. Carbo- hydrates, gm. Protein, gm. Nitrogen, Fuel-value, gm. calories. Bacon .... Hard Bread . . Beans .... Dried Fruit . . Sugar 6 18. 2.4 3.0 3.5 105.06 6.63 1.22 1.53 371. 8l' 40.18 50.70 94.25 15.64 73.12 15.16 . 1.77 2.49 1 1042 11.74 i 1926 2.42 240 0.27 220 397 Total . . . 32.8 114.44 556.94 105.69 16.92 3825 Total carbon, 328.76 gm. Nitrogen to carbon, 1 : 23. "The nutrient value of the ordinary dietary as proposed for garrison duty in the tropics is as follows : J ropical Dietary. III. Articles. Quantity in ounces. Fats, gm. Carbo- hydrates, "gm. Protein, gm. Nitrogen, gm. Fuel-value, calories. Fresh Beef . . Soft Bread . . Potatoes and On- ions . . . Dried Fruit . . Sugar 10 20 3.5 44.75 6.80 0.72 1.53 299.20 73.09 50.70 94.25 41.68 53.83 8.60 1.77 6.67 8.61 1.40 0.27 590 1506 340 220 397 Total . . . 52.5 53.80 517.24 105.88 16.95 3053 Total carbon, 828.76 gm. Nitrogen to carbon, 1 : 18. PROTEIDS. 135 "For the tbllowiiio; coiiibiiialiou the .several articles of the ra- tion most closely approaching in character to the food-materials used hy natives of the tropics — proj)ortioned in quantity accord- ing to the standard projmsed for hot climates — iiave been se- lected. Tropical Dietary. IV. Total carbon, 327.50 gm. Nitrogen to carbon, 1 : 19.6. "On averaging these four dietaries, as furnished by the ration proposed for the tropics, the mean nutrient composition is seen to be as follows : Dietary. Quantity in ounces. Fats, gm. Carbo- hydrates, gm. Protein, iNitrogen, gm. 1 gm. Fuel-value, calories. No. I No. II No. III. . . . No. IV. . . . 52.9 32.9 52.5 64.5 53.55 114.44 53.80 10.11 57.97 630.39 556.94 517.24 598.82 123.19 105.69 105.88 104.25 18.78 16.92 16.95 16.71 3677 3825 3053 2947 Average . 50.7 560.85 109.06 17.34 3375 Total carbon, 350 gm. Nitrogen to carbon, 1 : 20. " It will be observed that while the above dietaries differ con- siderably among themselves, yet when averaged together in equal proportions they do not greatly vary from the nutritive standard for the tropics already proposed — and this is an additional reason why a selection of the same articles of the ration should not be made from day to day. It is seen that the above average dietary, as compared with the nutrient standard, is still slightly deficient in fats and fuel-value and a trifle in excess as regards protein. These defects, if they may be considered as such, are, however, readily corrected by a rotation of dietaries, in which dietary II. is used twice where dietaries I., III., and IV. are each employed but once. The results of this change are as follows : 136 FOOD. DiETAPY Quantity Fats. uii.i.\v.\. in ounces. gm. Carbo- hydrates, gm. Protein, Kitrogen, Fuel-value, gm. gm. calories. No. I .52.9 53.55 No. II 32.9 114.44 No. II ... . 32.9 114.44 No. III. . . . 52.5 53.80 No. IT. ... 64.5 10.11 680.89 556.94 556.94 517.24 598.82 123.19 18.78 3677 105.69 16.92 3825 105.69 16.92 3825 105.88 16.95 8053 104.25 16.71 \ 2947 Average . 47.1 69.43 572.06 108.88 17.26 3465 Total carbon, 368.83 gm. Nitrogen to carbon, 1 : 21. " From the above tables it is evident that such clianges as are advisable in the adaptation of the United States Army ration to tropical conditions are chiefly in the line of a reduction in quantity Fresh Beef (quarters) . . . . or Fresh Mutton or Pork or Bacon or Salted Beef or Dried Fish ( cod i or Fresh Fish, average (whole) 10.0 10.0 6.0 6.0 10.0 10.0 14.0 41.68 46.20 27.54 15.64 40.27 45.37 31.73 Flour . . . 18.00 55.00 or Soft Bread .... 20.00 53.83 or Hard Bread .... 18.00 73.12 or Corn-meal .... 20.00 50.40 Beans . . or Peas . . or Rice . . or Hominv Potatoes or Potatoes 80 per cent, and Onions 20 per cent or Potatoes 70 per cent, and Canned Tomatoes 30 per cent. . . Dried Fruit (average) 2.4 2.4 4.0 4.0 15.16 16.38 8.75 9.20 6.67 7.35 4.40 2.49 6.44 7.26 5.07 44. 75 . 62.90 . 112.54 , 105.06 . 64.68 , 1.13 . 0.79 . 590 720 1093 1042 688 197 120 5.60 380.46 18-50 6.80 299.20 1506 6.63 371.81 1926 12.40 425.80 1986 1.22 40.18 240 0.75 41.80 246 0.45 88.87 407 0.67 88.75 430 16.0 16.0 9.50 8.60! 0.45 81.70 380 16.0 8.1"; 1.40 0.72 73.09 1.86 0.54 65.80 340 297 8.0 1.771 0.27 1.53 35.80 bugar . . . or Molasses . or Cane-syrup Coffee, green . . . or Coffee, roasted . . or Tea, green or black 3.5 1 gill 1 gill 1* ! 94.25 56.05 56.25 220 "397" 269 269 Tinegar . . Salt . . . . Pepper, black Soap .... Candles . . . 3? ?>ll' .^-, f>7.. I -7 circK I'llOTKII)!^. V?>1 Ptandarii dietary as given hy typical dietaries of men at hard labor in the northern portion of the temperate zone. Standard dietary as given by proposed U. S. Army ration for tropical service. Standard dietarv for uative laborers in the tropics : based on the weight of 14.5 pounds for purposes of comparison. Standard dietarv of the laboring class of natives in the tropics (Java, British India. Guadeloupe, Abyssinial, as determined from the food actually consumed by them at normal body-weiffhts. of the foods at present provided by a too eenerous government. It is true that the suirars and starches should be slightly augmented, but their increase is small when compared with the considerable reduction of nitrogenous and fatty material which is proposed. Many of the components of the present ration, as is seen by the above table, require no change in the consideration of the trop- 138 MILK. ical dietary, being not only admirably selected, bnt also properly pro])ortioned." The ideal ration for an army of United States soldiers on dnty in the tropics is therefore snggested as being of the composi- tion given in the table on page 136. ]\Inch less than the quantities quoted in these various dietaries will sustain life, but, of course, far below the physiologic standard ; thus the diet of a poor London needlewoman was found to consist of but 5-1 grams of proteid, 29 grams of fat, and 292 grams of carbohydrates. Age is another important factor which enters into the problem of the dietary. In early life, not only must the waste of the tissues be met, but there must be growth by increase of tissue. In estimating the amount of food to be given to a child as com- pared with an adult, it is not the weight of the body which is to be taken into account, but its surface, as it is to this that the waste is proportional. Thus a child weighing 20 kilos will present a body-surface about one-half that of a man weighing 70 kilos, and it would require therefore one-half as much food as an adult. As we have already seen, milk is, or should be, the sole diet of the ciiild up to the age of eight months, and in this food we have a diet which contains twice as much proteid and half again as much fltt as the adult diet referred to above. Some one has said that " The poorest mother in London or New York feeds her child as if he were a prince. Perhaps not once in a hundred times is the man as richlv fed as the young child, unless accident has made him a Gaucho, or study and reflection a gourmand." Having discussed food-stuffs, we will now turn our attention to some of the more common foods in which these occur. MILK. As already stated, milk is the sole food for the developing child during the early months of its existence, and indeed, as among the Eskimos, for a period extending into years. It is therefore a perfect food, inasmuch as it contains all that is needed for growth and the maintenance of the body in a physiologic con- dition. This is true for the early period of life, but not for the later, as it contains too little iron and too nnich proteid and fat, althouarh adults have lived for months on milk alone. Milk is au emulsion in which the globules of fat are sus- pended in a fluid, called milk-plasma. As in other emulsions, so here, the white color is due to reflection of light from the [rlobnles. It is now believed that the fat is not enclosed in a thin envelope of caseinogen, but that by molecular attraction each globule is covered by a closely adherent layer of milk-]->]asma. The diameter of the globules Varies from 0.0015 to 0.05 mm. HUM AX MILK. 139 The specific gravitv of butli cow.s' luul Imiimii milk is from 1028 to io;u. The reaction of milk varies in different classes of animals. In carnivora it is acid, but in most other animals it is cither slio;litly alkaline or neutral. Milk contains the following inirrcdients, the quantity varv- inu" in the milk of different ani- mals : ^^'ater, caseinogen, kictal- bumin, lactoglobulin, lactose, fat, extractives, as creatin, creatinin, hyj)oxanthin, cholesterin, and traces of urea, salts, and the gases oxygen, nitrogen, and car- bon anhydrid. Human Milk. — The first milk secreted by the mammary glands is colostrum (Fig. 86). It is a yellowish liquid, more alkaline than the milk secreted later in lactation, and contains very little caseinogen, sometimes none at all, but lactoglobulin and lactallnimin. The following table contains analyses by Clemm of human milk before and immediately after delivery : Fig. 86. — Colostrum and ordinary milk-globules, first day after labor; primipara aged nineteen (after Haskell). Constituents. Four weeks before delivery. Seventeen days be- fore delivery. 2 <2 0) *^ >i u M O >,> ^X a 85.85 14.15 3 >, 0) I. II. o Water .... Solids .... Casein .... 94.52 85.2 5.48 14.8 85.17 14.83 84.38 15.62 86.79 13.21 2.18 Albumin and Globulin . . Fat .... Lactose .... Salts 2.88 0.9 0.71 4.1 1.73 3.9 0.44 0.44 7.48 3.02 4.37 0.45 8.07 2.35 3.64 0.54 b.5l' 4.86 6.10 Lactoglobulin, M'hich is found in colostrum, exists in but very minute amount in milk fully formed. A comparison of the above analyses shows considerable varia- tion ; indeed, such variation is found in the milk of the two breasts of the same woman and in women of different ages. Some authorities attribute differences to complexion also. The salts of human milk are sodium lactate, chlorid, carbonate, 140 MILK. pho.sphate, and sulpliate ; potassium clilorid and sulphate; calcium carbonate and phosphate; magnesium phosphate; and ferric phos- phate. In the following table by Hallil)urton are given various analyses of fully formed hu'man milk : Water. Casein- Albu- ogen. min. Fat. Sugar. Salts. Remarks. Observers. 88.58 90.58 86.27 86.3) to y 88.8 j 89.1 87.24 89.29 89.06 87.79 3.69 2.91 2.95 1.68 to 3.15 1.79 1.9 1.6 1.72 2.53 3.53 3.34 5.37 (2.6 ■{ to (5.4 3.3 4.3 3.2 2.9 3.9 4.3 3.15 5.13 0.8 to 6.6 5.4 5.9 5.8 6.0 5.5 0.17 0.19 0.22 0.23) to \- 0.34 j 0.42 0.28 0.16 0.2 0.25 9 davs after delivery. 12 " Woman 20-30 years old. " 30-40 " \ Clemm. Tidy. Biel. Gerter. Christenn. I PfeifiFer. Mendus de Leon. Cows' Milk. — Tlie following analysis of cows' milk may be regarded as a sample of many analyses which have been recorded, and will enable a comparison to be made with human milk. Analysis of Cows' Milk. ^ Water 84.28 Solids 15.72 Caseinogen 3.57 Lactalbumin 0.75 Fat 6.47 Lactose 4.34 Salts 0.63 If a comparison is made, it will be seen that cows' milk con- tains more proteid, 4.32 as compared with 2 -f ; more fat, 6.47 to 8 or 4 ; and more salts ; but, on the other hand, less sugar, 4.34 to 5. It results from this that in substituting cows' milk for mother's milk in the feeding of infants the milk should be diluted and sugar added. In the consideration of the carbohydrates lactose or sugar of milk was discussed, so that here we need only refer to it. As we then learned, this variety does not undergo the alcoholic fermen- tation with yeast, but does with some other ferments. The fat of cows' milk is a mi.xture of palmitin, stearin, and olein, together with triglycerids of butyric, caproic, and other acids. It also contains lecithin, cholesterin, and a yellow lipochrome. The fats of human milk differ somewhat from those of cows' milk, but these diflPerences are not important. The proteids of milk are, as already stated, caseinogen, which is by far the most important, and lactall)umin and lactoglolyulin, which two are present in but minute quantities. Of caseinogen and its properties we have already spoken. COWS' MILK. 141 It is tliis con.stituont wliicli, when milk coagulates, becomes casein, fonning with lat the codcju/uin or curd; the liciuid j)ortion, which contains wiiey-proteid, lactalbumin, lactose, and salts, l)eing U'/teij. Cows' milk is a Huid which is very prone to nndergo fermen- tative changes ; one of these, the formation of lactic acid from lactose, has already been described ; but there are others, which are j)erhaps more harmful, being esj)ecially irritating to tiie delicate mucous membrane of the alimentary canal of the voung infant. These changes are brought about by various bacteria which lind their way into the milk at the dairy, where the milk is produced, or subsequently, either during transportation or after it has been delivered to the customer. Great pains should be taken to keep the surroundings of dairy and home in a cleanly condition. Milk may be the transmitter of specific disease if taken from a diseased animal — as, for instance, one suffering from tubercu- losis ; and it may also become infected after coming from the cow and before it is used as food. Numerous epidemics of enteric or typhoid fever have been traced to infection of the milk-supplv by polluted water used either to dilute the milk or to wash the cans which contained it ; scarlet fever, also, has been contracted by those who have drunk milk which had become infected by the hands of milkers who were recovering from the disease. Diph- theria has also been transmitted through infected milk. In order to prevent the fermentation of milk, the bacteria con- tained in it should be destroyed. This may be done either by sterilization or pasteurization. Sterilization consists in heating the milk to 100° C, the boiling- point, by which the milk becomes "sterile" — that is, all organisms which would produce fermentative changes in the milk are killed. The objections to this process are that the taste of the milk is altered to that of boiled milk, the casein is not so easily digested, the emulsification of the fat and its absorption are not so readily brought about, and the amylolytic enzyme is destroyed. If the exposure to the heat continues too long, the milk becomes brown- ish in color, due to the conversion of lactose into caramel. In pasteurization the milk is exposed to a temperature of only 71° C. to 76° C. for fifteen to twenty minutes; milk thus treated is not changed as in sterilization, but will keep only a short time — a day or two. Human milk is the product of the mammary glands, the structure of which may here be concisely described. 142 MA MMAE Y GLA NDS. MAMMARY GLANDS. The mammarv glands or mammte (Fig. 87) are two in number, situated one in each pectoral region. They are compound racemose glands, and consist of gland-tissue which is made up of lobes, and these again of lobules (Fig. 88). The lobes are connected by fibrous tissue, and between them is fat. Each lobule is composed of sacculated alveoli and a duct, the lobular duct. The lobular ducts discharge into larger ducts, which in turn discharge into a lactiferous duct, which may l)e regarded as the excretory duct of a lobe. Of these ducts, tubuli lactiferi, there are from fifteen to Fig. 87. — Arrangemeut of glandular tissue of breast, the fat having been removed to show the ducts and acini ( Astley Cooper). twenty. They open at the surface of the prominent point of the breast, the mammilla or nipple, surrounding which is the areola, which in the virgin is of a ])inkish color, becoming darker during pregnancy and almost black at its termination. Under the areola the tubuli lactiferi are dilated, forming ampullce, in which, during the period of lactation, the milk accumulates in the intervals of nursing. When these reservoirs are full the tension of the gland stops the process until they are emptied by the sucking child, when the cells again take on their function and the milk is secreted and flows into the ampullae through the ducts, there to accumulate until the next nursing. MAMMAIiV a LANDS. 143 Tlic walls of the alveoli consist of a bascment-memhrane, covered, (liirin»i; the ])erio(l when the gland is not active, bv a single laver of Hat or ciihoidal cells (Fig. 90) with one nnclens and presenting'- a grannlar aj)pearance. There are at this time no fat- o-lobules. When, however, the gland begins to take on an active Clavicle— irst rib. Lesser pectoral muscle. Intercostal mus- cles. Greater pectoral muscle. Integument Fibrous septa con nected with in- tegument. Glandular tissue.- Mass of adipi tissue. Areola. Interlobular adi- pose tissue. N'ipple.-/ Lactiferous duct._ Ampulla.— Interlobular adi pose tissue. Glandular tissue — Peripheral acini Mass of adipo: tissue. Fibrous septa Integument Superficial fas- cia. i^'i;. Horizontal axis of nipple. _ Fifth rib. Sixth rib. External oblique muscle.- • Fig. 88.— Longitudinal section of mammary gland hi situ; frozen subject of twenty- years (Testut). condition (Fig. 91) these cells become higher and project into the interior of the alveoli, and the single nucleus divides, thus becom- ing two. In the cytoplasm drops of fat appear, especially at the ends of the cells nearest the interior of the alveoli, and at the same time the nucleus which is nearer to this end of the cell becomes fattv. This end of the cell then breaks down, and the 144 MAMMAin' G7..L\7>.V. material forms the albuminous ingredients of the milk and the lactose, while the drops of fat become the milk-globules. The ^;- ^'-. -A! veolus. ■'-i'j'''°'/^"'-~""5'J'v-f -. ""'1 "' 1 ■ ^' ■ .V-~pConnective- "'^ " J tissue i-.f^:::S <-.r' .•■'.i.----'i4l VV-~t '^'t^"'.J3' >---'i'''f alveoli. Adipose tissue. Fig. 89. — From section of mammary gland of nullipara (from Xagel's "Dieweib- licben Geschlechtsorgane,"' in Handhuch der Anatomie des Menschen. 1896). portion of the cell which remains forms new cytoplasm, and the same process is repeated over and over again. The cells also secrete water and the salts which are found in the milk. Fig. 90. — Section through the middle of two alveoli of the mammary gland of the dog; condition of rest (after Heidenhain). There is some difference of opinion as to the origin of the corpuscles found in the colostrum, and which are known as EG as. 145 colostnun-corpur^clos. One view is that they aro cpitlielial colls c)t" the alveoli, whieh heeoine nmmled and in whieh fat is devel- oped, and that in this condition they become detachetl and are discharged into the cavity of the alveolus. Another view is that they are emigrated lymph-corpuscles; while still a third regards them as derived from the wandering cells of the connective tissue. When the period of lactation is over the glands retnrn approxi- matelv to their original condition, thus undergoing the process of inro/tdioii. That the secretion of milk is under the control of the nervous system there is no doubt, for the instances are numerous in which strong emotions of grief or anger have caused the secretion to cease, but just what the relation is remains still undecided. It A B Fi<4. 91. — Matamary gland of dog, showing the formation of the secretion : A, medium condition of growth of the epithelial cells; B, a later condition (after Heidenhain). mav be that secretory nerves are involved in the activity of these glands, or that it is through the influence of vasomotor fibers that their secretion is produced ; but exjwrimeuts have as yet not de- termined tiie question. That the glands may act automatically is proved by the fact that when all the nerves which supply them are divided, the secretion still continues to be formed. The table on page 146 gives the composition of milk and other food-materials, together with their nutritive value. It is from one of the Fanners' Bullefinx, " Milk as Food," issued by the United States Department of Agriculture. Incidentally we Avould call attention to these publications, which are issued free or at a nominal cost by the Government, and are full of practical value, not alone to farmers, but to all students of economics. EGGS. Eggs in various forms enter largely into the common dietary. So far as birds are concerned, eggs may be regarded as a perfect food, inasmuch as until the young leaves the shell all its nutrition has been obtained from the shell and its contents, together with what it has obtained from the atmosphere. The es:g of the hen is the one commonly used as food, although 10 146 iJGGS. COMPOSITION OF MILK AND OTHEE FOOD-MATEEIALS. Nutritive ingredients, refuse, and fuel-value. Nutrieuts. Non-uutrients. Wdiur. Kcluae. C^ilories. Carbu- M.UL-rul hydrates, itiuiiers. Protein compouuds, e. g., lean of meat, white of egg, caseiu (curd) of milk, aud gluten of wheat, make muscle, blood, bone, etc. Fats, e. f/., fat of meat, butter, and oil, ) serve as fuel to yield heat aud muscular Carbohydrates, e. g., starch and sugar, J power. MEAT. 147 diu'ks' e<2;i>s arc oaten to a c()nsi(l('ral)l(' oxtciit. In a lien's e<;^ weiiiliiny,- 50 y,ninis there are 7 i;i'aius of shell, 27 tiraiiis ot" the whiti', and 16 grams of yolk. The volk aiiv some, but the evidence in its favor seems couflusive to the author. This may not be directly due to the ingestion of the meat itself — that is to say, the muscular tissue may not contain the bacilli — but to the tuberculous matter from glands with which in the cut- ting of the meat the butcher smears it. The Bacillus fuherculosis is killed in a few minutes at a temperature of 100° C, the boiling- point, in five minutes at 80° ('., and in four hours at 55° C, but the bacillus itself must be exposed to these temperatures. Ex- periment has demonstrated that in ordinary cooking, both l)y boiling and roasting, the temperature in the interior of the joint of meat, unless it is under six jiounds in weight, seldom reaches 60° C. ; and that rolled meat, in the center of which is tul)er- culous matter, is not sterilized by any process of cooking if it is over four pounds in Aveight. It follows from this that the greatest care and sui)ervision should be exercised by health author- ities at the slaughter-house, so as to ])revent the possibility of infected meat finding its wav into the market. To minimize still further the danger, all meat which may contain infection should be thoroughly cooked. The cysticerci which develop ta])eworm in man are not destroyed by the simple processes of salting and smoking, so that for their destruction meat should be ex])osed to a temperature of at least 66° C, while for the destruction of the trichina the temperature should be even higher, say 70° C, inasmuch as the trichina is enclosed in a capsule which serves as an obstacle to the entrance of heat. The common methods of cooking meat are, roasting, boiling, broiling, and frying. These all have their proper places, but should be employed with discrimination. In roasting, the meat is exposed to a great heat, so as to coagulate the ]iroteids on the surface in as short a time as possible, thus retaining the juices of the meat in the interior. The temperature is then reduced to CEREALS. 149 93° C. or 88° C., and maintained at that point, the general rule beini tough. Thi.s temperatnre i.s high enongh to cook thoroughly the whole pieee, hut not roiling i.s allied to the proce.s.s of roa.sting. In boiling meat the same object !.•=; accomplished by ])lunging it into boiling water, which coagulates the exterior as in the roasting ])rocess. If, however, the object to be attained is to make sou|) or broth, then the meat, having been cut into small pieces, is placed for .some time in cold water and the temperature gradually raised to 71° C. By thi.s treatment the juices of the meat are extracted and the soluble parts are dissolved out from the meat, before the heat has time to coagulate the proteid. It should be remembered, however, that such souj)s are not very nutritious, but are stimulating. They contain very little proteid or fat, iiut do contain .-alts and the ex- tractives of muscles, such as creatin, creatiniu, etc. It is for the reasons thus given that beef-tea is of little value as food. If vegetables are added to meat-extracts, making a vegetable soup, the nutritive value is correspondinglv increased. If bones are u.sed in the soup-making process, the amount of gelatin is in- creased to such an extent, indeed, that when cold the soup gelatin- izes and becomes solid. Frying is a method of cooking which should never be applied to meat such as beef, as it makes it indigestible by rea.son of its toughness, and al.^o by reason of the fat with which it becomes soaked. If meats are fried by immersion in boiling fat, the process is not so objectionable; but the fat should not l)e allowed to permeate the ti.ssue, as it would do if the process was continued too long. Frying is well adapted to the cooking of fish. CEREALS. The cereals are the farinaceous seeds used as food, such as wheat, Indian corn or maize, rice, rye, oats, and barley. They all contain ])roteids, fat, starch, and mineral salts, though the pro- portion of these ingredients varies considerably in the different cereals, as is shown by the following table (Halliburton) : Rice. Constituents. Wheat. Barley. Oats. i Water Proteid Fat 13.6 12.4 1.4 67.9 2.5 1.8 13.8 11.1 2.2 64.9 5.3 2.7 13.4 10.4 5.2 : Starch Cellulo.?e Mineral Salts .... 57.8 11.2 3.0 13.1 7.9 0.9 76.5 0.6 1.0 The proteids in the flour of cereals are not identical. Some writers regard those in wheat-tlour as being a vegetable myosin 150 CEREALS. and a soluble proteose called phvtulbiimose. Gluten, which is considered by some autiiorities as a proteid constituent of wheat, is regarded by others as a mixture of" gluten-fibrin, which is formed from the vegetable myosin, and a proteose insoluble in water, wliich is formed from the phytalbumose, and which gives to the gluten its sticky consistency. According to this theory, the gluten as such does not exist until water is added, when by the action of an enzyme gluten is produced. This enzyme has, how- ever, never been isolated, and until this theory is better sustained by proofs we shall regard gluten as a constituent of wheat-flour. The proteids of oats are three in number : One soluble in alcohol, one a globulin, and the third a proteid soluble in alkali. In maize there are two globulins, one a vitellin and the other a myosin; one or more albumins; and zein, a proteid soluble in alcohol. The proteids of rye are gliadin, leucosin, edestin, and proteose ; and those of barley are leukosin,' proteose, edestin, and hordein. The cereal most commonly used is, perhaps, wheat, the flour of Avhich is made into bread. Bread. — The cereal most used for bread-making is wheat, though bread is also made from rye and cornmeal. Wheat-flour contains approximately 14 per cent, of water, 12 of proteids, and 70 of carbohydrates. The amount of fat and salts is small. In the making of flour the wheat-grains are ground, and the result IS sifted, or " bolted '' as it is termed, into fine flour, coarse flour, and bran. The bran is the extreme outer covering of the grain, and is so tough and silicious that it is of no nutritiye value, while the other coyerings contain so much of proteid, fat, and salts as to give them considerable food-value. The process of making flour just descril)ed is known as the old process, and results in heating the flour, which, if not properly cooled, is liable to spoil. In the neiv process the grains are cut with knives or crushed between iron rollers which do not produce heat. Flour is made by another process, in which the grains are moistened and the extreme outer covering or husks removed by rubbing. The grains after being dried are exposed to blasts of air which have force enough to thor- oughly disintegrate them. When pidyerized this is known as ir hole-wheat flour, and contains all that is nutritive in the wheat. In making l)read the flour is moistened with water or milk to which yeast has been added, and when thoroughly mixed this becomes dough. Salt is also added, and some breadmakers add sugar and butter as well. After thorouo:h kneadinc:, the dough is exposed to a temperature of al)out 24° C The starch is con- verted by an enzyme Avhich exists in the wheat into dextrin and sugar, and this, inider the iufluence of the yeast, then undergoes the alcoholic fermentation, alcohol and carbonic-acid gas resulting. This gas rises up through the dough, expanding it to more than VEUKTA BLK 1 'HOT EI US. 1 51 (loiil)l(' its ()ri<>iii:il vuliiiiio, inakiner cent, of proteid and 54.8 ])er cent, of starch. The ]>ro- teids of the pulses are of the nature of vitellin and globulin. lu the kidney-bean two globulins, phascolin and phaselin, besides proteose have been found. Vegetable Proteids. — The proteids in vegetables may exist in three forms : ( 1 ) In solution in the juices of the plant; (2) in the protoplasm ; or (3) in aleurone grains. They are classified, as are the animal proteids, into albumins, globulins, albuminates, pro- teoses and peptones, and coagulated proteids. ^^'hat was formerly spoken of as legumin or vegetable casein, or simply vegetable proteid, is now held to be an alkali-albumin produced by the action of the alkali used iiLthe extraction on the globulins which exist normally in the plant. Proteoses have been found in the various varieties of flour, as well as in the circulating fluids of plants, and in the latter also occur hemi-albnmose, leucin, tyrosin, and asjiaragin. Enzymes also exist in plants, and to those of a proteolytic character these proteoses are probably due. Some of these proteolytic enzymes have been carefully investigated, notal)lv ]>a])ain in the papaw plant, and bronielin in ]iineapple- juice. In the juice of the papaw are a number of proteids: a globulin resembling serum-globulin, an albumin, and two pro- teoses, with one of which papain is associated. This enzyme is verv much like trypsin. Bronielin acts in neutral, acid, or alkaline media, acting particu- larly well at 60° C. It produces proteoses and jieptones, and is used to prepare artificially digested foods. Enzvmes are verv abundant in the vegetable kingdom, and 152 BEVERAGES. have for their office the conversion of tlie insohihle protcid of the seed into the soluble nitrogenous substances of the sap. They are, however, not all of a proteolytic nature. There are also tiiose that are amylolytic, as the diastase in barley, and these enzymes change the starch of seeds into sugar. Such a conversion we have already referred to in the process of bread-making when the wheat- starch first becomes sugar, and then undergoes alcoholic fermenta- tion under the influence of yeast. The nutritious value of fruits is not to be overlooked. When fresh and ripe they are easily digested, and serve besides a useful purpose in keeping the bowels in regular action. BEVERAGES. Under this general head are included tea, coffee, cocoa, and alcoholic beverages. Some of these have a distinct food-value, others are stimulants only, while the opinions held by authorities as to some of the others are so diverse and the results of experi- ments so differently interpreted, that it is difficult with our present knowledge to classifv them with precision. Tea. — Tea is an infusion made from the leaves or leaf-l)uds of the tea plant, the principal constituents of which are an aro- matic oil, an alkaloid, thein (QHi^iN^O^ ) 1.8 per cent., tannin about 15 per cent., albuminous compounds, dextrin, and salts con- taining potash and phosphoric acid. Tea is a stinudant by virtue of the thein which it contains, and an astringent because of the presence of tannin. Tea should be made with boiling water, and in al>out five minutes the infusion should be poured into another vessel ; if left longer, it becomes bitter and unwholesome because of the large amount of tannin dissolved. Coffee. — This beverage is an infusion made from the seeds of the coffee plant. The seeds or berries contain fat, legumin or vegetable casein, sugar, dextrin, salts, an aromatic oil, and an alka- loid caffein (CgH,yX^02) about 0.75 per cent., and caffi-o-tannic or caffeic acid, a variety of tannic acid. Thein and caff to 6 })er cent, of" alcohol by volume ; although there is here, as in the distilled beverages, a great variation. They also contain dextrin, sugar, lupulin, free organic acids, and salts. The following table gives the percentages of alcohol and solid matter or extract in some of the common beers and ales (Allen) : Alcohol. Solid matter or extract. Munich Lasjer 4.75 3.55 2.78 6.25 0.37 6.66 7 08 Pilsen Lager American Lager (average of 19 sample:-; Bass's Pale Ale 5.15 6.05 6.98 Alsops Pale Ale 4.44 Guinness's Stout 7.24 Value of Alcoholic Beverages as Food. — It will be seen that by virtue of the carbohydrates and salts -which wines and beers con- tain they certainly have a food-value entirely irrespective of the alcohol, which is also one of their constituents. The compound ethers are regarded as assisting digestion by promoting the secre- tion of the digestive fluids, Avhile the bitter principles are well- recognized stomachic tonics. U.sed in moderation they are there- fore not injurious, but used to excess there is danger of their producing fat in excess, imperfect oxidation, and a resulting plethoric and perhaps gouty diathesis. EFFECTS OF ALCOHOL UPON THE HUMAN BODY. We come now to consider a suljjeet al)0ut m hieh volumes have been written, and one which has, perhaps, excited more discussion in both scientific and lay organizations than any other — /, e., the effects of alcohol upon the human body. The warfare has raged long and fierce around the question, "Is alcohol a food?" In a discussion of any subject it is very important that there should be no misunderstanding about the meaning of the terms employed, and, therefore, Ixi'fore entering upon this discussion we must have a distinct understanding as to wliat is meant by a food. For this purpose w^e quote the following definitions : Definitions of Food. — '^ That which is eaten or drunk for nourishment ; aliment ; nutriment in the scientific sense ; any substance that, l)eing taken into the body of animal or plant, serves, through organic action, to l)uil(l up normal structure or supplv the waste of tissue ; nutriment, as distinguished from condiment." — Standard Dictiovftrj/. " Anvthing which, when taken into the body, serves to nourish or build up the ti.ssues or to supply heat." — Dorkind''H Jlbisfrafed Medical Dictionary. " Any substance, inorganic or organic, solid or li(|uid, that will lyFLVEyCE OF ALCOHOL UPON OASTlllC 1)1(1 LSTIOy. 155 nourisli the IxkIv, renew the materials eonsmned iti pHxhicinj^ those I'oriiis of I'uerjiy ealletl vital." — ('ha[)mairs Jlnman I'liytii- olo(/!i. " The use of food is to repair the waste of the tissues, and through eonibustion in the economy to liberate energy." — IbuL These (juotatious might be increased iudetinitely, but th(jse given will answer our purpose. A food serves one or more of f(»ur purj)()ses: 1. To build up normal structure; 2. To diminish the waste of tissue ; 3. To supply the waste of tissue ; 4. Through combustion (oxidation) to liberate energy. Any substance, there- fore, which performs any one or more of these four offices is a food. It may do it to a considerable extent, and consequently have great food-value ; or it may do it to but a slight extent, and have but little food-value ; but in so far as it does it at all it is a food. Influence of Alcohol upon Secretion of Saliva. — When strong alcohol or an alcoholic beverage is taken into the mouth there is produced an increase in the secretion of saliva, not only as to volume, but also as to its organic and inorganic constituents. The same effect is produced by vinegar, ether-vapor, and other similar substances. This stimulating effect, however, lasts only while the liquid is in the mouth. Alcohol in the stomach has no effect upon the secretion of saliva. Influence of Alcohol upon Secretion of Gastric Juice. — The evid(>nce is overwhelming that alcohol, Avhether taken as alcohol or in the form of alcoholic beverages, such as whiskey, wine, or beer, increases the amount of gastric juice se- creted, and that this is more acid and contains more of its normal constituents. The action of this gastric juice upon proteids is also very pronounced. That this is not entirely due to direct stimidation of the glands of the stomach by the alcohol is shown by the fact that when alcohol is introduced into the small intes- tine, and then this latter is ligated so that none of the alcohol can enter the stomach, an increased secretion of gastric juice is still ])roduced. It is as yet not determined just how this is brought about, whether by action on the cells of the gastric glands through the medium of the blood, or upon secretory nerve-fibers. It is to be borne in mind that other constituents than alcohol are to be found in wines and malted liquors ; and experiments show that these, especially the organic acids, produce also a stimu- lating effect upon the gastric glands, so that the alcohol is not the only factor concerned in causing increased secretion and aciditv. Influence of Alcohol upon Gastric Digestion. — in a paper on " Influence of Alcoholic Drinks upon Digestion," by Chittenden, Mendel, and Jackson, published in the American Journal of Pln/siolor/i/, and to which we are indebted for much information, is a synopsis of the opinions and results of experiments 156 EFFECTS OF ALCOHOL UPON THE HUMAN BODY. of different physiologists on this part of the subject. Kretschy observed in a woman with gastric fistula that alcohol retarded digestion. Buchner found that in the human stomach alcohol, wine, and beer retarded digestion, but less so than in artificial digestion. Bikfavi observed in dogs a retardation of digestion with even small quantities of alcohol. Beer and wine showed no favorable influence, the latter retarding digestion in large quanti- ties. Ogata states that beer, wine, and l)randy retard digestion noticeably. Schelhaas observed that in the living stomach wine did not retard digestion so long as there was free HCl present. Gluzinski found that alcohol retarded proteid digestion and brought about the secretion of a very active, strongly acid gastric juice. Henczincki observed no bad effect on digestion with the use of beer. Blumenau found that 25-50 per cent, alcohol dimin- ishes stomach digestion during the first two or three hours. AVolff- hardt observed in a healthy man that 15—20 grams of absolute alcohol interfered with proteid digestion ; that the effect of cognac varied with the period of digestion during which it was taken ; and that wines tended to promote digestion. Brunton states that alcohol increases the movements and the secretion of the stomach, and by mixing its contents more thoroughly with gastric juice accelerates digestion. Gluzinski on the other hand, finds that alcohol diminishes the mechanical action of the stomach to a moderate degree. Chittenden and his associates experimented upon a dog to ascer- tain the effect of alcohol upon (1) variations in acidity and (2) time of digestion. The results are very interesting and in- structive. In these experiments 50 grams of meat were given in each, sometimes alone, sometimes with water, and sometimes with alcohol of varying strengths, and sometimes with various alcoholic beverages. AVhen meat alone was given the stomach was empty (end of gastric digestion) in 2 hours and 55 minutes. When water was given with the meat, the time of digestion varied from 2 hours and 15 minutes to 3 hours; an average of 2 hours and 40 minutes. With alcohol, varying from 22 to 30 per cent., the time was froui 3 hours to 3 hours and 45 minutes ; average, 3 hours and 20 minutes. With weak alcoholic beverages, wine and beer, the time of digestion was from 3 hours to 3 hours and 15 minutes; average, 3 hours and 10 minutes. With strong alcoholic beverages, it was with whiskey, 2 hours in one experiment and 3 hours in another ; Avith gin, 3 hours ; with brandy, 2 hours and 40 minutes ; an average of 2 hours and 40 minutes. The conclusions to be drawn from these experiments would seem to be that alcohol does not retard proteid digestion to any great degree ; taking the set of experiments quoted in connection with another set, there is a slight retardation, and that more marked with malted beverages. ABSORPTION OF ALCOHOL FROM THE STOMACH. 157 Inasimicli, however, as wc liavo already seen, an increased amount of an active s>:a.stric juice is produced by the alcohol, it is more than proUahle that tliis makes up for any retardation in the pro- teolytic ])rocesses. The great care with which these experiments of Chittenden and ins associates have been made seems to the writer to entitle their conclusions to great consideration, which may be briefly summed up in the statement that " gastric digestion in the broad- est sense is not markedly varied under the influence of alcohol or alcoholic fluids. This conclusion, it may be mentioned, stands in perfect harmony with the results of the investigations of Zuntz and ]Magnus-Lenz regarding the influence of alcohol (beer) on the digestibility and utilization of food in the body. These investi- gators found by a series of metabolic experiments on men with diets largely made up of milk and bread, and on individuals accustomed and unaccustomed to the use of alcoholic beverages, that the latter did not in any way diminish the utilization of the food by the body." Absorption of Alcohol from the Stomach. — Chittenden's experiments, in which 200 c.c. of 37 per cent, alcohol were intro- duced into the stomach of a dog with the duodenum ligated at the pylorus, resulted in the com])lete disappearance of the alcohol in 3-3^ hours by absorption through the stomach-walls into the blood. When tlie intestine is open the absorption is more rapid. When 6-8 grams of alcohol, as wine or beer, are taken into the stomach, 80-90 per cent, will have disappeared from the aliment- ary tract witliin ^ hour. In one of Chittenden's experiments 50 c.c. of 20 per cent, alcohol were absorbed within ^ hour. His conclusion is that, " in view of this rapid disappearance of alcohol from the alimentary tract, it is plain that alcoholic fluids cannot have much, if any, direct influence upon the secretion of either pancreatic or intestinal juice." We have seen that wdien alcohol is taken into the stomach it produces an increased secretion of an active gastric juice. When this stimulation is excessive changes are set up in the raucous membrane, as a result of Avhich the gland tissue becomes less, and the secretion is correspondinglv diminished. Up to the point where the stimulation resulting in increase of the normal secre- tion ends and the pathologic changes begin, alcohol is not in- jurious, but manifestly in health no such artificial stimulus is needed. So long as the individual is well, the natural food is a sufficient stimulus to the gastric glands and the additional stimu- lation of alcohol is uncalled for, and inasmuch as the exact line of demarcation between the amount of alcohol that does good and that wdiich does harm has not as yet been absolutely determined, there is always a possibility that an excess may be taken and in- jury result. So far as the stomach is concerned, then, there is in 158 EFFECTS OF ALCOHOL UPON THE HUMAN BODY. a condition of healtli no useful purpose served bv alcohol, but there are conditions in which this property of alcohol of exciting the ga.-^tric glands to increased activity may be availed of under medical advice. Alcohol being a very diifusible substance, is mostlv absorbed bv the blood-vessels of the stomach, which carry it into the portal vein, and by this channel it reaches the liver, where its stimulating action is again exercised upon the cells of that organ, and an in- creased production of bile is the result. If, however, this stinui- lation is excessive and long continued, degenerative changes take place by which the organ ultimately becomes diminished in size and incapable of performing its function. From the liver the blood carries the alcohol to the heart, which is quickened in action, and to the brain, Avhose activity is also in- creased. If the quantity of alcohol is excessive, the cells of gray matter in the brain are over-stimulated and great excitement re- sults, and this may, if the quantity is sufficient, result in a suspen- sion of the functions of the brain and a condition of unconscious- ness, passing on in extreme cases to a fatal termination. But if the quantity of alcohol which reaches the brain is not enough to produce the fatal result, I)ut still enough to maintain the condition of over-stimulation, there result changes in the structure of the brain, as there do in that of the stomach and liver, which weaken the mental activities and produce the irregular and inco-ordinated muscular movements so familiar to all who have observed m- dividuals who have for years been addicted to drink. From this necessarily incomplete recital of the effects of alcohol we now turn to some experimental evidence bearing upon the subject. These experiments have been carried on by various experimenters, and some of the results are well summarized in the following quotation from An American Text-Book of PIn/siolof/i/ under the title " Alcohol in the Body." Alcohol " promotes the al)>orption of accompanying substances (sugar, peptone, potassium iodid), and stimulates the flow of the gastric juice. In this matter it acts as do other condiments (salt, pej^per, mustard, peppermint), but if there be too great an irritation of the mucous membrane there is less activity (dyspepsia). The rapid absorption gives to alcohol its quick recuperative eifect after collapse, and its value in administering drugs, especially antidotes. Alcoholic beverages coml)ining alcohol and flavor promote gastric digestion and absorp- tion, but often stimulate the appetite in excess of normal require- ments. Alcohol is burned in the body, but may also be found in the breath, perspiration, urine, and milk. Alcohol has no effect on proteid decomposition, but acts to sjiare flit from combustion. The addition of 50 to 80 grams of alcohol to the food has no apparent eifect on the nitrogenous equilibrium. Alcohol in the body acts as a paralyzant on certain portions of the brain, destroy- ABSOIU'TIOS OF ALrnlluL IVJJM THE STUMACII. 109 ing tlie more (k-licatc degrees of attention, judgment, and reflec- tive thought, diMiinial account of the ex])eriments was given at a meeting of the Middletown Seientilic Association, June l.j, 1899. This epitomized the results of experiments carried on with men in the respiration-calorimeter. An abstract of the statements M'as published in the Outlook (Xew York), July 29. "The details of some of the experiments have been given in Bulletin Xo. 69, of tlie Office of Experiment Stations of the United States Department of Agriculture. This may be had by application to the Secretary of Agriculture, Washington, D. C. This bulletin, however, does not treat the experiments from the s])eeial standpoint of the nutritive value of alcohol. An account of the inquiry from that standpoint will be pul)lished later by the Committee of Fifty for the Investigation of the Drink Problem, under whose auspices the experiments were made." AVe are indebted to the Outlook for the following details of Prof. Atwater's experiments : The respiration-calorimeter is a chamber in which the man experimented upon sojourns. It is about 7 ieet long, 4 feet wide, and 6J feet high, and contains a fol(lin(r-])ed, chair, and table, besides a stationary bicycle for experiments on muscular work. This chamber is well ventilated, lighted, and heated, and so arranged in all jiositions as to enable the conditions to be as nearly as possible similar to those under which human beings live who are properly fed and housed. All of the food, drink, and excretory j)r()ducts, even the air which the man breathes, are measured and analyzed with the greatest accuracy, as are likewise measured the potential energy or latent force of the food which the body receives, 160 EFFECTS OF ALCOHOL UPON THE HUMAN BODY. and the eiier<2:y which the body gives oft' in the forms of muscular work and heat. These experiments have, as Prof. Atwater be- lieves, "demonstrated tiiat the human body, like any other machine — -a steam-engine or an electric dynamo, for instance — obeys the law of the conservation of energy." In the experiments reported upon, jiure alcohol was adminis- tered with water or coft'ee. Other exjK'riments with alcohol in the form of whiskey, brandy, beer, and wine will be reported later by Prof, Atwater. The amount of absolute alcohol given daily was about two and one-half ounces, or "about as much as would be contained in three average glasses of whiskey or in a bottle of claret or Rhine wine." The alcohol given was divided into six doses — three given with meals and three between meals — the object being to avoid any special influence of the alcohol upon the nerves, and thus test its action as food under normal bodily conditions. Without dwell- ing further upon the details of the experiments, we will quote the residts : " First, extremely little of the alcohol was given off" from the bodv tuicousumed ; indeed, it was oxidized — /. e., burned as com- pletely as bread, meat, or any other food. Second, in the oxida- tion all of the potential energy of the alcohol was transformed into heat or muscular power. In other words, the body made the same use of the energy of alcohol as of that of sugar, starch, and other ordinary food-materials. Third, the alcohol ])rotected the material of the body from consum})tion just as effectively as the corresponding amounts of sugar and starch : that is to say, whether the body was at rest or at work it held its own just as well with the one as the other." In these experiments the unconsuraed alcohol was found to be passed out from the body through the kidneys, lungs, and skin, and this amounted to about 2 ])er cent, of the amount taken. Aldehyde and acetic acid, products of the partial oxidaticm of alcohol, were not found ; Init 98 per cent, of the amount taken in — /. c, all but that passed off" unconsumed — was burned completely to carbonic acid and water. The amount of energy which was latent in the alcohol reap- peared and was measured in the heat given off" from the man's body and in the work he performed, so that in this respect alcohol is not different from fat or sugar or starch. One of the important questions which these experiments have determined is that the body actually gets the benefit which comes from the oxidation of the alcohol. When the subject of the experiment was doing no muscular work he was supplied with just enough food without alcohol to enable him to " hold his own" — /. e., he showed no consi(leral)le gain or loss in weight ; then the fat, sugar, and starch were reduced in amount and alcohol substi- tuted for that taken away, and the body showed no gain or loss — ABSonrriuy of alcohol from tiu: stomach. IGI in other words, the aleohol kept tlie body from wasting just as the tat and earl)oh yd rates did. M'hen the man was doing mus- cular work the (piantity of tootl was increased because more energy was needed ; hut in this case alcohol was sul)Stituted as before, and with like result — i.e., alcohol supplied the additional energy as well as the fat and carbohydrates. One of the important (piestions in connection with the effects of alcohol on the human body is that connected with the body- temperature. In answer to an inquiry from the author on this point, Prof. Atwater writes: ''Our experimeuts thus far liave not shown any specific effect of alcohol, in the quantities used, upon body-temperature. That is to say, the temperature of the bodies of tlie men under experiment was measured by mercury thermom- eters in the mouth in the ordinary way, and the average results in the periods in which alcohol has made a part of the diet have not differed sufficiently from those in the corresponding j)eriods in which alcohol was not used to warrant, in our judguient, any general conclusion as to the effect of alcohol upon body- temperature. The residts of observations elsewhere are, as you know, numerous and more or less conflicting. It seems tons that before venturing any generalizations we ought to attempt to secure a considerable number of data by more accurate methods of measurement of body-temperature, and we are making plans accordingly." If, with the results of these experiments in mind, we now turn back to the definition of food, we shall see that alcohol is a food. We have dwelt to a considerable extent upon this sul)iect for the reason that many of the text-l)ooks used in the grammar and high- schools of the country deal with the effects of alcohol upon the liuman body by reason of laws which have been enacted requiring them so to do. Unfortunately, many of these books do not repre- sent the physiologic facts as we believe them to be. The ten- dency of these l)ooks, to say the least, is to teach that alcohol is not a food, but a poison. That it is a food we think has been abundantly proved ; that it is a poison is also true, but whether it is the one or the other depends upon the amount taken. There are many things which, in certain quantities, are not only not harmful, but are absolutely essential. The process of stomach digestion requires that the gastric juice should contain hydrochloric acid, and normally this is jiresent to the amount of 0.2 per cent., and yet given in a sufficiently large quantity it would produce death. The experiments of Prof. Atwater ami his colleagues mark a new era in the historv of this most iuiportant subject, the effect of alcohol upon the human l)ody ; and in all future discussions arguments shoidd not be based upon the experiments Avhich pre- ceded theirs, unless they were conducted with similar precautions. 11 III. NUTRITIVE FUNCTIONS. DIGESTION. Having considered the conipositi(jn of the body and food, there may now be taken u]) tlie study of the nutritive functions. As has been noted already, the body is constantly producing energy and undergoing icaste, both of which require the taking of food. But food is of absolutelv no use to the body until it reaches the blood and Ijy this fluid is conveyed to the tissues. So long as the food remains within the alimentary canal it is as much out- side the body, so far as nutrition is concerned, as if it had never been taken inside. To be of any service the food must enter the blood, and it does this by being absorbed. In some forms of animal life the food is of such a nature that it readily and without further change undergoes absorption — that is, passes tiirough the walls of the aljs;estive organs. If the n-cjuisite ehanlex. Such is the character of the food of man, and, con.sequently, such is the character of his digestive apparatus (Fig. 92). The human digestive apparatus consists of the a/imentari/ canal and the other (Jir/rstive orgauf^, which, although outside, still com- municate with this canal by ducts through which their secretion 164 MOUTH DIGESTION. is poured. The alimentary canal consists of the mouth, the esopha- gus, the stomach, and the small intestine. Tlie digestive organs which are outside, but which discharge their secretion into this canal, are the salivary glands, the liver, and tiie pancreas. The digestive process is subdivided into three parts : That which takes place in the mouth — mouth digestion; that which takes place in the stomach — stomach or gastric digestion ; and that which takes place in the small intestine — intestinal digestion. For- merly, when digestion was spoken of it was always stomach diges- tion which was referred to, because it was supposed that the entire process took place in that organ ; and when digestion was impaired the remedies which physicians employed were directed to the stomach alone. There is, unfortunately, too much of this kind of practice even now ; but the study of physiology has taught that indigestion may be due quite as much to the improper per- formance of mouth and intestinal digestion as to tiiat which takes place in the stomach, and unless this is recognized many cases will be unsuccessfully treated. When food is taken into the mouth it has, presumably, been as fully prepared as possible by the removal of those portions which are of no nutritive value. No one eats the husks of corn, the shells of nuts, the gristle of meat, or similar sul^stances, be- cause experience has shown that they are of little or no nutritive value, and that their digestion is practically impossil)le. Such extraneous matters, therefore, are removed, and the food is further prepared, provided this preparation is necessary, by the process of cooking. In the form, then, in which the food is taken in it is as fully prepared as it can be outside the body. Whatever remains to be done in order that the food may be ])repared for absorption must be effected after it enters the alimentary canal. Some of the ingredients of human food are already in a con- dition to be absorbed by the blood-vessels of the alimentary canal, and therefore they need to undergo no change. Such ingredients are water, salts, and dextrose ; and were they tlie only constituents of the food, no digestive organs would be needed ; but, as already said, this is not the fact. The greater part of the food must be changed l)efore it can be absorbed. The first step in this conver- sion is tliat which takes place in the mouth. MOUTH DIGESTION. When food enters the mouth it consists of a mixture of vari- ous food-stuffs. In order that the changes M'hich these food-stuffs undergo may be traced thoroughly, let it be supposed that repre- sentatives of all classes of food-stuffs are present, namely, (1) inorganic, salts and water; (2) carhohi/dratcs, starch and sugar; (3)/«fe, or oils ; and (4) proteids. MO I -Til DICESTIOS. 165 All the food of a Hiiid natmv, ik^ matter what classes of food- stiiti's it et)iii|)rist's, ])asscs iiiimcdiatcly \'vo\\\ the mouth into the j)har\ii.\, and tlienre tlirough the esophajiiis into the stomach. Fig. 93.— Schema showing the temporary and permanent teeth in a child five years old irijevera(res of various kinds are unchanged. If, however, fluids are taken into the mouth when it contains solid food, the latter will l)e softened hy them, and the I'.i -tjsipi.ls Canino Tnci«ors Molars tkujpil-s (juiiie luciior^ Fig. 94.— Schema of the two dental arches; view of their external faces, showing their natural relations. two will be mixed, and will come under the influence of the agents concerned in carrying on mouth digestion. These agents are the teeth and the salivary glands. 166 MOUTH DIGESTION. Mastication. — The chewing of the food or mastieation is perforined by the teeth. Tlie first set of teeth, which are known as temporary, decidu- ous, or milk-teeth (Fig. 9o), and M'hich exist dnring early child- hood are twenty in number, and the seccMid or periaanent set (Fig. 95), which begin to take the place of the first set at about the sixth year of life, remain to a greater or lesser extent until old age. The latter set is composed of thirty-two teeth — four incisors, two canines, four bicus- pids, and six laolars — in each jaw (Fig. 95). The incisors, or cut- ting teeth, are adapted to bite the food ; the molar teeth, or grinders, are adapted to grind the food, while the canines and bicuspids in "man aid the incisors and molars. In the carnivora, the canines — or tushes as they are called — are very long and pointed, and are admirably ada}>ted to pierce the body of their prey, even to the vitals, thus killing and subse- quently tearing the animal pre- paratory to feeding upon it. The herbivora need no such aggres- sive weapons, and in them the molars are so constructed as to grind the food, their teeth resem- bling the grindstones of the mil- ler. The teeth of man have char- acters which resemble those of both carnivora and herbivora, and from this fact it may be inferred that it was designed that man should have a mixed diet. Movements of Mastication. — The movements concerned in mastication are those of the loM'er jaw upon the upper, produced by the action of the following muscles : Ilasseter, temporal, internal and external pteri/r/oids, digastric, mj/lohiioid, and genio- hyoid. The lower jaw is brought against the upper by the con- traction of the masseters, temporals, and internal jitervgoid mus- cles. The action of the external ]iterygoids, when both are acting, is to draw the lower jaw forward, causing it to project beyond the upper. If but one external pterygoid acts, that side of the jaw is drawn forw^ard and the chin deviates to the oppo- site side. Fig. 9o. — The palate and superior dental arch (right side) : 1, median incisors ; 2, lateral incisors ; 3, canine ; 4, first bicuspid ; 5. second bicuspid ; 6, first molar; 7, second molar; 8, wisdom-tooth ; 9, mucous membrane of the hard palate continuous behind with that of the soft palate ; 10, the anteroposterior raphe of palate ; 11, pits on each side of the raphe per- forated witli the orifices of glands; 12, anterior rugosities of the mucous membrane (after Testut). lysAIJVATION. 167 The digastric, mylohyoid, and geniohyoid mnscles depress the lower jaw, and this is an essential i)art of mastication, for the jaws must be separated as well as hrouglit togetiier to nialS?f//.s'ow'.s (1i(ct, which is about 6 cm, long and the size of a crowquill, and is discharged into the mouth on the inner surface of the cheek, opposite the second molar tooth of the upper jaw. Fig. 96. — View of the salivary glands (right side) (the inferior maxilla has been removed from the symphysis to the ascending ramus) : A. parotid gland, with A' its anterior prolongation ; B. submaxillary gland ; C, sublingual gland ; D. gland of Niihn or of Blandin ; E, gland of Weber, a, duct of Steno ; b, duct of Wharton with h' its orifice on the floor of the mouth ; c, excretory ducts of the sub- lingual gland. 1, sternocleidomastoid; 2, posterior belly of the digastric; 3, 3', mylohyoid, right and left; 4, hyoglossus ; 5, genioglossus ; 6, pharyngoglossus ; 7, geniohyoid muscle; 8, masseter ; 9, buccinator; 10, middle constrictor of the pharynx; 11, primitive carotid; 12, internal jugular vein; 13, external carotid artery; 14, lingual arterj'; 15, facial artery; 16, facial vein; 17, superficial tem- poral artery ; 18, transverse facial artery ; 19, facial nerve ; 20, auriculotemporal nerve; 21, lingual nerve, displaced slightly upward on account of the position of the tongue. The nerves which supply this gland are branches of the carotid plexus of the sympathetic, the flicial, the auriculotemporal, and the great auricular nerve. The suhmaxiUary gland is situated beneath the lower jaw. Its secretion is discharged bv Wliarion\s duct, which is about 5 cm. ISSALIVATION. 169 lon^- aiul opens at the .side of tlie fVeiuini of the tongue. Its nerves eoiiie iVoni the suhmaxiUarv i;aniilion, and eonsist of fiUi- ments of the chorda tyni])aui of the facial and lin<:;iiai hranch of the inferior niaxilkiry, of the mylohyoid branch of the inferior dental, and of the sympathetic. The .sublingual ohmd lies under the mucous membrane, at the side of the frenum of the tonjjjue. Its secretion is discharged through from eight to twenty ducts, ducts of liichiua, which open on the j)rominence of the mucous membrane made by the gland beneath. Sometimes two or more of these ducts join, and form the duct of Bartholin, which opens into Wharton's duct. The nerves of this gland are branches of the lingual. Besides these three sets of glands there are numerous mucous glands on the dorsum and the edges of the tongue, in the tonsil, and the soft palate, whose secretion is a constituent of the saliva. The salivary glands belong to the class ordinarily described as compound racemose glands. Inasmuch, however, as the secreting portions are not sacs, which are characteristic of racemose glands, but tubes, this variety of gland is perhaps better denominated conipoinid tubular. It consists of lobes, which in turn are made up of lobules, each of which is composed of tubular alveoli or acini connected with a duct. The ducts from diiferent lobules join together to form larger ducts, and finally all combine to form the main duct of the gland. Mucous (Fig. 97) and Albuminous Glands. — Two types of glands are recognized by histologists accord- ing to the product and the appearance of the cells within the alveoli of the salivary glands : mucous and albuminous or serous. The mucous gland secretes a tenacious fluid containing mucin, and the cells are relatively large and clear, and have been described as resembling ground glass ; their granules are ordinarily indistinct. The suldingiial and the raucous glands of the mouth are repre- sentatives of this type. These glands also contain demilunes of Heidenhain or crescentic cells, which are placed between the mucous cells and the base- ment-membrane (Fig. 97). Heidenhain, whose name they bear, Fig. 97.— Mucous gland : submaxillary of dog ; resting stage. 170 MOUTH DIGESTION. considers tliem to be uinleveloped mucous cells, destined to replace the secretin^: cells when they shall have ceased to perform their function and have disap|x;ared ; while other opinions are that they are a distinct type of albuminous cell, or are due to a post-mortem chancre. Some observers claim to have demonstrated that the lumen of the albuminous glands is continued as fine capillar}' spaces between the cells of these glands, and that from these pass oif smaller branches Avhich penetrate the cells themselves, and that in the mucous glands these same capillaries exist only in con- nection with the demilunes. If this is confirmed, it would seem to be more than probal)le that the demilunes liave distinct secre- tory functions. The all)uminous gland secretes a watery or serous fluid, which Fig. 98.— Parotid of the rabbit, in tbe resting condition fafter Heidenhain). contains, besides water, inorganic salts, some albumin, and may also contain enzymes. The cells of this variety are small and compactly fill the alveoli, leaving but little lumen (Fig. 98). Thev contain albuminous granules which are very distinct. The parotid gland represents tiie serous or albuminous type. The human submaxillary gland is a mixed type containing both mucous and albuminous'alveoli, the latter, however, in greater number. It is a fact that in mucous glands some cells are found which are regarded as characteristic of the albuminous type, and vice ISSALIVATION. 171 versa; so that it iias been .siii2:' the inijuilses to a center in the iiu(hilla, i'roin whieh etVerrnt impulses pass out throuuli tlic secretory nerves to the glands. This center may be stinudated hy atlerent ini])ulses reaching it through other nerves ; thus salivary secretion may be increased, or " the mouth made to water," by the smell or even the thought oi' food. This center may also be inhibited from sending out secretory impulses, as through fright or other nervous disturbance, thus diminishing the secretion of saliva and causing the dry mouth and "throat which so commonly accompany such conditions. Changes in the Salivary Cells. — Certain changes take place in the salivary cells as a result of their activity. When a ralibit is fasting, the cells of the parotid gland are granular throughout, their outlines being faintly marked by light lines. If it is fed, or pilocarpin injected, or the sympathetic stimulated, the "granules disappear from the outer portion of the cells, so that there is an external clear border surrounding the granular in- terior. If the stimulation continues, the granules diminish and are collected near the hunen of the alveoli and at the margin of the cells, the clear border becomes enlarged, and the cells become smaller. The explanation of this is that the granules contain a substance which is or which becomes the ptyalin of the saliva. If it should be demonstrated hereafter that there is a zymogen which precedes the ptyalin, it would receive the name of pti/alinogoi, but this has not as yet been proved to occur. These granules in the cells are called zymogen granules. While these granules are being used up to form the j)tyalin new material is being deposited by the blood at the base of the cells, which in turn will later form the zymogen or ptyalin. Similar changes take place in the mucous glands, in the cells of which are granules (125 to 250 to a cell) composed of mncin- ogen, which becomes mucin, and is in this form discharged into the lumen of the alveoli. The demilunes, before referred to, are situated outside these cells which produce the mucinogen. Properties and Composition of the Saliva. — The secretion of the human parotid gland is a clear fluid, though sometimes turbid, and contains some epithelial cells. It is alkaline in reaction, but less so than the saliva of the submaxillary gland. Its specific gravity is verv variable, as is shown by the following figures : Mitscherlich gives it as 1.006 to 1.008 ; Oehl, 1.010 to 1.012 with scanty, and 1.0035 to 1.0039 with plentiful secretion ; Hoppe- Seyler, 1.0061 to 1.0088 ; the solids being from 5 to 16 parts per 1000. It contains ptyalin and potassium sulphocyanate, but no mucin. The secretion of the human submaxillary gland is clear and watery, always alkaline, and has a specific gravity between 1.0026 176 MOUTH DIGESTION. and 1.0033. The solids are from 3.6 to 4.6 parts per 1000. It contains ptyalin, but authorities differ as to its containing potas- sium sulphocyanate. The existence of such ducts as those of Stenson and Wharton makes it easy to obtain the pure secretions of the parotid and submaxillary glands by the introduction into them of cannulae ; but this is not true of the iiublingual glan: salts and in uniylolytic power tiian the secrctiDii eoniinu; withont stiinuhition. Mixed saliva resulting from stimulation with ether, aleohol, ete., c(»ntains a niiieh larger propoi'tion ot" nuiein than the seeretiun eoniing without stimula- tion, being notieeal)ly thiek and viscid. This (juality is not appar- ent in the saliva resulting from mechanical stimulation. Duration of flic Aini/loli/fic Action of Sadoa. — One of the in- teresting (piestions in regard to the amylolytic action of saliva is as to its duration. As we have already seen, a very minute per- centage of free acid arrests this action. The food remains in the mouth but a short time, when, in portions, each of which is an alimentary bolus, it passes through the esophagus into the stomach, a process which is also very brief, and in the latter organ it meets with a fluid, the gastric juice. Although the amount of hydrochloric acid in this fluid is enough to arrest the action of the enzyme if it was free, still it must not be forgotten that this is not the case. It is in combination with the proteids of the gastric juice, and later with the proteids and peptones the results of stomach digestion, so that consider- able time must elapse before there is enough of the free acid present to arrest the action of the ptvalin. Just how long this is, it is impossible to say in all cases, for it will vary under different conditions. Experiments have shown that where the meal con- sists wholly of carbohydrates no free acid is found until about three-quarters of an hour after the meal has been eaten. In discussing this subject Moore says : " The diastatic action of the saliva, therefore, continues in the stomach during and after a meal until (1) the alkali of the saliva has been neutralized, (2) the proteid present in solution has been satisfied, and (3) a trace of free hydrochloric acid remains in excess." Some excellent authorities are inclined to regard the chemical action of the saliva as subordinate to the mechanical, inasmuch as in their opinion the amount of starch converted into maltose by the ptyalin is inconsiderable. This they infer from the fact that a medium as acid as the gastric juice will inhibit the action of the enzyme, and, since the food remains in the mouth and esophagus but a short time, it follows that the conditions favorable for salivary digestion must be of brief duration. It seems to us that they ignore the facts, already stated, with reference to the necessity of free acid to stop the action of the enzyme, and to the long time before this is present in the stomach in quantity sufficient to pro- duce its effect. It is undoubtedly true that the starch digestion of the small intestine is very important, but certainly in the three- quarters of an hour, apju'oximately, that the saliva acts a consider- able amount of starch can be converted, so that to the chemical action of the saliva must be assigned a greater importance than it has hitherto held. ISO MOUTH DIGESTION. The experiments of Cannon on the movements of the stomach, to which we shall refer in detail in considering the function of that organ, demonstrate most conclusively that in the process the conditions are most favorable for a relatively prolonged action of ptyalin on starch ; the principal condition being the absence of movement in this part of the stomach, so that the food remains here in an alkaline condition for a considerable length of time. This action of the saliva for so long a time after the entrance of the food into the stomach emphasizes the impor- tance of thorough mastication and insalivation, 3Iechanical OJfice of Saliva. — While the teeth are thoroughly comminuting the food they are at the same time working sidiva into the interstices which they make between the particles of the food. This process not only facilitates the chemical action of the ptyalin, but it tends also to keep the particles separated, so that when the food reaches the stomach the gastric juice may the more readily permeate it and produce its characteristic action. Saliva aids also in softening the food, thns enabling the process of deglu- tition or swallowing more easily to be performed. The secretion of the mucous glands of the mouth is of special importance in this act, the mucus secreted being of a ropj/ consistency and possessing great lubricating properties. Saliva is intimately con- nected with the sense of taste. Only soluble substances are sapid — that is, excite, the sense of taste. Insoluble substances have no taste. It is for this reason, among others, that calomel is such an excellent cathartic for children ; being insolul)le, it is tasteless, and they readily swallow it. Soluble substances not already in a state of solution are dissolved l)y the saliva, and in this condition excite the sense of taste. When in a febrile or other state, in which the secretion of the saliva is greatly dimin- ished, deglutition is difficult and the sense of taste is markedly deteriorated. Deglutition. — This is the act of swallowing, and for purposes of description is conveniently divided into three stages: 1. From the mouth to the pharynx ; 2. Through the pharynx to the esoph- agus ; and 3. Through the esophagus to the stomach. First Stage. — The tongue is an organ composed of muscles, some of which have their origin outside the tongue but end in it, known as the extrinsic muscles, and others Avhich are situated wliolly within the organ, and constitute its greater part ; these are the intrinsic muscles. In the former group are the styloglossus, hvoglossus, palatoglossus, and others ; and in the latter the superior lingualis and inferior lingualis, together with others which we need not name. For a detailed description of the muscles of the tongue the reader is referred to anatomical text-books. The floor of the mouth is made up of the two mylohyoid muscles, which have their origin in the mylohyoid ridge and are inserted DEGLUTITION. 181 into tlic liyoid hone. The diiiustric, stylohyoid, and genioh\(»id nuisc'los neod also to be mentioned in this conneetion. After the solid food has been thoroughly masticated and insali- vated, it is collected by the tongue, aided, by the cheeks, and formed into a small mass, the aluacnfcd-i/ bolus. This is placed npon the dorsum of the tt)ngue, which is then ])ressed against the roof of the mouth by the action of the styloglossi and ])alatoglossi muscles, thus carrying the bolus backward to the base of the tongue. There is also contraction of the anterior belly of the digastric, mylohyoid, and geniohyoid muscles, elevating and moving forward the hyoid bone and the tongue, and the ])harvnx and larynx are thus carried upward and under the bolus. The bolus is now at the anterior ])illars of the fauces, the palato- glossi muscles covered with mucous membrane. The first stage may now be considered to end and the second begin. Up to this point the movement has been a voluntary one, absolutely under the control of the will, for it would be possible at this point in the process to eje<"t the l)olus from the mouth. It is probable, however, that under ordinary circumstances the latter part of the first stage is involuntary — /. e., reflex — as, indeed, are both the second and the third stages throughout. The nerves which are involved in the first stage are the fifth nerve, su{>plying the mucous membrane of the mouth and the an- terior portion of the tongue ; and the glossopharyngeal, which is dis- tributed to the posterior third of that organ. These are the sensory nerves, or those which carry the afferent impulses ; the motor nerves are the hypoglossal, supplying the muscles of the tongue, the mylohyoid branch of the inferior dental, the largest branch of the inferior maxillary branch of the fifth, Mhich supplies the anterior belly of the digastric and the mylohyoid. Second Stage. — In this stage the bolus is carried through the pharynx, and, simple though this may appear, it must be borne in mind that there are other openings than the esophagus Avhich comnumicate with the pharynx into which the bolus might be car- ried ; these are the posterior nares and the larynx. If carried into the former, no danger would accrue ; but if into the latter, and it was not at once expelled by the violent act of coughing which it would excite, a fatal result would doubtless ensue — either immediately if the bolus so blocked the larynx that no air could enter, or after a longer period if it passed through and brought about the fatal result by setting up inflammation of the air-passages or lungs. The approximation of the base of the tongue to the soft palate and the contraction of the anterior pillars of the fauces, the jjalato- glossi, the so-called constrictors of the isthmus of the fauces, shut off the pharynx from the mouth and carry the bolus backward far enough to bring it within the influence of the constrictors of the pharynx. An additional oI)stacle to the return of the bolus to 182 MOUTH DIGESTION. the mouth is the elevation and carrying; backward of the hyoid bone by the contraction of the posterior belly of the digastric and the stylohyoid muscles. Its entrance into the posterior nares is prevented by the elevation of the soft palate caused by the action of the levator palati, which is innervated by the facial, according to Kirkes, or the internal branch of the spinal accessory, according to Gray, The soft palate is at the same time made tense by the tensor palati, supplied by a branch from the otic or Arnold's ganglion ; by the' contraction of the palatopharyngei muscles, which form the posterior pillars of the fauces, and are supplied by the in- ternal branch of the spinal accessory ; and by the raising of the uvula, due to contraction of the azygos uvulae. The contracted palatopharyngei do not come closely together, but what is lacking in their approximation is made up by the uvida. This contraction of the palatopharyngei also raises the pharynx and thus brings the bolus well within it. It will be readily seen that the changes just described not only result in shutting off any possible entrance to the posterior nares, but also form of the soft palate and the posterior pillars of the fauces, with the uvula between them, a continuous surface well lubricated with mucus, and so inclined as to direct the bolus in the direction which it should take to reach the esophagus. The upper portion of the pharynx is in reality a part of the respiratory rather than the alimentary apparatus, as is shown by the fact that its mucous membrane is covered with ciliated epithe- lium, as is also the upper surface of the soft palate. The bolus has still, however, to pass the opening into the larynx without gaining entrance thereto. This is accomplished in the following manner: As we have seen, the larvnx is raised in the manner described, aided by the thyrohyoid muscle, which acts to raise the larynx when the hyoid bone ascends, and its opening closed by the contraction of the arytenoideus and the lateral crico-arytenoidei, supplied by the inferior or recurrent laryngeal nerve, a branch of the pneumogastric. Whether the epiglottis is folded back or remains in its usual erect position during deglutition is a matter of dispute. Those who claim that it closes the glottis give various arguments to sustain the opinion and explain how it takes place. The action of the thyrohyoid, just referred to, is regarded by one authority as causing or permitting " the folding back of the epiglottis over the upper orifice of the larynx." It is further claitned that this movement can be felt by simply passing the finger into the throat until it comes in contact Avith the epiglottis and then performing the act of swallowing. On the other hand, there is a case on record in which enough of the pharynx was removed in a surgical operation to permit the actual inspection of the epiglottis during the act of swallowing, and it was observed to undergo no DEGLUriTION. 183 change of position. Wiiatcvor may be the fact in this regard, there is no (jiit-stion tliat tlie hirvnx is perfectly j)rotectetl against the entrance of food, even tiioiigh the ejiiglottis does not fold back during the act of deglutition. At the close of the first stage tlie pharynx is raised so as to receive the bolus, and at the same time it is eidarged. This is due to the forward movement of the larynx and the tongue, both of which as they are elevated are also carried forward ; and also to the contraction of the stylopharyngei, whose action is to draw upward and outward the sides of the pharynx, thus separating them and enlarging the cavity laterally. The bolus being well within the })luirynx, the muscles which raised the latter relax, and it descends, carrying with it the bolus, which is now passed along by the constrictors of the pharynx to the opening of the eso])h- agus. The stylopharyngcus receives its nerve-supply from the glossopharyngeal, while the constrictors are supplied by the pharyngeal plexus, the inferior constrictor being supplied by the external laryngeal branch of the superior laryngeal and the recur- rent laryngeal. Third Stage. — In this stage the bolus passes through the esoph- agus into the stomach. This canal is about 23 cm. in length, and from 1.8 to 2.4 cm. in breadth. When empty its walls are in apposition, and in section it presents the appearance of a trans- verse slit. It has three coats : 1. An internal, composed of mucous membrane, covered with stratified epithelium, as is that of the mouth and that of the pharynx from the soft palate down. 2. A submucous coat, in which are the esophageal glands, compound racemose glands which open by ducts upon the surface of the membrane, and which secrete mucus. These glands are most abundant near the cardiac orifice, where they encircle the esoph- agus. 3. A muscular coat, which is arranged in two layers, an inner (circular) and an outer (longitudinal). The fibers of the circular layer form at the cardiac orifice, where the esophagus enters the stomach, a sphincter which keeps the opening closed, especially when the stomach contains food. The muscular tissue of the upper third is principally striated, while the remainder is of the involuntary variety. The nerves of the esophagus come from the pneumogastric and the sympathetic. The circular layer of the muscular coat is continuous with the inferior constrictor, and the contraction of the fibers of this layer follows immediately upon that of the constrictor, carrying the bolus onward in its passage to the stomach. This is a continuation of the reflex act which begins certainly in the pharynx, possi- bly in the mouth. The bolus stimulates the mucous membrane as it passes along, and a Avave of peristalsis follows. Thus each successive portion of the muscular coat contracts behind the bolus, gradually pushing it onward. When it reaches the cardiac orifice, 184 MOUTH DIGESTIOy. the sphincter relaxes and the bolus is forced into the stomach. This can sometimes be heard by applying a stethoscope over the epigastric region. The time occupied by the passage of the bolus from the beffinnino; of swallowing' to the moment it enters the stomach is about six seconds. The action of the longitudinal fibers is not understood, although some authorities think that their con- traction precedes that of the circular fibers, and thus tends to dilate the esophagus and bring it forward over the bolus. The process of deglutition has been very thoroughly studied by Falk and Kronecker, by Kronecker and ^Sleltzer, and still more recently by Cannon and ]\Ioser. The first-named experi- menters have shown that tliere is pressure enough produced by the raj)id contraction of the muscles of the mouth to force liquid food through the esophagus independently of peristalsis, and indeed before the peristaltic wave passes along. Thus, when cold water is swallowed its presence is recognized in the epigastrium almost immediately ; and it has been also noted by them that when strong acids pass through the esophagus only parts of it are corroded, and not the entire surface of the mucous niemljrane, as would be the case were they swallowed by ])eristaltic action. The second named experimenters conclude from their experi- ments that liquids and semisolids are forced down the esophagus, or "squirted" down, by the rapid contraction of the mylohyoid muscles, nearly as far as the cardia (cardiac orifice), and that they remain here tmtil the peristaltic wave reaches this point, when they are carried into the stomach, which is about six or seven seconds from the beginning of swallowing. In these experiments only liquids and semisolids Avere employed, and it is manifest that what might be true of these might not be true of solids. It M'as to determine the actual movements of solids, as well as of semisolids and liquids, that the experiments of Cannon and Moser were performed. Some of these were on geese, cats, dogs, and horses, and some on man. The following is the " summary " of these later experiments, as published in the American Journul of Phi/.'^iolof/i/ : " There is a difference in swallowing according to the animal and the food which is used. " In fi)wls the rate is slow and the movement always peri- staltic, without regard to consistency. A squirt-movement with liquids is manifestly impossible, as the parts forming the mouth are too hard and rigid. AVith this diminution of propulsive poM'er in the mouth there is observed a greater reliance on the force of gravity. The head is raised each time after the mouth is filled, and the fluid by its own weight trickles into the esoph- agus, through which it is carried by peristalsis. " In the cat the movement is always peristaltic and slightly faster than in fowls. A bolus takes from nine to twelve seconds STOMA ri I DIGESTION. 185 in reaching the stomach. Liquids move somewliat more rapidly than semisolids in the ii})per esophagus. In the lower or diaphrag- matic part the rate is very much slower than above, and is tlie same for liquids as for solids. '' In the dog the total time for the descent of the hrdus is from four to Hve seconds. The food is always })ropelled rapidly in the upper esophagus and moves more slowly t)elow. This rapid movement is frequently continued further with liquid food. Xo distinct pause was observed when the movement of the bolus changed from the rapid to the slower rate, " In man and the horse liquids are propelled deep into the esophagus at a rate of several feet a second l)y the rapid con- traction of the mylohyoid muscles. Solids and semisolids are slowly carried through the entire esophagus In- peristalsis alone." The peristalsis of the esophagus is brought about by atFerent impulses which reach the center of deglutition and from which efferent impulses pass out to the muscular coat. While the act is, therefore, principally under the control of the nervous system, the stimulation of tlie successive portions of the mucous membrane as the food passes along may have some part in its production. STOMACH DIGESTION. The food having reached the stomach, now undergoes stomach or gastric digestion. The stomach is a hollow organ into Avhich the esophagus opens, ';^^^«/ l^y^^ yfnterwrjurface yoaiertCL Fig. 104. — Anterior outliues of stomach. His' model. the opening being called the cardia or cardiac orifice, and which at its lower end communicates with the small intestine through the pyloric orifice. Its greatest diameter is from 24 to 26 cm., and that from the lesser to the greater curvature, 10 to 12 cm. 186 STOMACH DIGESTION. It can hold from 2.5 to 4 liters. When empty its walls are in apposition. Its form and position are shown in Figs. 104 and 105. The study of the movements of the stomach by Cannon by means l/njieuurt vulorimm. Fig. 105. — Posterior outlines of stomach. His' model. of the Rontgen ray, using subnitrate of bismuth to throw a dark shadow on the fluorescent screen (p. 195), has brought out some facts in regard to the anatomy of the stomach which make it desir- able to reproduce here the outline of that organ as demonstrated by the experiments referred to. Fig. 106 represents the stom- ach of the cat, but probably also represents in all im- portant ]>articulars the hu- man stomach as well. Coats of the Stomach. — The stomach is composed of four coats: Serous, muscu- lar, submucous, and mucous. The serous coat is a reflec- tion of the peritoneum. The submucous coat, which con- tains ihe nerves and blood- vessels, is of special interest as giving to the mucous coat great mobility and as per- mitting it to form folds, called nigcr, when the cavity is empty. This structure is in striking contrast with the anatomic structure of the uterus, in which organ, the submucous coat being absent and the mucous lying directly upon the muscular coat, there is a total want of mobility of the membrane. Aside from this fact, neither the serous nor the submucous coat has any special physiologic Fig. 106.— The cardiac portion is all that part to the left, as the stomach lies in the body, of WX. The cardia is at C. The pylorus is at P, and the pyloric portion is the part between P and Tl'.V. This has two divisions: the antrum, between P and YZ. and the pre-antral part, between WX and YZ. The lesser curvature is on the top of the outline between C and P, and the greater curvature between the same points along the lower border {Amer. Joiini. of Physiology). COAK OF TIIK STOMACH. 187 interest. Tlic muscular coat is composed of three layers : lon- p^itiidiiial, circular, and ol)li(|iie. Tlie /onf/itHflinal layer is made up of tii)ers continuous with similar fibers of the esophaji'us, and is most external — that is, immediately beneath the peritoneum. These fibers radiate from the esophageal or cardiac orifice, and are especially al)undant in the region of the greater and lesser curvatures. They extend to the intestine, where they ibrm a laver of the muscular coat of tiiat organ. The circnhir layer is situated internal to the longitudinal, and, as the name implies, its fibers encircle the stomach — that is, are in general at right angles to the longitudinal axis of the stomach. At the pyloric orifice of the stomach, where the duodenum begins, these circular fibers are aggregated in such number as to receive the name of pyloric muscle or sphinder pj/loricus. Their projection into the interior of the organ at this location with its covering of mucous mem- brane constitutes the pyloric valve. The oblique layer is found especially at the cardiac extremity of the stomach. The mucous coat, or mucous membrane, is soft and velvety. Near the cardiac orifice the membrane is about \\ mm. in thick- ness, and near the pylorus 2 mm., while in general between these two points its thickness is al)0ut 1 mm. Its surface is composed of columnar epithelium, which secretes the mucus found in the stomach in the intervals of digestion, this mucus being a con- stituent of the gastric juice. In the mucous membrane, and forming a part of it, are two sets of glands, the pi/Ioric glands, so called from their abundance in the pvloric portion of the stomach, and the cardiac glands (Fig. 107), which are so called because of their occurrence in the cardiac region. The pyloric glands were formerly called mucous glands, but their product is not mucus ; the cells are of the serous type described in connection with the salivary glands. The ducts of both cardiac and pyloric glands are lined l)y columnar epithe- lium continuous with that covering the mucous membrane. In the tubes of the pyloric glands are granular cells called chief or central cells. The same kind of cells are found in the tubes of the cardiac glands ; and beneath these cells — that is, between them and the basement-membrane — are, besides, large cells, which are ovoid in shape, the parietal or oxyntic cells. These cells cause the base- ment-membrane against which they He to bulge out. The chief cells are regarded as producing the pepsinogen which is converted into the pepsin of the gastric juice, and the parietal cells as pro- ducing the hydrochloric acid, although the latter has not been certainly demonstrated. The vascularity of the stomach is very great. In the intervals of digestion the mucous membrane is of a pale pinkish color, while during active digestion its color is a bright red. This change in color is due to the greatly increased amount of blood present in the blood-vessels of the organ at this time. 188 STOMACH DIGESTION. The pyloric portion is specially distinguished by the name antrum pylori, and is that part situated between the pyloric orifice SJ^mm Fig. 107. — Cardiac glands. Diagram showing the relation of the ultimate twigs of the blood-vessels ( T' and A), and of the absorl)ent radicals (L) to the glands of the stomach, and the ditt'tjrent kinds of epithelium — namely, above, cylindrical cells ; small pale cells iu the lumen ; outside which are the dark ovoid cells. and a band of circular fibers, the transverse band or sphincter antri pylorici, distant from the orifice about 10 cm. In modern physiology this portion of the stomach is invested with much interest, and is referred to on p. 195. Prior to 1822 the process of stomach digestion Avas little un- derstood. During that year Alexis St. Martin, a Canadian boatman, eighteen years of age, was so injured by the accidental discharge of a gun that when the wound healed there remained in Fig. 108.— Left breast and side his side a permanent opening (erect position), showing perforation nearly 2^ cm. in diameter, wdiich of the walls of the stomach of Alexis • :■ , ■, ., , ,, ., St Martin communicated with the cavitv of the stomach (Fig. 108). Dr. Beaumont, the surgeon in charge of the case, and subsequently others, carried on a series of experiments and observations extend- COMPOSITIOX OF HUMAN GASTRIC jriCE. 189 ing- through years, aiul the ])rc.sent knowledge of stomach digestion is hirgely based upon this remarkable case. After the healing of his woinid his health was excellent, and he lived to be eighty-four years of age. During the intervals of digestion the mucous membrane of tlie stomach is pale in color, and is covered with a transparent and viscid mucus which is neutral or alkaline in reaction. This mucus is the j)roduct of the epithelium of the mucous membrane. After food has entered the stomach drops of gastric juice appear at the mouths of the glands. Quantity of Gastric Juice. — The amount of gastric juice daily secreted is difficult of determination, and it is not surprising that authorities should differ so much on this point. Dr. Beau- mont estimated it to be 180 grams in the case of St. Martin, while others place it as high as 7 liters, or one-tenth of the weight of the body. The gastric juice is never in large quantity in the stomach at any one time. It is secreted gradually by the glands, is poured out into the cavity of the stomach, where it permeates the food, is passed on into the small intestine, where it is absorbed by the blood-vessels, and is then returned to the circulation, from which its constituents were derived. It has the following proper- ties : it is clear, nearly colorless, and strongly acid. Its specific gravity is about 1002. Composition of Human Gastric Juice Mixed with Saliva. — As can readily be understood, it is impossible to obtain gastric juice unmixed with particles of food or saliva or other foreign substances, hence an accurate analysis cannot be given. The analysis by Schmidt of gastric juice from a Avoman having a gastric fistula, which is the only complete analysis on record, is as follows : Water 99.4400 Ora;anic substances (pepsin, peptones, and rennin) . . . .3195 Free hydrocliloiic acid 0200 Calcium chlorid 0061 Sodium " 1464 Potassium " 0550 Calcium 1 Magnesium Ipiiosphates 0125 Ferrum j Loss 0005 100.0000 The constituents of the gastric juice of special physiologic interest are hydrochloric acid, pepsin, and rennin. It was at one time a matter of di.spute whether the acidity of this fluid was due to hydrochloric or to lactic acid, but there is now a unanimity of opinion that it is the former. If lactic acid is present, it is probably due to lactic fermentation which has taken place in the liW STOMACH DIGESTION. carbohydrates of tho food when these are in excess. This fermen- tation may go on to the formation of acetic and butyric acids, these changes being doubtless due to the presence of micro- organisms. Hydrochloric Acid. — Tlie amount of free hydrochloric acid in human gastric juice varies from 0.05 to 0.3 per cent. Several of the best authorities give the average as between 0.2 and 0.3 per cent. Although the only possible source of hydrochloric acid is the chlorids of the blood, which decomposing yield chlorin, and this uniting with hydrogen forms the acid, yet the manner of its for- mation is still undecided, and various theories have been pro- pounded to explain it. Among these, Maly's is, perhaps, the one most generally accepted. This theory is that there occurs a reaction between the phosphates and chlorids of the l)lood which results in the formation of hydrochloric acid. This reaction is expressed by the following equation : NaH.PO, + NaCl = Na^HPO, + HCl Sodium dihydrogen Sodium Disodium hydrogen Hydrochloric phosphate. chlorid. phosphate. acid. Or the hydrochloric acid may l^e produced by the reaction be- tween calcium chlorid and disodium hydrogen phosphate, as follows : SCaCl, + 2Na.HPO, = Ca3 (PO,)^ + 4NaCl + 2HC1 Calcium Disodium hydrogen Calcium Sodium Hydrochloric chlorid. phosphate. phosphate. chiorid. * acid. This theory regards. the formation of the hydrochloric acid as taking place in the blood ; and being highly ditfusible, it diffuses through the gastric glands into the stomach. In this explanation the cells have no part in the formation of the acid. Gamgee re- gards the cells of the glands, those known as parietal or oxyntic, as the acid producers, and supposes that they have a peculiar power of selecting the alkaline phosphates and the chlorids from the other constituents of the blood, and that the reaction already referred to takes place in them, hydrochloric acid resulting. But, as we have already said, this is pure theory, and has never been demonstrated. About all that can be said is that the hydrochloric acid is probably produced by the parietal cells from the chlorids of the blood, and that is their special function, as is that of the chief cells to produce pepsinogen or the cells of the salivary glands to produce ptyalin. Besides the action of hydrochloric acid in connection with digestion, it has still another which is under some circumstances one of great importance — that is, its action on pathogenic bacteria ; we shall discuss the subject of Bacterial Digestion later (p. 244), COMPOSITION OF III 'MAX GASTRIC JUICE. 11)1 but here we desire to eall attention to the protective influence which the hydrochloric acid of the gastric juice exerts against certain well-lvnown diseases. Tlie preservative power of gastric juice on meat, due to the action of the hydroehloi'ic acid on putrefactive haetoria, has long been known. The cholera spirillum, the germ which produces Asiatic cholera, will not survive in fluid of the acidity of the gastric juice of the guinea-pig and the rabbit. Xor has cholera been produced when, .after first neutralizing the gastric juice by administering soda, cholera cultures have been ingested. But if opium is given with the soda, and intestinal peristalsis slowed down thereby, choleraic symptoms result, Koch produced genuine cholera in animals by opening the abdomen, tying the bile-duct, and then injecting cholera cultures directly into the intestines. It w'ould appear from the evidence taken as a whole that, if the stomach is in a normal condition, cholera germs will be destroyed by the gastric juice. It is not improbable that if the stomach is the seat of catarrhal inflammation, as might be caused by alcohol taken for a long time in excess, the conditions in the stomach-cavity would be favorable to the reception and growth of the cholera spirilla, and the disease be produced. Falk claims that the bacillus of anthrax is destroyed by gastric juice, except when in the sporulating stage, but that this fluid has no effect on the tubercle bacillus. Writing on this general subject, Sternberg, in his Manual of Bacteriology, says : " The experiments of Straus and Wiirtz and of others show that normal gastric juice possesses decided germi- cidal power, which is due to the hydrochloric acid contained in it. Hamburger (1890) found that gastric juice containing free acid is almost always free from living micro-organisms, and that it quickly kills the cholera spirillum and the typhoid bacillus, but has no effect upon anthrax spores. Straus and Wurtz found that the cholera spirillum is killed by two hours' exposure in gastric juice obtained from dogs, the typhoid bacillus in two or three hours, the anthrax bacillus in fifteen to twenty minutes, and the tubercle bacillus in from eighteen to thirty-six hours. The ex- periments of Kurlow and AVagner, made with gastric juice ob- tained from healthy men by means of a stomach-sound, gave the following results: Anthrax bacilli without spores failed to grow after exposure to the action of human gastric juice for half an hour, l)ut s]>ores were not destroyed in twenty-four hours ; the typhoid bacillus was killed in one hour ; the cholera spirillum, the bacillus of glanders, and Bacillus pyocyaneus were all destroyed at the end of half an hour; the pus cocci showed great resisting- power. Certain bacteria have a greater resisting-]>ower for acids than any of those above mentioned, and some of them may con- sequently pass through the healthy stomach to the intestine in a 192 STOMACH DIGESTION. living condition, but there is good reason to believe that the spirillum of ciiolera or the bacillus of anthrax would not. On the other hand, the tubercle bacillus and the spores of other bacilli can, no doubt, pass through the stomach to the intestine without losing their vitality." The hydrochloric acid of the gastric juice when free certainly destroys many non-pathogenic bacteria introduced with the food, which otherwise might cause it to decompose ; thus both lactic and acetic fermentations are prevented ; it is said, however, that hydro- chloric acid when combined with proteids does not have this power. Cohn explains the action of the free acid by supposing that it decomposes the alkaline phosphates, without which the bacteria cannot live. Pepsin — The chief or central cells of the cardiac glands present a granular appearance ; this is due to granules which are the product of the cells, and consist of a zymogen, pepsinogen. During gastric digestion they diminish, so that the outer ])ortions of the cells become quite clear, losing the granular a])pearance, while the inner portions, or those near the lumen of the tube, retain it. While the chief cells of the cardiac glands doubtless produce most of the pepsinogen, still it has been abundantly proved that the same variety of cells of the pyloric glands also produces this zymogen. The ])epsinogen thus formed becomes converted into pepsin, which exists in the human stomach at birth. Pepsin is a proteolytic enzyme which acts only in an acid medium, so that the presence of the acid is as essential to stomach- digestion as is that of the enzyme. AVhile hydrochloric acid gives the best results, some other acids may be substituted ; thus nitric and lactic, and even oxalic and tartaric acids, will exert a pro- teolytic action. In the case of pepsin, as also of ptyalin, and indeed of all enzymes, the effect of temperature upon tiie zymolytic process must always be considered. The optimum temperature for the action of pepsin is from 37° to 40° C. ; while if exposed to 80° C. in a moist state, the enzyme loses its proteolytic power. Low tempcratui-es inhibit its action, but it still acts, though feeblv, at 0° C. It has already been stated that the enzymes have not as yet been obtained in sufficient quantity or sufficiently separated from other substances to analyze, so that the composition of pepsin is still undetermined. Pepsin-hydrochloric Acid. — It is held by some authorities that the pepsin and the hydrochloric acid exist in gastric juice in a state of combination, to which the name of pepsin-hydrochloric acid has been given, but this cannot be said to have been demon- strated. Rennin. — This enzyme exists in human gastric juice at birth, ACTION OF THE GASTRIC JUICE. 193 and it appears to be more al)Uiulaiitly prodiieed in the fundus than in tiie pyloric region, though the exact seat of its formation is not determined. Its action is to eoaguhite the caseinogen ; the changes which tliis undergoes in the process of coaguhition have ahvady been fully discussed (p. 112), and need not be repeated here. Its optimum temperature is between 38° and 40° C, while at 63° C. in an acid medium it is destroyed. The curdling proc- ess precedes the action of the hydrochloric acid and pepsin during the gastric digestion of milk. Mothers are sometimes alarmed when their children, seemingly in perfect health, vomit curdled milk ; but, as has been stated, tliis curdling is a physiologic process, and the only abnormality is its regurgitation, which is usually due to overfeeding. Action of the Gastric Juice. — Having considered the composition of the gastric juice, we are now in a position to dis- cuss its action upon the food. Action on Proteids. — When proteids reach the stomach by the process of deglutition they meet with the gastric juice, whose hydrochloric acid converts them into acid-albumins. Some writers use the term syntonin as synonymous with acid-albumins ; others restrict its use to the special acid-albumin which results from the action of the acid upon myosin. This change in the proteids is more quickly and completely brought about by the acid when pepsin is present than when the acid acts by itself. The dcid- albumin (syntonin) takes up water, and undergoes a "cleavage" or splitting up, as a result of which two soluble proteids are formed, proto-proteose and hefero-proteose, which are together known as primary proteoses. This is due to the action of the pepsin, which is, therefore, a proteolytic enzyme. The process, however, does not cease here ; the action of the pepsin continuing, the primary proteoses take up water and in turn split, forming secondary or deufero-profeoses. These in turn nndergo hydrolytic cleavage, forming as final products, peptones. Inasmuch as there are doubtless two varieties of peptones, as will be seen in the dis- cussion of the digestion of proteids by the pancreatic juice, these are called ampho-peptones. For the distinguishing characteristics of peptones and proteoses the reader is referred to p. 106. Action on Carbohydrates. — Cane-sugar is undoubtedly inverted in the stomach to dextrose and levulose, the hydrochloric acid being the agent in the inversion. All the cane-sugar of the food, however, does not undergo this change in the stomach, some of it not being inverted until it reaches the small intestine. There is some evidence looking toward the presence in the gastric juice of an amylolytic enzyme, but this is as yet too incom- plete to require more than mention. Action on Fats. — Xo chemical change takes place in the fats. The temperature of the stomach, 38° C, renders them 13 * 194 STOMACH DIGESTION. more fluid. If the fat is in tiie form of adipose tissue — that is, enclosed in adipose vesicles — the walls of the latter being proteid in character undergo proteid digestion, setting the fat free ; but the latter is not emulsified, nor is it split up to any extent, though there is evidence to show that some decomposition into fatty acids may occur, probably attributable to the action of bacteria. Action on Albuminoids. — Of all the albuminoids which enter into the food, gelatin is the most important. It is found in various jellies and in soups. When acted upon by hydrochloric acid and pepsin it becomes converted into geUdoses. In the stom- ach these undergo no further change, but in the intestine gelatoses become gelatin i:)eptones under the influence of the trypsin of the pancreatic juice. Movements of the Stomach. — These were observed very carefully by Dr. Beaumont in the case of St. Martin (p. 188), and in order that we may the better refer to the results of recent investigations we will here quote his description. He says : " The bolus, as it enters the cardia, turns to the left, passes the aperture, descends into the splenic extremity, and follows the great curvature toward the pyloric end. It then rMurns in the course of the small curvature, makes its appearance again at the aperture, in its descent into the great curvature, to perform similar revolutions." This occupied in St. Martin's case from one to thr^e minutes. Before describing the results of Cannon's experiments as recorded in the American Journal of Physiologij, and which were performed upon cats, we will first describe the movements as they are believed by most of the modern physiologists to occur in the human stomach. Before food enters the stomach, this organ being empty, its walls are in apposition and its raucous membrane arranged in rugae. The first portions of food that enter separate the walls, but in all portions except where the food is they are still in contact. The presence of food stimulates the muscular coat, and as a result the circular fibers beg:in to contract feeblv and on the side of the <;reat curvature, setting up a wave of peristalsis which travels on toward the pylorus, becoming stronger as it progresses. Just before it reaches the antrum it appears to be stopped by the " pre-antral " constriction, which is the name given by Hofmeister and Schlitz, to whom we owe these observations, to a constriction of circular fibers Avhich surrounds the whole stomach in this region. This has the effect of pushing some of the stomach-contents into the antrum ; the sphincter antri pylorici now contracts, and the antrum is practically shut off from the fundus. The muscular coat of the antrum then contracts, and its contents are forced against the pylorus. The pyloric muscle relaxes to permit liquid material to pass through into the duodenum ; if, however, solid MOVEMESTS OE THE STOMACH. 