COLUMBIA UBRABIES OFFSITE HI A! 'M s.il H( I S SIANOAMI) HX64098508 QP40 .G93 Ptiysiology A manual atome Series RECAP PHYSIOLOGY GUENTHEPv ^v^r) ^:33 Columbia (MnttJmitp intljeCitpoflmgork CoQege of ^ffv^imni anli ^urseonsi Hihrarp Digitized by the Internet Archive in 2010 with funding from Columbia University Libraries http://www.archive.org/details/physiologymanualOOguen Zhc HDcbical Epitome Scries. PHYSIO LOCIY. A MANUAL FUR STUDENTS AND PRACTITIONERS. THEODORE C. GUENTHEK, M.D., Asuislanl Phi/sician, Norwcffinn Hospital, Brooklyn: ChitJ' of MedU'al Clinic, Sorwegian Hospital Dispenmry : Member of Kino's County Medical Society. AUGUSTUS E. CtUENTHER, B.S., Formerly Assistant in Physiology id the Meilirnl PepartmenI, University of Michigan. SERIES EDITED BY V. C. PEDERSEN, A. M.. 31. D., Clinical .{ssistnnt in Surgery at the Sew York Polyclinic Medical School and Hosjiilal ; Deputy Gcnito-Uriunry Surgcan to the Out-Paticnt Departmnti of the Xcw York Hospi- tal; Physiciitn-in-Charge, .s7. Chrysostoin' s Dispeimiry ; Recently Assistant Demou- ttrator of .1 natomy at the College of Physicians and Surgeons, Columbia I'ni- versity in the City of Sew York: Assi.itant .'^urgcon to the Out-Patiait De- partmctU of the Roosevelt Hospital and to the Vanderbilt Clinic, etc. ILLUSTRATED WITH FIFTY-SEVEN ENGRAVINGS. LEA BRD'IHKIJS ,^- CO.. PHILADELl'lII A AND X K W YoIJK:, 0^74-0 &^3 Entered according to Act of Congress, in the year 1903, by LEA BROTHERS & CO., In the Office of the Librarian of Congress. All rights reserved. ELECTROTYPED BV PRESS OF VESTCOTT &. THOMSON, PHILADA, WM. J. DORNAN, PHILADA. AUTHORS' PREFACE. It has been the aim of the authors in the preparation of the present volume to gather together those facts of Physi- ology with which medical students and practitioners should be fannliar. It is not the intention to produce a work which shall take the place of more elaborate text-books, but to f^ supplement them by covering the essential features of the ^ subject. Theodore C. Guenther, M. D. J Augustus E. Guenther, B. S. o New Yokk, 1903. J^ 3 EDITOR'S rilEFACE. In arrnngiiii!; for the cditorsliij) of The Medical Epitome Series the publishers (■st:il)li>lH'(l a few simple conditions, namely, that the Series as a whole shoiihl emhraee the entire realm of medicine; that the individnal volnnics shonld authoritatively cover their respective subjects in all essentials; and that the maximum amount of information, in letter-press and engravings, should be given for a mini- mum price. It was the belief of publishers and editor alike that brief works of high character would render valuable service not only to students, but also to practi- tioners who might wish to refresh or supplement their knowledge to date. To the authors the editor extends his heartiest thanks for their excellent work. They have fully justified his choice in inviting them to undertake a kind of literary task which is always ditHcidt — namely, the combination of brevity, clear- ness, and eom})rehensiveness. They have equalled the con- scientious efforts with which the editor has performed his duties from first to last. Co-operation of this kind ought to result in useful books, in brief manuals as contradistin- guished from mere eompends. In order to render the volumes suitable for quizzing, and yet ])r('serve the ('(mtinuitv of the text unbroken, the ques- tions have been gatluTcd at the end of eacli chapter. This new arrangement, it is hoped, will be convenient alike to students and j)ractitioners. Yktor C. Pedersen. New York, 1903. 