195 particles come ai::ainst it, tlie relaxation does not occur, i>ut an anti|)eristaltic \vave is set up in the musculature of the antrum which carries the materials l)ack into tiie fundus, the separation of the latter from the antrum having ceased owing to the relaxa- tion of the sphincter antri pyhjrici. The contents are thus re- tained in the stomach to be further acted upon by the gastric juice until they are rendered sufficiently liquid to pass the pylorus. During these muscular movements the food is not only carried toward the pylorus, but it is also thoroughly mixed with the gastric juice, and thus the action of the latter is more complete and efficient than it otherwise would be. Experiments of Cannon. — \\g deem a somewhat detailed account of these experiments warranted, for the reason that, although they were made upon the cat, the evidence is accinnulating that the character of the movements of the human stomach during digestion differs in no essential particular from the movements of the stomach of the animal which was the subject of experimenta- tion. Movements of the Pyloric Part. — AVitliin five minutes after a cat has finished a meal of bread mixed with sul)nitrate of bismuth there is visible near the duodenal end of the antrum a slight annular contraction which moves peristaltically to the pylorus ; this is followed by several waves recurring at regular intervals. Two or three minutes after the first movement is seen, very slight constrictions appear near the middle of the stomach, and, pressing more deeply into the greater curvature, course slowly toward the pyloric end. As new regions enter into constriction the fillers just previously contracted become relaxed, so that there is a true moving wave, with a trough between two crests. AVhen a wave swings round the bend in the pyloric part the indentation made by it deepens, and as digestion goes on the antrum elongates and the constrictions running over it grow stronger, but, until the stomach is nearly empty, do not divide the cavity. After the antrum has lengthened, a wave takes about thirty-six seconds to move from the middle of the stomach to the pylorus. At all periods of digestion the waves recur at intervals of almost exactly ten seconds. It results from this rhythm that when one wave is just beginning several others are already run- ning in order before it. Between the rings of constriction the stomach is bulged out (Figs. 109-111). In one experiment the cat was fed 15 grams of bread at 10.25 a.m. The waves were running regularly at 11 o'clock. The stomach was not free from food until 6.12 p.m. At the rate of 360 waves per hour, approximately 2600 waves passed over the antrum during the single digestive period. Movement'^ of the Pyloric Sphincter. — Ten or fifteen minutes elapse after the first constriction of the antrum before food appears 196 STOMACH DIGESTION. Fig. 109. Fig. 110. (Cannon, in American Journal of Physiology. MOVEMENTS OF THE STOMACH. 11)7 ^ Fig. 111.— Figs. 109. 110. and 111 present outlines of the shadow of the contents of the stomach cast on a fluorescent screen by the Rontgen rays. The drawings were made by tracing the outline of the shadow on tissue-paper laid upon the fluor- escent surface, and are about one- half the actual size. They show the change in the appearance of the stomach at intervals of half an hour from the time of eating until the stomach is nearly empty (Am. Jour, of Physiology). and that the constrictions in the duodenum. Tliis is spurted throutjh the pNdorusand shoots along the intestine for two or throe centi- meters. Not every constriction-wave forces food from tiie antrinn. In one of the experiments which were con- ducted by Cannon, about an hour after the movements began, three consecutive waves squirted food into the duodenum. The pylorus remained closed against the next eight waves, opened for the ninth, but closed again for the tenth and eleventh. In this irregular manner the food passed from the stomach. Cannon expresses the opinion that near the end of gastric digestion, when the constrictions are very deep, the pylorus may open for every wave. AVhen a hard bit of food reaches the pylorus, the sphincter closes tightly and re- mains closed longer than when the food is soft. On one occasion, dur- ing these experiments, when a hard particle of food reached the pylorus, the sphincter opened only seven times in twenty minutes. It is inferred from these results that hard morsels keep the pylorus closed and hinder the passage of the food into the duodenum. Activity of the Cardiac Portion. — The part played by the cardiac por- tion has not hitherto been properly appreciated. It has been regarded as the place for peptic digestion or as a passive reservoir for food ; but it is in fact a most interestingly ac- tive reservoir. Figs. 109-111 re|v resent the appearances the stomach presents at various stages in a diges- tive period. A comparison of them siiows that as digestion ])rocecds the antrum appears gradually to elon- gate and acquire a greater capacity, make deeper indentations in it ; but 198 STOMACH DIGESTIOS. when the funclus has lost most of its contents the longitudinal fibers of the aiitriini contract to make it shorter and smaller. The first region to decrease markedly is the pre-antral part of the pyloric portion. The peristaltic undulations, caused by the circular fibers, start at the beginning of this portion and gradually, by their rhythmic recurrence, push some of the contents into tlie antrum. As the process continues the smooth muscle-filjers with their remarkable tonicity contract closely about the food that remains, so that the middle region comes to have the shape of a tube (Figs. 110, 111, 1.30 p.m. to 5.30 p.m.), with the rounded fundus at one end and the active antrum at the other. Along the tube very shallow constrictions may be seen following one another to the pylorus. At tliis juncture the longitudinal fibers which cover the fundus like radiating fingers, and the circular and oblique fibers reaching in all directions about this s})herical region, begin to contract. Thus the contents of the fundus are squeezed into the tul>ular portion. This process, accompanied by a slight shortening of the tube, goes on until the shadow cast by the fundus is almost obliter- ated (Fig. Ill, 5.30 P.M.). This shows that the fundus is nearly empty, for there being but little subnitrate of bismuth in it, only a small shadow is cast. The waves of constriction moving along tlie tubular portion force the food onward as fast as they receive it from the contract- ing fundus, and when the fundus is at last emptied they sweep the contents of the tube into the antrum (Fig. Ill, 5 p.m. to 6 p.m.). Here the operation is continued by the deeper constrictions, till finally (in this instance, at 6.12 p.m.), with the exception of a slight trace of food in the fundus, nothing at all is to he. seen in the .stomach. The food in the fundus may possibly be slightly affected by the to-and-fro movements of the diaphragm in respiration. With normal breathing the upper border of the cardiac portion swings through about one centimeter ; with dyspnea, or deep breathing, through one and a half or two centimeters. Since the lower border does not move so much, the contents are gently pressed, and then relea.sed from pressure, at each respiration. Cannon calls attention to the observation made by Moritz with reference to the value of an organ like the stomach for holding the bulk of the food, and serving it out little at a time so that the intestines may not become congested during their digestive and absorptive proces.ses, and says that all of the advantages supposed to be thus secured to the intestines may be claimed for the stomach itself. The experiments above quoted prove that the stomach is com- posed of two physiologically distinct ]iortions. Tlie busy antrum, over Avhich during digestion constriction-waves are running in vomitim;. 190 oontinuous rliytlmi ; and the cardiac i)art, wliicli is an active reser- voir, j)ressin<^ out its ooiiteiits a little at a time as the antral niecliauism is reatly to receive them. Eff'cd of the MovemenU of the Stomach upon the Food. — 'J1ie experiments of Cannon demonstrate, in the cat at least, that the id(>a of Hcaumont that there is what may be called a circulation of food from thecardia alon<;- the (greater curvature to the pvlorus, and hack aloiii; the lesser curvature, and that of Jirinton that there are peripheral currents from the cardia along the walls of the stomach to the pylorus, and that these currents then unite and come back to the cardia as an axial current, are incorrect. What has been actually observed by Cannon shows conclusively that as the constriction-waves approach a i>iven })ortion of food, this latter is pushed forward in the direction of the pylorus, but not moving as fast as the wave, the constriction overtakes it, and as it passes it pushes the food backward, for in this direction is the least resistance ; the next wave pushes it forward a little further than the precedini>: one, and as it passes again it is pushed backward, but all the time it is making headway, though slowly, for the progress exceeds the backward movement. This to-and-fro move- ment is more marked in the antrum, where the waves are deep, than in the middle region. On different occasions the portions of the food under observa- tion have occupied from nine to twelve minutes in passing from Avhere the waves first affected them to the pylorus — i. e., on the way they Avere moved back and forth by more than fifty con- strictions. When the pylorus is closed, the food being pushed forward by the advancing constrictions, which are here very deep, and not being able to escape into the duodenum, is squirted back through the constricted ring. This process is repeated again and again until the sphincter relaxes and the fluid parts pass out, or if not rendered liquid pass into the duodenum later in a solid condition. The solid portions then remain in the antrum, to be here acted npon by the gastric juice, and to be subjected to the tireless rubbing of the muscular coat. In the above resume we have used the language of the experi- menter in describing his observations, condensing it where possi- ble, but endeavoring not to alter his interpretation of the experi- ments. Vomiting'. — The act of vomiting consists in an exj^ulsion of the contents of the stomach through the esophagus and the mouth. Before the expulsive act takes place there are connnonly nausea and an increased secretion of saliva. Then a deep inspiration occurs, caused by the descent of the diaphragm ; the glottis is closed by the contraction of the arytenoid and the lateral crico- arytenoid muscles ; and the posterior nares are closed by the con- 200 STOMACH DIGESTION. traction of the palatopliaiyiigei muscles or the posterior pillars of the fauces. The cardiac sphincter becoming relaxed, the cardia opens ; while the pyloric sphincter being contracted, the pyloric orifice is closed. The abdominal muscles now contract, and the diaphragm fanning a non-yielding wall above the stomach, this organ is so compressed that its contents are forced into the esoph- agus with sufficient power to carry them through the mouth to the exterior. Under some circumstances this force is sufficient to eject them into the posterior nares and out through the nose. Although the abdominal muscles are the principal factors in producing the expulsive movements, and indeed are in themselves sufficient, as was demonstrated by Magendie when he removed the stomach and substituted for it a bladder containing water, still there is also a contributing factor in the antiperistaltic contraction of the muscular coat of the stomach. Under some circumstances there is also an antiperistaltic w^ave in the muscular coat of the small intestine, by which its contents are forced into the stomach and then vomited. Whether this antiperistaltic action occurs or not in the muscular coat of the esophagus is a matter which is still unsettled. The above description, which fairly represents the modern views as to the act of vomiting, is modified by the investigations of Open- chonski on dogs and rabbits, and still more recently by Cannon on cats. The former's description is as follows : " As the result of an emetic there occurs a quickening of the walls of the stomach near the pylorus, which appears later in the antral and middle regions of the stomach. This becomes a contraction most marked in the antrum. The fundus enlarges in a spherical form, and into it the contents of the stomach are forced by these contractions of the antrum ; then follow the contractions of the abdominal muscles which force the contents into the esophagus." Cannon made his observations upon a cat, to which he gave apomorphin as an emetic. The upper circular muscles relax and become so flaccid that the slightest movement of the abdomen changes the form of the fundus. Then there are apparently irregular twitchings of the fundus wall. Soon a deep constriction starts about three centimeters below the cardia, and, growing in strength, moves toward the jndorus. When it reaches the trans- verse band the constriction tightens and holds fast, while a wave of contraction sweeps over the antrum. Another similar constric- tion follows. In the interval the transverse band relaxes slightly, but tightens again when the second wave reaches it. Perhaps a dozen such waves pass ; then a firm contraction at the beginning of the antrum completely divides the gastric cavity into two parts. This same division of the stomach into two parts at the transverse band is to be seen wdien mustard is given. Now, although the waves are still running over the antrum, the whole pre-antral EFFECT OF yEIiVUCS DISTUHnAXCES. L'nl part of the stoiiun-li i.s fully relaxed. A llatteniiij,^ oJ" the ilia- })lirai2^m ami a quick jerk of the abdominal muscles, accornpanied l)v the opeuiui; of the eardia, next Ibree the contents of the I'undus into the esophagus. .\s tiie spasmodic contractions of the abdomi- nal muscles are repeated, the atient's discharges after the operation. The urine and feces were examined every day at the chemical laboratory of the university. Products of abnormal intestinal fer- mentation or decomposition (skatoxyl and indoxyl) were either not at all found, or else discovered only in traces. " These observations tend to corroborate the views of von Noorden, while they negative the opinion held by Kast and Was- butski. The most recent results of laboratory experiments announced from Professor Baumann's institute, viz., that hydro- chloric acid inhibits intestinal decomposition, thus received no support from actual observations in the living human subject. " Does Removal of the Stomacli Affect the Bajtiditi/ of Intestinal Propulsion f — Observations on this point are still being made, and at the present time I am unable to present any very definite con- clusions. The patient objected to swallowing charcoal. Huckle- berries were at three different times found in the passages twenty- four hours after having been swallowed. " The Urine after the Operation. — Apart from a daily recurring diminution in the quantity of excreted chlorids, the urine of this Avoman has remained normal since ablation of her stomach. The daily excretion of chlorid of sodium has been found to vary be- tween the limits of 0.6 per cent, and 0.95 per cent. It should be stated in this connection, however, that, complying with the wish of the patient, her food is prepared with less salt than that of the other ward patients. " 3Iicroscopic Examination of the Feces. — The stools were well formed, of normal consistency, and light yellow in color. The microscope showed large numbers of fat-globules, and fatty crystals, some undigested vegetable-fibers, but no undigested animal-fibers or connective tissue. Large quantities of triple phosphates were observed. The number of micro-organisms was normal. Altogether, repeated examinations revealed no note- worthy departure from a condition of perfect health. " Vomiting unthout a Stomach. — How can a person vomit with- out a stomach? No matter what theoretic physiologic^ notions we may have imbibed from lectures and text-books, the woman REMOVAL OF TIIK II I'M AX STOMACH. 209 iimlt'i' ohsiTvatidii liiul r(|>cair(l attacks of ordinary nausea, retch- ing, and voniitinti'. We ninst needs eonelnde, tlieretnre, tliat the role of the stonuieli {i.e., its antiperistaltic etHcacy) in this direction has been very ninch overrated. While the vomited substances showed an acid reaction, this was not due to the presence of free hydrochloric acid. " In view of the fact that the i)atieiit ejected as much as thirty ounces at one time, it seems reasoualde to suppose that the remain- ing portion of the duodenum may have already begun to show distention sufficient to produce a sort of com])ensatory receptacle for food — iierhaps nature's attempt in the direction of the new formation of a stomach. " In endeavoring to e.\})lain vomiting without a stomach, we should remember that the act itself is far from being a simple process. It is due to nervous action on a complex motor appa- ratus, consisting of pharynx, esophagus, stomach, diaphragm, and abdominal muscles. " It is not surprising, therefore, to have witnessed in this woman an onlinarv attack of bilious vomiting superinduced by a mere physical disturbance." Conclusions by Dr. E. C. Wendt. — " While it would be mani- festlv unfair to indulge in sweeping generalizations on the strength of this single case, so bodly rescued and al)ly described by Dr. Schlatter, it seems at least justifiable to formulate the following conclusions : " 1. The human stomach is not a vital organ. " 2. The digestive capacity of the human stomach has been considerably overrated. " 3. The fluids and solids constituting an ordinary mixed diet are capable of complete digestion and assimilation without the aid of the human stomach. " 4. A gain in the weight of the body may take place in spite of the total absence of gastric activity. " 5. Tvpical vomiting may occur without a stomach. "(3. The general health of a person need not immediately deteriorate on account of removal of the stomach. " 7. The most important office of the human stomach is to act as a reservoir for the reception, preliminary preparation, and propulsion of food and fluids. It also fulfils a useful pur- pose in regulating the temperature of swallowed solids and liquids. "8. The chemical functions of the human stomach may be completely and satisfactorily performed by the other divisions of the alimentary canal. "9. Gastric juice is hostile to the development of many micro- organisms. " 10. The free acid of normal gastric secretions has no power 14 Fig. 11~ -Brigbam's case of removal of the stuinach : patient seven \v( the operation. ■ks after ^^^^^^^^^^^^^^^^^^^H^r^^vT^^E^flV^lBH ■tfifl^^K^''' Fig. 113.— Anterior view of stomach removed from patient in the preceding figure (Brigham). RKMOVM. OF THE III MAS STUMACll. 211 to arrest putrefiu-tive cliangos in the intestinal tract. Its antiseptic and bactericide potency has been overestimated." Brigham's Case. — Dr. Charles Ji. Jirijrhani, of San Francisco, California, on February 24, 189.S, completely removed the stom- ach from a woman, sixty-six years of age, affected Avith adeno- carcinoma of the stomach, involving one-half the organ, and sub- seqnently connected the esophagus with the duodenum, thus performing the operation of csop/iaf/o-duodenoHfomi/. This case is described by Dr. Jirigham in the Boston Medical ami Suiyical Jourmd of May 5, 1898, antl to this jcnirnal we are indebted for the details. In this case the operator was able to bring the duodenum up to the esophagus, which was not possible in Schlatter's case, and the two were approximated by means of a Murphy button (Fig. 114) instead of by sutures. Fig. 113 shows anterior view of the diseased organ after removal. After the operation the patient was nour- ished at first by enemata of i)randy and water, eggs, milk, and broths. During the evening of the day of the operation the patient vom- ited some bloodv mucus. On the following day hot water was given by the mouth, which relieved the intense thirst. On the second day claret and water, hot black coffee or chicken-broth was given, but after two teaspoonfuls there was no desire for more. On the third day double this quantity was taken each time, and on this day the bowels were moved for the first time. The nutrient enemata were given every four hours up to the fourth day, when they were discontinued. On the sixth day she was taking about 22 c.c. at each feeding, but could take no more. This quantity, however, w-as gradually increased. About three weeks after the operation she took for breakfast a cup of coffee with milk, a soft-boiled egir, and a third of a baked apple ; at noon, a cup of green-pea soup, a dozen small oysters, and an ounce of milk ; in the afternoon, some orange-jelly, one raw er^^, half a cup of pea soup, and a dozen oysters ; in the even- ing, half a cup of asparagus soup, Avith 14 c.c. of whiskey and 42 c.c. of wine. During convalescence the patient vomited food once, and on another occasion some mucus. About a month after the operation she complained of hunger, and ate a squab. About ten days later she ate in one day the following : At 6.30 a.m., cup of coffee and a raw eg^; at 10 a.m., two dozen small oysters and a Fig. 114. — Murphy but- ton (enlarged) : A, open ; B, clo.sed. 212 STOMACH DIGESTION. boAvl of broth; at 1 p.m., half a broiled chicken with toast, and stewed strawberries ; at 5 p.m.. half a broiled chicken, two slices of toast, and a cu]) of tea. DurinLT that week she gained six pounds. In concluding the history of this case Dr. Brigham writes : " In the treatment of this case no attempt has been made to predigest the nourishment which was given to the patient. The precaution was taken, however, to supply easily digested food ; and when meat was allo\ved it was cut in very small pieces. The food Mas taken slowly, Avhether liquid or solid. It is no hardship for the patient to live on simple food, for she has done so all her life ; and especially, as age has advanced, has been obliged to eat food that required the least chewing. The food was given of medium temperature ; water was taken as it came from the pipe and wine as it stood in the room ; iced cream, of which the patient Avas particularly fond, was taken slowly so that it dissolved in the mouth before it was swallowed. At first everything was too salt ; as the patient got well she wished salt on both eggs and oysters. The amount of flatus in the bowels was enough to cause pain only a few times in the early part of her illness. The urine has been normal throughout. Xever since the operation has any undigested food been seen in the movements from the bowels, and for the most part these have been Avholly or partly formed. The patient has vomited but a few times since the operation ; twice after etheri- zations, twice after some laxative had been given, once after the button left its place, and twice after coughing — not more than six ounces at anv one time, generally much less. On three or four occasions a mouthful of food would be regurgitated — an oyster, some shreds of meat, or a few teaspoonfuls of coffee. As a usual thing the food was well retained and well digested." On January 1, 1900, Dr. Brigham wrote to the author: "I am very glad to say that Mrs. M. is in excellent health, with no sign whatever of a return of the disease. On seeing her no one would ever believe that she had undergone any surgical operation, much less the removal of the entire stomach. She returned home seven weeks after the operation ; then she took five meals a day, consisting mainly of soups, oysters, eggs, milk-toast, baked apples, stewed prunes, iced cream, and strawberries. Little by little she chose what she liked — potatoes, peas, beans, lamb-chops, chicken, and fish. " I have always allowed her to choose her food, thinking that the success of the operation would be the better demonstrated. " For nearly a year she has kept house for herself, doing all her own work ; finding ample time to visit her grandchildren, who live near l)y. She is now in her sixty-eighth year, and afllirms that if she takes castor oil every ten days her health is perfect. " As to her weight, after the first year she weighed one hun- ACHYLIA GASTRICA. 213 dred and ten pounds ; last summer she gained two pounds. This weiirlit slie keeps at the present time." Achylia Gastrica. — Tiic fact that human heings can live and Ite apparently in })ertcet healtii, digesting all classes ot" iood- stutTs, and vet j)ossessint:; no stomach, as is sliown most notably in Dr. IJrigham's case, makes it (piite easy to believe that a similar normal condition may be maintained when the stomach is present, but a stomach which secretes no gastric juice. Such a condition of permanent absence of the gastric secretion is termed achi/lla gasfricd. This atfeetion has been tlescribed also under the names gastrifi.s fjldndularis atrophicans and progressive atropliy of the stomach. There are some cases in which the achylia is congenital, and others in which it comes on at middle life and in connection witii chronic gastric catarrh or some other affection. The admin- istration of test-meals demonstrates the al)sence of hydrochloric acid, pepsin, and rennin. Persons having achylia gastrica are often apparently in perfect healtii and eat everything they wish. The cases in which the stomach has been totally removed, taken in conjunction with these cases of achylia gastrica, all point to the conclusion that the small intestine is capable of carrying on all the digestive processes without any aid from the stomach. Still, it can hardly be supposed that the stomach is entirely a superfluous organ. Hemmeter, in discussing "The Logic of Hvdrochloric Acid Therapy," in American Medicine, AytrW 20, 1901, says: " The cases frequentlv noted in patients without any gastric secretion whatever who succeed in maintaining their nitrogen- equilibrium (and we have seen many such), and the experiment on the dog (Kaiser and Czerny), the weight of which Avas kept up, although the largest portion of the stomacii was removed, and Brigham's and Schlatter's total extirpations of the stomach, con- stitute but a weak argument against the tiierapy of HCl. For although such patients and animals manage to get along fairly well for a time, it is only under the most carefid and scientific supervision that their health is maintained. Permanent and perfect health with total alisence of gastric secretion is rarely ol)served, except in those wdio are able to rest much and have their food jn-epared with great care. " These facts must not be overlooked in considering the work of von Xoorden, which demonstrated that absolute and permanent deficiency of gastric juice may be accompanied by perfect health. This health is perfect under the conditions mentioned, but when such patients are taxed liv work or the diet is not the usual one, in ray experience suffering invariably becomes manifest. If achylia gastrica could really exist without any subjective or objective disturbances, how is it that so many of these jiatients consult the stomach specialists and are reported l)y them in lit- 214 STOMACH DIGESTION. erature? Wlien we iiiiist work for our living and cannot have the benefit ot" the dietetic kitchen at all times, we must have an active gastric juice to at least partially disinfect and dissolve our food, and a person mIio secretes no gastric juice is or soon becomes a patient. " In a recent article on achylia gastrica, by F. Martins and O. Lubarsch, the authors arrive at the conclusion that neither simple acliylia nor that dependent upon atrophy of the mucosa (anadenia) can bring about severe anemic or cachectic conditions, unless motor insufficiency, atropliy of the intestinal mucosa, or general diseases (tuberculosis, lues, infections, etc.) are added. Even if this is true, generally speaking, it does not disprove the statement that absence of HCl in the gastric secretion compels the individual to lead the life of a patient, for dyspepsia and dystrypsia may exist and become severe without the anatomic changes spoken of by Martins and Lubarsch. But, over and beyond this, Flint, Fen- wick, Quincke, Xothnagel, Osier, Kinnicut, also Rosenheim and G. Meyer, have described cases of pernicious anemia in which atropliy of the gastric mucosa was, at the autopsy, found to be the only organic disease existing. It is conceivable that the in- testine cannot persistently digest an amount of proteid sufficient to maintain the nitrogen-equilibrium during work; that it depends upon a certain part of this proteolysis to be performed by the stomach ; that the acid gastric chyme is necessary for the stimu- lation of the duodenal secretions. Pawlow has proved experi- mentally that the gastric HCl is an important stimidant to the secretion of pancreatic juice. It is probable that digestion in the duodenum is not perfect without the acid proteids, which, as we know, cause increased diastasic action of the pancreatic juice. So that we are justified in concluding on experimental and clinical grounds that in the absence of secretion of HCl in the stomach the entire dur)flenal digf-stion is al)norn)al."' Artificial Gastric Juice. — In addition to the observations upon man and lower animals already referred to, manv experi- ments have been carried on with an artificial gastric juice made by extracting the pepsin from the mucous membrane of the stom- ach of the pig with glycerin, and adding to this glvcerin-extract 0.2 per cent, of hydrochloric acid. The results of these experi- ments are, however, not to l)e regarded as identical with those that take place in the stomach of a living being. The factors in the prol)lem are many, and some of them are still undetermined. Effect of Alcohol on Digestion. — This subject has already been fully discussed, and the reader is referred to p. 155. STRUCTURE OF Till-: SMALL INTESTINE. 215 INTESTINAL DIGESTION. TliP intestinal canal extciuls from the stomach to the anus, and is divided into the duodennm, jejunum, and ileum, wliicii constitute the small intestine, which is about M meters in length, and the cecum, ct)lon, and rectum, constituting the large intestine, having together a length ot" 1.() Mucosa. Fig. 122.— From colon of man, showing glands of Liebcrkiihn : x 200 (Bohm and Davidoflf ). form of bands, a quite different arrangement from that in the small intestine. At the anus the circular fibers constitute the internal sphincter. The mucous membrane contains both solitary glands (Fig. 117) and glands which resemble the follicles of Lieberkiihn, and indeed are'called by that name by .some writers (Fig. 122); still the secretion differs very materially, not containing any enzymes 222 INTESTINAL DIGESTION. possessing digestive powers. The epithelium contains mucus- secreting or goblet-cells, and their jiroihiet is })rincipally mucus. Succus Kntericus or Intestinal Juice. — This is the secre- tion of all the glands of the small intestine ; but the follicles of Ijiel)erkiihn, being vastly more numerous tiian the others, con- tribute by far the greater part of the flui!^rT^ - Centro-acinal Connecti\e tissue. / ;^%- :^\ '^f'%, entro-acinal -\ » enirc Bj cell. — Intermediate tubule. -- Inner granu- lar zone of secretory cells. Fig. 128. — From section through human pancreas; X 450 (sublimate) (Bohm and Davidoff). 15 226 THE PANCREAS. Pancreatic Juice. — The most important changes which the food undergoes in the process of intestinal digestion are those which are due to the action of the pancreatic juice. This is tiie Intralobular — 'ik'^-'w duct. ^^^JB Fig. 129. — From section tlirough human pancreas : X about 200 (sublimate) (Bohm and Davidoff). product of the pancreas, and reaches the intestine by means of the pancreatic duct which, together with the common bile-duct, opens into the duodenum about 8 to 10 cm. below the pylorus. Centro-acinal cell. Secretory cell. Intermediate duct. Fig. 130. — Scheme showing relation of three adjoining alveoli to excretory duct, illustrating origin of centro-acinal cells (Bohm and Davidoff). Quantity of Pancreatic Juice. — The amount of this fluid secreted daily in the human being is not known, but it has been found that in the dog it is 2.5 grams per kilo of body-weight. This would give in a man weighing 70 kilos, 175 grams daily. PA NCE !■:. I 77 C .11 'ICE. 227 Composition of Pancreatic Juice. — Tlic puncTcatic juice has been obtaiiu'd rcjieatcdly from tlio dou; and the rabbit by tlie ()|K'ration of establishiiii; a permanent j)anereatic listnla. For tliis pin-pose that portion of the (hioch'num of a rabbit into which the main duct discharges, w hieh in this animal is about 35 cm. below the Fig. 131. — Stomach in place after removal of liver and mass of intestines: A, diaphragm; B, B'. thoraco-abdominal wall; (\ riglit kidney with c, its ureter; D, right suprarenal capsule; E, left kidney with e, its ureter; F, spleen; G, apon- euroses of transversales : H, //', quadrati lumhonim ; /, /', psoas muscles; A', esoph- agus : /„ stomach ; M, duodenum. 1, cardia ; 2, greater curvature ; 3, lesser curvature ; 4, great tuberosity or fundus; 5, small tuberosity or antrum of ])ylorus ; (j, j)ylorus; 7, right vagus; left vagus; 9, thoracic aorta; 9', abdoniinal aorta; 10, inferior dia- phragmatic arteries; 11, celiac axis; 12, hepatic artery; 13, right gastro-ei>iploic; 14, coronary artery ; 15, splenic artery ; 16, 16', su])erior mesenteric artery and vein ; 17, inferior mesenteric artery; 18, spermatic artery; 19, gall-bladder; 20, cystic duct; 21, hepatic duct; 22, inferior vena cava; 23, portal vein; 24, great sympa- thetic (Testut). opening of the bile-duct, is opened and a glass cannula is intro- duced into the duct and the secretion collected as it escapes. The amount thus obtained from rabbits is very small ; it is clear, color- less, alkaline, and does not clot. That obtained from fi.stulje in dogs is thicker, and coagulates on standing, although it is less thick after the fistula) have existed for some time. The specific gravity, 228 THE PANCREAS. Fig. 132. — Excretory ducts of the pancreas: A, pancreas, with a, its head; B, duodenum; C, jejunum; D, gall-bladder. 1, main pancreatic duct of Wirsung; 2, accessory duct with 2', its opening upon the postero-internal wall of the duo- denum ; 3, ampulla of Vater ; 4, common bile-duct ; 5, cystic duct ; 6, hepatic duct ; 7, aorta ; 8, superior mesenteric vessels ; 9, celiac axis with its three branches{Testut). too, falls from 1030 to 1010. The following table gives its com- position : Pancreatic Juice of Dog (C. Schmidt). Constituents. Water Solids Organic substances Ash Sodium carbonate Sodium chlorid Calcium, magnesium, and sodium phos- phates Immediately after From permanent establishing fistula. fistula. 900.76 980.45 99.24 19.55 90.44 12.71 8.80 6.84 0.58 3.31 7.35 2.50 0.53 0.08 Less is known as to the chemical composition of human pancre- atic juice. Herter obtained the fluid from an enlarged duct caused by carcinoma of the duodenum. In 1000 parts of this there were 24.1 parts of total solids, 17.8 parts of organic matter, and 6.2 parts of ash. Zadawsky obtained the juice from a young woman PANCREATIC JUICE. 229 from whom a tumor of tlie j)anercas had been romovod. The analysis of this was as foUows : Wat.T 8f;4.or, Organic substances 182.51 Proteids 'J2.0o Salts 3.44 Enzymes of Pancreatic Juice. — It is a remarkable fact that the pancreatic juice of all vertebrates, so far as examined, contains four enzymes : (1) amylolytic, (2) proteolytic, (3) fat-splitting, and (4) milk-curdlino'. A)ni/(oj)siti. — This is the amylolytic enzyme of the ])anereatic juice, and is regarded as identical with ptyalin of the saliva, although pancreatic juice has much greater amylolytic power than saliva, and acts upon uncooked starch ; but whether this is due to a difference in the enzymes or because in pancreatic juice the enzyme is more concentrated, has not been determined. Some authorities include them both luider the name of ptyalin. Amylopsin appears in the pancreatic juice for the first time about one month after birth, while ptyalin is present in the human parotid gland at birth, but in the submaxillary gland not until about two months subsequently. The optimum temperature for amvlopsin is from 30° (\ to 45° C, while between 60° C. and 70° C. it is destroyed. Its activity is greatest when the reaction is neutral or when a minute trace of acid is present, such as, for instance, 0.01 per cent, of hydrochloric acid. Its action on starch is to change it to mnltose and dextrose, or, under some circumstances, to maltose alone. Authorities who regard the action of saliva upon starch as being of comparatively little importance look to amylopsin and to the amylolytic enzyme of the intestinal juice as the principal agents in starch conversion. This we regard as a mistake, and are in- clined to place a much higher value upon salivary digestion than do thes(\ l)ut at the same time would give pre-eminence to the pancreatic juice as a starch converter. Trypsin. — This is the proteolytic enzyme of the pancreatic juice, and its power in this regard is greater than that of pepsin. It has been found in the pancreatic juice during the last third of fetal life. Its activity is greatest when sodium carbonate is present to the amount of al)out 1 per cent., although it acts when the reac- tion is neutral or very slightly acid. When hydrochloric acid is present to any considerable extent the enzyme is destroyed, and this is hastened when pepsin is also present. Trypsin has never been isolated, so that its chemical com- position has not as yet been determined. In the action of the cells of the pancreas, the zymogen trypsinogen is first formed, and this later becomes trypsin. In studying its action, a pancreas 230 THE PANCREAS. may be cut up finely and the enzyme extracted Avith glycerin, to which extract a solution of sodium carbonate of from 0.2 to 0.5 per cent, is added. Inasmuch as the pancreas and its extracts undergo putrefaction very readily, the glycerin preparation may be preserved by the addition of a few drops of an alcoholic solution of thymol. Tryptic Digestion. — The differences between peptic and tryptic digestion are quite marked. Pepsin requires an acid medium ; trypsin acts best in one that is alkaline. When peptic digestion of a solid proteid occurs, this first swells up and then gradually dis- solves, while in tryptic digestion there is no preliminary swelling of the proteid, but the erosion begins at once. In peptic diges- tion the proteid first becomes acid-albumin, then passes into the stage of primary proteoses, followed by that of secondary proteoses, and finally becomes peptones. In tryptic digestion it passes at once into the stage of secondary proteoses, and then on into peptones. These peptones are sjioken of as ampho- peptones, because there are at least two of them, anti-peptone and hemi-peptone. The action of pepsin stops when these are formed, but trypsin can act still further by splitting up the hemi- peptone into a number of substances, among them leucin, tyrosin, aspartic acid, tryptophan, and lysatinin. What office these sub- stances have in the body, if any, is as yet undetermined, though it is probable that a portion of the urea found in the body is derived from lysatinin. The changes which proteids undergo in tryptic digestion are well shown in the following scheme of Xeumeister : Proteid. Deutero-alburaoses (proteoses). 1 Ampho-peptones. Anti-peptone. Hemi-peptone. Leucin. Tyrosin. Aspartic Acid. Tryptophan. Lysatinin. Steapsin. — The fat-splitting or lipolytic enzyme of the pancre- atic juice, steapsin, is sometimes termed pnahjn. Its action has already been described in connection with sa)ionification (p. 100), and consists in the taking up of water by the neutral fats, which then " split up," glycerin and a free fatty acid being the result. The evidence that the pancreatic juice has this power is unques- tioned^ and that it is due to the presence of an enzyme is proved lyyj.'jiVA'jioy of tiii: I'Ascreas. 231 by the fact tliat hoiling tlestroys this power, and by the further fact that it eannot be due to bacteria, for antiseptics do not aH'ect it ; lU'vertheh's.s, the kiiowledij^e as to its properties is very nieaj^er. Its action upon fats is very rapid, and it is ju'obable tliat " it is capal)le of sj)littini; up all the fat of a full meal in the ordinary time of digestion within the body." The presence of bile, by virtue of its contained bile-salts or bile-acids, increases its activity, and this is still t^reater when hydrochloric acid is present. J'Jinu/.sifi/iiif/ Poicer of Pancreatic Juice. — One of the offic^es performed i)v the pancreatic juice is to make an emulsion of fats which form an important part of the food. This action is not due to any enzynu', but to the formation of fatty acids by the steapsin ; intleed, this is regarded by some authorities as the chief ottice of the lipolytic enzyme. The splitting up of fat is in and of itself of no great physiologic importance, inasmuch as only a part of the fat is thus split up, but the fatty acids which result, together with the fatty acids which the fats themselves con- tain, bring about the emulsilication of the main portion of the fat, which process is, according to some authorities, so essential in pre- paring it for absorption. Of the theories propounded to explain fat absorption, we shall speak later (p. 253). The fatty acids resulting from the decomposition of the fat unite with the alkaline salts in the small intestine, probably those of the bile and the intestinal juice rather than those of the pancreatic juice, and form soaps, Avhich, aided by the peristaltic movements of the intestine, convert the fat into an emulsion. The proteids of the pancreatic juice take no part in this emulsifving process, but it is very materially aided by the presence of the bile, inas- much as bile and pancreatic juice acting together split uj) fat much more quickly than the juice alone. In what manner soaps act to emulsify fats is not known. Some have supposed that the soap forms a film around the fat-glol)ules after they have been finely divided, which prevents their uniting; but the formation of such a film has never been demonstrated. Moore, in Schjifer's Physiology, says that the very fine subdivision of the fat and the increased viscosity of the menstruum occasioned by the dissolved soap, are quite sufficient to explain the per- manency of emulsions of fat. Milk-cnrdlincf Enzyme of the Pancreatic Juice. — Milk, to which an extract of the pancreas has been added, coagulates, and the term pancreatic casein has been applied to this precipitate. It is probably a substance intermediate between casein and caseinogen. The coagulating aorent is considered to be an enzyme, though nothing definite is known about it. Innervation of the Pancreas. — The nerves which supply this organ are from the celiac ])lexus of the sympathetic, together with some fibers from the right vagus, and are non-medullated 232 THE PANCREAS. and gangliated. When food enters the stomach of a dog, almost immediately the secretion of pancreatic juice begins, and is at a maximum in from one to three hours. It then diminishes until about five or six hours after the meal is taken, when it again increases until the ninth or eleventh hour, and again diminishes until the sixteenth or seventeenth hour, when it is practically nil. Fig. 13-3 shows this in the dog. Just what the facts are in man is unknown, although it is believed that the secretion begins about the time of entrance of food into the stomach ; but its increase and IS iz II 10 0.9 08 0.7 0.6 05 O.'i- 0.5 OSi 01 Fig. 133.— Curve of the secretion of pancreatic juice during digestion. Tlie figures along the ahscissa represent hours after tlie beginning of digestion : the figures along the ordinate represent the quantity of this secretion in cubic centi- meters. Curves of two experiments are given (after Heidenhain). I\ \ \ \ \\ T \ \ V j \ \ / / 1 1 \. 1 1 1 1 1 \ ' 1 1 \ \ / 1 \/ O Z 3 ■' ^ $ i ^ / ' i. 1 1 1 1 1 Z 1 i I H- 1 5 / fr / 7 h f diminution would, doubtless, vary very materially from those of the dog, which was fed but once during the day. The above facts tend very conclusively to prove that the secre- tion of pancreatic juice is a reflex act, brought about by stimula- tion of the afferent fibers of the mucous membrane of the stomach or inte.stine, or both. It is also probable that the acid of the gas- tric juice is the stimulus wliich brings about this activity of the gland. It seems also to have been proved that there are true secretory fibers along which efferent impulses pass to the gland ; certainly stimulation of the vagus or sympathetic brings about a secretion of pancreatic juice. It has been suggested that there are also inhibitory fibers to the pancreas, but this is as yet unproved. THE LIVER. 233 Internal Secretion of the Pancreas. — This oroun has been removed from animals without i)ro(hicing an immediately fatal result, but in every sueh case sugar has appeared in the urine, produeimj; a condition denominated glycosuria^ and this, too, when no carbohydrate was jiresent in the food. The urine has also been increased in quantity, thirst and hunger have been marked, and emaciation and muscular weakness have set in, with death resulting in one or two weeks. If the gland is not entirely removed, so little as one-fourth or one-fifth being left, glycosuria does not occur, and, what is still more remarkable is, that after the removal of the gland, if a portion of it is grafted under the skin, or if the ducts arc closed so as to prevent the secretion from entering the duodenum, glycosuria is also absent. All of which goes to prove thai besides the pancreatic juice, which may be re- garded as the external secretion of the pancreas, it also produces an internal secretion which, taken up by the blood or lymph, either aids in destroying the sugar ])roduced by the liver or muscles, or else inhibits the glycogenic function of these organs. The cells which are believed to form this secretion have been described in connection Avith the pancreas (p. 225). THE LIVER. This organ is situated in the abdominal cavity, and is as large as all the other glands of the body taken together. Its transverse diameter is 28 cm., antero})Osterior diameter, 20 cm., and vertical diameter, 6 cm. (Fig. 134). Its blood-supply is from the portal Gastric sur- face. Tuber ]iapillart'. Tuber omeutak'. ~^ Non-peritoneal surface. Imp. supra-ren. (non-perit). Imp. supra-ren. Inii)ressio renalis. Imp. duodenalis. Impressio celica. Impressio pylorica. Fig. 134. — Posterior and inferior surfaces of tbe liver. vein and hepatic artery, while its nervous supply is from the left vagus and celiac plexus. It is covered by the peritoneum, and beneath this is the fibrous coat, which, at the transverse fissure, is continuous with Gllsson's capsule. This connective-tissue envelope covers the hepatic artery, portal vein, and hepatic duct, and accom- panies them through ]>assnges in the liver, i\\e portal canals. Chemical Composition. — The liver during life is alkaline, 234 THE LIVER. but after death becomes acid, owing to the formation of sarcolactic acid. Its percentage-analysis is as follows (von Bibra) : Water 76.17 Gelatin 3.37 Insoluble tissues 9.44 Extractives 2.40 Proteids 2.40 Fats 2.50 Inorganic constituents .... 1.10 Proteids. — These are a globulin (cell-globulin) coagulating at 45° to 50° C. ; another globulin, coagulating at 70° C. ; a nuclco- proteid coagulating at about 60° C, which, when injected into the blood-vessels, causes coagulation of the blood ; and an albumin. Extractives. — These are urea, uric acid, xanthin, hypoxan- thin, and jrcoriit. This last constituent contains phosphorus, and has the following formula : C^-HiggN.SPgO^s. It resembles lecithin, but, unlike that sul)stance, reduces Fehling's solution. It is not confined to the liver, but is also found in the spleen, nuiscle, and brain. The liver also contains a nuclein, with which iron is in combination, called ZalesWs hepatin and also Schmiedeberg^s fer- ratin. Iron is present in the liver of young animals in greater proportion than in old ones, and it is stated that animals are born with iron in both liver and spleen. This iron meets the demand of the body until the use of milk is given up, this fluid being poor in iron. Structure. — The liver is made up of five lobes, which are composed of loliules each having a diameter of about 1 mm., and these in turn contain hepatic cells, polyhedral in shape, the secret- ing elements of the liver, each having a diameter of about Jjj- mm., and containing a nucleus. The protoplasm contains glycogen and iron-containing pigment-granules, and may also contain fat. Nerve-fibers are described by some histologists as terminating between the cells, but not passing into their interior. The lobules are separated by connective tissue, which is abundant in the pig, but much less so in man. Hepatic Artery. — The hepatic artery is a branch of the celiac axis, and enters the liver at the transverse fissure, dividing here into two branches, right and left, which go to the correspond- ing lobes. This artery furnishes nutrition to the coats of the large blood-vessels, the ducts, the membranes of the liver, and to Glis- son's capsule. It also gives off branches, interlobular branches, which pass between the lobules and give off lobular branches. These enter the lobules and end in a capillary network between the cells. Whether, however, any blood is carried by these vessels directly to the network is in di.spute. Portal Vein. — This vessel also enters the liver at the trans- verse fissure, dividing into two, each branch going to the corre- sponding lobe, and following the course already described as being taken by the hepatic artery and its branches. The termination HEPATIC DUCT. 235 of the portal vein forms the inUr/oha/ar plexus, wliieh, as its name implies, is in the connective tissue, between the lobules. From this go off vessels which run to the center of the lobule, being connected by transverse vessels, the whole forming a capillary network, in the meshes of which are the hepatic cells. The blood which passes through this network is discharged at the center of the lobule into the hitralohidar or central vein, which, at the base of the lobule, enters the suhlobular vein. In a similar manner all the intralobular veins discharge, and the sublobular veins unite to form larger veins, which terminate in the hepatic The same, -fr* cut trans versely. Anasto- v>' moses be- tween ves- sels of several lobules. Fig. 135. — Section through injected liver of rabbit. The boundaries of the lobules are indistinct ; X about 35 (Bohm and Davidoff). veins, which, as three large trunks and some small ones, discharge into the vena cava, at the back of the liver. Hepatic Duct. — Between adjoining hepatic cells are small passages, intercellular biliary iiassages or bile-canaliculi, which are the beginnings of the hepatic duct (Fig. 137). It would be more correct to say that the beginnings of the hepatic duct are within the hepatic cells themselves, for it has been demonstrated that in the interior of these cells are vacuoles which communicate with the bile-canaliculi (Fig. 137). The canaliculi pass outward to the interlobular spaces, where they form an interlobular biliary plexus, from which ducts are given oiff that enter the portal canals, and, covered with Glisson's capsule, in company with the branches of 236 THE LIVER. the portal vein and hepatic artery, they emerge from the liver at the transverse fissure as two trunks, right and left, which unite to form the hepatic duct. This is from 3 to 5 cm. in length and has a diameter oi about 4 mm. The bile-canaliculi have no wall save such as is made by the hepatic cells. The interlobular ducts have a wall of connective tissue lined with columnar epithelium. In the larger duct is fibrous and plain muscular tissue. The ducts in the portal canals have opening into them cecal diverticula, which are regarded by Sappey as mucous glands. Gall-bladder. — The gall-bladder lies on the under surface of the liver in the fossa vesicalis, being attached thereto by vessels and connective tissue. The neck of the gall-bladder terminates in the cystic duct, which is spiral in form, and unites with the Intralobular vein. Fig. 136.— Section through liver of pig, showing chains of liver-cells; X 70 fBohm and DavidoiT). hepatic duct to form the ductus cJiolcdochus or common bile-duct. The cystic duct, from the neck of the gall-bladder to its union with the hepatic duct, is 3 to 7 cm. long, and has a diameter of 2.3 mm. The length of the common bile-duct depends upon the point at which the cystic and hepatic ducts unite, which is not uniform. The following measurements are given : 7 to 8 cm. (Sappey) ; 2 to 4.5 cm. (Luschka) ; 6 to 7 cm. (Joessel). Its diameter is from 5.6 mm. to 7.5 mm. The coats of the gall-bladder are three : serous or peritoneal ; fibro-muscular, made up of fibrous tissue with plain muscular fibers arranged both longitudinally and transversely, the former greatly predominating; nud mucoiis. This last, which forms the internal coat, presents a honey-comb appearance. It is covered with columnar epithelium. The mucous membrane of the cystic BILE. 2P.7 duct forms folds which bear some rcscnibhince to tlio valviilaj conniventcs of the small intestine. These folds are called ra/vu/a Heisteri or the valve of Heister. The mucous membrane is con- tinuous with that lining the hepatic and common bile-duct. Bile. — This is one of the products of the cells of the liver; Fig. 137.— Diagram of a segmeut of an liei)atic lobule: 1,1. interlobular portal vein ; 2, central vein ; 3, 3, intralobular cai)illaries ; 4, 4, interlobular hepatic artery; 5, .5, ramifications of hepatic artery, contributing to the formation of the intralobular capillaries ; 6. 6, interlobular bile-duct ; 7, 7. its ramifications in the lobule, forming a plexus of intercellular canaliculi ; 8, 8. section of biliary canal- iculi with their intercellular capillaries : 9. 9. hepatic cells : 10. 10. interlobular lymphatics, receiving the intralobular lymphatics; 11, 11, 12. intralobular con- nective tissue (Testut). as it is secreted it passes through the he])atic and cystic ducts into the gall-bladder, where it is stored until needed at the time of intestinal digestion, when it is discharged through the common bile-duct into the duodenum by an opening common to it and the pancreatic duct. Properties of Bile. — The bile is a constant secretion — i e., the liver-cells are constantly producing it, although it leaves the liver 238 THE LIVER. intermittently, being forced out by the contraction of the muscular tissue in the walls of the bile-ducts. Some authorities state that it flows continuously into the intestine. But whether this is so or not, the greater part is stored up in the gall-bladder during the intervals of digestion, to be expelled therefrom during the diges- tive process. \\'hen the bile leaves the liver it is a clear fluid with a specific gravity of 1010. During its stay in the gall-bladder it becomes viscid, and loses some of its water and inorganic salts, certainly Fig. 138. — View of duodenum and pancreas. The part of stomach removed is indicated by dotted lines: A. quadrate lobe: B. right kidney; C. C", right and left suprarenal capsules; D. left kidney: E. pancreas; F. upper part of stomach; G. spleen: H. duodenum, with n. b. c, d, e. its five parts; /.jejunum; A', duodeno- jejunal angle. 1, lower end of esophagus; 2. pyloric orifice: 3. celiac axis; 4, coronary artery; 5, hepatic artery; 6. Spigelian lobe of liver: 7, 7', splenic ves- sels : S, left gastro-epiploic artery ; 9. right gastro-epiploic artery ; 10, superior mesenteric vessels; 11, portal vein; 12, hepatic duct; 13, cystic duct; 14, gall- bladder: 15, left crus of diaphragm; 16, aorta: 17, vena cava inferior; 18, inferior mesenteric vessels ; 19, spermatic vessels (Testuti. some of the chlorids, which are absorbed by the gall-bladder, and its specific gravity is increased to 1030 or 1040. The viscidity in human bile is due to mucin, but that of ox's bile is due to an in- gredient which was formerly thought to be mucin, but is now regarded as a nucleoproteid. That it is not mucin is shown by several facts: the nitrogen is from 14 to 16 per cent, higher than in mucin, and when boiled with a mineral acid it does not yield a reducing sugar. This substance is formed by the epithelial cells liuiui:: the gall-bladder. BILE. 239 Tlio bile is alkaline in reaction, sodium carbonate and alkaline sodium phosphate being present to the extent of about 0.2 per 10(^0. Its color varies: in heri)iv()rous animals it is oreen ; in carnivorous animals golden yellow or golden red ; w hilc in man it is of a golden yellow, though often green. Constituents of the Bile. — The chemical composition of the bile varies in the same individual at different times, and this differ- ence depends, to a considcraldc extent, u])on the length of time it remains in the gall-bladder. Analyses will, therefore, vary materially, according as the .secretion is removed through a fistula of the l)ile-duct, in which case it would come directly from the Fig. 139. — Portion of gall-bladder and bile-ducts: 1, cavity of gall-bladder; 2 cavity of calyx; 3. groove separating the calyx from the bladder; 4, promontory 5, superior valve of calyx ; 6, cystic canal ; 7, common bile-duct ; 8, hepatic due (Testut). duct liver or from the gall-bladder after having been stored there for some time. The table on page 240 gives the results of various analyses of bile which have been made by competent chemists. Bile-pigments. — These are two : bilirubin and biliverdin. Both of these are present in bile, but if the color is of a reddish brown, as in the carnivora, the bilirubin predominates, while the predomi- nance of the biliverdin gives the greenish hue, the characteristic color of the bile of the herbivora. The formula for bilirubin is CigHi^NjO,, or, as given by some writers, Cs-jHagX^Og ; that of biliverdin, CjgHigN.p^ or C^M^^^iO^ — ^. e., the former passes into 240 THE LIVER. Composition of Normal Human Bile. Bile from fistula. Bile from gall-bladder immediately after death. Copeman and Winston. Frerichs. Gorup-Besanez. Water • Total solids Sodium olyeocholate . . Sodium taurocholute Cholesteriu Lecithin Fats Soaps Mucin, pigment, etc. Inorganic .salts .... 985.77 14.23 I 6.28 1 I 0.99 J 1.72 4.51 860. 140. 102.2 1.6 ' 3.2 822.7 177.3 107.09 I 47.3 26.6 22.1 6.5 10.8 the latter by oxidation. It is because of a reduction in tlie bili- verdin that the greenish cohjr of fresh human bile becomes red- dish after it has remained for some time in the gall-bladder. In clots of blood that are old, crystals are found to which the name hemafoidin was given by Virchow. This is identical with bilirubin. Indeed, it is now conceded that the pigments of the bile are derived from hemoglobin, the coloring-matter of the blood. Thus one of the functions of the liver-cells is to change the hemoglobin which comes from broken-down red blood-corjjuscles to bile-pigment, separating from it the iron and preserving it for future blood-making. Neither bilirubin nor biliverdin shows any absorption-bands with the spectroscope. Gmelin's Test for Bile-pigment. — If diluted bile, or a solution containing bile-pigment, is poured into fuming nitric acid — /. e., nitric acid containing nitrous acid, wiiich is a powerful oxidizing agent — there will be produced a set of rings or zones of diiferent colors, according to the amount of oxidation of the bilirubin. The zone next to the acid will be the most oxidized, and will be of a yellow-red color : the product is eholetelin, CigHjgNjOg. Above this will be a zone of red or purple, becoming blue : this product is called bilici/anin ; above all will be a green zone, biliverdin, which beincr farthest from the acid has underg^one the least oxi- dation. This constitutes Gmelin's reaction, and is employed to detect the presence of bile-pigments, as in the urine. A modified form of applying this test consists in wetting a piece of filter-paper with bile, or the solution which is suspected to contain bile, and dropping the fuming nitric acid upon it, M'hen the character- istic colors will appear. Biliary urine gives an absorption spectrum showing a wide band beginning at the red side of D and ending between D and E. Choletelin gives a band between C and F. Hydrohilirubin. — This substance has the formula CgjH^oN^Oy. r.ILE. 241 It is a reduction-procliiet of bilirubin, and is oI>taiiK.'(l bv the action of nascent iiyilroiron, from sodium amalt^am, in an alkaline solution of bilirubin. It g:ives an al)sorption s|)eetrum, a dark band between C and F. It is with difficulty oxidized to bilirubin or biliverdin. Although bilirubin and l)iliverdin as constituents of the bile enter the intestine, still neither is found in the feces, but hydrol)ilirubin is there found, which is undoubtedly derived from the bile-pigments. This pigment of the feces has been described as stcrcobUia. A similar pigment in the urine is uro- bilin, antl it is now claimed tliat hydrobilirubin, stercobilin, and urobilin are one and the same substance. As already stated, it is l)elieved that bilirul)in comes from hemoglobin, the coloring-matter of the blood. In the liver this is decomposed into a proteid and hematin, the latter containing iron. The hematin takes up water, the liver-cells remove the iron, and bilirubin is formed. This may be expressed by the fol- lowing equation : C3,H3,XpFe + 2Hp - Fe = Q,M^^,0, or 2(C,,H,,XA). Hematin. Water. Iron. Bilirubin. Bile-salts. — These are sodium glycocholate and sodium tauro- cholate — i. e., sodium united with glycocholic acid, CjijH^NOg, and taurocholic acid, C.^H^-XSO-. These acids are known as bile-acids. Both occur in human bile, as a rule, though taurocholic acid may be absent. AVhen o-lvcocholic or taurocholic acid is boiled with an acid or an alkali, it takes up water and then splits up, or, as it is expressed, " undergoes hydrolytic cleavage," into cholic or chola- lic acid and an amido-acid — /. e., an organic acid, one or more of whose hydrogen atoms is replaced by amidogen (XH,). Glyco- cholic acid produces glycocoll or amido-acetic acid, and cholic acid ; while taurocholic acid yields taurin or amido-ethylsul phonic acid. Tills is represented by the following equations : Glycocholic acid. Water. Cholic acid. Glycocoll. C,eH,,XSO, + H3O = C^H^O^ + C,H,XS03. Taurocholic arid. Water. Cholic acid. Taurin. ♦ A similar decomposition of the bile-acids is believed to take place in the intestine, with the production of cholic acid. Pettenhofer's Test. — When cane-sugar and strong sulphuric acid are added to bile or a .solution of Ijilc-.salts a purplish or red- dish-violet color is produced. This is due to the action of the sulphuric acid on the cane-sugar, producing furfural or furfur^ aldehyd, and this acting upon the cholic acid gives the characteris- tic color. In applying this test the temperature should be kept 16 242 THE LIVER. below 70° C, and not too mnch cane-sugar added, otherwise it will undergo carbonization. The usual way of performing this test is to add to a few drops of the fluid in a porcelain capsule a drop of strong sulphuric acid, and spread out the mixture ; then add to this a drop of a 10 per cent, solution of cane-sugar. If the color does not appear, the capsule should be warmed. Inas- much as the test depends upon the reaction between furfural and cholic acid, instead of using cane-sugar, a drop of a 1 : 1000 solu- tion of furfural may be added to 1 c.c. of an alcoholic solution of bile-salts, and to this 1 c.c. of concentrated sulphuric acid, care being taken as before to keep down the temperature. It is said that the presence of -^^ to -^^ of a milligram of cholic acid may be recognized by the furfural test. Unfortunately, Pettenkofer's reaction alone cannot be relied upon as a test for the bile-salts, inasmuch as proteids and other substances to the number of forty will give the same color. The color produced by cholic acid may, however, be distinguished from that produced by all other substances by its spectrum ; two bands, one between the solar lines D and E near to E, and the ■other at F, The bile-acids are formed by the cells of the liver ; probably from some albuminoid or proteid constituent. They are absorbed by the intestine and are not excretory products, but have various offices to perform and for which they are produced ; just what these are has not been definitely determined, but it is regarded as probal)le that among other offices is that of dissolv- ing the cholestcrin, which would otherwise be insoluble. Other offices wnll be referred to in connection with the discussion of the offices of the bile as a whole. Choksterin. — The formula for this substance is CagH^^jO. It is found not only in bile, but also in nervous tissue and in the cells of plants and animals (p. 101), where it results from the kata- bolic processes taking place in them. It is brought to the liver by the blood, and is not formed in that organ. It is an excretory product, and the function of the liver, so far as this sui)stance is concerned, is to eliminate it. It undergoes no changes in the intestine, but is excreted as cholesterin in the feces. Lecithin. — This is another of the constituents of the bile which, like cholesterin, is derived from nervous tissue, and mIiosc elimina- tion from the blood is brought about by the liver-cells. Oflaces of the Bile. — The amount of bile which is daily secreted, l)eing about 800 or 900 grams in the human subject, would indicate that its offices in the body must be important. It is a remarkable fact that a single anatomic element can perform so many varied functions as does the liver-cell. (1) It secretes the water of the bile; not alone, for the cells of the bile-ducts and possibly those covering the lining of the gall-bladder aid in this process. (2) It forms the bile-salts. (3) It forms the bile-pig- BILE. 243 nu'iits. (1) Jt separates eliolcslcriii anower. it has considerable power of absorption. BACTERIAL DIGESTION. Bacteria are found in consideral)le numbers in the mouth, stomach, and intestine ; more than sixty species are recorded by Sternberg as having been found in the mouth ; and seventy- four have been isolated from feces and the intestines of cadavers. ABSORPTION OF Till-: FOOD. 245 Tliosf wliicli occur in tlie stomach consist of iiiouth-baotoria wliicli have been swallowed tofjcthcr with bacteria which are in the food and drink. Wc have already referred to some of the pathojrenic or disease-producing bacteria, and the effect of hydrochloric acid upon them (p. 191). But besides these there are others which have a true digestive action on the food-stuffs. Inasmuch as there is no free hydrochloric acid in the stomach for about half an hour after food has entered it, the antiseptic action of this acid is not exerted for that length of time, and the conditions are favorable for bacterial action. During this time some of the carbohydrates may l)e decom- posed, with the result of producing lactic and other acids and set- ting free hydrogen gas. Proteids do not, however, aj>])ear to be acted upon by bacteria in the stomach. In the small intestine there is some decomposition of proteids, but not to any considerable extent. Lactic and other organic acids are, however, produced from carbohydrates. These changes in both proteids and carbo- hydrates arc due to the action of bacteria. The action of the intestinal bacteria upon proteids has been likened to that of trypsin. The proteid is dissolved, and then changed into albumoses and peptones. A part goes on to the stage of tyrosin, which becomes still further decomposed into paraoxyphenylpropionic acid, paraoxyphenylacetic acid, phenol, and parakresol. From another portion of the proteid are formed indol, skatol, and skatolcarbonic acid. These substances are not derived from tyrosin nor, indeed, from peptones, but from some unknown intermediate substance derived from the proteid itself. All of the carbohydrates of the food seem to be subject to bacterial action. Thus starch and even cellulose may be decom- posed by the appropriate bacteria. As results of carbohydrate decomposition are produced ethyl alcohol, lactic, butyric, and succinic acids, together with cariion dioxid and hydrogen. The fats are normally unchanged by bacterial action ; in the absence of bile or pancreatic juice they are decomposed, with the formation or fatty acids. ABSORPTION OF THE FOOD, Attention has already been called to the fact that a large part of the food-stuffs taken into the body are not in a condition to be absorbed by the blood, nor to be utilized by the tissues when brought to them by that fluid (p. 162), and that digestion consists in bringing about the changes in them necessary to effect this result. It is these changes which we have studied, and which will prepare us to understand the process of absorption. iNIanifestly, absorption might take place anywhere in the ali- mentary tract from the mouth to the anus, but it has been demon- 246 ABSORPTIOS OF THE FOOD. strated that in some portions of this canal very little absorption, if any, takes place, and that in others the greater part of the proc- ess is carried on. Mouth-absorption. — Under ordinary circumstances there is no absorption while substances are in the buccal cavity. This is certainly true for the food-stuffs, though that it may occur for some other substances is proved by the fact that cyanid of potassium taken into the mouth and retained there Mill produce death. There is likewise no absorption while food is passing through the esophagus ; the time occupied in the transit is altogether too brief, and the conditions irenerally are unfavorable, . Gastric Absorption. — The food-stuifs which enter the stom- ach are: (1) inorganic, water and salts; (2) carbohydrates, starch and sugars : (3) fats or oils ; and (4) proteids. Inorganic Food-stuffs. — Water taken into the stomach by itself is not absorbed to any extent by that organ. Yon Mering demon- strated this in a dog in which he first established a fistula in the duodenum, and then gave it by the mouth 500 c.c. of water. Almost as soon as it reached the stomach it was forced out by contraction of the muscular coat into the duodenum in spirts, and in twentv-five minutes 495 c.c. passed out through the fistulous opening in the intestine. When water contains in solution sub- stances which are absorbed by the stomach-walls, some of the water is also absorbed with them. The evidence as to the absorption of salts is very incomplete. Sodium iodid in 3 per cent, solution is absorbed, but to a slight extent if the solution is more dilute. Many substances, such as mustard or alcohol, hasten its absorption, probably by stimulating the epithelium. Carbohydrates. — Starch is not absorbed as such, but must be chanoeJ into maltose, which process, as we have seen, does take place to no inconsiderable extent in the stomach ; although it also is carried on more energetically in the small intestine. All varie- ties of sugar — dextrose, lactose, saccharose, and maltose — are absorbed in the stomach, and this is also true of dextrin. Some of the saccharose is inverted to dextrose and levulose in tlie stomach, and doubtless absorbed in this form to some extent, while the rest of it undergoes the same change in the small intes- tine. It is essential, however, that the solution should be concen- trated ; at least this is true of dextrose, of which very little is absorbed until the concentration equals 5 per cent., and the rate of absorption increases up to a concentration, of 20 per cent. Alcohol causes increased absorption of sugar, as it does of sodium iodid, and doubtless for the same reason. Taken as a whole, the amount of the sugars absorbed from the stomach is probably not great. ABSORPTloy r,Y THE SMALL INTESTINE. 247 ♦ Peptones. — TIksi- arc also absorlx'd from the stomach, though, as in the case of dextrose, only when the concentration reaches 5 per cent., so that the al)sor[)tion of peptones from the stomach is relatively small. Fats and Oils. — \\'ith the exception of the physical change, due to the temjK'rature of the stomach, by which the fats and oils are rendered more Huid, no change takes ])la('e in them, nor are they absorbed to any extent whatever. Alcohol. — The fact that alcohol is readily absorbed from the stomach has been sntliciently dwelt upon (p. 157). From the above considerations it will be seen that gastric ab- sorption is not a process of much importance ; indeed, the cases of the entire removal of this organ, to which we have referred, demonstrate that the exercise of what little absorptive power it possesses, is unnecessary. We desire to direct special attention to the fact that sodium iodid, dextrose, and peptones are more readily absorbed when alcohol is also present. This empha- sizes the view now held as to absorption, — that it is not a mere matter of osmosis, but is due to an actual selective power of the epithelial cells, and that this is more actively exercised under the stimulating action of alcohol or other substances having like power. Absorption by the Small Intestine. — It is from the cavity of the small intestine that the greater part of absorption takes place, the products of digestion passing into the villi, a part entering the capillary blood-vessels and reaching the liver tlirough the portal vein ; while another part enters the lacteals, and passes on into the thoracic duct, from which it is discharged into the blood-vascular circulation. While osmosis is doubtless one of the factors in this process, still the selective power of living cells is much more potent. The materials to be absorbed are (1) water; salts; (2) carbo- hydrates ; (3) proteids ; (4) fats. Absorption of Water. — As was stated in connection w'ith gastric absorption (p. 246), water is not absorbed to any extent from that organ, most of that taken in being passed on into the small intes- tine. Experiments have shown that the water which enters the small intestine is absorbed by the capillaries of the villi ; and yet even when large quantities are absorbed, an analysis of the blood shows no change, as might be expected, the excess being elimi- nated by the kidneys. Absorption of Carbohydrates. — The dextrose and levulose, formed by the action of the enzymes, are absorbed by the veins and carried by the portal vein to the liver, but there is evidence that saccharose, and even dextrin and starch, can be taken up by the cells ; although, as we have seen, the action of the intestinal enzymes is very powerful, and doubtless the amount of carbo- 248 ABSORPTION OF THE FOOD. hydrates remaining in any other condition than that of dextrose or levuhxse is very small. But, even if carbohydrates should be absorbed in any form but these, they would be inverted while passing through the cells. It is a remarkable fact that lactose, which forms so important a part of the milk, the sole food of the growing child, is unaffected by the enzymes ; however, in its pass- age through the epithelial cells it is inverted, the product being probably dextrose and galactose. Maltose, also, may be inverted by the columnar epithelium. It is, then, mostly in the form of dextrose and levulose that the carbohydrates of the food enter the blood and are carried to the liver, and from these glycogen is formed. Saccharose and maltose cannot be thus changed by the liver-cells. It sometimes happens that very large quantities of sugar are taken in with the food ; if the amount is so great that the liver and muscles cannot convert it all into glycogen, the overplus is eliminated by the kidney, and appears in the urine, constituting alimentary glycosuria. Glycogenic Function of the I/iver. — As we have seen, the result of the digestion of starch is its conversion into mal- tose, or maltose and dextrin, which later becomes dextrose, in which form, for the most part, the carbohydrates of the food reach the liver. Some levulose may accompany it to the liver, where, according to some authorities, it becomes dextrose. If during the time of the al)Sorption of sugar the blood going to the liver through the portal vein and that coming from it by the hepatic vein are analyzed, it will be found that the former contains much more sugar than the latter ; from this fact the inference is inevitable that some change takes place in the sugar during its passage through the liver. This change consists in its conversion by the hepatic cells into glycogen, which is a process of dehydration, the reverse of what takes place when the starch or glycogen of the food is converted into sugar. Formation of Glycogen from "Carbohydrates. — The liver weighs between 1500 and 1900 grams, and as the amount of glycogen in this organ may reach 10 per cent, of its weight, 150 to 190 grams, it is manifest that the carbohydrates of a single meal, which would ordinarily amount to about 100 or 150 grams, could be stored as glycogen in the liver, provided that before the next meal this was all reconverted into liver-sugar, and as such passed out into the blood, leaving the liver free from glycogen ; but this does not occur, so that we may conclude that all the carbohydrates are not deposited in the liver. As has been stated (p. 62), the muscles contain glycogen, sometimes to the amount of 1 per cent., and this undoubtedly comes from the carbohydrates of the food. If, however, all the glycogen in the liver and the muscles is taken into account, together with the GLYCOGENIC THEORY. 24!) dextrose in tlie blood, about 0.12 per cent., there still renuiins an overplus unaccounted for, and this is i)elieved to enter into the ibrmatiou of jiroteids and other substances; indeed, it is not i>y any means certain but that some of the absorbed dextrose may exist in the blood as dextrose and never undergo conversion into olvcoo-en, but perform the same office as the dextrose which does result^ from liver or muscle glycogen — /. atic vein as due to a change brought about bv the action upon the glycogen of an enzyme formed in the liver after death. His analyses of the blood of the ascending vena cava, wdiich carries the blood coming from the liver, show no increase of sugar over the blood obtained from other portions of the circulation, provided that it is examined before post-mortem changes have set in. For this purpose he kills the animal by a; blow upon the head, and immediately withdraws the blood. According to this theory, during life the glycogen of the liver does not become converted into dextrose, but is a source of fat and of j)roteid. That fat is formed in the body in considerable amount on a carbohvdrate diet is a well-known fact, and one of the re- strictions placed upon obese individuals who are endeavoring to reduce their fat is to abstain from sugar as much as possible. The glvcogen of the muscles may also serve for the purpose of fat formation. That glycogen serves also as a source of energy there is no doubt. It mav seem to the student a strange fact that what appears so sim})le a matter to determine as this which is in dispute between the adherents of the two theories referred to cannot i)e definitely settled ; but it is to be borne in mind that the blood is a very complex fluid, and the methods for detecting with certainty the DIABETES. 251 amount of sugar in the blood are not sufficiently exact to uarrant a positive statement, for in this fluid there are other reducing substances than sugar. Then, too, it must be remembered that the entire blood of the body passes through the liver every two minutes, so that while the total amoinit of sugar passed out from that organ in twenty-four hours might be considerable, yet the ditlcrenee in amount found at any given moment in the blood of the hepatic vein, over and above that found in other parts of the circulation, would be so small as not to be within the possibility of determination. In view of the conflicting evidence we must, therefore, acknowledge that the question is still an open one, with the weight of evidence at the present time in favor of the theory of Bernard. Diabetes. — This is " an affection characterized by an immoder- ate and morbid flow of urine. '^ AMien there is no sugar in such urine the condition is called diabetes insijyidus; but when the urine contains an abnormal amount of sugar, diabetes mellitus, or simply diabetes. The term c/h/cosuria refers to the excessive amount of sugar in the urine, and this condition may exist, tem- porarily, in other affections than diabetes. The form in which the sugar exists is principally that of dextrose, though there is doubt- less some maltose also present. The source of this sugar may be from glycogen or from proteids. If from the former, it may be caused by excessive conversion of glycogen into dextrose (Ber- nard), or from a failure on the part of the liver to convert into glycogen as much of the absorbed sugar as occurs normally (Pavy). Whichever view is taken, the treatment consists, among other things, in depriving the patient of all foods which make sugar. In some cases, however, even after this is done, the glycosuria continues, and the only possible explanation is that the sugar is produced from jiroteids. Artificial Diabetes. — The condition of glycosuria may be arti- ficially produced : (1) Puncture-diabetes. — Puncture in the floor of the fourth ventricle of the brain, the region in which is situated the vaso- motor center, will cause glycosuria. This center is stimulated by the puncture, the arterioles of the liver are constricted, thus reducing the amount of arterial blood in that organ, which results in an increased activity of the liver-cells, thereby causing an excessive conversion of glycogen into sugar. This is one expla- nation which has been given to account for the phenomenon. Another is that the glycosuria is due to a direct action upon the secretory nerves of the liver. (2) Fhlorizin-diabetes. — Glycosuria may also be produced by the administration of a number of different substances ; among these are phosphoric and lactic acids, strychnin, arsenic, phosphorus, and especially phloridzin or phlorizin, a bitter substance, having 252 ABSORPTION OF THE FOOD. the chemical formula CjjHjjOk,, obtained from the bark of the root of the apple-, ])ear-, and chcrrv-tree. Phlorizin is a glucosid. A glucosid is a vegetable principle which, when treated with acids and some other substances, yields ghicose and another sub- stance which is characteristic of the particular plant from which the glucosid was obtained. There are many glucosids which have been isolated ; among these are, amygdalin, from bitter almonds ; digitalin, from digitalis ; esculin, from the horse-chestnut, etc. It was thought at one time that the glycosuria which follows the administration of phlorizin was due to the glucose which it con- tains, but it is now known that pldoretin, which is a crystalline substance formed by the action of an acid on phlorizin, and which contains no glucose, will have the same effect as the phlorizin itself. (3) A diabetic condition may also be produced by removing the pancreas. Of this form of glvcosuria we have already spoken (p. 233). Absorption of Proteids. — The theory that the digestion of proteids consists in their being changed into a more diffusi- ble form, and that in this condition they are absorbed by the physical process of osmosis, has been to a considerable degree abandoned. For while it is true that proteoses and peptones are diffusible, while native albumins are not, still it has been shown that egg-albumin is absorbed as such, although it is non-diffusible. This absorption takes place in both the small and large intestine ; in the former, under circumstances Avhich demonstrate that it could not have been previously peptonized, and in the latter, of course, there is no peptonizing enzyme. We must, therefore, attribute the absorption of proteids to the epithe- lial cells, to whose efficiency in the process of absorption Ave have so frequently had occasion to refer. Not only is egg-albumin absorbed, but the same is true of syntonin as well. There is this difference, however, that when egg-albumin is absorbed in such quantity that it cannot be changed into an assimilable form while passing through the cells of the villi, it is carried by the blood to the kidneys, where it is eliminated, producing an " alimentary albuminuria," while syntonin is utilized by the tissues. There is little doubt that it is in the form of proteoses and peptones that the proteids are absorbed, and that the capillary blood-vessels of the villi are the efficient agents in this process. Some recent experimenters, Asher and Barbera, claim that some proteid is absorbed by the lacteals, but Mendel conducted an investigation as a result of which he concludes that " under ordinary circum- stances by far the greater share in the process must still be dele- gated to the capillaries of the villi." Although proteids are mainly absorbed as proteoses and pep- tones, yet during this act they lose their identity. In other words, ABSOEPTION OF FAT. 253 Avliile passing: throii<;h the q)itlicliul cells which cover the villi they are so changed that neither proteose nor peptone can be found in the blood, and if these substances are directly injected into the blood they are eliminated l)y the kidneys and arc found in the urine. Indeed, if the amount is sufficient they act as poisons, causino- insensil)ility, lowering blood-pressure, diminishing or destroving the coagulability of the blood, and producing death. Although the power to convert ])roteoses and peptones into a form which can be assimilated is claimed for the leukocytes present in the intestinal wall, the evidence seems conclusive that this claim is without substantial foundation, and that it is to the columnar epithelial cells covering the villi that the change is to be attrib- uted. Up to the present time the form of proteid into which these substances are changed has not been determined, though it is doubtless a coagulable proteid, and probably serum-albumin or globulin. Absorption of Vegetable and Animal Proteids. — The products of vegetable proteolysis are not so completely absorbed as are those of animal origin. It is stated by Moore that this is in part due to their envelopes of indigestible cellulose, in part to their shorter stay in the intestine because of their action in causing increased peristalsis, and in part to their less digestible character. He further states that the proteids of some legumin- ous plants and cereals are absorbed nearly as perfectly as those of animal origin, while in most others (potato, lentil) it is much less complete (22 to 48 per cent. less). The percentage of the nitrogen of meat or egg appearing again in the feces in man amounts to but 2.5 to 2.8 per cent. ; that of milk, to but 6 to 12 per cent. Absorption of Fat. — There is no dispute as to the lacteals being the channels through which the fat reaches the blood-vascular circulation by way of the thoracic duct ; the presence of fat in the vessels has been observed too often to admit of any doubt on this point. Indeed, it is the milky appearance given by the fat-particles to the contents of these vessels which has given to them the name of lacteals (Fig. 120), but as to the manner and form in which fat passes into the villus to reach the lacteals two theories are held : (1) the emulsion theory and (2) the solution theory, or, more correctly, solution theories. Emulsion Theory. — This theory is the older, and explains the absorj^tion of fat by supposing that the greater part of it is emul- sified by the action of the pancreatic juice, and, being thus broken up into a state of extremely minute subdivision, the particles pass into the villi, reach the lacteals, and by way of the thoracic duct enter the blood-vascular circulation. In this theory the sjilitting up of the fat plays the important part of aiding in the emulsifying process (p. 101). Although fiit-particles have often been oI)5erved in the interior of the epithelial cells, they have never been seen 254 ABSORPTIOy OF THE FOOD. in the striated borders of these cells, which is a remarkable fact if as fat they pass through these borders to reach the interior. Nor is there any special reason why fat should be taken up by the columnar epithelium more than any of the products of digestion. It has been supposed that the lymph-corpuscles, already described as existing between the epithelial cells of the villi, put out pseudo- podia and take in the fat-particles, passing them on through the reticular tissue of the villi (p. 217); but, as already stated, it is in the columnar epithelial cells that the fat is seen during the Fig. 140.— Longitudinal section through summit of vilhis from human small intestine; X 90Q (Flemming's solution): at a is the tissue of the villus axis; 6, epithelial cells; c, goblet-cell; d, cuticular zone (Bohm and Davidotf). time of its absorption, and these are entirely distinct from the lymph-corpuscles. Solution Theories. — Of these there are two.: (1) as soaps, (2) as fatty acids. Soap Theory. — This theory takes cognizance of the fact that soaps are formed in the small intestine by the action of steapsin on the neutral fats, by which they are split up into fatty acids and glycerin, the fatty acids uniting with some of the alkali of the intestinal fluids with the result of forming soluble alkaline ABSORPTION OF FAT. 25r> soa[)s. Tlio tlu'oi'v iimlcr coMsidcratioii siipjjoses that tlicsf soaps, ti)i2;('tli(>r with thr y \irtne oi" eell-aetion to form neutral fat, which is seen in the interior of the cells. We have alreadv referred to the fact tliat pancreatic juice has the power of decoinposint; all the fut of an ordinary meal into fatty acids and olycerin durini^ the time that it remains in the small intestine. The oi)jection to the soaj> theory, that there is not enough alkali in the body to com- bine with the fatty acids which would residt from th(! decomposi- tion of the fat which is taken in as food, is met by the exj)lanation that only a small amount is needed at a g-iven time to form a soap, and that as soon as the soap has entered the cells it is again decrom- posed into fatty acids and alkali, the latter returning to the blood and being again availabh; for use, while the acids unite with the glycerin to form neutral fat, Fattij Acid Theort/. — The other theory is that fatty acids, formed in the manner stated, are dissolved by the bile, and in this form are absorbed, the fatty acids uniting with the glycerin which was absorbed at the same time and f()rmino[' neutral fat. There is evidence showing that when fatty acids alone are absorbed, glycerin is formed, probably by the columnar epithelium, and that by the union of the two neutral fat is produced. The evidence seems conclusive that fats are absorlx'd as soaps and fatty acids, and not as emulsified fat, the fatty acids being dissolved by the bile, the salts and pseudomucin of which are the efficient factors in causing this solntion. In summing up this ])ortion of the section on the " Chemistry of the Digestive Processes," in Schafer's Text-Book of Physiology, Moore says: "It is probable, then, that in all animals a great part of the fat is absorbed and dissolved in the form of soaps; but in some animals a part is also absorbed as dissolved fatty acids, while in others the entire quantity leaves the intestine in the form of soaps." Course of Fat from Columnar Epithelium to the Lacteals. — Although fat is not absorbed as an emulsion, it is in this form that it exists in the interior of the epithelial cells after its re-formation from the fatty acids and glycerin. We have already referred to the large number of lymph-corpuscles, or leukocytes, in the tissues composing the villi. During the absorption of fat these cells contain fat, and they doubtless carry this to the lacteals, there either depositing it while still maintaining their integrity, or set^ ting it free by themselves breaking up and disintegrating. Some authorities hold the opinion that the contractions of the proto- plasm of the columnar epithelial cells forces out the fat, and that the ])articles pass through the spaces between the cells and thus reach the lacteals. 256 ABSORPTION OF THE FOOD. Final Disposition of the Absorbed Fat. — Inasmuch as no more than 60 per cent, of the fat al)sorbe(l tinds its way into the thoracic (kict, it mic^ht be inferred that the lacteals were not the only channels of absorption, and that the capillary l)lood-vessels of the villi had a part in this process, but there is no more fat found in the blood of the portal vein during the period of fat absorption than in the blood of the rest of the body, and even this is not increased if the contents of the thoracic duct are not permitted to enter the venous circulation. Just what becomes of the 40 per cent, imaccounted for is not known. It was long regarded as impossible for the absorbed fat to be deposited in the tissues unaltered, and it was supposed that it all underwent such changes as to destroy its integrity, and that the fat which existed in adipose tissue and elsewhere M'as entirely a new formation. In reference to this Liebig said : " In hay or the other fodder of oxen no beef- suet exists, and no hog's lard can be found in the potato-refuse given to swine." While it is true that some of the fat of the body is produced from other substances than the absorbed fat, still, the evidence is conclusive that under certain circumstances this is deposited in the tissues without undergoing any change whatsoever. If a dog is starved until the reserve supply of fat has been exhausted, and it is then fed with rape-seed or linseed oil or mutton tallow, fat will be again deposited in the tissues and in it some of the fat given as food will be recognizable. It is, however, a question whether this occurs except imder the exceptional conditions here mentioned, although some of the best authorities state that the fat in the blood after a meal is eventually stored up in the connective-tissue cells of adipose tissue. Others claim that the fat of the food is completely oxidized, and that the body-fat is formed from proteids or carbohydrates, or both. The probabilities are that proteids and carbohydrates are the principal sources of the body-fat, and that fat itself is sometimes a contributory factor, although its main office is to supply the body with heat or other form of energy. Absorption by the I/arge Intestine. — Although destitute of digestive power, this portion of the alimentary canaliplays an im- portant part in the process of absorption. The food undergoes diges- tion in the stomach and small intestine, staying in the former from one and a half to five hoTU's, and in the latter also a variable time. In one case, in which by reason of the existence of a fistula at the end of the small intestine it was possible to investigate this ques- tion, it was found that food began to enter the large intestine from two to five and a quarter hours after it had been eaten, and that the last portions did not reach the fistulous opening until from nine to twentv-three hours after its ingestion. It would appear that in this case the duration of gastric and intestinal digestion must have been verv brief — much briefer than in most individuals. QUANT f TV OF FPJCES. 257 That water is al)S()rl)(.'(l hv the walls .\[)fl the feces. If the stimulation is very pronounced, the abdondnid muscles mav also be called into action irrespective of the will, hut when the stimulus is slight they may only resj)<)nd Avhen callccl uj)()n by the brain. The connection between the brain and the anospinal center is very close, so that the action of the latter may for a time be inhibited; but if the rectum becomes very much distended, the impulses may be so strong that, despite the will, defecation will take place. Fig. 141.— Microscopic constituents of the stools: a, vegetable fragments; b, muscular fibers; c, white blood-corpuscles; d, saccharomyces ; e, micro-organisms ; /, crystals of triple phosphate; g, fatty-acid crystals (partly from Jaksch). Fig. 142.— Monads from the feces : a, Trichomonas intestinalis ; 6, Cercomonas in- testinalis ; c, Ameba coli ; d, Paramcecium coli ; e, living monads ; /, dead monads (Jaksch). Involuntary Discharges. — In some form? of disease the irrita- bility of the anospinal center is so great that Avhen the rectum is only partially filled defecation takes place, and there is no power to retard it. Discharges under these circumstances are said to be involuntary. Involuntary and Unconscious Discharges. — If l)y reason of disease or of injury the middle or the upper portions of the cord become so di.sorsrauized as to cut off communication with the 260 THE BLOOD. brain, while at the same time the lower portion is in normal con- dition, the act of defecation takes place when the rectum becomes sufficiently distended to stimulate tlie anospinal center to action ; but there is no power to retard nor is there any consciousness of it, since the connection with the brain is severed. Under these circumstances the discharges are involuntary and unconscious. If the lumbar portion of the cord is the seat of injury or of disease to such an extent as to destroy this center, the sphincter is permanently relaxed, and the feces are discharged as fast as they reach the anus. THE BLOOD. The office of the blood is twofold : 1. It carries to the tissues of the body the materials which they need for their nourishment, and, in the case of glands, for their secretion ; and 2. It takes from the tissues the materials which result from their destructive metabolism — waste materials — which it carries to those organs whose function it is to eliminate them, as, for instance, urea to the kidneys. The blood may be likened to a river which bears to the inhabitants along its banks their daily food, and into which at the same time their waste is discharged and carried to the sea. Physical Properties of Blood. — Blood is in general red in color and alkaline in reaction when tested with litmus-paper, and has in man a specific gravity of about ]060, although this varies in men, women, and cliildren, being less in the last, except at birth, when it is 1066. The specific gravity of the corpuscles is greater tlian that of the plasma. Method of Obtaining the Specific Gravity of Blood. — The most convenient method is that of Roy. In applying it, mixtures of glycerin and water are made of diffident specific gravities, and blood is dropped into these until one is found in which the drop of blood will neither rise nor sink. Knowing the specific gravity of this mixture, that of the blood, being the same, is also known. Color of Blood. — Although blood is generally said to be red, still this color is subject to considerable variation. Thus, venous blood is variously described as bluish red, reddish black, deep purple, dark purplish red, dark blue, and dark purple, while arterial blood is a bright scarlet. The color of blood depends on hemoglobin or its derivatives. In the blood of an animal that has been suffocated, where the purplish or blackish color is most ])ronounced, the coloring-matter is almost entirely hemoglobin, while in arterial blood the oxyhemoglobin predominates, and in ordinary venous blood there is a mixture of hemoglo! )in and o\} - hemoglobin. When the coloring-matter passes out from the corpuscles into the fluid portion of the blood the blood is said to be lakey. This solution of the hemoglobin may be brought about in many ways, PHYSICAL PROPERTIES OF BLOOD. JOl as l)v mUliiig tli.stilkd water ur a solution of jjodiiun clilorid or other neutral salt, provided that tiie solution is not imtonic. An isotonic solution is one in which the amount of the salt present does not ehansre the form of the red corpuscles or dissolve out its colorinir-mattcr. In the case of sodium chlorid, this is for human bldod a solution liavint^ a percentage of 0.9. Reaction of Blood. — The alkalinity of blood is a property essen- tial to life, and, S(j far as the plasma is concerned, depends u])on the })resence of sodium carbonate and phospliate. The alkalinitv is not always the same ; it is least in the morning, increases in the afternoon, and diminishes at night. It increases during digestion and after muscular exercise. It is said that the blood becomes acid immediately before death in cases of cholera, and also in the condition of unconsciousness called coma, which occurs sometimes in diabetes. Odor of Blood. — Blood lias an odor which is said to be charac- teristic of the species of animal from which it is taken. The odor is usually very slight, but it may be intensitied by the addition of sulphuric acid. Taste of Blood. — The sodium chlorid which blood contains gives to it a salty taste. Quantity of Blood. — The amoinit of blood in the body of a hmnan adult is about 7.7 per cent., one-thirteenth of his Aveight ; some authorities state one-eighth, and others one-fourteenth. In a newborn child it is about one-nineteenth. During the latter half of the period of pregnancy it is increased, and it is also in- creased during digestion. There are various methods of determining the quantity of blood in the i)ody ; that of AVelcker is, jierhaps, the best known. It consists in opening a vein of an animal and withdrawing blood, which is measured and defibrinated. This is then divided into portions, each of which is diluted with a different amount of water, which thus gives solutions of different colors ; these serve subsequently as standards of comparison. The animal is then bled until all the blood that will How has been withdrawn ; this is defibrinated, and sufficient salt solution is injected into the vessels to wash out the blood that remains. This is continued until the fluid comes out colorless. The body is then cut up into small pieces and mixed with saline solution, and this then filtered, and the filtrate, together with tiie washings of the blood-vessels, is added to the defibrinated blood. The mixture is measured, and diluted with water until its color corresponds with that of one of the standard solutions, when the calculation can be made which will determine the total amount of blood in the body. It is necessary, of course, to include the quantity of blood which was first witiidrawn to make the standard solutions. Temperature of Blood. — The temperature of the blood varies 262 THE BLOOD. greatly in the different parts of the circulatory apparatus. The mean temperature may he stated as 39° C; that of the superior vena cava, 36.78° C- the right side of the heart, 38.8° C; the left side of the heart, 38.6° C; the aorta, 38.7° C; the portal vein, 39.9° C; the hepatic vein, 41.3° C. The temperature of the blood in the hepatic vein is the highest in the body, and it varies from 39.5° C. at the beginning of digestion to 41.3° C. at the time when the process is most active. The blood in the right side of the heart is made warmer by its proximity to the liver, while in its circulation through the lungs it loses heat, and is there- fore cooler in the left side of the heart. In the portions of the body exposed to the air, as in the skin, the temperature of the blood mav Ije doubtless as low as 36.5° C. Distribution of Blood. — The (li.-tributiun uf l)luod in the body is as follows : In the heart, lungs, and great blood- vessels, one-fourth; in the skeletal muscles, one-fourth ; in the liver, one-fourth ; in the rest of the body, one- foiirtli. Microscopic Structure of the Blood. — When ex- amined by the microscope the blood is seen to be composed of corpuscles suspended in a fluid, the plasma or liquor sanf/>iiiiis. Blood-corpuscles . — By means of a hematocrit (Fig. 143) the average percentage of corpuscles in hitman blood has been found to be about 48 for males, and 43.3 for females, while for children of from six to thirteen years it is 45. In mak- ing this determination the blood is mixed with a measured quan- titv of a 2i per cent, solution of potassium bichromate, and then placed in "a tube which is revolved very rapidly, or, as it is expressed, centrifugalized . The corpuscles accumulate at the bot- tom of the tube, while the plasma remains above them, and the volume can be determined by simply reading the scale. The corpuscles of the l)lood are of three varieties : (1) Red corpuscles ; (2) colorless corpuscles ; and (3) plaques. Red corpjuscles in human blood are circular, biconcave, non- FiG. 143.— Hematocrit. MICROSCOPIC STRUCTURE OF THE BLOOD. 2G3 nucleated disks, haviii<; an avcrai^o diameter of 7.7 //, some of them ht'iiiir as small as 4.5 [i, while others are 9 [i. The small corpuscle's arc termed ii\icvocytcs,-M\{\ are re<;arded as not fullv de- veloped corpuscles. Ju chronic anemic conditions some have been founil as large as 14 u, aud others as small as 2.2 a. Number of lied ('orpuschx. — The number of red corpuscles in a cubic millimeter of the blood of a male adult has l)een reckoued at 5,()(lO,()(K) ; in that of a female, 4,50(),00(). In a man weighing 68 kilos there are estimated to be 25,000,000,000,000, present- ing a superficial area of about 3200 square meters. In all the blood of the body in health their number is consequently enormous. There are various methods of determining the number of red corpuscles: (1) By the hematocrit (p. 262); (2) by the hemacy- tometer. By the Hematocrit. — This instrument has been descril)ed, and its use explained, for determining the relative proportion of cor- puscles and plasma. It has been ascertained that each volume of corpuscles, as indicated by the scale, represents 97,000 corpuscles. Fig. 144. — Blood-corpuscles: a, blood-plaques or third corpuscles; b, red corpuscles; c, white corpuscles (Eberth aud Schimmelbusch). By the Hemacytometer. — There are three forms of this instru- ment — that of Gowers, that of Thoma-Zeiss, and that of Oliver. Gorcers' hemacytometer consists of a pipet, which contains 995 cu.mm. when filled to the mark made on the tube, a glass mouth])iece is connected with this pipet by means of rubber tubing; a capillary tube, holding 5 cu.mm. when filled to the mark, this also having a mouthpiece and rubber tubing ; a brass plate, with a glass slide, on which is a cell having a depth of i mm. and divided on the bottom into y^^ mm. squares, the cell in use being covered by a cover-glass ; a jar, in which the blood to be examined is diluted; a glass rod, for staining; and a needle, for pricking the finger to obtain blood. A solution of sodium sulphate is made having a specific gravity of 1025, which corresponds to the specific gravity of blood-plasma, and this is sucked up into the pipet to the mark indicating 995 cu.mm. This is then deposited in the jar. The finger is pricked with the needle, the amount of projection of which can be regulated by a screw, and 5 cu.mm. of blood sucked up into the capillary tulDC, and this is then deposited in the jar with the saline solution, aud the mixture thoroughly stirred with the glass rod. A drop of the mixture is then placed in the cell and a cover-glass 264 THE BLOOD. placed over it. The brass plate is placed on the microscope, with a magnifying power of 400 diameters. In a short time the red corpuscles settle to the bottom of the cell, and the number con- $ ■^^ o G C O' ^=^ — ^ o o :) -e- O o -^^ ^^^ 0^ o '^ c o -o- 3- D ^ O ^ ■^■ o o ^3% c o c> .a o ^) C ^ C c O "G <« -^3 T' O Fig. 145. — Thoma-Zeiss hemacytometer. 1. Mixing apparatus: a, capillary tuhe in which the blood is taken ; 6. chamber for mixing the blood -with the diluting solution ; c, glass ball to aid in mixing the blood with the diluting solu- tion. 2. Cross-section of the chamber in which the blood is counted. 3. Section of the field on which the blood is counted, showing thirty-six squares. tained in 10 squares are counted, added together, and multiplied by 10,000 ; the product is the number in 1 cu.mm. of blood. Thoma-Zeiss Hemacytometer (Fig. 145). — This is quite simple to use, inasmuch as the blood is drawn and diluted in one in- MICROSCOPIC STRUCTURE OF THE liLOOD. 2G5 struinent. It oon.sists of ii pipct with niuiitlipici-c tmd tiil)iiii^ connecting the two. It is carot'ully graduated, and has a l)iill) wliich contains 100 times as much as the (•a])inarv tulx- wiien filled to mark 1. In this hull) is a glass hull) which aids in the mixing of the blood and saline solution. There is also a glass slide (Fig. 14o, 2) having a covered disk. On the surface of this 1 cu.mni. is divided into 400 squares, each -^^ mm. This is surrounded by a cell of such height that when a cover-glass is placed upon it its under surface will be -^ mm. above the disk. The finger being pricked, the blood is drawn into the capillary tube as far as 1 on the scale ; the saline solution, Hayem's fluid (see below) or 3 per cent, sodium chlorid solution, is then drawn up to 101. The pipet is then shaken so as to mix the blood and solution thoroughly, and a drop of the mixture placed on m and covered Avith a cover- glass. The volume of blood above each of the squares will be -^-^^-^ cu.mm. The corpuscles in from 10 to 20 squares are counted, and by dividing this number by the nund)er of squares taken, the average per square will be obtained. This multiplied l)y 4000 X 100 equals the number of corpuscles in a cubic millimeter of blood. For the depth of the cell being -^^ mm., and the area of each square being j^^- sq.mm., the volume of blood on each scjuare would be 40-^oTr cu.mm. Inasmuch as the blood has been diluted 100 times, 1 cu.mm. of blood withdrawn from the vessels would contain 400,000 times the corpuscles in 1 square. Hayem's fluid consists of sulphate of sodium, 5 grams; sodium chlorid, 1 gram ; corrosive sublimate, 0.5 gram ; dissolved in 200 c.c. of distilled water. Oliver's Hemacytometer (Fig. 146). — This apparatus consists of a measuring pipet, a ; a dropper, 6; a mixing tube, c. A small amount of blood is measured in the measuring pipet and mixed in the mixing tube with Hayem's fluid. The tube is then held between the fingers, and the light of a wax candle, held about 2^ meters from the eye, in a dark room, is looked at, the tube being held edgeways. Enough fluid is added to make the flame appear as a bright line through the mixture. If the red corpuscles are present to the number of 5,000,000 to the cubic millimeter, the surface of the mixture will stand at 100. If the number is less, it will not require so much of the fluid to make the mixture trans- parent; while if the number is in excess of normal it will require more. The graduations on the tube are percentages of the normal standard; thus if 100 represents 5,000,000 corpuscles, 80 would represent 4,000,000. Many observations have shown that the number of red corpus- cles is subject to considerable variation even in the same individual. INIuscular exercise, and even massage, which is passive exercise, increase the number; while food diminishes it. The blood of persons living in high altitudes has shown the 266 THE BLOOD. presence of red corpuscles to the number of 8,000,000 per cu.mm. It does not necessarily follow, however, that this is an absolute increase, for it may be due to loss of the water of the blood, caused by increased evaporation from the body, and to increased Fig. 146.~01iver's hemacytometer: a, measuring pipet: h, dropper to contain Hayem's fluid; c, mixing tube graduated in percentages; d, mode of luaking the observation (this must be done in a dark room) ; a, h, and c are natural size. arterial tension, by which the amount of lymph is increased. In conditions of apparent health so small a number as 1,600,000 has been found. In newborn children, 5,000,000 per cu.mm. have been estimated. Color of the Red Corpuscles.— A. single corpuscle is of a MICROSCOPIC STRUCTURE OF THE BLOOD. 