5 CONTENTS. CFI AFTER I. PAGES General Introduction 17-34 I*hysiolih;y and IIiman Physiology: Fundamental Proper- tie* of Living Tliing8 17-19 Celi^: Their Histological Differentiation and Structure ; Tlieir Essential Part.s; Tiioir Reproduction ; Their Origin ; Their Properties; Their Death 19-33 The Okujix ok Lifk 33 Somatic Death 33-34 CHAFfER II. Secretion 35-56 Salivary Glands 35-38 Stomach 38-39 Pancreas 39-40 LiVKR 40 Intestinal Olaxds 41 Serous Secretions 41 Lachry'mal Glands 41 Kidney and Urine 41-47 Skin 47-18 Mammary Glands 48-50 Thyroid . . . / 50-51 Pancreas 51-52 Si rKARKN.vL Capsules (Adrenal Bodies) 52 Pituitary Body 52-53 Testis and Ovary 53 Thymus (Jland ani> Spleen 53-5t; 8 CONTENTS. CHAPTER III. PAGES Digestion 66-71 The Peoteids 56 The Albuminoids 57 The CARBOHYDRA.TES • 57-58 Water and Salts 58 Oxygen 58-59 The Salivary Secretion 60 The Gastric Juice 61-62 The Pancreatic Juice 62-63 The Bile 63-64 The Intestinal Secretion 64 The Secretion of the Large Intestine 64-65 Summary of Digestion : Proteids ; Albuminoids ; Carbohy- drates ; Fats 65-67 The Self-digestion of the Stomach 67-71 CHAPTER IV. Muscular Mechanisms 71-80 Mastication 71 Deglutition . 71-72 The Movements of the Stomach and Vomiting 72-73 The Movements of the Intestines 73-74 Defecation 75 Micturition 75-76 Parturition 76-77 The Locomotor Mechanisms 77-78 The Voice 78-80 CHAPTER V. Absorption ■ 80-83 General Principles 80-81 Absorption from the Stomach 81 Absorption from the Small Intestine 81-82 Absorption from the Large Intestine 82-83 coxrhwrs. 9 C'llAlTKR VI. PAGFs Metabolism K:i-!tl TuK KNEKtiY OF Imiod: I'rottids ; All)iiiiiin<)i(ls ; Carholiydnitcs; Fat.s; Water; Salts S4-X;t TiiK 1)i;ti;i!M1nati()N of Mftaiiomsm .S<.)-'.)I cnAI'TKIl Nil. The Blood and Lymph 91-1U4 TnK Blooij : The ('<)ri)ii.scle.s; Ilieinoglobin ; The Pla.sma ; Combined Proteids; P^.\tr.ictives ; Inorgjinic Salts; Coag- ulation or Clotting 01-102 The Lymph 102-104 CHAPTER VIII. The Circulation 104-13:^ TuK llEAin- 104-121 The Arteriios, Capill.\.rii->, and Veins 121-127 The PrLMoN.\.RV CiRcrL.VTiox 127-130 The Circllation of Lymph 130-133 CHAPTER IX. Respiration 133-147 The Mechanical, Physical, Cikculatory, and Nervous Factors 133-14o Modified Ri>piration: Sighing; Ilicenngh ; Cough ; Sneez- ing ; Speaking ; Singing ; Sniffing ; Sobbing ; Laughing ; Yawning ; Sucking 145-147 CHAPTER X. Animal Heat 148-152 CHAPTER XI. Nerve and Muscle 152-169 Irritapility, Conductivity, and Nutrition 152-153 The Independent Contractility of Muscle 153-154 10 CONTENTS. PAGES Irritatation of Nerve and Muscle : Mechanical ; Ther- mal ; Chemical ; Physiological ; Electrical 154-157 Degeneration of Nerve and Muscle : Anodic Closing Contraction ; Cathodic Closing Contraction ; Anodic Open- ing Contraction ; Cathodic Opening Contraction .... 157-158 Muscle Fatigue and Tetanus 159-164 The Energy of Muscle Contraction 165 The Electrical Currents of Muscle and Nerve ; Sec- ondary Tetanus 165-169 CHAPTER XII. The Central Nervous System 169-205 The Structure of the Nervous System 169-173 Reflex Acts 173-178 Voluntary Acts 178-180 Paralyses and Degenerations 180-181 Areas of the Cerebral Cortex 181-184 The Function of Other Parts of the Encephalon : Cerebellum ; Thalamus Opticus ; Corpora Quadrigemina ; Medulla 184-188 The Cranial Nerves : Olfactory ; Optic ; Motor Oculi ; Patheticus ; Trigeminus ; Abducens ; Facial ; Cochlear ; Glossopharyngeal ; Vagus ; Spinal Accessory ; Hypo- glossal 188-193 The Weight and Growth of the Brain 193-196 The Fatigue of the Brain 196-197 The Blood-supply of the Brain 197 Sleep 198 Hibernation 199 Hypnotism 199 The Knee-jerk 199-200 The Time Involved in Nervous Processes ...... 201-202 The Nerve-centres 202-205 CHAPTER Xin. The Special Senses 206-229 Sight : Emmetropia ; Hypei-metropia ; Myopia ; Diplopia . 206-219 <.'n.\r/:.\Ts. 11 PAOKH IlKARiNn 219-221 TnK Sknsk of K Common Sknsation 220-229 CIIAITEK XIV. Reproduction 229-239 APPENDIX. The Chemical Tests of Physiological Analysis 241 The Metric System of Units and their Equivalents . . 