2G7 yellowish or ainWtT (^olor, and the red color of the blood appears only when the corpuscles are in thick layers or in masses. Strudnre of Red Corpascfcx. — There is a difference of opinion among histologists as to the minute structure of these bodies. Schiifer describes it as follows: "Each red corpuscle is fornusd of two parts, a colored and a colorless, the former being a solution of hemoglobin ; the latter, the so-called stroma, wliich is by far the smaller quantity, being composed of various substances, chief among these being lecithin and cholesterin, together with a small amount of cell-globulin." According to this view, the colorless stroma serves as an envelope to contain the hemoglobin in solution. By other authorities, of whom Rollett may be regarded as an exponent, the entire corpuscle is made up of an elastic structure, the stroma, the outer portion of which is denser than the inner, and having in its interstices the coloring-matter together with lecithin, cholesterin, and globulin. In discussing this subject, Gamgee, in Schafer's Text-Book of Physiology, says : '' Without attempting to speculate beyond the facts which we possess, it may, however, be assumed that hemo- globin exists in the blood-corpuscles in the form of a compound with a yet unknown constituent of the corpuscle. This compound, the existence of which we are forced to assume, is characterized by remarkable instability, for it is decomposed, setting free the hemo- globin, which then passes into solution (1) when the blood-plasma or serum, in which the corpuscles are suspended, is diluted; (2) when certain substances act upon the corpuscles (ether, chloro- form, salts of the bile-acids, certain products of putrefaction) ; (3) by the action of heat, by alternate freezing and thawing, by induction shocks, etc." The red corpuscles are exceedingly flexible, as may readily be seen by watching them in the circulation of the web of a frog's foot. At times they will be so stretched out as to pass through a vessel whose diameter is smaller than is theirs when in a circular shape ; or sometimes they may be seen bent over the projection made by the junction of two vessels, one portion being within each, until, one current being the stronger, they are carried for- ward by it, resuming their circular shape as soon as the size of the vessel permits. The human red corpuscles possess in adult life no nuclei. This is true of all mammals. Up to the fourth month of fetal life the blood of the human embryo contains nucleated red corpuscles. It is uncertain, however, whether these develop into the non-nucleated forms. In other vertebrates the corpuscles are nucleated. Chemical Composition of Red Corpuscles. — An analysis of the red corpuscles of human blood shows the presence of both organic and inorganic compounds. The percentage of organic ingredients in dried human corpuscles in one analysis was as follows : Proteids 2(j8 THE BLOOD. and nuclein, 12.24 ; hemoglobin, 86.79 ; lecithin, 0.72 ; cholesterin, 0.25. The nucleoproteid i.s called by some writers cell-globulin. The inorganic substances are potassium and sodium salts ; potas- sium constituting 40.89 percent, of the total ash, while of sodium there is only 9.71 per cent. HemogbMn. — This is the term applied to the highly complex, iron-containing, crystalline coloring-matter, which forms the most important constituent of the colored corpuscles of the blood, and by virtue of which they perform their function as the oxygen- carriers of the organism (Gamgee). It constitutes 95 per cent, of the solid matter of the red corpuscles, and in the adult male there are abgut 14 grams for each 100 grams of blood, or in all about 750 grams. When united with a molecule of oxygen it forms oxyhemoglobin ; wlien it exists by itself, ^\■ithout this molecule, it bears the name of hemoglobin or reduced hemoglobin. Because of its property of serving as an oxygen-carrier it is spoken of as a respiratory pigment. The hemoglobin in the blood of different animals varies both physically and chemically, so that some writers speak of tJie liemoglobins ; but Gamgee thinks this is unnecessary and misleading, inasmuch as the proportion in which iron, the characteristic element in the blood coloring-matter, occurs, is absolutely the same in many animals ; and, besides, there is abun- dant evidence in favor of the view that the optical and physiologic properties of hemoglobin depend upon the identical "typical nucleus" in all animals. When hemoglobin is decomposed in the presence of oxygen, it breaks up into a protcid, globulin, which constitutes 96 per cent, of it, and hematin, of which there is 4 per cent. If this decomposition takes place without oxygen, instead of hematin, hemochromogen is produced. It is to this latter substance that hemoglobin owes its characteristic property of taking up oxygen. The exact percentage-composition of the hemoglobin of human blood has not been determined ; that of the dog, as analvzed by Jaquet, is as follows : C, 53.91 ; H, 6.62 ; N, 15.98 ;. S^ 0.542; FeO, 0.333 ; O, 22.62. The molecular formula is C^5s^i2t>z^^g,- S33, FeOjig, making the molecular weight 16.669. Gamgee has calculated for the hemoglobin of the ox the following : Cy^gH^^ng- NoioSgFeOo,,^. Bunge says, in reference to the molecular weight of hemoglobin : " The enormous size of the hemoglobin-molecule finds a teleological explanation, if we consider that iron is eight times as heavy as water. A compound of iron which would float easily along with the blood-current through the vessels could only be secured by the iron being taken up by so large an organic molecule." HemoglolMii forms crystals in the absence of oxygen. Hemoglobinometers. — There have been various methods devised to determine the amount of hemoglol)in in the blood. Those which are commonly used are sufficiently exact for clinical purposes, MICROSCOPIC STRUCTURE <)F Till-: ULOOD. 269 thouoh muloubtedlv the (lctcnninati..n ..f the ain suj c 1^ g tinted glass riders in a graduated series from 1 to 9 1 ese r aers sented in the figure.) The apparatus is shown of the natural size. OUrcr's Hemoqlohinomder (Fig. 147).-Some of the blood the amount of whose hemoglobin is to be d^tf^mmed is d^^^^^^^^ and placed in the glass cell e; the color of this diluted blood is then compared with the series of tinte.l glasses, the color of each 27U THE BLOOD. of wliich corresponds to a known percentage of hemoglobin. The one that corresponds to the color of the sample of blood determines the percentage of hemoglobin in the blood under ex- amination. Goicers' Hemoglohiaoiaeter (Fig, 148).— This apparatus consists of two glass tubes having the same diameter, d contains glycerin- jelly colored with carmine, so that the color represents that of blood diluted one hundred times with water. The finger is pricked with the needle/, and the blood is sucked up into the pipet b to the 20 cu.mm, mark, and then blown out into the tube c, distilled water l)eing added in drops from a until the color of the diluted blood corresponds with the color in fl. Tlie tube c is so graduated that when tilled to 100 with diluted blood its color corresponds to Fig. 148. — Gowers' hemozlobinometer: a. pipet hottln for distilled water: 6, capillary pipet ; c, graduated tube ; d, tube with standard dilution ; /, lancet for pricking the finger. that of r/, wliich would consequently represent the color of normal blood. If, therefore, in order to produce a color corresponding to that in d, water must be added to fill the tube to a higher level than 100, the hemoglobin is above normal ; while if, on the other hand, the color is produced below 100, then the graduation at that point represents the percentage of the normal. Thus if at 75 the corresponding color is reached, only To per cent, of the normal amount is present. Von Flcificlir.s Hemometer (Fig. 149). — This consists of a stand carrying a white reflecting surface, e, and having a platform below upon which slides a glass wedge colored red, h. On the platform is a compartment, d, divided into tMo In* a vertical ])artition. The one which is directly above the colored wedge is filled with distilled water. Into the other, a small amount of distilled Avater is placed. MICROSCOPIC STRUCTURE OF THE BLOOD. 271 Tli(> tino-or is pricked and the blood which i.s to be examined is drawn np into a tube provided for that purpose. The Idood is tlien ]>ut into the second compartment, wliich is afterward filled with distilled water. The milled head /is then turned, and this carries alon<; with it the W('(l<;o of glass. When the colors, as seen by transmitted artilicial light, in the contents of both com- partments correspond, the percentage ol" hemoglobin in the bhjcjd Fig. 149. — Von Fleischl's hemometer : a, stand; h, narrow wedge-shaped piece of colored glass fitted into a frame (c), which passes under the chamber ; f/, hollow metal cylinder, divided into two compartments, which hold the blood and water; e, white plate from which the light is reflected througli the chamber : /, screw by which the frame containing the colored glass is moved ; .a, capillary tube to collect the blood; h, pipct for adding tlie water; », opening through which may be seen the scale indicating percentage of hemoglobin. may be ascertained by reading the scale at /. This instrument should be used in a dark room. Oxyhemoglobin. — It is this substance which gives to arterial blood the scarlet color which is so characteristic of it ; here, how- ever, it occurs, not by itself, but together with hemoglobin (re- duced hemoglobin) and in excess of the latter. In venous blood the two also coexist, but the hemoglobin is in excess, while in the l)loo(l of asphyxia the coloring-matter is almost entirely hemooflobin. 272 THE BLOOD. The hemoglobin of some animals, as the guinea-pig, cat, and dog, ervstallizes very readily, while that of man, and the mammals generally, forms crystals with more ditticulty. To obtain erystals of oxyhemoglobin, the blood should be mixed in a test-tube with one- sixteenth its volume of ether and the tube shaken with consid- erable force. The coloring-matter passes into the plasma, and the blood becomes lakey. If the tube is then placed on ice, in a short time the crystals will form and can be exaniined uniler the micro- scope. The form of the crvs- />/''f 'fS. t\ tals varies in ditferent animals (Fig. 150). In the guinea-pig, the blood of which is easily obtained, and wliose oxyhe- moglobin crystallizes readily, they are rhombic tetrahedra. Derivatives of Hemoglobin. — Besides oxyhemoglobin, the properties of which have al- ready l)een given, there are various derivatives of hemo- o-lobin ; among them are the following : Carhon-mon oxid Heinoglo- hin. — As one molecule of hemoglobin combined with one of oxygen forms oxyhem- oglobin, so one molecule of hemoglol)in united with one of carbon monoxid forms carbon-monoxid hemoglobin. There is, however, one strik- ing difference in the two com- binations. In the former the oxvgen is readily displaceable, while in the latter the com- ptnmd is a very stable one, although Ganigee has shown that bv the long-continued passage of neutral gases through solu- tions of CO-hemoglobin the CO is gradually driven out, and reduced hemoglobin is obtained. Carbon monoxid is the gas formed when combustion is incomplete, such as is produced by the charcoal fur- nace used in France for suicidal purposes ; the charcoal fumes when inhaled in sufficient quantity produce fatal results. It is also a con- stituent of illuminating-gas, where it exists in proportions ranging from 7.9 to 28.25 per "cent., and is not infrequently the cause of death. The gas displaces the oxygen and unites so firmly with the hemo^rlobin that even with artificial respiration it cannot be dis- FiG. 150. — Crystallized hemdgloliiii : a, h, crystals from venous blood ofiiiau; c. from the blood of a cat : d, from the blood of a guinea-pig ; e, from the blood of a hamster; /, from the blood of a squirrel i after Frey). MICIiOSCUriC STRUCTURE OF THE BLOOD. 273 phu'ctl. Tlio color ol" carljoii-iiionoxid heinoglohin i^ a clierrv red, aiul the l)k)(Kl ill j)C'iX)iis poisoiud witli it lias this color. yitric-o.i'id lldncKjlobin. — ^nitric oxid will also displace the oxygen from oxyhemoglobin, and the nitric-oxid hemof/loLin which results is a more stable compound than carbon-monoxid hemo- gloi)in. It consists of one molecule of hemoglobin and one of nitric oxid. Carb()-hei)i()lood-clots, sucli as form in apoplexy, where a blood-vessel of the brain ruptures, a crystalline substance is found, to which Virchow gave the name lieinatoidin. It is beyond question a deriv- ative of hemoglobin. Its formula is given as C-jgH^XoOg, and it is identical with bilirubin. Histohematins. — In the muscles and otlu^r tissues of the body coloring-matters are found which are called hktohemathis, which may be related to hemoglobin^ but the relationship has not as yet been established. Spectra of Hemoglohhi and its Derivatives. — Before discussing, the spectra of hemoglobin and its derivatives, it will not be inap- propriate to describe the spectroscope and its application to the differentiation of the coloring-matters of the blood in the varied forms in which we have found them to occur. For a more de- tailed description of spectrum analysis our readers are referred to the many excellent treatises on physics. The wonderful adapta- bility of spectrum analysis to the solution of many physiologic problems may be illustrated by the statement that by its means 3T 0O00O ^^ ^ milligram of sodium can be detected, and a corre- sponding delicacy of analysis is true of other substances ; thus the rapid absorption and diffusion of certain substances have been de- termined by the spectroscope. Roscoe, in his Spectrum Analysis, states that twenty-four minutes after injecting 3 grains of lithium salt under the skin of a guinea-pig the lithium is found to be present in the crystalline lens and every part of the body, it only 1. Solar spectrum with Fraunhofer lines. 2. Absorption spectrum of a concentrated solution of oxyhemo- globiu ; all the light is absorbed except in the red and orange. 3. Absorption spectrum of a less concentrated solution of oxyhemoglobin. 4. Absorption spectrum of a dilute solutiou of oxyhemoglobin, showing tlie two characteristic bands. 5. Absorption spectrum of a very dilute solution of oxyhemoglobin, showing only the a-band. 6. Absorption spectrum of a dilute solution of reduced hemoglobin, showing the characteristic single band (to be compared with spectrum 4). 7. Absorption spectrum of a dilute solution of carbon-monoxid- hemoglobin (to be compared with spectrum 4). 8. Absorption spectrum of methemoglobin. 9. Absorption spectrum of acid hematin (alcoholic solution). 10. Absorption spectrum of alkaline hemaiin (alcoholic solu- tion) (modified from MacMunn, The Spectroscope in Medicine). MICROSCOPIC STRUCTURE OF TJII-J IlIJJOl). 'Zii) being necessary to burn a portion ol' tiic animal tissue in a colorless Hanu' in order to sec the bright-red lini; of litliiuin : ten minutes after the injection it is found in small quantities in the lens, but plentifully elsewhere ; while four minutes after the injection lithium is not found in the lens, but plentifully in the a(iueous humor of the eye, ami in the bile. The same raj»id dilfusion occurs in the human body. The crystalline lenses of per- sons who have been operated upon for cataract have been examined, these persons having previously to the removal of the lens been given by the stomach 20 grains of carbonate of lithium ; in three and a half hours it was detected in each particle of the lens. When a sunbeam passes through a glass prism, the differently Fig. 1.=52. — Spectroscope : p, the glass prism ; a, the collimaror tube, showing the slit is) through which the light is admitted ; b, the telescope for observing the spectrum. colored rays which compose it are separated, and if, after emerging from the prism, the beam falls upon a screen, it will appear as a band of different colors, beginning with red and ending Avith violet; this band is the solar specfrum (Plate 1, Fig. 1). A spectroscope is an instrument for producing and observing spectra (Fig. 152). The beam of light which is to be studied, from what- ever source it may come, passes into the coflimafor iuhe A, through the slit s, and its rays, being made parallel by a lens in this tube, are separated or dispersed by the prism p ; the spectrum which results may then be examined by an observer through the telescope p.. If the source of the light is an incandescent body, the spec- trum will be a continnovs one — /. e., there will be nothing but a band of colors, in which the red passes on to violet through 276 THE BLOOD. orange, yellow, green, blue, and indigo ; but if it is the sun which is the source of light, though this is an incandescent body, still its light passes through an atmosphere which absorbs certain jiortions of the light, and the spectrum is, therefore, crossed by dark lines, Fraunhofer lines. These lines are fixed, and the more distinct ones are designated by letters of the al[)habet; thus in tlie red are A, B, and C; in the yellow D, etc. As the atmosphere of the sun absorbs certain parts of the light which is transmitted through it, so do many transparent substances, and the spectra of such substances are known as absorbent spectra, in contradistinction to continuous spectra, in which no lines or bands appear. If, there- fore, the light of tiie sun or that from auv other source of illumi- FiG. 153. — The hematinometer. Fig. 154. — The hematoscope. nation is passed through a solution of one of these substances, in its spectrum dark bands will be seen at definite places and in definite numbers, and the identity of such substances can thus be determined. The positions occupied by these bands may be designated either by stating their relation to the Fraunhofer lines, or the wave-length of the portions of the spectrum between which absorption takes place, this being determined by a scale which is provided for this purpose. For the description of the spectra of hemoglobin and its derivatives, and the use of the spectroscope in their differentiation, we are especially indebted to the section on "Hemoglobin," by Gamgee, in Schafer's Physiology. MICROSCOPIC STRUCTURE OF THE BlJjon. 277 For stiulyiii<^ the visihlc spci-tniiu of heiiioolobiii, (jiaiugco recominoiuls a spectroscope of the ordinary Bunsen type, provided Nvith a .sinjrle good Hint-glass j)risni, or direct vision sjx-ctroscopes of the Browning or Hofinann patterns. If minute (juantities of coloring-matter are to be investigated, micr<)speetroseo[)es may be used — /. ('., direct vision spectroscopes adapted to the eye-piece of a compoiuid microscope. As the source of liglit, lie recommends a gas lamp, furnished with the Auer incandescent burner. It is convenient to have the solutions, whose absori)tion-spectra are to be examined, in cells with ])erfectly parallel sides, and a defi- nite width apart ; such an apparatus is ihehcmatinometer (Fig. 153). The hcinafoscope or Jieiiwscope of Hermann (Fig. 154) is also used for this purpose. In this apparatus the thickness of a layer of fiuid can be regulated by sliding c toward F, and measured by a scale on c. F and c are glass plates through which and the intervening fluid light is transmitted for spectroscopic examina- tion. Spectrum of Oxyhemoglobin (Fig. 155). — Dilute solutions of 70 65 50 4-5 BCD E b F G Fig. 155. — Diagrammatic representation of the absorption-spectrum of oxyhemo- globin. The numerals give the wave-lengths in hundred-thousandths of a milli- meter; the letters show tlie positions of the more prominent Fraunhofer lines of the solar spectrum. The red end of the spectrum is to the left. The a-band is to the right of D, the /3-band to the left of K (after Eollett). oxyhemoglobin give two absorption-bands between D and E. The band nearer D — /. e., the red end of the spectrum — is known as the " «-band "; the one near E is the " y5-band," and is broader, lighter, and less clearly defined than the a-band. The center of the a-band corresponds to a wave-length of 579 millionths of a milli- meter (X 579) ; while the center of the /9-band corresponds to X 553.8. _ ■ Spectrum of Hemoglobin (Reduced Hemoglobin) (Fig. 156).— Oxyhemoglol)in may be reduced to hemoglobin by adding to its solutions Stokes' reagent, which is made by dissolving 2 parts by weight of ferrous sulphate, adding 3 parts of tartaric acid, and then adding ammonia until the reaction is distinctly alkaline. AYhen thus reduced the «- and ;5-bands disappear, and the " }'-band " appears ; this is a single band between D and E, its darkest part being nearer D than E, and corresponding to about X 550. If the solution is shaken with air, the appearance of the a- and ^-bands shows that oxyhemoglobin has been formed. 278 THE BLOOD. Carbon-monoxid Hemoglobin. — This derivative of hemoglobin presents two bands resembling those of oxyhemoglobin, except that they are nearer the violet end of the spectrum. Methemoglobin and hcmatin have each a characteristic spec- trum. Development of Red Corpuscles. — This is described by Schiifer as taking place in the following manner : In the developing embryo some cells of the mesoblast become united, forming a protoplasinic network. These cells are nucleated, and their nuclei multiply, colored protoplasm forming an aggregation around them. The protoplasm of this network is hollowed out by an accumulation of fluid ; in this manner the capillary blood-vessels are formed. The nuclei with their colored protoplasm are set free, becoming embryonic blood-corpuscles. The blood-corpuscles are at this period, therefore, nucleated cells. The corpuscles at this time have a diameter of from \0 fi to 16 n, and are spherical. They possess the power of ameboid movement, and thus resemble 70 65 45 I BCD E b F (j Fig. 15(j. — Diagrammatic representation of the absorption-spectrum of hemo- globin (reduced hemoglobin). The numerals give the wave-lengths in hundred- thousandths of a millimeter ; the letters show the positions of the more prominent Fraunhofer lines of the solar spectrum. The red end of the spectrum is to the left. The single diffuse absorption-band lies between D and e (after Eollett). the white corpuscles. It has been suggested that these should be called blood-cells rather than blood-corpuscles. The liver begins to be formed about the third week of em- bryonic life, and about the third month occupies most of the abdominal cavity. This organ, together with the spleen, thymus, and lymphatic glands, also produces blood-cells which are nucle- ated, are at first colorless, and afterward acquire the characteristic color. At a later period of embryonic life, about the second month, non-nucleated disk-shaped corpuscles make their appearance. These originate to some extent in connective-tissue cells, a portion of the cell becoming colored, and separate into globular particles, which subsequently become the discoid corpuscles. The connec- tive-tissue cells afterward become hollowed out, and, joining with other cells which have gone through the same process, blood- vessels are formed. This later embryonic formation of blood- corpuscles does not involve the cell-nuclei, as does that of the earlier period. The nucleated cells are replaced by the non- MICROSCOPIC STRUCTURE OF THE BLOOD. 279 nucleated about tlie cud of tlie fourtli uiontli, hut it is still a moot (juestiou wlietlier auy of the nucleated cells are actually concerned in the lorniation of the non-nucleated. Non-nucleated blood-corpuscles are also formed in the medulla or marrow of bones, and in the spleen. In the red marrow of bones are found nucleated cells possessing the power of ameboid movement, the true " marrow-cells " of K(')llillace its life at from three to four weeks. Old corpus- cles constantly undergo disintegration and new ones appear. The fact that fewer corpuscles are found in the blood of the hepatic than in that of the portal vein, and the additional fact that biliary pigment is formed from the coloring-matter of the blood, indicate that in the liver a part, at least, of these destructive changes takes place. The spleen is also regarded by some authorities as being an organ in which red corpuscles are destroyed. The argument advanced in favor of this theory is that some of the susten- tacular or supporting cells of the splenic pulp contain colored granules which resemble the hematin of the blood ; in others red corpuscles are found in various stages of disintegration. The explanation is that these large cells are engaged in the process of destroying used-up corpuscles. Opposed to this theory is the fact that the blood coming from the spleen contains no hemoglobin in solution, which it certainly would do if red corpuscles were destroyed in that organ ; besides, after removal of the sj)leen the destruction of corpuscles apparently goes on much the same as before. There seems to have been an idea in the minds of some that it Avas essential that some organ or organs should be charged with the duty of destroying the red corpuscles. This does not, how- 280 THE BLOOD. ever, follow. There is no reason why many of the coqjuscles mav not undergo disintetrration in any part of the circulatory svs'tem, wherever they happen to be at the time the change takes place. The large extent of blood-vessels in the liver would account for the destruction that takes place there, without regard to anv special function of this organ connected with such destruc- tion. If, as there is reason to believe, the pigment of the bile and the urine are formed from that of the blood, the number of corpus- cles daily destroyed must be very great. Function of Red Corpuscles. — The red corpuscles are the carriers of oxygen from the lungs, where it is received, to tiie tissues, which appropriate it. This function is due to the hemo- globin, which has a great affinity for oxygen. Diapedesis. — In inflammatory conditions the red corpuscles pass through the walls of the capillaries, constituting diapedesis (p. 282). This is not an active process, as in the case of the leukocytes, but a passive one ; for while the latter can make their way through uninjured walls, it is only after these have thus migrated that through the same opening the red corpuscles can pass. Colorless Blood-corpuscles. — These ai'e also called vliite cor- puscles and leukocytes. They consist of granular protoplasm, and contain one nucleus or more. When in a condition of rest they are spheroidal in shape, with a diameter of about 10 a, and possess the power of amel)oid movement ; their shape is constantly changing. The number of leukocytes in the blood is commonly said to be, (!ompared with the red corpuscles, as 1 to 350 or 1 to 750, or, as others state it, about 10,000 in a cubic millimeter of blood ; but these figures are of very little value, so greatly do the ])ropor- tions vary under different condititjns. Thus Hirst found before breakfast, 1 to 1800 ; one hour after, 1 to 700; before dinner, 1 to 1500; after dinner (1 o'clock), 1 to 400 ; two hours later, 1 to 1475; after supper (8 o'clock), 1 to 550; 12 P. M., 1 to 1200. After eating the number is much increased. This increase also occurs after the loss of blood, during suppurative processes, and after the use of bitter tonics ; while in a state of hunger or defi- cient nourishment the number is diminished. The proportion also varies in different parts of the circulatory system ; thus in the splenic vein it has been found to be as 1 to 60 ; in the splenic arterv, 1 to 2260; hepatic vein, 1 to 170; and portal vein, 1 to 740. Leukocytosis is defined as a temporary increase in tlie number of leukocytes in the blood. It occurs normally during digestion and in pregnancy, and is seen as a pathologic condition in inflam- mation, traumatic anemia, various fevers, etc. Leukocythemin or leukemia, on the other hand, is a fatal disease with marked MICROSCOPIC STRUCTURE OF THE BLOOD. 2X1 inorease in the miiuher t)f leukocytes in tlic Ijlood, to<^c'tliL'r w itli enlar»i;eniont and proliferation of" the lymplioicl tissue of the spleen, lymphatic glands, and bone-marrow. The disease is distinguished as li/mjjhatic, splenic, lymphaticospleiiic, medullary or )iii/clo(/<)ii<', and lioiomi/clor/oious, according as the disease involves the lymphatics, the spleen, both the spleen and the Ivmphatics, the bone-marrow, or both the spleen and bone-marrow. It may be due to disorder of the intestines {i)ifcstinal leukemia), of the liver {hepatic leukemia), or to disease of the tonsils {amygdaline leukemia) — Borland's Medical Dictionary. If peptones or leech extract are injected into the blood-vessels, there is at first a diminution in the number of the leukocytes, especially the polynuclear variety ; this is termed the Inikocyto- penic phase ; afterward the number is increased, constituting the leukocytotic phafic. Acute local inflammation causes similar changes as do these injections, but the diminution in the number of leukocytes in this case largely affects the coarsely granular variety, -while the after- increase is found mainly in the finely granular corpuscles (Schafer). It has been observed that the blood clots more readily Avhen the coarsely granular cells are relatively few in number, and Schafer thinks this may explain the more ready clotting of blood in in- flammatory conditions. Varieties of Colorless Corpuscles. — Ehrlich classifies the color- less cells according to the kind of anilin stain Avhich the majority of the contained granules take ; thus cells Avhose granules are stained by basic dyes, as methylene-blue, he terms basophil ; Avhile those whose granules are stained by acid dyes, such as eosin, he calls o.ryphil or eo.si)iophil. These terms are also written basophile, oxyphile, and eosinophile. Still another classification divides the colorless corpuscles into (1) lymphocytes, which are characterized by being small, having a round vesicular nucleus, and named from their resemblance to the leukocytes of lymph-glands, but not possessing ameboid movement; (2) mononuclear leukocytes, ce\h with a single nucleus; and (3) polymorphous or polynucleated leukocytes, characterized by having more than one nucleus or else a divided nucleus, the divisions being connected by protoplasm. Nos. 2 and 3 possess ameboid movement. It is believed by some authorities (Howell) that these varieties are simply different stages in the development of a single type of cell, the lymphocytes being the youngest and the polynu- cleated leukocytes the oldest. The granules of the mononuclear variety are coarser and stain more deeply with eosin than do those of the polynuclear, but constitute only about 5 per cent, of the total colorless corpuscles ; while the basophil cells are not often found. Still another variety, called hyalin, is described ; these have no crranules. It should be borne in mind that it is the kind 282 THE BLOOD. of dye which the protoplasm takes which determines the variety of the corpuscles ; the nuclei of all the leukocytes is basophil. Composition of Leukocytes. — The chemical composition of leukocytes is given (Lilienfeld) as follows : Water 88.51 Solids 11-49 The solids are : Proteid 1.76 Nuclein 68.78 Histon (i. e., proteid part of the nucleoproteid) 8.67 100.00 Lecithin 7 51 Fat 4.02 Cholesteriii 4.40 Glycogen 0.80 This analysis of the cells is of those from the thymus, but we are justified in concluding that the colorless corpuscles of the blood which originate from lymphoid structures have a similar composition. It is, however, impossible to investigate the color- less blood-corpuscles by macrochemical methods. Micro-chem- ically they can be shown to contain fat and glycogen (Halli- burton). Fmidions of the Colorless Corpuscles. — The movements which occur in protoplasm, known as ameboid movements, have been already described (p. 24). This power is possessed by the leuko- cytes, by virtue of which they pass through the walls of the capil- lary blood-vessels, this power being diapedesis or migration. Thens is no doubt that this occurs normally to a certain extent, but to a much greater extent under abnormal conditions, as in in- flammations. When the.se migrated leukocytes accumulate out- side the blood-vessels, and have lost their vitality, they consti- tute pus. Phagocytosis. — Metschnikoff has advanced the theory that one of the important functions of the leukocytes is to ingest and digest bacteria ; this constitutes jihagoci/tosis. In this process the polynucleated cells are the most active. There is no doubt that by virtue of their ameboid movement the leukocytes do surround and take into their protoplasm foreign matter, and if bacteria are present they are likewise ingested, but whether they are thus taken in while in a living state and destroyed, or only after their vitality has left them, is a question. Those who favor the theory look upon the leukocytes as the protectors of the human race against the incursions of infectious diseases, if their vitality is sufficient to overcome and destroy the l^acteria of these diseases ; whereas if the bacteria are the more powerful, then the disease obtains a foothold. A person is said to be immune when on ex- posure to a communicable disease, such as scarlet fever, measles, etc., he does not contract it, and the explanations which have been MICROSCOPIC STRUCTURE OF TIIK BLOOD. 283 given to aet'ount ior this hiuinmifij are many and various. One of these is tlie " phagocytosis theory of Metschnikoff" : That " ininmnity against infection is essentially a matter between the invading bacteria on the one hand and the leukocytes of the tissues on the other; that during the first attack of the disease tiie white blood-corpuscles gain a tolerance to the poisons of the bacteria, and so are able to resist the next incursion of the enemy." I'his phagoeytotic power of the leukocytes is also manifested in their destruction of the products of inflammation. It is believed that the colorless corpuscles are concerned in the process of coagulation of the blood (p. 286.) For the consideration of other functions of the leukocytes, the reader is referred to pages 24 and 25. Development of Colorless Corpuscles. — The first leukocytes are formed from the embryonic cells of the mesoblast, and afterward from lymphatic glands and lymphatic tissues generally. They pass into the lymphatics and thence into the blood-vessels. Plmpies. — These are also known as blood-plates, blood-platelets, and he mat ob lasts. They are circular or elliptical in shape, and smaller than the red corpuscles, but vary very much in size, from 0.5 /I to 5.5 fx, and are colorless. Their number is said to vary from 180,000 to more than 600,000. Various theories have been propounded to explain their occur- rence in blood. One of these is that they are not formed struct- ures, but simply precipitates of nucleoproteid from the plasma. This theory is, we think, no longer held. There is little doubt that they are formed elements existing normally in the blood, although the theory of Hayem, who discovered them, that red corpuscles are formed from them, is no longer maintained. Lilienfeld has obtained from them a nucleo-albumin, called by him nucleohlston, which is also found in the nuclei of the leuko- cytes, and it is believed by many that the blood-plates are nothing more than the nuclei of the polynucleated colorless corpuscles, which are set free when these corpuscles disintegrate, and that these plates also disintegrate, and are dissolved in the plasma. Their possible relation to the coagulation of the blood is discussed in connection with that subject (p. 286). Blood-plasma. — The plasma or liquor sanguinis is yellowish in color and alkaline in reaction, having a specific gravity of 1027 to 1031. It contains the following ingredients: Water, inorganic salts, extractives, enzymes, proteids, and gases. Water and Inorganic Salts. — Water exists in plasma to the approximate amount of 90 per cent., so that 10 per cent, consists of solids. Of these solids, about 0.85 per cent, are inorganic salts; and of these, sodium chlorid is the most abundant, being present to the amount of 0.55 per cent. Sodium carbonate is present to the amount of 0.15 per cent.; and this salt is the 284 THE BLOOD. principal cause of the alkalinity of the plasma, and gives it its power to absorb carbon dioxid. The salts of the plasma have not been exactly determined, but, according to Schmidt, the following table gives those that probably occur, Avith their percentages : Potassium sulphate 0.0281 Potassium chlorid 0.0359 Sodium chlorid 0.5546 Sodium phosphate 0.0271 Sodium carbonate 0.1532 Calcium phosphate 0298 Magnesium phosphate 0.0218 Calcium chlorid is probably also present, and traces of a fluorid have likewise been found. Extractives. — These include carbohydrates, of Avhicli there are three : Glycogen, probably derived from the leukocytes ; an animal gum ; and dextrose. This last, we have seen, is always present in human blood to the amount of about 0.12 per cent., being much more abundant in portal blood during the digestion of carbohydrates. Fat is also a constituent of the plasma, the amount being increased by its absorption after a meal containing it. Lecithin, cholesterin, Upochrome (which gives the plasma its vellow color), urea, uric acid, Irreatin, Jcreatinin, and occasionally hippuric acid are also present. Enzymes. — Plasma contains four enzymes: (1) An amylolytic, which converts starch into dextrin, maltose, and dextrose ; (2) a gh/co/i/tic, which causes a destruction of some of the dextrose of the plasma fthe existence of this enzyme is doubted by excellent authorities ; others think it may come from the leukocytes) ; (3) a lipolytic, called lipase; and (4J thrombin or prothrombin, the en- zyme which brings about coagulation of blood by changing fibrinogen into fibrin (p. 285). Proteids. — These are : (1) Serum-albumins, a, ,9, and } (p. 108) ; (2) serum-globulin or paraglobulin (p. 110); (3) fibrinogen (p. 110 j ; (4) nucleoproteid. The total proteids in human plasma are 7.62 per cent., of which 3.10 per cent, are globulins, and 4.52 per cent, albumins. ^ The proteids of the plasma have been already discussed iu dealing with this class of physiologic ingredients (p. 125), but one of them, fibrinogen, deserves special notice at this time because of its relation to the process of blood-coagulation. Fibrinogen. — Although it is cu.-tomary to speak of fibrinogen as if it was a simple substance, yet the fact that when it is di.s- solved in salt .solution and heated to a temperature between 52° C. and 55° C. only a part of the proteid is coagulated, and that when the temperature reaches 65° C. another portion is thrown down, has led Hammarsten to regard it as made up of fbrinogen proper, which coagulates at the lower temperature, and a globulin. MICROSCOPIC STRUCTURE OF THE BLOOD. 285 fibrin-(//()hufin, whicli is coagulated at the higher temperature. It is believed that a uucleoprotcid is also coml)ined with these two proteids to make up what is commonly termed Hbrinogen. Origin of Fibrinocjen. — Matthews, after a very elaborate study of the subject, reported in the American Journal of Physiolof/y, concludes that the decomposing leukocytes of the blood, and chieHv those of the intestinal area, are the sources of the blood tii)rinogen, and supports this opinion : "(1) By the increase in the per cent, of ril)rinogen in all cases of prolonged leukocytosis accompanving suppuration ; (2) by the increase in fibrinogen during leukocvthemia ; (3) by the increase in fibrinogen in pneu- monia, ervsipelas, acute rheumatism, peritonitis, and similar in- fiammatorv conditions; (4) by tiie fact that fibrinogen is not simplv transformed proteid of the food, as indicated by its con- tinued formation during fasting, and its failure to increase during proteid digestion ; (5) by the observation that neither the spleen, muscles, kidneys, pancreas, nor brain appears to be essential to its formation ; (6) by the well-known fact that there is present in the cell-l)0(ly of the leukocyte a substance which, by the action of a substance coming from the nucleus or arising in its neighbor- hood, is thrown into a fibrillar form closely resembling fil)rin- fibrils, and like them contractile ; (7) by the fact that the leuko- cytes are constantly going to pieces in the body, hence must be adding constantly to the proteid constituents of the blood ; (8) by the close correspondence existing between the fibrinogen-content of the blood and the excretion of uric acid ; and (9) by the fact that the intestine, which is rich in leukocytes, appears to be the chief source of the fibrinogen of the body." In this article Matthews makes the following statement, which is, to say the least, suggestive, although, of course, as yet not demonstrated : " If fibrinogen is derived from the leukocytes, as the preceding considerations indicate, and if Schmidt's and Mfirner's observations on paraglobulin indicating its origin in the leukocyte prove well founded, the conclusion would seem obvious that the proteids of the blood are derived from the leukocytes. This would strongly confirm HofFmeister's view^ that the leukocytes are pre-eminently active in proteid absorption and assimilation. It would lead to the interesting conclusion that the organism lives on its leukocytes much as the egg-cells of some forms live on their follicle-cells. If this were so, it would explain (1) the true function of the leukocytes and the elaborate arrangements for their production in the bodv ; (2) their congregation and great reproduction in the intestinal area during a proteid meal ; (3) the positive chemotaxis they exhibit toward the ])roteids, albumoses, and other products of digestion ; (4) the maintenance of the pro- teid constituents of the blood during fasting ; (5) the fate of the bodies of the leukocytes when they disintegrate ; (6) the fact that 286 THE BLOOD. no products of digested proteids are found in the blood during proteid digestion. It would make the leukocyte, in fact, a store- house of the surplus proteid food of the body, just as the liver- cell is a storehouse of surplus carbohydrate food." Niicleoproteid, — In regard to this constituent of plasma, Schiifer says that it is doubtful if it exists in the plasma of circulating blood, and that beyond the fact of its appearing to be one of the essential factors in the formation of fibrin, very little is known about it. It is regarded as being derived from the leukocytes and plaques at the time the blood is withdrawn from the vessels. A small amount comes from the red corpuscles. The reasons for this belief as given by Schiifer are : 1. White blood-corpuscles and similar cells (lymph-cells, thy- mus-cells, etc.) always contain a considerable amount of nucleo- proteid. 2. In plasma obtained by subsidence of the corpuscles there is most nucleoproteid in the lower layers, which contain most leuko- cytes ; and least in the upper, which contain very few. 3. Fluids which collect in the serous cavities of the body (pericardial fluid, hydrocele fluid, ascitic fluid) frequently contain no leukocytes. When this is the case they are also devoid of nucleoproteid and of the property of spontaneous coagulability, although they contain fibrinogen. Solutions of this nucleoproteid are coagulated at 65° C, and at 60°C., if free alkali is present, it is split into nuclein and a proteid. If soluble salts of lime are present, the nucleoproteid unites with the lime, and the product has the property of converting fil^rinogen into fibrin, and is identical with fibrin-ferment or throrabin ; inasmuch as the nucleo- proteid precedes and becomes changed into thrombin, it is termed prothrombin. Gases. — The plasma contains oxygen and nitrogen in solution, and carbon anhydrid both in solution and also in combination as sodium carbonate and bicarbonate. The amount of oxygen in the plasma is very small : in the dog, 0.25 per cent. Coagulation of Blood. — When blood is ^yithdrawn from the circulation it undergoes coagulation, consisting in the produc- tion of a clot from which is subsequently expressed a fluid — the serum. The length of time required for coagulation varies in the blood of different animals. In human blood the change manifests itself in about two or three minutes. When the blood is withdrawn from the vessel it is fluid, but at the end of two or three minutes its fluidity is so much diminished that it will not flow ; this consis- tency increases until at the end of eight or ten minutes the entire quantity of blood becomes a mass resembling currant-jelly in color and consistency. This jelly-like mass becomes more and more consistent, squeezing out upon its surface a few drops of a straw- colored fluid — the serum. As the shrinking of this gelatinous COAGULATION OF BLOOD. 287 mass — iJie clot — continues, it separates from the sides of the vessel in which the hUxxl was received, and the serum is squeezed out on all sides, until at length there is a more or less solid clot floating in a consitlerahle quantity of serum. The entire process requires from ten to fortv-ei,o:ht hours. When examined, the clot is found to be made up of tibrin and corpuscles, the red corpuscles giving to it the red color. The white corpuscles may at first be entangled in the meshes of the fibrin, but by virtue of their ameboid move- ment thev soon escape into the serum. The serum has the same composition as the plasma minus the fibrinogen. Although the corpuscles are denser than the plasma, still the difference is so slight and the process of coagulation so rapid that betbre they can settle they are entangled in the meshes of the fibrin as it fi)rms, and thus become a part of the clot. If any- thing occurs to delay coagulation, the corpuscles settle, and the clot is then less red and more yellowish. This delay may be brought about by the addition of a 27 per cent, solution of magnesium sulphate or other neutral salt, the plasma being then termed sd/fed p/asma; it occurs also in inflammatory processes, and hence in the olden time, when venesection or " bleeding " w^as commonly practised, this crusta phlogistica, or " buffy coat," was always looked for bv the phvsician, and when it formed was considered as evidence that the bleeding was justifiable. That the physicians of that period were not alwavs right in this judgment is now known, for a liuify coat will form" in blood which is hydremic, a condition in which bleeding is contraindicated. In horses' blood, wdnch normally coagulates verv slowly, this "buffy coat" always forms. It is simplv the fibrin w^ithout the corpuscles, or at least without enough of them to give the red color Avhich the clot usually possesses. Influences which Retard Coagulation.— Coagulation is retarded bv cold, by solutions of sodium or magnesium suli)hate, by a diminished'amount of oxygen, by an increased amount of carbon dioxid, bv acids or alkalies", by egg-albumin, by oil, by a solution of album'ose, and bv extract of the head of the leech. It is well known that the blood drawai from the vessels by this animal does not coagulate within its body. It is supposed that its saliva contains an albumose which prevents clotting of the blood. Solutions of potassium or sodium oxalate also prevent coagulation. The explanation of this action is that the calcium which is required for the process is precipitated as calcium oxalate. Venous blood coagulates more slowly than arterial, because of the lessened amount of oxvgen and the increased amount of carbon dioxid. It is said that blood from the capillaries does not coagulate at all. It is the i)revalent opinion that menstrual blood does not clot ; this, strictlv speaking, is not true. If the blood was collected as it jcomes from the uterine vessels, it w^mld doubtless coagulate as does other blood ; but when it is mixed with the acid vaginal 288 THE BLOOD. mucus its coagulation is then impeded. Then, too, during the menstrual period some of the blood undergoes clotting within the uterine cavity or in the vagina : that which escapes and which is regarded as menstrual blood is for the most part only serum, which, of course, does not coagulate. Influences which Hasten Coagulation. — Heat hastens coagulation, as does motion of the l>lood, as in whipping it with twigs or rods. In general, anvthing which tends to break down the leukocytes or plaques from which the nucleoproteid prothrombin is derived will cause the latter to be set free and favor coagulation. Causes of Coagulation. — Perhaps no physiologic question has excited more controversy than that which deals with the cause of blood-coagulation. Xormally, blood remains fluid within the blood-vessels, but within a few minutes after withdrawal it begins to undergo coagulation. What is the explanation ? It has been suggested that blood-coagulation is due to exposure to the air. It is true that contact w^ith the air hastens coagula- tion, but that this is unnecessary to the process is shown by the fact that coagulation w^ill take place under mercury when all air is excluded. Nor can it be due to the cooling the blood undergoes wdien it is exposed to the air, for, as already noted, cold retards coagulation, while heat aids it. It has also been suggested that the fluid condition of the blood in the circulation is due to its motion, and that it clots when it comes to a state of rest. But experiment shows that motion, such as the beating of blood with wires, hastens coagulation. Experiments demonstrate that the fluidity of the blood is main- tained only when the blood is in contact with the normal lining membrane of the blood-vessels : when this relation is interrupted, either by disease, or by death or injury of the membrane, or by withdrawal of the blood from the vessel, the fluidity ceases and the blood coagulates. The property of coagulation possessed by blood is of great service in arresting hemorrhage. There are individuals in whom bleeding, which in most people would be only slight, amounts to a dangerous hemorrhage, often requiring surgical skill for its arrest, and in some instances being so uncontrollable, even by the most skilful treatment, that death results. Such persons are called bleederfi, and on them surgeons hesitate to perform any opera- tion, however trivial, the extraction of a tooth even being often followed by an alarming loss of l>lood. This condition is spoken of as hemophUia or hemorrhagic diathesis. It is proliable that in such cases the fibrinogen is very deficient. Theories of Blood-coagulation. — From the many theories which have from time to time lieen advanced to explain this ])rocess, we shall select a few, each of which, although perhaps not now held in its entirety, still has elements in it which, combined w'ith those cOAari.ATiox or blood. 289 of other tlioories, cutrr into the ()j)iiii()ns licM l>y the best authorities in retjurd to this as yot iiiisolvt'd prohU'iii. All oxphinutions have as tlieir basis the pru(hietion of insohible fibrin from soluble fibrinogen, but as to how this change comes about, or the agencies which cause it, there is great disagreemont. Tlicori/ of Schmidf. — The proteid now known as paraglobulin Schmidt termed fibrinoplddlii, and in his theory this substance, under the infiuence of jibrln-fcnneiit, which he later called thrombin, enters into combination with fibrinogen, the result being fibrin. This ferment was obtained by adding alcohol to blood-serum, and extracting it from the ])recipitate by water ; it was di'stroyed by a temperature of 65° C, and had the power of coagulating a considerable amount of fibrinogen ; it resembled, therefore, the ferments or enzymes, and was considered by Schmidt to belong to that class. He later considered that fibrinogen was derived from paraglobulin. Theory of Hcunriiarnten. — This experimenter demonstrated that paraglobulin takes no part in the process of coagulation, so that at the present time it does not enter as a fiictor into any of the theories of blood-coagidation. In Hammarsten's theory there are but two factors : fibrinogen and fibrin-ferment. The action of the ferment splits the fibrinogen into fibrin, which is insoluble, and fibrin-r/Iobnlin, which remains in solution. Schmidt, Hammarsten, Freund, Pages, and others have shown that salts of calcium play a very important part in the coagulation process. Theory of PeheJharlng. — This theory supposes that the fibrin- ferment of Schmidt is composed of nucleo-albumin and calcium, and that the calcium leaves the nucleoproteid and unites with fibrinogen, the compound of the two being fibrin. The nucleo- all)umin comes from the leukocytes and plaques, but does not exist in normal blood. As soon, however, as blood is shed, these cells disintegrate, with the result of setting free the nucleoproteid. As has already been stated, analyses show the same amount of lime in fibrinogen as in fibrin, so that this theory cannot be sustained. Theory of LiUenfeld. — The originator of this theory attributes to the nucleoproteid the power of splitting the fibrinogen into a globulin and fhrombosin, which latter unites with lime to form fibrin. He regards this power as due to the nucleic acid, and! states that acetic or anv other weak acid will effect the same change in fibrinogen. This theory has also its weak points, and there is great doubt whether the clot is fibrin in any true sense of the term. Perhaps we can in no better way present to our readers the present status of this subject, which is at best unsatisfactory, than by giving the views of Schafer in his Text-book of Phj/i^i- olor/y. The evidence seems fairly conclusive that three factors are 19 290 THE BLOOD. essential to bring about coagulation of the blood. These are fibrinogen, the nucleoproteid prothrombin, and soluble lime salts, the two latter acting in combination, and forming Schmidt's fibrin- ferment or thrombin. In the normal blood-vessels the prothrom- bin and lime have not entered into the necessary combination or interaction which enables them to act as a ferment upon the fibrinogen. This nucleoproteid prothroml>in cannot hy itself act as a ferment, but must be exposed to the acting soluble lime salts ; it does not follow, however, that the thromlnn is a compound of the nucleoproteid and lime ; nor is there any certainty as to just what the interaction is. The prothrombin doubtless comes from the leukocytes and plaques ; but it is not necessary to suppose that they always undergo disintegration to produce it. It is also probable that the red corpuscles may contribute to this production of nucleoproteids, for they contain them, and the same is also true of the ejiithelial cells of the blood-vessels, which are doubt- less composed of living protoplasm. Schafer sums up the evi- dence as to coagulation as follows : 1. That the coagulation of blood — /. f.. the transformation of fil)rinogen into fibrin — requires for its consummation the inter- action of a nucleoproteid (prothrombin) and soluble lime salts, and the consequent production of a ferment (thrombin). 2. That eitlier nucleoproteid is not present in apprecialjle amount in the plasma of circulating blood, or that the interaction in question is prevented from occurring m itliin the blood-vessels by some means at present not understood. 3. That the nucleoproteid (prothrombin) appears and the inter- action occurs as soon as the blood is drawn and is allowed to come into contact with a foreign surface, the source of the nucleoproteid being in all pmbabilitv mainly the leukocytes (and blood-platelets). 4. That under certain circumstances and conditions either the nucleoproteid does not appear in the plasma of drawn blood or it appears, but the interaction between it and lime salts is prevented or delayed. 5. That the nucleoproteid ('prothromljin) appears in the plasma of circvJotiiig hlood under certain conditions, Ijeiug in all probabil- itv shed out from the white corpuscles and blood-platelets, or in some cases even from the red corpuscles ; and that when shed out under these conditions from the corpuscles, or when artificially injected into the vessels, it tends at once to interact with the lime salts of the plasma and to form fibrin-ferment (thrombin), intra- vascular coagulation being the result. 6. That under other conditions eitlier the shedding out of nucleoproteid from the corpuscles or its interaction with the lime salts of the plasma may be altogether prevented and the l)lood rendered incoagulable, unless nucleoproteid is artificially added, or unless a modification of the conditions is introduced which will REGENERATIOS OF BLOOD. 2*J1 jx-nnit of the interaction of the nuck'itproteid with lime to form tennent. 7. Tluit the niieleo}>roteid (})r<)thronil)in) i» incompetent, in the entire absence of lime salts, to promote the transf(»rmation of fihrinoo-en into fii)rin ; hut, as a result of its interaction with lime salts, it becomes transtormeil into a terment (tliroml)in), which, under suitable conditions of temperature, and the like, produces tibrin. 8. That either the place of nucleoproteid in coagulation mav be taken by certain all)umoses, such as those found in snake-venom, and i)v certain colloidal suijstances, such as those prepared bv (rrimnux ; or that such substances may act by sotting free nucleo- proteid from the leukocytes and other elements in the blood, or from the cells of blood-vessels, and thus indirectly promote coagu- lation. The colloidal substances referred to in paragraph 8 were three in number, and were artificially prepared by Grimaux, and presented many of the characteristics of proteids. They all gave the xantho- proteic reaction and in other ways resembled the proteid class. Thus when injected into the veins of animals, as the dog, cat, or guinea-pig, they caused intravascular coagulation, resembling in this respect nucleoproteid. It is suggested l)y Schafer that thev produce this effect not directly, but l)y setting free the nucleo- proteid from the leukocytes, inasmuch as there is no disintegration of the red or white corpuscles, nor any apparent change in the epithelium of the vessels. Regeneration of Blood. — One of the striking peculiarities of the blood is the rajiidity with which it is renewed after hemor- rhages. The l)lood constitutes about 7.7 per cent, of the weight of an adult ; and it is estimated that a hemorrhage in which no more than 3 per cent, of the weight is lost will not be fatal, and that the plasma will be renewed in such cases within fortv-eight hours, although it may require weeks for a renewal of the red corpuscles. In the treatment of severe hemorrhages it is now the practice to inject into the veins physiologic salt solution (p. 81). The rationale of this is stated by Howell to be that in normal blood the number of red corpuscles is greater than that necessary for a barely sufficient supply of oxygen, and that if after a hemor- rhage the quantity of fluid in the vessels is increased, the circula- tion is made more rapid, and the remaining corpuscles are made more etfective as oxygen-carriers ; this office is made still more effective by keeping the corpuscles from becoming stagnant in the capillary areas. In proportion as intravenous transfusion of salt solution has come into favor for the treatment of hemorrhages, in a similar proportion has transfusion of blood been abandoned. From what has been said, it will readily be understood that in the withdrawal 292 LYMPH. of blood from the vessels of a lower animal or man the conditions are most favorable for bringing about the destruction of leuko- cytes, and the consequent setting free of the nucleoproteid pro- thrombin. To throw this material into the circulation of a living animal is to invite coagulation within the vessels, a condition which is dangerous in the extreme, inasmuch as clots would be inevitably carried into the smaller arteries of the brain, causing embolism, and producing a fatal result. It has also been demonstrated that the injection of the serum of the blood of some animals into the circulation of others, as that of man into the vascular system of a rabbit, destroys the red corpuscles. This is the globulicklal action of serum. Such a result might follow in the case of blood-transfusion, unless special care was taken to select an animal whose blood did not possess this action upon the blood of the animal on which the operation was to be performed. LYMPH, Lymph is an alkaline fluid which is derived from the blood, and while, generally speaking, its constituents are the same as those of the plasma, still these differ in amount to a considerable degree ; nor is the lymph ol)tained from all parts of the body uniform in composition. Chemical Composition of I/ymph. — The following anal- ysis is of lymph obtained from a case of fistula of the thoracic duct in man, and is reported by Munk and Rosenstein. In 100 parts of lymph there are : Total solids 3.7 to 5.5 Proteids 3.4 "4.1 Substances soluble in ether 0.046" 0.13 Su2;ar (dextrose) 0.1 Salts 0.8 "0.9 In another specimen the inorganic constituents were found by Hensler and Danhardt to be : NaCl 0.614 Na.,0 0.057 K.,6 0.049 CaO 0.013 Co, 0.0815 MgO \ Fe.O, I traces '3 ^ P,0« ^*^''' I 0.033 From lymph only 0.1 per cent, of fibrinogen can be obtained, while from plasma the amount obtainable is 0.4 per cent. Besides fibrinogen, paraglobulin and serum-albumin are also present. Lymph coagulates more slowly than the blood, and the clot is less firm. Urea is present to a greater amount than in plasma. Histologic Composition of lyympli. — Examined under the microscope lymph is found to contain colorless cells, lympho- ORIGiy OF LYMPH. 293 cnhx which puss into the hl.x..l with the lymph and there hecome leukocyte.^ (p. 283). Fat-irlobulos are also found, especially alter •I nu-:il" and in the Ivniph from the thoracic duct. Origin of Lyniph.— While there is no doubt that the source of the lymph is the blood, still there is a difference of opinion as to the manner in xvhieh it escapes from the blood-vessels. Theory of Ludwig.— Lmhvi.o- believed that the pressure ot the blood in the capillaries was suffieient to cause the plasma to hlter throno-h their walls, thus formincr the lymph. He also believed that ditfusion plaved a part in lymph-formation. He expressed hi^ view^ as follows : '' The blood which is contained in the vessels mu^t alwavs tend to equalize its pressure and its chemical con- stitution with those of the extravascular fluids, ^bH-h aij only sei)arated from it bv the porous blood-vessel walls. J*, i«i' ex- ami)lo the quantitv of blood in the vessels has increased, the mean blolxl-pressure is also increased, and at once a portion of the blood is driven out into the tissues by a mere process of filtration, ihe same result is brouo-ht about when the constitution of the blootl is altered bv the absorption of food or by increased excretion by tlie kidnevs, 'blood, or skin, or when the composition of the tissue- fluids" is altered in consequence of increased metabolic changes taking place in the tissues. In the latter case the changes brouc;ht about in the Ivmph are effected by processes of diffusion. This^'theory of Ludwig may, therefore, be termed that oi JiU ration and diffusion. . , t i ,i i • + Theory of Heidenhain.— This experimenter studied the subject of Ivmph-formation bv examining the flow from the thoracic duct' He found that if the thoracic aorta was obstructed there would follow a fall of arterial blood-pressure below the obstruc- tion, and vet there was no diminution in the flow of Ivmph in the thoracic duct, and in some cases it was increased. If l^^n^^ ^^^^^^ formed bv filtration from the blood, a diminution of blood-pressuie should have been followed bv a corresponding lessening of lymph- produetion. Other experiments demonstrated tliat the flow of Ivmph might be increased without correspondingly increasing the blood-pressure. He also found that if commercial peptone and some other substances were injected into the blood-circulatiou the amount and concentration of the lymph would be increased, al- though blood-pressure might be reduced ; also that if concentrated solut^ions of sodium chlorid or sugar were injected, the flow ot Ivmph would be increased and its concentration diminished. it blood-pressure was increased, it was so but slightly. Heidenhain terms substances having the power of increasing the flow of ymph lymphagogues. These experiments demonstrated that the ympli mav contain more of injected substances than the blood-plasma, while at the same time there is no increase in blood-pressnre From these experiments Heidenhain formed the opinion that 294 LYMPH. filtration and diffusion cannot explain all the facts connected with the formation of lymph, but that it is to be attributed to a selective power of the endothelial cells of the walls of the capillaries, and that lymphagogues act by stimulating these cells. This subject has been investigated by Starling, who finds many reasons for upholding the theory of Ludwig as against that of Heidenhain. For a full discussion of the sul)ject we must refer our readers to Schiifer's Physiology, but it will not be out of place to quote Starling's conclusions. He says : " Thus a renewed investigation of the facts discussed by Heiden- hain has shown that they are not irreconcilable with the filtration hypothesis, but rather serve to support it. At the same time tiiey prove the extreme importance of the factor upon Avhich so much stress was laid by Cohnheim, namely, the nature of the filtering- membrane. In fact, we may say that the formation of lympii and its composition, apart from the changes brought about by diffusion and osmosis between it and the tissues it bathes, depend entirely upon two factors: 1. The permeability of the vessel-wall. 2, The intracapillary blood-pressure. " So far as our experimental data go, we have no sufficient evidence to conclude that the endothelial cells of the capillary walls take any active part in the formation of lymph. It seems rather that the vital activities of these cells are devoted entirely to maintaining their integrity as a filtering-membrane, differing in permeability according to the region of the body in which they may be situated. Any injury, whether from within or without, leads to a failure of this their one function, and therefore to an increased permeability, with the production of an increased flow of a more concentrated lymph. " We have no evidence that the nervous system has any in- fluence on the production of lymph in any part, except an indirect one by altering the capillary pressures in the part through the intermediation of vasoconstrictor or dilator fibers. This action is better marked in situations where the capillaries are normally very permeable or where the permeability has been increased by local injury to the vessels, or by the circulation of poisons in the blood-stream." The lyrapli-corpuscles enter the lymph as it passes through the lymphatic glands or other lymphoid tissue, such as the tonsils and the thymus gland, and become constituents of the lymph. Office of the Lymph. — The lymph after it passes out from the blood-vessels bathes the tissues, and is one of their sources of nutrition, but not the only one, for there is abundant evidence that tissues may receive their nutritive supply directly from the blood and pass into that fluid their waste-products. This muscles will do, while at the time no lymph is flowing in the lymphatic vessels of the part. When lymph accumulates, whether in a serous Plate II. A, aorta, with left vagus and phrenic nerves crossing its transverse arch ; B, root of pulmonary artery ; C, right ventricle ; D, right auricle ; E, vena cava superior, with right phrenic nerve on its outer border ; F, F, right and left lungs collapsed, and turned outward to show the heart's outline; G. inferior vena cava; H, celiac axis, dividing into the gastric, splenic, and hepatic arteries iMaclise). THE HEART. 295 cavity or in tlie collular tissue licnoath the skin, it constitutes drojisi/ or nioiui. The lymph is collected by the lyinpliatic vessels and ultimately reaches the blood-circulation again (p. 319). CHYLE. The term clii//r is applied to that portion of the lymph which comes from tiie small intestine during the period of digestion. The tissues of this portion of the body are, like all others, bathed in lymph ; but during digestion such products as enter the lacteals change its composition to a considerable extent, and the fat gives to it a milky appearance. The following is an analysis of chyle taken from a fistula of the thoracic duct in man (Patonj : Water 95.34 Proteids 1.87 Fats 2.40 Cholesterin 0.06 Lec'itliin 0.03 Inorganic constituents 0.56 CIRCULATORY SYSTEM. The blood in carrying nutrition to, and in carrying waste products from, the tissues passes through the entire circulatory system, and this constitutes the circulation of the blood. Before studying this process in detail it is essential to have a knowledge of the organs concerned in carrying it on — /. e., the circulatory organs. These are (1) the heart, (2) the arteries, (3) the capillaries, and (4) the veins. THE HEART. The heart, together with the great blood-vessels at its base, is enclosed in the pericardium, a fibro.serous membrane having an external fibrous and an internal serous layer. The serous layer not only lines the inner surface of the sac, forming the parietal portion, but it also covers the heart itself; this portion is the visceral portion or epicardium ; its structure is similar to that of other serous membranes, being composed of connective tissue and elastic fibers, beneath which are the blood-vessels, nerves, and lymjihatics of the heart. The myocardium, or muscular structure of the heart, is composed of transversely striated mu.scular fiber-cells, each con- taining a single nucleus. They differ from voluntary muscle in possessing no sarcolemma, in branching and uniting Mith adjoining cells, and in having their strise less pronounced (p. 61). The endocardium, which lines the heart and takes part in the formation of the valves, resembles the epicardium in struct- ure, and is covered by endothelium. The heart (Figs. 157, 158) is a hollow muscular organ whose 296 CIRCULA TOR Y S YSTEM. functions consist in acting as a reservoir and also as a pump, the auricles being the reservoir and the ventrides being the ])unip (Plate 2). It is about 12.5 cm. long, 8 cm. wide in its widest part, and 6.3 cm. thick at its thickest part; its weight is al^out 300 grams in the adult. It has a conical form, its base being above and to the right, and its apex below and to the left. It is divided longitudinally by a partition or septvm into a right and a left half, which are sometimes denominated the right heart and the left heart. Each half is com- posed of an auricle and a ventricle ; thus there are four cavities — the right au- ricle, the right ventricle, the left auricle, and the left ven- tricle. The right auricle (Fig. 157) is somewhat larger than the left, and has the thinnest Avails of the four cavities, measuring about 2 mm. in thickness. Discharging into this cavity are the superior and inferior vense cavse, at the mouths of which there are no valves. Within the cavity is the Eustachian valve, which will further be described when discussing the fetal cir- culation. This valve is sit- uated between the opening of the inferior vena cava and the auriculoventricular orifice. The right ventricle (Fig. 1 57) has walls whose thickness is greater than that of either auricle, but less than that of the left ventricle. The cavity of the right ventricle comnninicates with that of the right auricle by the right auriculoventricular orifice, at which is situated the tricuspid valve. It ordinarily contains, when filled, 87 grams of blood (p. 304). Connected with this ventricle is the pulmonary artery, at whose point of junction with the ventricle is the pulmonary orifice, at which is situated the pul- monary valve. The left auricle (Fig. 158) is not so large as the right, but its walls are thicker. Dischar^inff into it are the two right and the Fig. 157. — Interior of right auricle and ventricle, exposed by the removal of a part of their walls: 1, superior vena cava; 2, in- ferior vena cava ; 2', hepatic veins ; 3, 3', 3", inner wall of right auricle; 4,4, cavity of right ventricle ; 4', papillary muscle ; 5, 5', 5", flaps of tricuspid valve; 6, pulmonary ar- tery, in the wall of which a window has been cut ; 7, on aorta near the ductus arte- riosus; 8, 9, aorta and its branches; 10, 11, left auricle and ventricle (Allen Thomson). THE HEART. 297 two left pulinonarv veins, the former coming from tlie right and the latter from the left lung. The left veins sometimes join, and have hut a single opening, in which case there would, of course, he hut three openings instead of four. At these openings there are no valves. The left ventricle (Fig. 158) is by far the most powerful of the four subdivisions of the heart. Its walls are three times as thick as those of the right ventricle. The capacity of its cavity is the same as that of the right. The left auricle and ventricle communicate by the left auriculoventricular orifice, at which is situated the mitral valve. Connected Avith this ventricle is the aorta, the opening of communication being the aortic orifice, at which is situated the aortic valve. On the inner surface of the ventri- cles the muscular tissue projects, and forms the cohimnce eariieoe, or fleshy columns ; some of these are ridges only, while others are attached at both ends, but are unattached in the middle, while still others project into the cavity and are attached at one ex- tremity only ; tlie latter are the mus- culi papilhtrei^, or papillary muscles. Cardiac Valves. — There are four sets of valves in the heart : (1) The tricuspid; (2) the pulmonary; (3) the tricle, opened and part of their •, 1 1 / 1 \ j-i ^ „^..<-;^ " walls removed to show their cavi- mitral ; and (4) the aortic. The tricuspid valve (Fig. 159) is situated at the right auriculoventricular orifice, and, as its name implies, con- sists of three cusps or segments. The bases of these cusps are attached to the Openino;, while the other edges are semilunar valves; 8, pulmonary /. J ^ .1 i^ 1 1 .1 arterv: 10, aorta and its branches tree, and to them are attached the (Alien Thomson). chordce tendinece., or tendinous cords, the other ends being connected with the free extremities of the musculi papillares to which reference has been made. This valve, when shut, closes the right auriculoventricular orifice ; when open the segments are in the cavity of the right ventricle. The tendinous cords prevent these segments from passing into the cav- ity of the auricle at the time of the valve's closure, while the papil- lary muscles by their shortening keep the cords taut at the time of the ventricle's contraction, as will be seen later. Fig. 158. — Left auricle and ven- ties ; 1, right pulmonary vein cut short; 1', cavity of left auricle; 3, 3", thick wall of left ventricle ; 4, portion of the same with papil- lary muscle attached ; 5, the other papillary muscles; 6, 6', the seg- ments of the mitral valve ; 7, the figure in aorta is placed over the 298 CIR C L'LA TOR Y S YSTEM. tua BAV Fig. 159. — Orifice of the heart, seen from above, both the auricles and the great vessels being removed : PA. pul- monary artery and its semilunar valves: AO. aorta and its valves; P,.A V. tricuspid, and LA V. bicuspid valves: J/I'. segments of mitral valve : LV. segments of tricuspid valve (Huxley). The pulmonary valve is sometimes spoken of as the pulmonary semilunar valve or valves. It is composed of three, occasionally two, segments, and is situated at the beginning of the pulmonary artery. These .segments are at- tached at their bases to the wall of the artery, and on the free edge of each is a projection, the corpus Araniii. When the valve is open the segments lie against the walls of the artery ; when it is shut they are in contact, and thus close the orifice of tiie pulmonary arter}-. The mitral valve is sometimes described as the bicuspid, because it consists of two cusps. The attachments of the segments, the presence of chordae, and the other anatomic points referred to in speaking of the tricuspid valve are to be seen in connection with the mitral. It closes the auricu- loventricular orifice. The aortic valve resembles in all essential particulars the pulmonary ; it likewise is .sometimes called the semilunar valve, and closes the aortic orifice. The ventricular septum is the partition between the right and left ventricles. It is closed at all periods of life. The auricular septum, between the auricles, is closed from the tenth dav after birth ; prior to this time and during fetal life it has an openino-. the foramen ovale, which serves as a means of communi- cation between the right and the left auricles. Structure of the Valves. — The valves consist of reduplications of endocardium, Ijetween which is fibrous tissue. THE ARTERIES. Arteries are composed of three coats : (1) An internal, tunica intima ; (2) a middle, tunica media; and (3j an external, ^{^nica advent it ia. The ttinica intima consists of a layer of pavement-epithelium (Fig. 160), the cells being polygonal, oval, or fusiform, termed endothelium, and of a network of elastic fibers or a fenestrated membrane (Fig. 161 ). Between these two layers is a subepithelial layer consisting of connective tissue. The tunica media has a special physiologic interest. In the large arteries — that is, those larger than the carotids — this coat is principally yellow ela.stic tissue, only about one-fourth being mus- cular tissue.' Vessels of this size are therefore characterized by THE ARTERIES. 290 their elasticity. In the arteries t>f niedinni size — tliat is, those between the carotids and those having a diameter of al)oiit 2 mm. — the amount of muscular tissue is very much increased, while tiie Endothelium of the iutinia. Intiuia. Media. Adventitia with non-striated mus- cle-fibers in cross- section. Fig. 160. — Section through human artery, one of the smaller of the medium-sized ; X 640 (Bohm'aud Da\-idotr i. elastic tissue is also well represented. Such arteries possess, there- fore, both contractility and elasticity. In the small arteries — that is, those less than 2 mm. in diameter — the external coat gradually ^^^ V Endothelium of the intima. Media. Fenestrated — elastic mem- brane. ^ Elastica ex- "^ terna. Inner layer of adventitia. Outer layer of adventitia. t::^ Vasa vasorum. Fig. 161.— Cross-section of the human carotid artery ; X 150 (Bohmand Davidoff). disappears until in the arterioles there remains only muscular tissue, representing the middle coat and the internal coat. These vessels are endowed with the property of contractility. 300 CIRCULATORY SYSTEM. The tunica adventitia consists of l)iinclles of white connective tissue and elastic tibers, and gives to tlie artery its strength. This coat merges with the sheath of the arter}^, which is composed of fibro-areolar tissue, and in this are the blood-vessels which supply the arteries, the vasa vasonim. THE CAPILLARIES. The capillaries are minute vessels, having in general a diameter of 12 fi, though this differs very considerably in the diflPerent organs of the body. They are smallest in the brain and intestinal mucous membrane, and largest in the skin and bone-marrow, where they have a diameter of about 20 ft. Their arrangement is also subject to great variation ; thus in the lungs and mucous membranes they form rounded meshes, while in muscles and nerves the form of the mesh is elongated. In some organs they are very close together, as in the lungs, while else- where they are separated to a considerable extent, as, for instance, in the external coats of arteries. In general, where an organ is active, as is the kidney, there the number of capillaries is the Fig. 162. — Endothelial cells of capillary (o) and precapillary (ft) from the mesentery of a rabbit; stained in silver nitrate (Huber). greatest ; and where it is inactive, as is the case with bone, the capillaries are correspondingly lacking. The walls of the capillaries consist of endothelial cells joined edge to edge by a cement-material. From a physiologic standpoint this portion of the circulatory apparatus is the most important, as all the changes between the blood and the tissues take place while the blood is passing through the capillaries. THE VEINS. The structure of the veins is in many respects similar to that of the arteries. They are likewise composed of three coats, but CIRCULATION OF THE BLOOD. 301 the iiiiddle coat is the thinnest — so much so, indeed, that, while the arteries when cut remain patulous, the veins collapse. This coat contains both elastic and fibrous tissue : the former gives the vessels some elasticity, while to the latter is attrii)utable the greater strength of the veins as compared Avith the arteries. The greater thickness of the arterial wall woidd seem calculated to make these vessels the stronger, but, although possessed of thin walls, still the white fibrous tissue which aids in their formation gives the veins greater resisting power. Valves are to be found in most of the veins, but are absent in those whose diameter is less than 2 mm. ; also from the vena cava, hepatic, portal, renal, uterine, ovarian, cerebral, spinal, pulmonary, and umbilical veins. The valves are so arranged that they permit the blood to flow in the direction of the heart, but prevent its flow in the opposite direction. They consist of a reduplication of the internal coat, together with connective and elastic tissue to give them strength. Like the arteries, they are supplied with vasa vasorum to nourish their walls. QRCULATION OF THE BLOOD. The course of the blood, starting from any point, may be traced through the circulatory apparatus. Beginning with the right auricle, the blood flows into this cavity from the venae cavse (inferior and superior) ; thence through the right auriculoven- tricular orifice into the right ventricle ; thence into and through the pulmonary artery to the lungs ; thence by the pulmonary veins into the left auricle ; thence through the left auriculoventricular orifice into the left ventricle ; thence into and through the aorta and the arterial system to the capillaries ; through these vessels to the veins, by which, through the ven» cavse, it returns to the right auricle, the place of beginning. " Cardiac Movements. — If the heart is exposed in a living animal — a dog, for example — it will be seen that the ventricles are at one time in motion and at another time at rest. Each period of motion and rest constitutes a jnilsafion or a cardiac cycle, and these pulsations recur very rapidly, so much so that the inter- vals are recognized with difficulty. These different states of the heart are better detected by the sense of touch than by that of sight. If the ventricles are grasped by the hand, it will be found that, corresponding with the resting stage, the muscular tissue composing them is soft and flaccid, Avhile during the active stage it is hard and resisting. If these movements are studied still more carefully and analyzed, it will be found that the beginning of the cardiac movement, which immediately follows the stage of rest, occurs in the auricles, in the region of the openings of the venae cavje on the right side, and of the pulmonary veins on the left ; that this movement is propagated along the auricles in the direc- 302 CIRCULATORY SYSTEM. tion of the ventricles ; and that by the time it has reached the auriculoventricular orifices it has ceased at the orifices of tlie veins, and the muscular tissue in this region has begun to relax. It is to be noted that the auricles act synchronously, so that whatever is the condition of one auricle as to relaxation or con- traction of its muscular tissue, the same condition exists in the other. This contraction of the auricles is spoken of as the auricular systole, and has something of a peristaltic character, which has already been studied in connection with the stomach and small intestine, although differing materially in that it is much more rapid. Up to this time the ventricles are relaxed, or in a condition of diastole ; but as soon as the auricular contraction reaches the ventricles these organs take it up, although in a different manner. For, while in the auricles one portion is contracting while another is relaxing, in the ventricles the whole mass of muscle contracts at once with a degree of suddenness and vigor which might be expected of so large a mass of striped muscular tissue. This contraction is the ventricular si/stole, and while it is taking place the auricles are relaxing throughout ; this relaxation constitutes the auricular diastole. Thus the auricular systole and ventricular diastole, and the auricular diastole and ventricular systole, are respectively synchronous. Immediately after the systole of the ventricles these structures relax, and for a brief period the whole heart, both auricles and both ventri(;les, is in a state of relaxation ; this is the pause of the heart. The work performed by the ventricles is so much more important than that of the auricles that when the terms systole and diastole are used, reference is always had to these states of the ventricles, the auricles being practically ignored. To designate the corresponding states of the auricles it is always necessary to speak of the auricular systole and diastole. Cardiograph. — The cardiograph is an instrument for recording the movements of the heart, the record itself being a cardiogram. The form most used is that of Marey. It consists of a metal box, over the mouth of which an elastic membrane is stretched, to which a knob is attached (Fig. 163). This knob, in another form of this instrument, is attached to a spring (Fig. 164). This box or tympanum, is in connection with another box, the recording tambour, by means of a tube, and upon the elastic membrane of this rests a lever. The first tambour is so fixed in place against the chest wall as to bring the knob over the point where the cardiac impulse is felt, and the movement of the knob is com- municated to the membrane, sending a Avave of air through the tube and causing the lever to move at every impulse ; the point of the lever makes its record on a revolving drum or kymograph, covered with smoked paper (Fig. 166). This may be varnished CIRCULATION OF THE BLOOD. 303 with shellac for preservation. Fit:::. l'>-i shows a cardiogram taken ill this way. The same iustrumeut in a modified form is used to obtain a record of the endocardiac pressure. In this case Intlia-riiijber hairs commnnicatino; with the recording tambours are introduced throurch the jnirular vein into the cavities of the right auricle ami ventricle! This method is of service only in an animal with larire vessels, such as the horse. Movements of Blood diiring Systole and Diastole. — Before con- sidering other movements of the heart it will be well to study the course of the blood while contraction and relaxation of the mus- cular tissue of this organ are taking place. The venous blood, returning from the head and upper extrem- ities by the superior or descending vena cava, and from the portion of the bodv below the heart bv the inferior or ascending vena Fig. 163.— Diagram of Marey's cardiograph: A, knob attached to flexible membrane tied over end of metal box ; the kuob is placed over the apex-beat ; c, folded edge of membrane ; B is the tube commu- uicatiug with a recording tambour. Fig. 164.— Cardiogram taken with Marey's cardiograi)h : a, auricular systole ; v. ventricular systole : d, diastole. The arrow shows the di- rection in which the tracing is to be read (Stewart). cava, flows into and through the right auricle, passing into the right ventricle through the^'right aurieuloventricular orifice. The trTcuspid valve at this time is open, and offers no obstacle to the passage of the blood. Blood is also at the same time flowing into the left auricle and ventricle from the lungs. More blood enters the auricles than can at once pass out into the ventricles ; conse- quentlv some blood accumulates in, and gradually fills, the auricles, although at the same time as much blood is flowing into the ven- tricles^as the aurieuloventricular orifices will permit to pass, nearly filling these cavities, and floating up the segments of the mitral and tricuspid valves until thev are nearly closed. This is the condition at the end of the pause. At this moment begins the auricular svstole. Xear the ends of the veins which discharge into the auricles— that is, the vense cavse and pulmonary veins — are muscular fibers ; these fibers contract, diminishing the size of the orifices of the veins, thus taking the place of valves, and par- tiallv preventing a back-flow of blood into these vessels. Then 304 CIRCULATORY SYSTEM. the muscular fibers of the auricles in contiguity with these fibers contract, the movement spreading to the adjoining fil)ers until the wave of contraction has reached the ventricles. This auricular contraction forces more blood into the ventricles, and as the fibers relax the blood enters the auricles again from the veins. It will thus be seen that the interval of time during which the venous flow is arrested is the briefest possible. The principal office of the auricles is to serve as reservoirs to supply the ventricles ; the work they do in completing the filling of "these cavities is com- paratively unimportant. The auricular systole is followed by the systole of the ventri- cles. These cavities are at this time filled with blood, and the auriculoventricular valves are nearly closed, the segments having been raised up by the blood from the auricles. The ventricles, as has been stated, contract en masse, and the blood which they con- tain is compressed with great force. Under the pressure it tends to escape from the ventricles through all outlets — on the right side through the right auriculoventricular orifice back into the right auricle, and through the pulmonary orifice into the pulmonary artery ; on the left side through the left auriculoventricular orifice into the left auricle, and through the aortic orifice into the aorta. The pressure of the blood instantly closes the tricuspid valve, and thus prevents the blood from going back into the right auricle. The same force closes the mitral valve, and regurgitation of blood into the left auricle is made impossible. The pulmonary and aortic valves, as has been stated, open from the ventricles into the arteries. At the beginning of the ventricular systole these valves are closed, but when systole occurs the pressure of the blood forces them open, and the contents of the ventricles, 100 c.c. for each, are propelled into the pulmonary artery and the aorta respectively. Authorities differ as to the amount of blood which is expelled from the ventricle at each pulsation, and which is termed the pulse volume ; some place it as low as 50 c.c, and others as high as 190 c.c. Stewart gives it as his opinion that the average amount of blood thrown out by each ventricle at each beat is not more than 70 c.c. or 80 c.c. (87 grams). If the average amount is 100 c.c, the whole blood of the body would pass through the heart in about a minute. In accomplishing this the ventricles have to over- come the pressure which the blood already in the arteries is exert- ing on the other side of the valves to keep them closed. This pressure in the aorta is equal to a column of mercury 200 mm. high, and in the pulmonary artery is one-third as much. The amount of work done by the ventricles daily in thus forcing blood into the arteries is equal to that which is performed bv an indi- vidual weighing 75 kilograms in climbing a mountain 806 meters in height. As soon as the ventricles cease their contraction the pressure CIRCULATION OF THE BLOOD. 306 of the 1)1()()(1 in tlic arteries elo.se.s the pulmonary and aortic valves, the ventricles l)ei;in their diastole, and the pansi; of the heart eonnnenees. As it was at this point that the consideration ol" the changes which take place was begun, the study of a cardiac cycle, cardiac period, or heart-beat is now completed. If the time occupied by such a period is divided into one hundred parts, it will be found that the auricular systole lasts durint;- nine of the parts, the ventricular systole during thirty, and the pause during sixty-one ; or, in other Avords, the heart is at rest six-tenths and at work four-tenths of the time. Shortening of the Heart. — At the time of the systole of the heart (ventricular systole) the organ becomes shorter, yet the apex does not change its place, for the lengthening of the aorta which occurs compensates for the shortening, so that while the apex and base approximate the whole heart is lowered, the result being to keep the apex in its original position with reference to the chest wall. Cardiac Impulse. — The situation of the heart in the thoracic cavity is such that its apex is against the chest wall at the fifth intercostal space, the space between the fifth and sixth ribs, and about 3 cm. below and 1 cm. within the left nipple. The apex of the heart is the extreme point of the left ventricle. If the finger is placed in this region during the ventricular systole, there will be felt a tap as if something was gently striking it. This tap is known as the npex-beat. It is so called because it was formerly supposed that during the systole the heart w-as raised up and car- ried forward so as to cause the apex to strike against the chest wall and thus produce the sensation.. A more careful study of the changes which the heart undergoes during systole has, however, demonstrated that the apex of the heart is always in contact with the chest wall, and that this supposed striking does not take place. Indeed, the tap is not due to the apex at all. The term aj^tex- beat is a misnomer : it should rather be called cardiac impulse, the sensation being produced by the anterior surface of the con- tractinir ventricles swellino; out and hardening. The location at which this impulse is felt most pronouncedly is not over the apex, but higher up. If a long needle was to be introduced deeply here, it would penetrate the left ventricle at a point where the middle and lower thirds unite. The cardiac impulse is not always, even in health, detected at the same place : it changes somewhat with respiration and also with changes in the position of the body. Papillary Muscles. — It has been stated that during the ven- tricular systole the heart shortens. It is manifest that unless some provision was made this change in the shape of the heart would permit of regurgitation of the blood into the auricles, and thus would result a damming back of the blood in the venae 20 306 CIRCULATOR Y SYSTEM. cavie and pulmonary veins ; for if the chordae tendinese were of just the right lengtli at the beginning of tiie ventrieuhir systole to keep the segments of the mitral and tricuspid valves so exactly in place as not to permit a leakage, then when the ventricles shortened these cortls would be too long, and would permit the segments to enter the cavity of the auricles and there separate, leaving a considerable gap through which the blood could pass. That this does not occur is due to the papillary muscles. As the ventricles shorten, these structures contract sufficiently to take up the slack in the cords, and keep them just long enough to main- tain the proper approximation of the segments of the valves. Cardiac Sounds. — When tiie ear is placed against the chest wall in the region of the heart two sounds are heard during each cardiac period. The first of these sounds is heard loudest — that is, at its maximum of intensity — over the apex, and is by some writers called the apex-sound. For the reason that it is the first sound heard after the pause it is called the first sound, and because it occurs at the beginning of the systole of the heart (ventricular systole) it is called the s}/sfoliG sound. The second sound is heard loudest over the base of the heart, and is therefore sometimes de- scribed as the hasie sound; inasmuch as it occurs during the diastole, it has received the name of the diastolic sound. More commonlv, however, it is spoken of as the second sound. Characteristics of the Cardiac Sounds. — The first sound, as com- pared with the second, is lower in pitch and longer in duration, and has been likened to the sound of the word Iilhb. The second sound is higher in pitch and siiorter in duration than the first, and has been likened to the sound of dap. These sounds occur suc- cessively, without any interval between them ; in the pause which follows no sound is heard. Causes of the Cardiac Sounds. — The cause of the second sound is undoubtedly the closure of the aortic and pulmonary valves. This has been demonstrated by hooking back the segments of the valves, when tlie sound disappears, to reappear when the seg- ments are set free. The causation of the first sound is not so simple ; indeed, authorities are not at one on this point. The closure of the mitral and tricuspid valves contributes something to it, but the closing of tiie valves is not the sole factor, for in a heart in which there is no blood the sound may still be heard, although modified, and in such a heart the valves would not close. The contraction of the muscular tissue of the heart gives forth a sound, as does indeed the contraction of other muscles, and this is also an element in producing the first sound. The striking of the apex against the chest-wall, the so-called apex-l)eat, formerly regarded as one of the factors of the first sound, can take no part in its production, because, as has been pointed out, tliis action does not take place. CIRCULATION OF THE BLOOD. 307 Every student slidiild familiarize liiinself with the cardiac sounds, not simply by readiut^ ai)()ut them, hut hy listening to the human chest. jV. thorough knowledge ot" their character is essential to a comprehension of the diseases of the heart. It is important to remember that the impulse of the heart, the systole of the ventricles, the first sound, and the closure of the mitral and tricuspid valves arc synchronous, and that when the second sound is heard the ventricles are beginning their diastole and the aortic and j)ulmonary valves have just closed. Circulation in the Arteries. — Each time that the ven- tricles contract they send into the arteries about 200 c.c. of blood, each ventricle expelling 100 c.c. (p. 304). The arterial system is always overdistended — that is, even when the heart is at rest the amount of blood in the arteries is sufKcient to stretch their walls a little. When an additional amount of blood is forced into them by the muscular contraction of the heart, these vessels are distended still more, for the blood already in tliem cannot at once flow on in an amount equal to that which comes from the heart. If an artery at this time should be felt with the finger, it would beat against the latter, this beat being called i\\e pulse. As soon as the systole ceases the elastic coats of the arteries squeeze the blood that is ^vithin them, and this blood tends to flow away from the point of pressure in two directions — back toward the heart and onward toward the capillaries. Its backward flow at once closes the pulmonary and aortic valves, and in this direction, therefore, its progress is barred. The blood then can go only forward. Before the onward flow of the blood has ceased another systole occurs, and again the ventricles are emptied into the arteries, and thus this action continues during the life of the individual. If a cannula is inserted into the cavity of the ventri- cle, it M'ill be seen that at each systole the blood spurts out in a jet, which ceases at the end of the systole — that is, the flow from the heart is intermittent. If the cannula is inserted into the aorta, the blood will jet out at each systole of the heart, but, instead of ceasing to flow during diastole, it will not entirely cease, but will continue to flow a little under the influence of the elastic force of the aorta. If the cannula is inserted into successive portions of the arterial system farther and farther from the heart, the blood will corae out in jets as before under the influ- ence of the heart's contraction, but it will continue to flow in the intervals, the difference between the jet and the continuous flow being less and less marked the greater is the distance of the inser- tion of the cannula from the heart. In the capillaries the flow is regular and continuous, unaffected by the action of the heart. Internal Friction. — If the blood is studied as it is flowing through a small artery in the web of a frog's foot, it will be seen that in the center of the current it is flowiuir much faster than at 308 CIRCULA TOR Y SYSTEM. the sides ; this is the axial dream, and in it will he ohserved the red corpuscles. That }X)rtion of the current which is Ijetween the axial stream and the walls of the vessel moves more slowly, the rate diminishinf; from the center outward, until at the walls themselves it is at the minimum. Tliis outer portion is known as the ineti. layer. It should l>e stated that this arrangement of the current is not due to any peculiarity of the blood or of the vessels through \\ hii ]i it flows, but is present in every fluid while flowing through a tube. Between the different layers of fluid there is friction, called internal friction. The smaller the tubes the greater tlie internal friction, so that the amount of friction in the sub- divisions of the aorta and its numerous ramifications is very great, and this friction acts as an obstacle to the outflow of the blood, constituting peripheral resistance. BLOOD-PRESSURE. The systemic circuhition of tlie Ijlood — i. e., its flow from the left ventricle through the arteries and capillaries ; and back by the veins to the right ventricle again — is a movement from a point of high pressure, the left ventricle, to one of low pressure, the right Fig. 16.5. — Height of blood-pressure ih.p.) in left ventricle /.r. i : a, arteries; c, capillaries : r, veins ; r.a.. right auricle; o o, line of no pressure (after Starlings auricle. This is shown in Fig. 165, where the pressure is greatest at the left ventricle, gradually diminishing in the large arteries, until at the end of the arterial system the fall is al)rupt ; it falls gradually throughout the capillaries and veins until the large veins in proximity to the heart are reached, where it is negative (p. 311). The fact that the blood within the vessels is under varying degrees of pressure may be demonstrated by repeating the classic experiment jierformed by Stephen Hall, an English episcopal clergyman, in the year 1727. He introduced a goose-<^juill into the femoral artery of a horse, and connected it with a glass tube ; the blood rose to a height of 2.44 meters, and at each inspira- tion of the animal the column ro«o and at each expiration fell ; BLOOD-PRESS URE. 309 Fig. 166. — Diagram of the recording mercurial manometer and the kymo- graph; the mercury is indicated in deep black: M, the manometer, connected by the leaden pipe L with a glass cannula tied into the proximal stump of the left common carotid artery of a dog; .-1, the aorta ; C, the sto])-cock, by opening which the manometer may be made to communicate through R T, the rubber tube, with a pressure-bottle of .solution of sodium carbonate; F. the float of ivory and hard rubber; R, the light steel rod, kept perpendicular by B, the steel bearing; P, the glass capillary pen charged with quickly drying ink ; T, a thread which is caused, by the weight of a light ring of metal suspended from it, to press the pen obliquely and gently against the jiaper with which is covered D, the brass "drum" of the kymograph, which drum revolves in the direction of the arrow. The supports of the manometer and the body and clock-work of the kymogra])h are omittecl for the .sake of simplicity. The aorta and its branches are drawn disproportionately large for the sake of clearness (Curtis). besides this movonicnt due to respiration, there was a smaller rise at each systole and a corresponding tall at each diastole. 310 CIRCULATORY SYSTEM. This pressure under whicli the blood is in the artery which causes it to rise so high in the tube is arterial jjrej<.sure, or the blood- pressure in the arteries. Such an instrument for measuring pressure is a manometer. It is manifest that a glass tube 2^ meters in heiglit i:- imt a very convenient instrument to manipu- late, and besides the blood soon clots. To ol)viate both of tliese dithculties the mercurial raanometer was devised, together with the use of a solution of sodium carbonate ; the latter preventing the coagulation of the blood. Later a drum or hymograph was added to the apparatus, on which a record could be made for study and preservation (Fig. 166). The legend beneath the illustration is sufficiently descriptive of the complete apparatus. The curve Fig. 167. — The trace of arterial blood-pressure from a dog anesthetized with morphia and ether. The cannula was in the proximal stump of the common carot- id artery. The curve is to be read from left to right: P, the pressure-trace ^-ritten by the recording mercurial manometer: B L. the base-line or abscissa, representing the pressure of the atmosphere. Tlie distance between the base-line and the press- nre-cnrve varies, in the original trace, between 62 and 77 millimeters, therefore the pressure varies between 124 and 1.54 millimeters of mercury, less a small correction for the weight of the sodium-carbonate solution: T. the time-trace, made up of intervals of two seconds each, and written by an electro-magnetic chronograph (Curtis). made by the pen is shown in Fig. 1()7. The longer waves are due to respiration, the smaller ones to the heart-beat. By the term mean pre.^'^-irre is meant the average pressure throughout the observation. The mean aortic pressure in man is approximately 200 mm., an increase of 5 mm. occurring at the time of systole. The figures here given for the mean aortic pressure may be too high ; it has, of course, never been measured in man. The following table (Starling) gives the approximate heights in differ- ent portions of the vascuhir system, calculated largely from obser- vations in lower animals : Large arteries (e. g., carotid) — 140 mm. of mercury. Medium arteries (c. q., radial) ^- 110 •' •' Capillaries . . . .' + 15 to — 20 " Small veins of arm -f- 9 " " Portal vein - 10 " Inferior vena cava -j- 3 " " Large veins of neck from to — 8 " " BLOOD-PRESSURE. ;iii The Sphygmometer (Fig. 108). — Tho sphypmometor is an iiistniinent tor ascertaining the blftod-prc.-snre in tlir- lininan suhjoot. It consists of" a ruhhcr l)ag, containing a colored fluid, connected witli a graduated glass tube, the top of which i.s expanclcd into a bid!) and clos<'d with a stopcock. The instru- ment is so attached to the body that the rul)ber bag is on the artery whose l)lood-j)ressure is to be ascertained. The bag being pressed down upon the artery, the fluid rises in the tui;e, and the air in the bulb, ix-ing compressed, acts as an elastic spring. The top of the fluid is watched carefully, and when its pulsation is greatest, which is known as the maximal pulsation, its lieight is read otf on the scale ; this is so graduated as to correspond to millimeters of mercury pressure. an ^^ jz^ j\\ // T is at the time of the systole. \ \ s ^ J \\ -J^ / The Stromuhr. — One of the in- "^ ' "^ struments used to determine the rate of speed is the stromuhr of Ludwig (Fig. 169). This consists of a U-shaped tube, glass above and metal below, expanded into two bulbs, A and B, Mhich can be filled from the top. The lower extremities of these tubes are con- nected with the ends of a divided artery, so that the channel between the two is continuous through the stromuhr. The instrument is so constructed that while in place the upper portion, including the bulbs, can be so rotated at c as to bring A in eonnection with b, and B with a, and this process repeated as often as desired, the flow through the instrument not being interrupted. The tubes and the bulb B are filled with defibrinatcd blood, which in A reaches only up to the mark e ; and the bulb A is filled with oil. The clamps which close the ends of the vessel are now removed, the time being noted, and the blood from a expels the oil in A into B. When A is filled with blood to the point r/, the time is again noted, and the capacity of A, and the caliber of the vessel ^ a Fig. 169. — Diai^'rain of longitudi- nal section of Ludwig's ■"stromuhr."' The arrows mark the direction of the blood-stream. For further descrip- tion seethe text (Curtis). RATE OF BLOOD-FLOW l.\ Till-: VESSELS. 313 beini; known, the velocity of the How nuiy be calculated, A sinole measurement would not be sufficient to give results of niucii value ; but it' at the moment the blood reaches d the instru- ment is rotated, the Inilb B into which the oil has been driven l)y the blood will be brought into relation with a, and will be filled with i)lood from the vessel, as A originally was, the oil being forced into A, antl the blood contained in that bull) will be driven on into the vessel b, thus entering the circulation again. When the oil emerging from the bulb reaches the mark, the time is again noted, and the bulb again rotated ; thus the blood which is meas- ured is always the volume be- tween c and (/ in A. The time between the rotations is the time occupied in tilling the bulb, and this may be recorded on a kymo- graph. The Dromograph (Fig. 170). — This consists of a metal tube, which is inserted into a divided artery ; in the side of the tube is an opening, closed by rubber, through which a lever passes, one end being inside the vessel, the other outside, and so ar- ranged that its movements are indicated on a dial. The num- ber of graduations corresponding to a given velocity is known by brane, m, through which a "lever, C, observing the deflection of the lever when it is inserted into a rubber tube through which water flowing at a known rate is pass- Various observations have been made on lower animals to determine the velocity of the blood-flow in the arteries. In the dog's carotid it is found to be from 205 mm. to 350 mm. per second ; in the same vessel of a horse, 306 mm. ; and in the metatarsal artery of the horse, 56 mm. When an artery divides, the sectional area of the branches is more than that of the original vessel, and this consequently results in a gradually in- creasing sectional area, and a corresponding diminution in the velocity of the flow, so that in the smaller artery the speed is greatly reduced. The velocitv in the large arteries may be con- sidered as approximately 3 dcm. a second. Rate of Flow in the Capillaries. — The sectional area of the capillaries is 700 times greater than that of the aorta, where Fig. 170. — Chauveau's dromograph: A, tube connected with blood-vessel; B, metal cylinder in communication with A. The upper end of B has a hole in the center, which is covered bv a mem- passes ; C has a small disk, p, at its lower end, which projects into the lumen of A, and is deflected in the direction of the blood -stream through A. The deflection is registei-ed by a recording tambour in communication by the tube E with a tambour D, the flexible membrane of which is connected with the lever of the i)endulum C. 314 CIRCULATORY SYSTEM. the velocity is, perhaps, oOO mm. per second ; %vhen this portion of tlie circulatory apparatus is reached the rate of flow is greatly reduced, being in the dog from 0.5 mm. to 0.75 mm. per second. The rate of flow throngli the capillaries of the retina has been ascertained bv Vierordt in his own eye to be from 0.6 mm. to 0.9 mm. per second. The length lood receives from the tissues their waste products. The thin walls of the capillaries are admiral)ly adapted for this interchange. In fact, it is within bounds to say that the heart, the arteries, and the veins are simply subsidiary to the capillarif-s. the arteries carrying to these vessels the blood which tlie heart ])umps into them, while the veins return the blood to the heart. Rate of Flow in the Veins. — It is estimated that the sectional area of tlie veins i- at least t\\ ii<- as great as that of the arteries, and therefore the velocity would be twice as great in the arteries as in the veins. Some estimate the area of the veins as three times that of the arteries. Inasmuch as tlie sectional area of the veins decreases as the heart is approached, the rate of flow in these vessels gradually increases. The Circtllation-time. — The length of time which the blood takes to make the fiitire round of the body was first ascer- tained V)y dividing the jtigular vein and injecting a solution of potassium ferrocvanid into the end nearest the heart ; the blood was collected from the vein of the other side and tested by adding a solution of ferric chlorid to the serum ; as soon as the Prussian- blue reaction appeared it was demonstrated that the blood had completed the circulation of the body. These observations con- ducted on different animals gave the fiillowing results : In the horse, 31 seconds; dog, 16 seconds; cat, 6.5 seconds; fowl, 5 seconds. It was also found that this represented the time occupied by 27 heart-beats in each animal. If 72 times a minute are considered as representing the average number of beats in man, it will be seen that the Ijlood requires 23.2 .seconds to complete the entire circula- tion. Stewart has devi.sed a method for ascertaining the circulation- time by injecting into the ves.sels methylene-blue, the color of which shows through the blood-vessels. By this means he has been aide to studv the circidation-tinie in thr* Inno-s. kidnev. stom- THE PULSE. ;515 acli, and otlitT <)rj»;ans of lower animals. He tiiinks that the piilnionarv circulatioii-tiint' — /. /■., the time occupied hv the hlood in passing through the })ulmonary circulation — is not usually much less than 12 seconds nor more than 15 seconds ; the circulation-time of the kidney, spleen, and liver is relatively long and much more varial)le tiian that of liie lungs, these organs being easilv afi'eeted hy exposure and changes of temperature (increased by cold, diminished by warmth), and that of the retina and heart is the shortest of all. The total circulation-time in man he thinks is not much less than a minute, nor more than a minute and a quarter. THE PULSE, As has been seen, the left ventricle expels at each beat about 100 c.c. of blood, pumping it into the elastic arteries ; these being already filled, are still further distended by this additional amount, and the elastic coat of the artery recoils upon the blood within the vessel, driving it still further along. If a finger is placed upon an artery, this distention ca« be recognized, and constitutes the pulse. AVhen the ventricle ceases its systole and begins its diastole, although blood ceases to be expelled from it, still the current in the arteries does not cease, for the elastic force of the vessels is sufficient to keep up a continuous movement of the fluid, which while it is in the arterial system is affected by the pulsation of the heart, but which in the capillary and venous systems, is uniform in rate. If it was possible to place a finger upon the carotid, another on the radial, and still another on the dorsal artery of the foot, it would be found that the pulse would first be felt in the artery nearest the heart, then in that at the wrist, and finally in the most distant one. Thus the pulse-wave starting at the left ventricle is felt in 0.159 second at the wrist, and in 0.193 second at the foot. It travels at the rate of about 9 meters per second. Any artery which is accessible may be used to obtain the pulse, but physicians have selected the radial as the most convenient be- cause of its accessibility and also because it lies upon an unyield- ing bonv bed, and can be readilv compressed by the finger and its character studied. The heart is one of the vital organs of the body, and a knowledge as to how it is performing its functions is very important for the physician to possess. Situated as it is within the thorax, he cannot examine it directly, and is therefore compelled to resort to other means to ascertain its condition. One of the best sources of information is the ]:)ulse. This he studies to learn : (1) The frequency of the heart-beats, for each time the ventricle contracts there is a corresponding beat of the pulse ; (2) the /o/'c<' with which the heart is acting, for the strength of the pulse is an indication of that of the heart : f3) its ref/ularifi/ ; and (4) its tension — i. e., whether it is compressible or not, whether a 316 CIRCULATORY SYSTEM. t sliglit pressure will obliterate it, or whether it requires a greater amount of pressure. Low tension implies low arterial pressure, and high pressure denotes high blood-pressure. Fig. 171. — Scheme of Marey's sphygmograph : a, toothed wheel connected with axle h, and gearing into toothed upright 6 ; c, ivory pad which rests over blood- vessel and is pressed on it by moving g. a screw passing through the spring j ; e, writing-lever attached to axle h, and moved by its rotation ; e writes on d, a travel- ling surface moved by clockwork /. The Sphygfmograph (Fig. 171). — This instrument makes a record, fiphifinogram or pulse-trace, of the pressure in the Fig. 172. — Sphygmogram from a normal human radial pulse beating from 58 to 60 times a minute. To be read from left to right (Burdon-Sanderson). arteries. It is attached to the wrist, and the point of the lever makes a sphygmogram upon the card previously smoked. It II 1 125 1 1 1 B c D a a r Fig. 173. — Pulse-tracings : 1, primary elevation ; 2, predicrotic or first tidal wave ; 3. dicrotic wave. The depression between 2 and 3 is the dicrotic or aortic notch : 3 is better marked in B than in ,-1. C. dicrotic pulse with low arterial pressure. D. pulse with high arterial pressure-summit of primary elevation in the form of an ascending plateau. E. systolic anacrotic pulse ; the secondary wavelet a occurs during the upstroke corresponding to the ventricular systole. F, presystolic ana- crotic pulse; a occurs just before the systole of the ventricle. In this rarer form of anacrotism a may sometimes be due to the auricular systole when the aortic valves are incompetent (Stewart). is an instrument which needs great care in its use in order to make its records of practical value. Fig. 172 shows a sphygmo- gram of the radial pulse. It represents five complete pulsa- riiK PULSE. 317 tions of the artery and the heginninj^ of a sixth. The upstroke is caused by the expansion of the artery due to the arrival of tlie pulse-wave, while the dowustroke is due to the retraction of the vessel. The upstroke, the priinarj/ or percuxulou-icdrr, is altrupt, because the systole of the left ventricle is abrupt, but the down- FiG. 174. — Plethysniograph for arm: F, float attached by a to a lever which records variations of level of the water in b, and therefore variations in the vol- ume of the arm in the glass vessel c. Or the plethysnuigraph may be connected to a recording tambour. The tnbulure at the upper part of c is closed when the tracing is being taken (Stewart). stroke is oradual, because of the fact that the return of the artery to its former condition is gradual by virtue of its elas- ticity. The dowustroke is seen to be made up of a number of waves : First, the predicrotic or tkhil wave ; second, the dicrotic wave ; and third, the post-dici-otic wave. These sec- FiG. 175. — Plethysmograph tracing from arm. The tracing was taken by means of a tambour connected with the plethysmograph ; the dicrotic wave is distinctly marked (Stewart). ondary waves of the dowustroke are termed katacvotic. There is sometimes a secondary wave in the upstroke, called anacrotic. The predicrotic and post-dicrotic waves are supposed to be due to the elastic tension of the arteries, and are therefore more marked when this is at its highest. They are also caused to some extent by oscillation of the sphygmograph. Their causes are not thoroughly understood. 318 CIRCULATORY SYSTEM. The dicrotic wave is, on the other hand, a very constant and vahiable feature of the sphygmogram. It is probably caused by a second wave, ^vhich is produced by the closure of the aortic valve, although on tiiis point opinions are at variance. The arteries are already filled when the left ventricle throws in its contents, causing the expansion of the aorta and putting its elastic coat upon the stretch ; when the systole is at an end the elastic recoil upon the blood drives this fluid both forward and backward ; the backward flow closes the aortic valve, and, being suddenly brought to a standstill, a wave of blood is produced which is propagated along the arterial system closely following the pri- mary wave and causing the dicrotic wave. This is sometimes so marked that it (^an be felt by the finger, constituting the dicrotic pulse; thus each pulsation of the heart })roduces 2 pulse-beats. The sphygmograph shows this condition much better than the finger. The Plethysmograph (Fig. 174). — This is an instrument for recording the volume-pidse — i. e., the increase in the volume of an artery caused by the pulse-wave. It consists of a chamber into which the organ to be experimented upon is inserted and filled with fluid, the opening being closed witii a rubber band. At tiie other end is a rubber tube commimicating with a vessel, in wiiich is also fluid, and on its surface a float with a writing-point attached, which is so arranged as to record on a drum. If the arm is placed in the chamber in the manner illustrated, at every contrac- tion of the ventricle tiie volume of blood in the arteries will be increased, and a movement be set up in the fluid which will cause the float to rise ; when the diastole occurs the float will sink. The record made is called a plethysmogram (Fig. 175). CIRCULATION IN THE VEINS. The forces which ])ropel the blood through the arteries and capillaries — /. e., the contractile force of the ventricles and the elastic force of the arteries, collectively called the vis a tergo — are sufficient to carry the blood back to the heart through the veins ; for, as has been stated, the pressure in the aorta is equal to a column of mercury 200 mm. in height, while in the veins it is at most only 5 mm., and sometimes actually negative, so that there is a difference in ]>ressure of 195 mm. of mercury. This v/sa tergo is, however, aided by two other forces : (1) compression of the veins and (2) aspiration of the thorax. Compression of the Veins.— It will be remembered that in the veins there are, at different points along their course, valves which are so arranged as to permit the blood to flow in but one direction — that is, toward the heart. Many of these veins are so situated with reference to muscles that when the muscles contract LYMPHATIC VESSELS. 'MO the contiguous veins arc compressed. This compression forces the contained blood away from the j)()iiit.s of pressure, and as the closure of the valves ])reveuts the blood from Howing backward, it must i^o Ibrward. Aspiration of the Thorax. — At each inspiration the cavity of the chest is enlarged and the pressure on its contents is dimin- ished. One of the results of this inspiration is the inflowing of air. Another result is the inflowing of blood into the vena? cavie and right auricle, for while the intrathoracic })ressure is dimin- ished, that upon the blood-vessels outside remains the same. A similar tendency exists for the blood in the aorta to flow back into the left ventricle, but this is prevented by the aortic valve. This subject will be again discussed in connection with respiration. Force of Gravity. — The force of gravity assists in the retmni of the blood to the heart from the upper portions of the body, but retards its return from the lower portions, so that as a factor in aiding the circulation as a whole it may be ignored. This force may, however, be utilized whenever for any reason there is congestion in a part — as, for instance, in a foot the seat of inflam- mation. In such a case the elevation of the lower extremity facilitates the flow of l)lood in the veins and proves beneficial. Also, when by reason of an imperfect pei-formance of its function the heart fails to send enough blood to the brain, and fainting occurs, relief will come more promptly if the patient is at once placed on the back, with the head low^er than the heart, thus assisting that organ in sending blood to the anemic brain. LYMPHATIC SYSTEM. The lymphatic system is composed of lymphatie vessels, lymphatic glmuh, and the cavities of the serous membranes. I/3rmphatic Vessels. — The larger lymphatic vessels struct- urally are like the veins, being composed of three coats, the middle coat containing both muscular and elastic fibers. Unlike the veins, however, muscular fibers are found in the external coat. The smaller vessels have only a connective-tissue coat lined with endothelium. In the lymphatic vessels, as in the veins, are valves opening toward the heart, but they are nearer together than are those of the venous system. The origin of these vessels in the tissues, as a rule, is by plexuses or by stomata, as in serous mem- branes ; by blind extremities, as in the lacteals ; or by lacunar interstices, as in some viscera and glands. They ultimately dis- charge into the venous system — on the right side through the right lymphatic duct, and on the left side through the tlu^racic duct. , Right Lymphatic Duct. — The lymphatic vessels of the right side of the head, neck and thorax, and of the right arm. 320 /. YMI'IIA TIC SYSTEM. right lung, right side of" the heart, and a portion of the convex surface of the liver, discharge into the rigid lymphatic duct, which in turn discharges into the right sul)clavian vein, at its junction with the right internal jugular vein. It is about 1.25 cm. in length and about 2 mm. in diameter. At its junction with the venous system there are two semilunar valves, to })revent regurgi- tation of the hlood. Thoracic Duct. — All the lymj)hatics not connected with tlie right lymphatic duct discharge into the thoracic duct. This vessel Scalenus anticus. Brachial plexus. Superficial cer- vical vein. Axillary lym- phatic trunk. Esophagus ////K ViTtebral vein. Fig. 176. — Topography of the thoracic duct (Zuckerkandl) begins at tlie recfptacidum chyli or reservoir or cistern of Pecquet, which is situated upon the body of the second lumbar vertebra, and terminates in the left subclavian vein, where it joins the left internal jugular vein. The duct is from 38 cm. to 45 cm. long, about the .se cells are openings — domata — which are surrounded by small protoplasmic cells. They are very distinct in the peritoneal covering of the rabbit's diaphragm. The stomata are openings into the lymphatic vessels through which lymph is pumj^ed by the contraction and dilatation of the serous cavities, brought about by respiration and circulation. The serous membranes are: (1) peritoneum ; (2) pleura; (3) CIRCULATING LYMPH. 323 pericardium, which on account of its fibrous layer is termed jibro- serous ; (4) tunica vaginalis testis. CIRCULATING LYMPH. The h'lnph and its source having been discussed (p. 292), need not again be referred to. It is taken up by the lynipiiatic capil- laries in the tissues by endosmosis, and, as it accumulates there, gradually fills the larger vessels, and, as it is readily discharged into the venous system, there is set up a current which constitutes the lymphatic circulation. It is to be noted, however, that tliere is no true circulation, as in the case of the blood. The blood goes out from the heart and returns again, completing a circuit, but here the flow is always in one direction, toward the heart. Additional aids to the endosmotic force in producing the move- ment of the lymph are the contractions of the muscles of the body, by which, as in the veins, the lymphatics are compressed, and the lymph, being prevented by the valves from flowing back, is pro- pelled toward the heart. The pressure exerted by the walls of the aorta in its pulsations compresses the thoracic duct in a similar manner, and, as this possesses valves, the onflow of the lymph and chyle is favored. The force of aspiration of the thorax is Ftg. 179. — Endothelial cells from small artery of the mesentery of a rabbit : stained with silver nitrate and hematoxylin (Huber). also a factor in the movement of the lymph, acting as was stated in the case of the venous blood. It has been estimated that the amount of lymph absorbed daily in a human adult is about 2000 grams, and of lymph and chyle together 3000 grams. DUCTLESS GLANDS. This term includes the spleen, the thyroid and parathyroids, the thymus, the suprarenal cajxsules, the pineal gland, the pituitary body, the carotid and coccygeal glands, and the lymphatic glands, the last of which we have already considered. They have re- ceived this name because they lack secretory ducts. For the reason that they are believed by some to have important relations to the blood they are sometimes described as blood-glands or vas- cular glands. We have seen that although the lymphatic glands have no 324 DUCTLESS GLANDS. proper duct, still there are added to the lymph during its passage through the glands the lymphocytes, which are a product of the gland, and it is now held that in a similar manner while the blood is passing through the ductless glands their product is added to it. This product is regarded as an internal secretion. THE SPLEEN. The spleen is the largest of the ductless glands, tion is, doubtless, the most important. Its location and its func- is in the left Blood-vessel. Trabecula. -Spleen pulp. Artery. Malpighiau cor- puscle with germ center. v^«^..-,. 'fr-"i J^ Fig. 180.— Part of a section through the human spleen : X 75 (sublimate fixation). At a is an oblong Malpighian body with a blood-vessel (Bohm and Davidoflf). hypochondrium between the stomach and diaphragm. Instances are on record in which the organ was absent, while sometimes it is so divided as to present the appearance of a considerable number c»f small spleens. Weight. — The weight of the spleen varies at different periods of life, being at birth to the entire body as 1 is to 350 ; in adult life, as 1 to 320 and 400 ; and in old age, as 1 to 700, while in THE SPLEEN. 325 certain diseased conditions, such as ague, syphilis, or heart disease, it niav be cnuriuoiisly increased, in some eases as much as 1 to 7, or 9 kilograms, the average normal weight being about 17(j grams in the cadaver, or abont 225 grams during life, on account of" the contained blood. Its color is dark red. The size of the spleen is greatest during digestion, and least during starvation. Chemical Composition. — The spleen consists of about 75 per c-cnt. wattr and 25 jxt cent, solids, of Avhich only about 1 per cent, is inorganic, a part l)eing iron. The organic ingredients are proteids, among them being a cell-globulin and a nucleo- proteid ; whether peptones exist or not is still undecided ; hemo- globin, xanthin, uric acid, glycogen, cholesterin, lecithin, and the fatty acids, formic, acetic, and butyric. The reaction of the gland Intralobular trabec ula. Artery to one of the- ten compartments. Intralobular arterv Interlobular trabec- - ula. Intralobular trabec- ula. Malpighian cor- puscle. Capsule. Intralobular venous spaces. Intralobular vein. Ampulla of Thoma. Spleen pulp cord. Interlobular vein. Intralobular vein. Fig. 181. — Diagram of lobule of the spleen (Mall, Johns Hopldns Hospital Bulletin, Sept., Oct., 1898). is alkaline during life, becoming acid after death, due to the forma- tion of sarcolactic acid. Structure. — The outer covering is peritoneal, and is closely adherent to the tibro-elastic coat or tunica propria, the two form- ing practically one. From it are given off trabeculcp, which form the framework of the organ, in the interspaces of which, areolce, is the splenic pulp, a soft material with a reddish-brown color, within which are whitLsh bodies, MalpAghian corpuscles (Figs. 180, 181), composed of lymphoid tissue, and having a diameter of from ^ mm. to 1 ram. The spleen-pulp, when examined under the micro-scope, is seen to be made up of connective-tissue corpuscles, the sustentacular cells, from which are given off processes that form by their union a network in the areolae of which is blood, characterized by a large number of white corpuscles. The 326 DUCTLESS GLANDS. sustentacular cells possess ameboid movement, and in some of them reddish granules, resembling hematin, are seen ; also red cor- puscles in various stages of disintegration. In young spleens Klein has seen these cells each with a large nucleus from which project bud-like processes, and it has been suggested that these are possilily white corpuscles in the process of formation. The splenic artery enters the spleen at the hilum, after having divided into a number of branches (Fig. 181) and being covered by sheaths from the fibro-elastic coat. These arteries divide and subdivide and finally end in the pulp in small arterioles, their external coat gradually changing from connective tissue to lymphoid tissue in which enlargements occur the Malpighian corpuscles. These consist of a delicate reticulum enclosing lymph- corpuscles. The cells which make up the reticulum possess ame- boid movement. The arterioles end in capillaries, which later cease to be distinct vessels, the cells making up their walls becoming branched and the branches uniting with the processes of the sustentacular cells. The blood which reaches the pulp through these vessels is by this means brought into direct relation with it. It is again collected into vessels which ultimately become veins that emerge from the hilura as the splenic vein. Innervation of the Spleen — The nerves which are dis- tributed to the spleen are derived from the celiac plexus and right vagus. Functions. — The spleen has been frequently removed in lower animals without producing fatal results : indeed, without producing marked symptoms of any kind. In these instances, according to some authorities the size of the lymphatic glands was increased, also that of the marrow of bones ; but this increase has not been observed by others. The spleen has also been re- moved from human beings. On this point Gray, in his Anatomy, says : " Extirpation of tlie spleen has been performed for wounds or injuries, in floating spleen, in simple hypertrophy, and in leukemic enlargement ; but in these latter cases the operation is now regarded as unjustifiable, as every case in which it has been performed has terminated fatally." One of the most striking phenomena presented by the spleen is the change in size which occurs during digestion. This begins after a meal has been taken, and continues for about five hours, when the maximum is reached, after which its decrease begins. This has been supposed to indicate that the spleen serves as a reservoir for the blood which is needed during the time of digestion, and especially for that taking place in the stomach. The enlargement is caused by relaxation of its muscular tissue and a dilatation of the blood-vessels. A peculiar movement of contraction and expansion has been THE SPLEEN. 327 found l)v Roy to occur in tliis organ at intervals ot" about a minute. This lie (Icinonstrated by tlie use ot" an oncomdcr (Fig. l.S2i. The principle on whieh this is constructed is the same as that of the plethysmograph (p. 318). It is a metal box made up of two halves, fitted together in such manner that they can be tightlv closed, oj^eniugs being left for the vessels of the organ which is enclosed, be it spleen or kidney. To each half is attached a membrane between which and tjie metal is a space tilled with oil. Any increase in the size of the contained organ is accom- panied by an expulsion of the oil, which returns when the organ becomes smaller. These changes are recorded by the oncograph. AVhile the functions of the spleen have not as yet been satis- factorilv determined, still they are doubtless comprehended in the various theories which have from time to time been formulated. Fig. 182. — Kuy's oncometer for spleen : .4, open ; /?, closed. (1) It is a producer of white blood-corpuscles. As to this func- tion there is great unanimity of opinion. The blood emerging by the splenic vein contains more of these cells than that which enters the gland, and this number is greatly increased in leiiko- cythemia or leukemia, in which the spleen and the ]Malpighian cor- puscles especially are hypertrophied. This disease may also be due to affections of other organs, as the bone-marrow and lymphatics. (2) It destroys red blood-corpuscles. This theory is based upon the fact that red blood-cells are found in the pulp in different degrees of disintegration, and this is supposed to be brought about by the ameboid cells hitherto described (p. 325). It is stated that in the cells of the spleen hemoglobin is found in different degrees of transformation into other pigments, and a considerable amount of iron is also found in the splenic tissue. It is rather remarkable 328 DUCTLESS GLANDS. that if hemoglobin is set free or changeJ into bile-pigment, one or the other of these substances is not found in the blood of the splenic vein, and yet this is the fact. (3) It is a producer of red blood-corpuscles. The formation of red blood-corpuscles does, doubtless, take place during fetal life and for a short time after birth in man, but there is no evidence that this function exists in the human adult, though it does in some animals, as the rabbit. Laudenbach found that in this animal after an extensive hemorrhage nucleated erytlkrohhists or hematoblasts are found in the splenic pulp and in the blood of the splenic vein, and that if the spleen is removed the number of red corpuscles is diminished, as is also the hemoglobin. In an animal Avhose spleen has been removed the return of the red corpuscles to their normal number is much delayed. (4) It is a producer of uric acid. From the fact that uric acid, as also xanthin, has been found in the spleen, it has been inferred that this is one of its functions. The same is true of lymphoid tissue generally, so that this function cannot be considered as one of the characteristic functions of the spleen. (5) It is an enzyme producer. Some experimenters have found that an enzyme is produced by the spleen ^vhich Avhen carried by the blood to the pancreas converts the trypsinogen into trypsin. This theory lacks confirmation. • Schiifer sums up his views on the functions of this organ in the following language : " Whatever may be the nature of its functions in relation to the l)lo()d, it is certain that the organ is in no way essential to the normal nutrition of the body. It is, on the other hand, not at all improbable that tlie main function of the spleen is to serve a mechanical purpose, answering as a reservoir at certain periods of digestion for the bk)od which has to pass through the portal system ; and the fact that, as was first shown by Rov, the spleen normally exliibits regular rhythmic contrac- tions and dilatations, seems to point to its exercising an influence in assisting the flow of blood through the portal vein, and thus through the liver." THE THYROID AND PARATHYROID. The thyroid gland is also called the thyroid body ; it is situated in front of the trachea or windpipe, and consists of the lobes united by an isthmus. It weighs from 30 to 60 grams, and is larger in females than males, and is said to be larger during men- struation. Chemical Composition. — An analysis of an adult thyroid gives a percentage of 82.24 of water, 17.66 of organic, and 0.1 of inorganic constituents ; in that of an infant the figures were, 77.21, 22.35, and 0.44 respectively. Like the spleen, it is alkaline THE THY no ID AND PARATJIYJiOfl). 329 (luring life and acid :i1'Ut death, the acidity being due to the same eauso — the formation of sareohictic acid. Fatty acids, xantliiii, hvpoxanthin, and other extractives have also been obtained from it. The constituents which possess the greatest importance are those of a proteid nature, for upon them it is believed depend some of the remarkable powers with which this gland is endowed. Among these arc thyrcoprotcid and thy r co-antitoxin {Q^\^yS-f)^. A substance has also been found in the thyroid, principally com- bined with a ]>r(^teid, although also free, called thyro-iodin and iodo-fhyriii, containing 9.3 per cent, of iodin and 0.56 per cent, of ])hosphorus. TJie amount of iodin in each gram of the human adult thyroid varies from 0.3 to 0.9. Structure. — The thyroid has a capsule of connective tissue which sends off septa or trabeculce that enclose the thyroid vesicles Lumen of follicle. - Counective tissue. Epithelium of follicle. Fig. 183. — From section through thyroid gland of child (Bohm and Davidoflf). (Fig. 183), each of which is lined by cubical epithelium and con- tains viscid, colloid liquid, yellowish in color, which is coagulated by alcohol and stained with hematoxylin, and is doubtless secreted by these cells. Red blood-corpuscles in various stages of disinte- gration and white corpuscles are also found in these vesicles. The color of the colloid material is probably due to hemoglobin. Around the vesicles is a plexus of capillary blood-vessels, which is also found between the vesicular epithelium and the endothelium of the lymph-spaces, which latter surround the vesi- cles and communi(!ate witli lympliatic vessels. Colloid material, identical with that contained in the vesicles, has been found in the lymphatics. The arteries which supply the thyroid body are the superior 330 DUCTLESS GLANDS. and inferior thyroid, and sometimes the thyroidea media or ima, an occasional branch of" the innominate or aorta. The nerves are from the middle and inferior cervical ganglia of the sympathetic. Functions. — In recent years the physiology of the thyroid body lias received a great deal of attention, and important addi- tions have been made to the knowledge of its function by a study of (1) the effects of its disease and (2) of its removal. Cretinism. — In some parts of Switzerland and elsewhere on the Continent there exists a disease characterized by a swelling of the thyroid, termed goiter, together with "stunted growth, swelled abdomen, wrinkled skin, wan complexion, vacant and stupid countenance, misshapen cranium, idiocy, and comparative insensi- bility." This disease is cretinism, and those suffering from it are cretins. This condition is accompanied by disease of the thyroid, as manifested by the goiter. Myxedema. — A similar condition is sometimes seen in which the striking characteristic is the appearance of the skin, which resembles edema; and the material which is deposited in the con- nective tissue was thought to be mucin, hence the name myxedema. Although there is more mucin than in ordinary connective tissue, still the material here is not altogether mucin, nor is it true edema — /. e., a dropsical effusion into the cellular tissue — but a hyper- plastic and modified connective tissue. In addition to this condi- tion of the skin there is also a slowness of gait, an apathy of mind, and sometimes tremors and twitchings of muscles. Operative Myxedema. — AVhen the thyroid gland becomes enlarged, this may be due to a hypertrophy of the vesicles, paren- chymatous goiter, or of the connective tissue, fibroid goiter ; or the vesicles may form cysts, cystic goiter, or the blood-vessels may be dilated, pulsating goiter, or the vessels may be enlarged, and with this a prominence of the eyes, palpitation of the heart, and a quick pulse, exophthalmic goiter or Graves's disease. For goiter, one of the methods of treatment is the removal of the gland ; when this is practised, a condition of myxedema results, operative myxedema. The removal of the thyroid, thyroidectomy, has been performed upon dogs with a fatal result in all cases, occurring so soon after the operation — within fourteen days — that the changes in the skin have no time to take place, but tremors, spasms, and convulsions occur. One remarkable fact was discovered by Schiff, who per- formed as many as sixty thyroidectomies on dogs — namely, that if a portion of a thyroid was, before the operation, grafted under the skin or into the peritoneal cavity, the symptoms described did not occur, and the animals did not die. Horsley removed the thyroid from monkeys, with the result of producing myxedema. It has been demonstrated, as already stated, that grafting a thyroid or part of it into an animal before the removal of its THE THYROID AND rARATHYROW. 331 thvn.ia will prevent the niyxeclematous symptoms. It is interest- inL^ to know that if, later, this graft is removed, the symptoms w.l th?n .u,)ervene. Injeetions of an extract of the thyroid gland and also feeding the gland itself are followed hy the same results as the trrafting ]>rocess. i ^ i • Thcn-e are two the.)ries which have been advanced to explain the results of removal of the thyroid: (1) autotoxication and (2) internal secretion. , , ,, ^ • .,k Aidotoxication.-T\vis theory supposes that there are toxic sub- stances normallv in the blood which, being removed or rendered harmless bv the' thvroid, accumulate when that organ is removed and produce the effects that follow thyroidectomy. In support of this, it is stated that the urine of animals operated on is more toxic than that of unoperated animals, and that their blood is also toxic for others. , ^ ^i i. ^.u ^„^ Internal Secretion.-We have already seen that the pan- creas, in addition to the pancreatic juice, which is its external secreiion, also produces an internal secretion. Phis is also be- lieved to be true of the thyroid, and it is this secretion which is taken up by the blood or the lymph in its passage through the crland and carried to the tissues, where it is, in some way not under- 'stood, connected with their metabolic processes. From the dis- turbances in the nervous system and connective tissues which occur on ablation of the gland, it is probably especially re ated to their metabolism. When, therefore, after extirpation of the thyroid or in cases of mvxedema where the gland is diseased, iiyections ot the extract or injections of the gland itself are followed by benehcial results it is, doubtless, due to the introduction into the blood ot this interna'l secretion. It is also possible that some of the toxic products of metabolism mav be destroyed by the gland or its secretion. Several observers have maintained that the thvroid was inti- matelv connected with the regulation of the supply of blood to the head, and have reasoned thus from its great vascularity and direct connection with the blood-vessels of the head ; and Cyon has demonstrated that the nerves supplying the thyroid when stimu- lated lower the blood-pressure in the carotid, by virtue ot vaso- dilators, which are contained in the trunks of the nerves, ihese nerves are called into action when the cut ends of the vagi, ot the depressors, or of the cardiac branches of the recurrent laryngeal nerves are stimulated. ^ -^ «• ^.^ To which of the constituents of the thyroid extract its effects are due is still a mooted question. Indeed, the most recent researches seem to indicate that the gland forms more than one substance, each one having its own action ; thus there seems to be no doubt that both iodothvrin and thyreo-antitoxin are produced although at the present time the iodothyrin seems to be regarded as the most active ingredient. 332 DUCTLESS GLANDS. Thyroid extract has also been recommended as a means of treating obesity, on the ground that it increases metabolism ; there is undoubtedly a diminution of fat in its use. The thyroid gland has been used in the treatment of goiter, myxedema, etc., in various ways. Thus Schiff'and Esselsberg, in 1884, made grafts both in the abdominal cavity and in the cellular tissue. Birch, on the advice of Horsley, transplanted the thyroid of a sheep into the peritoneal cavity of a woman suffering with myxedema. For a time she was benefited, but the gland was absorbeituitary body. Dr. Kinnicutt states that in 84 rc(;orded cases of acromegaly, with full auto])sy, a microscopic lesion of the pituitary body has been found in every instance, and in the majority of cases it has proved to be either a simple hyperplasia or a tumor growth of some kind. Others have not found these k\sions in cases of enlargement of the gland, but rather a persistence of the thymus. There seems to be no valid reason for concluding that the thyroid and the pituitary body have any physioh)gic relation with each other. Injections of extracts of the pituitary body cause great increase in the force of the heart's beat, and also an increase in blood-pressure bv contracting the arterioles; that of the thyroid does neither. That the pituitary body furnishes an internal secretion seems to be beyond question, and this has the effect of increasing the contraction of the heart and arteries, and also of influencing the metabolism of the bones and nervous system, but just how this is brought about is not determined. THE CAROTID AND THE COCCYGEAL GLANDS. The caroiid gland is situated at the bifurcation of the common carotid artery, and the coccygeal gland or Luschka's gland is situated in front of the tip of the coccyx, just above the attachment of the sphincter aui. These glands are collections of small arteries enclosed in granular polyhedral cells, the whole being enclosed in a capsule. Into the coccygeal gland sympathetic nerves pass. IMacalister regards it as consisting of " the condensed and con- voluted metameric dorsal arteries of the caudal segments embedded in tissue which is possibly a small persisting fragment of the neurenteric canal." The function of these glands is unknown, if, indeed, they possess any. RESPIRATION. One of the most important processes carried on in the body is that by wdiich the tissues receive oxygen. In animals whose structure is exceedingly simple, and so constituted that all portions of their bodies are bathed by the oxygen-carrying medium, the oxygen is directly absorbed ; but in those in which there are tissues remotely situated as regards this medium, some provision must be made for conveying the oxygen from the medium to the 342 RESPIRATION. tissues. This condition exists in man, many of whose tissues are so deeply situated tiiat witliout such provision the maintenance of life would be imijossihle. In man this medium is the blood. But additional provision must be made for the renewal of the oxygen abstracted by the tissues. That part of the process by whicli the tissues take oxygen from the blood is i titer nal respiration, and that part by which the renewal is accomplished is external respiration. Ordinarily, when respiration is spoken of without qualification it is external respiration that is referred to. Respiratory Apparatus. — The group of organs concerned in external respiration is collectively spoken of as the re.'ipiratory ajjparatus, which consists of the nose, larynx, trachea, bronchi, lungs, and thorax. THE NOSE. The nose is the beginning of the air-passages, for although it is regarded by many as the organ of smell only, it has another function as well. The mouth belongs to the alimentary canal, and should be opened only to take in food or to speak, never to take in air. The proper channel for the admission of air is the nose, and the use of the mouth for this purpose is not physiologic. Indeed, man is said to be the only animal that breathes through the mouth. If the nursing child should attempt to use its mou^h for the admission of air to tlie lungs, sucking could not be performed without great difficulty, and after a few moments the child would be compelled to let go the breast in order not to suffocate. Mouth-breathing-. — There is no more pernicious habit, so far as health is concerned, than breathing through the mouth. If this is due to habit and to nothing else, it may be overcome ; but if, as is often the case, it is due to some diseased condition f)f the nose, or to the presence in the nasal cavities of tumors, or to the existence of enlarged tonsils, its relief can be accomplished only by surgical means. The function of the nose in respiration is to Avarm the air and to filter out from it dust and other extraneous matter which would otherwise enter the air-passages and cause irritation. When air is taken in by the mouth these beneficial results do not occur. Mouth-breathing causes dryness of the mouth and the pharvnx, which condition is very noticeable on awaking from sleep. The mucous membrane becomes congested and inflammation is likely to follow. A chronic inflammatory condition of the larvnx may also result from this cause, and the evidence is very conclusive that the hearing becomes affected in these cases. The deformity known as pigeon-breast is not an uncommon sequel. Indeed, the consequences of mouth-breathing are numerous, widespread, and serious, and the subject has never received the attention which its importance demands. THE LARYNX. 343 THE LARYNX. Tliis or) js situated at the upper part of the neck, behind and lK'h)\v the l)ase of tlie ton^^ue. It is composed of nine cartihiges, which are connected by ligaments. Cartilages. — These are tlie thyroid, cricoid, arytenoid (two), cornicHihi laryngis (two), cuneiform (two), and epiglottis. The thyroid is the largest of all the laryngeal cartilages, and the angle of its two aloe forms the prominence in the front of the throat, Adam's apple or pomuiii AdaiiiL Fig. 192. — Articulations and liga- ments of the larynx, anterior view : A, hyoid bone, with a its greater, and a' its lesser cornua ; 1-5, liga- ments ; 6, lateral cricothyroid artic- ulation ; 7, junction of cricoid and trachea (Testut). Fig. 193. — Articulations and ligaments of the larynx, posterior view : A, hyoid ; i?. thyroid, with b and b' its cornua; C, cri- coid ; D, arytenoids ; E, cartilages of San- torini ; F, epiglottis; G, trachea ; 1-6, liga- ments ; 2, opening for superior laryngeal artery; 7, junction of trachea and cricoid (Testut). The cricoid is ring-shaped. The arytenoids articulate with the cricoid cartilage, while to the summit of these are attached the comicula laryngis or cartilar/es of Saiitorini. Tiio cuneiform cartilages or cartifar/es of Wrisherg are tAvo small bodies, one in each fold of the mucous membrane extending from the apex of the arytenoid to the epiglottis, the aryteno-ejn- glottic fold. The epiglottis is behind the tongue, in front of the opening of the larynx. Its position is vertical during respiration, but during 344 RESPIRATION. a part of the act of deglutition it is carried backward and closes the laryngeal opening. The cartilages of the larynx are hyaline, except the cornicula laryngis, cuneiform, and epiglottis, which consist of yellow fibro- cartilage, and, being hyaline, do not become calcified. Muscles. — Of these tiiere are two sets — extrinsic, which arise outside the larynx, and intrinsic, which arise within the larynx and are also inserted wdthin it. Extrinsic Muscles. — These may be subdivided into the depressors and elevators and exist in pairs. The depressor muscles of the larynx and hyoid bone are : Sterno- hyoid, which arises from the clavicle and sternum, and is inserted into the hyoid bone ; sternothyroid, which arises from the sternum and cartilage of the first rib, and is inserted into the ala of the ikhOT^ Fig. 194. — Diagram to illustrate the thyro-arytenoid muscles; the figure repre- sents a transverse sectiou of tlie larynx through the bases of the arytenoid carti- lages: Ary, arytenoid cartilage ; p.m, processus muscularis ; p.r, processus vocalis; Th, thyroid cartilage; c.v, vocal cords; Oe is placed in the esophagus; m.thy.ar.i, internal thyro-arytenoid muscle; m.thy.ar.e, external thyro-arytenoid muscle; m.thy.ar.ep, part of the thyro-ary-epiglottic muscle, cut more or less transversely; m.ar.t, transverse arytenoid muscle (redrawn from Foster). thyroid cartilage; thyrohyoid, which appears like a continuation of the sternothyroid, and arises from the side of the thyroid and is inserted into the hyoid bone ; omohyoid, which arises from the upper border of the scapula and is inserted into the hyoid bone. The action of this group of muscles is to depress the larynx and hyoid ])one at the close of deglutition ; these structures having previously been drawn up with the pharynx. The omo- hyoid by carrying the hyoid backward, as well as depressing it, aids in ]>erforming the act of sucking. The thyrohyoid raises the thyroid cartilage as well as depresses the hyoid bone. The elevators of the larynx and hyoid bone are the digastric, which arises from the mastoid process of the temporal bone and from near the symphysis of the lower jaw, and is attached to the hyoid bone by a fibrous loop ; stylohyoid, which arises from the styloid process of the temjioral bone, and is inserted into the hyoid ; mylohyoid, which arises from the mylohyoid ridge of THE LARYNX. 345 10- tlu' IdWtT jaw, and is inserted into tlic hyoid b(Mie ; and genio- hi/uid, wliich arises from the inferior genial tuberele of the hjwer jaw, and is inserted into the hyoid bone. The action of this gronp of mnscles is to raise the iiyoid i>one and the hirynx during deglutition ; or if the hyoid bone is de- pressed and fixed, their eontrae- tion dej)resses the lower jaw. Intrinsic Muscles (Figs. 194, 195). — These are eight in num- ber : (1) Cricothyroid. — This mus- cle arises from the front and side of the cricoid cartilage, and is inserted into the lower border of the thyroid and the anterior border of the lower cornua. The action of the two muscles is to make tense and elongate the vocal cords. Their action will be better understood after a con- sideration of the thyrohyoid mus- cles. (2) Crico-ari/tenoideus Posti- cus. — It arises from the posterior surface of the cricoid, and is in- serted into the muscular process of the base of the arytenoid. The action of the two muscles is to ro- tate outward the arytenoid carti- lages, and thus separate and make tense the vocal cords and open the glottis. (3) Orico-arytenoideus Lat- eralis. — This muscle has its ori- gin from the upper l)order of the side of the cricoid cartilage, and is inserted into the mus- cular process of the arytenoid. The action of the pair of mus- cles is to rotate the arytenoid cartilages inward, approximating the vocal cords and closing the glottis. (4) Arytenoideus. — This is a single muscle and arises from the posterior surface and outer border of one arytenoid cartilage, and is inserted into the same parts of the other arytenoid. Its action is to approximate the arytenoid cartilages and close the glottis, especially at the posterior portion. Fig. 195. — Larynx and its lateral mus- cles after remo%'al of the left plate of the thyroid cartilage: 1, thyroid cartilage; 2. thyro-epiglottic muscle ; 3, cartilage of Wrisberg ; 4, ary -epiglottic muscle ; o, cartilage of Santorini ; 6, oblique ary- tenoid muscles; 7, tliyro-arytenoid mus- cle ; 8. transverse arytenoid muscle ; 9, processus muscularis of arytenoid car- tilage; 10, lateral crico-arytenoid mus- cle; 11, posterior crico-arytenoid mus- cle : 12, cricothyroid membrane ; 13, cri- coid cartilage ; 14, attachment of crico- thyroid muscle; 15, articular surface for the inferior cornu of the thyroid car- tilage; 16. cricotracheal ligament; 17, cartilages of trachea ; 18, membranous part of trachea (Stoerk). 346 RESPIRATION. (5) Tliyio-arytenouhus. — This muscle arises from the angle of the thyroid and the cricothyroid membrane, and is inserted into the arytenoid cartilage. It consists of two portions, ov Jdsc'u-idi : An inner, which is inserted into the vocal process of the arytenoid and is adherent to the true vocal cord ; and an outer portion, Avhich is inserted into the rauscidar process. The action of the two muscles as a whole is to draw the arytenoid cartilages toward the thvroid, shortening and relaxing the vocal cords ; the inner fasciculus acting alone modifies the elasticity and tension of the vocal cords, while the outer rotates the arytenoid cartilages inward and approximates the cords. (6) Thyro-epiylottideus. — It arises from the angle of the thyroid Fig. 196. — The laryugoscopic image in easy breathing : 1, base of the tongue ; 2, median glosso-epiglottic ligament; 3, vallecula ; 4, lateral glosso-epiglottie ligament; 5. epiglottis ; 6. cushion of epiglottis: 7. cornu major of hyoid bone; 8, ventricular band, or false vocal cord : 9. true vocal cord : opening of the ventricle of Morgagni seen between 8 and 9: 10, folds of mucous membrane; 11, sinus pyriformis; 12. car- tilage of Wrisberg ; 1.3, aryteno-opiglottic fold; 14, rima glottidis : 1.5, arytenoid cartilage ; 16, cartilage of Santorini : 17. posterior wall of pharynx (Stoerk). cartilage, and is inserted into the aryteno-epiglottic fold and the margin of the epiglottis. The action of these muscles is to depress the epiglottis, and, by virtue of some of the fibers which spread out upon the outer surface of the sacculus laryngis, to compress it. (7) Aryfeno-epif/loftifJeus Superior. — This arises from the apex of the arytenoid, and its fibers disappear in the aryteno-epiglottic fold. The action of the pair is to constrict the opening of the larynx during deglutition. (8) Aryteno-epiglottideus Inferior. — This mu.scle also arises from the arvtenoid, and spreads out upon the inner surface of the .sacculus laryngis, and the action of the pair is to compress the sacculus. Gray, to whom we are indebted for the description of the THE LARYNX. 34'; larynx and other anatomic stnu'tnrcs, in considering the action of these muscles, says that they may he conveniently divide(l into two i^roups, viz., 1. Those which open and close the ghjttis ; 2. Tlutse which regidate the degree of tension of the vocal cords. 1. The nniscles which open the glottis are the crico-arytenoidei postici,and those which close it are the arytenoidens and the crico- arytenoidei late rales. 2. The muscles which regulate the tension of the vocal cords are the crico-thyroidei, which tense and elongate them ; and the thvro-arytcnoidci, which relax and shorten them. The thyro- epiglottideus is a depressor of the epiglottis, and the aryteno- epiglottidei constrict the supe- rior aperture of the larynx, compress the sacculi laryngis, and empty them of their con- tents. Interior.— If the larynx is inspected from above, looking downward (Fig. 196), it will be seen that its openiiif/ is l)ounded in front by the epiglottis, behind by the interarytenoid fold, con- sisting of mucous membrane, connecting the arytenoid carti- lages, and the arytcno-epiglottic. folds, also mucous membrane, which connect the sides of the epiglottis and the arytenoid car- tilages. The cartilages of San- torini and Wrisberg make prom- inences in these folds. The cavity of the larynx (Fig. 197) extends from its opening to the lower border of the cricoid cartilage. In look- ing into it there will be seen the inferior or true vocal cords, vocaf bands or ligaments, the portions which approximate the most closelv, and between them a space or fissure, the glottis or rima glot- tidis. " The term rima glottidis is applied by some authors to the boundary of the space, and bv others to the space itself, using it synonvmouslv with r/lottis. Above the true vocal cords are the superior or false vocal cords, and between the true and false on Fig. 197.— Vertical transverse section of the larjTix : 1, posterior face of epiglot- tis, with 1', its cushion; 2, aryteno-epi- glottic fold ; 3. ventricular band, or false vocal cord ; 4. true vocal cord ; 5, central fossa of Merkel ; fi, ventricle of larynx, with (i', its ascending pouch; 7, anterior portion of cricoid : 8, section of cricoid ; 9, thyroid, cut surface ; 10, thyrohyoid menii)ranf; 11, thyrohyoid muscle; 12, aryteno-epiglottic muscle; 43, thyro-ary- teiioid muscle, with 13', its inner division, contained in the vocal cord ; 14, cricothy- roid muscle; 15, subglottic portion of larynx; 16, cavity of the trachea (after Testut). 348 EESPIBATION. each side is the ventricle of Morgagni, the anterior part of which connects with the sacculus laryngis, or laryngeal pouch, into Glands iu false vocal cord. Ventricle of Morgagni — Stratified pavement epithelium of true \~ vocal cord. \ Stratified ciliated col- umnar epithelium. Glands. Muscle. Muscle. Fig. 198. — Vertical section through the mucous membrane of the human larynx ; X 5 (Bohm and Davidofi"). which discharge 60 or 70 glands situated in the submucous areolar tissue. TliE LARYNX. 349 The glottis and the true vocal eorils demand a somewhat more detailed description than j^iven above, owing to their importance in connection with respiration and phonation. Glottis (Figs. 194-196, 199-201).— This opening diifers in shape under different conditions. Its length from the angle of the true vocal cords in front to the vocal processes of the arytenoid cartilages behind is about 2.5 cm., and its breadth when dilated varies from 0.8 cm. to 1.2 cm. During ordinary inspiration its breadth increases, becoming triangular, and in very deep or forced Fig. 199. — The voicing (female) larynx: A, small or highest register; B, upper thin or middle register; C, lower thin or middle register ; T, T, tongue ; F, F, false vocal cords ; <'^, S, cartilages of Santorini ; W, W, cartilages of Wrisberg ; V, V, vocal cords (after Browne and Behnke). inspiration lozenge-shaped, while during phonation the vocal cords are more approximated than at tiie end of respiration. Fig. 200. — The larynx in gentle breathing: L, epiglottis; F, vocal cords; •S cartilages of Santorini, which sur- mount the arytenoid cartilages ; P, P, ventricular bands (Lennox-Browne). Fig. 201. — The larynx in deep breath- ing : IF P. tracheal rings ; B, openings of bronchi ; P, P, ventricular bands (Lennox-Browne). The changes which take place during voice-production are more fuUv considered in connection with that function of the larynx (p. 378). True Vocal Cords. — Tliese are called also vocal bands and vocal ligaments. They consist of strong fibrous bands covered Avith mucous membrane, and parallel Avith them and attached to them are the inner portions of the thyro-arytenoid muscles. The mucous memhrane lines the entire larynx, and forms the folds already described. Below the false vocal cords it is covered with columnar ciliated epithelium. Above these cords cilia are only found in front up to the middle of the epiglottis. Elsewhere, in- cluding the true cords, the epithelium is stratified. Vessels and Nerves. — The arteries which supply the larynx are derived from the superior and inferior thyroid. The nerves are 350 RESPIRATION. the superior laryngeal, a branch of the vagus, which supplies the mucous membrane, the cricothyroid and arytenoid muscles; and the inferior laryngeal, or recurrent laryngeal, also a branch of the vagus, which supplies all the other muscles, and also the arytenoid muscle. THE TRACHEA. The trachea or windpipe (Fig. 202) is about 11 cm. in length, and 2.5 cm. in diameter, and extends from the cricoid cartilage to its division into the bronchi, which corresponds to the fourth or fifth dorsal vertebra. Stnicttire. — It is composed of rings of cartilage, from 16 to 20 in number, which are incomplete behind, Avhere the trachea is in contact with the esophagus. These cartilaginous rings are situ- ,i-4!«*';"»*4fflvs.^SS*: «^ ,?»i^ Fig. 202. — From longitudinal section of human trachea, stained in orcein (Huber). ated within the two layers of an elastic fibrous membrane. In the spaces between the rings these layers unite, thus forming a single membrane. The membrane behind is also single. Be- tween the ends of the cartilaginous rings is also a transverse layer of unstriped muscular tissue, trachealis muscle, and posterior to this are some longitudinal fibers of the same kind. The trachea is lined with mucous membrane covered with columnar ciliated epithelium, and in it are mucous glands, tracheal glands, whose secretion lubricates the membrane, and there are elastic fibers arranged longitudinally. Blood-vessels. — The artery supplying the trachea is the inferior thyroid, and its veins terminate in the thyroid venous plexus. Nerves. — The nerves are branches of the vagus and sympa- thetic. PLATE III. A. upper bone of sternum; B, B, two first ribs ; C, C, second pair of ribs ; D, D, right and left lungs; E, lower end of sternum; F, F, right and left halves of the diaphragm in sections: the right half separating the right lung from the liver, the left half separating the left lung from the broad cardiac end of the stomach ; G, G, eighth pair of ribs; K, K, ninth pair of ribs (Maclise). TIIK LUNGS. 351 THE BRONCHI. These are two in nuinber : tlie right bronchus, wliieh is more liorizontal tlum the left iiiul is about 2.5 cm. in length, divides into three subdivisions which go to the right lung, which has three lobes. The left bronchus is about 5 cm. long, and divides into two branches, one for the upper, and the other for the lower lobe of the left lung. The bronchi are, like the trachea, made up of cartilaginous rings or plates with intervening membrane. THE LUNGS. There are two lungs, right and left, situated in corresponding sides of the thorax ; each being divided by fissures into lobes— the right into three, superior, middle, and inferior, and the left into t\vo, superior and Inferior. The root of the lung, where this organ is connected with the heart and trachea, is composed of bmnchus, puhnomiri/ artery, pulmonary veins, bronchial arteries, bronchial veins, pulmonary plexus of nerves, lymphatics, bronchial glands, and areolar tissue, all covered by a serous membrane— the pleura. Structure. — Each lung is covered by the visceral layer ot the pleura, beneath which is areolar tissue containing elastic fibers. This coat exists not onlv on the outside, but also penetrates into the interior between the lobules. The lobules form the parenchyma of the lung. Lobules. — A lobule consists of a terminal or idtimate bronchial tube and the air-cells or cdveoli, into which it opens, together with such pulmonarv and bronchial vessels, lymphatics, and nerves as are associated 'therewith. Each lobule may be regarded as a miniature lung, a lobe being made up of many lobules. Their form and size'varv, those which are on the exterior of the lung being pvramidal "in shape, the base forming a polygonal figure ; while those more deeply seated present considerable variations from this. To obtain a clearer idea of the minute structure of the lung than can be obtained from the above description, it will be profitable to approach the lobule from the direction of the bronchi.^ After entering the lung the bronchi divide and subdivide into two branches, or dichotomously, occasionally into three. The cartilages become plates or lamina^ between them being mem- brane. When the bronchial tubes become as small as 0.5 mm. the cartilage disappears and the walls are membranous ; the fibrous tissue and the longitudinal elastic fibers continue throughout, while the muscular tissue, equally extensive, is arranged around the tubes. The mucous membrane continues to be covered with ciliated epithelium of the columnar variety, until the lobule is reached. At this point each subdivision of a bronchus becomes 352 RESPIRATION. a lobular bronchial tube or bronchiole or ultimate bronchial tube, and on one side dilatations exist, air-cells or pulmonary alveoli. Artery. \~;? — Lung-tissue. Respiratory iJ_- bronchiole. A^W /K^ i. i ^ V^.^v^ \__L^_ —ZEf-'^S. — Lung-tissue. Alveolar duct. ^^SftJ^^^P^.^ \, i\f-^\C? Fig. 204. Figs. 203 and 204.— Two sections of cat's lung : Fig. 203, x 52 ; Fig. 204, X 35 (Bohm and Davidoff). These increase in nnmber, and, although at first limited to one side of each bronchiole, they subsequently surround the tube, and the THE LLWCS. 353 bronchiole becomes enlarged, forming' the atrium, which opens into sac-like cavities, infundibuld, each infundibulnm being about 1 mm, in diameter, and these open into (lir-cel/.-i or pidmonary alveoli, which latter have a diameter of from 0.1 mm. to 0.3 mm. At the infimdibula the muscular tissue is less abundant and the elastic Hbers are arranged around the openings of the air-cells. The epithelium in the bronchioles is both cohunnar ciliated and cubical non-ciliated ; Ijiit in the infundibula and alveoli it is of the pavement variety, with some cubical. Blood-vessels. — JJranches of the pulmonary artery pass into the lung witii the bronchial tubes and terminate in ihe pulmonary capillaries (Fig. 205), which as plexuses lie under the mucous mem- brane of the walls of the infundil)ula and alveoli and of the par- titions or septa between them. The capillaries have very thin '^^MJ Blood-capillaries seen in surface view. -- Alveolus in cross- section. Fig. 205. — Section through injected lung of rabbit (Bohm and Davidoflf). walls and a diameter of about more moisture from tlie Ijody than if it is moist and warm. The daily loss from this source is about 540 grams. 4. The expired air is, as a rule, warmer than the inspired. Thus in a series of obser- vations it was found that when the inspired air had a temperature of from 15° to 20° C, when expired its temperature was 37.3° C. ; when the inspired air was — 6.3° C, it was 29.80° C. when expired; and when 41.9° C. at inspiration, it was 38.1° C. at expiration. The inspired air is warmed from 1 to 2 degrees more when taken in by the nose than by the mouth. 5. The actual volume of expired as compared with inspired air is less bv about 2 per cent. 6. The expired air contains certain volatile organic matters, whose presence is at once recognized by the sense of smell, among them croivd-poimn, although chemists have not yet made us acquainted with their exact composition. The following table represents the average composition and temperature of inspired and expired air : Inspired Air. Expired Air. Oxygen 20.96 16.03 Nitrogen 78.00 78.00 Argon 1.00 1.00 Carbon dioxid 0.04 4. .38 Watery vapor variable saturated Temperature " about 37° C. Respiratory Quotient. — This is a term employed to express the ratio between the carbon dioxid given off and the oxvgen ab- sorbed, and is obtained bv dividing the former bv the latter — i. e., CO.,,4.34 ... O 4 93 ^ ^'^^' ^^ *^^* *^^^^ ^^ gained 0.88 volume of COg for every volume of O absorbed. This ratio is an exceedinglv vari- able one, differing in different animals, and even in the .same indi- vidual with age, food, temperature of the air, during exercise, etc. There are various reasons which account for these differences. CHEMISTRY OF RKSPI RATION. 3G7 It is to be borne in mind, in ilic first place, that the sources of carl)()n dioxid in the animal body are numerous. Tlie oxvgen whieh is al)sorbed at any given time does not immediately api)ear in the carbon dioxid given off; it may be absorbed and enter into combinations, which may retain it for a considerable time ; so that at any given time the amount of oxygen absorbed may be greater than that given off in the carbon dioxid, or vice verna. Then, too, more C(X is formed in proportion to the amount of oxvgen absorbeil Ijy the decomposition of some substances than others. Thus when carbohydrates constitute the diet the amount ol" oxygen which they contain is enough to satisly their hydrogen, but fats and proteids need more, and in the formation of water they use up oxygen ; from this it follows that more oxygen is absorl)ed during an animal than durin*!: a vejjetable diet. When the amount of carbon dioxid given off equals the amount of oxygen absorbed, the respiratory quotient is 1. The quotient will be higher in herbivora, where it is from 0.9 to 1.0, than in carnivora, where it is from 0.75 to 0.8. It is interesting to note that when an her- bivorous animal is fasting — that is, at a time wdien it is taking in no food, but is living on its own tissues, and is therefore for the time being a carnivorous animal — the quotient is that of the car- nivora, 0.75. In observations upon man it is found that before feeding the quotient is 0.84 to 0.89 ; when meat or fat is given, 0.76 ; with potatoes, 0.98 ; and with glucose, 1.03. The respiratory quotient is higher in adults than in children ; during the day than at night ; during wakefulness than during sleep ; during activity than during rest. Ventilation. — It is manifest that if at each inspiration oxygen is extracted from the air, in the course of time the amount of this gas will be so reduced as to make its want seriously felt. It is necessary, therefore, in order to keep the amount of oxygen up to the standard, that some provision should be made to supply it. Besides the removal of the oxygen, the air is still further rendered unsuited for respiratory purposes by the carbon dioxid, and especially by the organic matter thrown off by the expired air ; the oxygen being still further diminished by stoves and lights, and the air being vitiated by the products of combustion. To supply oxygen and to remove these impurities are the objects of ventilation. A common test to determine whether the air of an apartment contains sufficient oxygen for respiratory purposes is to see if a candle will burn in it. This test is used to determine whether the air in vaidts or in excavations is fit for respiration. A candle will not burn if the air contains only 17 volumes per cent, of oxygen ; a man can breathe without difficulty if there are but 15 volumes per cent. So far, then, as the question of oxygen is concerned, a man uoS BESPIRA TIOX. could breathe where a candle would not burn, but it does not necessarily follow tliat it is always safe for a man to venture where a candle icill burn, for sometimes, although there may be oxygen sufficient to sustain life, poisonous gases may also be present in an amount sufficient to produce a fatal result. It would be a surer test to place a dog in the suspected place and leave him there for twenty minutes. If it survives, it will be safe for a man to enter. It is a matter of common experience that injury to health follows confinement in badly ventilated apartments, but the cause thereof has never been satisfactorily determined. The generally accepted theory is that it is not due to the carbon dioxid which is given off by the lungs, but to the organic matter — croicd-poison — exhaled in the expired air and also given off from the surface of the body, especially of those who are not cleanly in their habits, and who resort to bathing the body too infrequently. Those who maintain these views state that an air which contains respiratory CO;, — /. €., CO2 produced by respiration — to the amount of more than 0.07 per cent, is nnwholesome air to breathe, and yet that CO., may be present to the. extent of 2 per cent, provided that its presence is due to chemical processes, as in soda-water factories, and be breathed without inconvenience or any injurious conse- quences resulting. Indeed, so reliable observers as Brown-Sequard and d'Arsonval have breathed air in which CO^ was present to the amount of 20 per cent, for two hours Avithout marked distress. When, therefore, injurious effects follow from breathing air con- taining 0.8 per cent, of CO., which represents that present in a verv l)adly ventilated lecture-hall, it must be due to something else than the COo, and they attribute it to the organic matter already referred to. Brown-Sequard and d'Arsonval, who believed that it was the organic matter from the lungs which was the poison- ous matter, injected into rabbits the condensed vapor of the ex- pired air with fatal results. On the other side of the question are those who maintain that the injurious con.sequences of breathing vitiated air are due to the excessive amount of CO^and the deficiency of oxygen, and not to organic matter. In support of this theory we have the following observations : Haldane and Lorraine Smith foimd that in breathing air containing 18.6 per cent, of CO,, within a minute or two they suffered from hvperpnea, distress, flushing, cyanosis, and mental confusion ; and the injections of condensed vapor-breath into rabbits, practised by Brown-Sequard and d'Arsonval, have been repeated bv several experimenters with negative results. Besides these, other experiments have been performed, showing that no volatile poisons are exhaled with the expired air. Among the mo.'St recent investigations on this subject is that of Haldane and Lorraine Smith, reported in 1892. From this they conclude as follows : CllEMISTIlY OF RESPIRATION. 369 " 1. The imnicdiutc ilangvr.s trom brt'Utliiii<; air highly vitiated by respirati«>u arise entirely from the excess of" earljon dioxid and deficiency of* oxygen, and not from any special poison. " 2. The hyperpnea is due to excess of cari)on dioxid, and is not appreciahlv affected by the corresponding- deficiency of oxygen. The hvpcrpnea begins to appear when the carbon dioxid rises to from 3 to 4 per cent. At about 10 per cent, there is extreme distress. "3. Excess of carbon (boxid is likewise the cause, or at least one cause, of the frontal headache produced by highly vitiated air. " 4. Hyperpnea from defect of oxygen begins to be appreciable when the oxygen in the air breathed has fallen to a point which seems to difJ'er in different individuals. In one case the hyperp- nea became apprecial)le at about 12 per cent., and excessive at about 6 per cent." Haldane and Smith also regard the odorous substances present in rooms due to a want of cleanliness as contributing to the dis- comfort caused by breathing the air of such rooms. It must be remembered that the oxygen of the air is consumed and carbon dioxid and other impurities produced by stoves, gas- burners, and lamps, as well as by respiration. Thus a large gas- burner will in one hour consume as much oxygen as a human being will in five hours, and at the same time will be produced carbon dioxid and monoxid, sulphur compounds, and other gaseous impurities, all of which vitiate the air to a considerable degree. At the same time the air is heated. Perhaps one of the most important advantages which has accrued from the introduction of electricity as applied to illuminating-purposes is the entire absence of heat and of those impurities which so impoverish the air of inhabited rooms. It is generally conceded that if the respiratory CO2 in the air does not exceed 0.02 per cent, above that which is ordinarily present in all air — 0.03 or 0.04 per cent. — bringing it up to 0.06 or 0.07 per cent., no harm will result, and adequate ventilation will be secured — /. e., keeping the CO, from increasing beyond 0.06 or 0.07 per cent. To- bring this about will require as a minimum 60,000 liters (2000 cubic feet) per hour per individual, but this should be increased by at least one-half (making it 3000 cubic feet) to provide for the increased production of CO, caused by active exercise ; and in factories and workshops where all the operatives are men, and all actively at work, this amount often needs to be as much as 6000 cubic feet. For hospitals, where the emanations from the sick are more likely to vitiate the air than are those from the well, at least 60G0 cul)ic feet should be pro- vided. These figures take no account of gas-burners or lamps, and for these there should be allowed not less than 1800 cubic 24 370 RESPIRATION. feet of air for each cubic foot of gas consumed, and 18,000 cubic feet for each pound of oil burned. The cubic space allotted to each individual must also be taken into account, for experience has proved that unless the ventilating arrangements are very perfect, tlie air of an inhabited room can- not be changed oftener than three times an hour without causing draughts, which are uncomfortable, and it may be dangerous to health. It becomes necessary, therefore, to provide at least 1000 cubic feet of air-space per individual. In the dormitories of workhouses the amount allowed does not often exceed 300 cubic feet; in military barracks, 600 cubic feet, and in hospitals, 1200 cubic feet. It has also been found by practical experience that in rooms that have a height of more than 12 feet the conditions are not favorable for pro})er ventilation, for the reason that organic matters have a tendency to remain in the lower parts of rooms. A room 50 feet high, with 20 square feet of floor-space, would give 1000 cubic feet of air-space, but it would not be the same from a sani- tary point of view as a room 10 feet in all its dimensions. Atten- tion must, therefore, be paid to the amount oi' jioor-space allotted to each individual ; this varies according to circumstances. It should be at least 100 square feet. Of course, where rooms are occupied for but a short time, as in theaters, churches, etc., wliere after the audiences are dismissed the buildings can be thoroughly aired by the admission of external air, all these restrictions do not apply. It seems hardly necessary to say that due attention must be paid to the source from which the introduced air is drawn. If it is obtained from filthy cellars or from dirty streets, it may be as impure as that which it is designed to replace. For any further discussion of this subject our readers are re- ferred to text-books on liygione. Changes in the Blood due to Respiration. — When the blood reaches the lungs from the heart it is venous, and when it leaves the lungs to return to the heart it is arterial. The con- version, then, of the venous blood into arterial takes place ^vhile it is traversing the pulmonary cajiillaries. In its passage the bluish-red color which characterizes venous blood becomes changed to the scarlet color of arterial blood, and at the same time the venous blood gives up a portion of its CO., to the air, and takes O from it. From 100 volumes of blood, whether arterial or venous, ajiproximately 60 volumes of both gases can be obtained ; the ])roportion, however, varying. Thus in human arterial blood there is O, 21.6; CO^, 40.3_; and N, 16. _ The amount of nitrogen is practically the same in both varieties of blood. It is impossible to give figures which represent accurately the composition of venous blood, for while analyses of arterial CHEMISTRY OF RESPIRATION. 371 blood tiilvon from the dillereut arteries vary but little, those of venous blood from different parts of the venous system vary to a considerable deg'ree ; and even the blood from the same vein will have a different composition at different times, as, for instance, that cominy: from a ulaiid when active or at rest. In general, venous blood may be said to contain O from 8 to 12 per cent., and COj about 46 per cent. Zuntz has made many analyses, and concludes, as a result, that venous blood, as compared with arterial, contains 7.15 volumes per cent, less of O, and 8.2 volumes per cent, of CO2. Although arterial blood contains but 21.6 per cent, of O, still it can be made to take up as much as 23 per cent., which would about saturate it. But even the 21 .6 per cent, is more than is needed by the tissues in their metabolic processes. Unless, there- fore, the blood contains less oxygen than normal, there is no advan- tage to be derived from inhaling oxygen gas. If, however, the venous condition is marked, then oxygen inhaled under pressure may do good. While the arterial blood is nearly saturated with oxygen, experiments have shown that it can take up nearly four times as much CO^ as it ordinarily contains. Causes of the Interchange between O and CO. in the I/Ungs. — The trachea and bronchi can contain about 140 c.c. of air, so that at each inspiration, Avhen 300 c.c. or more of tidal air are taken in, the difference between these two figures, 160 c.c. or more, must represent the amount which passes at each inspiration into the alveoli of the lungs. When expiration occurs an equal volume is exhaled ; thus by the repeated alternation of inspiration and expiration the air in the lungs is being constantly changed. But the most potent factor in bringing about this interchange is the difusion of the gases, which depends upon their partial j^fessure — i. e., the part of the total pressure of the air which is exerted by each of its different components. This is also spoken of as tension by some writers ; although others use the term j^^^c'^'fd pi-cssu re with reference to gases in a mechanical mixture, as in atmospheric air ; and that of tension with reference to gases in solution, meaning thereby "the pressure required to keep the gas in solution." If we regard 760 mm. of mercury as representing the pressure of the atmosphere, and 20.96 as the percentage of the total volume , 20.96 X 760 .„ , , represented by oxygen, then :r^ will equal the pressure exerted by the oxvgen, or its partial pressure or tension, which ^' 0.04 X 750 is 159.29 mm. The partial pressure of the CO2 = TXTj ^'= 0.30 mm. If now we ascertain the partial pressure of these gases in the alveoli, we shall have the principal conditions affecting their diffusion. The partial pressure of O in the alveoli is estimated at about 114 mm. and of CO., at 36 mm. The O then in the air 372 RESPIEA TION. as it enters the respiratory passages has a partial pressure of 159.29 ram., while in the alveoli "it is only 122 mm. ; therefore it will diffuse inward until it reaches the point of lowest pressure. On the other hand, the partial pressure of CO^ is greatest in the alveoli — 38 ram. as compared with 0.30 mm. ; this gas will therefore diffuse outward. There is a third force causing diffusion which is regarded as possessing different value by different authorities ; this is the cardiopneumatic movements. Each time tiie heart contracts it becomes smaller, and the pressure within the thorax, but outside the lungs — the intrathoracic pressure — is diminished, with the re- stilt of causing the lungs to expand slightly, and air consequently to enter them, ^y hen diastole occurs and the volurae of the heart becomes larger, the intrathoracic pressure is relatively increased, and the air is forced out of the lungs. Besides, therefore, the en- trance and exit of air due to the inspiratory and expiratory move- ments, there is a corresponding movement of the air due to the contraction and dilatation of the ventricles. Causes of the Interchange of O and CO. between the Air and the Blood. — The fact that the amount of O and COj in the blood does not follow the general law that the amount of gas which a liquid absorbs depends to a great extent upon its pressure, is conclusive proof that these gases are not to any great extent in solution in the blood. O is in solution in the plasma, but to the extent of less than one volume, and in venous blood onlv about 5 per cent, of the CO, present is in solution. Inas- much as the amoimt of both of these gases is greatly in excess of these figures, we must look for some other explanation of their presence in the blood in the quantities in which they there exist than to solution. When the gases are extracted from the blood, as they may be bv the use of a pump devised for tliis purpose (Fig. 212), the oxvgen which is in solution is given off gradually as the pressure is reduced, but it is not until the pressure has been reduced to from one-thirtieth to one-tenth of an atmosphere that most of it comes off, and this it does suddenly when this low pressure is reached. From this it is evident that most of the oxygen is in chemical combination, and this pressure at which the gas is given off is the tension of dissociation. From various observations and experiments we know that the combination is one between oxygen and hemoglobin, forming oxyhemoglobin. It has been ascertained that theoretically oxyhemoglobin can contain 23.38 volumes per cent, of O, although it never does, but only about 20 per cent., because the hemogloV)in is not saturated ; still, blood from which the red corpuscles and consequently the hemoglobin have been re- moved, as in plasma or serum, can take up only 0.26 volume per cent. The tension of O in arterial blood is 29.64 mm. of mercury, and in venous blood 22.04 mm. CHEMISTRY OF RESPIRATION. 373 The tension of CO., in the l)l()od is as follows: In arterial blood 21.28 mm., and in venous blood 41.04 mm. COg exists in venous blood in solution to the amount of about 5 per cent.; in loose chemical combination, 75 to 85 per cent.; and in firm chemi- cal combination, 10 to 20 per cent. — or about 45 volume per cent, in all. The COo is in solution in the plasma, in combination with glol)ulin and alkali, and with sodium in the form of carbonates and biearbonates. About one-third of the carbon dioxid of the FiQ. 212. — Kemp's gas pnmp. (For detailed description see American Text-Boole of Physiology, vol. i., p. 420.) blood exists in the blood-corpuscles, both white and red, but prin- cipally in the latter, where it is in combination with the alkaline phosphates, with globulin and hemoglobin. We have seen that by various forces the oxygen in the outside air reaches the alveoli, while in turn the carbon dioxid in the latter situation reaches the exterior ; we have now to consider how the interchange between the CO^ in the blood and the O in the alveoli is effected. AVe have learned that the tension of the O 374 RESPIRATION. in the alveolar air is about 114 mm., although one observer at least places it as low as 99 mm. This has never been accurately de- termined. The tension of COg in the alveolar air is about 36 mm. In order to asceitain why the O of the air goes to the blood and the CO2 of the blood to the air, we must first know the tension of O and CO, in the blood. For this purpose an instrument known as an aerotonometer is used. The principle underlying this instrument is thus described by Pembrey in Schiifer's Fhyd- ology : " Blood in contact with a mixture of oxygen, nitrogen, and carbon dioxid gives up some of its gases if their partial pressures are greater than those of the corresponding gases in the mixture ; on the other hand, if the tensions of the gases in the blood be lower than the. respective tensions of the gases in the mixture, the blood takes up gas. These interchanges persist until equilibrium is established, until tlie tension or partial pressure of the gas in the blood is equal to that of the corresponding gas in the mixture. In the aerotonometer the blood is made to pass in a thin layer through a glass tube or tubes containing mixtures of gases of known quantity and tension, and it is arranged by prac- tice that the tension of the gases shall in the one case be greater, in the other case smaller, than the tensions of the corresponding gases in the blood. The gases in these tubes, after the blood has passed through them, are analyzed, and from the alteration in the proportion in the two tubes it is possible to calculate the partial pressure of the gases in the blood. The aerotonometer is sur- rounded by a water-jacket with a temperature of 39° C." Another aerotonometer is that of Fredericq, and Bohr has devised one known as an hemato-aerometer. The results obtained by these different instruments vary con- siderably. Strassburg gives the tension of CO2 in venous blood of the right side of a dog's heart as 5.4 per cent, of an atmosphere ; and 2.2 to 3.8 per cent, in arterial blood. Herter gives the ten- sion of O in arterial blood as 10 per cent, of an atmosphere. Bohr has obtained quite different results: 101 to 104 mm. of mercurv for the tension of O in arterial blood — higher than that of the air in the trachea. He al.so found that when the dog, the subject of the experiment, breathed pure air, the tension of the COo in arterial blood rises from nothing to 28 mm. of mercurv, and when the dog breathed air containing COj the tension varied between 0.9 and 57.8 mm. That is to say, the tension of CO2 was greater in the tracheal air than in the blood. If this is so, it is manifest that the passage of the CO, of the blood outward to the air could not be due to diffusion ; so that to explain the actual facts Bohr concludes that the tissues of the lungs play an active part in the absorption of oxygen and the elimination of carbon dioxid. Haldane and Lorraine Smith have substituted for the aerotonometer a method by which " the tension of O in the CHEMISTRY OF RESPIRATION. 375 arterial blood is calculated from the percentage of carbon monoxid brratiu'd bv tlic subject of the (iXiK'riment, and from the final saturation of his blood with carbon niouoxid" (Penibrey). Their results are 20. 2 per cent, of an atniospliere, or 200 mm. of mercury, about twice that of oxygen in the alveoli, which would confirm Bohr's views that diffusion cannot account for the absorption of oxv*'-en by the blood while flowing through the pulmonary cap- illaries, but that it is to be attributed to the epithelial cells of the alveoli. Notwithstanding these results, which need further investiga- tion, diffusion is usually regarded as the principal factor in de- termining the gaseous interchanges between the air and the blood. Causes of the Interchange ,of O and CO^ between the Blood and the Tissues.— This process constitutes in- tci'ual respiration. Oxygen when it reaches the tissues by the blood is immediately taken up by them and enters into chemical combination, so that as oxygen it may be said not to exist, except momentarily. On the otiier hand, the tension of oxygen in arterial blood is rela- tively high, so that its passage from the blood to the tissues is readily accounted for. The tension of CO2 in the tissues is about 58 mm. of mercury higher than in the blood ; hence its passage outward fi'om the tissues to the blood. Innervation of the Respiratory Apparatus.— The nerv- ous supply to tiie respiratory apparatus comes from the respiratory center, a collection of nerve-cells in the lower part of the medulla oblongata, though its exact location is not yet determined. Other centers, sabsidiarj/ centers, have been described, but their inde- pendence of the principal center is questioned. The respiratory center is in reality made up of two centers, one for each side, so that, although anatomically connected and ordinarily acting together, yet if one center is broken up, wdiile the respiratory movements on that side cease, those on the other side continue. Besides this double character of the center, each half is made up of an inspiratory and an expiratory center — /. e., the nervous impulses which originate and pass out from the inspiratory center produce inspiratory movements, and those from the expiratory center bring about movements of expiration. The respiratory center is both an automatic and a reflex center — /. e., it sends out spontaneously impulses which result in move- ments of the respiratory muscles, constituting its automatism ; and it may also be excited reflexly — /. e., by impulses reaching it from without. Its reflex character is most marked, and it is doubtless as a reflex center that its function is ordinarily performed. Rhythm of the Respiratory Movements. — One of the striking characteristics of the respiratory movements is their 376 RESPIEATIOX. rhythmko.Uty — i. e., the regularity with which expiration follows inspiration, then a pause, and again an inspiration followed by an expiration. It is true that tliis regularity is not as marked in the aged and in children as in others, but in a condition of health it is not markedly departed from. In certain forms of disease, how- ever, the respiratory movements are very irregular. One such is Cheyne-Stokes respiration (Fig. 213), which may occur in fatty degeneration of the heart, uremia, some brain diseases, etc. It is Fi(f. 213. — Cheyne-Stokes respiration (after Waller}. characterized by a beginning shallowness of respiration, the respi- rations gradually becoming deeper and deeper, then a return to shallowness, and finally a complete cessation of respiratory move- ments. This pause lasts for half a minute or more, M'hen the shallow movements begin as before, followed by deeper and again by shallower respirations and then by a pause, etc. This grouping of the respirations is shown in the above curve of this kind of breathing. In all reflex acts not only must there be nerve-centers which receive the impulses coming from without and those which gen- erate and emit impulses, but there must be afferent ner\'es to carry the impulses to the centers and efferent nerves to cany the outgoing impulses. The main afferent respirator}- nerve is the vagus or pneinnogastric, and it has been demonstrated that this nerve con- tains two kinds of nerve-fibers — one which carries the impulses to the inspirator}- and the other to the expiratory center, so that division of one nerve slows and deepens respiration to some degree, much more when both nerves are divided. If the end still in communication with the nerve-centers, the central end, is stimu- lated powerfully with electricity, the movements of inspiration become greater, and the diaphragm not only contracts — i. e., de- scend.s — but remains in the position of contraction. If, on the other hand, only a weak stimulus is ap])lied, the expiratory move- ments are increased, and the diaphragm remains in the position it is in at the end of expiration. It has further been demonstrated that whenever air is pumped into the lungs so as to distend them, the contraction of the diaphragm diminishes, and when fully distended the diaphragm is in the expiratoiy position — /. e., as it is at the end of an expiration. This distention of the lungs constitutes positive ventilation. On the other hand, if air is pumped out of CHEMISTRY OF RESPIRATION. 377 the lungs, the alve(ili collapse, and the contractions of the diaphragni increase, and finally the diaphragm becomes quiescent in the inspiratory position. Analogous conditions occur in normal breathing. When the lungs are distended, as in inspiration, the expiratory fibers of the vagus are stimulated, and an expiratory act follows ; when expiration is complete and the alveoli are in the condition of diminished size, it can hardly be called collapse; the inspiratory fibers arc stimulated and an act of inspiration occurs. Other afferent respiratory nerves are the superior laryngeal, glossopharyngeal, trigeminus, and sensory nerves of the skin. The superior laryngeal is the sensory nerve of the larynx, and whenever any foreign body touches this sensitive organ, or when food is inclined to go down the '' wrong way " — i. e., gets into the larynx instead of the esophagus — inspiration is at once stopped and violent coughing ejects it. In this process the afferent impulses are carried to the respiratory center, and not only is the inspiratory center restrained or inhibited, but the expiratory center is stimu- lated, and a pronounced expiratory effort, the cough, results. The glossopharyngeal is also an afferent respiratory nerve, and carries to the inspiratory center inhibitory impulses that cause all inspiratory movements to cease, as when food is swallowed. The food stimulates the terminations of the nerve in the mncous mem- brane of the pharynx, and the inhibition results. \Yere this not so, there would be danger of food entering the larynx at the time of inspiration. The trigeminus sends fibers to the mucous membrane of the nose, and Avhen these fibers are irritated by an irritant like ammonia, respiration may be arrested. The nerves of the skin also act as afferent respiratory nerves, as is well shown when cold water is dashed on the body. The efferent respiratory nerves are the 2)hrenics, which supply the diaphragm ; the vagi, which supply the muscles concerned in producing the respiratory movements of the glottis (p. 362) ; and the spinal nerves, which supply the respiratory muscles of the thorax. There are certain terms used in connection with respiration which need to be understood. Eupnea. — This term means easy respiration, and is applied to the normal act. Apnea. — This term as used by physiologists, physiologic apnea, applies to a condition in which the respiratory movements are suspended, as when the lungs are distended with air forced in by a pair of bellows. It was formerly attributed to the hyper- oxygenation of the blood, but this cannot be the only explanation, because if hydrogen is the distending gas, apnea results. Disten- tion with air is practically what has been described as positive 378 VOICE AND SPEECH. ventilation. It appears, however, from experiments that when the lungs have been distended with air, there is besides the distention enough oxygen in the alveoli to aerate the blood for a time, so that it is pr()bai)le that physiologic apnea is produced by positive ventilation, distention, and the excess of oxygen in the alveoli. Apnea is also used as a synonym for asphyxia ; in this case the qualifying adjective "physiologic'' is omitted. Dyspnea. — This is difficult or labored breathing. If caused by a deficiency of oxygen, it is 0-dyspnca ; if by an excess of carbon dioxid, CO^-f^i/spnea. Hyperpmea. — In this form of breathing the rate is moderately accelerated. Asphy.ria. — The term literally means pmlselessness, and is espe- cially applicable to the last stage. If by any means the supply of air to an animal is cut off, or so diminished in amount as to be exhausted, the animal dies in a short time from asphyxia, passing previous to the fatal termination through the following stages : (1 ) Hyperpnea. — This stage is characterized by an increased frequency of the respiratory movements, especially marked during inspiration, because of the increased stimulation of the inspiratory center. (2) Dyspnea. — In this stage, the expiratory center is espe- cially stimulated, and as a result the movements of expiration are more pronounced than those of inspiration, the expiratory muscles (p. 360) being brought into action. These two stages last about one minute. (3) ConvnL'tion. — This stage is characterized by convulsive movements throughout the body. (4) Exhaustion. — The expiratory muscles being exhausted, the animal becomes quiescent, only a few slight attempts at inspiration being perceptible. After a time these become deeper, but only occur at comparatively long intervals. (5) Inspiratory Spasm. — The intervals between the inspirations have in this stage greatly increased, and apparently ceased, but they recur occasionally. The pupils are dilated and the pulse becomes less and less perceptible ; finally a last inspiration occurs and the animal is dead. VOICE AND SPEECH. The voice is produced by the vibration of the true vocal cords, vocal bands, or vocal ligaments, by all of which terms they are called, these being set in vibration by the respired air as it passes out from the lungs, if at the time the bands are approximated and tense, and if, also, the current of air is sufficiently strong. At the same time, the sounds produced by the vibrating bands are sup- LARYNGOSCOPE. 379 plemented by the cavities above and below them, which act as resonators. For the anatomy of the larynx the reader is referred to page 343 ; in order to understand voice-proiluction a knowl- edt'-e of the anatomy of this organ is absolutely essential. Especial attention should be paid to the muscles and their action. Ivaryngoscope. — In order to observe the changes which take place in the vocal bands, use is made of the laryngoscope. This instrument also enables the physician to study the other structures of the larynx and trachea, and to treat any diseases of these organs which may be present. The laryngoscope consists of a concave head-mirror with an aperture in'its center, and one or more small hand-mirrors. The Fig. 214.— The laryngoscopic image in easy breathing : 1, base of the tongue ; 2, median glosso-epiglottic ligament ; 3, vallecula ; 4, lateral glosso-epiglottic ligament ; 5, epiglottis ; 6. cushion of epiglottis ; 7, cornu major of hyoid bone ; 8, ventricular band, or false vocal cord ; 9. true vocal cord ; opening of the ventricle of Morgagni seen between 8 and 9; 10, folds of mucous membrane; 11, sinus pyriformis; 12, car- tilage of Wrisberg ; 13, arvteno-epiglottic fold ; 14, rima glottidis ; 15, arytenoid cartilage ; 16, cartflage of Santoriui ; 17, posterior wall of pharynx (Stoerk). person whose larynx is to be inspected is seated at the side of a lamp, gas, or electric light, and in front of him is seated the observer, with the head-mirror so attached that he can look through the aperture in its center. The observed now opens his mouth, the head being thrown back, and with a napkin the tongue is drawn out and its tip is held against the lower teeth, by which act the epiglottis is drawn forward. One of the hand- mirrors is then slightly heated and passed into the mouth, its back elevating the uvula ; the head-mirror is then so directed as to re- flect the light on the hand-mirror and illuminate the image formed by it of the larynx and trachea. If the hand-mirror is not heated, the vapor of the expired air will be condensed upon it, obscuring the reflected image. To avoid overheating it and burning the 380 VOICE AND SPEECH. parts of the throat with which it comes in contact, the observer touches it to the back of his hand before introducini;- it. The image which is seen (Fig. 214) is reversed — /. e., the epiglottis appears in the upper portion of the image, and the left side of the larynx is at the right, as seen by the observer. Laryngoscopic Image during Respiration. — If the glottis is ex- amined in the cadaver, the separation of the bands is but about 1 or 2 mm., while during life, wlien ordinary or quiet breathing is taking place, the separation amounts to 3 to 4 mm. Nor is there, in most individuals, much diiFereuce between ordinary inspiration and expiration as to the width of the opening, although in some the bands do separate a little during inspiration and again approach during expiration. During deep inspiration the width of the rima glottidis may be 1.3 cm. Laryngoscopic Image during Voice-production or Phonation, — "NVhen a tone is produced the vocal bands approach each other and are rendered more tense ; and the greater the tension the higher is the note. Although in the production of a high note the cords are correspondingly approximated, still this does not seem to be essential, while increased tension of the cords is absolutely neces- sary to the production of a more elevated tone. It is claimed that the depression of the epiglottis and its consequent partial covering of the glottis render the tones produced by the vibrating bands lower in pitch, and that the epiglottis also acts as a sounding-board by reinforcing the vibrations of the air-column which im- pinges against it. Resonance. — This is defined as "A prolongation or reinforcement of sound by means of sympathetic vibra- tion, or the capal)ility of producing such a continued sound" (Sfdndard Didion- arij) : or " The pro])erty of a sonorous body that enables it to absorb the vibra- tions of another sonorous body and vi- brate in unison with it" (AVentworth and Hill). Bodies which possess this property are resonators, and good examples are resonant boxef<, such as the body of a violin, which contain masses of air. The action of a resonator is illustrated and explained as follows (Fig. 215) : If a vibrating tuning-fork is held over the mouth of a cylindrical jar, of about 2 inches diam- eter and 12 inches deep, and water is poured in slowly, it will be noticed that as the air-column grows shorter, the sound grows Fig. 215.— Tuning-fork and cylindrical jar, to illustrate reso- nance (Carhart and Chute). INTENSITY— PITCH. 381 louder until a certain length is reached, after which it grows weaker. Forks of diiferent length will be found to have tiieir own length of air-eolunm, respectively, which reinforces its sound. The exphuiation is this : '' When the prong a moves to b, it makes half a vibration, and hence generates half a sound-wave. The condensation it produces passes down the tube AB, is reflected from the bottom, and returns to unite with other waves sent out by the prong. Now, if AB is of the proper length, this condensa- tion can move up the tube and return to combine with the con- densation produced by the prong moving from b to a, thus making the condensation more marked and thereby strengthening the sound. The effect of the fork on the column of air is to set it in vibration, and the layer of air at its mouth has the sound-pro- ducing properties of a sonorous body of large area" (Carhart and Chute). As already stated, the voice is produced by the vibrations of the tense vocal cords due to the expiratory blast of air emitted from the lungs. As in musical sounds, so in the voice, the three properties of intensity, pitch, and quality are to be found. Intensity. — The intensity or loudness of the voice depends upon the amplitude of the vibrations of the bands, the force with which the air is emitted, and the resonance cavities, viz., the chest and the cavities of the head, all of which contain air. The air being set in sympathetic vibration by the vibrations of the vocal bands, reinforces the sound produced by the bands. Pitch. — The pitcli of the tones produced by the vibrating vocal bands depends upon the same elements as in any vibrating string — i. e., length, tension, and thickness. Thus, the female voice is of a higher pitch than the male, because of the lesser length of the bands in the female than in the male. The following table (Browne and Behnke) shows the vibrational number of a few extreme tones used in music : Large organs C iv. . . 16^ vibrations per second. Latest grand pianos A iv. . . 21\ " " " Ordinarv modern pianos . . . . C iii. . . 33 " " " Double bass E iii. . . 41^ " " " Pianos with usual compass ... A iii. . . 3520 " " " " " exceptional compass . Civ. . .4224 " " " Piccolo-flute D iv. . . 4752 " " " The length of the bands in childhood is from 6 to 8 mm.; in the female adult about 11 mm., and may be stretched to 15 mm. or more ; and in the male adult 15 mm., with a capability of ex- tension to 20 mm. AVhen the cricothyroid muscle contracts, the bands are lengthened and made tense. The structures of the bands and their attachments are such that they may vibrate as a whole or only in part ; thus, when the vocal processes of the arytenoids are approximated, as they are by the contraction of the lateral crico- 382 VOICE AXD SPEECH. arytenoid and transverse arytenoid muscles, the posterior portion of the bands does not vibrate, and the anterior portion alone vibrating produces a high note. The range of an individual voice is about 2^ octaves, while 3^ octaves is very exceptional. The range of the human voice is about 5^ octaves ; the lowest bass, F iii., with 44 vibrations per second, and the highest note ever sung, so far as is recorded, B ii., corresponding to 1980 vibra- tions per second. This note was sung bv the famous " Bastar- della." Quality. — Helmholtz defines the quality of a tone as "that peculiarity which di.-tinguishes the musical tone of a violin from that of a flute, or that oi' a clarionet, or that of the human voice, when all these instruments produce the same note at the same pitch." The quality or timbre of the human voice is due to the fundamental and overtones produced In* the bands, reinforced by those of the cavities of the head and chest acting as resonance- chambers. Registers. — The terra register, as applied to the voice, has two significations : (1) The range or compass of the voice ; and (2) "a class or series of tones of a particular quality or belonging to a particular portion of the compass of a voice." Behnke defines a register as consisting of " a series of tones which are produced by the same mechanism." In singing up the scale, it will be noticed that at certain points there is a change or " break " in the quality of the voice, and at these points the voice is said to pass from one register to another. Thus, low notes belong to the chest register, and when they are emitted the chest will be felt to vibrate if one places one's hand upon it, and the voice produced is the chest voice: above this is the middle register, and the highest of all is the head ^register, in which the air in the head cavities acts as a resonator. Some prominent authorities denominate the middle register also falsetto, although this term is more commonly used with reference to certain peculiar high-pitched notes not often emitted, and said to be due to vibrations of the extreme edges of the cords only. The falsetto may be considered as a fourth reg- ister. Prof. Thos. R. French is of the opinion that "the female voice has three registers ; and that it is quite probable that in voices with exceptional ranges there are four registers, but suffi- cient evidence has not yet been obtained to make this demon- strable." Speech. — Phonation, or voice-production, is a faculty common to all animals having vocal l)ands, while the faculty of speech is peculiar to man. Channing says : " A man was not made to shut up his mind in itself, but to give it voice and to exchange it for other minds. Speech is one of our grand distinctions from the brute." It is possible that this attribute of man may not be solely his, as some recent observations on monkeys have been VOWELS— PHOTOGRAPHY OF THE LARYNX. 383 made which wouhl U'ud to the conchision that tliey can commuui- cate to a certain extent with their fellows. Vowels. — These are sounds produced by vibrations of the vocal bands, but modified by the resonating cavities, to which modification the diti'erence in their quality is due : and if the variations in the cavity of the mouth together with those of the tongue and soft palate are observed while different vowels are sounded, this fact will be readily understood (Fig. 216). Consonants. — These are not produced by the vocal bands as are the vowels, but by obstructions placed in the way of an out- going blast of air; and places Avhere these obstructions are placed are positions of articulation. " The consonants are classified ac- cording to (1) their places of closure; (2) the completeness of the closure ; (3) their utterance with breath or voice. The first dis- tributes them into (a) labials, or lip-consonants — p, f, b, v, m, w ; (6) dentals, or tooth-consonants — t, d, th, dh ; (c) palatals, or palate- Fig. 216.— Section of the parts concerned in phonation. and the changes in their relations in sounding the vowels .4- C*), /(«). U {"<>) : T, tongue; p. soft palate; e, epiglottis ; g, glottis ; h, hyoid bone ; 1, thyroid ; 2, 3, cricoid ; 4, arytenoid cartilage (after Landois and Stirling). consonants, including sibilants — s, z, sh, zh, and liquids, I, v, n, v ; (c/) gutturals, or throat-consonants — c-k, ch (Scottish lock), g, gh, (Irish lough), h, ng. " The second division gives mutes, having tight closure — p, b, t, d, c-k, g ; the other consonants are continuous. " The third division gives : (1) Surds — p, t, ch, c (k), f, th (as in thin), s, sh, h. (2) Sonants — b, d, j, g, v, dh, z, zh, av, I, r, y, m, n, ng" (Standard Dictionar)/]. Photography of the I^arynx. — Prof. Thomas E. French, of the Long Island College Hospital, has brought laryngeal pho- tography to a high state of jierfection, and has demonstrated most thoroughly the changes which take place in the vocal bands during the act of singing. The results of his observations are recorded in the Xew York Medical Journal. To him we are indebted for our present knowledge of this important subject, and from his articles in this publication we quote freely ; the illustrations are also taken from the same source. 384 VOICE AND SPEECH. In photographing the larynx, Prof. French uses the electric arc light. The apparatus is shown in Fig. 217. It consists of an automatic 200U-candle-power lamp partly inclosed in a metal box. The front face of the box carries a condensing lens which, when placed 9 inches from the arc, gives a focal distance of 20 inches. This relation of light and lens is ibund to give the most satisfac- tory illumination. The lamp and accessories are fitted to a narrow board which is placed upon a table of sufficient height. The light can be raised or lowered by means of a device designed for that purpose. The rheostat is placed upon a shelf beneath the table top. The whole light outfit is but a modification of the electric stereopticon. This one is so arranged that by adding a second Fig. 217.- -Showing the manner iu which photographs of the larynx and posterior nares are secured with the aid of the arc light. condensing lens and an objective lens to the end of the cone- shaped tube in front it can be used as a projecting lantern. In speaking of the action of the glottis, Prof. French says that with all his experience he has not yet permitted himself to formu- late a theory of the action of the glottis in singing, for even now, after a large number of studies have been made, the camera is con- stantly revealing new surprises in the action of the vocal bands in every part of the scale. The movements of the larynx in a much larger number of subjects must be revealed, grouped, and recorded before definite conclusions can be drawn. Most of our past knowledge on the subject of the changes in the larynx during singing has been obtained from inspection of this organ through the laryngoscope. As these changes follow each other too rapidly to be appreciated by the eye, much of this knowledge has been found to be erroneous. The photographic PHOTOGRAPHY OF THE LARYNX. 385 plate, however, is so sensitive that e\X'rv detail ean be recorded, and as a result ol" its application to the physiology ol" the larynx, much that was regarded as established has been donionstrated to be false : just as the older ideas of the form of a lightning-Hash have been entirely changed by instantaneous photography. The ditheulties to be overcome in photographing the larynx so as to show the changes during voice-])r()duetion are many, among Fig. 218. — Apparatus used iu photographing the larynx. them being the fact that it is only in certain individuals that the vocal bands can be seen throughout their whole length. This is very well shown in Fig. 220. In No. 1 the insertions of the vocal bands into the thyroid cartilage are so exposed as to be sus- ceptible of being photographed; in 'No, 2 these are covered by the anterior wall of the larynx, and it would therefore be impos- sible to determine in such a larynx whether the vocal bands were lengthened or shortened in passing from one register to another, 25 386 VOICE AND SPEECH. or (luring a cliange in the pitch of the voice. In some individuals the bands will be exposed tliroughout their length while some notes are being sung, while during the singing of others they will be covered. Fig. 221 shows this ; while singing F sharp and D, the bands are exposed, but covered when E is being sung. The number of ])ersons whose laryngcs are so constructed as to permit photographing to determine the changes taking place in the glottis Fig. 219. — Photograph taken by Prof. French of a normal hxrynx in quiet respiration. throughout all the registers is, it will be seen, limited, and wlio they are can only be ascertained by careful inspection. Nor are the changes which take place the same in all individuals. The following photographs show these changes in the larynx of a well-known professional contralto singer, and their explana- tion will be given in Prof French's words : No. 1. No. 2. Fig. 220.— Pair 1. " The voice in tliis singer is of excellent quality. The first of the pair (Fig. 222, No. 1) was taken while F sharp, treble clef, third line below staff, was being sung, and the second (No. 2) while she was singing E above. All notes in this and the following series were sung in the key of A. These are one of the lowest and the highest notes of her lower register. In the photograph represent- ing the lowest note it can be seen that the vocal bauds are quite PHOTOGRAPHY OF THE LARYNX. 387 short and wide, and that, with the exception of the anterior fourth, the li<;anientous and a part of" the cartilaginous gh>ttis is open and the slit between the vocal bands is linear in shape. As the voice aseenils the scale the vocal bands increase in length and decrease in width, until at the highest note of the register they can be seen to have become considerably longer. It can also be observed that the lio-anientous portion of the glottis is still open to the same relative extent, and tliat the cartilaginous ])ortion has opened to its full ex- tent. In the photograph representing the lower note the anterior faces of the arvtenoid cartilages can be seen. As the voice ascended, the capitula Sautorini were tilted forward. This seems to be proved Fig. 221. by the change in the position of these structures as seen in the photograph representing the upper note, as well as a similar change to be seen in nearly all the series showing the registers which I have taken. The epiglottis, though not well illuminated, seems to have risen as the voice ascended the scale. The light upon the epiglottis is so weak that the structure does not appear at all in the" photo-engraving. The vocal bands have increased in length at least i inch in 7 notes. The compass of the voice of this sub- 388 VOICE AND SPEECH. ject is about 2^ octaves. Therefore, at that rate of lengthening, the vocal bauds would increase nearly ^ inch if their length was progressively increased while singing up the scale from the lowest to the highest note. This progressive increase in length does not, m Ft m No. 1. E Fig. 222.— Pair 2. No. 2. however, occur, and the reason is apparent in Fig. 223, which shows the changes which took place in the larynx at the lower break in the voice, which, in this subject, occurs at F sharp, treble clef, first space. E i^ No. 1. Fig. 223.— Pair 3. No. 2. " The changes which occur at this point are extremely inter- esting and instructive. In the transition from the lower to the middle register, from E to F sharp, in the voice of this subject, the vibratory portions of the vocal bands are shortened about -^ PHOTOGRAPHY OF THE LARYNX. 389 inch. The anterior insertions of the voeal bunds can be seen in botli photographs ; therefore the actnal tlitf'erenee in the length of tlie bands can be appreciated. The vocal bands have not only become shorter, bnt thev apjiear to be snbjeeted to a much higher degree of tension. The cartilaginous glottis is closed and the aperture in the ligamentous portion has been much reduced in size. The laws wliich govern the pitch in both string and reed instruments will aid us in explaining these changes. Though the tone is higher and the degree of stretching less than in the note below, the tension is increased, and the aperture through which the air passes is much narrower. It seems to me that this clearly defined change in the mechanism of the vocal bauds — which, so far as my investigations permit me to judge, are at this point in the scale the rule — will assist us to a clear understanding of the action of the laryngeal muscles in singing when we reach that part of the study. '* In the first photograph, which was taken while the subject ■was singing the note immediately preceding that on which the break occurred, the vocal bands can be seen to be long and wide and the posterior three-fourths of the chink of the glottis is open. By open, I mean that the edges of the vocal bands are not in actual contact. The anterior fourth or fifth of the ligamentous portion of the glottis is closed. The space between the vocal bands is widest in the cartilaginous portion of the glottis. In the production of the next note higher, F sharp, the second of the pair, a marked change in the size of the larynx and in the length of the vocal bands is seen to have occurred. The cavity of the larynx has been suddenly reduced in size and the vocal bands have been shortened. The cartilaginous portion of the glottis is closed and the ligamentous portion is open in a linear slit from the posterior vocal process to within a short distance of the an- terior insertions of the vocal bands. The decrease in the length of the vibratory portions of the vocal bands is due to the closure of the cartilaginous glottis, for the ligamentous glottis remains about the same as in the note before the break. The arytenoid cartilages have been brought much closer together and occupy a more posterior position. These pictures were taken one after the other in quick succession, the conditions in every respect, except the note sung, being the same. The anteroposterior and lateral dimensions of the cavity of the larvnx are shown to have been considerably decreased when the voice broke into the register above. When the mechanism of the larvnx was changed the voice acquired a very different quality, which continued, in grad- ual elevation of pitch, throughout the register. As marked a change as this in the mechanism of the vocal bands in females is, I believe, found only in the larvnges of contralto singers. " It is believed bv manv writers on the voice that with the 390 VOICE AND SPEECH. change in the mecliauism of the vocal bands the epiglottis is raised higher than in the register below. I am of the opinion that it is usually depressed. The reason for this belief is that, with very few exceptions, I have found it lower in the photo- graphs showing the change than in those representing the note preceding it. When the voice of this subject broke into the middle register it was with difficulty that J could get the epiglottis to rise as high as it is shown here, which, though high enough to show the anterior insertions, is not so high as it was before the break. There does not seem to be any difference in the width of the vocal bands, but in this particular the appearances vary, the variation being due to the position of the ventricular bands. The entire upper surfaces of tlie vocal bands are rarely exposed to view during the production of the middle and upper notes. D ^ No. 1. No. 2. Fig. 224.