242 Comparative Scales 243 PHYSIOLOGY. CHAPTER L GENERAL INTRODUCTION. Physiology is the science that treats of the phenomeua of normal living matter. As living matter may be either of animals or of plants, so there is a separation of physiology into corresponding divisions — animal and vegetal)! e. Human physiology consists of those facts of animal physiology which have been derived from experiments upon human beings, together with much that has been ascertained for closely allied animals and can be inferred to hold true for man. The chemistry of living things is now a distinct science, — physiolo'j^ci and ^ytyo^, is synonymous etymologi- cally in its broadest application and acceptation with natural phi- losophij, and the earliest physiological conceptions were formed in prehistoric times, inseparable as such from the general mass of knowledge which during the course of later centuries grew into theological, scientific, philosophical, and other aggregations of ideas. The science of physiology as it exists to-day has been gradually evolved out of the joint labors of thousands and thousands of workers. Of these, there are some that stand preeminent and mark in a way the principal epochs in the history of the subject. In the earliest times among the philosophers who dealt with prob- lems that are now physiological may be mentioned Empecheles, Hippocrates, H'^racleitu.^ and particularly Arifitntle (884-322 b. c.\ Galpn (131 to about 200 a. d.) distinctly recognized the nature and importance of physiology. His system of medicine, from which the physiology of the time is inseparable, held an almost 2— Phvs. 17 18 GENERAL INTRODUCTION. indisputable sway for nearly thirteen centuries. Harvey (1578- 1657 A. D.), whose name stands foremost among those of his time, discovered the circulation of the blood. His greatest accomplish- ment was the establishment of the experimental method in physi- ology upon a firm basis. With him originated the conception " omne vivum ex ovo." Haller (1708-1777 A. d.) was the first to recognize the necessity of bringing together the mass of physiolog- ical facts and theories that had arisen during the sixteenth and seventeenth centuries into an independent science. This he did in his Elementa Physiologice Corporis Humani. Johannes Midler (1801-1858 A. D.) was perhaps the greatest physiologist of all times. He impressed upon his science the general form or aspect that it wears to-day. The aim of physiology is the investigation of life. The term life is, however, not readily definable. In general, any given piece of matter is said to be alive when it manifests ihQ fundor mental properties of living things. These properties may be de- fined as follows : 1. Irritability is that property of protoplasm which enables it to undergo characteristic physical and chemical changes when acted upon by certain influences called stimuli. Usually there is a liberation of energy in the response out of all proportion to the energy applied in the stimulus. 2. Conductivity is that property of protoplasm by virtue of which a condition of activity aroused in one portion of the sub- stance may be transmitted to any other portion. 3. Contractility is that property of protoplasm which enables it to change its form when irritated by stimuli. 4. Nutrition is that property of protoplasm which enables it to convert dead food material into its own living substance. 5. Reproduction is that property of protoplasm which enables it to separate into a number of parts, each of which may develop into the parent form. None of the fundamental properties serve absolutely to distinguish living from dead matter, since all are simulated more or less completely by phenomena in the non-living world. Life is always associated with a peculiar form of matter called protoplasm, and is never found elsewhere. Protoplasm has therefore been called the "physical basis of life." It may be defined as the active substance of which living things GESERAL ISTRODUCTION. 19 are composed. It is usimlly colorless, st'niiriuid or gelatinous in coii.«ii:»teiu'y, of greater retractive |K)\ver than water, and granular in apj)earance. Consi:>ting largely of water, it neverthele.