— Pair 4. "As this singer ascends the scale above the break at F sharp, the vocal bands are increased in length and the chink gradually enlarges, as shown in Fig. 224. The first photograph is of the larynx while singing F sharp, treble clef, first space, the note on which the lower l)reak occurred, and the second Avhile singing D, treble clef, fourth line, which is the highest note in the middle register of the voice of this singer. The difference in the length of the vocal bands and width of the chink of the glottis, as the voice mounts from the lowest to the highest note of the middle register, is clearly shown. Not only is it shown that the vocal bands increase in length as the voice ascends the scale, but the cartilaginous portion of the glottis — which, while producing the lowest note of this register, is seen to be tightly closed — has begun to open again, as shown by the small triangular opening which has appeared between the arytenoids in the second of this PHOTOGRAPHY OP TUP LARYNX. 391 pair. A<;ain, as the vocal l)ands increase in len<;tli in this rcf^ister their tension is apparently decreased. The capitula Santorini, which in the photo, the capitula Suntorini are tilted more and more forward, and tlu; (■i)iiis "lottis is then closed. The glottic chink becomes mnch narrower and linear in shape, the capitula San tori ni are tilted backward, and the epiglottis is depressed. " When the vocal bauds are shortened in the change at the lower break in the voice, it is mainly due to closure of the carti- lao-inous portion of the glottis, the ligamentous portion not usually being affected. If, therefore, the cartilaginous glottis is not closed, there is usually no material change in the length of the vocal bands. " As the voice ascends from the lower break, the vocal bands increase in length and diminish in width, the posterior portion of the glottic chink opens more and more, the (tapitula Santorini are tilted forward, and the epiglottis rises until, in the neighborhood of E, treble clef, fourth space, another change occurs. " The glottic chink is then reduced to a very narrow slit, in some subjects extending the whole length of the glottis. In others, closing in front, or behind, or both. Not only is the cartilaginous glottis always closed, but the ligamentous glottis is, I believe, invariably shortened. The arytenoid cartilages are tilted back- ward and the ej)iglottis is depressed. As the voice ascends in the head register the cavity of the larynx is reduced in size, the aryte- noid cartilages are tilted forward and brought closer together, the epiglottis is depressed, and the vocal bands decrease in length and breadth. If the posterior part of the ligamentous portion of the glottis is not closed in the lower, it is likely to be in the upper notes of the head register." VITAL HEAT. The temperature of a lifeless object is apj)roximately that of the air which surrounds it; the temperature of a living object is independent of the temperature of the air, although it may be modified by it. This difference is due to the fact that living things produce heat within themselves ; this is called " vital heat." Many, perhaps most, authorities speak of it as " animal heat," but, though it is most striking in members of the animal kingdom, yet inas- much as its production is not confined to animals, but also occurs in plants, the writer prefers the term vital heat as indicating that the phenomenon is peculiar to the living condition, irrespective of the question whether it occurs in an animal or in a vegetable. Warm-blooded Animals. — The term warm-blooded was ap- plied to certain animals because their temperature was so high as to make them warm to the touch, while others were spoken of as cold-blooded because they were cold to the touch. Thus, man, with 396 VITAL HEAT. a temperature of 37° C, the doi>:, 39°, the cat, 39°, the swallow, 44° or even higher, are among the warm-blooded, while reptiles and fishes, whose temperature is from 1.7 degrees to 4.5 degrees C. above that of the medium in whioli they exist, are cold-blooded. The terms warm-blooded and cold-blooded are, however, now not so frequently used as formerly, but in their stead are used the terms homoiothcrriud and poikilotheniial. Homoiothermal animals are animals of uniform heat or those whose temperature is unvarying. Tiie thermometer if in- troduced into the rectum of a man, whether he is in the tropics or in the frozen regions of the North, will register about 38° C. The temperatiuT of the surface of his body varies with that of the air — a fact with which all are familiar — but the internal temperature is the same irrespective of whether it is winter or summer. What is true of man is true also of other mammals and of birds — that is, of those animals commonly denominated warm-l)looded. Poikilothermal animals are animals of varying heat, or those whose temperature varies according to that of the medium — air or water — in which tliey live. The frog's temperature is slightly above that of the water, and if this is warm, the temperature in the frog will rise, to fall again when the temperature of the water is lowered. Thus a frog with a temperature of 20.7° C. in water at 20.6° C. will have a temperature of 38° C. when that of the water is raised to 41° C. Fishes, reptiles, amphibia, and insects also exhibit this same variation of temperature, so that cold- blooded and poikilothermal are practically interchangeable terms. A study of insects shows that these creatures produce heat, the thermometer registering, in some experiments on butterflies in active motion, a temperature of 5 degrees C. above that of the air. These insects are poikilothermal. The same power of generating heat is observed also in plants. The amount of heat varies under different circumstances, being especially marked at the time of germination and flowering, sometimes from 5 degrees to 10 degrees C. above that of the air. Temperatures of DiflFerent Animals. — The following table gives the temperatures of some of the more common animals : Mammals. J Bi7^ds. Poikilothermal aniwah. Centigrade. Centigrade. Temperature above .surrounding medium Sheep . . 37.3°-40.o° Duck . . . 42..'i°-43.9° Fros; . . 0.32- 2.44 de£cree.s C Ape . . 3r).5°-39.7° Turkey . . 42.7° Snakes . 2.r)0-12.0 de2;rees C Dojr . . . 37.4°-39.f>° Chicken . 43.0° Fish . . 0.50- 3.0 degrees C Horse . . 36.8°-B7.5° Ox . . . 37.5° Temperature of Different Parts of the Body. — The tem- perature of the skin at the middle of the up]>er arm is 35.4° C, while in the sole of the foot it is but 32.26° C. In the axilla it is INSTANCES OF IIIGII AND L())V TKMPKRATrili:. 397 about 37.1° ('., altlioiiiih some observers have placed it as low as 3(3. '2o° C, ami others as hig-h as 37.5° C; under the toni) are situated in the lumljar region of the abdominal cavity, one on each side of the spinal column, with the upper border on a level with the twelfth dorsal, and the Fig. 238. — Longitudinal section through the kidney : 1. cortex ; 1', medullary rays; 1", labyrinth; 2, medulla; 2*. papillary portion of medulla; 2", boundary layer of medulla ; 3. transverse secrion of tubules in the boundary layer : 4, fat of renal sinus: 5. artery: * transverse medullary rays; A, branch of renal artery; C, renal calyx ; U, ureter (after Tyson and Henle). lower o])posite the third lumbar vertebra. The dimensions of each are approximately : Length, 10 cm. ; lireadth, 5 cm. ; thickness, 2.0 cm. The weight is from 125 to 180 grams. The shape of the kidney is like that of a bean, the internal PLATH IV. I ^.\ f0 A, A, rijibt and left kidneys; B. urinary bladder : C, C. right and left ureters; d, d, renal arteries (Maclise). KIDNEYS. 411 border being concave and ])resenting a fissure — the hilmn — at which the vessels, tiie nerves, and the ureter enter tiie organ. A\ hen the Ivichiey is longitudinally cut in two, it is seen to be made up of an external or cortical portion — cortex — and an in- ternal or niedullarv portion — lacdid/a. The medullary portion is made up of numerous pyramids (those of Malpighi), from 8 to 18 in number, and, dipping down between them, as well as forming the outer j)art of the kidney, is the cortical portion. Each pyra- mid terminates in a papilld pro- jecting into a calyx, which, with the calices of other pyramids, forms the pelvis, the upper dilated cavitv of the ureter. Tubuli Uriniferi (Figs. 239, 240). — At each papilla there open about 20 uriniferous tubules, which can be traced to the base of the pyramid. Each tubule continues into the cortical portion of the kidney, where it is larger and becomes convoluted, narrowing again and entering the pyramid, in which it again becomes straight, forms a loop, and re-enters the cortical portion, again becomes convoluted, and finally terminates in a spherical body, the Malpigli- ian capsule or capsule of Boicman. This complicated structure may, perhaps, be traced more easily in the opposite direction. Beginning with the Malpighian capsule in the cortical portion, there is next the convoluted tubule, which, as it passes into the medullary portion, becomes straight and is known as the " descending limb of Henle's loop." This bends on itself, forming the ascending limb, like- wise straight, passes back into the cortex, becomes convoluted, and enters a straight collecting tube which opens at the apex of a pyramid. The uriniferous tubules are lined with epithelium, which varies at different parts of their course. The epithelium w' hich lines the capsules and the neck, and which covers the glomerulus, is flattened, Fig. 239. — Diagram of two urinif- erous tubules : 1, Malpighian tuft surrounded by Bowman's capsule; 2, constriction or neck ; 3, proximal convoluted tubule ; 4, spiral tubule ; 5, descending limb of Henle's loop; 6, Henle's loop ; 7 and 8, ascending limb of Henle's loop ; 9, wavy part of ascending limb of Henle's loop : 10. irregular tubule ; 11, distal convoluted tubule ; 12, first part of collecting tube ; 13 and 14, straight part of col- lecting tube ; 15, excretory duct of Bellini (Tj-son and Brunton, after Klein and Noble Smith). 412 THE URINARY APPARATUS. and the cells have an oval nucleus (Fig, 241). This changes to a thick polyhedral epithelium, with a fibrillar or striated structure, in the proximal convoluted tubule and spiral tubule of Schachona. It is again Hat in the descending limb of Ilenle's loop, while in the ascending limb it resembles that of the spiral tubule. The epithelium in the irregular or zigzag tubule is angular and markedly Artery of capsule. •Arched collect- --. ing tubule. Straiglit col- lecting tu- bule. Distal convo- luted tu- bule. Malpighian c'orpu.scle. Proximal con- voluted tu- bule. Loop of Henle. Collecting tubule. Arteria arcua- ta. Large collect- ing tubule. Papillary duct, Glomer- ulus. Vena arcuata. Fig. 240. — Diagrammatic scheme of uriniferous tubules and blood-vessels of kidney ; drawn in part from the descriptions of Golubew (Bohm and DavidoflF). striated ; in the second convoluted tube it is like that in the first ; in the jimctional tubes, flat and cubical ; in the straight or collecting tubes, clear cubical and columnar ; and in the ducts of Bellini, clear columnar. The following table, from Sehjifer's Essentials of Histology, exhibits the differences in the epithelium of the tubules in a manner very useful for reference : KIDNEYS. 413 Portion of tubule. Capsule First convoluted tube . Spiral tube Small or descending) tube of Henle. . . . ) Loop of Henle Larger or ascending 1 tube of Henle. . . • j Zigzag tube Nature of epithelium. Position of tubule. Second convoluted tube Junctional tube .... Straight or collecting) tube J Duct of Bellini .... f Flattened, reflected overglomO I erulus. j I Cubical, librillated, the cells \ interlocking. ICubical, fibrillated (like the last Clour flattened cells. Like the last. f Cubical, tibrillated, sometimes | t imbricated. / (Cells strongly fibrillated ; 1 \ varying height ; lumen v ( small. ) ( Similar to first convoluted 1 tube, but cells are longer, i \ with larger nuclei, and they J- I have a more refractive as- | t pect. J Clear, flattened, and cubical cells. f Clear cubical and columnar ) I I cells. J Clear columnar cells. Labyrinth of cortex. Labyrinth of cortex. Medullary ray of cortex, f Boundary zone and partly \ papillary zone of medulla. PapiUarv'zone of medulla. fMeduUa'and medullary ray \ of cortex. Labyrinth of cortex. Labyrinth of cortex. f Labyrinth passing to medul- \ lary ray. Medullary ray and medulla. Opens at apex of papilla. Blood-vessels. — The renal artery (Fig. 238), which supplies the kidney, is a branch of the abdominal aorta, which before entering Fig. 241.— From section of cortical substance of human kidney : a, epithelium of Bowman's capsule ; b and d, membrana propria ; c, glomerular epithelium ; e, blood-vessels; /, lobe of the glomerulus; g, commencement of uriniferous tubule; h, epithelium of the neck; i, epithelium of proximal convoluted tubule; X 240 (Bohm and Davidoff). 414 THE URINARY APPARATUS. the organ subdivides into 4 or 5 vessels. It is from these vessels that the suprarenal capsules and tiie ureter also receive their blood-supply. When, as frequently happens, there is a second artery, it is called the inferior renal artery. The branches of the renal artery pass toward the cortex and end as proper renal arteries, arterice projyrice renales, from which are given oif the interlobular arteries in the direction of the cortical substance, and the arterioke rectce toward the medullary pyramids. From the interlobular arteries are given oiF the afferent Nuclei of en- dothelial cells of blood capillaries. Lumen of uri- niferous tu- bule. ■Striated bor- der. Fig. 242. — Section of proximal convoluted tubules from man ; X 580 (Bohm and Davidofl'). vessels, which pierce the capsules and end in the Malpighian tufts. From the capsules emerge the efferent vessels, which form a venous plexus about the uriniferous tubes, and the blood ultimately leaves the kidney l:>y the renal vein. Nerve-supply of the Kidney. — The nerves of the kidney, from 15 to 20 in number, have ganglia upon them, and are from the renal plexus. This plexus is formed from the solar plexus, semi- lunar ganglion, lesser and smallest splanchnic nerves. So far as known, the nerves are distributed to the arterioles principally, KfDXEYS. 415 though nerve-fibrils are described as nimifving among the cpithc- liiini of the tiibides. Function of the Kidneys. — The function of the ki(hieys is to form urine. Tills is sometimes spoUen of as a .secrdion, but inas- much as its constituents pre-exist in the blood when that fluid conies to the kidneys, and these organs simply remove these sub- stances from the blood, urine is more properly an excretion. The ingredients composing the urine may, from a physiologic stand- point, be divided into two groups: (1) Water and some of the salts ; and (2) urea, uric acid, and allied substances. The first group, consisting of water and salts, is eliminated from the blood while that fluid is passing through the glomerulus within Bowman's capsule, the beginning of the uriniferous tubules ; while the urea group is excreted while the blood is passing through the venous plexus surrounding the convoluted portions of the tubule. Excretion of Water and Salts. — While all authorities agree that it is at the glomeruli that water and some of the inorganic salts are eliminated from the blood, there is a diversity of opinion as to the factors engaged in this process ; some regarding it as a simple filtration in which the glomerular epithelium plays a passive part, while others attribute to these cells a very important part in the process. Whenever the renal blood-supply is increased, the quantity of urine is also increased, and it has therefore been assumed that this increase was due to the heightened blood-press- ure within the glomerulus, and this is the basis of the filtration theory ; but it has been pointed out that under these circumstances there is an increased blood-flow through the organ, and it is to this that Heidenhain attributes the increased secretion, rather than to the simple increase of pressure within the glomeruli. This authority is one of the principal exponents of the theory that the glomerular epithelium is the efficient agent in the elimination which takes place within Bowman's capsule. Bowman, in 1842, advanced the opinion that "the Malpighian bodies might be an apparatus destined to separate from the blood the w^atery portion " of the urine. On the other hand, he held that " the tubes and their plexus of capillaries were probably the parts concerned in the secretion of that portion of the urine to which its characteristic properties are due." In 1884 Ludwig expressed the opinion that all the constituents of the urine escape from the blood while passing through the glomeruli, and that this separation is due to the high pressure under which the blood is within these structures. Heidenhain combated the view of Ludwig on various grounds : Among others, that a rise of arterial presvsure elsewhere in the body, as in the salivary glands, does not cause increased transuda- tion through the walls of the blood-vessels ; that the epithelium 416 THE URINARY APPARATUS. covering the glomeruli would oifer great resistance to filtration ; that if the renal vein is ligated and the pressure within the glomeruli thereby increased, not only is the flow of urine not in- creased, but it is actually abolished; and, finally, that filtration will not explain the increased flow of urine when water and crys- talloid substances are increased in the blood. Heidenhain, as already stated, believes that the cells of the glomerular epithelium act as secretory cells do elsewhere, and by the power which they possess as living cells eliminate water and inorganic salts, espe- cially sodium chlorid, from the blood. In commenting on these opinions, Starling, to whose admirable article on " The Mechanism of the Secretion of the Urine," in Schiifer's Text-book of Physiology, we are much indebted, says : " It seems probable that in the glomeruli the process is largely if not exclusively physical," and that '* we have at present no evi- dence that the cellular covering of the glomeruli acts otherwise than passively in the production of the glomerular part of the secre- tion." He also refers to the researches of ]Munk and Senator, who have reached the conclusion that water and part of the urinary salts, especially sodium chlorid, are transuded through the glomeruli in direct consequence of the blood-pressure — i. e., by a process of fil- tration, although the rapidity of the blood-flow is equally important. It is also generally accepted that when serum-albumin, hemo- globin, or dextrose escapes from the blood and l)eeomes a constitu- ent part of the urine, this takes place while the blood is passing through the glomeruli. The oncometer (p. 327) has been largely used in connection with the various experiments which have been conducted to deter- mine the effects of increased and diminished blood-pressure on the excretion of urine by the kidney. Excretion of Urea, Uric Acid, etc. — Bowman, in his views as to the manner of the formation of urine, expressed the opinion that the tubes and their plexus of capillaries were probably the parts concerned in the secretion of the substances forming this second group of urinary constituents, and this is the generally accepted view of the authorities of the present day. It is also probably true that some water, sodium chlorid, sulphates, and phosphates are eliminated from the blood in this part of its course through the kidney. The efficient agents in this elimination are the cells lining the tubules, and especially those in the convoluted portions. Effects of Removal of the Kidneys. — Removal of a single kidney for a diseased condition of that organ, constituting nepJirectomif, is not an uncommon operation at the present day. After the operation the remaining kidney enlarges and performs the func- tions of both. Removal of both kidneys is followed by a fatal result. URETERS. 417 Ureters. — Vnnw cucli kidney passes a ureter, a tube which conneets the kichicy w itii tiie hhukler, and tiirouij^h wiiich tlie urine is discharged. It has a diameter about that of" a goose-quill and a length of about 40.G cm. It has 3 coats : External or fibrous; middle or nitiscu/a)' ; and internal or mucous. The mnscular tissue is of the plain variety and arranged in 2 layers: longitudinal and circular ; a third layer, also longitudinal, is found near the bladder. The mucous meinbrane is covered with transi- tioHdl epithelium (p. 34). \\4ien the ureters reach the base of the bladder, they pass for about 2 ora. between the muscular and mucous coats, and then open by a constricted orifice in the bladder. Function of the Ureters. — The urine which is being constantly formed by the kidneys passes into their pelves, and by peristaltic action of the muscular coat of the ureters is carried to the bladder, into which it flows intermittently. The actual entrance of the urine has been observed in a case of ectopia vesicee in a boy. This condition consists in a deficiency in the abdominal wall and in the front wall of the bladder, so that the openings of the ureters. Fig. 243. — Casper's ureter cystoscope : li, movable lid covering groove in which moves c, the ureteral catheter ; d, handle of lid ; o, ocular end ; p, prism ; I, lamp, s, screw for making and breaking connection with the battery ; m, mandril. can be inspected. In this case the flow of urine into the blad- der was intermittent, and about the same in amount for each ureter. By means of the cystoscope (Fig. 243) it has been determined that the peristaltic action of the ureters is both intermittent and alternate ; exceptionally it may be synchronous. At intervals of a minute or more urine is discharged from the ureters into the bladder, the amount varying ; but averaging, perhaps, from 1 5 to 30 drops. The cause of this peristaltic contraction is not definitely deter- mined. Some authorities attribute it to the direct stimulation of the muscular tissue by the accumulated urine, which results in a wave which is propagated from one muscle-cell to another ; while others think that this contractility of the musculature of the ureters is a power possessed by it independent of any direct stim« ulation, either mechanical or nervous. Experiments upon the rat have demonstrated that when the ureter is cut into several pieces, each section will contract peristaltically. 27 418 THE URINARY APPARATUS. Bladder (Fig. 244). — This is not infrequently spoken of as the urinary bladder, and when moderately distended will contain about \ liter ; though it may be so distended as to contain very much more than this. It has 4 coats : peritoneal or serous, muscular, submucous, and mucous. The muscular coat is made up of 3 layers of plain muscular fiber : External or longitudinal, middle or circular, and internal, which is also longitudinal. The external longitudinal layer is also described as the detrusor urince muscle, and the aggre- Fig. 244. — Section of penis, bladder, etc.: 1, symphysis pubis; 2, prevesical space; 3, abdominal wall; 4, bladder; 5, urachus; 6, seminal vesicle and vas deferens; 7, prostate ; 8, plexus of Santorini ; 9, sphincter vesicae; 10, suspensory ligament of penis; 11, penis in flaccid condition ; 12, penis in state of erection ; 13, glans penis; 14, bulb of urethra; 15, cul-de-sac of bulb, a, Prostatic urethra; 6, membranous urethra; c, spongy urethra (Testut). gation of the fibers of the circular layer around the neck of the bladder and the beginning of the urethra, as the sphincter vesicce. The mucous coat or mucous membrane is covered with transitional epithelium, and contains racemose glands. Nerve-supply. — The nerves supplying the bladder are, according to Langley and Anderson, derived from (1) the second to the fifth lumbar nerves, reaching the organ through the sympathetic chain, the inferior mesenteric ganglion, and the hypogastric nerves ; (2) the second and third sacral spinal nerves. Stimulation of the URETHRA. 419 iirst i^rouj) causes feeble, and of the seeoiul strong, contraction of the bhuhh'r. Function of the Bladder. — Tlie bladder acts as a reservoir for the urine until such time as it is passed in the act of urination or micturition. The urine is retained within the bladder by the tonic contraction of the spliincter vesicie in the same manner as feces are retained in the rectum by the sphincter ani. The pressure of the urine when the bladder is full is equal to only 1 cm. of mer- curv, while it takes a pressure of at least 3 cm. to overcome the elasticity of the sphincter. When the bladder is about to be emptied, as the result of an inhibitory impulse, the sphincter vesicae becomes relaxed. At the same time the muscular coat of the bladder and the abdominal muscles contract, and the urine begins to flow. The pressure which is thus exerted equals 10 cm. of mercury. Although the starting of the act is voluntary, when once it has begun it continues under the influence of the vesico- spinal center situated in the lumbar part of the cord until the bladder is empty. Up to a certain point the i)rain is able to inhibit the center and postpone the evacuation of the bladder, but after a time, if too long delayed, the resistance of the sphincter is overcome and urine will flow. It is more difficult to stop the act after it has once begun than to delay its beginning, for the urine, flowing over the mucous membrane of the urethra, stimulates the vesicospinal center, and the efferent impulses to the contracting muscles are increased. If the mucous membrane of the bladder is inflamed, as in cystitis, the stimulation of the center may be so great as to pre- vent the brain from inhibiting the evacuation, and this may occur when only a small quantity of urine is accumulated. Or it may happen that the spinal cord is injured or diseased in the upper or middle portion, and thus all sensation caused by a full bladder may be abolished. Under these circumstances the bladder, when fuli, will be emptied by the reflex action of the vesicospinal center. Or, again, if the lesion of the cord is such as to disorganize this center, then there will be no reflex action of the cord, and the elasticity of the tissues about the neck of the bladder will keep the urine in that viscus until the elasticity is overcome by the disten- tion, when the urine will flow in drops as fast as it comes from the kidneys ; but the bladder will not empty itself. Inexperi- enced persons are often deceived by this dribbling of the urine, thinking that its discharge is evidence that the bladder is perform- ing its duty, while the fact is that it is evidence of paralysis and retention. Urethra (Fig. 244). — This canal extends from the neck of the l)ladder to the meatus urinarius, and in the male is about 20.4 cm. and in the female about 3.7 cm. in leng-th. It is lined with 420 THE URINE. mucous membrane, in which are mucous glands, glands of Littre, and opening into it in the male are two compound racemose glands, Cowper^s glands. In the female urethra the epithelium is stratified. In the male urethra it is stratified near the meatus, transitional in the prostatic portion, and elsewhere columnar. THE URINE. Quantity. — The amount of urine voided by an adult in twenty -four hours is about 1500 c.c, although it may vary within normal limits from 1200 c.c. to 1700 c.c. In health the increased drinking of fluids and lessened formation of the perspiration will increase the amount of urine excreted, while the excretion will be diminished if the quantity of liquids drank is lessened or if the perspiratory glands are more active. It is a matter of common observation that in summer the urinary flow is less than it is in winter. Color. — The color is ordinarily yellow, though it may be, even in health, almost colorless or reddish brown. The urinary pigments are urochrome, urobilin, uroerythrin, and hematopor- phyrin. Urochrome. — This is the essential pigment to which the yellow color is due. It has been demonstrated that when alcoholic solu- tions of pure urochrome are treated with aldehyd a reducing action is produced on the pigment and urobilin is produced. This would indicate that urochrome is an oxidation-product of urobilin. Urobilin. — This is the same as stercobilin of the feces, and is probably formed from the bilirubin of the l)ile. Urobilin exists in small amount in the urine, and principally in the form of a chromogen, to which the name urohUlnngen has been given. Uro- bilin and hydrobilirubinare regarded by some as identical. Hop- kins states that the origin of urinary Ijilirubin is probably three- fold — from absorption of the ready-formed ])igment in the bowel ; from direct production in the liver ; and from reduction of the blood-pigment in the organ, independently of hepatic agency. Uroerythrin. — This coloring-matter is that Avhich gives the characteristic color to the pinkish deposits of urates. It exists in small amount, but it is always present in normal urine. Hematoporphyrin. — Although normally present in but small amount, this substance may exist pathologically in considerable quantity. Reaction. — The reaction of the mixed urine passed in twenty- four hours is acid to litmus, due to the presence of sodium dihy- drogen phosphate, NaHjPO^, or, as it is more commonly called, acid sodium phosphate. The acidity of the urine is subject to considerable variation. It is increased after exercise and after the consumption of animal COMPOSITION OF THE URINE. 421 food ; it is decreased alu-r the ingestion of vegetable food, because this contains compounds of organic acids which by oxidaticjn form carbonates, and these latter may be so plentiful as to make the urine alkaline. . The alkdUnc tide is a term applied to the condition ni which during the period when hydrochloric acid is being set free as a constiUient of the gastric juiee the urine, through the elimination from the blood of the bases, becomes less acid and sometimes even alkaline. • There is also a diifcrence in the degree of acidity of the urine at different times of the dav, without regard to the food taken. Specific Gravity.— This varies from 1015 to 1025, being lower when the quantity of urine is increased, and higher when it is diminished. It mav, in extreme cases, as after the drinking of large quantities of fliud, be as low as 1005. In diseased condi- tions, as in diabetes mellitus, the quantity is greatly increased and this is accompanied bv a high specific gravity. Composition.— in the following table are given two analyses bv Bunge of the twentv-four hours' mixed urine of a young man : The "nteat diet" consisted of beef with a little salt and spring- water ; the " bread diet " consisted of bread, butter, and water : Meat diet. Bread diet. Total quantitv in twentv-four hours . 1672 c.c. 1920 c.c. TTrPT ^ ' . . 67.2 ^rams 20.3 grams Creatinin .' ." .' .■.".■:: 2.163 " 0.961 - Uric acid 1-398 " 9.253 || Sulphuric acid (total) 4.674 " 1.265 '' Phospho™ acid . 3.437 " I.608 LinJ P-328 " 0.339 Magnesia 0.294 " 0.139 Potash 3.308 " 1-314 " Soda^ : 3.391 " 3.923 " Chlorin 3.817 " 4.996 " The urine of an adult living upon an ordinary mixed diet and amounting in the twenty-four hours to 1500 c.c. would contain approximately 1440 c.c. of water and 60 grams of solids, of which 35 grams would be urea. Urea, CO(NH„).,.— Chemically this substance is an amid ot carbonic acid, and' fs also described under the name carbamid. It is isomeric with ammonium cvanate, (NHJCXO, and was pre- pared therefrom bv Wohler in 1828. It crystallizes in the form of colorless needles or rhombic pri.sms ; is soluble in water and alcohol, but is insoluble in ether and chloroform With nitric acid, urea becomes urea nitrate, CO^MI,),^ 0.,UH , which forms in its crvstallization rhombic tables ; the angles of these are usiiallv cut' oif, making six-sided crystals, which fre- quently overla]) one another. The formation of these crystals is used as a test for urea. 422 THE URINE. With oxalic acid urea forms urea oxalate, CO(XH2)2(COOH)2, which crystallizes as short rhombic prisms. Urea is convertetl into ammonium carbonate by the action of the ferment Micrococcus urece ; this change Avhich takes place in urine declares itself hy the aramoniacal odor which is developed. It is represented by the following equation : CO(NH2)2 + 2H2O = (NH,)2C03 Urea. Water. Ammonium carbonate. Urea is the end-product of the proteid metabolism of the body and of the albuminoids of the food. When a meal containing considerable proteids has been ingested, and the urea determined, the amount will be at a maximum at the third or fourth hour ; this is supposed to indicate the absorption of peptones from the stomach. A second maximum occurs at the sixth or seventh hour, and this is attributed to the absorption of peptones from the intestine. Formation of Urea. — Urea exists in the blood when that fluid reaches the kidney, and the function of this organ is, so far as urea is concerned, simply to eliminate it. Without recounting the experimental evidence, which is ample and satisfactory, it is enough to say that urea is formed by the cells of the liver. The most satisfactory explanation of the manner of this formation is that given by Drechsel, and is substantially as follows : Proteids undergo hydrolytic cleavage, and leucin, tyrosin, aspartic acid, and other amido-bodies are formed : these undergo oxidation, forming NH3, CO2, and H.,0 ; NH3 and CO2 unite to form ammonium carbonate, COCH I II )C0 HN— C — X ^ HX — C — XH^ Guanin. Uric acid. HX— CO I I OC C— XH^ I li >CH HX — C — X ^ Xanlhin. " Purin, as has been shown by E. Fischer, has the formula : X=CH I I HC C— XH- II II >CH X — C — X ^ " The purin bases and uric acid are derived from purin by simple substitution of the various hydrogen atoms by hydroxy!, amid, or alkyl groups, as is plainly evident from comparison of the different formulae. "Secondly, it must be noted that all true nuoleins on decompo- sition by chemical means yield more or less of the above purin bases, as was first pointed out by Kossel. This means that all nucleins contain in their molecules some purin bases — /. f., in a state of combination, from which combination they can be split off by appropriate means either in the body or by chemical methods outside of the body. Further, as these nuclein or purin bases stand in such close relationship to cell-nuclei, it is easy to see how the quantity of these substances may he largely increased "whenever from any cause the number of nucleated cells is increased in any part of the body. Thus, while normal blood yields only traces of purin bases, in leukemia the amount of nuclein bases may be increased to over 0.1 per cent." COMPOSITIoy OF THE URIXE. 42o Prof. Chittenden concludes his admirable paper in the follow- ing languaire : " In man uric aciil has a twofold origin ; one portion, coming from the breaking down of nuclein-containing tissues or cell- elements of the man's own body, and hence is of endogenous origin, while the other portion — usually the larger — is of exogen- ous origin, coming from the transformation of free and combined purin compounds present in the food. Tlie uric acid of endogen- ous origin is essentially constant in amount for the same indi- vidual under all conditions of diet, but is subject to slight varia- tion in connection with alterations in the activity of the tissues. Changed conditions embodying increased katabolism of the tissue- elements, increased breaking down of cells and cell-nuclei, might naturally be expected to cause slight alteration in the amount of endogenous uric acid, but analytic results at present do not justify belief in any profound changes in the uric acid output due to this cause. The amount of endogenous uric acid is, therefore, a physiologic constant for a given individual, and, as might be ex- pected, decided variations are to be found in the value of this constant for different individuals. In other words, personal idio- syncrasy, constitutional differences, etc., may manifest themselves in the amount of endogenous uric acid produced. Such a condition of things is by no means strange or out of harmony with physio- logic laws. There is a personality in every man, internal as well as external, and the individual constancy in endogenous uric acid production is merely another illustration of the general truth of this law. Individual functional peculiarities are as liable to existence as personal peculiarities of form and structure. " The amount of exogenous uric acid produced in the body is dependent mainly upon two factors, viz., the quantity and char- acter of the nucleins contained in the ingested food, and the quantity and character of the free purin bases present in the food. . The nucleins owe their influence solely to the combined purin bases they contain, and since nucleins from different glands and tissues differ both in the amount and character of the purin bases present in their molecules, it follows naturally that the individual nuclein-containing foods have different values as sources of exogen- ous uric acid. Further, since all nucleins are somewhat slowly attacked by the digestive fluids, it follows that the uric acid coming from this source does not appear at once in the urine, but is found some hours after digestion has been under way. The free purin bases, on the other hand, such as are contained in meats, meat-juice, meat-extracts and soups, coffee, cocoa, etc.. lead to a quicker output of uric acid, owing to their ready solubility and availability. Differences in the extent of this form of exogenous uric acid production, however, are traceable to differences in the nature of the free purin bases ; adenin, hypoxanthin, and guanin, 426 THE URINE. for example, showing distinct differences in the extent to which they are individually converted into uric acid in the body. '' Finally, we see that there is no cau«d relationship whatever between the daily urea and uric acid output. They come from totally different lines of metabolism ; they stand for totally dis- tinct chemico-physiologic processes ; and hence any attempt to emphasize the so-called ratio of urea to uric acid in the urine is misleading, and shows, furthermore, a lack of understanding of the true genesis of these two excretory products. Between uric acid and ordinary })roteid metai)olism there is no connection what- ever. With a purely jion-nitrogenous diet, on the one hand, and a diet rich in eggs, milk, and cheese, on the other, with perhaps a maximum amount of contained proteid, the output of uric acid remains practically unchanged. The genesis of uric acid is to be found solely in metabolism of the tissue nucleins (endogenous) and in the transformation of the nucleins and free purin bases of the ingested foods (exogenous)." Xantliin Bases. — The urine contains besides xanthin, the follow- ing members of this group : Meteroxanthin, paraxanihin, hypo- xcmthin, gruinin, adenin, and carnin. Tliey are related to uric acid, as is shown by the formulse given on page 424, and these bases and uric acid are called by Kriiger and V\\\\\X (lUox^iric sub.stanccs, because of their relation to alloxan and urea. The amount of the xanthin bases daily excreted in the urine is about 0.1 gram. They are increased after taking green vegetables and on a diet contain- ing much nucleins, and also in some form of leukemia, Hippuric Acid (CgHj.NOj). — Although present in herbivora in considerable amount — 2 per cent, in cattle — hippuric acid occurs in human nrine on an ordinary diet to the amount of but about 0.7 gram per diem, being increased three or four times this amount if fruits enter largely into the diet. Creatinin. — This substance exists in human urine under a mixed diet to the extent of al)0ut 1 gram in the twenty-four hours. Its principal source is the creatin contained in the meat ingested, as is represented by the following equation : C.HgNgO^ - HP = C.H.NjO Creatin. Water. Creatinin. It is possible that some of the creatinin in the urine may come from the creatin of the muscular tissue of the body, although this is not established. Proteids. — In the urine is a minute quantity of a nucleoproteid from the cells lining the urinary passages. This may be present in sufficient quantity to react to Heller's test, which consists in allowing urine to flow down the side of a test-tube in which is strong nitric acid. The urine floats on the acid, and where the PEPTONURIA AXD ALBUMOSURIA. 427 two join a white ring of coagulated protcid forms. In n/diiis, an inHannuation of the mucous membrane lining the bladder, the quantity of the nucleoproteid may he increased, and tiiis is precip- itated when acetic acid is added to the urine. The nucleo- proteitl of the urine is also increased in leukemia. Albuminuria. — Under some circumstances serum-albumin and serum-globulin are found in the urine, constituting albvminurid. These doubtless always exist in minute quantities in health, but may come from the cells of the passages along which the urine travels, and not from the blood as it flows through the glomeruli, as they undoubtedly do in true albuminuria, which is a patho- logic condition. Peptonuria and Albumosuria. — These conditions are character- ized by the presence in the urine of peptones and albumoses, respectively. We have already seen that the products of digestion, peptones, are changed in their passage through the gastric and iiitestinal walls by the cells into, probably, serum-albumin and serum-globulin ; certainly, they do not enter the blood as peptones. If either wall is much diseased, as in cancer of the stomach, the peptones and albumoses or proteoses may not be changed, but may enter the blood in these forms and appear in the urine, being eliminated by the kidneys. It is probably in the form of albumoses or proteoses rather than peptones that this elimination takes place. This condition of peptonuria may occur in connec- tion with abscesses or collections of pus, the pus-cells having broken down, and pe])tone being one of the products which is taken up by the blood and carried to the kidneys, where it is eliminated. Aromatic Substances. — Hippuric acid or benzamido-acetic acid belongs to the aromatic series, by reason of its containing the benzene nucleus. Besides this, there are other aromatic substances which come from the food and also from the proteids of the tissues. Among these are phenol, kresol, pi/rocafechin, sometimes inosit, and various carboxi/acids. Indo.ryl, which is produced by the oxida- tion of the indol that is absorbed from the intestine, and sk(doxi/l, produced in the same manner from skatol, also occur in urine. Dextrose. — Ordinary urine contains dextrose to the amount of from 0.08 to 0.18 gram per diem. The presence of dextrose in normal urine has been and still is denied, but the most recent investigations seem to leave no doubt upon this much mooted question. We have seen that alimentary glycosuria may occur when an excessive amount of sugar is ingested. In diabetes mellititt, the quantity of dextrose in the urine may be very great, 500 or 600 grams being excreted in a single day. The methods of recognizing the presence of dextrose have been previously referred to (p. 87). 428 THE URINE. Lactose. — The presence of this variety of sugar in the urine constitutes lactosuria, and this condition of the nursing mother's urine is quite constant. Lactose is formed l)y the mammary gland, absorbed by the blood, and eliminated by the kidneys. It must be inverted before it can be changed into glycogen ; this inversion takes place when lactose is ingested with the food, but when absorbed by the blood from the mammary gland, it does not occur. Under these circumstances lactose enters the blood directly as lactose and is excreted in the urine. Lactosuria is a condition which has escaped general recognition, and in speaking of it Hopkins says : *' If the urine exhibits the following characters, the presence of lactose is established almo-st without the possibility of doubt : It should reduce copper and bismuth solution; but with the fermentation-test, it should give negative results for the first twenty-four hours of the experiment, and it should give no definite crystalline precipitate with the phenylhydrazin test when this is directly applied. On the other hand, after boiling with 5 per cent, sulphuric acid for a short time the urine should, if first neutralized with ammonia, give the phenylhydrazin test readily : crystals of dextrosazon shoukl be thus obtained, and with proper precautions galactosazon crystals may also be distinguished. Although the lactose is converted bv the mineral acid into dextrose and galactose, fermentation is not always to be obtained after treatment, as the large amount of sulphate which is present after neutralizing the acid interferes with the growth of the yeast. If the reducing power of the urine is estimated, this should be found increased after boiling with mineral acid, but unaflPected by boiling with citric acid." Inorganic Constituents. — The inorganic ingredients which occur in the urine are mainly in the form of chlorids, phosphates, sulphates, and carbonates, combined with sodium, potassium, ammonium, calcium, and magnesium, and are excreted to the amount of about 25 grams per diem, of which about 15 grams are sodium chlorid, derived almost exclusively from that taken in with the food. The inorganic constituents eliminated in the urine come from (1) the inorganic constituents of the food, and (2) from the de- structive metabolism of the body -tissues. In the first group are the chlorids and the principal part of the phosphates ; in the second, the sulphates, which occur in but small quantities in the food, and a small part of the phosphates. Chlorids. — Although the urine contains some potassium chlorid, it is mainly by sodium chlorid that these salts are represented. Inasmuch as its quantity in the urine depends upon that taken in with the food, this is subject to considerable variation. In disease any process which results in taking sodium chlorid from the blood will correspondingly diminish its excretion in the urine; INORGANIC CONSTITUENTS. 429 tliis occurs in the exiKlutions which accompany pneumonia and plenrisv. \\ hen the.se are absorbed, the chlorid of sodium again enters the blood and the quantity in the urine is increased. Phosphates. — In the metal)olism of the tissues of tlie body some of tile phosphorus contained in uuclein, lecithin, and prota- gon is oxidized, producing phosphoric acid, which in the form of phosphates is excreted in the urine; the amount of this is, how- ever, small. Most of these salts which occur in the urine arc derived from the food ; hence their quantity is increased with an animal diet, while with a vegetalde diet it is diminished. The phosphates of plants are not absorbed by the animal, because of their insolubility, hence in the urine of herbivorous animals these salts are deficient. The amount of phosphoric acid daily excreted in human urine is about 3.5 grams. The phosphates exist in two forms : (1 ) Alkaline and (2) earthy. The alkaline phosphates arc those of sodium and potas- sium ; while the earthy phosphates are those of calcium and mag- nesium. Sodium dihydrogen phosphate, also called acid sodium phos- phate, XaHoPO^, is the principal factor in giving urine its acid reaction, although associated with it in this office is calcium dihydrogen phosphate, CafHjPOjo- ^Vhen the reaction of the urine is neutral there are also present disodium hydrogen phos- phate, XaoHPO^, calcium hydrogen phosphate, CaHPO^, and mag- nesium hydrogen phosphate, MgHPO^. AVhen the urine is allca- line these may also be present, accompanied by the normal phos- phates, XagPO^, Ca3(POj2, ^ig3(P04)2j or these latter may replace the former. When the urine becomes alkaline, "whether as a result of the decomposition of urea and the formation of ammonium car- bonate or by the addition of ammonia, the earthy phosphates are precipitated. From alkaline decomposing urine, crystals of ammonia- magnesium phosphate, magnesium ammonium jyhosphate, or triple phosphates, by all of which names they are known, are deposited. The chemical formula of this deposit is XH^MgPO^ + 6H2O. It forms coMn-lid crystals or star-shaped figures. Urine that is slightly acid deposits star-shaped masses of prisms of calcium phosphate, called from the form of the crystals stellar phosphates. Sulphates. — Only a small quantity of the sulphates comes from the food, mo.st of it being the result of the metabolism of the proteids of the body, into which sulphur enters as a component part. These salts occur in the urine in two forms : (1) Inorganic sulphates and (2) ethereal or conjugated sv.lpjhates. The total amount of sulphates daily excreted in the urine varies from 1.5 grams to 3 grams, of which about one-tenth is in the form of the conjugated sulphates. The conjugated sulphates consist of radicles derived 430 MUSCLE PHEyOMENA. from the aromatic substances present in the urine, joined with sulphuric acid, from which fact they derive their name. Among the most important of tlic ethereal sulphates are phenol-potassium sulphate and indoxyl-potassium sulphate : besides these are kresol- potassium sulphate, skatoxyl-potassium sulphate, etc. These salts are increased when the putrefaction of proteid substances in the intestines is increased. Whenever, therefore, the amount of sulphuric acid in the urine is increased, it may be due to an in- creased amount of sulphates in the food or drink, or to increased putrefaction in the intestines. There is, according to Hopkins, also some sulphur in the urine in the form of neutral sulphur, as contradistinguished from the "acid sulphur" of the sulphates. It is in a less oxidized form than the sulphates, but what the compounds are is not kn(jwn. It is said that one-fifth of the total sulphur of the urine is in this form. Some of this may come from the taurin of the bile. Carbonates. — AVhen the urine is alkaline, sodium, calcium, mag- nesium, and ammonium carbonates are present. These are espe- cially abundant after a vegetable diet, for the reason that the malates, tartrates, and citrates contained in such food are con- verted into carbonates, which are eliminated by the kidnevs. Carl)onic acid also exists in acid urines, as much as 50 c.c. per liter having been found j^resent. IRRITABE,ITY; CONTRACTILITY; ELECTRIC PHENOMENA OF MUSCLE. Irritability is the property possessed by living tissues by virtue of which they respond to certain external agents called irritants or stimuli. A stimulus, therefore, is an agent which is capaljle of producing in living tissues certain changes by which is manifested the fact that they are living, the character of these changes varving according to the tissue which is the subject of the stimulation. When this change consists in one of form, it is contractility. Thus, simple protoplasm, as in the ameba, will, when touched, draw in the processes or pseudopodia which it had previouslv put out (p. 24). Here the touch was the stimulus which caused the irritability of the ]-)rotoplasm to manifest itself by contraction. Or if a muscle is stimulated by an electric current, it shortens, thus manifesting its irritability by contraction. In both these instances the response to the stimulus is a change of form. If, however, a current of electricity is passed through a nerve, the closest inspection fails to reveal any change in the nerve itself: it neither moves its position nor in any wise changes its form ; and yet a nerve is irritable — /. e., has the property of responding to a stimulus. If it is a motor nerve — that is, one distributed to a muscle — when it is stimulated its contractility will be mani- IRRITAIIIIJTY. 431 fested by a contraction of that muscle ; or if it is a secretory- nerve — tiiat is, one supplying a gland — its irritability will be manifested by an increased activity of the gland. It is not, however, essential that in order to manifest contrac- tilitv muscles should be stimulated through the motor nerve which is distributed to them, as a stimulus applied directly to the muscle itself will cause the muscle to contract. That muscular tissue pos- sesses irritability independently of the nerves distributed to it was for a long time in dispute, but is now conceded by all authorities, the proof which was furnished by Claude Bernard's experiment being incontrovertible. This consists in destroying the brain of a frog by pithing it — /. e., passing a blunt needle into the cranial cavity and moving it about. This destroys consciousness ; but the circidation of blood continues. The left sciatic nerve is then dissected out, and a ligature passed beneath it, and all the tissues of the thigh excepting the nerve are tightly tied : thus is cut off the blood-supply to all the parts below the ligature ; but the nerve is at the same time uninjured. Under the skin of the back a few drops of a 2 per cent, solution of curare are then injected. If after some time, about half an hour, the nerve is stimulated, there will be no contraction of the muscles supplied by it ; but if the stimulus is applied directly to the muscles, they will respond. Experiment shows that curare poisons the motor end-plates, so that although the nerve carries the current to this end-organ, its influence can pass no farther. . It has also been demonstrated that muscular tissue in which there are no nerves will respond to stimuli ; so that of the existence of independent muscular irritability there is no doubt. Stimuli. — Stimuli may be general or special. General Stimuli. — These are electrical, chemical, mechanical, and thermic. A current of electricity will stimulate a muscle or a nerve; certain chemicals will also stimulate them; but there are some of these agents which will stimulate a nerve and not a muscle ; still others will stimulate a muscle and produce no effect upon a nerve. A blow will stimulate either a muscle or a nerve, and is an instance of a mechanic stimulus, and heat or cold suddenly applied will cause a response in either. Special stimuli are those whose influence is restricted to a single nervous apparatus; thus light affects only the retina; sound- waves, only the organ of Corti ; and the senses of smell and taste require special stimuli to excite them. The manner in w^hich stimuli act is not thoroughly understood. It is compared by Sir William Gowers to the blow that explodes dynamite or the match which ignites a mass of gunpowder. Although any of the stimuli above mentioned may be used to demonstrate irritability and to study it, still it has been fonnd that the most reliable and satisfactory results are obtained when an 432 MUSCLE PHENOMENA. electric stimulus is used, as this is more readily controlled and measured than any of the other varieties of stimuli, and for this purpose a musele-n^rve preparation is made (Fig. 245). It consists of the gastrocnemius muscle of a frog with the sciatic nerve attached, a portion of the bone being also removed by which it may l)e clamped in an appropriate holder, Tiie electric current may be applied to the muscle directly, constituting direct stimula- tion, or to the nerve through which it passes to the muscle, indirect stimulation ; the result in either case being a shortening or con- traction of the muscle, which may be made manifest by some device attached to the tendon of the muscle. Battery. — For the generation of the current the Daniell cell (Fig. 246) is the one best adapted and most commonly employed. In it polarization is prevented and its constancy is very great. Polarization consists in a diminution in the intensitv of the cur- FlG. 245. — Experiment for determining the irritabilitv of nerves. Fig. 246.— Daniell cell. rent, caused by a film of hydrogen which forms on the copper plate. The Daniell cell consists of a glass jar holding dilute sulphuric acid or a solution of copper sulphate, in which is a sheet of copper of a cylindric form. Within the latter is a porous jar containing a solu- tion of zinc sulphate, within which is a zinc prism. To keep the solution of copper sulphate .saturated, crystals of this salt are placed in a perforated pocket attached to the copper plate. The action of the sulphuric acid upon the zinc results in chemical changes by which a current of electricity is generated when the zinc and copper are metallically connected. The current within the cell flows from the zinc to the copper, while outside it flows from the copper to the zinc. The zinc is the positive plate, and the copper the negative : but the end of the wire wdiich is connected with the copper is the po.dtive pole or anode, and that connected with the zinc plate is the negative pole or kathode. When the unattached ends of these wires connecting the zinc and the copper are brought into contact with IRRITAinUTY. 433 a norve a current of electricity flows through the nerve, the direc- tion being from the anode to the kathode. The wires are also termed tledrodes, thougii this term is more commonlv ap})lied to the terminations of the wires attached to suitable holders. When the electrodes are brought into communication through the inter- vening nerve the circuit is closed, and a contraction of the muscle occurs ; v/hen one of them, or both, is removed from the nerve the circuit is broken, and another contraction follows ; or the same results will follow if the muscle is directly stimulated without the intervention of the nerve. Keys. — A more convenient method of stimulating a nerve or muscle is by placing the one or the other upon the electrodes, which are not connected directly, but through the intermediarv of a key. When the key is open the circuit is broken, and when it is closed the circuit is also closed and a current passes. The closing of the key is make; its opening, breah ; these be- ing abbreviated expressions to imply that the circuit is closed or made, and open or broken. Du Bois-Reymond Key (Fig. 247).— By this key the circuit may be either closed or the current short- circuited. In Fig. 248 these two methods of the use of the key are shown. At a the current is passing through the nerve because the key is closed, and at b it is not so passing, because the key is open. M^hen used in the manner shown at c and dthe battery is at all times connected with the electrodes which are in connection with the nerve, so that the current is at all times taking this path Avhen the key is open at d ; but when the key is closed, as at e, the key oifering less resist- ance than the nerve, the current takes the short path through the key, and none of it, or so little as not to be worth considering, passes through the nerve. It is at the make and break that muscular contractions occur, and then only ; the contraction being stronger when the circuit is closed than when it is opened. It has been demonstrated that if a current is permitted to pass through a nerve, and gradually increased, and again gradually decreased, no contraction of the attached muscle occurs ; the make and break must be sudden. Induced Current. — This is a more powerful stimulus to the 28 Fig. 247.— Electric key. 434 MUSCLE PHENOMENA. nerves than the galvanic current produced in a voltaic cell, such as that of Daniell. In Fig. 249, 6 represents a battery the current of which can be permitted to pass or not through the primary coil p by closing or opening the key k. If near this coil a secondary coil, s, is Fig. 248. — Electric circuiting. placed, with its electrodes connected with a muscle, at the moment the key /; is closed in the primary circuit a current is in- duced in the secondary coil, which is manifested by a contraction of the muscle. The effect upon the muscle is brief, and it returns Fig. 249. — Schema of induction apparatus. to its former condition, and so long as the current is flowing no further change takes place in it ; but the moment the primary current is broken the muscle again contracts, because of the pro- duction of another induced current. It will be recalled that with the direct battery current the closing of the circuit, or the make^ IRRITABILITY. 435 produced the greater effect upon the muscle ; in the incUiced current it is the break which proihices the more powerful shock. Dh Jtois-R('t/mo)t, the cross-wires have been removed, and, as shown hy the diagram, the current can he sent through c and d to one part of the nerve, or through e and /to another, by rocking the bridge hack and forth. Myographs. — In order properly to study the effects of the Fig. 254. — Method of recording muscular contraction (Lombard). induction shocks upon the nerves and muscles it is necessary to have some method of recording the movements of the muscles which these shocks produce. Such an instrument is the myograph. The nerve-muscle preparation has already been described. The tendon of the muscle is attached to a lever, and to this latter is attached a writing-point, which rests against a piece of paper wrapped around a revolving drum, the paper revolving with the drum. When the muscle contracts, it raises the lever and an upward line is made by the point on the paper ; when the muscle relaxes, the lever falls and the point makes a descending line. Inasmuch as this drum is revolving all the time, these lines take the form of curves. Such a record is a myogram or muscle-curve, and may be preserved 438 MUSCLE PHENOMENA. for the purpose of study. Fig. 254 represents the method of recording muscular contraction. Other forms of the myograph are the spring myograph (Fig. 255) and the pendulum myograph (Fig. 256). Time-markers or Chronographs. — In order to know and record the length of time consumed by various phenomena which are the subject of investigation, various forms of time-markers are used which make a record on the drum at the same time that the myo- gram is being made. Such an one is the electric signal of Deprez (Fig. 258), which is an electromagnet whose circuit is closed and opened by the second pendulum of a clock or a metronome. Or for this purpose a tuning-fork may be used which vibrates Fig. 255. — Spring myograph : A, B, iron uprights, between which are stretched the guide-wires on which the travelling plate a runs ; k, pieces of cork on the guides to check gradually the plate at the end of its excursion and prevent jarring; b, spring, the release of which shoots the plate along ; h, trigger-key, which is opened by the pin d on the frame of the plate (Stewart). one hundred times in a second, the writing-point being attached to one of its prongs. Moist Chamber. — In order to preserve the preparation in as normal condition as possible during an experiment, it is enclosed in a chamber the air of which is kept moist. Sim^ple Musciilar Contraction. — When the muscle-nerve prep- aration is stimulated by a single induction shock, a single con- traction of the muscle results ; this is a twitch or a simple muscular contraction, and its myogram is shown in Fig. 259. This is a simple muscle-curve. Latent Period. — The moment that the stimulus reaches the muscle is represented by a in the illustration, but the upward IRRITABILITY. 439 curve begins at h. So that between these events there is an interval of 0.00(5 second, as sliown by the lowest line, in which the curves are tnade by a tinie-niarkcr. This interval is the latent period. At b the curve begins rapidly to rise, then more slowly, Fig. 256.— Pendulum myograph ; at the left, as seen from the front : A, bearings on which the pendulum swings; P, pendulum; G, G', glass plates carried in the frames T, T; a, pin which opens the trigger-key. The key, when closed, is in con- tact with c, and so completes the circuit of the primary coil (Stewart). when it reaches its highest point, e. Then, as the muscle begins to relax, there is a downward curve until the line is reached from which the curve started, this line being the abscissa ; the descend- ing curve shows that the relaxation is at first rapid, then becomes 440 MUSCLE PHENOMENA. slower, and occupies a longer time than the contraction. From a to 6 occupies about 0,006 second ; from 6 to c, about 0.05 second ; from c to d, about 0.07 second. Helmholtz, in his experiments upon the frog's gastrocnemius, found that the latent period occupied j^-^ second ; the rise of the curve, or the star/e of contraction proper, j^-^ second ; and the fall or stage of elongation, ywo • ^^ Fig. 257. — Time-marker; arrangement for marking two intervals: D, seconds pendulum, with platinum point, E. soldered on ; A, mercury trough, into which E dips at the end of its swing ; B, Daniell cell : C, electromagnets, which draw down writing-lever F when the current is closed by E dipping into A ; G, spring (or piece of India rubber), which raises i^'as soon as current is broken (Stewart). Fig. 2,58. — Electromagnetic time-marker connected with metronome. The pen- dulum of the metronome carries a wire which closes the circuit when it dips into leither of the mercury cups, Hg (Stewart). ]-j^ second in all. A close inspection of the myogram will show ja slight rise after d ; this is due to the elasticity of the muscle, and .constitutes the fitage of clastic after-vibration or contraction-remain- der. Sometimes more than one of these curves are produced. Since the time of Helmholtz's experiments other observers have found that the true latent period is much shorter, certainly not more than 4^Vo second, and probably even shorter than this, for IRRITABILITY. 441 it is highly probable that changes begin immediately in the muscle upon the receipt of the stimulus, although these changes are not at once apparent. The muscle-curve differs in the muscles of different animals and also in those of the same animal. iSummatio)i of Stimuli. — If a muscle which has been stimulated Fig. '259.— Myogram from gastrocnemius muscle of frog ; beneath, the time is re- corded in 0.005 second : a, moment of excitation ; 6, beginning of contraction ; c, height of contraction ; d, end of contraction (Lombard). is again stimulated before the effect of the first stimulation has passed, a second curve will be produced, which will be higher than the first (Fig. 260), due to the addition of the second stimu- lation to the first. This is the summation of stimulation, summa- tion of effects, or superposition of contraction. Tetanus. — When a series of stimuli are added one to another Fig. 260.— SupeiTOsition of contractions: 1 is the curve when only one stimulus is thrown in ; 2, when a second stimulus acts at the time when curve 1 has nearly reached its maximum height (Stewart). before the effects of the preceding ones have passed, so tliat the muscle at no time becomes completely relaxed, the condition of tetanus is produced : incomplete tetanus, if the effect of each stimu- lation can be seen in the separate curves (Fig. 261), and complete tetanus, where these have disappeared and their place is taken by a 442 MUSCLE PHENOMENA. continuous line (Fig. 262). Voluntary tetanus is the term applied to the normal voluntary contraction of a muscle. The impulses sent out by the nerve-cells are generated and emitted with such frequency as to produce tetanus, and not a simple contraction. The character of the simple muscle-curve is modified hy : Fig. 261. — Development of incomplete tetanus and contracture, by indirect stimulation. A gastrocnemius muscle of a frog was indirectly stimulated by breaking induction-shocks, of medium strength, applied to the sciatic nerve. The rate was about 8 per second, as shown by comparison of the seconds traced at the bottom of the tigure with the oscillations caused by the separate contractions. 1. The load ; 2. The temperature ; 3. Previous stimulation ; 4. The character of the muscle itself; and 5. Drugs. 1. Effect of the Load. — The extent to which a muscle contracts is increased up to a certain point with the increase of the load ; but when this point is reached it diminishes, and if the load is sufficiently increased, its power to lift it at all ceases. 2. Effect of Temperature. — Up to a certain point cold increases Fig. 262. — Effect of rapid excitations to produce tetanus. Experiment with a gastrocnemius muscle of a frog, excited directly with breaking induction-shocks of medium strength, at the rate of 33 per second. The weight was about 15 grains. The time record gives fiftieths of a second (Lombard). the contraction ; beyond this point it dimini.shes it ; moderate warmth also increases the lieight of the contraction, but excessive heat (exceeding 40° C.) coagulates the proteids of the muscle, producing heat-rigor. 3. Efect of Previous StimuIatio7i. — "SVlien a muscle is stimu- lated, each curve is a little higher than the preceding one for a IRRITABILITY. 443 time, the curve beint^ called a staircciHe ; then, as the stimulation is t'DUtiuuod, the curve i'alls, aud finally there is no response to the stinudation — the nuiscle is Jutif/iud. Caui^c of luitk/Hc of Mnsclcs. — This is explained in the case of the muscle-nerve preparation by the fact that the destruction or katabolism of the muscular tissue predominates over its anabolism or building up, and after a time its contractile power is lost. Fig. 263.— EflTect of fatigue on the height of muscular contractions. The figure is a reproductiou of parts of a record of over 1700 contractions made by an isolated gastrocnemius muscle of a frog. The contractions were isotonic, the weight being about 20 grams. The stimuli were maximal breaking induction-shocks, and were applied directly to the muscle at the rate of 25 per minute. Between the first grt»up of 6G contractions and the fcjllowing groups a rest of five minutes was given ; after this rest the work was continued without interruption for about one and a half hours. The second group of contractions, that immediately following the period of rest, contains the first 20 contractions of the new series ; the next group the 100th to the 110th ; the next the 200th to the 210th, and so on (Lombard). Fatigue also occurs as a result of the accumulation of the prod- ucts of contraction, sarcolactic acid and acid potassium phosphate, which to a certain extent act to prevent contraction, and when these are removed by the circulating blood during a period of rest following muscular activity, the contractile power is restored. In tlie fatigue of muscles which follows their use as the result of volition, the cause is chiefly in the nerve-cells in which the voluntary impulses are generated. 444 MUSCLE PHENOMENA. 4. Effect due to the Character of the Muscle. — Some muscles contract more slowly than others, even in the same individual ; as, for instance, those of the leg than those of the arm. The same difference is seen in the corresponding muscles of different animals. 5. Effect of Drugs. — The efiect of drugs upon muscular contrac- tion is well illustrated by injecting veratrin under the skin of a frog : the principal characteristic of the muscle-curve produced being the extreme prolongation of the period of relaxation (Fig. 264). Rigor Mortis. — It has already been stated (p. 62) that the coagulation of the muscle-plasma is the cause of rigor mortis or cadaveric rigidity, in which the muscle becomes opaque and stiff, and loses its elasticity and extensibility ; at the same time it becomes warmer and acid in reaction. Rigor usually appears in from one hour to five hours after death, although this is subject Fig. 2<)4. — ]SIyogram of muscle poisoned with veratrin and that of a normal muscle: a, myogram from a normal gastrocnemius muscle of a frog — the waves at the close are due to the recoil of the recording lever: 6. myogram from a gastroc- nemius muscle poisoned with veratrin. recorded at the same part of the drum (Lombard). to great variation, coming on more rapidly in muscles that are feeble than in those that are strong and vigorous. Thus in per- sons who have been in good health, dying suddenly, it comes on slowly ; while when deatli occurs after protracted illness it comes on quickly, and remains but a short time. Animals which have been hunted, and whose muscles are consequently exhausted by fatigue, are the subjects of early rigor mortis. There are, how- ever, instances in which rigor has come on very early in those who were presumably in health at the time, although it is pos- sible that these were not exceptions, and that the cause of the early appearance was due to muscular exhaustion ; as, for instance, soldiers killed in battle being found with one eye closed and the other open in the act of taking aim. It has been said that after death from lightning or in the heat of passion, rigor mortis is entireh' absent ; but it is more than probable that in such cases IRRITABILITY. 445 it comes on early and disappears without liaving been ob- served, Rioor mortis, as a rule, is first observed in the neck and lower jaw, tlion in the upper, and later in the lower extremities, passing off in the same order. There are, however, exceptions to this. It may remain for from one to six days. Little is known about rigor mortis of involuntary muscle, although this condition has been seen in the heart, stomach, and uterus. Mnscular Tone. — If a relaxed muscle is divided, the two ends separate — /. c, each portion of the divided muscle contracts, so that even in a so-called relaxed muscle this is in a state of tonic con- traction, and this condition is muscular tone or muscular tonus. The advantage which accrues from this is that when the muscles are called upon to perform any work they are already in a posi- tion to effect results quickly, which would not be the case if it were necessary to bring them from a state of complete relaxa- tion to one of effective contraction. It is as if one desired to move a boat by a rope, and before exerting any influence on the boat was compelled to take up a considerable amount of slack. Muscular tone is a reflex action depending upon the reception by the cord of afferent impulses, under which stimulation motor impulses are sent out to the muscles; and if the afferent nerves are cut, the. tone disappears. Peristalsis. — The difference in the manner of contraction of voluntary muscle, as the skeletal muscles, as compared with that of involuntary muscle, as that of the intestines, is very marked, for while the action of the former takes place rapidly and throughout the entire muscle, the action of the latter is slow, and moves from point to point as a wave, at a rate of about 30 mm. per second, the contraction occurring at one part of the intestines while it has disappeared at another, the circular coat being especially active in the movement. It is called also vermicular contraction. When the movement is in the direction opposite to the normal, as in the intestine from below upward, or in the stomach from the pylorus toward the cardia, it is reversed ponsfalsis. Rhj/fhriiicaliti/. — Involuntary muscular tissue exhibits the prop- erty of contracting and relaxing with a certain degree of regu- larity or rhythm, as in the spleen, where there are a true systole and a diastole, recurring about once each minute, as demonstrated by the oncometer (p. 327\ Electric Phenomena (Fig. 265). — A normal muscle in a condi- tion of rest is iso-electric — /. e., it is " equally electric throughout, and hence has no electric current " ; the same is true of dead muscle. If, however, the muscle is cut, the electrical condition is changed, and if the part that is cut and the normal part are connected to a galvanometer, the movement of the magnet at once 446 MUSCLE PHEyOMEXA. demonstrates the existence of an electric current flowing from the normal to the cut portion. If the muscle is caused to contract, the needle of the galvanometer will return to the position of rest. The first current was formerly called the current of rest, Init is now known as the current of injury or demarcation current ; while the second is the current of action, or n^f/ative variation current. Fig. 265. — Schema to .show the direction of currente to be obtained from mu~A:\t. The .schema reijresents a cylindric piece of muscle with normal longitudinal .surface 'a r and b d), and two artificial crfjs.s section.s (a h and c d). The j>osition of the equator is .shown by line e. The unbroken lines connect points of different potenrial, and the arrows show the direction which the currents would take were these y>oints connectefl with a galvanometer. The broken lines connect points of equal potential from which no current would be obtained fLombardj^ Du Bois Reyraond explained the current of rest by supposing that in the normal muscle at re.-t there were electric currents due to the fact that muscle was made up of electromotive molecules, and that each of these molecules is positive at the center and negative at the ends, and this difference of electric tension be- comes manifest when the muscle is cut and the negative ends are exposed. Hermann, however, denies the existence of currents in Fig. 266. — Secondary tetanus (Lombard). normal muscle, and attributes their generation to the injury to the muscle cau.sed by its action, chemic changes being thus brought about. Other injur}' than cutting will produce the .same result, and as these changes take place at the point between the normal and injured tissue the term " demarcation" has h)een applied to the current thus produced. IRRITABILITY. 447 It should be said, however, that there are authorities who hold witii Du Jiois Rcyniond that uornial muscle in a condition of rest is the seat of cloctroniotivc forces, which require changed condi- tions in muscle to bring them forth. It has been already stated that dead muscle is iso-electric ; dead muscular tissue is, however, electrically negative to normal living muscle. Sccondari/ Contraction (Fig. 2G6). — To demonstrate secondary contraction two nerve-muscle preparations are made, and the nerve of one is placed upon the nniscle of the other. Such an arrangement constitutes a pJiysiologic rheoscope or rheoscojyic frog. When the nerve of the first preparation is stimulated, not only its muscle, but also that of the second preparation, contracts. If the stimulation is single, a secondary contraction or twitch results ; while if the stimuli cause tetanus of the first muscle, there will be secondani tetanus of the second muscle. The explanation of these secondary contractions would seem to be that the current passes through the first preparation into the second ; but if the nerve of the second is tied, the secondary con- traction does not take place, so that this explanation is not a true one. Du Bois Reymond's explanation is that each stimulus applied to the first nerve causes a contraction of its muscle and a current of action, which stimulates the nerve of the second preparation, and a contraction of its muscle follows. IV. NERVOUS FUNCTIONS. GENERAL CONSIDERATIONS. There is a most intimate relationship existing between the different organs of the body — so intimate, indeed, tliat not one of the whole number can be said to be entirely independent of the others. Many illustrations of this dependency might be given, but one will suffice. The respirations of an individual at rest are not far from 16 per minute, and the pulsations of the radial artery are, under the same condition, about 70. If, now, he exercises violently, the respirations will l^e found to have greatly increased, amounting perhaps to 30 per minute, while at the same time the pulsations of the artery will have reached 120 per minute. Is this change from the quiescent condition a mere coincidence, or is there a reason for it? If the latter, how has the change been brought about ? During a resting condition the muscles of the body do not make great demand upon the blood, and with the heart beating 70 times per minute the muscles, as well as the other tissues, are receiving all the material they need for the performance of their functions. The 16 respirations a minute are also sufficient to supply the blood with all the oxygen required and to remove from it the necessary amount of carbon dioxid. When, however, the muscles are called upon for the increased exertion above referred to, they must have a greater supply of the necessary materials, to furnish which a larger amount of blood must be sent to them. Then, too, as a result of the extra work, more muscular tissue is wasted, and the waste must be taken away rapidly to tlie organs whose duty it is to eliminate it. To send the larger supply of blood the heart must loeat faster, and to provide the increased oxygen and to remove the additional carbon dioxid the respiratory movements must be more rapid. The muscles of the body have not the power within themselves to increase their activity, but when acted upon properly from without thev have. Neither has the heart-muscle the ])Ower to beat more quickly imtil influenced thereto by some influence outside itself. Equally powerless are the agencies which produce the respiratory movements. These outside influences, by which the muscles contract and by which the heart and the respiratory apparatus act in harmony, are 448 NKR VES. 449 (U'rived from the nervous system, a collection of organs one of whose functions is to cause the ditferent organs to act harmo- niously. The effect of a want of harmony under the circumstances just supposed would be most disastrous. If the nervous force was not at command to make the muscles respond when their increased action was desired, there would be a condition of paral- ysis, or if, when the muscles attempted to perform this added task, the heart should fail to respond, the effort would be fruitless ; and e(iuallv unavailing would be the attempt if at the crucial moment the lungs and other respiratory organs should be unresponsive. Manv other illustrations of the interdependence of the organs might be given, but a little reflection will suggest them almost ad infinitain. The simplest movements that are made require for their per- formance the conjoint action of several, often many muscles, and were it not for the exciting and controlling power of the nervous system, instead of the harmony which is everywhere and at all times apparent, there would result the utmost confusion. In what has been said thus far reference has been had only to the individual, as if he M'as alone on the face of the earth and interested only in himself; but there are other human beings with whom he is constantly brought into relation, and a world of other animate objects as well as an infinite amount of inanimate matter. This relationship is also accomplished through the nervous system, principally by means of the special senses. It will, therefore, be seen that the nervous functions are those wdiich bring the different organs of the body into harmonious relations with one another, and, in addition, bring the individual, through the special senses — sight, hearing, etc. — into relation with the w^orld outside him. The nervous system is made up of collections of nerv'ous tissue, which is composed of two kinds of matter — nerve-fibers and nerve-cells, Avith neuroglia ; tliese have been already de- scribed (p. 63). NERVES. Nerve-fibers associated together form nerves, and these con- duct impulses from within outward, from without inward or from one nerve-center to another. Whether it is the function of a given nerve to do the one or the other does not depend upon any- thing in the nerve itself, l)ut upon its relations ; and there is every reason to believe that were it ])0ssible to separate a nerve from its anatomic connections and attach it to different structures, it would be just as capable of acting in its new relations as it did in the old ; just as a copper wire will carry equally well a current of electricity to ring a bell or to supply a motor or to turn a hand on a dial : The result depends not upon the wire, but upon the mechanism with which it is in connection. 29 450 • NERVES. Classification of Nerves. — There are three kinds of nerves, classified according to the direction in which they carry impulses : 1. Efferent; 2. Afferent; and 3. Intercentral. Efferent Nerves. — Inasmuch as nerves of this kind carry im- pulses away from nerve-centers, they are also called centrifugal nerves. They were formerly spoken of as motor nerves. All motor nerves are efferent, for they carry impulses outward, but all efferent nerves are not motor. A nerve which carries an impulse to a muscle, and thus brings about motion, is properly called a " motor nerve " ; but one that conducts an impulse to a gland, the results of which are the activity of its cells and the production of a secretion, is improperly named a motor nerve, although it is un- questionably an efferent nerve, ^eeretory is a much more appro- priate name. Efferent nerves may be divided as follows : (1) motor ; (2) vasomotor ; (3) accelerator ; (4) secretory ; (5) trophic ; and (6) inhibitory. Motor nerves terminate in muscles, and convey to them im- pulses which cause and regulate their contraction. Vasomotor nerves, although distributed to the muscular tissue of blood-vessels, and thus act as motor nerves, regulate the amount of blood supplied to a part, and it seems wise to separate them from the purely motor nerves and put them in a class by themselves. Accelerator nerves are nerves Avhich carry impulses that increase the rhytlimic action of an organ, as the sympathetic nerves to the heart. Secretory Nerves. — The impulses which these nerves carry to glands bring about their secretion. The chorda tympani is a striking example. Trophic nerves are supposed by some to govern the nutrition of the structures to which they are distributed, entirely independently of the regulation of the blood-supply. It is still a mooted ques- tion whether such nerves exist. Efferent inhibitory nerves carry impulses which restrain or inhibit the action of the organs to which they are distributed. The pneumogastric, so far as the heart is concerned, is such a nerve. Without its restraining influence the heart would beat much faster. Afferent Nerves. — The fact that these nerves carry impulses to the nerve-centers has led to their being called also centripetal nerves. They were formerly called sensory nerves, but there is the same impropriety in using these terms synonymously as in the case of efferent and motor nerves. All sensory nerves are afferent, but all afferent nerves are not sensory. Afferent nerves may be divided as follows, although the distinction is by no means so well marked as in the efferent nerves : (1) Sensory ; (2) nerves of special sense ; (3) thermic nerves ; (4) excitoreflex ; and (5) inhibitory. DETERMINATION OF THE FUNCTION OF A NERVE. 451 Semory Nerves. — When these nerves are stimulated an impulse is carried to a nerve-eenter ; if this center is the brain, the sen- sation may be a conscious one, and may or may not be painful. Nerves of Special Sense. — The impulses carried by these nerves do not give rise to pain, but with each nerve is connected a special sensation : With the olfactory, the sense of smell ; with the optic, the sense of light ; and with the auditory, the sense of hearing. Thennic Nerves. — It is believed by some writers that there are special nerves which convey the sense of temperature only ; but this is still an unsettled question. Excitoreflex Nerves. — In these nerves there is an impulse car- ried to a nerve-center without producing a conscious sensation : this center is excited, and from it or from another center with which it is in communication there goes out an impulse that, if it is a gland to which it is distributed, produces secretion : such a nerve would be an excitosecretory nerve. Or if it is distributed to a muscle, it produces motion, and would in that case be considered an excitomotor nerve. Afferent Inhibitory Nerves. — The afferent inhibitory nerves are also called centro-inhibitory, to distinguish them from the efferent inhibitory nerves. The centro-inhibitory nerves carry impulses to nerve-centers, which are so affected as to prevent them from send- ing out impulses. A familiar instance is that of pinching the lip to prevent sneezing. It is, however, doubtful whether there exists a separate class of nerves performing this function, rather than ordinary sensory fibers which act in this peculiar manner for the moment. Intercentral Nerves. — The nerve-centers are intimately con- nected with one another by nerves which are neither afferent nor efferent, and which are called intercentral. As has been said, even the simplest movements of the body bring into action several, and sometimes many muscles ; of course, this action is more obvious in complex •movements. To accomplish this, various nerve-centers must be at work ; and that they may act harmoniously and pro- duce coordinated movements it is essential that they should be in intimate relationship. Study for a moment the intricate mechanism brought into play in the ordinary act of picking up a pin from the floor, and it will be readily understood how essential it is that the nerve-centers responsible for these movements should act in the most perfect harmony, sending to each muscle just the right aniount of nerve-force and at exactly the right moment ; other- wise the act could not be accomplished in the perfect manner that it is. Determination of the Function of a Nerve. — The func- tion of a nerve may be determined by (1) dividing it, and observ- ing what function has l)een lost ; or (2) stimulating it, and observing the effect of the stimulation. Thus when a motor nerve is divided, 452 NERVES. there is a loss of power, or para/3/s/.s of motion, in the muscle sup- plied by the nerve. If, on the other hand, a galvanic current is passed through the nerve, there will follow contraction of the muscle. Similarly a paralysis of sensation will follow division of a sensory nerve ; and when such a nerve is stimulated, sensation will result. When a nerve is thus divided, one portion will remain in communication with the nerve-center, and is called the central or proximal end ; while the other, which remains in communica- tion with the periphery, is the distal or perijjheral end. Stimu- lation of the central end of a motor nerve produces no effect; while the motion referred to above results from stimulation of its peripheral end. In the case of a sensory nerve, it is the reverse. Wallerian Degeneration. — When a nerve is divided the first result is a loss of its function. Afterward the nerve under- goes Wallerian degeneration, which results in changes in its structure that can readily be seen. Inasmuch as each nerve-fiber develops from a cell which later nourishes it, if the connection between the two is severed, the nerve-fiber undergoes Wallerian degeneration, and in the case of a nerve which is made up of nerve-fibers the whole nerve undergoes this change. This degener- ation consists, in the case of medullated nerves, in the death of the axis-cylinder, the breaking up of the medullary sheath iuto drops of myelin, which are later absorl)ed, and the multiplication of the nuclei of the primitive sheath. In non-medullated nerves the only result is the death of the axis-cylinder. Degeneration begins very soon after the section — within a day or two — and throughout the entire severed portion of the nerve at the same time. Thus the course of a nerve, or a collection of nerves, may be traced throughout its entire extent. These changes are believed to be due to the severance of the nerve from its trophic center. If an anterior root of a spinal nerve is divided, the distal end, being separated from the gray matter of the cord which is its center of nutrition, undergoes degeneration, while the end which remains connected with the cord retains its integrity. If a posterior root is divided between the cord and the ganglion, the degeneration takes place between the cord and the ganglion ; while if divided l^elow the ganglion, the degeneration takes place in that portion separated from the ganglion, showing that the ganglion is the uTitritive center for the posterior root. Regfeneration of Nerves. — If the two ends of a divided nerve are brouglit together and retained there, a regeneration may take place, and the new structure has all the properties of the original nerve. It will be remembered that in the degeneration w^hich follows division of a nerve there is an increase in the nuclei of the sheath. These form a continuous thread of pro- toplasm within the old sheath, and around this protoplasm a new sheath develops, the whole forming an embryonic nerve-fiber, ELECTROTONUS. 453 whicli unites with the proximal jxjrtiuii of the okl fiber still in connection with its nntritive center, and hence has undergone no degenerative change. Such a regenerated fiber has both conduc- tivity and irritability, the former appearing as early as the third week, but the latter not manifesting itself until afterward. At this period of the regeneration there is neither myelin nor axis- cylinder, and the fiber is responsive to mechanical stimuli, l)ut not to induction shocks, which latter property returns only after the axis-cylinder is developed. The medullary substance later appears and forms a tube ; and still later the axis-cylinder is formed, having its origin in the central end of the nerve — /. c, the portion which is still in communication with the cell from which the original axis-cylinder was developed. The complete regeneration of a nerve may take months. So far as known, regeneration does not occur in the central nervous system. NERVE-IMPULSES, The function of nerve-fibers is to conduct impulses, and this from centers to the periphery, from the periphery to centers, or from one center to another. Although much study has been given to the subject, exactly what a nerve-impulse is has never been determined. Except an electrical change in the nerve itself, and the results of the reception of the impulses at the termination of the nerve, as motion in a motor nerve, secretion in a secretory nerve, etc., there is no evidence of the fact that impulses have travelled over the nerve. Chemical, mechanical, or thermic changes, if they occur, have never been demonstrated. The stimuli which excite muscle will also stimulate nerves ; these are electrical, mechanical, chemical, and thermic ; and what has been said of these applies in general to nerves. It should be called to mind, however, that induction-shocks stimulate nerves more powerfully than a voltaic current ; while in the case of muscle it is the voltaic current which is the more powerful stimulus. Velocity of Nerve-impulses (Fig. 267). — In the motor nerves of human beings nervous impulses travel at the rate of 33 meters a second, and in sensory nerves, from 30 to 33 meters in the same length of time. Blectrotonus. — Although contraction of a muscle takes place at the make and break of a constant current which is passed through the nerve distributed to it, and although no apparent change takes place in the nerve at either of these moments, or indeed while the current is passing, still during the latter period important changes are actually taking place, though they are not visible ; these are changes in the electrical condition of the nerve, in its excitability and also in its conductivity, and are collectively 454 NEB VE-IMP ULSES. called eledrotonus. This has been concisely defined as "a change of condition in nerves traversed by an electric current." It also occurs in muscles. B',. Fig. 267. — Arrangement for measuring the velocity of the nerve-impulse: A, travelling plate of spring myograph ; M, muscle lying on a myograph plate ; iV^, nerve lying on two pairs of electrodes, E and E' : C. Pohl's commutator without cross- wires; K, knock-over key of spring myograph (only the binding screws shown); A", simple key in primary circuit; B, battery; P, primary coil; 8, secondary coil (Stewart). That an electrical change is produced in a nerve by passing a constant current through it, the polarizing current, may be demon- strated by connecting the nerve with a galvanometer. The Fig. 268. — Electrotonic alterations of irritability caused by weak, medium, and strong battery currents : A and B indicate the points of application of the elec- trodes to the nerve, A being the anode, B the kathode. The horizontal line repre- sents the nerve at normal irritability ; the curved lines illustrate how the irrita- bility is altered at different parts of the nerve with currents of different strengths. Curve y^ shows the effect of a weak current, the part below the line indicating de- creased, and that above the line increased irritability ; at .r' the curve crosses the line, this being the indifferent point at which the katelectrotonic effects are com- pensated for by anelectrotonic effects; v^ gives the effect of a stronger current, and 2/', of a still stronger current. As the strength of the current is increased the effect becomes greater and extends farther into the extrapolar regions. In the intrapolar region the indifferent point is seen to advance with increasing strengths of current from the anode toward the kathode. current near the kathode is the hatelectrotonic current, while that near the anode is the anelectrotonic current. These currents occur only as the result of passing a constant current through a nerve, ELEGTROTONUS. 455 and cease when the current ceases. They exist in living medul- lated nerves only, or it' at all in degenerated nerves but to a slight degree. At the time of the passage of the current there is an increase in the excitability or irritability of the nerve in the kathodic region, and a decrease in the anodic region ; the increase is katelec- f)'oto)ias, and the decrease, anelectrotonus. After the opening of the current the conditions are reversed, the excitability being temporarily increased in the anodic, and decreased in the kathodic Fig. 269. — Diagram of changes of excitability and conductivity produced in a nerve by a voltaic current: E, changes of excitability during the flow of the current, according to Pfliiger. The ordinates drawn from the abscissa axis to cut the curve represent the amount of the change. C (1), changes of conductivity during the flow of a moderately strong current; conductivity greatly reduced around kathode; little afl'ected at anode. C (2), changes of conductivity during flow of a very strong current ; conductivity reduced both in anodic and kathodic regions, but less in the former. C', changes of conductivity just after opening a moderately strong current; conductivity greatly reduced in region which was formerly anodic; little afl'ected in region formerly kathodic (Stewart). area. The indiffercni point is the point at wliich there is no change in the excitability of the nerve, where the katelectro- tonic and anelectrotonic effects counteract each other ; this will change its position according to the intensity of the current, approaching the katliode as the intensity increases. Fig. 268 shows the changes which take place according as the intensity of the current is increased. The condndivity of a nerve is also affected by the constant current, the changes being shown in Fig. 269. 456 THE NERVOUS SYSTEM. THE NERVOUS SYSTEM. The nervous system is divided into two subdivisions : the cerebrospinal system and the sympathetic system. The cerebrospinal system includes the brain and spinal cord, which together form the cerebrospinal axis, and the nerves which come from them, namely, the cranial and spinal nerves. SPINAL CORD. The spinal cord is situated in the vertebral canal, and is covered by three membranes — the dura mater, arachnoid, and pia mater. It is about 0.43 meter in length, and, in general, is of a cylindrical shape ; it weighs 42.5 grams. It extends from the medulla oblongata above to the first lumbar vertebra below, where it ends in the jilum terminale, although in fetal life it extends to the bottom of the sacral canal. Enlargements of the Spinal Cord. — Two enlargements along the course of the spinal cord are noteworthy. The cervical Fig. 270. — Different views of a portion of the spinal cord from the cervical region, with the roots of the nerves. In A the anterior surface of the specimen is shown, the anterior nerve-root of its right side being divided : in £ a view of the right side is given ; in C the upper surface is shown ; in D the nerve-roots and gang- lion are shown from below : 1. the anterior median fissure ; 2, posterior median fi.s.sure; 3, anterior lateral depression, over which the anterior nerve-roots are seen to spread ; 4, posterior lateral groove, into which the po.sterior roots are .seen to sink ; 5, anterior roots pas-sing the ganglion ; 5', in A, the anterior root divided ; 6, the po.sterior roots, the fibers of which pass into the ganglion, 6 ; 7, the united or compound nerve; 7', the posterior primary branch, seen in A and D to be derived in part from the anterior and in part from the posterior root (Allen Thomson). enlargement extends from the third cervical to the first or the second dorsal vertebra, and tne lumbar enlargement is at the eleventh and twelfth dorsal vertebra. From the cervical en- largement go off the nerves which supj^ly the upper, and from the lumbar those which supply the lower, extremities. SPINAL CORD. 457 458 THE NERVOUS SYSTEM. Fig. 272. — Four cross-sections of the human spinal cord: A, cervical region; in the plane of the sixth spinal nerve-root ; B, lumbar region ; C, thoracic region ; D, sacral region ; X 7 (from preparations of H. Schmaus) (Bohm and DavidoflF). SPINAL CORD. -159 Fissures (Fig. 270).— On the anterior surface of the spinal cord is a groove, the anterior median fissure, which extends to the anterior white commissure. On the posterior surface is also a so- called fissure, the posterior median fissure, which is filled with connective tissue and blood-vessels, and extends to the posterior qraif commissure. It will thus be seen that the anterior and posterior fissures nearly divide the cord into two symmetrical halves, which are connected by the commissures. At a little distance from the anterior median fissure on each sidJ is the anterolateral fissure. Strictly speaking, this is not a fissure being rather a line of small openings at which emerge the anterior roots of the spinal nerves. In front of the posterior median fissure and on either side is the posterolateral fissure. Here emerge the posterior roots of the nerves. The posterior intermedin ate furrow is between the posterior median and posterolateral fissures. Columns. — The anterior and posterior median fissures divide the cord into two svmmetrical halves, and the anterolateral and posterolateral fissures subdivide each half into three columns called main columns: anterolateral, posterolateral, and posterior median. , Anterolateral Column.— This includes that portion ot the cord between the anterior median and the posterolateral fissure. It is divided by some anatomists into an anterior, situated between the anterior median fissure and the anterior nerve-roots, and a lateral, the portion between these roots and the posterolateral fissure (Fig. 271). Posterolateral Column. — This is the portion between the postero- lateral fissure and the posterior intermediate furrow. Posterior Median Column. — This is also called posteromedial column. It is situated between the intermediate furrow and the posterior median fissure. The posterolateral and posterior median are sometimes described together as the posterior column. Section of the Spinal Cord (Fig. 273).— A cross-section of the spinal cord shows a central gray substance and an external white substance. The gray matter presents the appearance of two crescents, with the concavities outward, joined together by a band of grav matter, the gray commissure. The points of the crescents are the horns or cornua, two anterior and two posterior. The posterior cornua come nearly to the surface of the cord at the posterolateral fissure, while between the surface and the extremi- ties of the anterior cornua there is considerable white matter. The arrangement of the white matter into columns is readily discerned ?n this section. In the gray commissure is a small canal — the central canal — which communicates with the fourth ventricle of the brain, and contains cerebrospinal fluid. This is a colorless alkaline fluid containing sodium chlorid and other 460 THE NERVOUS SYSTE3I. inorganic salts, and about 0.1 per cent, of proteids, ])rincipally proto-albumose, with some serum-globuJin, and rarely peptone. kSerum-albumin, fibrinogen, and nucleoproteid are absent. It also contains a non-nitrogenous reducing substance considered by Claude Bernard to be sugar, but by Halliburton to be pyrocatechin derived from the proteids. The central canal is lined with columnar epithelium, which in fetal life is ciliated, but the cilia are often absent in the adult. The canal is of special interest in connection with the develop- ment of the cord. Sections of the cord at different levels show that the white substance is most abundant in the upper part, and Fig. 273. — Transverse section of half the spinal cord, in the lumbar enlargement (semi-diagrammatic) : 1, anterior median fissure ; 2, posterior median fissure; 3, cen- tol canal lined with epithelium ; 4, posterior commissure ; 5, anterior commissure; 6, posterior column ; 7, lateral column ; 8. anterior column (the white substance is traversed by radiating trabeculse of pia mater): 9. fasciculus of posterior nerve-root, entering in one bundle ; 10, fasciculi of anterior roots, entering in four spreading bundles of fibers ; b, in the cervix cornu, decussating fibers from the nerve-roots and posterior commissure ; c, posterior vesicular columns. About half-way between the central canal and 7 is seen the group of nerve-cells forming the tractus inter- mediolatenilis ; e. e. fibers of anterior roots: e' , fibers of anterior roots which decussate in anterior commissure (Allen Thomson). gradually becomes less abundant as the examination is made down itlie cord. The cervical and lumbar enlargements are due to the increased amount of gray matter at these points. Minute Structure of the Cord. — Neuroglia supports both the white and the gray matter of the spinal cord, and occurs also under the pia mater, around tlie central canal, forming the sub- stmifia gelathiosa centralis, and at the apex of the posterior horn, forming the svhsfnntia cinerea gelatinosa of Rolando or substantia gelatinosa lateralis. The white substance is made up of medullated nerve-fibers and blood-vessels, in addition to neuroglia. The medullated nerve- SPINAL CORD. 461 fibers in sections stained with carmin or anilin blue-black appear as clear areas with the stained axis-cylinder in the center, the clear space being the me(hillary substance. The gray matter consists of nerve-fibers, of nerve-cells and their processes, together with neuroglia and blood-vessels. Tracts of the Cord. — The course which the nerve-fibers take in tlic cohimns of the cord has been determined by two methods : the eml)ryoIogic and the degenerative. The eiiihri/olof/ic method, or method of Flechsig, consists in studying the cord at different stages of its develoj^ment ; and as in some tracts the medullary substance forms at an earlier period than in others, these can be thus differentiated or distinguished from one anotlier. The degenerative, or Wallerian, method consists in studying the degeneration which occurs in nerve-fibers when separated from their nutritive or trophic centers (p. 452). Sections of the cord in which the degeneration has taken place are stained with Marchi's solution, consisting of JNIiiller's fluid 2 parts, and 1 per cent, osmic acid 1 part : the degenerated fibers stain black, while the other portion remains practically unstained. A tract in which this degeneration takes place below the injury or point of section is a descending tract, and the degeneration is a descending degenera- tion ; while a tract in which the process occurs above the lesion is an ascending tract, and the change, an ascending degeneration. These methods have demonstrated the following tracts in the cord (Fig. 271), into which the main columns may be considered as divided. Each tract or fasciculus may be considered. Gray says, as a distinct anatomic system and endowed with special functions : 1. Direct Pyramidal Tract. — This is also called fasciculus of Tiirck, and is situated in the anterolateral column next to the anterior median fissure. It is continuous with the non-decussating fibers of the pyramid of the medulla. Besides this tract, the anterolateral column contains : 2. Crossed Pyramidal Tract. — The fibers of this tract are con- tinuous with those forming the decussation of the pyramid of the medulla. 3. Direct Cerebellar Tract. — Continuous with the restiform body. 4. Anterolateral Ground-bundle. — Continuous with the forma- tio reticularis of the medulla. 5. Anterolateral Descending Cerebellar Tract (Lowenthal). 6. Anterolateral Ascending Cerebellar Tract (Growers). 7. Tract of Lissauer. The posterior column contains : 8. Posteromedian, also called posteromesial and column of Goll, which is continuous with the funiculus gracilis of the medulla. 462 THE NERVOUS SYSTEM. 9. Posterolateral, also called column of Burdach, which is con- tinuous with the funiculus cuueatus. 10. Comma trad. The position and relation of these tracts can be better under- stood by reference to the illustrations than by any verbal descrip- tion. Grouping of the Nerve-cells (Fig. 274).— Some of the nerve-cells of the cord are distributed through the gray matter, while others are arranged in groups, the latter being larger, and characterized by their branching; they are multipolar verve-cells. Cells of the Anterior Horn. — In the anterior cornu are three of these groups: 1. Near the tip on the inner side; 2. At the base on the inner side ; and 8. On the outer side of the grav matter. Posterior horn cell. Crossed pyram _ ,_, idal column. /I " / \ Gol^ cell of ■ posterior horn. Direct cerebel- lar column. Column cells.-- 7- i -i^r^- Gol^'s commis-.J-T-^'X — C~ — sural cells. \ ' I V^^v Gowers' col^-^ — uinn. ^■. Motor cells. 2n_ Direct pyramidal column. Fig. 274. — Schematic diagram of the spinal cord in cross-section, Lenhossek, showing in the left half the cells of the gray matter, iu the the collateral branches ending in the gray matter (Bohm and Davidoff ). Collaterals ending in the gray matter. after von right half Each cell of the anterior cornu gives off an axis-cylinder process which passes out into the anterior nerve-roots. Cells of the Posterior Horn. — These are smaller than those of the anterior cornu, but their axis-cylinder processes do not pass into the posterior nerve-roots. Clarke's Column. — This group of cells is most marked in the thoracic region, and is situated at the l)ase of the posterior cornu. Their axis-cylinder processes pass into the direct cerebellar tract. Intermediolateral Tract. — This group is situated on the outer side of the grav matter in what is called the lateral horn between the anterior and posterior cornua. Middle Cell-group. — These lie in the middle of the crescent. Nerve-fibers of the Gray Matter. — These are, as a rule, smaller than those in the white substance. In the posterior cornu SPINAL CORD. 463 they form Gerlach's net-oe-network, in which small and larger nervo-fibcrs exist together. Tliesc fibers can be traced to tiie meduUated fibers of the posterior nerve-roots, and also to the processes of the ganglion-cells, thus bringing these cells into con- nection with the posterior nerve-roots through the network. The fibers of the anterior horn are directly continuous with the axis-cylinder processes of the ganglion-cells. The following illustration (Fig. 275) represents the relations between the nerve-cells the skin, and a muscle. Spinal Nerves. — There are thirty-one pairs of spinal nerves, which are distributed to the neck, trunk, and extremities. Each mJV Fig. 275.— Schematic diagram of a sensorimotor reflex arc according to the modern neuron theory ; transverse section of spinal cord ; miV, motor neuron ; sN, sensory neuron; C^, nerve-cell of the motor neuron; C^, nerve-cell of the sensory neuron ; d, dendrite; n, neuraxis of both neurons ; t, telodendrons ; M, muscle-fiber; h, skin with peripheral telodendron of sensory neuron (Bohm and Davidoff ). of these arises by two roots ; an anterior or motor, and a posterior or sensory root. Anterior Roots. — These are traced through the anterolateral column to the cells of the gray matter of the anterior cornu. Around the cells is an interlacement of ramified nerve-endings, which come especially from the collaterals of the posterior root- fibers and from those of the fibers of the white substance of the cord. Posterior Roots. — These are characterized by the presence upon each of a ganglion, except the posterior root of the first cervical nerve, which frequently possesses no ganglion. These roots have their origin in the cells of the ganglion, and pass into the postero- lateral column, some entering the marginal bundle of Lissauer, 464 THE XERVOUS SYSTEM. and some passing into the posterior cornii. "When the fibers of the posterior root enter the cord they bifurcate, one branch passing upward, the other downward. From the main fiber, and also from the branches, pass collaterals, which end in the gray matter in arborization, and in the nerve-cells of the anterior and posterior cornua. In the same manner end the main fiber and its branches ; some, how^ever, pass upward in the posterolateral and posteromesial Fig. 276.— Transverse section through half the spinal cord, showing the ganglia: A, anterior cornual cells ; B. axis-cylinder process of one of these going to posterior root: e. anterior (motor) root : D. posterior (sensory) root; E. .spinal ganglion on posterior root : F, sympathetic ganglion ; G, ramus communicans ; H, posterior hranch of spinal nerve : I. anterior branch of spinal nerve ; a. long collaterals from posterior root-fibers reaching to anterior horn ; b. short collaterals passing to Clarke's column : c. cell in Clarke's column sending an axis-cylinder (d) process to the direct cerebellar tract : e. fiber of the anterior root : /, axis-cylinder from sympathetic ganglion cell, dividing into two branches, one to the periphery, the other toward the cord : a. fiber of the anterior root terminating by an arborization in the sympa- thetic ganglion : /;, sympathetic fiber passing to periphery > Eamon y Cajal). columns, and end in the medulla by arborizing around the cells of the nucleus gracilis and cuneatus. Spinal Ganglia. — The structure of these ganglia has been already described. Beyond the ganglion the two roots unite to form the trunk of the spinal nerve, which passes out through the intervertebral foramen, and gives oif a recurrent branch to the dura mater of the cord. It then divides into a posterior division, which is distributed to the posterior part of the body^ and an ante- SPINAL CORD. 465 rior division which goes to the anterior part ; botii divisions contain libers from both roots. Functions of the Spinal Cord.— Ihe li Mictions of the spinal cord arc of two kinds: 1. A eon(hictor of iinj)nlses, by virtue of the fibrous nervous matter which it contains ; and 2. A nerve-center, by virtue of its nerve-cells. As a Conductor of Impulses. — The spinal cord is the principal channel tlirouo^h which all impulses from the trunk and the extremities pass to the brain, and all im- pulses to the trunk and extremities pass from the brain. If through disease or injury the cord is disor- ganized at any point, all power to produce volun- tary motion in the parts below the injury is lost, and conscious sensation in these parts is from that moment abolished. The cord therefore acts as a conductor of impulses, both motor and sensory, between the brain and the trunk and extremities ; the different kinds of impulse follow different paths in the cord. Condnding-paths in the Cord. — The paths by which voluntary motor impulses traverse the cord are fairly well ascertained. These im- pulses originate in the pyr- amidal cells of the cerebral cortex, and pass through the pyramids in the medulla, crossing principally at the decussation of the pvra- mids, and to a less degree in the upper part of the cord, to the opposite side, whence they follow the course of the pyramidal tracts, direct and crossed, arbo- rizing around the cells of the anterior cornu ; from which the anterior roots arise to be distributed to the muscles. The course pursued by the sensory imjjulses (Fig. 277) is not 30 Fig. 277.— Schema showing pathway of the sensory impulses. On the left side, .S", S', repre- sent afferent spinal nerve-fibers ; C, an afferent cranial nerve-fiber. This fiber in each case ter- minates near a central cell, the neuron of which crosses the middle line and ends in the opposite hemisphere (van Gehuchten). 466 THE NERVOUS SYSTEM. SO well uuderstood as is that of the motor. But the best opinions may be summarized as follows : Tactile and niusciUar sense-imjjressions pass up the posterior columns to the nucleus gracilis and nucleus euneatus, by the internal arcuate tibers and fillet to the optic thalamus, by the posterior part of the internal capsule to the llolandic area of the opposite side. Painful, impressions, and those of heat and cold, pass up the grav matter of the cord from cell to cell to the optic thalamus, and bv the fibers of the corona radiata to the cortex. Afferent impulses reach the cerebellum by Clarke's column, direct cerebellar tract, restiform body, and inferior peduncles. The fibers composing the tract of Gowers have their origin in cells at the base of the anterior cornu, on the opposite side, and its cerebellar fibers pass to the middle lobe by the superior peduncles. There are other fibers in the cord, which have their origin in the cerebellum ; but although their existence has been ascertained their destination is not certainly determined, though it is thought by some that they arborize around cells in the anterior cornu. As a Nerve-center. — Besides the function \vhieh the cord per- forms as a conductor of motor and sensory impulses, it also acts as a nerve-center in which, by virtue of its nerve-cells, afferent impulses are received and motor impulses are generated. Voluntary motion in the extremities, which motion originates in the brain, is abolished when the cord is divided and its ana- tomic connection with the brain cutoff; but there still remains the power of exciting muscular contractions in these muscles, due to the cells of the cord itself. Reflex Actio7i. — If a frog is deca])itated, it has no longer the power of producing voluntary movements ; but if the skin of a foot is irritated by pinching, the foot is pulled away from the source of irritation. This is an instance of reflex action. A slight pinch will cause only the one foot to be withdrawn ; but if it is stronger, the other foot may also be withdrawn. This is known as a spreading of reflexes. Such movements are not spontaneous, but thev require the application of a stimulus for their production. The irritation docs not act upon the muscles directly, but through the medium of nerves, an afferent nerve carrying the sensory impulse inward to the cord, and an efferent nerve conducting a motor impulse outward to the muscles. If either of these nerves is divided, the action does not take place ; nor does it if the gray matter is broken up. For the performance of a reflex act, there- fore, three things are necessary — an afferent nerve, a nerve-center, and an efferent nerve, all in a physiologic condition. This can be readily underst(wd by reference to Fig. 275, where h represents the skin, from which passes an afferent nerve to the SPINAL CORD. 467 center, and C represents a cell in the anterior eornii of the cord, from which passes a motor impulse to the muscle m. In the human subject, when the cord is injured or diseased at any point, so as to cut off comnuuiieation between the brain and extremities, but is still intact l)el()w this point, tickling of the soles of the feet will be followed by their withdrawal, although the individual will be entirely unconscious of anv sensation. This is also an instance of reflex action. As in the frog, so in man, the three structures mentioned must exist in a state of integrity for the performance of this act. It is not essential, however, that the cord be diseased in order to have it manifest reflex action : this property is one which normally resides in the cord. Thus if the hand comes in contact with a flame, it is immediately withdrawn. This is not a voluntary act, for the act of withdrawal takes place before the sensation of pain is felt in the brain. It is a purely reflex act, in which the gray matter of the cord, after being stimulated by an impulse carried to it by an afferent nerve, generates an impulse which is conveyed by an efferent nerve to the muscles concerned in with- drawing the arm. The afferent nerve, nerve-center, and efferent nevxe form a reflex arc. If the attention was fixed upon the subject at the time the burn was received, it might be possible to prevent the withdrawal. This would be an instance of inhibi- tion of reflex action. Reflex Time. — From the moment when the stimulus is applied to the moment when the reflex action takes place is an appreciable interval of time, part of which is occupied bv the passage of the afferent impulse to the center, jiart by the passage of the efferent ner^'e to the muscle, part by the latent period of the muscular contraction, and part by the reception of the afferent impulse and the generation of the efferent impulse in the center itself; this latter is the reflex time. In the frog it varies from O.OOS to 0.015 second. Heat and an increase in the strength of the stimulation lessen it. Reflexes in Man. — The presence or absence of certain reflexes is made use of to determine the presence or absence of certain diseases in the human subject. They are included in two grou])S, supei-ficial and dee]i. Superficial Reflexes. — Of these, there are many, but the princi- pal ones are : 1. Plantar. — Tickling the sole of the foot causes its with- drawal, 2. GJnteal. — Pricking of the skin over the gluteus causes a contraction of that muscle. 3. Cremai^teric. — Stimulating the skin on the inner side of the thigh causes a retraction of the testicle. 468 THE NERVOUS SYSTEM. 4. Abdominal. — Stimulating the skin of the abdomen causes a contraction of muscles in this region : when this occurs in the epigastric region it constitutes the epigastric rejiex. 5. Xasal. — Stimulation of the nasal mucous raeml)rane causes sneezing. 6. Conjunctival. — Touching the eyeball causes closure of the eyelids. Deep Reflexes. — These are called also tendon rejlexes, but are not true reflexes as are the superficial ones, being caused by direct stimulation of the muscles or their tendons. 1. Tendo Achillis Reflex. — If while the extended leg is sup- ported at the knee a hand is firmly pressed against the ball of the foot, a tap on the tendo Achillis causes the gastrocnemius and soleus to contract and draw the heel up quickly. This may exist or not during health. 2. Ankle-clonus. — The leg being supported, the ball of the foot is suddenly pressed so as to put the muscles of the calf on the stretch, and there results a series of clonic contractions of these muscles which cease when the pressure is removed. This is absent in health. 3. Patellar Reflex or Knee-jerk. — If one thigh is crossed over the other, a tap on the tendon below the patella causes a forward movement of the leg. This is present in health, but may be in- creased or abolished in disease. Other Functions of the Cord as a Nerve-center. — The power of the spinal cord to respond to afferent impulses independently of the will is of great advantage in preserving the body from injury. The closing of the eye when moving oVjjects are liable to injure it, the attempt to retain one's equilibrium after slipping on a side- walk, the raising of the arms in front of the face to ward off an unexpected blow, are all instances of this action. Walking, playing on musical instruments, and similar acts are all performed under the influence of the gray matter of the cord. To start them requires the action of the l)rain, but when once they are begun their continuance is accomplished by the cord, and the brain can be busy about other things without interfering in the slightest degree with the perfection of their performance. Indeed, any attempt to control them is more apt to hinder than to help them. Thus in coming rapidly down a flight of steps, if the spinal cord is permitted to take charge of the act the descent will be made with ease and safety, but if each step is made as the result of volition, the chances of stumbling or of tripping are very much increased. The reflex action of the cord may be diminished by shock to the nervous svstem ; thus in the frog immediately after decapita- tion the reflex power cannot be excited, but after a short time it manifests itself under the influence of a stimulus. A similar SPINAL CORD. 469 diminution of the reflex power of the cord may be caused by opium, bv chloroform, and by some other substances, \yhile the reflex action is iitcrcuscd by strychnin. If under the skin of the decapitated frog a solution of strychnin is injected, the cord in a short time becomes so irritable that a stimulus which before would have had no effect will now produce the most marked results, a sli^dit blow upon the skin sutticing to throw the animal into a con- vulsive state. In tetanus the same irritable ccmdition of the cord exists, and in this state the patient may be thrown into convulsions bv the simple opening and closing of a door. Special Centers in the Cord. — It is the practice to speak of certain centers as existing in the spinal cord--that is, of detinite collections of cells wliich preside over definite functions. Among these centers the following have been described : Musculo- tonic, 'respiratory, cardio-accelerator, vasomotor, sudorific, cilio- spinal, genitospi'nal, anospinal, vesicospinal, trophic, for erection of the penis, for parturition, and others. Musculotonic Center. — This center is continually discharging impulses which keep the muscular system in a condition of slight contraction : this is called muscular tone. It is questionable whether this condition is to be attributed to any special center rather than to the action of all those cells whose function it is to send out motor impulses. Respiratory Center. — The respiratory center is in the medulla, but experiments in which this structure has been destroyed while some respiratory movements persisted demonstrate that to a cer- tain extent, doubtless very slight, the spinal cord controls the respiratory processes. Cardio-accelerator Center. — The s])inal cord through the cardiac nerves and plexus sends impulses to the heart, causing it to beat more rapidly — that is, they accelerate its movements. These impulses are* not constantly emitted as are the inhibitory impulses, which travel bv the pneumogastric. Vasomotor Center. — The vasomotor center in the cord is entirely subsidiary to that in the medulla. Sudorific Center. — The existence of special nerves controlling the secretion of sweat seems to be demonstrated. These nerves come from the spinal cord, being a part of the anterior roots. Ciliospinal Center.— Nerve-fibers pass from this center to the iris, and thev are concerned in the dilatation of the pupil. These fibers come out from the cord through the anterior roots of the spinal nerves, from the fifth cervical to the fifth thoracic, and join the cervical sympathetic. Genitospinal Center. — The genitospinal is the center which governs the emission of semen, and is situated in the lumbar region of the cord. Sensory impulses from the glans penis reach this center through afferent nerves and stimulate it, and from it 470 THE NERVOUS SYSTEM. go out efferent impulses which cause contraction of the muscular fibers of the vasa deferentia, seminal vesicles, and accelerator urinffi, the result of which is to produce an ejection of semen. Anospinal Center. — The act of defecation is governed by the anospinal center and has been already described (p. 258). Vesicospinal Center. — The act of micturition is under the in- fluence of the vesicospinal center. This act has been already described (p. 41 9 j. Trophic Centers. — It has already been seen that when nerve- fibers are divided they undergo degeneration, and that this is ex- plained by the fact that under these circumstances their connection with certain nerve-cells is severed, and that they are thus deprived of the nutritive influenct; which such centers exert. Such centers are called tropJiic ccnto-st, and the cells of the anterior cornua of the cord and the ganglia on the posterior roots of the spinal nerves are familiar illustrations. That these are true trophic centers for nerves seems to be beyond dispute, but this is an entirely different question from that which deals with trophic nerves as regulating the nutrition of tissues other than nerves. About the existence of such nerves there is considerable doubt. Other Centers. — Some writers describe a center for erection of the penis, and locate it in the lumbar enlargement. The afferent nerves from the penis cause this center to send out efferent im- pulses by which the blood-vessels are dilated and the muscles are compressed, thus preventing the return of the venous blood from the penis and bringing about erection. A center for parturition is described as being located in the lumbar region of the cord, above the centers already mentioned ; under the influence of this the muscular tissue of the uterus contracts at the proper time and expels the fetus. Other reflex centers are described, but the tendency to extend the number of such centers seems to be beyond what the actual facts warrant. However, enough has been said to show the great importance of the spinal cord as a nervous center, independently of its function as a conductor of nervous impulses to and from the brain. Functions of Spinal Nerves. — Stimulation of an anterior root causes contraction in the muscle to which it is distributed, w'hile its division is followed by a loss of motion in the same muscle. In neither instance is sensation affected. If after the division the distal portion of the nerve is stimulated, muscular contraction will follow, while stimulation of the proximal end, that which is in connection with the cord, will produce no effect. The anterior roots are therefore efferent and motor, and are dis- tributed to muscles. Stimulation of a posterior root causes a sensation of pain in the part to which the nerve is distributed. Division of the root causes a loss of sensation in that part. If after division the THE BRAIN. 471 distill iK)rtion of tlic lUTve is stimulated, no effect is produced, while .stiimihition of the proxiinul portion produces sensiition. The posterior roots are therefore afferent iintl sensory and are dis- tributed to the skin. The two roots uniting form a mixed nerve that is, one in which there are both motor and sensory fibers. Recurrent Sensibility. — When the distal end of a divided an- terior root is stimulated, besides the muscular contraction which follows there is also some pain produced. If the trunk of the nerve beyond the ganglion is divided, and then the anterior root is stimulated, no muscular contraction results, but the pain is felt as before. If, however, the posterior root is divided, no sensation is produced. The sensation experienced when the anterior root is stimulated is accounted for by the ])resence in this root of some sensory fibers which pass up into it for a short distance and form a loop, returning to the junction of the two roots, and then pur- suing their course in the posterior root. These are called recurrent scmori/ fihf.rs. The impulse passes along these fibers to the point of junction of the two roots, and then along the posterior root to the nerve-center. Function of the Spinal Ganglia. — As has already been stated, upon each posterior root of a spinal nerve, with one exception, is a ganglion. When examined under the microscope, the root-fibers spread out, passing between groups of large cells having promi- nent nuclei and a diameter of about 100 //. With one of these ganglion-cells a root-fiber is in communication, and the function of these cells is to form the fibers and to regulate their nutrition ; they are true trophic centers. THE BRAIN. The brain, or encephalon (Figs. 278, 279), is that part of the cerebrospinal axis situated within the cranium or skull. Its divisions are sometimes described as the forebrain, including the hemispheres, with the olfactory lobe, the corpora striata, and the optic thalami ; the midbrain, licing the corpora quadrigemina and the crura cerebri ; and the liindbrain — that is, the cerebellum, the pons Varolii, and the medulla oblongata. In the adult male the brain weighs, on an average, 1415 grams avoirdupois: in the female, 1245 grams. In 278 cases of males in which the brain was weighed the maximum was 1841 grams and the minimum 968 gramk In 191 eases of females the max- imum was 1586 grams and the minimum 878 grams. The brain of Cuvier, the great naturalist, weighed 1815 grams; that of an idiot weighed 651 grams. The brain of a mulatto not remarkable for intelligence weighed 1927 grams. The forebrain weighs about 1245 grams in the adult male. The gray matter of the brain is in some parts on the surface, 472 THE NERVOUS SYSTEM. as in the convolutions of the cerebrum ; in other parts it is deeply situated, as in tlie basal ganglia — /. e., the corpora striata, optic thalami, etc. (p. 487) ; while in still other parts it is scattered about without any tixed arrangement, as in the pons Varolii. The white matter is made up of fibers which come from the spinal cord ; of fibers having their origin in the gray matter, and which, escaping from the skull, go to their points of distribution as the Fig. 278. — Base of brain : 1, 2, .3, cerebrnm ; 4 and .'i. lonsitiulinal fis.snre ; 6, fissure of Sylvius; 7, anterior perforated spaces; 8, infnndibulnm ; 9, corpora albi- cautia ; 10, posterior perforated space ; 11, crura cerebri ; 12, pons Varolii ; 13, junc- tion of spinal cord and medulla oblongata ; 14, anterior pyramid ; 14", decu,ssatiou of anterior pyramid ; 1.5, olivary body ; 16, restiform body ; 17, cerebellum ; 19, crura cerebelli ; 21, olfactory sulcus; 22, olfactory tract; 23, olfactory bulbs; 24, optic commissure ; 25, motor oculi nerve ; 26, patheticus nerve ; 27, trigeminus nerve ; 28, abducens nerve ; 29, facial nerve ; 30, auditory nerve ; 31, glossopharyn- geal nerve ; 32, pueumogastric nerve ; 33, spinal accessory nerve ; 34, hypoglossal nerve. cranial nerves ; and of still other fibers connecting the ganglia with one another, forming commissures. The Medulla Oblongata. — The medulla oblongata, or bulb, is the continuation of the spinal cord, and is about 2.5 cm. long, 2 cm. broad, and 1,2 cm. thick. It is composed of gray and white matter. The gray matter, which in the cord has the characteristic donble crescentic shape, approaches more and more the posterior surface rilK BRAIN. 473 of the cord as the region of the iiuHhilhi is reached, and the pos- terior cormia become more and more external, the whole mass of gray matter flattening out, until in the medulla it forms a layer the outer portions of Avhich represent the posterior horns and the middle ])ortions the anterior. The posterior eolumns separate in the medulla, the central canal cominir to the surface posteriorly and entl- ing in the fourth ventricle, the floor of which is the gray matter above referred to, which is, however, not limited to this site, but is pres- ent also about the aqueduct of Svlvius. From this gray matter arise all the cranial nerves except- ing the olfactory and optic. The medulla, like the cord, has an anterior and a posterior median fissure. At the lower part of the anterior fissure are fibers that cross from side to side, the decussation of the anterior pyramids. The pos- terior fissure of the cord widens out and forms the fourth ventricle. Some of the cranial nerves come out from the medulla, and serve as l)oundaries to describe the different portions of the medulla. That por- tion of white matter between the anterior median fissure and the roots of the hypoglossal ner^'e is the anterior pyramid. The lat- eral column is between the roots of the hypoglossal and those of the glossopharyngeal, the pneu- mogastric, and the spinal acces- sory. At the upper portion the olivarv body lies between the col- umn and the pyramid. The pos- terior column is between the lat- eral column or tract and the pos- terior median fissure. It is com- posed of three smaller columns separated by shallow grooves, the most external being the funiculus of Rolando, next the funiculus cuneatus, and the most internal the funiculus gracilis, the first two being joined in the upper part of the medulla to form the restiform" body. The outer portion of the pyramid is derived Fig. 276.— View, from below, of the connection of the principal nerves with the brain : I', the right olfactory tract ; II. the left optic nerve : II', the right optic tract (the left tract is seen passing back into i and e. the internal and external corpora gcniculata) ; III. the left oculomotor nerve ; IV. the trochlear : V.Y, the large roots of the trifacial nerves : -^ -f , the lesser roots (the - of the right side is placed on the Gasserian ganglion): 1. the oph- thalmic; 2. the superior maxillary ; and 3. the inferior maxillary divi- sions: VI. the left abducens nerve; VII, VIII. the facial and auditory nerves : IX-XI. the glossopharyngeal, pneumogastric. and spinal accessory nerves : XII. the right hypoglossal nerve : Ci. the left suboccipital or first cervical nerve (Xancredel. 474 THE NERVOUS SYSTEM. from the direct pyramidal tracts of the same side, while the decus- sation consists of the fibers of the crossed pyramidal tract of the lateral colunni. In the restiform bodies are to be found, besides the funiculus of Rolando and the funiculus cuneatus, fibers of the direct cere- bellar tract of the lateral column. These bodies form the inferior peduncles of the cerebellum. The funiculus of liolando is the enlarged head of the postericjr cornu of the cord, and is therefore gray matter. The funiculus cuneatus is the continuation of Burdach's column of the cord, and the funiculus gracilis is tlie continuation of GoU's column. Functions of the Medulla Oblongata. — Conduction. — All the impulses, whether afferent or efferent, passing between the brain and the cord must pass through the medulla. Nerve-centers. — Experiments have demonstrated that all the brain above the medulla and all the spinal cord may be removed and yet life be maintained, provided that the origin of the phrenic nerves is left intact ; wliile if all these structures are undisturbed and the medulla is destroyed, death will result. The centers in the medulla are both reflex and automatic. Reflex Centers. — One of the most important of these centers is that which presides over deglutition. As has been seen in dis- cussing this process, the first stage of the act is voluntary ; but as soon as the food has passed into the pharynx, the act becomes involuntarv. The mucous membrane of the pharynx is stimu- lated by the food, and the afferent fibers of the glossopharyngeal transmit the impulse to the medulla, in which a motor impulse is generated, and out along the efferent fibers comes the impulse to the constrictors of the pharynx. Centers for vomiting, coughing, sucking, and for other movements are described. The act of vomiting is a reflex one, in which the fibers of the pneumogastric serve as afferent fibers, the impulses stimulating the center in the medulla, from which emanate motor impulses to the respiratory and other muscles concerned in the act. If the act of vomiting is brought on by stimulating the pharynx with a feather or with a finger, the glossopharyngeal is the carrier of the afferent impulses. Afferent impulses producing vomiting may also come from other organs, such as the kidneys, or the testicles when injured. Central Vomiting. — In central vomiting tiie center is stimu- lated by impulses which come from the brain. Rumination. — The power to ruminate, by virtue of which ani- mals chew the cud, is possessed In' some human individuals, M'ho can regurgitate the food whenever they feel so disposed, and chew it again. Automatic Centers. — Besides reflex centers, which require a stimulus from without to bring them into action, the medulla THE BRAIN. 475 possesses automatic centers which generate and emit impulses independently of stimuli iVom without. licspiratori/ Center. — This center is situated in the floor of the fourth ventricle, and when injured, respiration ceases immediately. Some authorities place it among the reflex centers. It may, in- deed, be excited reflexly, but there are reasons for believing it to possess automatic powers as well. If tiie s])inal cord is divided below the medulla, although the respiratory movements of the thorax cease, those of the nose and larynx continue. Under these circumstances no afi'erent impulses can be transmitted through the spinal nerves, and the only channel is the cranial nerves ; but if, while the medulla and cord are left undisturbed, the cranial nerves are cut, respiration continues. These two series of experiments show that respiration will continue independently of stimuli from without — that is, automatically. The principal nerves that transmit the impulses producing the respiratory movements are the intercostals and the phrenics to the diaphragm. The respiratory center is double, so that one side may act after the other is injured. Division of one phrenic para- lyzes only the side of the diaphragm to which it is distributed. The respiratory center may also be excited reflexly. The afi'erent fibers under these circumstances are those of the pneumogastric. Cardio-inhibitory Centei'. — In the cardio-inhibitory center are generated those impulses which, travelling to the heart by the pneumogastric nerve, inhibit or restrain the action of that organ. This subject will be more fully discussed in connection with the functions of the pneumogastric nerve. The accelerator nerves of the heart have their origin in the spinal cord, and are distributed to that organ through the sympathetic ganglia. Whether they have any origin in the medulla is doubtful. They are antagonistic to the pneumogastric, and carry impulses to the heart which hasten its action. Vasomotor Center. — The principal vasomotor center is situated in the medulla, in the floor of the fourth ventricle, extending from its upper part to a point about 4 mm. from the calamus scriptorius. When the center is destroyed there is a marked fall in arterial blood-pressure, due to the loss of tone in the small blood-vessels. After a while the pressure is increased under the influence of stimuli sent out from the subsidiary vasomotor centers in the cord. When the center is stimulated, arterial pressure is increased on account of the constriction of the vessels. Vasomotor Nerves. — The vasomotor nerves, which originate in the cells of the vasomotor center in the bulb, pass down the lateral column of the spinal cord, and it is believed that they arborize around the cells of the subsidiary centers in the spinal cord, although the precise location of these centers has not been deter- mined. The cells in these subsidiary centers give rise to axis- 476 THE NERVOUS SYSTEM. cylinders which form a part of modullated nerve-fibers that enter as component parts of the anterior roots of the spinal nerves. Vasocondridor Nerves. — These nerves cany impulses which cause constriction of the arterioles. They pass out from the cord in the anterior roots of the spinal nerves from the second thoracic to the second lumbar, which they leave by the white rami com- municantes, passing into the sympathetic ganglia situated along the vertebral column. These ganglia contain cells around which the nerve-fibers arborize, and they are spoken of as eel/ dcdions. From these cells axis-cylinder processes are given off which are continued as non-medullated fibers and which carry the impulses that orig- inate in the vasomotor centers. Vasodilator Nerves. — The description of the vasoconstrictor fibers just given applies in general to the vasodilator, though there are some marked exceptions, for while, as a rule, they pass out together, still some do not. A striking example of this is the chorda tympani, which is given off from the facial. Nor do the dilator nerves arborize around the cells of the ganglia of the sympathetic chain, but pass through these and lose their medullary sheaths in the collateral ganglia, such as the semilunar, around whose cells they arborize. Depressor Nerve-fibers. — Between the heart and the medulla are nerve-fibers which carry impulses from the heart to the vaso- motor nerve-center, which impulses inhibit the center, and thus diminish the impulses to the muscular coat of the arteries, thereby causing the arteries to dilate and reducing arterial pressure. In the rabbit these fibers are together and form the depressor nerve, but in most animals they are joined with the fibers of the pneumo- gastric. By means of these fibers the nerve-center can be inhibited and arterial pressure lessened, thus reducing the work of the heart. Pons Varolii. — The pons Varolii (tuber annulare or meso- cephalon) is situated just above the medulla, and is composed of three sets of fibers and of some gray matter. The first set consists of superficial transverse fibers which cross the upper part of the medulla and connect the two hemispheres of the cere- bellum, forming at the sides the crura cerebelli or middle peduncles. The second is made u]) of longitudinal fibers which come from the pyramids of the medulla and pass on to help form the crura cerebri^ The third set is also transverse and is deeply situated, connecting the middle peduncles of the cerebellum. Among its fibers are collections of gray matter. Functions of the Pons Varolii. — The anatomic relations of the pons show that it must serve as a conductor of impulses both to and from the centers above. As to the function of its gray matter, comparatively little is known, save that from a portion of it some of the cranial nerves arise. If it is stimulated or divided, pain THE BRAIN. 477 and s|):isms are prodiiecd. Wlieii a lesion is sitnated in tlie lower half ot" the pons, there resnlt taeial paralysis on the same side as the lesion, and motor and sensory paralysis on the opposite side of the body. This is called alternate paralysis. If the lesion is in the npper half of the pons, the facial paralysis and that of the body are on the same side. When the pons is suddenly and ex- tensively injured, a condition of liy|)erpyr(>xia is often produced, the temperature rising rapidly within an hour. This is probably Blood-vessel. Y- Nerve-fiber layer. Fig. 280.— Section through the human cerebellar cortex vertical to the surface of the convolution ; treatment with Miiller's fluid ; x 115 (Bohm and Davidoff ). due to the influence of the gray matter in the floor of the fourth ventricle, or possibly to the involvement of some special heat- regulating center. The Cerebellum.— The cerebellum (Figs. 280, 281) is com- posed externally of gray matter, which also penetrates into the substance of the organ, forming with the white matter the lamince. In the central part of the cerebellum is white matter, in which is imbedded a collection of gray matter, the corpus dentatum. The cerebellum is connected with the rest of the encephalon by the THE BRAIN. 479 superior, the middle, and tiie inferior ])eduncles. Tlie superior pcduueles (y>/vxv',s.swi( e ccrchello ad /r,s/(\s) connect the cerehclhini with the cerebrum; the middle })eduncles {crura cerebc/li) con- nect the two eerebellar heniisi)h('res ; the inihrior {proce,H8us ad medullain) connect the eerebellum and medulla oblongata. The gray matter consists of two layers, an inner or granular layer, composed of nerve-cells, princij)ally small in size, and neuroglia ; and an outer or molecular lai/er, composed offline nerve- libers and nerve-cells. Between these two layers are the cells oj Purkiuje, which nve flask-shaped, and from the base of each of which is given oli'a neuron, which is continued as an axis-cylinder — Dendrite. Cell-bodv. Neuraxi> Fig. 282.— Cell of Purkinje from the human cerebellar cortex ; chrome-silver method ; x 120 (Bohm aud Davidoft'). ~ Neuraxis. — Claw-like telo- dendron of dendrite. Fig. 28.3.— Granular cell from the granular layer of the human cerebellar cortex ; chrome-silver method ; x 100 (Bohm and Davidofi"). of a medullated nerve-fiber of the white center. From the opposite side are given off dendrons which pass into the gray matter. In discussing the structure of the cerebellum, Schiifer says : " The dendrons of the cells of Purkinje spread out in planes trans- verse to the lamellae of the organ, so that they present a different appearance according to whether the section is taken across the lamellae or along them. These dendrons are invested at their attachment to the cell, and to some extent along their branchings, by basketworks formed by the terminal arborizations of certain fibers of the medullary center. The body of the cell of Purkinje is further invested by a feltw ork of fibrils formed by the arboriza- 480 THE NERVOUS SYSTEM. tion of axis-cylinder processes of the same nerve-cells in the outer layer of the gray matter. Each cell has therefore a double invest- ment of this nature, one covering the dendrons, the other the body of the cell. Ramifying among the granule-layer are peculiar fibers derived from the white center, and characterized by having pencils of fine short branches at intervals like tufts of moss. These are termed by Cajal the moss-fibers ; they end partly in the granule-layer, partly in the molecular layer." Functions of the Cerebellum. — If the surface of the cerebellum is irritated, no muscidar movements are produced, nor is there any evidence of sensation ; if, however, the irritation is applied near the medulla or inferior peduncles, both pain and muscular contrac- tion result. If the cerebellum is removed wholly or partially, sensation is not diminished in the part of the body below, nor is there any impairment of the power of producing muscular move- ments, nor of the special senses, nor of the intelligence ; but there is a marked want of harmony in the muscular movements — a lack of co-ordination. Attention has already been called to the fact that even the simplest movements that are made require the harmonious action of different muscles, and when these move- ments are more complex, they require different sets of muscles. If these movements do not occur at just the right time and are not produced in the right manner, the result is disorder instead of harmony ; or, as it is expressed, there is a want of co-ordina- tion, or a condition of inco-ordination or cerebellar ataxy. This is the effect of removing the cerebellum. Thus, if the cerebellum of a pigeon is removed, and an attempt is then made by it to fly, it is unsuccessful, for this act requires the consentaneous action of both wings, which action is absent. In walking the bird reels like a person intoxicated, and cannot go to the spot for which it apparently set out. It should be borne in mind that there is no paralysis either of motion or of sensation in this condition, but the voluntary movements which originate in the cerebrum, and which are in the normal condition co-ordinated by the cerebellum, pass to the muscles without this regulating influence, and the result is a series of disordered movements. Especially marked is this inco-ordination in connection with the maintenance of the equilibrium of the body and locomotion. Indeed, some authorities are inclined to limit the functions of the cerebellum to this, and to regard it as not being the con- trolling organ of co-ordination in general, (pioting experiments upon animals in which, after the first effects of its removal had passed away, there was a return of the co-ordinating power, and also instances in the human subject in which during life the movements had been co-ordinated, yet after death the cere- bellum had been found com])Ietely disorganized. It is interesting to know that in animals that produce complex THE BRAIN, 481 movements the cerebellum is considerably developed, while in those whose movements are simple, such as the frog, this organ is exceedingly small. Sources of Impressions that reach the Cerebellum. — The ana- tomic relations of the cerebellum are so intimate that impressions of many kinds can reach it and thus enal)le it to preside over this most important function of co-ordination, especially as regards equililjration and locomotion. E, lower parietal lobule, constituted b5' Pi, gyrus supramarginalis ; P>', gyrus angularis; Si, end of the horizontal branch of the fissura Sylvii ; ti, upper temporal fissure. lymph upon the otoliths, and these in turn upon the hair-cells of the maculae acusticse. Dynamic Equilibrium. — This is the equilibrium of motion, and, as already stated, is presided over by the semicircular canals, from which impressions pass to the cerebellum. The Cerebrum. — The cerebrum, which in man makes up about four-fifths of the encephalon, is divided into two hemi- spheres which are separated by the great longitudinal fissure (Figs. 286-289), but are connected by a Avhite commissure, the corpus callosum. The surface presents depressions, fissures and sulci, 484 THE NERVOUS SYSTEM. and prominences, convolutions or gi/ri. The external portion of the hemispheres is gray nervous matter about 3 mm. in thickness, beneath wliich is white matter. The fissures are not numerous, but are quite constant ; they are folds of the brain-matter both gray and white. The sulci are depressions of the gray matter alone ; they are very numerous and inconstant. As gray matter is present on both sides of the fissures and sulci, this arrangement permits of a larger amount of gray matter than could exist were it only upon the surface of the convolutions. In a brain, therefore, where the sulci are deep and numerous the amount of gray matter Fig. 287. — Outer surface of the left hemisiihere : A. anterior central or ascending frontal convolution ; B, posterior central or ascending parietal convolution ; c, sulcus centralis or fissure of Rolando ; cm, termination of the callosomarginal fissure ; F, frontal lobe; Fi, superior, F2, middle, and F^, inferior frontal convolution ; /i, supe- rior, and /2, inferior frontal sulcus ; /;, sulcuj prsecentralis ; ip, sulcus intraparietalis ; 0, occipital lobe; Oi, first, O2, second, O3, third occipital convolutions; 01. sulcus occipitalis transversus ; 02, sulcus occijiitalis longitudinalis inferior ; /', i)arietal lobe ; po, parieto-occipital fissure ; Pi, superior parietal or posteroparietal lobule ; A, infe- rior parietal lobule, viz., Pi, gyrus supramarginalis ; P2', gyrus angularis ; .^ fissure of Sylvius; S', horizontal, ^", ascending ramus of the same; T, temporosphenoidal lobe; Ti, first, T-i, second, T-^, third temporosphenoidal convolutions; h, first, t2, second temporosphenoidal fissures. exceeds that in a brain where they are more shallow and less abundant. This gray matter is the cortical substance. Fissures of the Cerebrum. — The fissures serve as landmarks in the description of the different parts of the hemispheres. Besides the great longitudinal fissure, there are (1) the fissure of Sylvius ; (2) that of Rolando ; and (3) the parieto-occipital fissure. These fissures divide each hemisphere into 5 lobes. (1) The fissure of Sj/lvius is, next to the great longitudinal fissure, the most important. It is found in all animals whose brains have any fissures. It exists in the human brain in the THE BRAIN. 485 thinl month of intra-uterinc! liil'. It coininciiccs at the base of the brain, and rnns outward, baekward, and upward, t^iving off a short anterior braneh or limb. The continuati(ni of the fissure backward from where this branch is given off is the posterior branch or horizontal limb, which ends in the parietal lobe. The fissure of kSylvius is the boundary between tlie frontal and parietal lobes on the one hand and tiie temporosjihenoidal on the other. At the middle and anterior j)art of this fissure, deeply situated, is the island of Reil, or insula, or central lobe. (2) T\\c fissure of Rolando starts near the median line, and runs downward and forward nearly to the fissure of Sylvius. It is the boundary between the frontal and parietal lobes. Fig. 288.— Inner surface of right hemisphere : A, ascending frontal ; B. ascend- ing parietal convolution; c, terminal portion of the sulcus centralis, or fissure of Eolaudo; CC. corpus callosum, longitudinally divided; Cf, collateral or occipito- temporal fissure (Ecker); cm, .sulcus callosomarginalis ; D. gyrus desceudens ; F\, median aspect of the first frontal convolution ; Gf, gyrus fornicatus; H, gyrus hip- pocampi ; A, sulcus hippocampi, or dentate fissure; 0. sulcus occipitalis transversus; oc, calcarine fissure ; oc' , superior, oc", inferior ramus of the same; Oz, cuneus ; po, parieto-occipital fissure; Pi", precuneus; T^, gyrus occipitotemporalis lateralis (lobulus fusiformis) ; Ts, gyrus occipitotemporalis medialis (lobulus lingualis) ; U, uncinate gyrus. (3) The parieto-occipital fismre is about half-way between the fissure of Rolando and the posterior extremity of the brain, and is the boundary betw'een the parietal and occipital lobes. Lobes of the Cerebrum. — The lobes of the cerebrum are (1) the frontal, (2) the parietal, (3) the occipital, (4) the temporosphen- oidal, and (5) the central, or island of Reil. (1) T\\e frontal lobe is above the fissure of Sylvius and in front of the fissure of Rolando. It is divided into 4 convolutions by 3 sulci, or fissures as they are sometimes called. The precentral fissure or sulcus is in front of the fissure of Rolando, and the convolution between the two is the ascending frontal. From the upper extremity of this sulcus the superior frontal sulcus runs downward and forward between the superior and middle frontal 486 THE XERVOUS SYSTEM. convolutions, while from the lower extremity extends the inferior frontal sulcus, separating tlie middle and inferior frontal convolu- tions. Thus the frontal lobe is divided into the ascending, superior, middle, and inferior frontal convolutions. (2) The parietal lobe is behind the frontal and in front of the occipital lobe, the fissure of Rolando being its anterior, and the parieto-occipital fissure its posterior boundary. Its inferior boundarv is the fissure of Sylvius and the imaginary continuation of it to the superior occipital sulcus. It has 2 sulci, the intra- parietal and the post-central, and 3 convolutions, the ascending, superior, and inferior parietal. (3) The occipital lobe is posterior to the parietal, and has 2 Lobulus paracentralis, Fig. 289. — Lateral view of the brain : gyri and lobuli marked with antique type, the sulci and fissures with italic ty])e (combined from Ecker). sulci, the superior and middle, and 3 convolutions, the superior, middle, and inferior occipital, the latter being subdivided into the supramarginal and the angular. (4) The Temporosphenoidal Lobe. — The fissure of Sylvius forms the anterior and superior boundaries of this lobe, while its posterior boundary is the imaginary continuation of the occipitoparietal fissure. It presents 2 sulci, the superior temporosphenoidal or parallel, and the middle temporosphenoidal. Its convolutions are 3, the superior, middle, and inferior temporosphenoidal. (5) The central lobe, or island of Reil, is situated at the base of the brain, in the fissure of Sylvius. It consists of 6 convolutions, the gyri operti. TlIK BLATX. 487 Crura cerebri, also called the peduncles of the cerebrum, are nrule up of white matter, nerves wiiieh are continuous with those ■ilreadv studied in the medulla and pons, too;ether with nerves fr..m the cerebellum, the superior pecUuieles. between the super- iicial libers of the crura, the cru.sUt, and the deeper ones, the teg- mentum, is the locus niger, a collection of gray matter. The fibers of the crura on their wav upward to the gray matter ot the hemispheres pass through the corpora striata and the optic thalami. ^ , i • i i. • Basal GangUa.— At the base of the hemisphere are certain bodies, the basal ganglia, which are the corpora striata, the optic Fig. 290.— Vertical section through the cerebrum and basal ganglia to stow the relations of the latter: co., cerebral convolutions : ex., corpus callosum ; r.(., lateral ventricle; 6., fornix: vIIL. third ventricle; n.c, caudate nucleus: tli, optic tuaia- mus; n.l, lenticular nucleus: cA.. internal capsule: cL. claustrum ; c.e.. external capsule ; m, corpus mammillare ; t.o.. optic tract : .s-.U., stria terrainalis ; n.a., nucleus amygdalae; cm, soft commissure ; co.i., island of Reil (Schwalbe). thalami, the tubercula quadrigemina or corpora quadrigemina, the corpora creniculata, and the locus niger. Corpora striata, with the optic thalami, are called the cerebra^ ganglia. The corpora striata present a striped appearance, which "is due to a mixture of grav and white matter, the latter being bundles of fibers which have come from below and within. Although at the lowest part each corpus striatum is a single body, at the dipper part it is divided into two portions, the caudate nucleus and lenticular nucleus. The lenticular nucleus, the more posterior, is separated from the optic thalamus by white matter, the internal capsule, which is the continuation of the crus cerebri. Outside the lenticular nucleus is white matter, the external cap- sule, beyond which is a layer of gray matter, the claustrum, and 488 THE NERVOUS SYSTEM. external to all these structures is the idand of Bcil. The cortical substance is at this point very near the gray matter of the basal ganglia. The fibers of the internal capsule, passing upward, radiate forward, upward, and back^\■ard, forming the corona radiata, the fibers of which pass to the cortex, each one being the continuation of the axis-cylinder process of a pyramidal cell. The fibers of the internal capsule give oif collaterals which pass to the optic thalamus, and the nucleus caudatus and nucleus lenticularis of Fig. 291. — Diagram to show the eonuection of the frontal occipital lobes with the cerebellum: ec, the dotted lines passing in the crusta (TOO, outside the motor fibers, indicate the connection between the tcmporo-occipital lobe aud the cerebel- lum ; F. C, the frontocerebellar fibers, which pass internally to the motor tract in the crusta ; I.F., fibers from the caudate nucleus to the pons ; Fr.. frontal lobe : Oc, occipital lobe ; .-IF., ascending frontal; AP.. ascending parietal convolutions ; PCF.. precenlral fissure in front of the ascending frontal convolutiou : FR.. fissure of Eolando ; IFF., interparietal fissure. A section of crus is lettered on the left side : S.IV., substantia nigra ; FY., pyramidal motor fibers, which on the right are shown as continuous lines converging to pass through the posterior limb of LC. internal capsule (the knee or elbow of which is shown thus (») ) upward into the hemisphere and downward through the pons to cross at the medulla in the pyramidal decussa- tion ; Ipt., crossed pyramidal tract; apt., direct pyramidal tract (Gowers). the corpus striatum. These ganglia give oif fibers which pass into the internal capsule and corona radiata. There are, there- fore, fibers passing into these ganglia and others passing out from them, the latter being the more numerous. The pyramidal fibers in their downward course thus give off collaterals whicli arborize around the cells of the corpus striatum and optic thala- mus, and from these ganglia axis-cylinder processes pass out to form a part of tlie pyramidal tract. So, also, the sensory fibers, particularlv tho.'^e of the fillet, arborize around the cells of the optic thalamus and the subthalamic region. THE liRAiy. 480 It is in this locality that hctiiorrhaij^e produces such serious cousc(|Ucuccs. The blooil-vci^scLs supplyiu*^ the basal ganii'lia may rupture ou account of a diseased condition, and as a result of this apoplexy or paralysis may occur, or the henujrrhage may })rove fatal. When the hemorrhage takes place into the anterior portion of the internal capside, heniip/cr/id, or paralysis of motion in the ojiposite side of the body, will result; while if it is into the })Oste- rior i)art, j^aralysis of sensation will occur on the opposite side. (jj)tic Thalanii (Fig. 290). — Each of these bodies is covered by a layer of white libers, which is especially prominent in the internal capsule. From the capsule it enters the thalamus, con- necting it with the hemisphere. The gray matter of the thalamus, of which it is principally composed, is aggregated into two masses, an ouier antl an inner nucleus, separated by a white lamina, the internal medullary lamina. In the anterior portion there is a third portion of gray matter, in which the nerve-cells are quite large. The cells of the thalamus are multipolar and fusiform. Corpora Quadrigemina. — These bodies, 4 in number, the ante- rior pair being the testes, and the posterior the ncdes, are situated behind the third ventricle and posterior commissure and under the posterior border of the corpus callosum. They consist principally of gray matter. Each gives off a bundle of white fibers to^the corpora geniculata, which joins the optic tract of the same side, and each receives fibers of the fillet which can be traced to nuclei of the opposite funiculus gracilis and cuncatus. Thus the fillet serves as a channel for afferent impulses which have traversed the fibers of the posterior roots of the spinal nerves. These nerves arborize around the cells of the nuclei, frc^m which the fibers of the fillet arise. Over the gray matter of the superior corpora cpiadrigemina is a layer of nerve-fibers which have their origin in the nerve-cells of the retina, coming by way of the optic tract, and which pass into the corpora cpiadrigemina and arborize around the cells of the gray matter. Schiifer says that these cells " are very various in form and size, and are dis- posed in several layers, which are better seen in the optic lobe of the bird (Fig. 292) than in mammals. Most of their processes pass ventralward. Their destination is not certainly known, but some appear to pass downward with the fillet, others probably turn upward and run in the tegmentum toward the higher parts of the brain ; while others, perhaps most, probably form terminal arliorizations around the motor cells of the oculomotor and other motor nuclei. All the nerve-fibers of the optic nerve and optic tract do not enter the corpora (piadrigemina. Some pass into the lateral geniculate bodies and form arborizations there. On the other hand, from the cells of these geniculate bodies the axis- cylinder processes appear to pass to the cortex of the brain (occipital region)." 490 THE NERVOUS SYSTEM. Fiiuctwns of the Cerebral Ganglia. — A marked change has taken place within comparatively recent times as to the functions and importance of the corpora striata and tlie optic tlialami. The former were for a long period of time considered important motor centers, and the latter as performing the same rdle with reference to sensation. This was doubtless largely due to the fact, to which Kirkes calls attention, that when a hemorrhage took place in the Fig. 292. — Sections of optic lobe of bird taken in planes at right angles to one another (S. Eamon y Cajal) (Golgi method). A. Anteroposterior section : a, optic fibers cnt across. The other letters indicate diflfer- ent kinds of cells, of which it will he noticed that some have their axis-cylinder processes extending ontward toward the optic fiber layer, and others have their axis-cylinder processes extending inward toward a deep layer of nerve-fibers; *', some have only short neurons ramifying in adjacent layers. B. Transverse section : a. optic fibers cnt longitudinally; h. c, d. e, their terminal ramifications in different layers of the gray matter. region of the corpora striata, motor paralysis was the result ; and that when it occurred in the region of the optic thalamus, sensory paral- ysis followed. It was, therefore, natural to attribute motion and sensation to these ganglia respectively. It is now known that when the hemorrhage is limited to these ganglia paralysis is slight, or even absent altogether, and that the effects of cerel)ral hemor- rhage ordinarily observed are due to injury of the internal capsule ; and hemorrhage into the anterior portion is followed by motor paralysis, because it is here that the fibers jiass which carry motor impulses from the cortex to the cord ; and that hemorrhage THE BRAIN. 491 into the posterior part is followed by paralysis of sensation, because in this part of the capsule are the fibers which carry the sensory impulses from the cord to the cortex. The cerebral gan«:lia are subordinate centers : the corpus striatum with regard to motion ; the optic thalamus with reg:ard to sensation, particu- larly to vision. kicroscopic Structure of the Cerebrum (Figs. 293, 294). — The Fig. 293.— The layers of the cortical gray matter of the cere- brum (Meynert). \ i f k i' i '^ i K ({ Fig. 294.— Schematic diagram of the cerebral cortex: a, molecular layer with superficial (tangential) fibers ; 6. striation of Bechtereff- Kaes ; c. laver of small pyramidal cells ; d, stripe of Baillarger; e. radial bundles of the medullary substance; /. layer of polymor- phous cells (Bohm and Davidofif). Gray Matter. — The gray matter on the external surface of the cere- brum, the co)iex, is "divisible into five layers, whose distinctness varies in different regions, being perhaps most marked in the parietal lobe ; but in the posterior portion of the occipital lobe, in the gray portion of the hippocampus major, in the wall of 492 THE SERVO US SYSTEM. the fissure of Sylvius, and in the olfactory Inilb this arrangement does not exist. These layers are : 1. Molecular Layer. — This is the most superficial, and consists of neuroglia, a few small ganglion-cells, and a network of non- meduUated and meduUated nerve-fibers, the latter forming a delicate white lamina absent in contact with the pia mater. Fig. 295. — Schematic diagram of the cerebral cortex, after Golgi and Eamon y Cajal ' Bohm and Davidoff). Fig. 296. — Large pjT^midal cell from the human cerebral cortex ; chrome-silver method ; x 150 (Bohm and Davidoffj. The non-medullated fibers have their origin principally in the small pyramidal cells of the .second layer, but also come from the dendrites and axi.--cylinder processes of the cells of the first layer. The nerve-cells of this layer have two or three axis-cylinder processes arranged horizontally, which terminate by arborization in this superficial layer. 2. Siiiall Pyramid-cell Layer. — The cells of this layer are small THE BRAIN. 493 and pvramidal, having a dianieter of" ahout 10 /i, with their lonij axos vertical to tiie surface of the convolutions. Their dendrites pass into the first layer ; their axis-cylinder processes passing olf from the base give off collaterals and form projection- fibers which go to the corpus striatum. 3. Lan/e I'ljrm aid-eel I Lai/cr. — This layer is characterized by being made up of j)yramidal cells larger than those of the second layer, and increasing in size from above downward, reach- ing a diameter of 40 /t. The breadth of this layer is shown in the illustration. The axis- cylinder processes of these cells give off collaterals and pass into the white substance of the brain, where they be- come UKKhdlated. 4. Poli/inorphous-ccll Lui/er (Fig. 295).— The cells of this layer are irregular in shape, each ffivine: off several den- drites and an axis-cylinder process. Some of these proc- esses pass into the white cen- ter, while others pass to the first layer and are contained in one of its fibers. 5. Fusiform-cell Layer. — In this layer are spindle- ^ shaped or fusiform cells. In „ „ . 1 ^. I U" +1, r Fig. 297. — Pnnciixil types of cells m the tne mner nalt they are nu- cerebral cortex: ^, medium-sized pyrami- merOUS and arranged parallel dal cell of the second layer; 7^, large pyram- — idal cell of third layer; C, polymorphous cell of fourth layer; D, cell of which the axis-cylinder process is ascending; E, neu- roglia cell ; F, cell of the first, or molecular, layer, forming an intermediate cell-station between sensory fibers and motor cells. Notice the tangential direction of the nerve- fibers ; G. sensory fibers from the white matter ; H, white matter ; 7, collateral of the white matter (Ramon y Cajal). to the surface. The claustrum is made up of this layer, sepa- rated by white substance from the other gray matter. The different varieties of cells are well shown in Fig. 297. The number of cells in the cortex has been estimated at 1,200,000,000 by Donaldson, and 9,200,000,000 by Thompson: the latter regards 1 59,960 of these as motor ; this number would therefore represent the largest pyramidal cells or " giant-cells." White Matter. — The medullated nerve-fibers of the white center are traced through the deeper layers of the gray matter. Some are continuous with the axis-cylinder processes of the pyramidal and polymorphous cells ; others arborize around the 494 THE NERVOUS SYSTEM. cells of the various layers without being anatomically in connection with thera. If the axis-cylinder processes of the pyramidal cells are traced, it will be found that they take various courses. Some, commissural fibers, pass either directly or by collaterals through the corpus callosum from one hemisphere to the other; some join association fibers, and pass into the gray matter of other parts of the same hemisphere as that in M'hich they originated ; while others, jyrojection fibers — and this is the course particularly of those having their origin in the largest pyramidal cells — pass downward through the corona radiata, internal capsule, and pyramidal tract. The number of pyramidal fibers has been estimated at 158,222 by Blocq and Ozanoff. The white matter of the cerebrum, consisting of medullated nerve-fibers, mav then be divided into three groups : 1. Those fibers that connect the cerebrum with the medulla oblongata, pons Varolii, and spinal cord. These are the crura cerebri or cerebral peduncles ; hence the group is described as peduncular or projection fibers. It will be remembered that the crura cerebri consist of the crusta and tegmentum. The fibers which come from the pyramids of the medulla and are continued through the pons aid in forming the crusta. To these fibers are added others which originate in the gray matter of the aqueduct of Sylvius and in the locus niger. After forming the crura cerebri the fibers pass upward : some of them go directly to the gray matter of the cortex : these form the corona radiata ; others go to the internal capsule, and thence to the corpora striata, where they terminate ; while some of the others continue on, receiving fibers from these bodies, and together they assist in forming the corona radiata. More fibers come from the corpora striata than end there, so that the number of those which emerge is greater than the number of those which enter. The tegmentum of the crus is made up of fibers from the anterior and lateral columns of the cord, the olivary body, funiculus cuneatus, funiculus gracilis, corpora quadrigemina, corpora genicu- lata, and the superior peduncles of the cerebellum. These fibers pass into the optic thalami, some terminating there, while others pass through. To these latter are added fibers having their origin in the optic thalami, and together they assist in forming the corona radiata, being traced to the cells in the cortical sub- stance of the temporosphenoidal and occipital lobes. 2. The second group of fibers in the cerebrum consists of those which connect the hemispheres and the basal ganglia, and are the transverse or commissural fibers. They compose the corpus callo- sum and the anterior and posterior commissures. The fibers of the corpus callosum connect the hemispheres, being traced into the convolutions and intersecting those of the corona radiata. The anterior commissure connects the corpora striata, and then passes through these bodies into the temporosphenoidal lobe. Some of THE URAIN. 495 the fibers of the jmsterior coniniissure connect the optic tliahinii, wliile some come from the tegmentum of one side, traverse tlie optic thalamus, and terminate in the white matter of the temporo- sphenoidal lobe of the other side. 3. The third ji;roup, aaHociatlon fibers, connect different struct- ures in the same hemisphere ; as the short (isaociatlon fibers, which connect adjacent convolutions, and the long association fibers, which connect more distant jnirts. Functions of the Cerebrum. — That the cerebrum is not essential to life has been demonstrated experimentally many times in birds, fishes, rats, and other animals. (Jf course, the same kind of proof is not available in man, but there are instances on record in which 9 y wmmmmm )miimmmmmmmmmik Fig. 298. — Dr. Harlow's case of recovery after the passage of an iron bar through the head. the destruction of brain-tissue has been so great as to warrant the statement that in man, as well as in lower animals, life may be maintained without the influence of the cerebrum. A remark- able instance is that of a man who was injured by a premature blast, an iron bar, one inch in diameter, being driven through the skull and brain. Although delirious and unconscious for several weeks, he finally recovered, with but the loss of one eye. He lived more than twenty years after the injury, and performed the work of a coachman and a farm-lal)orer. The cerebrum is undoubtedly the seat of the intellectual faculties. A study of the lower animals reveals the fact that according as the hemi.s])heres are developed the signs of intelli- gence are increased : when these structures are destroyed there is an absence of these manifestations. When the hemispheres are removed, spontaneous action ceases. In studving the reflex action of the spinal cord in a decapi- tated frog it was seen that the animal made no attempt to move 496 THE XERVOrS SYSTEM. or change its position unless some stimulus was applied, and that as soon as this stimulus was withdrawn it lapsetl into its original position, remaining therein until again disturbed. If the hemispheres are removed from a pigeon, it will act very much as does the iron;. If disturbed, it mav Hv for a short distance, but at once lapses into a state of apparent unconsciousness, with eyes closed. When the foot is pinched, it will be withdrawn. If a pistol is discharged, the bird will open its eyes and show unmistakably that the report was heard, but the discharge seems to produce no other effect. The fact that there is danger is not appreciated. It seems, therefore, that the faculty is absent by which the bird in health associates danger with such sounds. When the human brain is diseased or injured, something of the same kind is witnessed, and in idiots, whose brains are imperfectly developed, the intellectual faculties are very deficient. Human intelligence is manifested through memory, reason, and judgment. Memory is the basis for the action of the other two faculties ; without it there could be neither reason nor judgment. It is the facultv of the mind i)y which it retains the knowledge of previous thoughts or events, the actual and distinct retention and recogni- tion of past ideas in the mind. Afferent impulses are continually reaching the cells of the cortex of the brain, and these impulses produce impressions more or less permanent. If they were evanes- cent, passing away almost as soon as received, memory would be impossible ; but it is this retention which constitutes memory. If the ideas produced by these impulses come again into existence spontaneously and without effort, this is remembrance ; if this requires an effort, this is recoUection, a re-collecting of the im- pressions originally produced on the cells by afferent impulses. Reason is the faculty of the mind by which is appreciated the nature of nervous impulses, and by which they are referred to their external source — by which an effect is referred to its cause. This reference an idiot cannot make ; hence he is said to be " un-reasonalde." Judgment is the faculty of the mind by which a selection is made of the proper means to be used in the attainment of a par- ticular end. Thus if one selects inadequate means for the accom- plishment of a given object, it is said that one " lacks judgment." The cerebrum is the seat of conscious sensation, as opposed to sensation alone. The gray matter of the spinal cord is said to be sensitive — that is, it responds to stimuli. If the finger is burned, the afferent impulse is received by the gray matter of the cord and a motor impulse passes out to the muscles. But if the impulse travels no farther than the cord, there is no co)iiicious sensation. To excite this sensation it must proceed to the gray matter of the cerebral cortex. It is in the cells of the cortex that volitional impulses have their origin. The gray matter, then, is the seat of THE BRAIN. 497 the will as well as the conseious eenter, and when largelv diseased or destroyed, the only movements made are involuntary, depending on other nerve-eentcrs. Cerebral Localization. — Altlinim-h the study of the intellectual faoulties is Ixith ditlieiilt and abstruse, much advance has in late years been made in tiie knowledge of the physiologv of the cere- brum, so far as relates to the production of voluntary movements and the reception of sensation. Observations upon both man and the lower animals have led to the belief that the power of pro- ducing certain movements is limited to certain restricted areas of the braiu, and that other areas are connected with sensation. LoliQlas paracentTalisi Fig. 299. — Lateral view of the brain : gyri and lobuli marked with antique type, the sulci and fissures with italic type (from Ecker). These are known respectively as motor, sensorimotor, or kinesthetic or Bolandic areas, and sensory areas. The localizing of these functions is cerebral localization. These observation? had their lieginning in 1870. It was found that when galvanic currents were applied to certain parts of the cerebral convolutions movements of particular muscles followed,, and that in order to excite these muscles these parts or areas must be stimulated. Although the dog was first experimented upon^ other animals I cat, rabbit, and monkey) have furnished like results. In the application (^f these experiments the animal is put under ether, the skull is trephined, and tlie poles of a galvanic batterv are applied to the convolutions. When on such stimulation of a 32 498 THE NERVOUS SYSTEM. given spot or area contractions of certain muscles or groups of muscles follow, and when its extirpation causes paralysis of these muscles, such spot or area is said to be the motor area for these muscles. The following statement summarizes in a general M'ay what is kuown with reference to cerebral localization in the human subject : Motor Areas (Figs. 300, 301). — It has been noted that the Fig. 300. — The motor areas on the outer surface of the brain. Fig. 301. — The motor areas on the median surface of the brain. Rolandic area is also called sensorimotor and kinesthetic. This is because it has been determined that the sensory fibers from the skin and also from muscles terminate in the Rolandic area, as well as that the motor fibers have their origin here. The motor areas are grouped about the fissure of Rolando and are as follows : THE BRAIN. 499 Head, neck, and face: I^owcr two-thinls of the ascendinir frontal and the bases of the lower and niitldle transverse frontal convolntions. rpper limb: UpjK-r third of the ascending frontal, base of upper transverse frontal, ascending parietal, and part of the mar- ginal convolntions. Lower limb: Parietal lobule and posterior part of marginal. Trunk: Marginal convolution between the leg and arm. Jt is to be understooil that the action is in all eases crossed — that is, excitation of one side of the cerebrum causes the move- ments spoken of to occur on the opposite side of the bodv, and the same is true of the paralysis which follows di.sease or injurv. As a result of destruction of the Rolandic area degeneration FiUtt Cone Mid Bmin Fig. 302.— Degeneration after destruction of the Rolandic area of the right hemi- sphere (after Gowers). occurs, and its course is well shown in the illustration (Fig. 302), in which the shaded portions represent the parts that have under- gone degeneration. Speech-center. — Articulate speech requires the exercise of memory and the power of producing certain voluntarv move- ments. Inability to produce articulate speech is known as'aphasia. If the memory of words is absent while the power to produce the movements remains, it is amnesic aphasia, and if the reverse condition exists, it is ataxic aphasia. It is believed that the center which presides over language is in the frontal lobe on the left side, and has received from its discoverer the name of Brocn's convolutio7i. Some localize it in the third frontal convo- lution ; others regard it as being more diffused, and locate the center in the convolutions surrounding the lower end of the fissure 500 THE NERVOUS SYSTEM. of Sylvius. It is on the left side in persons that are right- handed, and on the right side in those that are left-handed. Sensory Areas. — When a sensory area is stimulated, the move- ment which results is reflex. Thus, if the auditory area, which was localized, perhaps incorrectly, by Ferrier in the superior temporosphenoidal convolution, is stimulated, the animal pricks up its ears and turns its head to the opposite side. If a sensory Fig. 303. — Base of brain : 1. 2, 3, cerebrum ; 4 and .^. longitudinal fissure ; 6, fissure of Sylvius; 7, anterior perforated spaces; 8, infundit)ulum : 9, corpora albi- cautia ; 10. posterior perforated space ; 11, crura cerebri : 12, pons Varolii ; 13, junc- tion of spinal cord and medulla oblongata; 14, anterior pyramid; 14'', decussation of anterior pyramid; 1.^, olivary body; 16, restiform body; 17. cerebellum; 19, crura cerebelli ; 21, olfactory sulcus; 22, olfactory tract; 23, olfactory bulbs; 24, optic commissure; 25, motor oculi nerve: 26, patheticus nerve; 27, trigeminus nerve; 28. abducens nerve; 29. facial nerve; 30. auditory nerve; 31, glo.ssopharyn- geal nerve ; 32, pneumogastric nerve ; 33. spinal accessory nerve ; 34, hypoglossal nerve. area is extirpated, there is a loss of the sense presided over by this area. Visual Area. — This is located in the occipital lobe and the angular gyrus. Auditory Area. — Ferrier located this in the superior temporo- sphenoidal convolution. The location of other areas is a matter of considerable doubt. 77//-; /.7M/.V. 501 Cranial Nerves (Fig. 303). — Tlu- cranial nerves have their oriiiiii in the ^ray matter at the base of tiie l)rain, and they escape from the skull by various openings, or foramina, to reach the parts to which they are distributed. The only exception to this is the spinal accessory, a part of which arises from the gray matter of the cord. Among the cranial nerves are those of special sense, of motion, and nerves having both motor and sensory properties. The points at which they leave the l)rain are spoken of as their apparent origin, but this is only apparent, for they can be traced into the brain-substance, to collections of nerve-cells, nerve- centers, to which the name nuclei has been given. The nucleus of a nerve is its real origin. Of cranial nerves there are 12 pairs, the number of each indicat- ing the order, from i)efore backward, in which it escapes from the cavity of the cranium: 1. Olfactory; 2. Optic; 3. Motor oculi communis ; 4. Patheticus or trochlearis ; 5. Trigeminus ; 6. Ab- ducens ; 7. Facial ; 8. Auditory ; 9. Glossopharyngeal ; 10. Pneu- mogastric; 11. Spinal accessory; 12. Hypoglossal. The first two nerves, the olfactory and the optic, will be considered in connection with the senses of smell and sight. Motor Oculi. — The third nerve, motor oculi, motor oculi com- munis, or oculomotorius, leaves the surface of the brain at the inner surface of the crus cerebri, just in front of the pons Varolii. Its real origin is, however, a nucleus in the floor of the aqueduct of Sylvius. It escapes from the cranium tiirough the sphenoidal fissure, and is distributed to the superior, internal, and inferior recti and to the inferior oblique. It also supplies the levator palpebrae superioris, and sends a branch to the ophthalmic, lenticular, or ciliary gang- lion. Another way to describe its distribution is to say that it supplies the levator palpebrse and all the muscles that move the eyeball, except the superior oblique and external rectus. The action of these muscles is largely indicated by their names. The levator palpebrae by its contraction raises the upper eyelid. The internal rectus turns the eyeball inward toward the nose, and the external rectus turns it outward. The direction and the point of attachment of the superior rectus are such that when it con- tracts the eyeball is not only turned upward, but it is also slightly rotated inward ; this is corrected by the action of the inferior oblique, so that the two acting together produce a movement directly upward. The same deviation inward follows when the eye is turned downward by the inferior rectus, and a similar cor- rection is made by the action of the superior oblique. If the external and superior recti act together, the movement of the eyeball is in the direction of the diagonal — that is, outward and upward ; the conjoint action of the external and inferior recti causes the eyeball to move outward and downward, and a corre- sponding action results when the other adjacent recti are brought 502 THE XERVOUS SYSTEM. into play. If the recti act alternately, the eyeball will be rotated completely, as in looking around a room from one side to the other and back again, from the floor to the ceiling. The motor oculi is purely a motor nerve. When stimulated, contraction is produced in the muscles to which it is distributed ; wiien the nerve is divided, these muscles are paralyzed. Paralysis of the Motor Oculi. — When the motor oculi is par- alyzed, the following are the results : (a) External strabismu-s, which consists in a turning of the eye outward. The retention of the eye in its normal position requires the conjoint action of the internal and external recti. In paralysis of the motor oculi the internal rectus has lost its innervation, and therefore its power to contract, and the external rectus, which receives its nervous supply from another nerve (the ab- ducens), having lost its antagonist, turns the eye outward. (h) Lascitas. — After external strabismus has been produced the eye remains in that condition, for the muscles which could move it in any other direction have been paralyzed. This immol)ility is called " luscitas." (c) Ptosis. — The levator palpebrs sujierioris is also paralyzed, and the upper eyelid droops, constituting ptosis. The ability to close the eye still remains, as this is the act of the orbicularis palpebrarum, which is not innervated by the third, but by the seventh, nerve. (d) Mydriasis. — A branoli of the motor oculi goes to the ciliary ganglion, which gives off the ciliary nerves that supply the iris. Accompanying the manifestations of paralysis of the motor oculi already mentioned there is in addition a dilatation of the pupil, or mydriasis. The diminution of the size of the pupil fdlowing the action of light upon the retina does not take place when this nerve is paralyzed. The contraction of the pupil is a reflex act requiring the integrity of the optic nerve, which serves as a carrier of the luminous impressions to tlie brain, and of the motor oculi, which is the efferent nerve in this act. (e) Pliability to Focus. — The muscle concerned in focusing the eye for short distances is the ciliary. The power to focus is lost in paralysis of the motor oculi. Paralysis of the motor oculi may be due to disease of the brain or to pressure on the nerve. If the trunk of the nerve is affected, all the physical signs mentioned may be observed, while if a single branch only is involved, the efi^ect will be limited to the part to which that branch is dis- tributed. Trochlearis. — The apparent origin of the trochlearis or patheti- cus is on the outer side of the crus cerebri, in front of the pons, and its real origin is a nucleus continuous with that of the motor oculi. The trochlearis leaves the cranium by the sphenoidal fissure, and is distributed to but one muscle, the superior oljlique. THE BRAIN. 503 AVhen this nerve is paralyzed the patient cannot turn the eye out- ward and downward ; the action of" the superior oblique is, there- fore, to turn the eye outward and downward. If the head is not turned toward either side when this nerve is paralyzed, the only tliiuii; observable is that the patient sees doul)le when he looks downward, and the image perceived by the affected eye is obliipie and below that seen by the eye that is affected. For a further discussion of the ocular muscles see p. 544. Trigeminus. — This nerve, which is also called "trifacial," has received its names from the fact that it has three subdivisions, and its latter name from the fact that is distributed in the main to Fig. 304. — General plan of the branches of the fifth pair: 1, lesser root of the fifth pair : 2, greater root, passing forward into the Gasserian ganglion ; 3, placed on the bone above the ophthalmic division, which is seen dividing into the supra- orbital, lacrimal, and nasal branches, the latter connected with the ophthalmic ganglion ; 4, placed on the bone close to the foramen rotundum, marks the superior maxillary division ; 5, placed on the bone over the foramen ovale, marks the inferior maxillary division (after a sketch by Charles Bell). the parts about the face. It arises by two roots, anterior and posterior. The anterior root, the smaller, is purely motor ; the posterior root, the larger, is sensory, and is characterized anatomi- cally by having upon it the Gasserian ganglion. The nerve leaves the brain at the side of the pons Varolii. The real origin of the motor root is a nucleus in the floor of the fourth ventricle ; the sensory root arises from a nucleus on a level M^th the middle of the superior peduncle of the cerebellum, just internal to the margin of the fourtii ventricle. Some authorities give it a more extensive origin, from the pons through the medulla and as far as the posterior cornua of the gray matter of the spinal cord. 504 THE NERVOUS SYSTEM. The motor root passes beneath the Gasserian ganglion, and takes no part in its formation. Beyond the ganglion the fifth nerve divides into three parts : (1) ophthalmic ; (2) superior maxillary ; and (3) inferior maxil- lary. (1) Ophthalmic Division. — This division, which leaves the cranium by the sphenoidal fissure, is distributed to the tentorium cerebelli, the eyeball, the Schneiderian membrane, the lacrimal gland, and the skin about the forehead and nose ; and also supplies branches to the ciliary ganglion. It contains fibers from the posterior root only ; none from the anterior. (2) Superior Maxillary Division. — This division of the fifth pair leaves the cranial cavity by the foramen rotundum. It is ilistributed to the dura mater, the sphenopalatine ganglion (Meckel's), the skin of the temple and cheek, the teeth, the gums, the mucous membrane of the upper jaw and upper lip, the mucous membrane of the lower part of the nasal passages, and the skin of the lower eyelid, side of nose, and upper lip. There are no fibers of the anterior root in this division. (3) Inferior Maxillary Division. — As has already been stated, there is no anatomic connection between the motor root of the fifth nerve and the Gasserian ganglion. From this ganglion are given off nerve-fibers which join the motor root, together making the inferior maxillary division, which escapes through the foramen ovale. It is distributed to the dura mater, the otic ganglion, the mucous membrane of the cheek and skin, the mucous meml)rane of the lower lip, the anterior wall of the external auditory meatus, the front of the external ear and the skin of the adjacent temporal region, the submaxillary gland and ganglion, the mucous mem- brane of the mouth and tongue ; to the papillae at the tip, the edges, and anterior two-thirds of the tongue, and to the teeth and gums of the lower jaw. It also supplies the following muscles : Temporal, masseter, pterygoid, mylohyoid, and anterior belly of the digastric. Physiologic Properties of the Trigeminus. — The trigeminus is the largest of the cranial nerves, and its functions are many and important. It supplies the parts to which it is distributed with the general sensibility they possess. If it is divided, there is complete absence of sensation (anesthesia) of the face on the cor- responding side. So pronounced is this anesthesia that no amount of irritation applied to such ordinarily sensitive parts as the cornea will produce any effect. An animal thus experimented upon seems entirely unconscious of the. irritation. Experimenters have gone so far as to exsect the eyeball and apply hot irons to the skin without causing pain to the animal experimented upon. Neuralgia of the face, headache, and toothache are all due to some interference with the normal functions of this nerve. It is THE BRAIN. 505 not an uncommon tliintr t" Inar patients complain of headaches whicli seem to tliem to l)e in the brain itself. These deep-seated headaehes may be due to affections (tf one or more of the recurrent branches which come off' IVom the divisions of the nerve, and wliich arc distributed to the dura mati-r and bones of the skull. Linr/iKil [Gustatori/) Xerve. — This nerve is sometimes called the " lingual branch of the fifth nerve." It is the branch which is distributed to the mucous membrane of the mouth and the gums, and to the mucous membrane and papilhe of the tongue. It suj)- plies the tongue with tactile sensibility, a (piality ol" great advan- tage in enabling one to detect the physical properties of food, to Figs. 305, 306. — Distributioii of the cutaueoii.s sensitive nerves iijion the head: omii. orni. the occiput, maj. and 7ninor (from the N. cervical II. and III.) ; am. N. auricular niajni. (from X. cervic. III.) ; cs, N. cervical superfic. (from N. cervic. III.) ; Vi. first branch of the fifth (so, X. supraorbit. ; st. X. supratrochl. ; it, X". infra- trochl. ; e, X. ethmoid.; /, X. lacrimal.); Fj, second branch of the fifth (sm, X. subcutan. malfe seu zygomaticus) ; Fs, third branch of fifth (at, X. auriculotempor. ; b, X. buccinator ; m, X. mental.) ; B, posterior branches of the cervical nerve. recognize in it the presence of hard objects which it would be injurious to swallow, and to determine when it is ready for deglutition. Besides this tactile sensibility the lingual nerve, according to some authorities, supplies the anterior two-thirds of the tongue with the sense of taste, a special sense, and this power is lost when the fifth pair or the lingual branch is divided. For a further consideration of this nerve see p. 523. Mastication. — The muscles that have been mentioned as receiv- ing branches of the inferior maxillary division are those concerned in the act of mastication. In this act the temporal and masseter close the mouth, the mylohyoid and diga.«tric open it, while the pterygoids produce the lateral movement of the lower jaw. Division of the inferior maxillary division paralyzes, therefore, all 600 THE XERVOUS SYSTEM. these muscles. If it is divided on one side, the muscles on the other side can still perform the act, but in an imperfect manner ; if divided on both sides, all masticatory movements will be abolished. Anastomosis of the Fifth Pair. — Besides the branches already mentioned, there are others which are termed anastomotic branches. Although the upper, middle, and lower parts of the face are sup- plied with sensation by the ophthalmic, superior maxillary, and inferior maxillary divisions respectively, still the boundaries of each are not absolute. Thus the skin of the nose is supplied by fibers from the ophthalmic and superior maxillary, and the skin of the temporal region is supplied from both the superior and inferior maxillary divisions. In addition to these branches, there are some which unite with other nerves and give a certain amount of sensibility to the parts to which these nerves are distributed. A striking: instance of this is the branch which anastomoses with the facial nerve. This nerve is at its origin purely motor, and is distributed to the uiuscles of the face. These muscles are endowed with sensibility ; but this is not due to fibers of the facial nerve, but to those of the fifth nerve, which anastomose with the facial and go with it to its termination in the muscles. Connection of the Fifth Pair with the Special Senses. — After division of the fifth nerve the special senses of smell, sight, taste, and hearing are seriously aiFocted. The Schneiderian membrane becomes SAVoUen, and later assumes a fungous condition and bleeds readily when touched. There is besides an accumulation of altered mucus in the nasal passages. The eye also undergoes marked changes : The conjunctiva becomes congested and the cornea opaque ; later, most of the structures of the eye suffer from inflam- matory changes to the degree of destruction. The sense of taste may likewise be lost, not only in the anterior two-thirds of the tongue, but also in the posterior third as well. Besides, the sense of hearing may also be greatly impaired. The explanation of these changes is not an easy one. Some authorities regard them as due to disturbance of trophic in- fluences. The nerve-fibers which form the posterior or sensory root of the fifth pair in passiug throuo^h the Gasserian ganglion are reinforced by fibers which have their origin in this collection of nerve-cells. Each of the three divisions of the trigeminus contains, therefore, fibers of the posterior root, and in addition fibers from the ganglion. The latter fibers are distributed to the structures to which the accessory fibers are distributed, and they are regarded as trophic nerves — that is, as nerves which regulate the nutrition of the parts to which they go. Among these parts are the mucous membrane of the nose, the cornea, the conjunctiva, and the tongue, and the loss of the special senses is believed to be due to altered nutrition of the affected parts. The sense of sight THE BRAIN. 507 is resident in the retina and optic nerve, but it may be as perfectly abi)lislied by rendering: opaque the tissues tiirou<^h which liuht reaches these structures as l)y dividin<^ tiic ()[)tic nerve. Thus in cases where a tumor presses upon the triucniiuus in front of the ij:;anglion, not only may there be an alteration of the nutrition of the skin of the face, as evidenced by an herpetic erujition, but tiiere may be also the corneal ulceration alreadv referred to. In like manner the olfactory nerves are the nerves of smell, but if the nasal mucous juembrane is so affected in its nutrition as to render the function of the nerves impossible, the sense of smell is as certainly abolished as if tiie olfactory bulb was broken up. This interference with the normal action of the nerves is seen in catarrhal affections of the nose, in Mhich the sense of smell is much obtunded and sometimes even lost. Some authorities, however, question the existence of specific trophic nerves. Stewart says that up to the present "?fo unequivo- cal proof, experimental or clinical, has ever been yiven of the exixtence of spjecific tropJiic nerves." These authorities consider that the inflammatory changes occurring in the eye, for instance, are due to the presence of foreign bodies lodging on the eyeliall, which has lost its sensibility ; that if the eye is so protected that irritating substances cannot injure it, tlie degenerative changes take place only after a considerable time ; and tliat when they do occur it is probably even then due to injury, for it is a most difficult thing to ]irotect the eye for a long time from all sources of irritation. Thus in a case reported by Shaw, in which both the fifth and the third nerves were paralyzed, due to the pressure of a tumor at the base of the brain, no change took place in the nutrition of the eye. The orl)icularis could still close the eye, and the protection which this gave was augmented by the ptosis. After manv months the growth of the tumor involved the facial nerve, and as the eye coidd then not be closed, inflammatory changes soon set in and sight was destroyed. Gowers also reports a ease in which the patient lived for seven years with complete paralysis of the fifth nerve, yet the eye re- mained free from disease and the sight was unimpaired. Kirkes, on the other hand, is an advocate of the existence of the *' trophic influence of nerves," although he states that the proof that there are distinct trophic nerve-fibers anatomicallv is not very conclusive. He thinks that the division or disease of the fiftii nerve, for instance, acts as a predi.y:>osing cause, and the dust which falls on the cornea as the exciting cause. He gives one instance of disturbance of nutrition which it is difficult to account for except on the theory of trophic nerves. He says : " Manv bed-sores are due to prolonged confinement in bed with bad nursing ; these are of slow onset. But there is one class of bed- sores which are acute : these are especially met with in cases of 508 THE NERVOUS SYSTEM. paralysis due to disease of the spinal cord ; they come on in three or four days after the onset of the paralysis in spite of the most careful attention ; they cannot be explained by vasomotor dis- turbance nor by loss of sensation ; there is, in fact, no doubt they are of trophic origin ; the nutrition of the skin is so greatly im- paired that the mere contact of it with the bed for a few days is sufficient to act as the exciting cause of the sore." The subject is one of great importance, but must be regarded as still unsettled. Ganglia of the Trige^ninm. — Besides the Gasserian ganglion, there are, in connection with the fifth nerve, four ganglia which are by some writers described as a part of the sympathetic system. They are the ciliary or ophthalmic, the sphenopalatine or Meckel's, the otic or Arnold's, and the submaxillary. The ciliary ganglion belongs, according to some authorities, to the third rather than to the fifth nerve. It is not larger than the head of an ordinary pin, and is situated in the orbit. The branches by which other nerves communicate with it are called its " roots " ; of these there are three : The sensory, from the ophthal- mic division of the fifth ; the 7notor, from the motor oculi ; and the sympathetic, from the cavernous plexus of the sympathetic. The nerves that go off from it are the short ciliary nerves, which, joining with the long ciliary nerves, form the nasal branch of the ophthalmic division, and together they are distributed to the ciliary muscle, the iris, and the cornea. These nerves supply motion to the sphincter and dilator pupillse, sensibility to the iris, choroid, and sclerotic, and vasomotor influences to the blood-vessels of the iris, choroid, and retina. If the trophic influence already spoken of exists, it must be conveyed to the eye through the ciliary nerves. The sphenopalatine or MeckeVs ganglion, which is the largest of the four, is situated in the sphenomaxillary fossa. This gang- lion also has three roots : The sensory, sphenopalatine, from the superior maxillary division of the fifth ; the motor, large superficial petrosal nerve from the facial ; and the sympathetic, large deep petrosal nerve from the carotid plexus of the sympathetic. The Vidian nerve is made by the union of these two latter nerves. The nerves from this ganglion are distributed to the posterior por- tion of the nasal passages and the hard and soft palate, giving them sensibility ; to the levator palati and azygos uvnlse, giving them the power of motion ; and to the blood-vessels of this region. The otic or Arnold's ganglion is situated on the inner side of the inferior maxillary division of the fifth, just below the foramen ovale. It likewise has three roots : The sensory, from the inferior maxillary and glossopharyngeal ; the motor, from the facial and inferior maxillary ; and the sympathetic, from the plexus around THE BRAIN. 509 the mciiingoal artery. Its branches of distributiou are to the tensor tympani, tlie tensor palati, and a small one to the chorda tynipani. The mucous mcmljrune of the tympanum and the Kustachian tube is also supplied by this ganglion. The subiit((.rill((ri/ (/(inylioii, which is situated near the sub- maxillary gland, receives branches of communication from the lingual branch of the fifth, ehonla tympani, and sympathetic plexus around the facial artery, its branches of distribution are to the mucous membrane of the mouth and AVhartou's duct, also to the submaxillary gland. Abducens. — This nerve, ^vhich has its real origin in the floor of the iburtli ventricle, emerges from the cranium by the sphe- noidal fissure, and is distributed to the external rectus muscle. It is a motor nerve, as is shown by the contraction of this muscle when the nerve is stimulated, and by its paralysis when the nerve is divided, Fdndysis of Abducens. — When from any cause this nerve is so injured as to deprive it of its function, the internal rectus, having lost its antagonist, the external rectus, turns the eye inward toward the nose, producing internal strabismus. There may also be some contraction of the pupil, because the radiating fibers of the iris, which cause dilatation of the pupil, are to a certain extent deprived of their innervation, this being supplied from the sympathetic, some of the nerves of wdiich system run along with the abducens, and when this nerve is injured, these sympathetic fibers may also be involved. It is said that the abducens is more frequently im- plicated in fractures at the base of the skull than any other cranial nerve. Facial Nerve. — The facial nerve leaves the medulla oblongata at the groove between the olivary and the restiform bodies. Its real origin is a nucleus in the floor of the fourth ventricle. It leaves the cranium by the internal auditory meatus, through which and the aqueduct of Fallopius it passes to emerge at the stylo- mastoid foramen. In the older nomenclature, in which there were but nine pairs of nerves, the facial was associated under the name of seventh nerve with the auditory nerve, in company Avith which it enters the auditory meatus ; the facial, from its firm consistency, being called the portio dura, and the auditory, on account of its opposite quality, being called the portio mollis. The facial has a very extensive distribution — the muscles of the face and external ear, the stylohyoid, posterior belly of the digastric, the platysma myoides, and the stapedius. It also gives off the chorda tympani, which is distributed to the submaxillary gland and ganglion, to the inferior lingualis muscle, and to the sublingual gland. Besides these it has most important branches of communication with the sympathetic system and with the glossopharyngeal, pneumogastric, and trigeminus nerves. 510 THE NERVOUS SYSTEM. Physiologic Properties of the Facial. — The facial is, origi- nally, a purely motor nerve, and whatever sensibility is possessed by the parts to which it is distributed is not due to facial fibers, but to anastomotic fibers from other nerves, principally the fifth. The most pronounced function of the facial is its relation to ex- pression. The so-called "■ expression " of the face is caused by different degrees of contractiou of the facial muscles, and the different expressions, such as of fear, of anger, etc., are due to con- traction of different muscles. The facial is therefore said to be the " nerve of expression," and when it is divided and the muscles paralyzed, the reason for this title is readily understood. Facial Paralysis. — When the facial nerve is divided or its functions otherwise abolished, the following are the results : (1) Efect of Paralysis on Facial Expression. — A complete loss of expression follows on the affected side ; the wrinkles on that side are obliterated and the face is flattened. (2) Efect of Facial Paralysis on the Eye. — The muscle which closes the eve is the orbicularis palpel^rarum ; this muscle is inner- vated by the facial nerve, and in paralysis, therefore, the eye remains permanently open, the power to close it being lost. Inas- much as the act of winking is but a rapid partial closing of the eye, this act is also abolished and the eyeball is liable to become dry. The act of winking spreads the tears which keep the eye moist. Unless provided against, this exposure of the eye may result in injury (p. 507). (3) Effect of Facial Paralysis on the Jlouth. — The mouth is drawn by the unparalyzed muscles to the unaffected side. It is impossible to approximate the lips of the affected side to a tumbler or cup ; consequently in drinking therefrom, unless the head is thrown back, fluids will dribble from the corners of the mouth. The buccinator muscle being paralyzed, food finds its way into the space between the cheek and the gum, and mastication is seriously impeded. The lips being paralyzed, the consonants b and p cannot be pronounced distinctly. (4) Efect of Facial Paralysis on Taste. — Accompanying facial paralysis may be impairment or abolition of the sense of taste. Authorities are not agreed as to the explanation of this result, but it is doubtless due to interference with the chorda tympani. Some attribute it to the influence which this nerve exercises over the circulation in the tongue and on the secretion of saliva : others regard the chorda tympani as the nerve of taste to the anterior two-thirds of tiie tongue, and as taking part in forming the gusta- tory nerve or lingual branch of the trigeminus. Indeed, there is a difference of opinion among anatomists as to the true source of the chorda tympani, at least so far as concerns those fibers which are connected with the sense of taste ; some look upon it as a part THE lUiAIX. oil of tlu' fif'tli, some as a part of the sevcnlh, and still otlicrs as a part of tlie ninth or glossopharyngeal. Auditory. — The anditorv nerve has its a])])arcnt origin from the lower bonier of the })ons, in tlie groove between the olivarv and restiform bodies. Its real origin is in tiie floor of the fonrth ventriele. As already stated, the anditorv nerve enters the in- ternal anditory meatns with the facial nerve. It is distributed to the internal ear, and is the special nerve of the sense of hearing. It will fnrther be discnssed in connection with that special sense. Glossopharyngeal. — The superficial origin of the glossopharvu- geal nerve is from the upper part of the meduUa, in the groove between the olivary and restiform bodies. Its real origin is a nucleus in the lower part of the floor of the fourth ventricle. It escapes from the cranium through the jugular foramen, together with the pneumogastric and spinal accessory nerves. Its branches of coinnuiuication are with the ])neumogastric, facial, and svmpa- thetic nerves. Tiie glossopharyngeal gives off the tympanic branch, the nerve of Jacobson, which is distributed to the fenestra rotunda, the fenestra ovalis, and the lining membrane of the tym- panum and Eustachian tube. As its name implies, the glosso- pharyngeal is distributed to the tongue and pharynx. The glossal portion supplies the mucous membrane of the posterior third of the tongue, the tonsils, and the pillars of the fauces and soft palate, while the pharyngeal portion is distributed to the pharyn- geal mucous membrane and to the muscles concerned in a part of the act of deglutition — namely, the styloglossus, digastric, and stylopharyngeus, and the superior and middle constrictors. Phifsio/ogic Properties. — Tiie sensil:)ility of the parts to which the glossopharyngeal nerve is distributed is due to this nerve. It is also a nerve of special sense, supplying the posterior third of the tongue and the palate with the sense of taste ; and, finally, it is the motor nerve for the muscles enumerated which are con- cerned in passing the food from the back of the mouth into and through the pliarynx to the esophagus in the act of deglutition. Vagus. — This nerve is also called pneumogastric, from two of the important organs, the lungs and stomach, to which it is dis- tributed. Its apparent origin is by eight or ten filaments from the groove below the glossopharyngeal, while its deep origin is from a nucleus in the floor of the fourth ventricle, below and con- tinuous with that of the same nerve. At the jugular foramen, by which it escapes from the cranium, is found the ganglion of the pneumogastric or the jugular ganglion. The pneumogastric receives branches from the spinal accessory, facial, hypoglossal, and anterior branches of the first and second cervical nerves. It assists in forming the pharyngeal, larvngeal, puhnonary, and esopliageal ]>lexuses. Among its important branches are the superior and inferior larvngeal nerves, the cardiac 512 THE NERVOUS SYSTEM. \\ " ^ 29 f ' Vj' ifV >^; I;' tt:^ % Fig. 307.— View of the glos.sopharyngeal, pnenniogastric, spinal arcessory, and hypoglossal nerves of the left side : 1, pneumogastric nerve in the neck ; 2, ganglion of its trunk ; 3. its union with the spinal accessory : 4, its union with the hypoglossal ; 5, pharyngeal branch ; 6, superior laryngeal nerve ; 7, external laryngeal ; 8, laryn- geal plexus; 9, inferior or recurrent laryngeal; 10, superior cardiac branch ; .11, middle cardiac; 12, plexiform part of the nerve in the thorax; 13, posterior pul- monary plexus; 14, lingual or gustatory nerve of the inferior maxillary; 15, hypo- glossal, passing into the muscles of the tongue, giving its thyrohyoid branch, and uniting with twigs of the lingual ; 16, glossopharyngeal nerve: 17. spinal accessory nerve, uniting by its inner branch with the pneumogastric, and liy its outer passing into the sternoniastoid muscle ; 18, second cervical nerve ; 19, third ; 20, fourth ; 21, origin of the phrenic nerve; 22, 23, fifth, sixth, seventh, and eighth cervical nerves, forming with the first dorsal the brachial plexus; 24, superior cervical ganglion of the sympathetic; 2.5, middle cervical ganglion: 26, inferior cervical ganglion united with "the first dorsal ganglion ; 27. 28, 29, 30, second, third, fourth, and fifth dorsal ganglia (from Sappey, after Hirschfeld and Leveille). and the gastric branches. The pharyn«:cal l)ranch is distributed to the mucous membrane and muscles of the pharynx and to the THE BRA IS. 513 muscles of the soft palate. Its esopliageal branches sup})ly tlie mucous membrane and nuiseuhir coat of the esopliagus, so that the act of detrhititiou, which begins in the mouth and is continued in the pharvnx, is completed by the esophagus. The superior laryngeal nerve is distributed to the erieotliyroid muscle and to the inferior constrictor, and communicates with the superior cardiac nerve. Its further distribution is to the mucous membrane of the epiglottis and larynx as far as the vocal cords. The superior laryngeal nerve is the sensitive nerve of the larynx. This sensibility is of great importance as a protection of the larynx and the respiratory organs below it from the entrance of foreign bodies, which would set up dangerous iuHammatory processes. The instant such a substance touches the surfaces sup- plied by this nerve a violent expulsive cough occurs which ejects it. If the nerve is paralyzed, as it may be after diphtheria or in con- nection with brain disease, this protection is absent, and, owing to paralysis of the cricothyroid, the ability to make tense the vocal cords is lost and the voice is hoarse. The inferior or recurrent laryngeal nerve is distributed to all the muscles of the larynx except the cricothyroid. It sends branches to the raucous membrane and muscular coat of the esophagus, to similar structures of the trachea, and to the inferior constrictor. It is the motor nerve of the larynx, and may be paralyzed under the same conditions as were mentioned in con- nection with the superior laryngeal, and all motion of the vocal cords is abolished. One nerve may alone be paralyzed, as when pressed upon by a tumor, when the corresponding vocal cord would alone be motionless. The cardiac branches of the pneumogastric terminate in the superficial and deep cardiac plexuses. The pulmonary branches assist in forming the pulmonary plexuses, the branches of which are distributed to the lungs. The esophageal branches form the esophageal plexus or plexus gulae. The gastric branches, which are the terminal filaments of the nerve, are distributed to the stomach and to the celiac, splenic, and hepatic plexuses, the latter two supplying the liver and spleen. In mentioning some of the branches of the pneumogastric, their functions have also been referred to. In addition tothese func- tions the movements of the stomach and the intestines are also performed under the influence of this nerve. It is through the cardiac branches that the inhibitory impulses from the medulla are sent to the heart. Through the pulmonary branches impulses reach the respiratory center and influence respiration. Reference has previously been made to the depressor fibers, which run in the pneumogastric to the vasomotor center, inhibiting its action and thus diminishing the work of the heart. Spinal Accessory Nerve. — This nerve has two parts — one arising 33 614 THE SERVO US SYSTEM. from a nucleus in the medulla below that of the pneumogastric, and the other from the iutermediolateral tract of the cord. The former is the accessory, and the latter the spinal, portion. The accessory portion joins the pneumogastric, and is distributed through the pharyngeal and superior laryngeal branches of that nerve. It is also probable that the fibers of the pharyngeal branch going to the muscles of the soft palate are fibers of this portion of the spinal accessory. The inferior laryngeal nerve also contains fibers from this nerve, probably from the internal, anastomotic, or accessory por- tion, and experiments demonstrate that the power which the larynx possesses to produce vocal sounds is due to these fibers, for when the spinal accessory is torn out this power is lost. The other move- ments of the larynx, those which take place during respiration, are not interfered with under these circumstances, but only those of phonation. The inferior laryngeal nerve is, then, only par- tially made up of spinal accessory fibers : these fibers preside over phonation. The other fibers, which are prol^ably derived from the facial, hypoglossal, or cervical, or all of them, provide the nervous influence for the other movements. If the entire nerve is divided, the laryngeal movemeutsofl)oth phonation and respiration will cease. The spinal or external portion is distributed to the trapezius and sternomastoid muscles; it is therefore sometimes called the "muscular branch." This branch is believed to be brought into requisition when these muscles are needed for more than their ordinarv activity, for the nervous force to supply the latter is fur- nished by cervical nerves. In unusual straining or in lifting, or in the production of prolonged cries, these muscles are brought into action, and to supply the additional innervation which these acts seem to require is believed to be the office of the muscular branch of the eleventh nerve. The spinal accessory is, then, a motor nerve, althougli some writers regard a portion of the fibers of the accessory part as being sensory. Hypoglossal. — The apparent origin of this nerve is by filaments, from 10 to 15 in number, from the groove between the pyramidal and olivarv bodies : its real origin is in a nucleus in the floor of the fourth ventricle. It sends branches of communication to the pneumogastric, the sympathetic, the first and second cervical, and the gustator\\ It is distributed to the sternohyoid, sternothyroid, omohyoid, thyrohyoid, styloglossus, hyoglossus, geniohyoid, and genio'hyoglossus muscles. It is a motor nerve to the tongue, so much so that it has been called the " motor linguae." The move- ments over which it presides are those concerned in mastication and deglutition and in the production of articulate speech. "When this nerve is paralyzed on one side, the tongue, when protruded, is directed toward the paralyzed side. When both nerves are involved in the paralysis all motion of the tongue ceases. THE SENSES. 51 o THE SENSES. It is by the senses that the iiulivichial is i)roiight into relation with the worM ontsitle him. The senses are five in number: (1) General sensibility ; (2) Smell ; (3) Taste ; (4) Sight ; and (5) Hearing. General Sensibility. — This kind of sensibility is so called because it is generally distributed over the entire bodv in the skin, and in those parts of mucous membrane adjacent to the skin. It is composed of a variety of sensations which are excited by a variety of stimuli, but it is still an unsettled question whether the nerves which conduct the impulses that excite these sensations are in all instances the ordinary sensory nerves of the skin, or whether they are special nerves, each one conducting only its own special stimulus. In treating of the subdivisions of general sensibility this question will again be referred to. Sense of Touch. — The sense of touch, or tactile sensibility, de- pends upon the existence of nerves and nerve-endings (p. 64) in the skin and other portions of the body in which the function exists. It gives knowledge of such qualities as hardness or soft- ness, roughness or smoothness, sharpness or dulness, etc. ; by it we become acquainted Mith the shape and consistency of objects, and are made aware of the presence or absence of irritating quali- ties in certain substances. The pungent vapors of some gases excite in the nose the ultimate fibers of distribution of the fifth pair of nerves, and not those of the first pair, and it is incorrect to describe this sensation as a smell. It is as truly a tactile sensa- tion as when a sharp-pointed instrument is brought in contact with the skin. The same is true of pungent liquids applied to the tongue, which are commonly, but erroneously, said to be tasted. The difference in the tactile sensibility of different portions of the body is shown in the following table : Table of Variations in the Tactile Sensibility of Different Parts. The measurement indicates the least distance at which the two points of a pair of compasses can he separately distinguished (E. H. "SVeberj. Tip of tongue 1 mm. Palmar surface of third phalanx of forefinger . ... 2 ■• Palmar surface of second phalanges of fingers 4 " Eed surface of under lip 4 " Tip of the nose 6 " Middle of dorsum of tonsjue 8 " Palm of hand " 10 " Center of hard palate 12 " Dorsal surface of first phalanges of fingers 14 " Back of hand 25 " Dorsum of foot near toes 37 " Gluteal region 37 " Sacral region 37 " 516 THE NERVOUS SYSTEM. Table of Variations, Etc. — Continued. Upper and lower parts of forearm 37 mm. Back of neck near occiput 50 " Upper dorsal and mid-lumbar regions 50 " Middle part of forearm 62 " Middle of thigh G2 " Mid-cervical region 62 " Mid-dorsal region 62 " Weber, who has investigated tlioronghly the subject of tactile sensibility, says that in order to distinguish the two points of the compasses as such, there must be unexcited nerve-endings between the points of tlie skin that are touched by them, and the greater the number of these, the more distinctly are they recognized as being separate. Tactile sensibility is a function which can be educated to a high degree. Case of Laura D. Bridgman. — No better illustration could be given of the degree of perfection to. which this sense can be brought than that of the deaf, dumb, and blind girl, Laura Dewey Bridgman. When about two years old this child had scarlet fever, as a result of which she lost the senses of sight, hearing, taste, and smell. Although, about eleven years after, the sense of smell returned to a slight degree, the other senses mentioned were permanently absent. . In describing her case. Prof. Mussey, Prof, of Anatomy and Surgery at Dartmouth College, Hanover, N. H., where Laura lived, states that she possessed not merely " touch proper," but the capacity for " acute " sensations, pleasant or pain- ful ; the sensations of pressure, weight, temperature, and " mus- cular sensations." In speaking of this girl, her instructor said : " With regard to the sense of touch, it is very acute, even for a blind person. It is shown remarkably in the readiness with which she distinguishes persons. There are forty inmates in the female wing, with all of whom, of course, Laura is acquainted ; whenever she is walking through the passageways, she perceives by the jar of the floor or the agitation of the air that some one is near her, and it is exceed- ingly difficult to pass her without being recognized. Her little arms are stretched out, and the instant she grasps a hand, a sleeve, or even a part of the dress, she knows the person, and lets them pass on with some sign of recognition. Her judgment of dis- tances and of relations of place is very accurate ; she will rise from her seat, go straight toward a door, put out her hand just at the right time, and grasp the handle with precision." From her Life and Education it is impossible to ascertain what abilitv Laura possessed of distinguishing colors. Her historian says that it has been stated that she could tell the color of every- thing by feeling, but that this is not true. He further says that fabulous stories have been told of the power of the blind to dis- tinguish color, but such statements could not be made of those in GENERAL SENSIBILITY. 517 the institution with wiiich .slic was connected. " It is trueof numy totally blind that, it" a number of balls of worsted of various colors are given them, and they are obliged to notice them care- fully in order to use them in their proper j)laces in work, they will rarely make a mistake. So we may give th(,'m pieces of silk, with the same result ; but this does not prove that, having been told the colors in one material or fabric, they will recognize them in any other. " We have no evidence that there is any inherent property in the color red, or blue, or yellow, which will enable the most sensi- tive touch to detect each in all materials offei'ed." Sense of Pressure. — When objects are laid upon the hand there is a sensation produced, which is that oi' pressure, and by the exer- cise of this sense we are able to distinguish differences in the weights of objects. This is true of other portions of the body as well as of the hand. Sense of pressure and tactile sensibility are not identical ; indeed, portions of the body in which the latter is very acute are nevertheless very insensitive to pressure. Thus the tactile sensibility of the tip of the tongue is very highly devel- oped, but its sense of pressure is very deficient. Kirkes says that with the tip of the tongue one cannot detect the radial pulse. While there is a marked difference between the tongue and the finger in their ability to distinguish the pulse-beats, still the writer is positive that the statement that these cannot be felt by the tongue is not true for all individuals. It is to be borne in mind that in the investigation of the sense of pressure the muscles must not be brought into play, otherwise a new factor is involved — the muscular sense. Muscular Sense. — This sense is brought into action in lifting weights, and the estimation of the weight of an object depends upon the amount of nervous energy (efferent impulses) necessary to accomplish the result. Some authorities regard it as a modifica- tion of the sense of pressure ; but the two senses are undoubtedly distinct. Sense of Temperature. — By this sense the difference in tem- perature of bodies is recognized, and it is a well-known fact that the various portions of the body are endowed with different degrees of sensil)ility in this regard : The hand will bear a degree of heat which would cause great pain to some other parts of the body. The sense of temperature and that of touch are entirely distinct, and this fact may readily be demonstrated by pressing firmly on a sensitive nerve until the part to which it is distributed is almost devoid of the sense of touch, when it will be found that the sense of temperature is unaffected. N-ot only is the sense of temperature distinct from other sensa- tion, but even this is so subdivided that there are heat spots and cold spots — that is, portions of the skin which are excited by heat 518 THE NERVOUS SYSTEM. anJ cold respectively. Thus if a lieatecl object is moved about over the skin, at some points tactile sensibility alone will be excited, while at others the object will feel distinctly hot. In like manner cold spots will be recognized by the application of a cold object. This test applied to the skin of the forearm has resulted in such a chart as is shown in Fig. 308. Sense of Pain. — AVhen the stimuli that call out the sense of touch or of temperature are excessive, the sense of pain is pro- duced, and the other sensations are abolished ; thus when a piece i I ■■.. .Ji • • • , •<.::::::::: Fig. 308. — Cold and hot spots from the same part of the anterior surface of the forearm : a. cold-spots ; 6. hot-s]>ots. The dark parts are the more sensitive ; the hatched the medium ; the dotted the feeble ; and the vacant spaces the non- sensitive. of iron very much heated burns the hand, the sensation is the same as Avhen the iron is very cold. Some authorities regard the sense of pain as being a distinct sensation, others as simply an exaggeration of other sensations. Sense of Smell. — In the consideration of the respiratory processes the nose was described as being a part of the respiratory tract (p. 342). This is true of the lower portion of the nasal cavity, the entrance or regio vestibularis and the rcgio respiratoria, the rest of the lower part of the nasal cavity; the upper part, however, is more especially concerned with the function of smell, and is therefore called regio o/facforia. This portion of the raucous membrane is sometimes denominated olfadory membrane, and may be defined as that portion of the Schneiderian membrane which covers the superior and middle turbinated bones and the upper part of the septum nasi. The Schneiderian membrane lines the nasal fossae. Before the time of Schneider, from whom the mem- SENiSI'J OF SMELL. 519 n- v~^' l)r:uu' was luuiu'd, it was thought that the secretion it forms came from the l)rain : he (Imnonstvatcd that it came from the membrane itself It is covered by epithelium, which, near the orifice of the nostril in the vestibuh;, is pavement, but elsewhere, except ou the olfactory membrane, this epithelium is columnar and ciliated. In man the olfactory membrane is soft, vascular, and of a yellow color. It is covered by e})ithelium comj)osed of two varieties of cells, with a superficial lamina tiirouo;]! which the ends of the cells pro- ject. One variety, olfiuiory or otfactorlal cells, is spindle-shaped and bipolar (Fig. 309), having a nu- cleus. One of the poles extends to the surface, its extremity passing through the lamina, and in amphibia, reptiles, and l)irds terminates in fine, hair-like filaments. It is uncertain whether these filaments exist in mammals. The other pole extends downward and is connected with one of the fibrils of the olfiictory nerve, and passes through the cribriform plate of the ethmoid bone, and arborizes within one of the olfactory glomeruli (Fig. 310). The other variety of cells is the columnar or sustenfacular cell. These are columnar epithelium-cells with nucleated cell-bodies at the free surface of the mucous membranes and branching processes extending down- ward : they are supporting cells. The coriiim of the olfactory membrane is very thick and vascular, with bundles of olfactory nerve-fibers and a large number of serous glands, Boiv- man's (glands, whose ducts open upon the surface of the membrane between the epithelial cells. Olfactory Nerves. — These are about twenty in number, non-medullated, and are given off from the olfactory bulb. They pass through the cribriform plate of the ethmoid bone and are distributed to the olfactory membrane. Olfactory Bulb. — This is in reality a portion of the hemispheres, and is described as "a cap superimposed upon a conical process of the cerebrum." It consists of gray and white matter, and is thus described by Schafer : " Dorsally there is a flattened ring of longitudinal white bundles enclosing neuroglia, as in the olfactory tract ; but below this ring several layers are recognized, as follows : M" >:re Fig. 309. — Olfactory mucous membraue : a, sustentacular cells ; h, olfactory cells ; c, basal cells; (I, submucous fibrous tis- sue ; e, glands of Bowman ; I, nerve-fibers (Leroy). 520 THE NERVOUS SYSTEM. " 1. A white or medullary layer, characterized by the presence of a large number of small cells ('granules') with reticulating bundles of medullated nerve-libers running longitudinally between them. " 2. A layer oj large nerve-cells, with smaller ones intermingled, the whole embedded in an interlacement of fibrils which are mostly derived from the cell-dendrons. From the shape of most of the large cells of this layer it has been termed the ' mitral ' layer. These cells send their neurons upward into the next layer, Fig. 310. — Diagram of the connections of cells and fibers in the olfactory bulb: olf.c, cells of the olfactory mucous membrane; olf.n, deepest layer of the bulb, composed of the olfactory nerve-fibers which are prolonged from the olfactory cells ; gl, olfactory glomeruli, containing arborization of the olfactory nerve-fibers and of the dendrons of the mitral cells; m.c, mitral cells; a, thin axis-cylinder process passing toward the nerve-fiber layer, n.tr. of the bulb to become continuous with fibers of the olfactory tract ; these axis-cylinder processes are seen to give oflf collaterals, some of which pass again into the deeper layers of the bulb; n , a nerve- fiber from the olfactory tract ramifying in the gray matter of the bulb (Schiifer). and they eventually become fibers of the olfactory tract and pass along tliis to the base of the brain, giving off numerous collaterals in the bulb as they pass backward. " 3. The layer of olfactory glomeruli consists of rounded nest- like interlacements of fibrils which are derived on the one hand from the terminal arborizations of the non-medullated fibers which form the subjacent layer, and on the other hand from arborizations of descending processes of the large ' mitral ' cells of the layer above. "4. The Layer of Olfactory Nerve-fibers. — These are all non- SENSE OF SMELL. 521 racdullatod, ami aiv continiieil from the olfactory fibers ot" the Soliiioiderian or oltaetory mucous membrane ot" the nasal fossae. In this mucous membrane they take origin from tlie bipolar olfactory cells which are characteristic of the membrane, and they end in arborizations within the olfactory irlomeruli, where they come in contact with tlie arborizations of the mitral cells." Olfactory Tract. — This structure is an outgrowtii from the brain, which is in man at one period of development liollow, but later the cavity is filled with neuroglia, outside of which are bundles of white fibers, and still more external is a layer of neuroglia. There Mitral cells. f Large I nerve- Molecu- J cell, lar layer. 1 Small nerve-""*" L cell, r Layer of olfactory ■{ glomeruli. Peripheral nerve-' fibers. Fig. 311.— The olfactory bulb, after Golgi and Ramon y Cajal. The granular layer is not shown. are no nerve-cells in the tract. It lies in the olfactory sulcus, a depression in tlie under surface of the frontal lobe of the cere- brum, and terminates in the olfactory bulb. Traced backward, the tract is found to be made up of two roots, external and in- ternal ; between these is the trigonum olfactorium, which is some- times called the middle or r/raj/ root, but which is in reality cortical grav matter. The external root is connected with the end of the hippocampal gyrus, and the internal with the beginning of the gyrus fornicatus. Functions of the Olfactory Nerves. — The olfactory nerves are bevond all doubt the channels by which olfactory impressions reach the brain (Fig. 312). They are nerves of the special sense 522 THE NERVOUS SYSTEM. of smell. The whole mucous membrane of the nose is not sup- plied with olfactory fibers ; hence only in that part where they are present, the olfactory membrane, does the sense of smell reside. The proof that the function of these nerves is tliat of smell is derived from experiments upon lower animals and from observa- tions upon man. Animals whose sense of smell is very acute have the olfactory bulbs and tracts more highly developed — that is, these structures are larger — than in those animals in which the acuteuess of the sense of smell is not marked. If the tracts are destroyed, the sense of smell is abolished. Although this experi- FiG. 312 . — Nerves of the outer walls of the nasal fossse : 1, network of the branches of the olfactory nerve, descending upon the region of the superior and middle turbinated bones; 2, external twig of the ethmoidal branch of the nasal nerves; 3. sphenopalatine ganglion ; 4, ramification of the anterior palatine nerves; 5, posterior, and 6. middle, divisions of the palatine nerves; 7, branch to the region of the inferior turbinated bone : 8, branch to the region of the superior and middle turbinated bones ; 9, nasopalatine branch to the septum cut short ( from Sappey, after Hirschfeld and Leveille). mental proof is not applicable in man, still there are cases on record in which an absence of the sense of smell during life has been found after death to have accompanied an absence of the olfactory tracts ; and there are cases also of individuals whose sense of smell has been seriously impaired after injury to the tracts. During ordinary respiration the inspired air does not pass over the olfactory membrane, but only over the lower part of the Schneiderian membrane, the respiratory portion. Hence if odors are faint, they are not detected, unless by a strong inspiration the air is carried up to and over that portion to which the olfactory nerves are distributed. If the nasal passages are closed by a catarrhal condition, the sense of smell is obtunded or may even be abolished temporarily. SENSE OF TASTE. 523 It is important to dislinguisli botwooii tlie sense of smell and general sensibility. The nuicous membrane ot' the nose has, in common with otlier miieous membranes and the skin, the power to recognize such physical properties in objects as consistency, temperature, etc. Thus if a sharp instrument was to be brought in contact with this membrane, it would be recognized as sharp, but this recognition is not due to the excitation of the olfactory ncrvi's, but to the fibers of the trigeminus. The mucous mem- brane is therefore supplied by two nerves, the olfactory and the lifth. One is not liable to confound sharpness with odor, but the irritating effects of certain substances are often confounded with the sense of smell, when, as a matter of fact, it is not the olfactory, but the fifth pair, which is excited. Thus if acetic acid is brought in contact with the mucous membrane of the nose, it will excite the fibers of the fifth pair and will produce an irritating effect, but it would be incorrect to say that we smelled it. If, however, vinegar was substituted for the acetic acid, we should have the irritating effect of the acetic acid it contains, and in addition the olfactory nerves would be excited by the aromatic ingredients which, with the acid, form vinegar ; and it would therefore be cor- rect to say that we smelled the vinegar. The acuteness of the sense of smell differs in different indi- viduals, but in most it is well marked. It has been estimated that 2in)h~ooT o^ ^ milligram of musk may be detected by this sense. The emanations from objects which excite the sense of smell pro- duce this effect by stimulating the olfiictory cells, and the impulses are carried by the olfactory nerves to the brain. Case of Julia Brace. — A remarkable instance of the acuteness of the sense of smell is that of Julia Brace, an inmate of the Hartford Asylum, who became entirely deaf and blind at the age of four years and five months. The history of this case is given in the Life and Education of Laura I). Bridgman, by M. S. Lamson. This girl could select by the sense of smell her own clothes from a mass of dresses belonging to a hundred and thirty or forty persons. "She could discriminate, merely by smelling them, the recently Avashed stockings of the bovs at the asylum from those of the girls. Among a hundred and twenty or thirty teaspoons used at the asylum she could distinguish those of the steward from those of the pupils." Her sense of touch was also acute. " By putting the eye of a cambric needle upon the tip of her tongue, she could feel the thread as it entered the eye and pressed upon her tongue, and she would thus thread the needle." Sense of Taste. — The sense of taste exists to a slight degree in the middle of the dorsum of the tongue, but is especially de- veloped in the posterior third of the dorsum. It is also present in its tip and edges and in the soft palate, but the exact area in which it resides has never been determined. 524 THE NERVOUS SYSTEM. The nerves supplying the anterior two-thirds of the tongue are the lingual branch of the fifth pair, and the chorda tynipani, while the posterior portion is innervated by the glossopharyngeal. Some authorities regard the glossopharyngeal as the sole gustatory nerve, and attribute to the lingual branch only tactile properties, while others hold that the fifth nerve is the true nerve of taste, and that whatever function the glossopharyngeal seems to have in this re- FiG. 313. — Papillar surface of the tongue, with the fauces and tonsils : 1, 1, cir- cumvallate papillse, in front of 2, the foramen csecum ; 3, fungiform papillae ; 4, fili- form and conical jiapillse ; 5, transverse and oblique rugpe ; ti. mucous glands at the base of the tongue and in the fauces : 7, tonsils ; 8. part of the epiglottis ; 9, median glosso-epiglottidean fold (frsenum epiglottidis) (from Sappey). spect is derived from the fifth through anastomosis. It must be regarded as an unsettled question. The mucous membrane of the tongue is covered with papillae, Ungual 'papillce, of three varieties — circumvallate, conical, and fungiform. The circumvallate papillae (Fig. 313), about twelve in number, form the boundary between the anterior two-thirds and the posterior SENSE OF TASTE. 525 third of tlu' tdiigiic. Hk'v lire arning(!(l in V shape, the apex l)eing backward. In these papilhc are the tade-hud.s, and with these tlie gh)ss(>pharvn<>;eal nerve is in coninninication. The conical papillae, so called from their conical-pointed epithe- lial ca])s, are present throughout the rest of the lingual mucous membrane. Some of these, jUiform papUkc (Fig. -315), possess tine epithelial (ihiments in the cap. The fungiform papillae (Fig. 31G) are larger than the conical and scattered among them. They are highly vascular. Between the superficial lingual muscles are tubular glands, whose ducts open on the surlace. These are principally mucous Epithelium. \ i Taste-buds. ^ . Groove sur- rounding papilla. >-*"^ r^^v^ "-y -U: Ebner's .^.-.v gland. Fig. 314. — Longitudinal section of a human circumvallate papilla ; X 20 (Bohm and Davidoif). glands; but some are serous, glands of Ebner, and these latter open into the fossae of the circumvallate papillae ; their secretion is regarded by Ebner as assisting in the distribution of substances to be tasted over the taste-area. Taste-buds (Fig. 317). — These occur in both the circumvallate and fungiform papillae, and also in the epithelium of the general mucous membrane of the tongue, especially in that of the dorsum and sides. They are also found on the under surface of the soft palate and on the epiglottis. They are thus described by Schiifer : " The taste-buds are ovoid clusters of epithelium-cells which lie in cavities in the stratified epithelium. The base of the taste-bud rests upon the corium of the mucous membrane, and receives a 526 THE NERVOUS SYSTEM. branch of the gh^ssopharyngeal nerve ; the apex is narrow and communicates with the cavity of the mouth In- a small pore in the superficial epithelium — gustatory pore. " The cells which compose the taste-buds are of two kinds, viz.: 1. The gustatory cells, which are delicate fusiform or bipolar cells composed of tlie cell-body or nucleated enlargement, and of two processes, one distal, the other proximal. The distal process is nearly straight^ and passes toward the apex of the taste-bud, J- — - Papilla filiformis. . , _ Tongue epithe- lium. k Connective-tissue papilla. ^:. Mucosa. ^■^: • y ' ' '" ' ' ,' " ,' =i2ll Basal epithelial ■ , layer. Fig. 315. — From a cross-section of the human tongue, showing short, thread-like papiUse (filiform) ; X 140 (Bohm and Davidoff). where it terminates in a small, highly refracting cilium-like appendage which projects into the bottom of the pore above mentioned. The proximal process is more delicate than the other, and is often branched and varicose. The nerve-fibers take origin in ramifications among the gustatory cells (Retzius). " 2, The sustentacular cells (Fig. 318). — These are elongated cells, mostly flattened, and pointed at their ends ; they lie between the gustatory cells, which they thus appear to support, and iu addition they form a sort of envelope or covering to the taste-bud. SENSE OE TASTE. 527 Between the cells of the tnste-l)U(ls lyniph-eorpuscles are often seen, having probably wandereU hither from the subjacent mucous membrane." "^ ^^''■' K' Fig. 316. — Fungiform papilla from human tongue (Huber). Fig. 319 shows the nerve-endings in the taste-buds. Tlie fact that the general sensibility of the tongue may be lost and the sense of taste remain indicates that the channels for the 1= ?^Vi;-i.>-., - * Fig 317 —Longitudinal section of foliate papilla of rabbit, showing taste-buds (Huber). transmission of these two sensations are different. It may be well again to call attention to the necessity for making a distinction between what raav be tasted and what may be smelled, between savors and flavors. The sense of taste gives cognizance of the 528 THE NERVOUS SYSTEM. Process of neuro-epi- Epithe- Nerve- thelial Taste- lium. fibrils. cell. pore. .Tegmental ^s/f^^ cell. ' "rtl_ii!ik_Neuro-epithe- Sustontacular cell. Terminal branches of nerves. Fig. 318. — Schematic representation of a taste-goblet (partly after Hermann). qualities siveet, acid, hitter, and saline; but to speak of an oily taste is incorrect : such a quality appeals to general sensibility only. The tip of the tongue is most sen- sitive to sweet tastes, the sides to acid, and the back to bitter. Conditions of the Sense of Taste. — That the sense of taste may be exercised requires the presence of certain conditions, one of which is that the substance must be in a state of solution or be soluble in the saliva. Insoluble substances are tasteless : for this reason calomel is especially suitable as a cathartic for children. Another condition is that the mucous membrane of the mouth must be moist. AVhcn the mouth is dry and substances not already in a state of solution are taken in, there is no saliva present to dissolve them ; consequently they are not tasted. This absence of taste is very marked in the parched con- dition of the mouth occurring during fevers. To excite the sense of taste, sapid sub- stances must pass by osmosis into the pa- pillse of the mucous membrane and there stimulate the terminal filaments of the nerves which preside over this sense. An important agent in causing this absorption is the Fig. 319. — Nerve-endings in taste-buds : w, nerve-fibers of taste-buds, b : i, ending of fibrils within taste-bud; p, ending in epithelium be- tween taste-buds; s, surface epithelium (G. Retzius). SENSJ-: OF SKUIT. 529 movenu'nt of the tongue. It is a iiiattcr of" cominon observation that if sapid substances are simply placed on the ton«rue, the sense of taste is not excitcid ; but if the toni^ue is jiressed against the roof of the moutli, absorj)tion is [)roni<)te(l and the gustator\ (pial- ities are at once recognized. It is to be noted also tiiat a savor persists for a certain length of time, and that if it is desired to ly thicker than the rod-fiher, passes inward, to terminate by an expanded arborization in the f>uter moiecMJar layer; here it comes into relation with a similar arborization of dendrons of a cone-bipolar. The cone ])roper, like the rod, is formed of two segments, the outer of which, much the smaller, is transversely striated, the inner, bulged segment being longitudi- nally striated. The inner ends of the rod- and cone-fibers come, as already stated, in contact with the ])eripheral arborizations of the inner granules, and through these elements and their arljori- zations in the inner molecular layer a connection is brought about with the ganglionic cells and nerve-fibers of the innermost lavers. There appears, however, to be no anatomic continuity between the several elements, but merely an interlacement of ramified fibrils. 10. Fi(/}iieuf retina at the vellow spot, except at the fovea centralis, is thicker than elsewhere ; the middle of the fovea is the thinnest part of the retina. The ganglion- cells are more numerous in the macula, as are the cones when com- pared with the rods. In the fovea the rods are absent, and the 542 THE NERVOUS SYSTEM. cones are long and slender. Tliis portion of the retina consists of but little else than cones and the outer nuclear layer; the cone- fibers are very distinct and nearly horizontal. Pars Ciliaris Retinae. — At the ora serrata the pars optica retinae terminates, and the pars ciliaris retinae begins. It consists of two layers : An external layer of pigment-cells which are the continuation of the tapetum nigrum, and an internal, of columnar cells with oval nuclei, raoditied fil)ers of Midler. The picrmented epithelium is continuous with the uvea of the iris. The sensory epitlieliuui receives its nourishment from the blood-vessels of the choroid. Anterior and Posterior Chambers. — The anterior chamber is that portion of the cavity of the eye situated between the cornea and the iris ; the posterior chamber, the space between the iris in front ; and the capsule of the lens, the suspensory ligament and the ciliary processes l)ehind. Inasmuch as the iris is in contact with the capsule for the greater part of its extent, this "chamber" is ex- ceedinglv small, and hardly deserves the name. In fetal life these two chambers are separated l)y the membrana j^upillaris, but about the seventh or eighth month, when the membrane begins to be ai:»sorbed, they becouie one cavity, and are filled with aqueous humor (p. 544), Some authorities describe the cavity containing the vitreous under the name " posterior chamber." Vitreous Body. — This is called also vitreou.s humor. It is a transparent, jelly-like material which fills the cavity of the retina and is enclosed in a delicate membrane, tiie hyaloid membrane. At the pars ciliaris retinae this membrane splits into two layers, an anterior and a posterior. The anterior layer becomes the suspen- sory ligament of the lens, while the posterior passes behind the lens and covers the anterior portion of the vitreous ; at this part there is a depression in the vitreous in which the lens lies. In the vitreous are found rtl)ers and some cells, the bodies of which con- tain large vacuoles and give off long and varicose processes. Through its center in fetal life runs a small artery from the arteria centralis retinae to the capsule of the lens, but in the adult this is a simple channel, canal of Stilling, which is lined by a portion of the hvaloid membrane. Crystalline Lens (Fig. 332). — The lens is a transparent body, biconvex in form, the convexity being greater posteriorly than anteriorly. Its transverse diameter is about 0.8 cm., and its anteroposterior diameter about 0.6 cm. It consists of concentric lavers or laminae ; those that are centrally situated form the nucleus, and are harder than the external, which are relatively soft. If the lens is boiled or hardened in alcohol, these laminae may be peeled off like the coats of an onion. The laminae are coniposed of long fibers with serrated edges, which fit into corre- sponding serrations of adjoining fibers. When cut transversely, SENSE OF SIGHT. o4:ht about hy tlie conjoint .4 t 6 tj Fig. 335. — Movements of the eyeballs: 1, inferior oblique; 2, superior rectus; 3, external rectus; 4, internal rectus; 5, sujjerior oblique ; 6, inferior rectus. action of the superior rectus and the inferior oblique. The in- ferior rectus turns the eye downward and inward ; when the eye is turned directly downward, tliis is effected by the conjoint action of the inferior rectus and the superior oblique. The internal Fig. 336. — Horizontal section of left eye. Arrows show direction of pull of the muscles. The axis of rotation of the external and internal recti would pass through the intersection of a and ^ at right angles to the plane of the paper (Stewart). rectus turns the eye inward ; the external rectus turns it outward. The superior oblique rotates the eye outward on its anteroposterior axis, and corrects the inward deviation of the inferior rectus. The inferior ohlicpie rotates the eyeball outward on its anteroposterior axis, and corrects the inward deviation of the superior rectus. 548 THE XERVOUS SYSTEM. Physiology of Vision. — The eye has very aptly been compared to a photographic camera, tlie transparent structure, through which pass the rays of light, representing the lenses, and the retina representing the sensitive plate on which the image is received, while the pigmented choroid coat is the representative of the lampblack with Avhich the photographer darkens the interior of the camera-box to prevent any reflected light striking the plate and interfering with the sharpness of the picture. In the camera, in order to bring to a focus upon the plate the rays of light coming from objects at different distances, the photographer uses a focus- sing screw, by which the lens may be moved nearer to or farther from the object he wishes to photograph ; and in order that clear images may be obtained by the eye it is necessary to accomplish the same result, for when the eye is focussed for near objects, those at a distance are blurred, and vice versa. This fact may readily be demonstrated by looking through a piece of mosquito-netting at the windows of a house on the opposite side of a street. When Fig. 337.— Principal focus of a lens. The parallel rays, a, h, c, d, are refracted by the lens so as to unite at the point F on the axis P; the ray P undergoes no refraction. F is the principal focus. the threads of the net can be seen distinctly, the bars of the window will be indistinct, and when the bars of the window are clear and distinct, then the threads are blurred. In the optical apparatus of the eye there is no provision for altering the position of the lenses, but there is one which answers the same purpose, and which is called accommodation. In connection with every camera there is an arrangement of openings or diaphragms by which a greater or lesser amount of light may be admitted, according to circum- stances. In the .eye the iris serves a similar purpose. In many cameras it is necessary to have a number of such diaphragms, each having an opening of a different size, but some are provided \vith a single one, the size of whose opening can be altered ; this is called an " iris diaphragm," and is a rude contrivance com]iared with the natural iris from which it derives its name, and which by means of its muscular fibers can alter in a moment the size of the pupil. Rays of light coming from an object, in order to produce a distinct image of that object, must be brought to a focus upon the retina (Fig. 337). If the media through which the light from an SENSE OF SIGHT. 549 object passes to reach the retina were all of the same density as the air. and were also })lane surfaces, an impression would be produced, but there would be no distinct image. Actually, before such ravs do reach the retina they pass through certain media which, by reason of both density and shape, refract them and bring them to a focus, thus producing a sharp and distinct image of the object looked at. These media are the cornea covered with a laver of tears, aqueous humor, crystalline lens with its anterior and poste- rior capsule, and vitreous humor, seven in all. The amount of refraction is determined by the radius of curvature of the surface through which the rays pass, the refraction being greater as the radius becomes smaller, and by the diiference between the refrac- tive indices of the media, refraction increasing as the difierence increases. The radii of curvature are as follows : When accommodated for Far vision. Near vision. Cornea 8 mm. 8 mm. Anterior surface of lens 10 " 6 " Posterior '• " " 6 " 5.5 " The refractive indices of the various media through which the light passes are as follows : Tears 1.3365 Cornea 1.337 Aqueous humor 1.3365 Vitreous '' 1.3365 Lens (mean for all layers) 1.437 The refractive index of air is 1.000, and of water 1.335. From this talde it will be seen that the tears, cornea, and aqueous humor have practically the same indices of refraction, and we may there- fore regard the media through which light passes to reach the retina as three in number: 1, tears, cornea, and aqueous humor, with a refractive index of 1.33; 2, crystalline lens, with a re- fractive index of 1.43; and 3, vitreous humor, with a refractive index of 1.33. The following table gives the distances between the various points mentioned therein : When accommodated for Far vision. Near vision. Anterior surface of cornea and anterior surface of lens . . 3.6 mm. 3.2 ram. " " " " posterior ." " . . 7.2 " 7.2 " " " lens " '• " " . . 3.6 " Posterior " " " retina " " . . 14.6 " 14.6 " The anteroposterior diameter of an emmetropic eye along the axis is 21.8 mm. 550 THE NERVOUS SYSTEM. The data here given are known as optical constants, and the figures may be regarded as averages, individual eyes differing, as would naturally be expected. Reduced Eye (Fig. 338). — For purposes of calculation, an imaginary eye, the reduced or schematic eye, has been proposed. Fig. 338. — The reduced eye : S, the single spherical refracting surface, 1.8 mm. behind the anterior surface of the cornea; N, the nodal point, 5 mm. behind S ; F, the principal focus (on the retina), 20 mm. behind S. The cornea and lens are put in in dotted lines in the position which they occupy in the normal eye (Stewart). whose refractive medium is a single one, representing, approxi- mately enough for practical purposes, the natural eye. This eye has the following characteristics (Listing) : From anterior surface of cornea to the principal point From nodal point to the posterior surface of lens Posterior principal focus behind cornea .... Anterior principal focus in front of cornea . . Radius of curvature of single refracting surface Index of refraction of single refractive medium 2.3448 mm. 0.4764 " 22.8237 " 12.8326 " 5.1248 " 1.33 " The optical and visual axes may be regarded as identical, and as represented by a line which passes through the centers of cur- vature of the cornea and lens directly backward until it terminates Fig. 339. — Diagram of the formation of a retinal image (after Foster). in the fovea centralis. Rays of light falling upon the cornea are refracted and made convergent, and this effect is increased by the SEySE OF SIGHT. 551 lens and vitreous, so that when the rays reach the retina they are broiio;ht to u focus. Tiiis is shown in Fig, .'539, where the arrow XY is projected upon the retina, forming the inverted image yx. The angle x/(Y is the vifiUdl or optical optical apparatus of the eye was rigid and immovable, it would be necessary, in order to obtain a clear image of an object, either for the individual to approach or to recede from the object, or to cause the object to do the same with reference to him, for only parallel rays, namely, rays coming from objects at a distance of two to three meters or more, are brought to a focus in the normal eye unless some change is brought about in the refractive media. If an object is within that distance, the rays of light coming from it are brought to a focus by altering the shape of the crystalline lens ; this is accom- modation. As already stated, the optical apparatus of the eye is in a state of rest when it is looking at objects more than two to three meters away ; thus to see the stars, although millions of kilometers dis- FiG. 341. — Diagram showing the changes in the lens during accommodation ; the ciliary muscle on the right is supposed to be passive, as in looking at distant objects : the suspensory ligament L is therefore tight, and compresses the anterior surface of the lens A, so as to flatten it. On the left the ciliary muscle M is contracting so as to relax the ligament, which allows the lens to become more convex. This contraction occurs when looking at near objects. tant, no effort is required ; but if it is desired to see objects less than two or three meters away, there is a change in the refractive media until objects are brought to a point so close to the eye that no amount of effort will enable them to be seen. The point at which objects cease to be seen distinctly is called the near-point, and it is, for a normal or emmetropic eye about 12 cm., although it is not the same in all persons. The accommodation of the eye is brought about especially by the change in the shape of the crystalline lens ; thus in looking at SENSE OF SKUIT. 553 near obiects the lens becomes more convex. Tliis is aeconiplishecl in the fullowino- manner: The lens is a very elastic strncture, en- closed in a capsnle to which the snspensory ligament is attached, and the tension of this ligament is snch as to ])nll upon the anterior portion of the capsule and flatten it, at the same time flattening- the anterior surface of the contained lens. This is the condition when the eye is looking at distant objects or is in a state of accommodative rcfst. But when a near object is to be looked at, the radiating fibers of the ciliary muscle contract, and as its fixed jwint is at the junction of the cornea and sclerotic, this contraction draws the ciliary processes forward and relaxes the suspensory liijament, thus removing the influence which tends to flatten the lens, and permits the latter, by its elasticity, to become more convex. The nervous supply for this act is furnished to the ciliary muscle by the motor oculi through the ciliary nerves. At the same time that this muscular action is taking place the pupil becomes smaller and the eves converge. Fig. 342.— Reflected images of a candle-flame as seen in tlie pi'pil of an eye at rest and accommodated for near objects (Williams). This is the usual explanation of accommodation, and may be demonstrated in the following manner : If in a dark room a candle-flame is held at one stde of the eye of a person who is looking as if at a distant object and about 50 cm. distant from the eye, and an observer stands at his other side, he will see reflected from the eye three images of the flame, the brightest and most di.stinct being an erect image, which is formed by the anterior surface of the cornea. Besides this image there is a second image, which is also erect, but which is less" distinct and larger; this image is formed at the anterior surface of the lens. A third image is also seen, which is inverted and also indistinct ; this image is formed by the posterior surface of the lens, which, being concave forward, acts like a concave mirror and inverts the image. These are called Purkhje-Sanson images. If the person then looks as if at a near object, the second image becomes brighter and smaller, and at the same time approaches the first, Avhile the first image under- goes no chancre, and the third a change so slight as not to be per- ceptible (Fig? 342). This proves that in accommodating the eye 554 THE NERVOUS SYSTEM. for near objects the principal change which takes place is an in- crease in the convexity of the anterior surface of the crystalline Fig. 343.— Diagram explaining the change in the position of the image reflected from the anterior surface of the crystalline lens (Williams, after Bonders). lens. There is also a slight increase in the convexity of the posterior surface, while the cornea remains unchanged. In Fig. c Fig. 344.— Phakoscope of Helmhohz: at B B' are two prisms, by which the light of a caudle is concentrated on the eye of the person experimented ■R-ith ; A is the aperture for the eye of the observer. The observer notices three double images reflected from the eye under examination when the eye is fixed upon a distant object ; the position of the images having been noticed, the eye is then made to focus a near'object, such as a reed pushed up : the images from the anterior surfaces of the lens will be observed to move toward each other, in consequence of the lens becom- ing more convex. 343 the course taken by the rays of light is delineated. The eve whose accommodation is under investigation is directed to A, while SENSE OF SIGHT. 555 the candle-flame and the observer's eye are on opposite sides. The images of the candh'-fiauu" will appear alon^r the line IP, on the (hirk hackground ui' the pupil. T\w imago produced l)y reHection from the cornea is seen at the termination of the dotted Hue d ; that from the posterior surface of the lens, at tlie termination of c ; and that from the anterior surface of the lens when the eye is in a state of accommodative rest— «. c, looking at distant objects— at the termination of b; wdien focussed for near objects and the anterior surface of the lens moves forward, the image is seen at the termination of b'—L e., nearer the corneal image ; it is also smaller and brighter. The change in the convexity of the anterior surface of the lens may also be shown by looking at the eye from the side, as in ac- commodation the iris may be seen to move forward, being pushed in that direction by the anterior surface of the lens, \w\i\\ w'hich it is in con- tact. Phahoscope of Helmholtz (Fig. 344).— This apparatus was devised by Helmholtz to demonstrate the changes which have just been de- scribed, and which w^ere ad- vanced by him to explain accommodation. The eye of the person whose accommodation is to be studied is placed at C. For near vision the needle at D is to be looked at, and for distant vision some ob- ject in the same direction. At B and B' there are two prisms, in front of which a candle-flame is placed. The eye of the observer at A sees two sets of the three reflected images, each image being a square spot of light ; those reflected from the ante- rior surface of the lens approach those reflected from the cornea, as already explained, and also approach each other (Fig. 345). Tscherning's Theory of Accommodation. — This authority ex- plains accommodation by supposing that by the contraction of tiie anterior part of both the radiating and circular fibers of the ciliarv muscle the ciliary processes are drawn backward, and that this pulls the zonule of Zinn (suspensory ligament) backward and outward. This increases the tension of the ligament and the Fig. 345. — Puikiiije-Sanson images: A, in the absence of accommodation ; B. during accommodation for a near object. The upper pair of circles enclose the images, as seen when the liglit falls on the eye through a double slit or a pair of prisms ; the lower i)air show the images seen when the slit is single and tri- angular in shape (Stewart). 556 THE NERVOUS SYSTEM. pressure upon the lens, the external or softer portion of which is caused to bulge out, this change being especially marked on its anterior surface. The contraction of the ])osterior portion of the ciliary muscle pulls forward the choroid, and thu.s makes tense, so to speak, the vitreous, })reventing it from yield- ing when the lens is pressed against it by the anterior portion ; thus the pressure of the an- terior portion of the muscle causes the increased convexity of the lens, and not its displacement backward. t^cJioen's Theory of Accommodation (Fig. 346j. — This writer explains the increased convexity of the lens by assuming that the contraction of the ciliary muscle produces the same effect on the lens as is produced upon a rubber ball when held in both hands and com- pressed l)y the fingers. The theories of Tscher- ning and Sehoen presuppose a stretching of the suspensory ligament, while that of Helm- holtz is based on its relaxation. Recent ob- servations of Hess seem to demonstrate that the change in the ligament is one of relaxation rather tiian increased tension, so that at the present time the theory of Helmholtz may be accepted as the true explanation of accommodation. Range of Accommodation. — The point nearest to the eye to Fig. 34G.— To illus- trate Schoen's theory of accommodation. Fig. 347. — Scheiner's experiment. In the upper figure the eye is focussed for a point farther away than the needle : in the lower, for a nearer point. The continuous lines represent rays from the needle, the interrupted lines rays from the point in focus. which objects can be brought and be seen distinctlv is the near- point ; while the point farthest from the eye at which distinct vision exist.s is ihe far-point ; the length of the intervening space is the range of accommodation. SENSE OF siaiiT. 557 \car-poi}if. — Tliis is also called pitnctuin proximtnii, and is ex- pressed by p.j>. It varies in diflerent individuals, l)Ut for a normal adult eye is about 12 era. Objects broug;bt nearer to the eye than this cannot be seen with distinctness, for the refractive media cannot brln<^ the iinati:e of such objects to a focus upon the retina. The near-point for any given eye may be determined by Scheiner's experime)}^ {F\g. 347). In a card two pinholes are made whose distance from each other must not exceed the diameter of the })upil, about 2 mm. Through these holes, with the card held close to the eye, a needle is looked at. It will appear single; if the needle is brought near to the eye, a point will be reached at which it appears double, or it may be blurred ; this is the near-point for the eye in question. Far-pohd. — This is also known as punctum remoturn, or p. r. It is the farthest point at which objects can be seen distinctly by a normal eye, and is inlinitely distant ; so that the range of accom- modation in the normal eye is from about 12 cm. to infinity. As a matter of fact, rays of light which reach the retina from any object not more than two meters distant from the eye are practi- cally parallel, so that in looking at objects at any distance greater than this there is no change in the accommodative apparatus — i. €., the eye is in a state of accommodative rest; while as objects are brought nearer than two meters there is necessitated an increase in the convexity of the lens in order that they may be seen dis- tinctly until the near-point is reached, within which their images become blurred by reason of the fact that the lens has reached the limit to which its convexity can be increased. Convergence of the Eyes during Accommodation. — If, as an object is brought nearer to the eyes of an observer, his eyes are inspected by another, it will be seen that, as the accommodative apparatus is brought into action to focus the image on the retina, the eyes are at the same time turned inward — /. e., made to converge. When it is remembered that in order to produce distinct vision the image must be formed in the fovea centralis; it will be seen that as the object is brought nearer to the eyes each eye must be turned in- ward, otherwise the image would not fall upon the fovea. Contraction of the Pupil during Accommodation. — AVhen a dis- tant object is observed, the pupil is relatively large ; but when the eye is accommodated for near objects, the pupil becomes smaller. By this contraction of the iris the very divergent rays which come from the object, and which, by reason of their extreme divergence, would not be brought to a focus on the retina, are excluded, and thus a sharpness of the image is secured which would not be the case if the pupil was large enough to admit these rays. Defects in the Visual Apparatus. — Emmet ropia (Fig. 348, A). — The emmetropic or normal eye is one in which parallel rays are brought to a focus upon the retina when the eye is in a state of 558 THE NERVOUS SYSTEM. accommodative rest. In such an eye the near-point is about 1 2 cm, distant from the eye, the far-point at infinity, and from about two meters distant to an infinite distance objects can be distinctly seen without any change in the accommodative apparatus. Ametropia. — Whenever the permanent condition of an eye is not as described above, it is one of ametropia. Of this condition there are several varieties. Myopia (Fig. 348, B). — A myopic eye is one that is abnormally elongated, and some au- thorities regard an in- creased convexity of the lens as constituting an essential part of this con- dition. The retina is so far from the lens that parallel rays are focussed in front of it, and, cross- ing, do not form distinct images on the retina, the images being blurred. To correctthis,concave glasses are used, which cause these rays to diverge as they en- ter the eye, and by adjust- ing the concavity to the amount of myopia, par- allel rays are brought to a focus on the retina as they are in the emme- tropic eye without glasses. A myopic eye is commonly said to be a " near-sighted " one. The near-point in myopia may be 5 or 6 cm. from the eye, while the far- point is comparatively near the eye, never at an infinite distance, so that the range of accom- modation is extremely limited. Hypermetropia (Fig. 348, C). — In this condition the eye is shorter than normal, and the retina is too near the lens, so that parallel rays are brought to a focus behind the retina and indis- tinct vision is produced, as in the myopic eye. In the endeavor to overcome this defect the ciliary muscle is liable to overstrain in order to converge the rays to a focus upon the retina, and the constant effort is painful and injurious. The condition is corrected by the use of convex glasses. The near-point in the hypermetropic eye is farther than in the normal eye. The far-point does not Fig. 348. — Diagram showing the difference between (.4) emmetropic, (B) myopic, and ((7) hypermetropic eyes. SLWSE OF SIGHT. 559 exi.-=t. for objects witiild of necessity liave to he removed to a greater distance than infinity, which is, of" course, itnpos.-ihle, in order that the rays coming from them might he converging, and tluis these rays be brought to a focus upon tlie retina wlien the eye was in a state of accommodative rest. Presbyopia, which is sometimes called " old sight," sometimes "long sight," is the condition of the eye present in elderlv people. In this condition it is ditlicult to see near objects, although the vision for those at a distance is unaffected. It is usually attrib- uted to a lessened elasticity of the lens, though the ciliary muscle is also less strong; some writers state that it depends on dimi- nution of the convexity of the cornea. To aid in correcting it convex glasses are used. Presbyopia may begin as early in life as the fifteenth year, although it commonly does not until about the fortieth year. The ability to see objects nearer by in advanced age, when pre- viously spectacles were required, is explained by an increased refractive power which sometimes occurs under such conditions. Fig. 349. — Lines for the detection of astigmatism. Astigmatism (Fig. 349 \. — In this condition the cornea is usually at fault, its curvature being greater in one meridian than in another, and consequently the rays of light from an object are not all brought to the same focus, and the image, therefore, is not distinct. Astigmatism is regular when the curvature in any given meridian is regular in that meridian, although the meridian may differ in respect to curvature when compared with the one at right angles to it : the cornea is ellipsoidal and not spherical. Astigmatism is irregular when in any given meridian or meridians the curva- ture of the cornea is not an arc of a circle or an ellipse. It is irregular astigmatism which causes the stars to look as though ravs projected from them. For the correction of regular astigma- tism glasses are worn which are segments of a cylinder — that is, curved in but one direction — and are known as '' cylindrical " glasses. Irregular astigmatism cannot be corrected by any glasses. The crvstalline lens mav also be at fault in astigmatism. 560 THE NERVOUS SYSTEM. Regular astigmatism is detected by the observation of con- centric rings or radiating lines, as in Fig. 349. In the former some portions will be blacker and more distinct than others, while in the latter the lines will present the same differences. Spherical Aberration (Fig. 350). — When rays of light are refracted, those which are incident near the edge of the lens are refracted more than those near the principal axis, and will, therefore, come to a focus in front of them, and produce an indistinctness of the image. This indefiniteness of focus is spherical aberration. To reduce this, a diaphragm is used in optical instruments, by which these marginal rays are excluded, or, as in large telescopic lenses, the same result is accomplished by diminishing the curvature of the lens at its margin. This Fig. 350. — Diagram showing the effect of a diaphragm in reduciBg the amount of spherical aberration. defect exists in the eye, and is lessened by the iris, which serves as a diaphragm to cut off the marginal rays, and also by the diminished refractive power of the marginal portions of the lens as compared with its center. Spherical aberration is more marked with divergent than with parallel rays, and as rays are more divergent the nearer the object from which they come is to the eye, this is corrected by the greater contraction of the iris — /. c, the greater diminution of the pupil — which results in cutting off more of the marginal incident rays. In the human eye spherical aberration is not an important defect. Chromatic Aberration. — White light being a mixture of rays of different colors, and these differing in refrangibility, the red being the least and the violet the most refrangible, when white SENSE OF SIGHT. 561 liirht passt's through a Ions it is hrokcn up into its ('((niponcnt ravs — /, I'., uiulorgot'S (li.sixrsion — and the most n't"rang;ihle or violet rays will be brought to a tbeus nearer the lens (Fig. ool j than the least refrangible or red rays, and between will be the various intermediate eolors. When these rays fall upon a screen there will be produced a si-ries of circles of the different colors. In Fig. 351 it will be seen that if the screen was ])lace(l at x, the outer color would be red, and the inner violet; while if it was Fig. 351. — Chromatic aberra- tion (Carhart and Chute). Fig. 352. — Achromatic combination of lenses (Carhart and Chute). placed at y, the colors would be reversed. This defect in lenses is chromatic aberration, and is overcome by combining a biconvex lens of crown glass with a planoconcave lens of flint glass (Fig. 352). Inasmuch as images formed by rays which have passed through such a combination are not fringed with color, the combination is achromatic. It is a rather curious fact that the eye was at one time sup- posed to be free from this defect, and its absence Avas explained by the fact that the different media through which light passes to reach the retina differ so in their refracting power as to over- come dispersion ; and it is said that it was this which led to the combination just described of the crown and flint glass to make the achromatic lens. The media of the eye, however, do not form an achromatic combination, but the violet rays are actually Fig. 3.53. — To show dispersion in the eye, view the figure from a distance too small for accommodation. Approach the eye toward it : the white rings appear bluish, owing to circles of dispersion falling on them. A little closer, and the black rings become white or yellowish-white, being covered by circles of dispersion and diffusion. brought to a focus about 0.5 mm. in front of the red. Under ordinary circumstances this produces no confusion ; and yet that this defect is inherent in the human eye may be readily demon- strated. If Fig. 353 is looked at very clo.se to the eye — so close that the two crystalline lenses cannot accommodate for it — the white rings become bluish on account of circles of dispersion fall- ing on them, and if a little closer, the black rings become of a yellow- ish white color. This dispersion also explains irradiation. 36 562 THE NERVOUS SYSTEM. Tlie Iris. — The iris possesses two sets of muscular fibers, the circular and the radiating. Some authorities question the existence of the radiating muscular fibers, regarding them as elastic rather than contractile, and explain dilatation of the pupil by supposing that the circular fibers cease to contract, and that ijy tlie elasticity of the radiating fibers the pupillary margin of the iris is drawn outward. It seems to us, however, that the existence of contrac- tile radiating fibers has been sufficiently demon- strated. By the enlarge- ment or diminution of the size of the pupil the amount of light which is permitted to pass into the eye is regulated. The pigment in the iris makes it opaque, and thus only such light as enters the pupil can reach the retina. \Ye have seen that it is the iris which, excluding the marginal rays, mini- mizes spherical aberra- tion ; and that contrac- tion of the pupil takes place during accommo- dation. The three func- tions of the iris may, therefore, be regarded as (1 ) to regulate the amount of light which falls upon the retina ; (2) to minimize Ckjurse of constrictor nerve-fibers spherical aberration ; and Course of dilator nerve-fibers — -Vophfh Fig. 354. — Diagrammatic representation of the nerves governing the pupil : //, optic nerve ; Z.g, ciliary ganglion ; r.6, its short root from III, motor oculi nerve; sym, its sympathetic root; r.l, its long root from I'', ophthalmonasal branch of ophthalmic division of fifth nerve ; a.c. short ciliary nerves ; I.e., long ciliary nerves (Foster). (3) to assist the accom- modative apparatus in the production of distinct vi- sion for near objects. In the changes which take place in the iris, two sets of nerves are involved (Fig. 354) : (1) Tho.se of the third nerve or oculomotorius ; and (2) those of svmpathetic origin. The third nerve supplies the circular fibers, and consequently section of this nerve paralyzes these fibers, and dilatation of the pupil occurs. When the third nerve is .stimu- lated, the circular fibers contract, causing a diminution in the size of the pupil. The sympathetic supplies the radiating fibers, and SENSE OF SIGHT. 5(33 its section paralyzes these fibers, causing contraction of tiie pupil, whik' its stiuujlation produces dilatation. Mi/(j5 inav be seen. If the eye is quickly closed and again opened, this outline may be again seen, and this may be repeated several times. 3. A third method of demonstrating the retinal vessels is by con- centrating a strong light on the sclerotic, at a part as distant as possible from the cornea, by means of a lens, as is shown in Fig. 355. 4. If a card is perforated with a pin, and then held close to the cornea, and through the pinhole light from a lamp or other source of illumination is allowed to fall on the retina, when the card is moved rapidly up and down or from side to side, but not so much as to prevent the light from entering the pupil, Fir,. 356.— Figure to illustrate the principle of the ophthalmoscope. Rays of light from a point, P, are reflected by a glass plate, M (several plates together in Helinholtz's original form), into the observed eye E' . Their focus would fall, as shown in the figure, at P', a little behind the retina of E' . The portion of the retina A B is therefore illuminat<>d by diffusion circles; and the rays from a point of it, F will, if FJ is emmetropic and unaccommodated, issue parallel from E' and be brought to a focus at F' on the retina of the (emmetropic and unaccommodated) observing eye E. a shadow of the blood-vessels of the retina will be seen. These shadows of the retinal blood-vessels are Purkinje' s figures. The retinal blood-vessels do not extend beyond the inner nuclear layer, and the fact that these vessels cast a shadow when light is admitted to the eye, as in the experiments just referred to, demonstrates that the sensitive portion of the retina lies behind the blood-vessels, and the distance behind can be calculated by measuring the amount of change of position the shadows undergo when the light is moved about. This has been done, and the distance has been ascertained to be about 0.2 mm. to 0.3 mm, behind the vessels, which corresponds to the layer of rods and cones. 566 THE NERVOUS SYSTEM. Circulation of Blood in the Bctiua. — Not only is it possible to see the shadow of the retinal blood-vessels, but the movement of _— ^- — '^ Fig. 357.— Diagram of the direct method with the formation of an upright image. Rays from the source of light L are received upon the concave mirror M, and con- verged upon the observed eye Obd., within which they cross and illuminate an area of its fundus. From an area A B thus lighted, rays pass out of the pupil (parallel if it be emmetropic, as here represented) through the sight-hole of the mirror, and, entering the observer's eye. Obr., are focussed upon the retina. An image is there formed as though the object seen was at a great distance, and the perceptive centers project it into space as though the object was at some arbitrary distance (e. g., 25 cm.). By the laws of magnification by a simple lens the image is embraced between the lines passing from the optical center of the magnify ing-lens (the refracting system of the observed eye), through the extremities of the object, and has the size A' B' , A" B", etc., according to the distance of projection (Randall). the corpuscles within these vessels can also be seen if the eye is directed toward the sky. They appear as bright little bodies, 06r Fig. .358. — Diagram of the indirect method, giving an inverted image : rays from the source of light L. converged toward the observed eye Obd by the concave mirror M, are intercepted by the lens Obj, and after coming to a focus diverge again and light up the fundus. From a part of the illuminated fundus A B rays pass out of the pupil to be again intercepted by the lens 0. and form an inverted real image at its anterior focus A' B'. This real image is viewed by the observer's eye behind the sight-hole of the mirror with tlie aid of a magnifyiug-lens Oc, and is seen enlarged, as at A" B" (Randall). movins: rapidly and uniformly throucrh the field. If cobalt glass is held in front of the eyes, the corpuscles are more readily dis- SENSE OF SIGHT. 5G7 cernible. The velocity of the flow of IjIooJ in the capillaries of the retina is from O.o mm. to U.9 mm. per second. Intra-ocnlar Imajts. — In addition to the blood-vessels and blood-corpuscles, other objects within the eye may throw shadows upon the retina; indeed, any opacity in the media of the eye through which the rays of light pass would do this, as, for in- stance, the muscce volhanfes. These are little bodies floating in the vitreous, which are supposed to be the remains of cells or tibers which exist during fetal life, and which have not become converted into the vitreous humor, as have most of the cells and fibers. Thcv assume various shapes in diiferent individuals, but the shape is' invariable in the same person. They may appear as a string of beads, or in the form of streaks or granules. The OpJithalmoscope. — This is an instrument l)y means of which (me person can examine the eye of another and obtain a view of the retina. Inasmuch as sora'e of the rays of light which enter the eve and fall upon the retina are reflected from the surface and are brought to a focus again at the source of illumination, it is mani- fest that%vithout some special device it would be impossible to see the image which these reflected rays make, for to have the eye of the observer in the path of these reflected rays would cut off the light which caused them. To overcome this obstacle, Helmholtz devised the ophthalmoscope, which consisted of several plates of glass, one upon another (Fig. 356), that reflected the light from their source into the eve, and the reflected rays, traversmg the glass plates, formed an image on the retina of the observer. At the present time glass plates are not used, but in their place a cncave mirror, with an opening in it, through which the observer can look. There are two methods of using the ophthalmoscope : the direct (Fig. 357) and the indirect (Fig. 358). These Avill be readilv understood after an examination of the illustrations and their respective lesrends. It is customarv, though not absolutely necessary, before making an ophthalmoscopic examination to drop into the eye a solution of atropin of a strength of two grains to the ounce. This paralyzes the accommodation "and dilates the pupil. The exammation is conducted in a dark room. The illuminated retina produces a red glare, the refiex, which, as the observed turns his eve slightly inward, becomes lighter in color, because of the white surface, the optic disc, from which the liffht is reflected when the eye is in this position ; in its center is the'ponis opticus, with the arteria centralis retinae, and radiating from this are its branches ; veins also are seen. The macula lutea and the fovea centralis mav likewise be discerned. The ophthalmoscope is used to detect changes in the retina, as in Bright's disease of the kidneys, and also for testing errors of refraction, as in myopia and hypermetropia. For this latter 568 THE NERVOUS SYSTEM. purpose .skiascopy also is employed, which is defined as " a method of determining the refraction of the eye by examining the move- ments of light and shadow across the pupil when the retina is illuminated bv light thrown into the eye from a moving mirror." Light. — The word "light" is used in two senses: 1. With reference to the sensation produced in the brain ; and 2. With reference to the cause of that sensation. Light, the cause, is defined as " the form of radiant energy that acts on the retina of the eye, and renders visible the objects from which it comes ; the illumination or radiance that is apprehended bv the sense of vision" (Standard Dictionary). It is " a periodic disturbance in a very subtle and highly elastic medium which is supposed to exist everywhere in space, even pervading the inter- molecular spaces in matter. This medium is known as the ether, and vil)rating disturbances in it give rise to all the phenomena of radiant energy. These disturbances are propagated through it as waves, not of compression and rarefaction, but more like those of the rope, the direction of vibration being transverse to that of propagation " (Carhart and Chute). The reference to " the rope " is to an experiment of laying a soft-cotton rope, about 5 feet long, on a floor, and then, holding one end of the rope in the hand, setting up vibrations in it bv a quick up-and-down movement of the hand. When these waves in the ether reach the retina they produce the sensation of sight, and, as has been stated, the portion of the retina which is sensitive to light is the layer of rods and cones. Just how this is accomplished is not known. Various theories have been advanced to explain it : (1) That the waves of light be- come waves of heat antl thus act as thermic stimuli to the rods and cones ; (2) that the waves of light become waves of electricity, and that the stimuli are electric; and (3) that these waves produce certain chemical changes, so that the stimuli are chemical. The first antl second theories may be passed by with a mere men- tion, and. although the third is far from proved, yet there are facts which make the theory worthy of attention and continued investi- gation, as a result of which the true explanation may be forth- coming. In the outer portions of the rods of the retina is a pigment, rhodopsin or visual purple, which, when the retina is exposed to light, becomes red, then orange, then yellow, and finally fades awav. When the eye is exposed to light, the pigmented epithe- lium of the retina sends pigmented processes between the rods and cones, and this pigment, fuscin, forms visual j)urple again, and this reappears in the rods. If the pigmentary layer is sepa- rated from the other layers of the retina, the formation of the rhodopsin, after it has been bleached by light, does not occur. If an eye, after having been protected from the light for a con- siderable time, is then exposed so as to receive the image of SENSK OF SIGHT. 569 a window upon the retina for a time varying from several seconds to several minutes, according to tlie intensity of the ligl»t, and the retina is then removed and inspected in a red light, the image of the window will be seen in it. Such an image is an optogram, and is due to the action of the light on the visual purple, bleaching it in some places, and but little aftecting it in ()thers. This image may be preserved, or, as piiotographers say, " fixed," bv putting the retina in a 4 per cent, solution of ahuu. While it might at first seem as if these changes in the rhodopsin explained what actually took place in the eye when the waves of the luminiferous ether reached the retina and produced the sensa- FiG. 359.— Model to illustrate astigmatisDi. tion of light, still the absence of this coloring-matter from the cones, which exist without the rods in the fovea centralis, where sis:ht is most acute, would alone be sufficient proof that the visual purple is not essential to vision. Some animals possessing sight have no visual purple even in the rods. Engelmann has described a shortening and a thickening of the cones of frogs and fishes under the stimulation of light, and a lengthening in the absence of light, but as to the connection be- tween these changes in the cones and sight, nothing is known. The eye is able not only to see objects, but to take cognizance of certain facts in connection with them, such as their form, size, distance, and color. 570 THE NERVOUS SYSTEM. Form. — Plane surfaces can be seen witl; either eye alone, but solid bodies require the combined use of both eyes, or bhiocular vision, in order that their solidity may be appreciated. If a solid object is looked at with the left eye, while the right eye is closed, and then with the right eye while the left is closed, it will be ob- served that with the left eye more of the left side of the object is seen than with the right eye, and with the right eye more of the right side of the object than with the left eye. The two images produce the effect in the brain of a single solid body. This principle is made use of in the stereoscope (Fig. .360). The picture which is seen with this instrument is double, each having been taken with a separate lens, so that when their images are thrown on the retina the effect is as if both eyes were looking at the scene represented in the pho- tographs. Identical Points. — It would seem a priori that each rctinal image would produce its own ef- fect upon the brain, and that, in- stead of seeing a single object, it would appear double. The theory of identical or corresponding points has been advanced to explain what actually takes place. If one retina is in imagination placed upon the other, the foveje centrales super- imposed the one upon the other, all the other [)oints of the retinae similarly superimposed are iden- tical or corresponding points, and images formed upon such points will in the brain produce the ef- fect of single vision. When the images of an object are not formed upon identical points, double vision or diplopia results. If, therefore, while looking at an object we press with the finger upon the outer side of one eye so as to turn it a little inward, we see the object double. Size. — The size of objects is determined by two factors : The size of the visual angle which they subtend, and their distance from the observer. Helmholtz has demonstrated that an object which subtends a visual angle of less than 50" cannot be seen by the unaided emmetropic eye. This corresponds to an image on the retina of 3.65 //. The diameter of each cone in the macula lutea is about 3 /i. Kolliker gives it as 4 fj. to .5 ii. In other words, if an object does not make an image on the retina large Fig. 360. — Brewster's stereoscope: p and n are prisms, with their refract- ing angles turned toward each other. The prisms refract the rays coming from the points c, t of the pictures a b and a (3, so that they appear to come from a single point, q. Similarly the points a and a appear to be situated at /, and the points h and p at <<). SENSE OF SIGHT. 571 enough to stimulate a cone, it does not come within the range of vision. Distance. — It is inip()ssil)le to judge of the distance of <)l)jects except by experience ; thus a child reaches for everything it sees, irrespective of the distance from it the objects may be ; and persons who, having been blind from birth, are in maturer years endowed with sight — by operation, for instance — bear testimony that every- thing seems to be immediately in front of them. If, however, the size of an object is known, then the size of its image on the retina determines our estimate of its distance. Conversely, if we know the distance of an object, then the image which that object produces on the retina is the determining factor in our judgment of its actual size. If, therefore, our judgment of the distance of an object from us is erroneous, so will be our judgment of its size, and vice versa. If, for instance, a ship is seen through a fog, we suppose that, being indistinctly seen, it is at a considerable dis- FlG. 361. — Formation of solar spectrum. tance from us, although, as a matter of fact, it may be quite near, and making an image of considerable size upon the retina, we judge the ship to be larger than it actually is. It is a well-known fact that the moon seems larger to an observer when near the horizon than when near the zenith, although, as a matter of fact, it is nearer by about 4000 miles, half the diameter of the earth, when in the zenith, and should therefore a priori seem larger, but when it is near the horizon we have terrestrial objects to compare it with, while when in the zenith there is nothing with which to compare it. Color. — When a beam of sunlight passes through a prism it is separated by dispersion into its component colors, forming a solar spectrum (Fig. 361), the red rays being tlie least refracted, and the violet rays the most. The color depends upon the rapidity of vibration or the length of the waves ; thus the red waves are the longest and the vibrations the least rapid, while the violet are the shortest and the vibrations the most rapid. In the following 572 THE NERVOUS SYSTEM. table are given the wave-lengths for the center of each color in ten-millionths of a millimeter. Eed 7000 Blue Orange 5972 Yellow 5808 Green 5271 4960 Indigo 4383 Violet 4059 There are rays, calorific rays, beyond the red rays whose wave- lengths are longer than the red, and others beyond the violet whose wave-lengths are shorter than those of the violet ; these latter are the actinic rays ; neither the calorific nor the actinic rays are visi- ble. If, after the dispersion, a second prism in reversed position (Fig. 362) is placed in the path of the colored rays, these will be Fig. 362. — Reunion of colored rays to form white light. reunited, and will emerge from the second prism as white light. This synthesis of light, or the composition of white light by the union of all the colors of the spectrum, may he brought about by the union of certain colors without using all of them ; thus red and bluish green will produce white light, as will also orange and light blue. Colors which when mixed produce white light are complementary. In the color diagram (Fig. 363) this relation is Fig. 363.- JP -Color diagram. made evident, the form of a triangle being selected around which to arrange the colors, rather than a cin^le, for the reason that they do not act equally as stimuli. Red, green, and violet are placed at the angles on the Young-Helmholtz theory of these being the primary colors — i. e., the theory that tlie other colors are mixtures of these three colors. A reference to this diagram shows that red, green, and violet, represented by R, G, and v, make white, repre- SENSE OF SIGHT. 073 sented by w. The colors at the extremities of straight lines are complementary colors ; orange and Idue, o and n, make white, w. But neither n nor o is at the extremities of tlie line from n, but, if this line was continued, it would strike the curved line i)etween 15 and G — i. e., red and bluish green are complementary colors. One can see also from this diagram what color results from the union of two others. Thus red and yellow will produce the inter- mediate color, orange ; red and violet will produce purple, and this and green will produce white. If complementary colors are put beside each other, both colors are more pronounced ; on the other hand, if colors which are not complementary are so placed, the colors are subdued. It may be well here to refer to some of the fundamental facts in connection with colors, and for this purpose we shall quote statements and experiments from Elements of Phi/sics, by Carhart and Chute. Color is not a property inherent in objects — i. e., bodies have no color of their own. Thus in the case of opaque bodies, the color which they appear to have depends upon the kind of light which they reflect. A red body is red because it absorbs the other colors of the spectrum than the red and reflects this color from its surface. If all the colors are reflected in proper proportion, the body appears white. This can he proved by looking through a glass prism at a piece of white paper 3 cm. long and 2 mm. wide, pasted on a piece of black cardboard several times larger, the edges of the prism being held parallel to the length of the strip. The image seen through the prism will be a spectrum similar to the solar spectrum. If a piece of red paper is substituted for the white paper, on looking through the prism the red end of the spectrum will be seen, but the other colors will be dim or absent. If a blue strip is looked at, the spectral image will show the blue, the other colors being lacking. In other words, white paper is white because it reflects all the colors in due proportion, while red paper reflects only red, and blue, only blue. If in the red of the solar spectrum a piece of red paper or ribbon is held, it will appear brilliantly red ; else- where it will be nearly black ; a piece of blue will appear blue in the blue of the spectrum, and there only. The color of opaque bodies varies as the light which falls upon them varies ; thus if any fabric into which blue or violet enters, as purple and pink, is examined by artificial lights, all of which are deficient in blue and violet rays, its color will vary from that which it has in sun- light. It is on this account that matching colors by artificial light is so difficult. Transparent bodies, on the other hand, are colorless when they absorb no light — i. e.. transmit it all ; or when they absorb all the colors in like proportion. It is the color or colors which are trans- mitted that give the color to transparent bodies. If one color is 674 THE XERVOUS SYSTEM. absorbed, the color of the object will be the sum of the colors that are transmitted. We are now prepared to discuss some of the facts which have been established in connection with the sensation of color. The union of the spectral colors to produce white light may be demon- strated by cutting out disks of colored paper (Fig. 364) and attaching them to a whirling machine (Fig. 365), or complemen- tary colors may be combined in the same way with the same result ; or, again, by using different colors various combinations mav be made. This mav be called a physiologic mixture of colors, and is thus explained : When the retina is exposed to a color, this produces a certain effect which remains even after the color which produced it has been removed ; if, before the sensation caused by this color has disappeared, the retina is exposed to another color, the second color is superimposed upon the first, and if the two are complementary, the effect is that of white light, as when these Fig. 364. — Disks of colored paper. Fig. 365. — Whirling machine. colors are combined by a prism. If the revolving disks contain all the .spectral colors in due proportion, and are revolved rapidly enough, so that all the colors produce their effect on the retina before the sensation produced by any one has faded away, the effect of white light is produced, as when these colors are united by a prism. Mixing of Pigments. — The effects just described as being pro- duced by the physiologic mixture of colors cannot be produced by the mechanical mixture of pigments. Although blue and yellow when mixed upon the retina produce white, yet when blue and yellow pigments are mechanically mixed the resulting color is green and not white. If a broad line is drawn on a blackboard with a yellow crayon, and over this is drawn another line with a blue crayon, the resulting color will be green. This effect is ex- plained in the following manner : The yellow crayon reflects not only yellow light, but also green light, and absorbs all the other colors. The blue crayon reflects not only blue, but also green, and SENSE OF SICIIT. 575 absorbs all the others. So that when the two are mixed, the only color which is not absorbed by the crayon is green, and therefore the line appears green. Nor can tlie colors whicii are transmitted through transparent bodies be nnited to produce white light, or the combination which the mixture of" colored lights produces on the retina, any more than can the pigments mentioned above, and the reason for this is obvious. If, for instance, sunlight is transmitted through red glass, all the rays which produce other colors than red are absorbed, and the red onlv being transmitted, gives the red color to the glass. If the same is done with green glass, only the green rays will be transmitted, all the other rays being absorbed. If now white light is transmitted through red glass, only the red will remain, and if this is transmitted through green glass, no light will come through, for green glass will not transmit the red rays, and the green ravs have alreaily been absorbed by the red glass. To pro- duce white light or the various combinations of the spectral colors, the rays must fall upon the retina and the colors be mixed phy- siologically, the mixture producing effects which are interpreted by the brain. Young -Hehnfwltz Theory of Color. — Inasmuch as this theory was advanced by both Young and Helmholtz, it bears the name of both. It is based on the view that there are in the retina three substances which are stimulated by the three primary colors, re- spectively, of red, green, and violet, and that when all three fall upon the retina in proper proportion tiie sensation of white is produced ; and when any two of the three stimulate the retina, the effect is to produce some intermediate color, as, for instance, violet and green produce blue ; red and green, yellow and orange ; red and violet, purple. That such substances actually exist, there is no proof; the term "substance" is used for want of a better one. The term "fiber" is used by Helmholtz, and "red fibers," " green fibers," and " violet fibers " are spoken of. This theory supposes, also, that each of the primary colors stimulates to some extent all the three substances, but one is stimulated so much more than the others that the effect upon the others is not noticed. Especially marked is this differentiation of the red, green, and violet near the fovea centralis, and when the light is not too intense. If the light falls upon the ])ortions of the retina near the ora serrata, or if that wiiich falls on the retina in the neighborhood of the fovea is of very little or of very great inten- sity, all the rays seem to stimulate the three substances alike, for, under such circumstances, the colors of objects are not readily made out. The theory has been advanced that the power to dis- tinguish colors resides in the cones, and that the stimulation of the rods by light gives the sensation of luminosity without color. Von Kries states that the rods are color-blind, their stimulation re- 576 THE NERVOUS SYSTEM. salting iu the sensation of luminosity only ; that they are more easily stimulated than the cones, and are particularly responsive to waves of short wave-lengths ; and tliat they adapt themselves to light of varying intensity. Hering Theory of Color. — This theory supposes the existence of three substances in the retina, and of six primary color sensa- tions, arranged in pairs, white and black forming one pair, red and green another, and yellow and blue the third. These corre- spond, it will be noticed, to complementary color sensations. The three substances are the white-black, the red-green, and tlie yellow- blue. These substances are supposed to be susceptible of being affected in two opposite ways : In one a constructive or anabolic change is produced, and in the other a disintegrative or katabolic change. If, for example, all the spectral colors fall upon the white-black substance, katabolic changes occur in this substance producing the sensation of luminosity ; while if no light enters the eve, anabolic changes occur, with the effect of producing blackness. The red rays falling upon the retina produce katabolic changes in the red-green substance, producing the sensation of red, while the green produces anabolic changes, and the resulting sensation is that of green. Blue ravs cause anabolic changes in the yellow- blue substance, and yellow rays cause katabolic changes in the same substance. These changes in the retinal substances produce the sensations of color when transmitted through the fibers of the optic nerve to the brain. Franklin Theory of Color -sensation. — This theory supposes that the eve, in the early periods of development, possesses only the white-black or grav visual substance, and is therefore sensitive to luminositv onlv, and not to color. Later this substance becomes modified "into the blue and yellow substance, and then into the red and green. For a further account of this theory the reader is referred to the American Text-hook of Physiology, vol. ii., p. 337. Birch Modification of the Young- Helniholtz Theory. — This ex- perimenter has exposed the eye to sunlight in the focus of a burn- ing-glass behind transparent screens of different colors, with the result of producing a temporary color-blindness. If a red screen is used, the eye is red-blind — i. e., cannot distinguish the color, so that if scarlet is looked at, it appears black, while yellow appears green and purple appears violet. If a violet-colored screen is used, violet appears black ; purple appears crimson ; and green, a bright green. These effects are due to fatigue of the retina, so that the color to which the retina is exposed for a time ceases to stimulate, and that color ceases to be recognized while the other colors con- tinue to stimulate. Birch found that after exposure to yellow the eve was blind not only to yellow, but to red and green also, which primarv colors in the Young-Helmholtz theory produce yellow. He concludes that there are not only the three primary SENSE OF SIC I IT. r,77 colors red, green, and violet, but that blue must also be included as a jiriinarv color. Color-blindness or Daltonism. — It is estimated that 4 per cent, of all males and 0.4 per cent, of all females are color-blind — i. e., unable to recognize all colors; and this defect is congenital — i.e., its possessor is born with it. It is said that it may be inherited also. Most of those who are color-blind are unable to distinguish between red and green, while some cannot tell green fnjui blue, and others confound various colors. 'I'lic name Dtiltonisin, given to color-blindness, is derived from the name of the great chemist, Dalton, who when twenty-six years of age discovered that he was color-blind. By some writers the term "Daltonism" is used as a svnonvm for color-blindness in general, while others restrict its use to red-l)liudness. Dalton himself, in matching silk, would match red, pink, orange and brown with different shades of green ; blue he would match with pink and violet, and lilac with gray. It was not Dalton, however, but a shoemaker, Harris by name, who discovered color-blindness, he himself being red-blind. As already stated, most color-blind persons are either red- blind or green-i)lind. If a red-blind per.son looks at the spectral colors, those from the red to the green look green, while the extreme red end of the spectrum is invisible. The violet appears blue, and at the end of the green near the blue of the spectrum there appears to be a band of white or gray. To a green-blind person the spectral colors from red to yellow appear to be all yellow, but of different intensity : the green appears as a pale yellow, having in its middle a gray or a white band, while the violet appears blue. A report on color-blindness, made by the Royal Society, states that "to the green-blind, red and yellow are the same color ; but the yellow being the brighter, he looks on red as degraded or darkened yellow. On the other hand, to the red-blind, green is brighter than yellow or orange, and these appear as degraded green." The explanation of color-blindness varies according to the theory of color-vision which is accepted. According to the Young-Helmholtz theory, a red-blind person is deficient in the red, and a orreen-blind person in the green, visual substance of the retina, or else, if these substances are present, all the rays, irrespective of their wave-lengths, stimulate them. In accordance with the Hering theory, those who are red-blind or green-blind lack the red-green visual substance and possess yellow-blue. On this theorv there is no difference between red-blindness and green- blindness, but, as a matter of fact, this is not the case. If the Franklin theory is accepted, then the explanation in the case of the red- and green-blind wouM be that the white-black, or gray, visual substance had developed into the yellow-blue, but had been arrested in its development before the stage of red-green had .'57 578 THE NERVOUS SYSTEM. been reached. It may be said in conclusion that objections may be advanced to all the theories, and that no one accounts for all the observed facts. Holmgren Test. — Inasmuch as color-blindness is so common a defect, and inasmuch as it may be a most serious one when the individual who suffers from it is engaged in a pursuit in which the lives of human beings may be jeopardized by his inability to distinguish colors, as a railway engineer or a pilot on a vessel, tests have been devised to determine its presence or absence. The one most commonly used is that of Holmgren, and consists in submitting to the one to be examined a lot of skeins of worsted of various colors, from which he is to select those which will match standard skeins of green and pink. Fatigue of Retina. — When the retina has been exposed for some time to any color, it ceases to be sensitive to that color. It was this fact which led Helmholtz to the adoption of the theory of color-sensation which bears his name. He found that if the retina was exposed to a red light, it became fatigued for that color, and a yellow light appeared green ; if exposed to a green light, and after it was fatigued for that color it was exposed to blue, the blue w^ould appear violet. It was such experiments as these that led him to the opinion that there were three visual substances in the retina, and that there were three primary colors — red, green, and violet. In a similar manner, if the retina is exposed to white, it becomes fatigued. Thus, if the eye is directed for a time to a piece of black paper placed on white paper, and then the black pa])er is removed, so that the eye sees only the white, the spot which was covered by tlie black will be more intensely white than the rest — for the reason that the portion of the retina upon which the light from tlie white paper falls w'hen the other portion is covered by the black becomes fatigued, while the portion on which the rays from the black fall is not fatigued, and by con- trast the white here appears whiter than does that of the other part of the paper. After-images. — The white spot which is seen in the above experiment is a negative after-image — i. e., it is the opposite of the color which causes the fatigue, white being the opposite of black. It would perhaps be more correct to say that it is complementary to the color which produces it, as in this case, black and white being complementary. Negative after-images are also produced when other colors are used. Thus, if a blue paper is imposed on white and the eye directed to it, and the blue then removed, the spot which had been covered by it appears yellow, blue and yellow being complementary colors. A negative after-image is always complementary in color to that which causes the retinal fatigue that produced it. SENSE OF SIGHT. 579 If the eye is directed to a briglitly illuminated object, as the sun, but not lonc^ enough to produce fatigue, and then closed, a bright spot of light is seen : this is a [xmiirc after-image. It remains bright for but a short time and then changes color, becomino: irreenish blue or bluish green, blue, violet, purple, and red, and then fading away entirely. It may be followed by a negative after- image. Visual Judgment. — We have al- ready referred to some visual judg- ments — as to form, size, distance, etc. (p. 571). It is a common say- ing that " seeing is believing," and yet not one of the senses is more liable to deceive its possessor than that of sight. For instance, if the vertical and horizontal lines in Fig. 3()() are compared, the vertical will immediately be pronounced the longer, and yet when accurately measured it will be found that each is exactly 4 cm. in length. This tendency to overestimate vertical lines is attributed to the relative weakness of the superior rectus muscle as compared with the muscles that move the eyeball horizontally. The difference is said to be from 30 to 50 per cent, in height and 40 to 53 per Fig. 366. — To illustrate the overesti- mation of vertical Hues. D E Fig. 367. — To illustrate the illusion of subdivided space. cent, in area of cross-section ; owing to this weakness a greater effort is required to turn the eyeball upward, and the effect upon the mind is that of turning it through a greater distance ; hence vertical lines seem to be longer than they really are. 580 THE NERVOUS SYSTEM. In Fig. 367 the space between a and b seems to be greater than that between b and c, and yet they are exactly the same. Any space like that between a and b which is subdivided seems larger than that which is undivided, as that })etween b and c. In Fig. 367 d appears to be liigher than it is broad, and e broader than it is liigh. So, too, Zollner's lines (Fig. 368) are very illusory. The hori- zontal lines appear to be far from parallel, and yet if they are looked at from their ends, by turning the page sidewise, their Fig. 368.— Zollner's lines. parallelism is at once apparent. This is explained by the fact that acute angles are apt to be overestimated and obtuse angles underestimated. In Fig. 369 the straight line A appears shorter than the straight line b, though it is of exactly the same length. Similar illusions might l)c multiplied almost indefinitely, and yet with all its imperfections the human eye is a wonderful organ. Some one has said that it is so defective from an o]>tical standpoint that, had he ordered such a piece of apjiaratus from an optician Fig. 369. — Illusion of space-perception (Bowditch). and it had been delivered with as many defects, he would have returned it and refused to pay for it. It has also been said, in speaking of the crystalline lens, that an optician could make a better lens than Nature has furnished ; but it has also been said that he could not make so good an eye. And finally. Dr. Bow- ditch, in his excellent discussion of "Vision," in the American Text-hook of Physioloc/y, well says : " When we reflect upon the difficulty of the problem which Nature has solved, of constructing an optical instrument out of living and growing animal tissue, we cannot fail to be struck by the perfection of the dioptric apparatus SENSi: OF SKI I IT. 581 of the eve as well as by its adaptation to the needs of the organism of Avliioh it forms a j)art." Appendages of the Bye. —Lacrimal Apparatus. — To keep the conjunctiva (the mucous membrane covering the anterior seg- FiG. 370.— Lacrimal and Meibomian glands, the latter viewed from the posterior surface of the eyelids. (The conjunction of the upper lid has been partially dis- sected off, and is raised so as to show the Meibomian glands beneath.) 1, free border of upper, and 2, free border of lower lid, with openings of the Meibomian glands; 5, Meibomian glands exposed, and 6, as seen through conjunctiva ; 7, 8, lacrimal gland ; 9, its excretory ducts, with 10, their openings in the conjunctival cul-de-sac; 11, conjunctiva (Testut). ment of the sclerotic and the cornea and lining the lids) moist and in normal condition is the function of the tears. They are secreted by the lacrimal r/l(ind, a compound racemose gland lodged in a depression at the upper and outer portion of the orbit. Its ducts, about seven in number, open on the upper and outer half of the conjunctiva near its reflection over the eyeball. At the edge of the upper and lower eyelids, at their inner ex- tremities, are openings, puncfa lacrhnalia, into which the tears pass after performing their function. These openings are the beginnings of the cayialiculi (Fig. 371), which open into the lacrimal sac, or the dilated upper extremity of the nasal duct, Avhich discharges at the inferior meatus of the nose, the open- ing here being partially closed by a fold of mucous membrane, the valve of Hasncr. Meibomian Glands. — On the posterior surface of the eyelids, Fig. ;-571. — 1, Canaliculus; 2, lacrimal sac ; 3, nasal duct ; 4, plica semilunaris ; 5, car- uncula lacrimalis. 682 THE NERVOUS SYSTEM. beneath the conjunctiva, are the Meil)omian glands (Fig. 370), thirty in number on the upper, and fewer on the lower lid. Their ducts open on the edges of the lids, and their secretion prevents the adhesion of the lids and the tears from running over them on to the cheeks. The Sense of Hearing. — The ear (Fig. 372), the organ of hearing, consists of three subdivisions : (1) External ; (2) middle ; and (3) internal. External Ear. — The external ear consists of the pinna or auricle, and the external auditory canal or meatus. The function of the Fig. 372. — Diagram of organ of hearing of left side : 1, the pinna ; 2, bottom of concha; 2, 2', meatus externus; 3, tympanum ; above 3, the chain of ossicles; 3', opening into the mastoid cells : 4, Eustachian tube ; 5, meatus internus. containing the facial (uppermost) and auditory nerves; 6, placed on the vestibule of the laby- rinth above the fenestra ovalis ; a, apex of the petrous bone; h. internal carotid artery ; c, styloid process ; d, facial nerve, issuing from the stylomastoid foramen ; e, mastoid process ; /, squamous part of the bone (Quain, after Arnold). pinna is to collect the sound-waves and direct them to the external auditory canal, which they traverse to reach the membrana tym- pani. In some animals, such as the horse, the auricles are very important, enabling the animal to detect the direction from which sounds come, and they are capable of considerable movement ; but in man they are not so important, altliough when the hearing is defective they are of assistance. That they are not essential to hearing is shown by the fact that when removed, hearing is not affected, and also by the fact that in birds, where they are absent, the sense of hearing: is well marked. SENiSK OF HEARING. 583 Tlie pinna (Fig, 374) is composed of yellow fibrocartilage covered by skin, although in some parts, as the /oLu/e, the cartilage is absent. It is attached to the meatus and other parts bv liga- ments and muscles. Fig. 373.— Semidiagrammatic section through the right ear : G. external audi- tory meatus: T. membrana trmpani ; P. tympanic cavity: o, fenestra ovalis ; r, fenestra rotunda ; B, semicircular canal ; S, cochlea ; Vt, scala vestibuli ; Pt, scala tympani iCzermak). External Auditory Meatus. — This canal, extending from the pinna to the membrana tympani, is about 3.2 cm. in length, the outer 1.3 cm. being of cartilage, except at the upper and back Fossa of helix Anthelix Helix. Fossa of anthelix. Tragus. Lobule. Fig. 374.— Exteriijil ear. part, where its place is taken by fibrous membrane. The inner 2 cm. is osseous. The entire canal is lined with skin, which in the cartilaginous portion of the canal contains sebaceous and perspiratory glands, their jiroduct being cerumen or ear-vax (p. 406). The skin lining the meatus also contains hair-follicles. 584 THE SERVO US SYSTEM. Inasmuch as in the examination of the ear and the treatment of its diseases it is necessary to introduce an aural specuhim (Fig, 376), a knowledge (^f the direction and shape of the canal is essen- tial. Its greatest diameter is at the external orifice and is vertical ; Fio. 375. — Muscles of the auricle: 1. attollens aurem : 2, attrahens aurem ; 3, retrahens aurem; J!^. helicis major; 5, helicis minor; (?, tragicus. with & , its acces- sory portion ; 7, aiititragicus; a, spine of helix; 6, concha (Testut). o its smallest diameter is in the middle. At the tympanic end the greatest diameter is horizontal. The direction of the canal is obliquely forward, inward, and downward. Before introducing the speculum the helix of the ear is raised upward, so as to straighten the canal as much as possible. Middle Ear. — Tliis is called also the tympa- num (Fig. 377). Membrana Tympani (Fig. 378). — This mem- branous structure separates the tympanic cavity from the external auditory canal. Its shape is oval, and the direction of its long axis is down- ward and inward ; its diameter along this axis C) liw ^^ about 9 mm. It is composed of three layers : An external or cuticvlar, which is an extension of the integument that lines the external audi- ( j I torv canal ; an internal, mucous, a continuation ^—^ of the •niucous membrane lining the tyin]>anic cavity ; and a middle, Jibrous, made up of both fibrous and elastic tissues. There are two vari- eties of these fibers — radiating, which radiate from the center to the circumference ; and circular, which form a ring at the circum- ference. The membrana tympani is set into a groove in a ring of bone, except at the upper j^art, where it is attached to the wall of the canal. This portion of the membrane is not so tense as Fig. 37G.— Aural speculum. SENSE OE HEARING. 585 ^'•'•"^'tKn^ Fig. 377.— Tympanum of left ear, with ossicles in situ: 1, suspensory ligament of malleus ; 2, head of malleus; 3, epitympanic region; 4, external ligament of malleus ; 5, processus longus of incus ; 6, base of stapes; 7, processus brevis of mal- leus; 8, head of stapes; 1), os orbiculare : 10, manubrium ; 11, Eustachian tube; 12, external auditory meatus; 13, membrana tympani ; 14, lower part of tympauum (Morris). Fig. 378. — Otoscopic view of left membrana tympani : 1, membrana flaccida : 2, 2', folds bounding the former ; 3, reflection from processus brevis of malleus ; 4, pro- cessus longus of incus (occasionally seen) ; 5, membrana tympani ; 6, umbo and end of manubrium; 7, pyramid of light (Morris). 586 THE NERVOUS SYSTEM. the rest, and has therefore received the name membrana flacdda. It is called also ShrapneWs membrane. When a normal membrana tympani is viewed through an aural speculum, there is seen a triangular spot or cone or pyramid of light, whose apex is at the end of the manubrium or handle of the malleus, and whose base is at the circumference. The membrane is funnel-shaped, with the concavity toward the meatus, at the apex being attached the tip of the manubrium, and at this point on the outer surface is the umbo (Fig. 378). Tympanic Cavity (Fig. 377). — In this cavity, which is situated in the petrous portion of the temporal bone, are the chains of bones, the ossicles, serving as a ^ ^ means of communication between the membrana tympani and the internal ear. It c o m m u n i c a t e s \ ^ \ /-'^M.^ posteriorly with the mas- toid antrum and the mas- FiG. 379. — The ossicles of the leit ear, external view (eularged) (after Gray). Fig. 380.— Malleus of the right side : a, anterior face ; b, internal face ; 1, caijitulum or head of malleus; 2, cervix or neck; 3, processus brevis ; 4, processus gracilis ; 5, manubrium ; 6, grooved articular surface for incus ; 7, tendon of musculus tensor tympani (after Testut). toid cells, and anteriorly with the pharynx by means of the Eusta- chian tul)e. Two openings, the fenestra ovalis and fenestra rotunda, give it communication with the internal ear. The roof of the tym- panic cavity, the legmen, is a very thin plate of bone, the only struc- ture separating this cavity from that in which lies the brain. It is on account of this slight separation that inflammation of the middle ear sometimes extends to the brain. The tympanic cavity is lined by mucous membrane, which is covered with ciliated epithelium except over the ossicles and the membrana tympani. Ossicles (Fig. 379). — These are three in number : the malleus, the incus, and the stapes. 3Ialleus (Fig. 380). — The malleus is about 18 mm. long, and consists of head, neck, manubrium, processius graciUs, and processus brevis. The head has a sreneral surface for articulation with the incus. SENSE OF HEARING. 587 The manubrium or handle is attached to the membrana tvmpani. The processus gracilis is attached to the Gasserian fissure hy bone and liijament. The processus brevis presses afjainst the niemljrana tiaccida, and its location is visible by inspection of the external Fig. 381. — The incus of the right side: a, anterior face; B, internal face: 1, body of incus; 2, processus brevis; 3, processus longus; 4, articular surface for the malleus; 5, a convex tubercle, processus lenticularis, for articulation M'ith stapes; 6, rough surface for attachment of the ligament of the incus (after Testut). surface of the membrana tvmpani, through which it shows (Fig. 378), The malleus is held in place by ligaments (Fig. 383). Incus (Fig. 381). — This is called also arabos and anvil-bone. The body is characterized by the presence of an articular surface for articulation with the malleus. It has two processes — processus brevis and processus longus. The processus brevis is attached by ligament to the margin of the opening that leads into the mastoid cells. The processus longus is nearly parallel with the handle Fig. 382.— The stapes: 1, base ; 2, anterior crus : 3, pos- terior crus: 4, articulating surface of head of the bone ; 5, cervix or neck (after Tes- tut). Fig. 383. — Ligaments of the ossicles and their axis of rotation. The figure represents a nearly horizontal section of the tympanum, carried through the heads of the malleus and incus: J/, malleus; /, incus; f. articular tooth of incus : Ifi.a. and Ig.e, external ligament of malleus; Ig.inc. ligament of the incus: the line a-x represents the axis of rotation of the two ossicles (from Foster, after Testut). of the malleus and ends in a round projection, os orbiculare or lenticular process, which articulates with the head of the stapes. During fetal life the os orbiculare exists as a separate bone. Stapes (Fig. 382). — This bone is so called from its resemblance 588 THE NERVOUS SYSTEM. to a stirrup. It consists of a head, which articulates with tlie OS orbiculare ; a neck, into which the stapedius muscle is inserted ; and two crura, which are connected with the base, this being attached by ligamentous tissue so as to close the fenestra ovalis. Ligaments of the Ossicles. — The ossicles are connected with one another, and also with the walls of the tympanum, by ligaments (Fig. 383). One of these, the anterior ligament of the malleus, was at one time supposed to be a muscle and was described under the name levator tympani. Muscles of the Ossicles. — These are two in number — tensor tympani and stapedius. Tensor Tympani. — This muscle lies in a bony canal which is above the canal containing the Eustachian tube, and sepa- rated from it by the j^rocessus cochlear if ormis, a thin plate of bone. It has its origin from the petrous bone, the cartilaginous portion of the Eustachian tube, and the bony canal in which it lies. Its tendon enters the tympanum and bends at almost a right angle around the end of the processus cochleariformis, and is inserted into the manubrium near the neck. Its nervous supply is a branch from the otic ganglion. When this muscle contracts, the membrana tympani is drawn inward and made more tense. Stapedius. — This muscle arises from the interior of the pyramid which is situated just behind the fenestra ovalis, and just below the opening of the mastoid antrum, and its tendon passes out at an opening in the apex ; it is inserted into the neck of the stapes. Authorities do not agree as to the effect of the contrac- tion of this muscle. Gray says that "it draws the head of the stapes backward, and thus causes the base of the bone to rotate on a vertical axis drawn through its own center; in doing this the back part of the base would be pressed inward toward the vestil>ule, while the fore part would be drawn from it. It probably compresses the contents of the vestibule." Sewall, in the American Text-Book of Physiology, says : " Con- traction of the muscle would cause a slight rotation of the stapes round a vertical axis, so that the hinder part of the foot of the ossicle would be pressed more deeply into the fenestra, while the remaining portion would be drawn out of it. Its action probably reduces the pressure in the cavity of the perilymph, and thus is antagonistic to that of the tensor tympani." The nervous supply of this muscle is the tympanic branch of the facial, which reaches the muscle through a canal in the pyramid which communicates with the aquteductus Fallopii. Eustachian Tube (Fig. 384). — Through this channel the tym- panum is in communication with the ]>harynx. It is about 36 mm. in length, and passes downward, forward, and inward. It begins in the lower part of the anterior wall of the tympanum, and is bony for about 12 mm. It then becomes cartilaginous, and SENSE OF HEARING. 589 remains so throughout tlie rest of its course. It \s luied by mucous nicmhrauc, the epithelium of which is ciliated. The direc- tiou of the motion of these cilia is from the tympanum to the pharynx, so that the secretion of the membrane lininti; the tym- panum will escape into the pharynx. Its opeuinj,^ in the pharynx is ordinarily closed, except during the act of swalk.wing, when it momentarily .)pens ; or it mav be made to open by closmg the mouth holding the nostrils closed with the thumb and finger, and foreibl'v blowing. The pharyngeal opening is at the upper lateral part of the pharynx behind the inferior turbmated bone. There Portion of Eust I Jt_ i-liian tube frti f, from gland's V ; Cartila^'o - Glands. -_-. Mucosa of the pharynx. Glands. Fig 384 —Cross-section of the Eustachian tube with its surrounding parts ; X 12 (from a preparation by Professor Eudinger). is a band of muscular tissue, the dilatator tubce, which joins the tensor palati. . i ,,- Mastoid Antrum.— This is a cavity which opens mto the attic or epitympanic recess, an extension upward and backward of the tympanic cavity. It is in this recess that the head of the malleus and a part of the incus are situated. The antrum communicates with the mastoid cells in the mastoid process. Antrum and cells are lined bv mucous membrane which is continuous with that ot the tympanum. This extension of the mucous membrane explains how "inflammation of the middle ear may extend to the mastoid cdls Fenestra Ovalis (Fig. 385).— This is an oval opening in the internal wall of the tympanum into the vestibule of the internal 690 THE NERVOUS SYSTEM. ear, and is closed by the stapes, an annular ligament uniting the bone to the fenestra. Fenestra Rotunda, — This opening, also on the internal wall of the tympanum, leads into the cochlea of the internal ear. It is Fig. 3S5. — Eight bony labyrinth, viewed from outer side: the figure represents the appearance produced by removing the petrous bone down to the denser layer immediately surrounding the labyrinth : 1, 2, 3, the superior, posterior, and hori- zontal semicircular canals ; 4, 5, 6, the ampullffi of the same ; 7, the vestibule ; 8, the fenestra ovalis ; 9, fenestra rotunda ; 10. first turn of the cochlea ; 11, second turn ; 12, apex (from Quain, after Sommerringi. Fig. 386. — Interior view of left bony labyrinth after removal of the superior and external walls: 1, 2, 3, the superior, posterior, and horizontal semicircular canals; 4, fovea hemi-elliptica ; 5, fovea hemispherica ; 6. common opening of the superior and posterior semicircular canals : 7, opening of the aqueduct of the vestibule ; 8, opening of the aqueduct of the cochlea : 9. the scala vestibuli ; 10. scala tympani ; the lamina spiralis separating 9 and 10 (from Quain, after Sommerring). closed by the memhrana tympani secundaria, -which is made up of an external or mucous layer, a continuation of that lining the tympanum ; and an internal or serous, a continuation of that lining the cochlea ; between these two is a third or fibrous layer. Be- SENSE OF HE A RING. 591 tween the two fenestrae is the promontory, a prominence caused by the projc'i'tion of the first turn of the cochlea. Internal Ear (Figs. 3i(( ductus vestibuli communicates with the vestibule by an opening at the posterior part of the inner wall. Through this canal pass a vein and the ductus endolymphaticus. The/oira or fossa hemi-elliptica is an oval depression on the roof of the vestibule. Between it and the fovea hemispherica is the crista vestibuli. Posteriorly the semicircular canals open into the vesti- bule, while the opening into the cochlea, a])ertura scalce vestibuli cocfdece, is situated anteriorly. Semicircular Canals. — These are three in number, situated behind the vestibule and above it. Each has a diameter of about 1.5 mm., except at one end, the ampulla, where the diameter is 2.5 mm., and each canal is so arranged as to be at right angles to the others. The superior is vertical and at right angles to the posterior surface of the petrous bone ; its ampullated extremity opens into the vestibule, while its other extremity joins with the non-ampullated extremity of the posterior canal, and these open into the vestibule by one common opening. The jjosterior canal is also vertical, but parallel with the posterior suriace of the petrous bone. Its ampullated extremity opens into the vestibule. The external canal is horizontal, and both its extremities open into the vestibule. It will be seen that the three canals have but five openings into the vestibule, one opening being common to two canals. Cochlea (Fig. ?)^~). — The cochlea is situated in front of the vestibule, with its apex directed outward, forward, and downward, its base corresponding to the internal auditory meatus. It is 5 592 THE NERVOUS SYSTEM. ram. long and 9 mm. broad at its base. It consists of an axis, the modiolus or columella, which runs through the entire structure, from the base to the apex ; around the modiolus runs the spiral canal. At the base the modiolus is perforated to transmit tilaments of the cochlear branch of the auditory nerve, and through it ex- tends the canalis centralis modioli, which transmits a nerve and an artery. The spiral canal is about 2 mm. in diameter and 3.3 cm. in length. It makes two and three-fourth turns, clockwise — /. e., Fig. 387. — The cochlea and vestibule as seen from above : A, cochlea ; B, vesti- bule ; C, internal auditory canal ; X>, tympanum. 1, Lower border of fenestra ovalis ; 2, vestibulotympanic cleft ; 3, fossa hemispherica ; 4, fossa hemi-elliptica ; 5, fossa cochlearis ; 6, orifice of aqueduct of vestibule ; 7, lower orifice of posterior semi- circular canal ; 8, non-ampullary orifice of the external semicircular canal ; 9, scala tympani ; 10, scala vestibuli; 11, cupola; 12, lamina spiralis, with 12', its vestibulary origin ; 12", its external border ; 13, helicotrema (Testut). in the direction taken by the hands of a clock — around the modiolus. At the apex the canal terminates in the cupola. This canal is partially divided into two by a bony septum, the lamina spiralis, which consists of two thin plates of bone between which are minute canals for the transmission of nerve-fibers. The lamina spiralis extends from the modiolus only about half-way toward the outer wall of the spiral canal. In the recent state there is a membrane, the membrana basilaris, extending from the edge of the lamina spiralis to the outer wall, dividing the canal into two parts, the lower being the scala tympani, while the SENSE or iir.MUNCi. 593 upper is au^ain subdivided hy a iiiciiil)iaiic, the nicinhranc of Rcissner, into two canals : that hetwocn the inner wall of the cochlea and this membrane beint;: the scala vesfihu/i ; and that between the outer wall and the mend)rane of lleissner, havinjr the niembrana basilaris as its base, the .scala media, ductus coch/ecc, or canalis cochlecc. This latter is in reality a part of the membranous labyrinth, not of the osseous, but it is somewhat more convenient to describe it at this point. At the a|)ex of the cochlea the lamina spiralis ends in the /kuiiuIus, a hook-like process, and here the scala vestibidi and scala tympani communicate, the opening being the helicotrema. At the junction of the lamina spiralis and the modiolus, and winding around the latter, is the canalis spiralis modioli, which lodges the y far the older, and may be regarded as the theory usually held to explain what takes place in the cochlea. The cochlear division of the auditory nerve sends into the modiolus of the cochlea branches that pass in between the plates of the lamina spiralis, where they form a plexus in which are ganglion-cells, from which the nerve-filaments pass to the organ of Corti, terminating, it is believed, in the hair-cells. The waves already referred to as being set in motion in the endolymph pass over and under these cells, with Avhich the nerve- filaments are connected, and cause the basilar membrane on which they rest to vibrate. This motion is communicated to the outer rod's of Corti, which in turn pass it to the hairs of the special audi- torv cells through the medium of the perforated membrane, and from SENSE OF JIEARL^G. GU3 there it passes to tlic nerves. Here it is eoiiverted into impulses whicli are transmitted to tlie Wraiii, wliere s<»iin(l is produced. It has been supj)()seil that tiie roils of Corti are so arranged as to vibrate with partieuhir tones, one rod for each tone, but it is doubtful whether such a differentiation can be made out in the auditory apparatus. The rods are not present in the ears of birds, and there is no reason to believe that birds cannot apj)reciate musical tones. In the basilar meml)rane there are fillers enough to respond to all the notes that can l)e aj)preeiated — that is, from 33 waves to 38,000 waves in a second. It is more probable that the rods simply act as levers to communicate the vibrations of the fibers of the basilar membrane to the terminal nerve-filaments in the auditory cells. Just how one is able to distinguish the differences in the in- tensity (loudness), pitch, and quality of sounds is not understood. The exj)lanation most generally accepted at the present time, as to pitch at least, is that as when a tone is sung over the strings of a piano, certain strings are set in vibration sympathetically, so in the basilar membrane, where, as in the piano, there are filters of different lengths, these respond to different tones, and that in con- nection with each tone there is a separate filament of the auditory nerve, so that if the note is a high one a certain fiber is set in vibration, and the nerve-filament in communication with it transmits an impulse to certain cells in the brain, which when excited give the impression of a high note, and so with other notes and other nerve-cells. The Telephone Theory. — The introduction of the telephone and a study of its mechanism have led some writers to question the explanation which is generally accepted of the mechanism of hearing, and to suggest that as the single telephone wire transmits the complex sounds produced by an orchestra to a distance where they are reproduced in all their variety of intensity, pitch, and quality, so " the cochlea does not act on the principle of sympa- thetic vibration, but that the hairs of all its auditory cells vibrate to every tone, just as the drum of the ear does; that there is no analvsis of complex vibration in the cochlea or elsewhere in the peripheral mechanism of the ear ; that the hair-cells transform sound-vibrations into nerve-vibrations similar in frequency and amplitude to the sound-vibrations ; that simple and complex vibra- tions of nerve-molecules arrive in the sensory cells of the brain, and there produce, not sound again, of course, but the sensations of sound, the nature of which depends not upon the stimulation of different sensorv cells, but on the frequency, the amplitude, and the form of the vibrations coming into the cells, probably through all the fii)ers of the auditory nerve." This explanation has been put forth by Prof. William Rutherford under the title of the " Telephone Theory of the Sense of Hearing." 604 THE NERVOrS SYSTEM. In referring to this subject, Waller compares the basilar mem- brane to the memljrana tympani in the following language : " It is the internal drum-head, re]>eating the complex vibrations of the membrana tympani, and vibrating in its entire area to all sounds — although more in some parts than in others — giving what we may designate as acoustic pressure patterns between the membrana tectoria and the subjacent field of hair-cells. In place of an analysis by sympathetic vibration of particular radial fibers, it may be imagined that varying combinations of sound give vary- ing pressure patterns, comparable to tiie varying retinal images of external objects." There are several terms used in the discussion of the subject of sound which it is important to understand ; especially is this true for the medical student, for he will constantly meet them in his study of physical diagnosis. Period ; Amplitude ; Frequency. — If a weight attached to a rubber cord (Fig. 397) is pulled down and then released, the weight and the particles composing the cord will vibrate, and any particle, as a, will oscillate between two extreme points, as b and c, which are equidistant from a. The motion of a from c to b and back again to c is one vibratioji or one complete vibration, and the time this Fig. 397. — WeiKlit aud cord. • • .i • i r j.\ •! j.* occupies is the period oi the vibration. The distance from a, when the particle is in equilibrium, to b or to c is the amplitude of the vibration, and the number of complete vibrations in one second is the fre- quency. Noises. — These are sounds produced by irregular vibrations — i. e., wanting in periodicitv ; or by discordant or dissoyiant sounds — i. e., sounds which differ from one another in pitch ; or they may be single, sudden sounds, as the report of a cannon. Noises are disagreeable sounds. Musical Sounds. — These are sounds produced by regular vibra- tions, and thev produce a pleasing effect upon the ear. It should be .said, however, that what may under some circum- stances be a noise may, under others, produce the effect of a musical tone. Haughton says : " Xothing can be imagined more purely a noise or less musical than the jolt of the rim of a cab wheel against a projecting stone ; yet if a regularly repeated succession of such jolts takes place, the result is a soft, deep, musical sound that will bear comparison with notes derived from more sentimental sources." And Zahni says: "With a sufficient number of properly tuned bottles a skilful performer could, by k SENSE OF HEARING. ^'^^^ merely withdrawing the corks, easily evoke a simple melody that every one v;ould rceot^nize. Musical sounds ditVer in intensity, pitch, and quality. Intensity.— This depends upon the energy with which the particles of air in vibration strike upon the air, and: (1) \ aries directly as the square of the amplitude of vibration oi the sound- ing body ; (2) varies inversely as the square of its distance ; and (3) diminishes with the density of the air. Loudness is oftentimes spoken of as synonymous with intensity, but it depends somewhat upon the condition of the ear an* Y)^ three or four times that emitted ■ j: ^^^^^--—----^ l>v the string when it vibrated as a -^ ^^v.^-! — i_.-..__:^^3 whole. Such a series of tones is a ^^ -^ — harmonic series, and all the tones ^'' above the fundamental are har- monic overtones, or upper partial Fig. 398.— Vibrating strings. tones, or simply partial tones. To demonstrate this more effectively, a sonometer may be used, which con- sists of a wire stretched over a sounding-box (Fig. 399) with a graduated scale, so that the divisions of the wire may be accurately determined. In order to produce these overtones it is not neces- sary to divide the string with the finger, or, in the case of the sonom- eter, the wire with the bridge ; for in the vibration of the string or wire as a whole it divides itself, so that it may vibrate as a whole and also in segments ; and consequently, while the whole vibrat- ing string or wire emits the fundamental tone, the subdivided seg- ments emit each its own partial tone, producing therefore compound tones, the fundamental tone tieterminins" the pitch. As a rule, the Fig. .399.— Sonometer. sounds of musical instruments are compound tones, and, as Helm- holtz has shown, it is the partial tones which determine their quality by which they are differentiated from one another, there being no difference in the fundamental tones. Thus if a key on a piano, say " middle C," is struck, the string will vibrate as a whole 132 times in a second, producing one fundamental tone, C, and it will also break up into segments which will vibrate respectively 264 times, producing the octave C ; 396 times, producing the fifth above this ; 528 times, producing the second octave C" ; 660 times, producing the third above this, etc. SENSE OF HEARING. 607 These tones are believed to form a composite wave, and as such to strike the membrana tympani : and, according to the " piano theory," this wave is analyzed into its component tones by the basilar membrane, each of" whose fibers is caused to vibrate by a partial tone ; while according to the " telephone theory" this analysis takes place in the brain. Besonntors. — That musical sounds possess this compound char- acter Helndioltz demonstrated by means of resonators (Fig. 400), which consist of metallic globes ot" various sizes having two openings of unequal diam- eter. If one of these is held with its small opening to the ear, and the large one is held toward a source of sound, the resonator will resound when a tone is emitted which corresponds to the vibration- rate of its contained air, and to no other, and by using a series of these the various overtones may be identified. To sura up the properties of sounds and their causes, we may say that the amplitude of a wave determines its intensity ; its vibration-frequency, its pitch ; its form, its quality. Semicircular Canals, Utricle, and Saccule. — The utricle and saccule have been regarded by some authorities as having the function of responding to irregular vibrations, and as being connected, thereff»re, with the perception of noises, while the perception of musical sounds depends upon the cochlea ; l)ut the consensus of opinion now is that, together with the semicir- cular canals, they are connected with the important function of the preservation of the equilibrium of the body, the utricle and saccule with ."italic equilibrium — i. e., when the bodv is in a state of rest ; the semicircular canals with dynamic equilibrium — /. e., when the body is in motion. This subject is discussed in connection with the cerebellum (p. 481;. Fig. 400. — Eesonator. V. REPRODUCTIVE FUNCTIONS. The reproductive functions are those concerned in the perpetua- tion of tlie species. In tlie lower forms of animal life, where the individual consists of a single cell, this process of reproduction is very simple, consisting of the division of the cell into two, each of which has the power of dividing to form new individuals in the same manner as it was formed. This is asexual reproduc- tion. In the higher animals the reproduction is sexual — that is, it requires the union of two elements produced in the organs of two individuals, the male and the female, neither of which can accomplish the process alone. REPRODUCTIVE ORGANS. These organs, which are also called the genital or generative organs, are in the male the testes, each with its duct, the vas Fig. 401. — Diagram representing the male genital apparatus of right side: A, bladder; B, prostatic urethra; C. membranous urethra: 1). spongy urethra. 1, Eight testicle: 2. epididymis; 3, vas deferens, with 3', its ampulla: 4, seminal vesicle; 5, ejaculatory duct opening at the verumontanum ; 6, Cowper's gland : 7, its excre- tory duct (Testut). deferens, the vesiculse seminales, and the penis (Fig. 401) ; and in the female, the ovaries, Fallopian tubes, uterus, and vagina. 608 GENITAL ORGAyS OF THE MALE. 609 Genital Organs of the Male. — Testes. — The testes or testicles (^Fig. 402), two in niinibtT, are situated in the scrotum. They are composed of lobules, the number of wliich in each testis is variou.slv estimated at from two hundred and fifty to four hundred. In each lobule are convoluted seminiferous tubules, tubuli seminiferi, varyino; in number from one to three. These tubules contain epitiielial cells of two varieties, mi^fen- tacular cells, or •'^drioirs columns, and sjiennator/enic cells, the latter being related only to the formation of spermatozoa. These two varieties of cells are sometimes described as the parietal cells. Internal to these are the mother-cells, which are derived from the sperraatogenic cells by the process of mitosis or karyokinesis Ghihiis Mitjor Vagn Efferentia Fig. 402.— Vertical section of the testicle to show the arrangement of the ducts (Leroy). (p. 8). These give rise to a third and more internal layer of daughter-cells, from whose nuclei, liy the disappearance of the cell-body, the spermatobhists are developed. These in turn become spermatozoa. This ]>rocess by which spermatozoa are formed is known as spermafoc/enesis. Spermatozoa (Fig. 403). — A human spermatozoon is about 50 a in length, and consists of a head from 3 u to 5 // long, a body and a tail, the last terminating in the end-piece of Retzius, which is the end of the axial filler which runs through the center of the body and tail. The tail during the living condition is in rapid motion, bv virtue of which the spermatozoon can travel quite rapidly. The vitalitv of spermatozoa is considerable, as they can live for several 610 REPRODUCTIVE ORGANS. days outside the body, and they are also very resistant to low temperatures. They appear at the time of puberty, and have been ^' ^ found in individuals ninety years f^- b of age, though they are not com- FiG. 403. — Human spermatozoa. The two at the left after Eetzins ; the one at the extreme left is seen in profile ; the others in surface view ; the one at tlic right is drawn as de- scribed by Jensen : a, head ; b, ter- minal nodule ; c, middle piece ; d, tail ; e, end-piece of Retzius (Bohm and DavidoflF). Fig. 404. — Spermatozoa : a. human ; I, of the rat ; c, of menobranchus (X 480). Epithelium. Middle cir- cular mus- cular layer. Outer longi- tudinal muscular layer. Fig. 405. — Cross-section of vas deferens near the epididymis (human) (Huber). GENITAL ORGANS OF THE MALE. 611 nionly Ibuiul in .semen alter the age of seventy or seventy-five years is past. Tlie spermatozoa of different animals vary in size, tliouo;li their general appearance is much the same (Fig. 404). Their number is very great ; some writers state that in a single ejaculation as many as 2o,()00,000 may he discharged, while one has placed their numhcr as high as 41 2,")00,0()0. lioth figures may he correct, inasmuch as the amount ol" semen ejaculated varies at each emission. The seminiferous tubules terminate at the apices of the lobules Fig. 406. — Vas deferens and seminal vesicle, A, seen in longitudinal and, B, in horizontal section: 1, vas deferens ; 2, its terminal or ampuUary portion ; 3, semi- nal vesicle with, 3', its partitions; 4, its terminal portion ; 5, ejaculatory duct (Testut). Fig. 407. — Right seminal vesicle, unfolded and seen on its posterior aspect (subject of forty years, previous injection of tallow) : 1. vas deferens, with, ]', its ampulla ; 2, seminal vesicle with, 3, its lateral prolongation ; 4, its enlargements in form of cecum ; 5, protuberances of its wall; 6, junction of the vesicle and vas deferens ; 7, ejaculatory duct (the dotted line, x x, indicates the level of the upper extremity of the vesicle before its unfolding) (Testut). in the vasa recta (straight tubes), about thirty in number. In the mediastinum these tubes form a network, the rete testis, the vessels of which end in the vasa efferentia, about fifteen in number. These vessels connect the testicles with the epididymis, the con- tinuation of which is the vas deferens. The canals of the rete testis are lined by non-ciliated epithelium ; the vas aberj-ans, how- 612 REPRODUCTIVE ORGANS. ever, which is connected with it, has ciliated epithelium. Ciliated columnar and non-ciliated cubical epithelium line the vasa efferentia. Vas Deferens (Fig. 405). — This duct, the excretory duct of the Fig. 408. — Sagittal section through the ampulla of the right vas deferens and ejaculatory duct: 1, ampulla of vas deferens; 2, ejaculatory duct: 3, seminal vesicle dissected away in its middle portion; 4, its opening into the ejaculatory duct; 5, bladder; 6, urethra; 7, prostate; 8, verumontanum. testis, has a thick muscular wall. Its lining epithelium is partly simple ciliated columnar, and partly stratified ciliated columnar, Fig. 409.— Seminal vesicles and vasa deferentia, posterior view: 1, bladder; 2. prostate; 3, 3', seminal vesicles; 4, 4', vasa deferentia; 5, ejaculatory ducts; 6, fi', ureters; 7, 7, peri vesicular cul-de-sac of peritoneum; 8, interdeferential triangle, in direct relation with the rectum, from which it is separated only by the prostato- peritoneal aponeurosis. The two crosses (+ +) indicate the points at which the ureters disappear in the vesical wall (Testut). though the cilia are sometimes absent. At the base of the bladder this duct lies between it and the rectum, and here presents an GENITAL ORGANS OF THE MALE. 613 enlargement, the ampulla (Figs. 406, 407), beyond which, at the base of the prostate, it narrows and joins with tlie duct of the vesicuhi seniinalis, thus iorMiiug tlie ejacuhitory duct (Fig. 40«). The total length of the duct is about 60 cm. Vesicula :Scminaltf> (Fig. 409). — This structure is a diverticulum from the vas deferens, and glands exist in its mucous membrane which is covered with non-ciliated columnar epithelium. Some authorities regard it as a storehouse for the semen, while others do not regard this as one of its functions. Bohm and Davidofi' state that " spermatozoa are, as a rule, not met with in the seminal r'xN Fig. 410. — Section of penis, bladder, etc.: 1. symphysis pubis; 2. prevesical space; 3. abdominal wall: 4, bladder; 5, urachus: fi. seminal vesicle and vas deferens; 7, prostate : 8, plexus of ."^antorini ; 9, sphincter vesicae; 10. suspensory ligament of penis; 11, penis in flaccid condition; 12. penis in state of erection ; 13, ftlans penis; 14. bulb of urethra; lo. lul-de-sac of bulb, a, Prostatic urethra; 6, membranous urethra ; c. spongy urethra (Testut). vesicles." The vas deferens and especially its ampulla serve to retain the semen until ejaculated. A considerable amount of fluid is added to the semen by the secretion of the mucous membrane lining the vesicula seminalis, and this is probably its most im- portant function. The ejaculatory ducts discharge into the urethra at its pro.static part. The prostate gland and Cowper's glands contribute also to the formation of the semen. Semen. — The semen or seminal fluid consists of secretions from G14 REPRODUCTIVE ORGANS. the testes, vasa deferentia, vesiculae seminales, prostate, Cowper's glands, and the muciparous glands of the urethra. It is whitish in color, viscid in c(jnsistency, alkaline in reaction, and possesses a characteristic odor. The amount ejaculated varies from 0.5 c.c. to 6 c.c. It contains from 82 to 90 per cent, of water, nuclein, protamin, proteids, xanthin, lecithin, cholesterin, fat, sodium and potassium chlorids, sulphates, and phosphates. From it may be obtained Charcot's crystals, which are a phosphate of the nitrogen- ous base, spermin, and which have their origin in the portion of the semen which is contributed by the prostate ; to the decomposition of the substance which produces these crystals the odor of the semen is at- tributable. While the spermatozoa are the essential fertilizing agents, the presence of the fluid portion of the semen is important as giving to them their mobility, without which they could not travel in the genera- tive passages. Penis (Fig. 410). — The penis serves a double purpose, inasmuch as it is the organ of copulation and also the termination of the urinary passages. The former function is undoubtedly the essential one, for there is no reason why the urinary passages could not terminate at the surface of the body ; it is, however, manifestly advantageous in provid- ing for the perpetuation of the spe- cies that the semen should be ex- pelled as near as possible to the mouth of the uterus, a result which is obtained by the intromission of the penis. The penis consists of erectile tissue arranged in three subdi- visions, two above, corpora cavernosa, and one below, corpus spongiosum, which latter terminates in the glans penis. The corpora cavernosa are surrounded by fibro-elastic sheaths from which are given oif (rabeculce. These pass inward, and between them are spaces which contain venous blood. A similar structure characterizes the corpus spongiosum which encloses the urethra. The arteries which supply the penis are derived from the internal pudic (Fig. 412). Sensory nerves are distributed to the Fig. 411. — Sagittal section of the anterior extremity of the penis : 1, glans penis ; 2, corpus cavernosurn : 3, 3, spongy portion of urethra; 4, meatus urinarius; 5, fossa uavicularis ; 6, left half of the valve of Guerin ; 7, sinus of Guerin between the valve and the anterior wall of the urethra ; 8, left lateral border of urethra: 9, its lower surface ; 10, prepuce pushed back behind the glans; 11, frenum ; 12, integument; 13, dorsal vein; 14, tibrous partition between the corpus cavernosum and corpus spongiosum (Testut). GENITAL OnaAXS OF Till-: Fh'MALi:. (;i5 skin of the ponis, ami ospocially to the <;hiii.s jK-nis, where they terminate in Meissner's eorpnseU's, Kranse'.s si)herie end-bnlbs, ami i^euital eorpnseles (Fig. 41.")). CiU^ Fig. 4 12.— Diagram of the arterial circulation of the penis : 1, corpus cavernosuui, with 1', its root ; 2, suspensory lipauient ; 3, corpus spougiosuna with 4, bulb ; a. glaus; 6, internal pudic artery; 7, bulbo-urethral artery, with 7', its bulbar branch, 7", its anterior branch going to the frenuin; 8, arteria cavernosa, with 8', its recur- rent braTich; 9, dorsal artery; 10, 10, its lateral branches; 11, its termination in the glans (Testut). Sensory nerves are distribnted also to the verumontanum, in the urethra, and the pleasnrable sensations connected with coitns are due to the excitation of the nerves here distributed, as well as to those supplying the glans penis. In addition to sensor y nerves there are also distrib- uted to the penis e x c i t o r nerves, iiervi erigentes, which are derived from the first and second, and sometimes from the third, saeral nerves ; they are vasodilator nerves, and have their origin in the sex- ual center of the spinal cord. Genital Organs of the Female. — Ovary. — The ova- ries (Fig. 414), two in num- ber, are attached to the pos- terior surface of the broad ligament, one on each side of the uterus, with which they are connected by the ova- rian lif/amcnf, a fibromuscular structure. They are covered by ])eritoneum, except at the hilum, which is, however, somewhat modified, its me.sothelial cells form- ing the germinal epithelium (Fig. 415), the cells of which are Fig. 413. — Genital cori)uscIe from the glans penis of man ; methylene-blue stain (Dogiel, Arch. f. mik. Anat., vol. xli.). 616 REPROD UCTIVE OR GA SS. /\ ^ "■"^A Fig. 414. — Posterior view of left uterine appendages: 1, uterus : 2,Fallopian tubes; 3. fimbriated extremity and opening of tbe Fallopian tube : 4. parovarium : 5. ovary ; 6, broad ligament; 7, ovarian ligament; infundibulopelvic ligament (Henlei. g c ^ c Fig. 41o. — Section through part of ovary of adult bitch : a. germinal epithelium ; 6. h. ingrowths f^egg-tubes) from the germinal epithelium, seen in croi^s-section ; c. c, young Graafian follicles in the cortical layer: '/. a more mature follicle, containing two ova (this is rare) : e and /, ova surrounded by cells of discus proligerus; g, h, outer and inner capsules of the follicle; i. membrana granulosa; I. blood-vessels; m, m. parovarium ; g. germinal epithelium commencing to grow in and form an egg- tube : 2, transition from peritoneal to germinal epithelium (from WaldeyerJ. GENITAL ORdAXS OF TIIE Fh'MAI.h'. 617 cubical or cyliiulrical aiul liioluT iIkiii those uf the rest of tlio peritoneum. At tiio liihim the comieetive ti.ssue of tiie ovarian ligament passes into the ovarv, forming the .stroma (Fig. 41 «j), which constitutes the greater part of the organ. The sjjindle- shaped cells of the stroma are reganled by His as nnstriped muscle-cells, while Wakleyer, Henle, and others consider them to be connective-tissue cells, l^eneath the germinal epitlielium is a condensed jiortion of the stroma, wiiieh was formerly deseril)ed under the name of tunicd albuginea, and was regarded as a cover- ing or coat of the ovary. The outer third of the ovary is the cortex, while the inner or deeper two-thirds is the medulla, in Fig. 416. — Part of the same section as represented in Fig. 415, more highly enlarged : 1, small Graafian follicles near the surface ; 2, fibrous stroma ; 3, 3', less fibrous, more superficial stroma ; 4, blood-vessels ; 5, a follicle still further advanced ; 6, one or two more deeply placed ; 7. one further developed, enclosed by a prolonga- tion of the fibrous stroma; 8, part of the largest follicle; a, menibrana granulosa; h, discus proligerus; c, ovum ; d, gorniinal vesicle; e, germinal spot (Schriin). which are the blood-vessels giving to this medullary portion another name by which it is sometimes known, zona vascidosa. In the cortex above are the Graafian follicles, the medulla con- taining none of them. These are sacs varying in size according to the stage of their development. In the Graafian follicles are the ova, the least developed of which are covered by a single layer of cells, those further advanced, by several layers, con.stituting the menibrana granulosa. The ova and the cells are derived from the germinal ej)ithelium. A mature Graafian follicle (Fig. 417) has a diameter of from 8 to 19 mm., and extends from the medulla to the surface of the ovary and projects therefrom (Fig. 418), rupturing at the most 618 REPR OD UfJTI VE OR GA XS. projectiug part and permitting tlie escape of the ovum. The wall of the follicle, tfieca foUicu/i, is a condensed layer of the stroma, ''^jt-. ligerus. nal vesicle. Fig. 41'; BUiOd- vessel. -Section of fully developed Graafian follicle from injected ovary of pig; X 50 (Bobm and Davidoff;. and is itself divisible into an outer layer of fibrous connective tissue, tunica externa, and an inner, tunica, interna, which is charac- terized by the presence of blood-vessels and of cells. Within the theca is the meni- hrana grunuJoHa or stratum rjrarodonum, which is com- posed of several layers of small polyhedral cells. In one portion of the membrana granulo.sa the cells are very numemus, constituting the (liacua prolifjcrus, in \\hich the ovum lies embedded. The cells of the discus pro- ligerus which are in contact witli the ovum are arranged radially, con.stituting the corona radiata (Fig. 421). Between the discus proligerus and the membrana granulosa, except at the point where the two are in contact, is a cavity, the antrum, which is filled with Fig. 418. — Ovary with mature Graafian follicle about ready to burst fEibemont- Dessaignes;. GENITAL ORGANS OF Til?: FEMALE. 619 a fluid, liquor J'o//icnfl, funned l)y a secretion of the cells and by the dcstnu'tioii of .some ol" tlieni. (Tri'aalian follicles continue to be formed in tiie ovarv for a short time after birth, and have been estimated to number, in both ovaries, more than 70,000 ; but a small jn-oportion of these, however, become mature, the rest undergoing degeneration. During the development of Graafian follicles the ova which they contain also become developed in the following manner (Nagel, R(»hm and Davidoff ). In the early ])eriod of the develop- ment of the ovary the germinal epithelium pushes into the sub- jacent connective tissue in solid projections (Fig. 415) ; these form the prhnary proach to regularity in the develop- ment of either the Graafian follicles or the ova. At undetermined periods Graafian follicles rupture and mature ova are discharged, together with the cells of the discus proligerus. This ripening and discharge of ova constitute ovulation. The cause of the OVCLATrON. 627 rupture of the follicle is still iiii unsettled question. In discussing this subject IJiihin und Davidotf say : "The manner in which the fully developed Graafian follicle hursts and its ovum is freeil is still a subject of controversy; the following may be said regarding it : By a softening of the cells forming^he pedicle of the discus ])roligerus, the latter, together with the ovum, are separated from the remaining granulosa, and lie free in the liquor foUiculi. At the point where the follicle comes in contact with the tunica albuginea of the ovary the latter, with the theca folliculi, becomes thin, and in this region, known as the stigma, the blood-vessels are obliterated and the entire tissue gradually atrophies; thus a point of least resistance is Fig. 431. — a, isolated muscle-elements of the non-pregnant uterus ; B, cells from the organ shortly after delivery (Sappey). formed which gives way at the slightest increase in pressure within the follicle, or in its neighborhood. " The increase of pressure within the follicle, leading to its rupture, is, according to Nagel, due to a thickening of the tunica interna of the theca of the follicle. The cells of this layer pro- liferate and increase in size and show yellowish colored granules. This cell-proliferation leads to a folding of the tunica interna, the folds encroaching on the cavity of the follicle, and causing its contents to be pushed toward the stigma." Piersol states that the liberation of the ova usually takes place at definite times, which in general coincide with the men- strual epochs, one or more ova being set free at each period. This t)28 REPRODVCTIVE ORGANS. coincidence, however, is l)y no means necessary or invariable, since ovulation undoubtedly proceeds independently of menstruation. Other authorities regard the intervals between periods of ovula- tion as very irregular. J. Bland Sutton, in his iSurgical Diseases of the Ovaries and Fallopian Tubes, says : " In the ovary of the human fetus ova ripen, form follicles, and undergo suppression duriny Fig. 438. — Prof. August Martin's case of ovarian pregnancy. The intact tube is seen lying above the ovarian sac containing the fetal envelopes. end of the tube which has become intimately connected with the ovary ; pregnancy in an accessory tube-end which has become attached to it ; pregnancy in the ovarian fimbria, which may be hollow sometimes, representing the extreme outer end of the tube ; pregnancy in the tube which has extended into the ovarian sac of peritoneum, which occasionally occurs in women." The terms " extra-uterine pregnancy " and " ectopic pregnancy " are ordinarily used synonymously, but there is really a distinction. The term " ectopic " implies that the gestation is outside the uterine cavity. A gestation may occur in that part of the Fallo- pian tube which is situated in the uterine wall. Such an one, described under the name " interstitial,^^ would not be " extra- uterine," for it is within the uterus. It would, however, be " ec- METHOD OF FERTILIZATION. 639 topic." If the view of Webster is correct, all ectopic (gestations must be of tubal oriii^in. He divides them into three subdivisions : 1. Ampullar, in which the gestation begins in the ampulla of the tube, and he regards this as by lar the most common. 2. Inter- stitial, in which the gestation develops in the interstitial portion of the tube. 3. Infundibular, in Avhich it begins in the outer end of the tube or in an accessory tube-ending. In the latter class are those commonly described as " tubo-ovarian " and " tubo- FiG. 439.— Sections of the ovum of a rabbit, showiug the formation of the blasto- dermic vesicle : «, h, c, d, are ova in successive stages of development ; sp, zona pel- lucida ; ect, ectomeres, or outer cells; ent, entomcres, or inner cells (E. Van Beneden). abdominal," in whicli the body of the gestation-sac has become adherent to the ovary or abdominal wall. Method of Fertilisation. — In the vitelline membrane of the ova of some animals there is a minute opening, the micropyle, by which a spermatozoon gains access to the interior. Such an opening does not exist in the human ovum. Some histologists have described the vitelline membrane as possessing a porous structure, and it has been suggested that through one of these G40 REPRODUCTIVE ORGANS. pores a spermatozoon might pass. It is by no means established that such pores exist. However, in some way the spermatozoon })asses through the membrane into the protoplasm ; here its tail tlisappears and the head assumes a spherical form, and to it the name of " male pronucleus " is given. The male and female pro- nuclei then unite to produce the fecundation nucleus. After this occurs the ovum consists of a mass of protoplasm with a nucleus, and is spoken of as the " segmentaticm sphere," because it under- goes segmentation. Segmentation. — This consists in the production of two seg- ments by the same process of indirect division which takes place in the germinal vesicle ; these again divide, forming four, and, the same process continuing, the entire ovum is broken up into a mass of spherical cells which, from the resemblance to a mulberry, is named morula. These cells separate into two layers, Avith fluid between them, except at one place where the layers are in con- tact. The blastodermic vesicle is now formed. It is probable that development has reached this stage at about the tenth day, by which time the ovum has entered the uterus. The albuminous secretion of the Fallopian tube serves as pabulum or food to the cells in this process. Formation of Embryo. — The next change which takes place is the formation of three layers from the two just described. They are termed the epibla^st, the mesoblast, and the hypoblast; together they form the blastoderm. The epiblast is most external, in con- tact with the vitelline mem]:)rane, which takes no part in the changes thus f;ir described. It would, periiaps, be too much to say that the embryo is now formed, yet the subsequent changes are but the modification and differentiation of the cells which compose these three layers. The epiblast forms the brain and spinal cord, portions of tlie organs of special sense, and the epidermis, and also takes part in the for- mation of the chorion and amnion. The mesoblast forms the vascular, osseous, and muscular systems, and the endothelium which lines the serous cavities. The hypoblast forms the lungs, the epithelium of the alimentary canal and of the glands which are offshoots from this canal. Tiie membrane \vhich lines the allantois and the yolk-sac is also formed from the hypoblast. The segmentation just described is such as takes place, in tlie human ovum and that of other mammalia. It is a process in which the entire mass of protoplasm undergoes division : such ova are said to be holoblasfic. In the ova of birds and of reptiles only a portion undergoes this segmentation, the rest serv- ing as food. Such ova are mcroblastic. As an illustration of the latter may be mentioned the fowl's oq:(i;, in which the processes of development have been most t]u)roughly studied. In this Qs^^g only a minute portion, the cicatricula, becomes converted into DEVKLOl'MENT OF CHICK. 641 the chick, while the great body of niateriiil nourishes the growing einl)ryo until it leaves the shell and is able to gain its own liveli- hood. As such an embryo is never attached to the parent, it must have within itself, supplemented by what it receives from the air, all the material necessary for its development and maintenance until freed from its enclosing shell, hence the large size of the ovum ; while in the mammal this supply is not necessary, for the attachment to the maternal structures is made at an early period of its history, and from the parent all necessary sustenance is obtained. Inasmuch as development has been so much more thoroughly studied in the hen's egg than in any other, and inasmuch as the processes are in many respects probably the same as in the human ovum, the development of the chick will be described, referring to the principal points of difference as they are reached in the description, giving, however, only a general view of the subject, which is much too extensive and complicated to discuss in any other manner in this connection, and referring our readers for fuller details to monographs on enibrvologv. Development of Chick. — If the shell of a hen's ^^g is broken during the lirst day of its incubation and the blastoderm is examined, it will be seen that there is a clear central portion, the area pellucida, and a portion outside of this, the area opaca, which is much less clear. The embryo forms in the area pellu- cida, and the membranes and structures which are to nourish it form in the area ojuica. On the second day, the area opaca having meanwhile extended, within it are formed red blood-corpuscles and vessels, and during the same time in the area pellucida the heart is formed. These structures arise, as has been stated, from the cells of the mesoblast. At one extremity of the area pellucida a fold forms in the blas- toderm, and, as this is the anterior end, it is called the cephalic fold. A similar fold, the fail fold, forms at the other extremity of the area pellucida. In the same manner lateral folds form on the sides. All these folds, which include the three layers of the blastoderm, ap]>roach one another below, and by so doing form a canal, the emlnyonal sac. This sac is bounded above by the blastoderm, anteriorly by the cephalic fold, posteriorly by the tail fold, and laterally by the lateral folds, while below it is in com- munication with the vitellus. This embryonal sac subsequently becomes divided into two, one division forming the alimentary tract, and the other the body-walls, the umbilicus being the point at which the folds all unite. These folds just described are to be carefully distinguished from the membranes, the amnion, the cho- rion, etc. The folds, as stated, involve the epiblast, the mesoblast, and the hypoblast, while in the formation of the membranes the various layers play different parts. 642 REPR OD UCTI VE ORGANS. Membranes of the i^mbryo. — Amnion. — The mesoblast about the embryo s])lits iuto two laminae, the parietal and the visceral. The parietal (external) joins with the epiblast to form the somatojjleure, from which the amnion and the bodv-walls are developed, while the visceral lamina unites with the hypoblast to JVC PP St. A B Sp. Fig. 440. — Diagrammatic longitudinal section through the axis of an embryo chick: N. C, neural canal; Ch, notochord: D, foregut; F. So. somatopleure ; F.Sp, splanchnopleure ; .Sp, splanchnopleure forming the lower wall of the foregut; lit, heart; pp, pleuroperitoneal cavity; .4m, amniotic fold; ^, epiblast; i', mesoblast; C, hypoblast (Foster and Balfour). form the splanchnopleure. From this structure are developed the walls of the allantois, the yolk-sac, and the alimentary canal. Between the somatopleure and the splanchnopleure is the pleuro- peritoneal cavity, which later is divided by partitions into peri- cardial, pleural, and peritoneal cavities. From the somatopleure folds form which rise above the embryo on all sides, meeting over Fig. 441.— Diagrammatic longitudinal section of a chick on the fourth day: ep, epiblast ; hy, hypoblast ; sm, somatopleure : vm. splanchnopleure ; af, pf, folds of the amnion; pp, pleuroperitoneal cavity; am. cavity of the amnion; ai, allantois; a, position of the future anus; /i, heart : i. intestine; ri. vitelline duct; ys, yolk; s, foregut; m, position of the mouth; me, the mesentery (Allen Thomson). its back and fusing together. These are the amniotic folds. As each fold is double, when they unite two membranes result : the inner, next the embryo, is the amnion, and the outer, toward the vitelline membrane, is the false amnion (Fig. 441). The latter and the vitelline membrane fuse together, forming the chorion. AJJ.A yrois—i'i.A ( 'i:sTA. (; };} The true amnion has opihhi.st lor its inner, and mesoblast for its outer, hiyer, and X\\v. spaee l)et\veen it and the embryo is the amniotie cavity, in wliieh the liquor anniii aceumulates. Yolk-sac. — Tlie yolk-sac is a very important structure in tiic fowl ;ind in birds t^enerally, as it is upon the yolk that the nutri- tion of the embryo ilical arteries. At a later stage of development the character of the allantois dis- appears, except in that ])ortion wdiich is to be included \\ithin the body of the fetus, and which becomes the urinary bladder, and in that portion between the bladder and the umbilicus, which becomes the urachus. Chorion. — This membrane, as already stated, is formed by the union of the vitelline membrane and the false amnion. When first formed, it is smooth, but becomes shaggv bv the growth from it of processes called villi. These villi are at first scattered over the whole exterior of the ovum, but later they are found only at the point of attachment of the ovum to the uterus, where the ])laoenta is to be formed. In these villi are blood-vessels from the fetal vascular system. Placenta. — When the impregnated ovum reaches the cavity of the uterus the mucous membrane of that organ is prepared to receive it, and it finds a lodgement there. Under the stimulus of impregnation the whole mucous membrane becomes thickened, and at the termination of uterogestation the entire mucous membrane of the body is cast off; it is called the (JecirJua vera. Especially marked is this thickening at the point of attachment of the ovum, and to this part the name decidua serotinn is applied (Fig. 442). As a result of this stimulus the mucous membrane increases around the ovum, finally completely enclosing it. This new formation is the decidua reflexa. The villi of the chorion find their way into the depressions of 644 REPRODUCTIVE ORGANS. the decidua serotina, and their walls become atrophied, being finally represented only by epithelial cells covering' the capillary blood- vessels which have come from the allantois. The blood-vessels in the decidua serotina become converted into blood-spaces, sinuses, to which the uterine arteries carry blood, and from which the uterine veins carry the blood away. It will be seen, therefore, that the fetal blood- vessels are surrounded by the maternal blood in the uterine sinuses, the two fluids being separated only by the thin wall of the fetal capillaries, through which the interchanges of oxygen and carbon dioxid take place, and also the passage of the nutri- tious material to supply the growing fetus, and in the reverse direction pass the effete products to be eliminated. The structure which performs all these im- portant offices is the placenta, made up of both maternal and fetal tissues. It seems hardly necessary to say that the blood of the mother and that of the child never come in contact, but are alwavs separated by the walls of the fetal capillaries. At birth the placenta is cast off, and by the contraction of the uterine muscular tissue the mouths of the maternal blood-vessels are closed, and thus hemorrhage is prevented. The blood which escapes during a normal labor is that which was in the sinuses. The functions of the placenta are thus seen to be threefold — nutri- tive, respiratory, and excretory. Circulation in the Embryo. — Vitelline Circulation. — During the earliest ]xirt of human fetal life the contents of the ovum supply the growing embryo with nutrition. This is done by means of vessels which compose the vitelline circulation, but, im- portant as this circulation is in the fowl's egg, it is of very brief duration in the human subject, for the supply of nutritious material is soon exhausted, probably at the sixth week. Placental or Fetal Circulation (Fig. 443). — By the sixth week the placenta is formed and the connection has been made by which the embryo receives its nourishment from the maternal blood. Fig. 442. — Series of diagrams repre- senting the relationship of the decidua to the ovum at different periods. The decidua are colored black, and the ovum is shaded transversely. In 4 and 5 the vascular processes of the chorion are figured. 1, Ovum entering the con- gested mucous membrane of the fundus — decidua serotina; 2, decidua reflexa growing around the ovum ; 3. comple- tion of the decidua around the ovum ; 4, general growth of villi of the chorion ; 5, special growth of villi at placental attachment, and atrophy of the rest (copied from Dalton). CIRCULATION IX TIIK EMlillYO. G45 l^roin this time until l)irtli the fetus (Icik'ikI.s upon tlie placental or fetal eireulation for its nourisliuient and maintenance. The hlooil of the fetus is freed from much of its impurities in the placenta, and there likewise it recieives oxygen and nutritive materials. It returns to the fetus through the umbilical vein, passing to the liver. In tliis organ the current is divided : the R Sub elf Su/ui-toi' Vena Cava - -f VmhiUcu I - Fig. 443. — Diagram of the fetal circulation. greater part joins with the venous blood of the portal vein ; a second portion goes directly into the hepatic circulation ; while a third part goes through the ductus venosus into the a-scending vena cava without passing through the liver. The currents all meet again in the ascending vena cava, here mixing with the blood returning from the lower extremities. The ascending vena cava 646 REPRODUCTIVE ORGANS. discharges its blood into the right auricle of the heart, where, guided In- the Eustachian valve, it is directed into the left auricle through the foramen ovale. From this cavity it passes into the left ventricle, thence into the aorta, which distributes it to the head and upper extremities. It Avill be seen from this description that to these three portions of the body the blood from the placenta is distributed. This blood is not very pure, for it is deteriorated by admixture with the impure blood returning from the lower extremities, with which it mingles in the ascending vena cava; but it is the purest and most nutritious blood the fetus receives, and this accounts for the greater development of the upper portion of the body as compared with the lower, which is so striking a feature in the newborn babe. The blood returns from the head and upper extremities through the descending vena cava to the right auricle, and thence passes into the right ventricle. There is probably always a slight mixing of the currents in the right auricle, that returning from the placenta and that from the descending vena cava, but at first this is very slight ; later, it is doubtless greater. From the right ventricle the blood passes into the pulmonary artery, a very small portion going through the capillaries of the lungs, the larger part passing through the ductus arteriosus into the aorta, passing down this vessel to the common and internal iliacs, from which latter are given off the hypogastric or umbilical arteries by which the blood is conveyed to the placenta. By comparing this description with that of the circulation in the adult the points of difference will be seen. It may be well to note here that there are six principal points of difference be- tween the fetal and the adult circulatory ajiparatus, besides less important ones of size and shape. These points of difference are the presence in the fetal heart of the Eustachian valve and the foramen ovale, in the venous system of the umbilical vein and the ductus venosus, and in the arterial system of the uml^ilical arteries and the ductus arteriosus. Chang-es in the Circulation at Birth. — During intra- uterine life the res]>iratorv center in the medulla is supplied with blood containing sufficient oxygen to prevent any inspiratory im- pulse, and there is therefore during this period no attempt at respiration on the part of the fetus. As soon, however, as the connection between the parent and the child is severed, whether by separation of the placenta or by tying of the umbilical cord, the respiratory center, being no longer supplied with oxygen, sends out impulses to the respiratory muscles, and respiration begins. This mav be hastened or assisted by slap])ing the skin or dashing water upon it, but under ordinary circumstances these measures are not called for. The fact that resi)iration will take place while the fetus is still enclosed in its membranes, without the reflex in- CHANGES L\ THE CIRVVLATION AT BIRTH. 647 riiH'nce of c'xposiiro to the air, shows that tliis is not the essential, but only a contributinij;, cause. Jt is the Ht<>j)page of the placental circulation which starts the respiratory movements. Although durinti- fetal life some blood Hows through the pulmo- nary capillaries, still the amount is small, and, there being no air in the pidmonary alveoli, the lungs will sink if placed in water. The first respiratory movement causes an enlargement of the thoracic cavity and a conse-"< influences retarding, 2o7 theuries, 2>W distribution of, 202 gravity and, 319 inert layer of. :>(I8 internal friction of, 307 lakey. -JGO menstrual, power to clot, 287 microscopic structure of, 262 movements of, in diastole, 303 ill systole, 303 peripheral resistance to, 308 physical properties of, 260 regeneration of, 291 serum, 2*6 specific gravity of, 260 Blood-cells, 278 Blood-corpuscles, 262 colorless, 260. See also Leukocytes. red, 262. See also Red Corpuscles. white. 280. See also Leukocytes. Blood-flow, rate of, 312 Blood-glands. 323 Blood-plasma, 283 enzymes of, 284 extractives of, 284 gases in, 286 inorganic salts in, 283 proteids of, 284 water of, 283 Blood-plates. 283 Blood-pressure. 308 aortic, 310 arterial, 310 measuring of. 310 negative, 311 veuous, 311 Bolus, alimentary, 181 Bone, 41 blood-vessels of, 44 calcium phosphate in, 84 cancellated. 41 chemical composition of, 44 compact. 41 development of, 45 lacunae, 42 lamellae, 42 lymphatic vessels of, 44 nerves of, 44 Bone-corpuscles. 42 Bone-marrow, 43 Bowman's capsule. 411 glands. .519 membrane, 530 Brace, Julia, case of, 523 Brain, 471 columns of, 473 effect of alcohol on, 1.58 gray matter of, 471 pyramids of. 473 weight of. 471 Brain-sand. 340 Bran. 150 Brandy. 153 Bread," 150 Break of current, 435 Bridgman, Laura D., case of, 516 Brigham's case of esophago-duodeuos- tomy, 211 Broca's convolution, 499 Bromelin, 151 Bronciii, :i51 Broiicliial arteries, 353 tube, lobular, 352 veins, 353 Bronchiole, 352 Broth, meat. 149 Bruch's membrane, 532 Brunner's glands, 219 Buffv coat, 287 Bulb, 472 Burdach's column, 462 Cadaveric rigidity, 62, 444 Caffein, 152 Caffeo-tannie acid, 152 Cajal's cells. 539 Calcification. 40 Calcium carbonate, 85 fluorid ill body. 86 phosphate in body, 84 salt in body, 84 Calculi, salivary, 177 Calorie, 398 Calorific rays, 572 Calorimetry. 399 Canaliculi, 42, 581 Cane-sugar, 93 action of gastric juice on, 193 as food, 123 Canines, 55, 166 Capillaries, 300 pulmonary, 3.53 rate of flow in. 313 Carbamid. 421 Carbo-hemoglobin, 273 Carbohydrates, 87 action of gastric juice on, 193 as food, 123 gastric absorption of, 245 glycogen formation from, 248 intestinal absorption of, 247 Carbon dioxid in body, 87 and oxygen interchange. See Oxygen and Carbon Dioxid. tension of, in blood, 373 Carbonates in body, 83. See also Calcium, Sodium, etc. Carbon-monoxid hemoglobin, 272 spectrum of, 278 Cardia, 185 Cardiac cycle. 301 glands, 187 impulse, 305 muscle, 61 composition of, 63 nerves, 513 orifice, 185 portion of stomach, movements of, 197 Cardio-accelerator center, 469 Cardiogram. .302 Cardiograph. 302 Cardio-inhibitory center, 475 652 INDEX. Cardiopueumatic movements, 372 Carotid glaud, 341 Cartilasje, 33 articular, 39 cellular, 41 chemical composition of, 41 costal, 40 hyaline, 38 inorganic solids of. 41 intermediate, 49 organic solids of, 41 transitional, 39 true, 38 white fibrous, 40 vellow elastic, 41 Casein, 112 vegetable, 151 pancreatic, 231 Caseinogen, 109, 112 Casper's cystoscopy 417 Caudate nucleus, 487 Cell stations, 476 Cell-group, middle, 462 Cells, 23 air- 352, 353 amacrine-, 539 bipolar, 70 blood, 278. See also Red Corpuscles and Leuhocytes. bone-forming, 43 central, 187 chief, 187 columnar, 519 connective-tissue, 35 crescentic, 169 daughter-, 609 dentin-forming, 50 division of, 28 fat-, 35 fiber-, of Retzius, 594 giant-, 44 glia-, 73 goblet-, 31 granule, 35 gustatory, 526 hair-, of ear, 599 lamellar, 35 marrow-, 44, 279 mastoid, 589 mother-, 609 mucus-secreting, 32 multipolar, 70 nerve-, 69 neuroglia, 73 of anterior horn, 462 of Cajal, 539 of Deiters', 599 of gray matter of cerebrum, 492 of posterior horn, 462 of Purkinje, 479 olfactory, 519 osyntic, 187 parietal, 187 plasma-, .35 salivary, changes in, 175 spermatogenic, 609 spider-, 73 splenic, 44 Cells, sustentacular, 325, 526, 609 tendon-, 38 unipolar, 70 villi, 218 Cellulose, 98 action of ptyalin on, 178 Cement, tooth, 53 Central canal, 459 cells, 187 lobe, 486 of cerebrum, 485 spindle, 28 vein, 234 Centrifugalization, 262 Centrosome, 25 Centrospliere, 28 Cephalic fold, 641 Cereals as food. 149 Cerebellar ataxy, 480 tracts, 461 Cerebellum, 477 effect of removal of, 480 functions of, 480 gray matter of, 479 impressions of, sources of, 481 inferior peduncles of, 474 laminae of, 477 white matter of, 479 Cerebral localization, 497 Cerebrin, 75 Cerebrosides, 75 Cerebrospinal fluid, 459 Cerebrum, 483 convolutions of, 484 fibers of, 494 fissures of, 483, 484 functions of, 495 gray matter of, 484 microscopy of, 491 gyri of, 484 lobes of, 485 microscopy of, 491 peduncles of, 487 sulci of, 483 vital importance of, 495 white matter of, 493 Cerumen, 406, 583 Charcot's crystals. 614 Chemistry, definition of, 20 physiologic, 21, 76 Cheyne-Stokes respiration, 376 Chick, development of, 641 Chief cells, 187 Cholalic acid, 241 Cholesterin, 101, 242, 258 Choletelin, 240 Cholic acid, 241 Cliondrigen, 115 Chondrin, 41 Chorda tympani, 172 Chordfe tendineae, 297 Choriocapillaris, 532 Chorion, 643 Choroid, .5.32 Chromatin, 25 Chromogen, 337 Chromoplasm, 25 Chronographs, 438 INDEX. 653 Cbylf, 2a-) Cliyinosin, 112 Cilia, 3;{ Ciliary body, 5;5r> giiiiglioii, "jOiS ligament, 532, 534 luotiou, 3:j muscle, 534 processes, 533 Ciliospinal center, 469 Cinoritious matter, 69 Circnilation, 3(11 time reiiuired fur, 314 (Circulatory system, 295 Circulus iridis major, 534 minor, 534 Circum vallate papillaj, 524 Clarke's column, 462 Claustrum, 4b7, 493 Climacteric, 629 Climate, menstruation and, 629 Clitoris, erection of, 635 Coagulated proteid, 10«, 113 Coagulum, 141 Coccygeal gland, 341 Cochlea, 591 canals of, 593, 596 duct of, 593 nerve of, 599 spiral canal of, 592 Cocoa, 153 Coffee, 152 Coffin-lid crystals, 429 Cohnbeim's areas, 57 Cold-blooded animals, 395, 396 Collagen, 115 Colliculus nervi optici, 537 Colloids, 106 Color, 571 diagram, 572 theories, 575, 576 Color-blindness, 577 Colorimetric equivalent, 400 Colors, complementary, 572 physiologic mixture of, 574 Colostrum, 139 Colostrum-corpuscles, 144 Columella, .592 Columnee carnefe, 297 Columnar cells, 519 Columns. Burdach's, 462 Clarke's, 462 Goll's, 461 of brain, 473 spinal, 4.59 Comma tract, 462 Commissural fibers, 494 Commissures, 459 Commutator, 436 Complemental air, 363 Conduction-paths in cord, 465 Cone proper, 541 Cone-bipolars, 539 Cone-elements, 541 Cone-fiber, 541 Cone-foot, 540 Cone-granules, 540 Cones, 540 Conical papilhc, .525 Conjunctiva, .581 Conjunctival reflex, 468 Connective tissue, 34 jelly-like, 38 Consonants, 3H3 Continuous spectrum, 275 Contractile substance, 56 Contractility, 430 Contraction, secondary, 447 suix'rposition of, 441 vermicular, 445 Contraction-remainder, 440 Corium, 402 Cornea, .529 chemistry of, 543 proper, substance of, .530 vascular system of, 5.30 Corneal corpuscle, 530 spaces, 530 Cornicula laryngis, 343 Cornua, 4.59 Corona radiata, 488, 618 Corjwra cavernosa, 614 ([uadrigemina, 489 striata, 487 Corpus albicans, 633 Arantii, 298 callosum, 483 dentatum, 477 luteum, formation of, 633 spongiosum, 614 Corpuscles, bone-, 42 colostrum-, 144 connective-tissue, 35 corneal, 530 Pacinian, 65 salivary, 176 tactile, 65 Vater's, 65 Corresponding points, .570 Cortex, microscopy of, 491 Cortical substance, 484 Corti's membrane, 597, 599 organ, 597, 598 rods, .598 Costal cartilages, 355 Coughing center, 474 Cowper's glands, 420 Cows' milk, 140 Cranial nerves, 501 Creatinin in urine, 426 Cremasteric reflex, 467 Cretinism, 330 Crico-arytenoideus lateralis muscle, 345 posticus muscle, 345 Cricoid cartilage, 343 Cricothyroid muscle, 345 Crista acustica, 594, .596 vestibuli, 591 Crotalin, 114 Crowd-poison, 366 Crura cerebelli, 479 cerebri, 487 Crusta, 487 petrosa, 53 phlogistica, 287 Crystallin, HI, 544 654 INDEX. Crystalline lens, 542 capsule of, 543 chemistry of, 544 Crystalloids, 106 Cubic space iillotment, 370 Cuneiform cartilages, 343 Cupola, 592 Curd, 112, 141 Current of action, 446 of injury, 44(J of rest, 44G Cuticle, 402 Cylindrical glasses, 559 Cystic duct, 236 Cystoscope, 417 Daltonism, 577 Daniell cell, 432 Daughter-cells, 609 Decidua reflexa, 643 serotina, 643 vera, 643 Defecation, 257-259 Degeneration, 461 Deglutition, lSO-185 center, 474 Deiters' cells, 599 phalanges, 599 Demarcation current, 446 Demilunes of Heidenhain, 169 Demours' membrane, 530 Dendrites, 69, 72 Dendrons, 72 Dental follicle, 54 germ, common, 54 lamina, 54 papilla, 54 pulp, 50 sac, 54 Denticulate lamina, 596 Dentin, 50, 51 Dentinal tubuli, 51 Deprez electric signal, 438 Derma, 402 Descemet's membrane, 530 Descending tract, 461 Detrusor urinpe muscle, 418 Deutero-proteoses, 193 Deutoplastic granules, 621 Dextrose, 87 fermentation of, 91 in urine, 427 Diabetes, 251 mellitus, 251, 427 Dialysis, 106 Diapedesis, 280, 282 Diaphragm, 356 iris, .548 Diaster, 30 Diastole, 302 Diastolic sound! 306 Diathesis, hemorrhagic, 288 Dicrotic pulse, 318 wave, 317, 318 Diet, age and, 138 meat, 128 proper, 127 tropical, 134 Diet, vegetable, 128 Diffusible substances, 162 Ditfusion, 104 Digastric muscle, 344 Digestion, 162 apparatus of, 163 bacterial, 244 effect of alcohol on, 155 intestinal, 215 in large intestine, 244 mouth, 161 stomach, 185. See also Stomach Digestion. tryptic, 230 Diplopia, 570 Direct cell division, 28 Disaccharids, 93 Disassimilation, definition of, 25 Discus proligerus, 618 Dispersion, 561 Dispirem, 29 Distance, judgment of, 571 Dobie's line, 58 Dromograph, 313 Dropsy, 295 Drugs, effect on muscle-curve, 444 DuBois-Eeymond key, 433 inductorium, 435 Ductless glands, 323 Ductus auditorius, 597 choledochus, 236 cochlearis, 597 endolymphaticus, 591, 594, 595 Dulong's calorimeter, 399 Duodenal glands, 219 Duodenum, 215 Dysentery from drinking water, 122, 123 Dyspnea, 378 Ear, 582 external, 582 hair-cells of, 599 internal, 591 labyrinth of, 591 middle, 584 ossicles of, 586. See also Ossicles. vestibule of, 591 Ear-stones, 594 Ear-wax, 406, 583 Ebners glands, 525 Ectopia vesica?, 417 Edema, 295 Efferent nerves, 450 vessels, 414 Egg-albumin, 108 Eggs as food, 145 Egg-tubes, 619 Ejaculation, 636 Elastic tissue, 37 Elasticity, definition of, 37 Elastin, 116 Electric keys, 433 phenomena of muscle, 430, 445 signal of Deprez, 438 Electrodes, 433 non-polarizable, 435 Electrotonus, 453 Eleidin, 117 INDEX. G55 Elementary tissues. 23 Kinl)olism, '29"J Embryo, eiirulatioii of, 64-1 formation of, (i4U membranes of, ti I'J Embryologic method of determining course of nerve-fibers, 4G1 Emergency ration. 130 Einnu'tropia, .")r)7 Enuilsification, 101 Emulsion theory of fat-absorptiou, 253 Enamel, .">■'? Enamel-jelly, r)5 Enamel-organ, v>\, 55 Eiiauu'l-prisms, 53 Enamel-pulp, 55 Encephalon, 471 End-iiulbs, t!5 Endoeariliac jiressure, recording of, 303 Endocardium. 295 Endolymph. .'/J;} Endomysium, 58 End-organs, motor, 61, 65 Endosmosis, 105 Endothelium, 30 End-plate, 65 English ration, 130 Enzymes, 117-119 spleen as producer of, 828 Eosinophils, 2~*1 Epiblast, 640 Epicardium, 295 Epidermis, 402 Epiglottis, 343 in deglutition, 182 Epimysium, .58 E|iineurium, 64 Epiphysis cerebri, 340 Epithelium. 30 ciliated, .32 columnar, 31 cubical, 30 cj'lindric, 31 germinal, 31. 615 glandular. 32 pavement. 30 scaly, 30 simple, 34 spheroidal. 32 stratified, 34 trausitional, 34 Epi tympanic recess, 589 Epoiiphoron, 622 Equilibrium, 481-483 Erectile center, 470 Erection, 635 Erythroblasts, 44, 279 Erythrodextrin, il7, 178 Esophageal glands, 183 Esophago-duodeuostomy, 211 Esophago-enteiostomy, 205 Esophagus. 183 Ether, .568 glyceric, 99 Eupnea, 377 Eustachian tube, 296, 588 Excretin, 2.58 Excretoleic acid, 258 Exophthalmic goiter, 330 Exosmusis, 105 Expiration, 360-363 Exi)iratory center, 375 Expireil air, 366 External cajisule, 487 oblique, 360 rectus, 545 functions of, 547 Extrinsic muscles of tongue, 180 Eye, 529 accommodation of, 548, 552 anterior chamber of, 542 appendages of, 581 chemistry of, 543 etTects of facial paralysis on, 510 near-sighted, 558 normal, 557 posterior chamber of, 542 reduced, 550 schematic, 550 tunics of, 529 white of, 529 Eyeball, muscles of, 544 Eyes, convergence of, during accommo- dation, 557 Facial expression, 510 nerve, 509 paralysis, 510 Fallopian tubes, 624 ova in, 628 Falsetto, .382 Far-point, 556, 557 Fasciculi, 58 Fasciculus of Tiirck, 461 Fat-cells, 35 Fatigue of muscles, cause of, 443 Fats, 99 absorption of, 253 action of gastric juice on, 193 as food, 125 course of, from columnar epithelium to lacteals, 255 disposition of, 2.56 gastric absorption of, 247 glycogen formation from, 249 Fatty-acid theory of fat-absorption, 255 Feces, 257 after stomach removal, 208 color of, 2.57 composition of. 258 quantity of. 2.57 reaction of. 258 Fecundation nucleus, 640 Fehling's test for dextrose, 88 Female genital organs, 615 Fenestra oralis. 589 rotunda. 590 Fermentation, 91, 117 Fermentation-test for dextrose, 88 Ferments. 117-119 Ferratin. Schniiedeberg's. 234 Fertilization, 635 method of. 639 Fetus, circulation of, 644 at birth, 646 Fibrils, 57 656 INDEX. Fibrin, 110 Fibriu-ferment, 284 Fibrin-globulin, 285 Fibrinogen, 110, 284 Fibrinoplastin, 110, 289 Fibrocartilage, 40 Fibrous nervous matter, 63 tissue, 38 Field ration, 131 Filiform papillae, 525 Filtration-and-diffusion theory of lymph origin, 293 Filum terminale, 456 First sound, 306 Fission, 28 Fissures of spinal cord, 459 Floor-space, allotment of, 370 Flour, processes of making, 150 Focus, inability to, 502 Focussing, 548 Food, 121 absorption of, 162, 245 definitions of, 154 digestibility of, 129, 203 for soldiers, 130 quantity required, 129 of water in, 79 sodium chlorid in, 81 starch in, 96 Food-stuflfs, 121 composition of, 146 inorganic, absorption of, in stomach, 246 oxidation of, 398 Foramen of Sommerring, 536 ovale, 298 Forebrain, 471 Form, appreciation of, 570 Fossa vesicalis, 236 Fovea centralis, 536 hemi-elliptica, 591 hemispherica. 591 Fracture, green-stick, 84 Franklin color theory, 576 Frauuhofer lines, 276 Frick's spring myograph, 312 F'rontal lobe, 485 Function, definition of, 17 Functions, classification of, 21 Fungiform papillic, 525 Funiculi, 64 Funiculus cuneatus, 473, 474 gracilis, 473, 474 of Rolando, 473, 474 Furfurol, 241 Furfur-aldehyd, 241 Fuscin, 544 Galactose, 88, 92 Gall-bladder, 236 Gamgee's theory of HCl in gastric juice, 190 Ganglia, 72 automatic menstrual, 631 basal, 487 functions of, 490 cerebral, 487 of trigeminus, 508 Ganglia, spinal, 464 function of, 471 Ganglion spirale, 593, 599 Garrison ration, 132 Gartner's duct, 622 Gastric aciditv, intestinal contents and, 208' juice, action of, 193 artificial, 214 germicidal powers of, 191 hydrochloric acid in, 190 mixed with saliva, 189 pepsin in, 192 pepsin-hydrochloric acid in, 192 quantity of 189 rennin in, 192 secretion of alcohol and, 155 nerves, 512 Gastritis glandularis atrophicans, 213 Gelatin, 115 Gelatoses, 194 Gemmation, 28 Geniohyoid muscle, 345 Genital organs, 608 female, 615 male, 609 Genitospinal center, 469 Gerlach's nerve-network, 463 German ration, 130 Germinal epithelium, 615 spots, 622 vesicle, 621, 622 Giant-cells, 44 Gland-pulp, 321 Glaus penis, 614 Glia-cells, 73 Glisson's capsule, 233 Globulicidal action of serum, 292 Globulins, 81, 110, 268 Glossopharyngeal nerve, 377, 511 Glottis, 347, 349 in singing. 384 movements of, 362 Glucoses, 87 Glucosid, 252 Gluteal reflex, 467 Gluten, 150 Glycerids, 99 Glycocoll, 241 Glycogen, 97, 248 action of ptyalin on, 178 Glycogenic theory, 249 Glycosuria, 251 alimentary, 248, 427 from pancreas removal, 233 Gmelin's reaction, 240 Goblet-cell. 31 Goiter, 330 Golgi's organ, 69 Goll's column, 461 Gowers' hemacytometer, 263 hemoglobinomcter, 270 Graafian follicles, 617 bursting of, 627 ova in, 619 Granule-cells, 35 Granuloplasm, 24 INDEX. 657 Gniiic-sufiivr, 87 Uiaves' (liscase, ;?30 (} rave- wax, 9!t (iruvity, circulation anil. 319 (iray coiuiuissurc, -lo'J lil)ers, (>4 matter, 69 nerve-fibers of, 462 of brain, 171 of cerebellum, 479 of cerebrum, 484 microscopy of, 491 (if cord, 461 (iroen-stick fracture, 84 Ground-buiuUe, anterolateral, 461 Gum, animal, 112 Gustatory cells, .526 nerve. "jOo pore, 526 Gyri, 484 operti, 486 Hair-cells of ear, 599 Hairs, 4(16 Hammarsten's blood-coagulation theory, 289 Hamulus, 59;5 Harmonic series, 606 Hasner's valve, 581 Hassal's corpuscles, 336 Haversian canals, 41, 43 Head, motor area of, 499 Hearing, 582 physiology of, 600 theories of, 602 Heart, 295 apex-beat of, 305, 306 impulse of, 305 movements of, 301 papillary muscles of, 297 parietal portion, 295 pause of, 302 septum of, 296 shortening of, 305 sounds, 306 valves of, 297 visceral portion, 295 Heat -rigor. 111 Heat-unit, 397 Heidenhain's demilunes, 169 lymph theory. 293 Heister's valve, 237 Hclicotrema, 593 Heller's test, 426 Helraholtz phakoscope, 555 Hemacvtometer, 263-265 Hematin, 268, 273. 274 hydrochlorid, 273 Hemato-aerometer. 374 Hematoblasts. 283 Hematocrit, 262, 263 Hematoidin, 240, 274 Hematopoiesis, 279 Hematoporphyrin, 274, 420 Hematoscope, 277 Hemin, 273 Hemiplegia, 489 Hemochromogen, 268, 274 42 Hemoglobin, 268 carbon-mono.tid, 272 spectrum of, 278 derivatives of, 272 sjiectia of, 274 nitric-oxid, 273 spectra of, 274, 277 Hemoglobinometer, 268-270 Hemoiihilia, 288 Hemorrhagic diathesis, 288 Hemoscope, 277 Henle's loop, 411 Hensen's line, 57 Hepatic arterv, 234 duct, 235' Hepatin, Zaleski's, 234 Hering color theory, .576 Hermann's hematoscope, 277 Hctero-proteo.se, 193 Hindbrain, 471 Hippuric acid in urine, 426 Histohematins, 274 Histology of body, definition of, 21 Holmgren test, .578 Homoiothermal animals, 396 Horns of cord, 462 Human milk, 139 Humidity, .365 Humor, aqueous, 542 chemistry of, 544 vitreous, 542 chemistry of, 544 Hyaloid membrane, 542 Hyaloplasm, 24 Hydrobilirubin, 240, 420 Hydrochloric acid in body, 87 Hydrogen, 86 sulphuretted, 86 Hydrolysis, 119 Hypermetropia, 558 Hyperpnea, 378 Hypoblast, 640 Hypoglossal nerve, 514 Hypophysis cerebri, 340 Identical points, 570 Iliocostalis muscle, 359 Immunity, 282 Impregnation, 635 method of. 639 Incisors. 53, 166 Inco-ordination, 480 Incus. 587 Indifferent point, 455 Indirect cell-division, 28 Indol, 258 Indoxyl in urine, 427 Induced current, 433 Induction apparatus, 434 Inferior maxillary nerve, 504 oblique, -546 rectus, 545 functions of, .547 Infundihula of lungs, 353 Infundibulum, 624 Inhibition of reflex action, 467 Inoi-gaiiic, definition of, 18 ingredients, 77 658 INDEX. Iiiosit, 93 Insalivation, 167 Inspiration, 361, 363 extraordinary muscles of, 358, 361 forced, 363 muscles of, 358, 361 ordinary, muscles of, 356 Inspiratory center, 375 spasm, 378 Insula, 485, 486, 488 Intensity, 605, 607 Interarytenoid fold, 347 Intercentral nerves, 451 Intercostal muscles, 357 spaces, 354 Interlobular arteries, 414 plexus, 235 rein, 235 , Intermediolateral tract, 462 Internal capsule, 487 medullary lamina, 489 oblique, 360 rectus, 545 functions of, 547 secretion, 324 sphincter, 221 Internodes, 64 Interposed bundle. 69 Interverteliral disks, 354 Intestinal contents, gastric acidity and, 208 digestion, 215 juice, 222 Intestine, large, 'absorption by, 256 digestion in, 244 structure of, 221 small, 215 absorption by, 247 villi of, 216 " Intra-epithelial plexus, 532 Intranuclear network, 25 lutra-ocular images, 567 Intrinsic muscles of tongue, 180 Invertin, 93, 222 Invert-sugar, 92, 93 Involuntary muscle, 61-63 Involution, definition of, 62 lodin in body, 86 test for starch, 96 lodo-thyrin, 329 Iris, 533, 562 arteries of, 534 diaphragm, 548 Iron in body, 86 Irradiation, 561 Irritability, 430 Irritants, 430, 431 Island of Eeil, 485, 486, 488 Iso-electric, definition of, 445 Isomaltose, 95' Isotonic solution, 261 Isthmus of fauces, constrictors of, 181 Ivory of tooth, 51 Jacob's membrane, .540 Jecorin, 234 Jelly-like connective tissue, 38 Judgment, 496 Karvokinksis, 28 Karyoniitosis, 28 Katabolism, 120 definition of, 25 Katacrotic wave, 317 Katelectrotonic current, 454 Katelectrotonus, 455 Kathode, 432 Keratin, 117 Keys, electric, 433 Kidney, 410 blood-vessels of, 413 eli'ects of removal of, 416 function of, 415 nerve-supply of, 414 Kilocalorie, 398 Kilogramdegree, 398 Kinesthetic area, 497, 498 Knee-jerk, 468 Kolliker's membrane, 599 Krause's end-bulbs, 65 membrane, 59 Kymograph, 302 Labium tympanicum, 596 Labyrinth. 591-593 Labyrinthine impressions, 481 Lacrimal apparatus, 581 Lactalbumin, 109 Lacteals, 218 Lactoglobulin, 109, 111 Lactose, 88, 94 in urine, 428 Lactosuria, 428 Lacunse, bone, 42 Lakev blood, 260 Lamellae, 42, 43 Lamina cribrosa, .529 fusca, 529 spiralis, 592 suprachoroidea, 532 vitrea, .5.32 Langlcy's ganglion, 172 Lanolin, 101 Laryngeal nerves, 377, 511 pouch, 348 Laryngoscope, 379 Larynx, ,343 blood-supply of. 349 cartilages of, 343 cavity of, 347 depressors of, .344 elevators of, 344 in singing, 384-395 interior of. 347 muscles of. 344 nerves of. 349 photography of, 383 Latent period, 438 Lateral born, 462 LatiSsimus dorsi, 3.58 Laurent's polarimeter, 89 Lecithin, 101, 242 Legs, motor area of, 499 Legumin, 151 Lens, crystalline, 542. See also Crys- tnllirie. Lenticular nucleus, 487 I}iJ)KX. 669 lAUiki-inia, 'AMO, :{27 Loiikru(liiction of, 327 v;irii'tirs of, 2t Make of current, 434 Mall! genital organs, 609 Malleus, .586 Malpighian cajjsule. 411 (M)rpuscles, 325, 326 Maltodextrin, 97 Maltose, 88, 94 Maly's theory of origin of HCl in gastric juice, 190 Mamma', 142 Mammary glands, 142 Mammilla, 142 Manometer, 310 Marey's cardiograph, 302 Marrow, bone-, 43 embryonic, 49 red, 43 yellow, 43 Marrow-cells, 44, 279 Marsh -gas, 86 Mastication, 166, ,505 Mastoid antrum, ,589 cells, 589 Maxillary nerves, 504 ramjiart, .54 Maximal jiulsation, 311 Mean blood pressure, 310 Meat as food, 147 cooking of, 148 Meatus, auditory, external, 582, 583 internal, 591 urinarius, 419 Meckel's ganglion, 508 Meconium, 258 Medulla oblongata, 472-474 Medullary artery, 44 canal, 43 sheath, 64 s]iac(s. 49 Meibomian glands. 581 Membrana basilaris, 592 flaccida, 586 granulosa, 618 limitans externa, 540 interna, ,538 pupillaris, 534 tectoria, 597, 599 tympani, .584 in hearing, 601 secundaria, ,590 Memory, 496 Meniere's disease, vertigo of, 483 Menopause, 629 Menses, 629 Menstrual ganglia, automatic, 631 Menstruation, 629 and ovulation, relation between, 632 cause of, 631 corpus luteum of, 633 cycle of, 629 Mercurial manometer, 310 Mesoblast, 640 Mesocephalon, 476 Metabolism, 120 660 IXDEX. Metakiuesis, 30 Metheiuoglobin, 273 MetsclmikoflTs phagocytosis theory, ;iS2 Micropyle, 639 Micturitiou, 419 Midbrain, 471 Middle cell-group, 462 Migration of leukocytes, 282 Milk as food, 133 composition of, 146 cows', 140 human, 139 formation of, 143 secretion of, nervous control of, 145 transmission of disease by, 141 Milk-curdling enzyme of pancreatic juice, 231 Milk-sugar, 94 Milk-teeth. 55, 166 Millon's reaction, 103 Mitosis, 28 Mitral valve, 298 Modiolus, 592 central canal of, 592 spiral canal of, 593 Moist chamber, 438 Molars, 55, 166 Monaster, 30 Monosaccharids, 87 Morgagni's ventricle, 348 Morula, 640 Moss-fibers, 480 Mother-cells. 609 Motion, paralysis of, 452 Motor area, 497, 493 end-organs, 61, 65 lingute nerve, 514 oculi. 501 Mouth, absorption in, 246 digestion, 164 effects of facial paralysis on, 510 floor of, ISO Mouth-breathing, 342 Mucinogen, 175 Mucins, 117 Mucin-sugar, 92 Mucous glands, 169 of stomach, 187 secretion of, 176 Mucus-secreting cells, 32 Miiller's fibers, 541 ring muscle, 532, 534 Mumps. 168 Murexid test for uric acid, 423 MusctE volitautes, 567 ^Muscle, blood-vessels of, 61 cardiac, 61, 63 character of, effect on curve, 444 electric phenomena of, 430, 445 fatigue, cause of, 443 involuntary, 61-63 uon-striated. 61 nuclei of, 58 of insects, 58 phenomena, 430 plain. 61 skeletal. 61 striated, 56, 61, 62 Muscle, voluntary, 56 Muscle-clot, 11 Muscle-columns, 57 Muscle-curve, 437, 438, 442 Muscle-nerve preparation, 432 Muscle-i)lasma, 62 Muscles, ocular, 544 Muscle-spindles, 61, 69 Muscle-sugar, 93 Muscular contraction, simple, 438 sense, 517 tissue, 56 tone, 445, 469 Musculi papillares, 297, 305 Musculotouic center, 469 ilydriasis, 502 Mydriatics. 563 Myeloplaques, 44 Myeloplaxes. 44 Mylohyoid muscle, 344 Myo-albumin, 109 Myocardium. 295 Myogen-fibriu, 62 Myogram. 437 Myograph, 437 Frick's spring, 312 Myohematin, 63 Mvopia, .553 Myosin, 62. Ill Myosin-fibrin, 62 Myosinogen. Ill Myotics, 563 Mvtilotoxin. 115 Myxedema, 330 Nails. 406 Nasal duct, ,581 reflex, 468 Nates, 489 Near-point, 552, 556, 557 Near-sightedness, 558 Neck, motor area of, 499 Neck-sweetbread. 335 Negative blood pressure. 311 variation current, 446 Nephrectomy, effects of, 416 Nerve-cells, 69 development of. 73 of spinal cord. 462 Nerve-center, cord as. 466, 468 Nerve-centers of medulla, 474 Nerve-fibers. 63 depressor, 476 development of, 73 Nerve-impulses. 453 Nerves, 449-452 cranial, .501 olfactory, 519 functions of, 521 spinal. 463 functions of. 470 trophic, 507 vasoconstrictor. 476 vasodilator, 476 vasomotor, 450, 475 Nervi erigentes. 615 nervorum, 64 INDEX. 6(jl Nervous functions, 448 sj'steiii. 406 tissue, G;i c'lu'iui.stry of, 74 protcids of, 75 NtMiraxrs, (iit Neuraxoii, 71 Nourilriunia, (i4 Neuroblasts, 73 Neurofjlia, 7"J Neurokeratin, 117 Neuroli'uinia, 64 Neuron, 71, 7o Neuroplasm, 64 Nipple, 142 Nissl's granules, 69 Nitric-oxid henioglobiu, 273 Nitrogen in body, 86 Nitrogenous foods, 126 Nodes of lianvier, 64 Noises, 604 Non-difrnsil)li' substances, 162 Normal salt solution, 81 Nose, 34-2 Nuclear matrix, 2ij membrane, 25 Nucleic acid. 111 Nuclei n, 25 Nucleins, 111 Nucleo-albumins, 112 Nucleohiston, 283 Nucleolus, 25, 621 true, 25 Nucleojiroteids, 111, 112, 286 in urine, 426 poisonous property of, 113 Nucleus, 25 fecundation, 640 Nutrient artery, 44 foramen, 44 Nutritive functions, 162 Oblique muscles, 546 Obliquus externus, 360 internus, 360 Occipital lobe, 486 Ocular muscles, 544 functions of, 547 Odontoblasts, 50 Odontoclasts, 55 CEstrus, 631 Oils as food, 125 gastric absorption of, 247 Old sight, 5.59 Olein, 99 Olfactory bulb, 519 cells, 519 glomeruli, 520 membrane, 518 nerve-fibers, .520 nerves, 519 function of, 521 sulcus, 521 tract, .521 Olivary body, 473 (Oliver's hemacytometer, 265 hemoglobinometer, 269 Omohyoid muscle, 344 Oncometer, .327 Opa(iue bodies, .573 Oplillialniic nerve, .504 Opli t halmoseope, 567 Optic angk', 551 constants, 549 disk, .537 thalami, 489 Optogram, 569 Ora serrata, 535 Orbits, 529 Organ, definition of, 17, 18 of Corti, .597, .598 of Golgi, 69 Organic, definition of, 18 Organs of body, relations between, 448 Os orbiculare, 587 Osmometer, 104 Osmosis, 81, 104 Ossein, 115 Ossicles of ear, 586 ligaments of, 588 muscles of, 588 Ossification, 40, 45 center of, 46 endochondral, 46 intracartilaginous, 46 intramembranous, 46 subperiosteal, 45 Osteoblasts, 43 Osteoclasts, 44, 49 Osteogenic fibers, 46 Ostium abdominale, 624 Otic ganglion, 508 Otoconia, 594 Otoliths, .594 Ova, 622 holoblastic, 640 in Fallo))ian tubes, 628 in Graafian follicles, 619 liberation of, 626 maturation of, 633 meroblastic. 640 nucleolus of, 621 nucleus of, 621, 622 primitive, 619, 621 Ovarian ligament, 615 Ovary, 615 cortex of, 617 medulla of, 617 Overtones, harmonic, 606 Ovula Nabothi, 626 Ovulation, 626 and menstruation, relation between, 632 Oxygen and carbon dioxid, interchange of, between air and blood, 372 between blood and tissues, 375 in lungs, 371 in body, 86 tension of, in blood, 372 Oxyhemoglobin, 268, 271 spectrum of, 277 Oxyntic cells, 187 Oxyphils, 281 Pacinian corpuscles, 65 Pain, sense of, 518 662 INDEX. Palmitin, 99 Pancreas, 223 inuervation of. 231 removal of, 233 secretion of, 226 iuterual, 233 structure of, 223 Pancreatic fistula, 227 juice, 226 emulsifying powers of, 231 enzymes of, 229 milk-curdling enzyme of, 231 secretion of, 232 Papain, 113 Papiilffi. circumvallate, 524 conical, 525 filiform, 525 fungiform, 525 lingual, 524 Papillary muscles, 305 of heart, 297 Paraglobulin, 110 Paralysis, cerebral, 489 of motion, 452, 489 of sensation, 452 Paranucleins, 112 Paraplasm, 24 Parathyroid, 328, 334 Parietal cells, 187 lobe, 486 Parieto-occipital fissure, 485 Paroophoron, 622 Parotid gland, anatomy of, 167 nervous supply of, 171 secretion of, 175 Parotitis, 168 Parovarium, 622 Pars ciliaris retinte, 535, 542 optica retinse, 535 Parturition, center for, 470 Pasteurization, 141 Patellar reflex, 468 Patheticus, .502 Pavilion, 624 Pavy"s glycogenic theory, 250 Pecquet's cistern, 320 Pectoralis major and minor, 359 Peduncular fibers, 494 Pekelharing's blood-coagulation theory, 289 Penis, 614 erection of, 635 Pepsin in gastric juice, 192 Pepsin-hydrochloric acid, 192 Pepsinogen, 192 Peptones, gastric absorption of. 247 gelatin, 194 poisonous property of. 113 Peptonuria, 427 Percussion-wave, 317 Pericardium, 295 Pericementum, 54 Perichondrium, 41 Perilymph-waves. conversion of sound- waves into, 600 Perimysium, 58 Perineurium, 64 Period of vibration, 604 Periosteum, 43 dental, 55 Peripheral resistance, 308 Peristalsis, 445 of esophagus, 183 Perivitelline space, 621 Perspiration, 403 Perspiratory glands, 402 Pettenkofer's test, 241 Peyer's patches, 220 Pfliiger, primary egg-tubes of. 619 Phagocytosis. 282 Phakoscope, Helmholtz, 555 Phalanges, Deiters', 599 Phloridzin, 251 Phlorizin-diabetes, 251 Phonation, 382 laryngoscopic image during, 380 Phosphates, earthy. 86 in body, 82. See also Calcium, Mag- nesium, etc. Phospho-glucoproteids. 112 Phosphorized fat, 101 Phrenic nerves, 377 Physiologic chemistry, 76 ingredients. 76 salt solution, 81 Physiology, animal, 20 branches of, 19 definition of, 17 human, defined, 20 vegetable, 19 Phvtalbumose, 150 Pia'lyn. 230 Piano theory of hearing, 602 Pigeon-breast, 342 Pigmentary layers of retina, 541 Pigments, mixing of, 574 respiratory. 268 retinal, 544 Pineal gland, 340 Pinna, .582 Piotrowski's reaction, 103 Pitch, 3M, 605. 607 Pituitary bodv, 340 Placenta, 643 circulation of, 644 Plantar reflex, 467 Plaques. 283 Plasma. 108 blood, 283. See also Blood-plasma. muscle-, 62 salted, 287 Plasma-cells, 35 Plethvsmograph, 318 Pleura, 351, 354 Pleural cavity, 354 Plexus, intra-epithelial, 532 subepithelial. 532 • Pneumogastric nerve. 511 Pohl's commutator, 436 Poikilothermal animals, 396 Polarimeter, 88 Polariscope, 88 Polarization, 88. 432 Polarizing current, 454 Poles of cells, 70 Polysaccharids, 95 lyuEX. 003 Pomum Adami, 343 Pons Varolii. 4709 Porus opticus, 529, 537 Post-dicrotic wave, 317 Posterior chamber of eye, 542 gray commissure, 459 horn, cells of, 4(i2 intermediate furrow, 459 median fissure, 459 Posterolateral column, 462 fissure, 459 Posteromedian column, 461 Potassium carbonate, 83 chlorid, 84 pho-phate, 82 sulphate, 83 Pre-antral constriction, 194 Predicrotic wave, 317 Pregnancy, abdominal, 637 ampullar. 639 corpus luteum of, 633 ectopic. 63S extra-uterine, 638 infundibular, 639 interstitial. H'i-^. 639 ovarian, 637 tubo-abdomiual. 6.39 tubo-ovariau, 639 Presbyopia. 5.59 Pressure sense. 517 Primary pulse wave. 317 Primitive sheath, 64 Processus ad raedullam. 479 cochleariformis. 588 e cerebello ad testes, 479 Projection-fibers, 493, 494 Pronucleus, female, 634 male, 640 Protagon. 75 Proteids, 102 absorption of, 2.52 action of gastric Juice on, 193 on polarized light, 103 as food, r2.5 classification of. 107 coagulated, 10-;, 113 color-reactions of, 103 crystallization of, 104 glycogen formation from. 249 in urine. 426 non-diflTusibilitv of, 104 of liver, 234 poisonous, 113 precipitation of. 106 vegetable. 151 Protein, 110 Proteoses, poisonous property of, 11.3 primary. 193 secondary. 193 Prothrombin". 234. 236 Protoplasm. 24 Protoplasmic process, 72 Proto-proteose. 193 Pseudonucleins, 112 Pseudonucleoli, 25 Pseu0 number of. 263 spleen and. 327 structure of. 267 Reflex action, 466-469 arc. 467 centers of medulla, 474 time, 467 664 INDEX. Reflexes, deep, 468 iu miiu, 467 superficial, 467 Eegio olfactoria, 518 respiratoria, 518 vestibularis, 518 Eeichert's water calorimeter, 399 Eeil's island, 485, 486, 488 Reissuer's niembraue, 593 Relative humidity, 365 Remak's fibers, 64 Remembrance, 496 Renal arteries, 413, 414 Renuiu, 112 iu gastric juice, 192 Reproduction, 608 organs of, 608. See also Genital Organs. Residual air, 364 Resonance, 380 Resonators, 607 Respiration, 341 apjiaratus of, 342 at birth, 646 blood- changes from, 370 chemistry of, 365 Cheyne-Stokes, 376 eflferent nerves of, 377 female type, 364 frequency of, 364 innervation of, 375-377 internal, 375 laryngoscopic image during, 380 male type, 364 movements of, 361 rhythm of, 375 muscles of, 356 of skin, 408 Respiration-calorimeter, 159 Resi)iratory center, 375, 469 pigment, 268 quotient, 366 Restiform body. 473 Rete mucosum, 402 testis, 611 Reticular lamina. 599 Reticulin, 116 Reticulum. 24 Retiform tissue, 37 Retina. 535, 563 central artery of, 529, 537 chemistry of. 543 circulation in. 566 epithelium of, 540 fatigue of. .578 layers of. 538-541 minute structures of. 538 pigmentary layer of, .541 reflex of, 567 Retinal image. 5.50, .551 Retzius' fiber-cells, 594 Reuniens. canalis, 595 Reverse air, 363 Rheoscope, physiologic, 447 Rhodopsin, 544, .568 Rhomboidei, 3.59 Rhvthmicalitv, 445 Eibs, 354 Ricin, 113 Rigor mortis, 62. Ill, 444 Ring muscle of Miiller, 532, 534 Rima glottidis. 347 Rivinus' ducts, 169 Kod-bipolars, 539 Rod-elements', 540 Rod-fiber, .540 Rod-granules, .540 Rods, 540 Rolandic area. 497, 498 Rolando's fissure, 485 funiculus. 473, 474 Root-fiber, anterior, 73 Roots of spinal nerves, 463 Rope, the, 56b Rosenmiiller's organ, 622 Rotatory power, specific, 91 Rugie of stomach, lft6 Rumination, 474 Rut, 631 Saccharimeteb, 89 Saccharoses, 93 Saccule, 594, 607 Sacculus laryngis, 348 Sacrolumbalis, 359 Saliva, alkalinity of, 176 amylolytic action of, 178 cells of, clianges in, 175 chemical action of, 177 examination of, 176 composition of, 175 corpuscles of, 176 efi'ect of alcohol on secretion of, 155 of nerve-stimulation on, 172 mixed, 176 with gastric juice, 189 ofiices of, 177. 180 properties of. 175 secretion of. 174 taste and, 180 Salivary calculi, 177 glands, anatomy of, 167 secretory nerves of, 171 Salted plasma, 287 Salts as food. 123 excretion of, 415 in body, 80 Santorini's cartilages, 343 Saponification, 100 Sarcolemma, 56 Sarcomeres, 59 Sarcoplasm. 57 Sarcostyles, .57 Sarcous element of muscle, 59 .Sartoli's columns, 609 Seal a media. .593 tympani, 592 vestibuli, 593 Scaleni, 356 Scheincr's experiment. 5.57 Schlatter's case of stomach extirpation, 205 Schmidt's theory of blood-coagulation, 289 Schmiedeberg's ferratin. 234 Schoens theory of accommodation, 556 INDEX. GGO Scliiilzi-'s tests for {ilycofieii, 98 Scliwaun's miclfiiti-.'! J Sflfidtic tiiiiii' of ovc, .")-J'J Sfhat'cuiis {ilauds, -lUo Sebum, 40o Second sound, 306 Sefiini'Utation, ()40 Semen, til.'5 ejaculation of, G36 Semicircular canals, 591, 607 . impressions from, 481 membranous, 596 I)ositions of, 48"J result of injury to, 481 Semilunar valves, 29H Seminiferous tubules, 609 Senile atrophy, 84 Seusutiou, paralysis of, 452 Senses, 515 special, trigeminus and, 506 Sensibility, general, 515 recurrent, 471 tactile, 515 Sensorimotor area, 497, 498 Sensory an^a, 497, 500 fibers, recurrent, 471 Septum, auricular, 298 ventricular, 298 Serous glands, 169 membranes, 322 Serrati muscles, 359, 360 Serum, 108 blood, 286 globulicidal action of, 292 Serum-albumin, 108 Serum-globulin, 110 Sharpey's perforating fibers, 43 Shock, reflex action and, 468 Shrapnell's membrane, 586 Sight, 551 long, 559 old, 559 sense of, 529 Silicon, 86 Singing, resonance chamber in, 384-395 Size, appreciation of, 570 Skatol, 258 Skatoxvl in urine, 427 Skein, 29 Skeletal muscle, 61 Skiascopy, 568 Skin. 402 care of, 408 excretion of, 407 functions of, 407 nerves of. in respiration, 377 protection furnislied by, 407 respiration by, 408 sensation in, 407 temperature and, 408 Smell, sense of. 518 acuteni'ss of. 523 Snake-poison, 113, 114 Soap. 100 emulsification and, 231 theory of fat-absorption, 254 Sodium carbonate, 83 chlorid, HO in osmosis, 81 glycocholate, 241 ]iliosi)liatt\ H2 sulj)hate, 83 taurocholate, 241 Solar si)ectrum, 275, 571 Solitary glands, 220 Solul)le starch, 9(i Solution theories of fat-absorption, 254 Somatopleure, 642 Sommerring's foramen, 536 yellow spot, 536, 541, 564 Sonometer, 606 Sonorous bodies, 600 Sound conduction through skull bones, 602 definition of, 600 Sounds, 604 Sound-waves, 600 Spectro.scope, 275 Spectrum, 275, 571 Speculum, aural, 584 Speech, 378, 382 Speech-center, 499 Spermatoblasts, 609 Spermatogenesis, 609 Spermatozoa, 609 passage of, 637 Sphenopalatine ganglion, 508 Sphincter antri pyloric!, 188 internal, 221 pupillse, 533 pyloricus, 187 movements of, 195 vesicffi, 418 Sphygmograph, 316 Sphygmometer, 311 Spider-cells, 73 Spinal accessory nerve, 513 columns, 459 cord, 456 as nerve-center, 466, 468 conduction-paths in, 465 enlargements of, 456 fissures in, 459 functions of, 465 gray matter of, 461 minute structure of, 460 nerve-cells of, 462 reflex action of, 466 section of, 459 special centers of, 469 tracts of, 461 white substance of, 460 ganglia, 464 functions of, 471 nerves, 4G3 functions of, 470 in respiration, 377 Spiral canal of ear, 592 1 Spirem, 29 Spirits as food, 153 Splanchnopleure, 642 Spleen, 324 contraction and expansion of, 326 corpuscles and, 327, 328 6QQ INDEX. Spleen duriujj; digestion, 326 enzymes and, 328 uric acid and, 328 Splenic artery, 326 cells, 44 pulp, 325 Spongework, 24 Spongioblasts of i-etinal molecular layer, 539 Spongioplasm, 24 Spreading of reliexcs, 466 Staircase curve, 443 Stapedius, 588 Stapes, 587 Starch, 95-97 Starch-grains, 95 Starch-paste, 96 Steapsin, 230 Stearin, 99 Stellar phosphates, 429 Stellate reticulum, 55 Steuson's duct, 168 Stercobilin, 241, 253 Stei'eoscope, 570 Sterilization of milk, 141 Sternohyoid muscle, 344 Sternomastoid, 359 Sternothyroid muscle, 344 Stilling's canal, 542 Stimulation, 432 previous, effect on muscle-curve, 442 Stimuli, 430, 431 protoplasmic, 24 summatiou of, 441 Stomach, 185 absorption in, 246 of alcohol from, 157 changes in. in digestion, 198 digestion, 185, 202 movements of, 194 etfect on food, 199 progressive atrophy of, 213 removal of, 205, 208 rug'tP of, 186 self-digestion of, 202 Stomata, 322 Strabismus, external, 502 Straight tubes, 611 Stratum granulosum, 618 Striae, 56 Striated muscle, 56 Stroma, 533, 617 Stromuhr, 312 .Stylohyoid muscle, 344 ISubcIavius, 360 fSubepithelial plexus, 532 ■ Sublingual gland, 169 I nerve-supply of. 172 I secretion of, 176 ISublobular vein, 235 Submaxillary ganglion, 509 gland, 168 nerve-supply of, 172 secretion of, 175 Subsidiary centers, 375 Substantia cinerca gelatinosa, 460 gelatinosa centralis, 460 lateralis, 460 Succus entcricus, 222 Sucking center, 474 Sudorific center, 469 Sudoriparous glands. 402 Sugar, composition of, 124 Sulci, 483, 484 Sulphates, 83 Sulphuretted hydrogen, 86 Superior intercostal vein, 353 maxillary nerve, 504 oblique, 546 rectus, »45 Supplemental air, 363 Suprarenal capsules, 336-338 Suspensory ligament, 543 Sustentacular cells, 325, 526, 609 Swallowing, 184 Sweat, 403 Sweat-gland, 402 Sweetbread, 335 Sylvius' fissure, 484 Sympathetic nerve, effect of stimulation of, 172 Svnapse, 72 Syntoniu, 109 Svstem, definition of, 19 Systole, 302 Systolic sound, 306 Tail fold of blastoderm, 641 Tapetuui nigrum, 541 Tartar, 177 Taste, facial paralysis and, 510 saliva and, 180 sense of, 523 conditions of, 528 Taste-buds, 525 Taurin, 241 Tea, 152 Tears, 581 Teeth, 50, .55, 166 development of, 54 in mastication, 166 Tegmen, 586 Tegmentum, 487 Telephone theorv of hearing, 603 Temperature, 396, ,397 effect on muscle-curve, 442 regulation of, 401 sense. 517 skin as-regulator, 408 Temporosphenoidal lobe, 486 Tendo Achillis reflex, 468 Tendon reflexes, 468 Tendon-cells, 38 Tenon's capsule, 529 Tension of dissociation, 372 Tensor tvmpani, 588 Testes, 489, 609 Test-meals, 204 Tetanin, 115 Tetanus, 441 secondarv, 447 Theca folliculi, 618 Thein. 1.52 Tliiry-Vella fistula, 222 Thoma-Zeiss hemacytometer, 264 INDEX 667 Tlioracic i-avity, 'i~>l 'riiDrai'ic duct, '-i'M Tliorax, o.")! aspiration of, 'Mi) respiratory muscles of, 35t) Til rout -swfftbrcad, 335 'riiriiiiihiii, :JiSl Tlnouihusiii. 'JiSy Thymus, 33.'> Thyroo-aiititoxiii, 329 Tiiyrt'oproti'ltl, '\'29 Thyro-arytc'iioideus muscle, 346 Thyro-cpiglottidcus muscles, 346 Til V roll j-oid muscle, 344 Thyroid, 328 arteries, 329, 330 cartilage, 343 colloid liquid of, 329 extract, 331 innervation of, 330 internal secretioa of, 331 removal of, 330 treatment, 332 venous plexus, 350 vesicles, 329 Thvroidectomv, 330 Thvro-iodin, 329 Tidal air, 363 wave, 317 Timbre, 382, 605, 607 Tiiiie-uiarkei's, 438 Tissues, elementary, 30 epithelial, 30. See also Epithelium. Tone-color, 605, 607 Tones, 605, 606 Tongue, 180 mucous membrane of, 524 nerves of. 524 Tonus, muscular, 445, 469 Touch, sense of, 515 Toxalbumins, 114 Trachea, 350 Tracheal glands, .350 Trachealis muscle, 350 Transparent bodies, 573 Transversalis, 361 Transverse band, 188 fillers, 494 Trapezius, 358 Travel ration, 131 Trial-meals, 204 Triangularis sterni, 360 Tricuspid valve, 297 Trifacial nerve, 503 Trigeminus, ,503 , anastomosis of, 506 ganglia of, 508 nerve, 377 special senses and, 506 trojjhic influence of, 507 Trii.'onum olfactorium, 521 Trocblearis, 502 Tronimer's test for dextrose, 87 Trojihic centers, 470 Tropical diet, 134 Trunk, motor area of, 499 Trypsin. 229 Tryptic digestion, 230 Tseherning's theory of accommodation, .5.55 Tuberculosis from eating raw meat, 148 Tubular giands, compound, 169 Tubuli lactiferi, 142 urinil'eri, 411 Tunica ay Subscription. Abbott on Transmissible Diseases, second Edition. Revbed. 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Professor of Clinical Medicine in the University of Pennsylvania; Visiting Physician to the Pennsylvania Hospital IT is universally acknowledged that the Germans lead the world in Internal Medicine ; and of all the German works on this subject, Nothnagel's " Ency- clopedia of Special Pathology and Therapeutics" is conceded by scholars to be without question the best System of Medicine in existence. So necessar>- is this book in the study of Internal .Medicine that it comes largely to this country in the original German. In view of these facts, Messrs. \V. B. Saunders & Com- pany have arranged with the publishers to issue at once an authorized edition of this great encyclopedia of medicine in English. For the present a set of some ten or twelve volumes, representing the most practical part of this encyclopedia, and selected with especial thought of the needs of the practical physician, will be published. The volumes will contain the real essence of the entire work, and the purchaser will therefore obtain at less than half the cost the cream of the original. Later the special and more strictly scientific volumes will be offered from time to time. The work will be translated by men possessing thorough knowledge of both English and German, and each volume will be edited by a prominent specialist on the subject to which it is devoted. It will thus be brought thoroughly up to date, and the American edition will be more than a mere translation of the Ger- man ; for, in addition to the matter contained in the original, it will represent the very latest views of the leading' American specialists in the various departments of Internal Medicine. The whole System will be under the editorial super- vision of Dr. Alfred Stengel, who will select the subjects for the American edition, and will choose the editors of the different volumes. Unlike most encyclopedias, the publication of this work will not be extended over a number of years, but five or si.x volumes will be issued during the coming year, and the remainder of the series at the same rate. Moreover, each volume will be revised to the date of its publicatfon by the American editor. This will obviate the objection that has heretofore e.xisted to systems published in a number of volumes, since the subscriber will receive the completed work while the earlier volumes are still fresh. The usual method of publishers, when issuing a work of this kind, has been to compel physicians to take the entire System. This seems to us in many cases to be undesirable. Therefore, in purchasing this encyclopedia, physicians will be given the opportunity of subscribing for the entire System at one time ; but an\- single volume or any number of volumes may be obtained by those who do not desire the complete series. This latter method, while not so profitable to the pub- lisher, offers to the purchaser many advantages which will be appreciated by those who do not care to subscribe for the entire work at one time. This American edition of Nothnagel's Encyclopedia will, without question, form the greatest System of Medicine ever produced, and the publishers feel con- fident that it will meet with general favor in the medical profession. NOTHNAGEL^S ENCYCLOPEDIA VOLUMES JUST ISSUED AND IN PRESS VOLUME I Editor, William Osier, M. D., F. R. C. P. I'to/isicr of Medicine in Johns //o/>k-ins University CONTENTS Typhoid Fever. Hv l)u. II. Curschmann, c'l l.tip^ic. Typhus Fever. By Ur. H. Curschmann, of l.eipsic. Handsome octavo volume of about 600 pages. Just Issued VOLUME VII Editor, John H. Musser, M. D. /'ro/essor 0/ Clinical Medicine, University 0/ Pennsylvania CONTENTS Diseases of the Bronchi. 15y Hk. I". A. Hi.i 1 - MANN, of ixip^ic. Diseases of the Pleura. ]iy Dr. Rosknijach, oMierlin. Pneumonia. lly Dr. E. Aufrecht, of Magdeluirg. VOLUME II Editor, Sir J. W. Moore, B. A., M. D., F.R.C.P.L, of Dublin Pro/essor 0/ Practice 0/ Medicine, Royal College of Surgeons in Ireland CONTENTS Erysipelas and Erysipeloid. By Dr. H.Lr.N- II \K iz, of llauii>uig. Cholera Asiatica and Cholera Nostras. By Dr. K. von I.ii.f.kr- MiJSTKK, ol rubinfjen. Whoooing Cough and Hay Fever. By Dk. (■• Sm kir. of Giessen. Varicella. By Dr. Tii. von JUR- c.ENSEN, of Tiibincren. Variola (including Vaccination). Bv Dr. H. Immermann, of Basle. Handsome octavo volume of over 700 pages. Just Issued VOLUME VIII Editor, Charles G. Stockton, M. D. Pro/essor 0/ Medicine, University 0/ Buffalo CONTENTS Diseases of the Stomach. By Dk. F. Riigei., ul tliesseu. VOLUME IX Editor, Frederick A. Packard, M. D. Physician to the Pennsylvania Hospital and lo the Children's Hospital, Philadelphia CONTENTS Diseases of the Liver. By Drs. H. Quincke ami (;. lliirPK-Sr.YLER, of Kiel. VOLUME m Editor, William P. Northrup, M. D. Pro/essor 0/ Pediatrics, University and Belle-me Medical College CONTENTS Measles. By Dr. T)i. von Jurcensen, of 'iiibinrjen. Scarlet Fever. By the same author. Rotheln. By tlie same author. VOLUME X Editor, Reginald H. Fitz, A.M., M. D. Hcrsey Pro/essor 0/ the Theory and Practice 0/ Physic, Harvard University CONTENTS Diseases of the Pancreas. B.y Dr. T,. Oser, of \ ienna. Diseases of the Suprarenals. r.y I)r. E. Neusser, of \'ieniia. VOLUME VI Editor, Alfred Stengel, M. D. Pro/essor 0/ Clinical Medicine, Uniz'crsity 0/ Pennsyhania CONTENTS Anemia. By Dr. P. Ehri.ich, of Frankfort- on-the-Main, and Dr. A. Lazarus, of Chai- lottenburg. Chlorosis. By Dr. K. von Nookden, of Frankfott-on-the-Main. Dis- eases of the Spleen and Hemorrhagic Diathesis. Bv Iir. M. I.rrri n, of Ikrlin. VOLUMES rV, V, and XI Editors announced later .'oL IV. — Influenza and Dengue. By Dr. O. Leichtenstern, of Cologne. MalarialDis- eases. By Dr. J- Mannaherc, of \ ienna. ■o'- ^ — Tuberculosis and Acute General Miliary Tuberculosis. B.y Dr. (".. d irnic'i , of Berlin. 'ol. XI. — Diseases of the Intestines and Peritoneum. By Dr. 11. IS'othnagel, of \'ienna. 19 CLASSIFIED LIST OF THE MEDICAL PUBLICATIONS or W. B. SAUNDERS O COMPANY ANATOMY, EMBRYOLOGY, HISTOLOGY. Bohm, Davidoff, and Huber— A Text- Book of Histology, Clarkson — A Text- Book of Histology, . . Haynes — A Manual of Anatomy Heisler — A Text-Book of Embryology, . . Leroy — Essentials of Histology Nancrede — Essentials of Anatomy Nancrede — Essentials of Anatomy and Manual of Practical Dissection BACTERIOLOGY. Ball — Essentials of Bacteriology FrotMngbain — Laboratory Guide Gorham — Laboratory Course in Bacteri- ology Leliina,nn and Neumann— Atlas of Bacte- riology, Levy and Klemperer's Clinical Bacter;- ology Mallory and Wriglit — Pathological Tech- nique, McFarland — Pathogenic Bacteria CHARTS, DIET-LISTS, ETC. Griffith— Infant's Weight Chart, Hart — Diet in Sickness and in Healtli, . . Keen — Operation Blank Laine — Temperature Chart Meigs — Feeding in Early Infancy Starr— Diets for Infants and Children, . . Thomas — Diet-Lists CHEMISTRY AND PHYSICS. Brockway— Essentials of Medical Physics, Wolfif — Essentials of Medical Chemistry, . CHILDREN. An American Text-Book of Diseases of Children Griffith— Care of the Baby Griffith- Infant's Weight Chart Meigs — Feeding in Early Infancy, .... Powell — Essentials of Diseases of Children, Starr— Diets for Infants and Children, . . DIAGNOSIS. Cohen and Eshner— Essentials of Diag- nosis Corwin — Physical Diagnosis, Vierordt — Medical Diagnosis DICTIONARIES. The American Illustrated Medical Dic- tionary The American Pocket Medical Dictionary, Morten — Nurses' Dictionary, 13 15 EYE, EAR, NOSE, AND THROAT. 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M. and Therapeutics, 15 Saunders' Pocket Medical Formulary, . . 11 Sayre — Essentials of Pharmacy 15 Sollmann — Text- Book of Pharmacology, . 22 Stevens — Manual of Therapeutics, ... 13 Stoney — Materia Medica for Nurses, . . 13 Thornton — Prescription-Writing 13 20 MEDICAL PUBLICATIONS OF 1 1'. B. SAUNDERS 6- CO. 21 MEDICAL JURISPRUDENCE AND TOXICOLOGY. Chapman — M e d i c a 1 J unspiudcnce and Toxiiold^^v t; Golebiewski and Bailey— Atlas of Dis- ease's Caused by Accidents 17 Hoftnann and Peterson— Atlas of Legal Medicine 16 NERVOUS AND MENTAL DISEASES, ETC. Brower — Manual of Insanity 22 Chapin — Compendium of Insanity, ... 5 Church and Peterson — Nervous and Men- tal Diseases 5 Jakob & Fisher— Atlas of Nervous System, 17 Shaw— Essentials of Nervous Diseases and Insanity 15 NURSING. Davis — Obstetric and Gvnecologic Nursing, 6 Griffith— The Care of the Baby 7 Hart — Diet in Sickness and in Health, . . 7 Meigs — Feeding in Early Infincy JUorten — Nurses' Dictionary, . . Stoney — Materia Medica for Nurses, . . 13 Stoney — Practical Points in Nursing, ... 13 Stoney — Surgical Technic for Nurses, . . 13 Watson — Handbook for Nurses 14 OBSTETRICS. An American Text-Book of Obstetrics Ashton — Essentials of Obstetrics, Boislini6re — Obstetric Accidents, .... 4 Borland — Modern Obstetrics 6 Hirst — Te.xt-Book of Obstetrics, Norris — Syllabus of Obstetrics, Schaeffer and Edgar — Atlas of Obstetri- cal Diagnosis and Treatment, 17 PATHOLOGY. An American Text-Book of Pathology, . 2 Diirck and Hektoen — Atlas of Pathologic Histology 16 Kalteyer — Essentials of Pathology, ... 15 Mallory and Wright — Pathological Tech- nique 9 Senn — Pathology and Surgical Treatment of Tumors 12 Stengel — Text-Book of Pathology, ... 12 Warren — Surgical Pathology and Thera- peutics 14 PHYSIOLOGY. An American Text-Book of Physiology, 2 Budgett — Essentials of Physiology, ... 15 Raymond — Te.xt-Book of Physiology, . . 11 Stewart— Manual of Physiology, .... 13 PRACTICE OF MEDIQNE. An American Year-Book of Medicine and Surgery 3 Anders — Practice of Medicine 4 Eichhorst — Practice of Medicine 6 Lockwood — Manual of the Practice of Medicine, 9 Morris — Ess. of Practice of Medicine, . . 15 Salinger and Kalteyer — Modern Medi- cine II Stevens — Manual of Practice of Medicine, i ^ SKIN AND VENEREAL. An American Text-Book of Genito- urinary and ."^kin Diseases 2 Hyde and Montgomery— Syphilis and the \'i'nereal 1 )iseases g Martin — ICsscntials of Minor Surgery, Bandaging, and Venereal Diseases, . . 15 Mracek and Stelwagon— Atlas of Diseases of the Skin 16 Stelwagon— Essentials of Diseases of the Skin 15 SURGERY. An American Text-Book of Surgery, . . 2 An American Year-Book of Medicine and Surgery 3 Beck — Fractures 4 Beck — Manual of Surgical Asepsis, ... 4 Da Costa — .Manual of Surgery 5 International Text-Book of Surgery, . . 8 Keen— Operation Blank 8 Keen — The Surgical Complications and Sequels of Typhoid Fever 8 Macdonald — Surgical Diagnosis and Treat- ment 9 Martin — Essentials of Minor Surgery, Bandaging, and Venereal Diseases, . . 15 Martin— Essentials of Surgery, .._... 15 Moore — Orthopedic Surgery, ...'... 10 Nancrede — Principles of Surgery 10 Pye — Bandaging and Surgical Dressing, . 11 Scudder — Treatment of Fractures, ... 12 Senn — Genito-Urinary Tuberculosis, ... 12 Senn — Practical Surgery 12 Senn — Syllabus of Surgery 12 Senn — Pathology and Surgical Treatment of Tumors 12 Warren — Surgical Pathology and Thera- peutics 14 Zuckerkandl and Da Costa — Atlas of Operative Surgery 16 URINE AND URINARY DISEASES. Ogden — Clinical E.xaminadon of the Urine, 10 Saundhy — Renal and Urinary Diseases, . 11 Wolff — Handbook of Urine-E.xamina- tion ... 22 Wolfif — Essentials of E.xamination of Urine, 15 MISCELLANEOUS. Bastin — Laboratorx- E.xercises in Botany, . 4 Golebiewski and Bailey — Atlas of Dis- eases Caused b\ Accidents 17 Gould and Pyle — Anomalies and Curiosi- ties of Medicine 7 Grafstrom — Massage 7 Keating — How to Examine for Life Insur- ance 8 Saunders' Medical Hand-Atlases, . . 16,17 Saunders' Pocket Medical Formulary, . . 11 Saunders' Question-Compends, . . . 14,15 Stewart and Lawrence — Essentials of Medical Electricitv 15 Thornton — Dose-Book and Manual of Prescription-Writing 13 Van Valzah and Nisbet — Diseases of the Stomach 13 THE LATEST BOOKS. Bergey's Principles of Hygiene. The Principles of Hygiene : A Practical Manual for Students, Physicians, and Health Officers. By D. H. Bergev, A. M., M. D., First Assistant, Laboratory of Hygiene, University of Pennsyl- vania. Handsome octavo volume of about 500 pages, illustrated. Brewer's Manual of Insanity. A Practical Manual of Insanity. By Daniel R. Brower, M. D., Professor of Nervous and Mental Diseases, Rush Medical College, Chicago. i2mo volume of 425 pages, illustrated. Gorham*s Bacteriology. A Laboratory Course in Bacteriology. By F. P. Gorh.\m, M. A., Assistant Professor in Biology, Brown University. i2mo volume of about 160 pages, handsomely illustrated. Gradle on the Nose, Throat, and Ear. Diseases of the Nose, Throat, and I^ar. By Henry Gradle, M. D., Professor of Ophthalmolog}' and Otolog\', Northwestern University Medical School, Chicago. Handsome octavo volume of 800 pages, profusely illustrated. Sollmann's Pharmacology. A Text-Book of Pharmacology. By Torald Sollmann, M. D., Lecturer on Pharmacology, Western Reserve University, Cleve- land, Ohio. Royal octavo volume of about 700 pages. Wolfs Examination of Urine. A Handbook of Physiologic Chemistry and Urine Examination. By Ciias. G. L. Wolf, M.D., Instructor in Physiologic Chemistry, Cornell University Medical College. i2mo volume of about 160 pages. -v'^