-?!! dot's nut mix with water a.< long as it i.s living. \\^ .specific gravity is greater than 1 i paraniM'ciurn, 1.2")), hut varies in many organisms hv the formation and disapin^arance of vacuoles. The jiuitl initnrt' of protoplasm is shown — 1. By the streaming phenomena in plant-colls and in the pseu- dojKnJia of rhizojxxls. '2. By its formation into spherical masses whenever it is freed from its cvU-walls. o. By the assumption of a spherical form hv Huids when iml)edded in a mass of protoplasm. Granules and all for- eign suhstauces lie in a ijroiind gub^tance, which at times is per- fectly homogeneous, but usually has a structure resembling a network. Of the many attempts to explain the Ji if er drncture of proto- plasm, that of Biitschli is the most successful. According to this investigator, protoplasm is an emulsion, the vacuoles or globules of which, through mutual pressure, according to well-known math- ematii'al principles, give rise to the appearance of a network. The granules, etc., never lie within the vacuoles, but always between them. Biitschli has imitated in every detail the appear- ance of protoplasm by artificial emulsions. These were prepared bv mixing intimatelv cane-sugar or jxjtassium carbonate with old oiive oil. A minute quantity of the mixture, placed in a drop of water under the microsco|>e. showed not only all the peculiarities of the pr ., it does not consist of a definite chemical comjxnind, but of the Ig, Ca, and Fe— are all of low atomic weight. Protoplasm with very few exceptions is divided into microscopical massi»s, each of which jx^si^esses one or more ditTerentitited portions culled a ?*•. Such a mass with its nucleus is a cell. .\ cell may be defined as the elementary unit of all organisms, no matter how simple or 20 GENERAL INTRODUCTION. how complicated they may be. Every organism begins its indi- vidual history as a cell separated from a preexisting organism. From time to time this cell (ovum, spore, etc.) divides itself into two or more parts, each of which in due time divides again, the resulting divisions in every case forming complete cells. In the protozoa the daughter-cells separate, and each leads an independent existence, but in many-celled animals they remain connected and become dependent upon one another. A histological differentiation takes place as the animal develops, so that they form groups of cells which are totally different in appearance, and results in tissue- and organ-formation. They take on different functions, p)(^^^ i^assw, and one group of cells will perform a certain work for the good of the entire economy. They thus lose their individuality and become dependent upon one another. This is known as the j^hysiological division of labor. The exact molecular structure of living matter is unknown, but there is no doubt that it is of very great complexity. It dif- fers from dead protoplasm in its unstable, labile nature, reacting to an enormous number of substances which are indifferent to dead protoplasm. It manifests a continual tendency to undergo changes, while dead protoplasm, if protected from external agen- cies, can be kept indefinitely. The nitrogen-containing oxidation products derived from the two are radically different. Those from living matter — uric acid, creatin, adenin, xanthin, guanin, etc. — are all characterized by the possession of the cyanogen group, CN. This group is one of great internal energy, so that compounds containing it have a marked tendency to undergo dissociation. This is especially the case in the presence of oxygen. It is a well- known fact that cyanogen compounds also have the jjroperty of polijmerization — that is, of combining with compounds having a structure like their own, so as to form more complex combinations. By this process they become less and less stable, until the insta- bility reaches its acme by the introduction of oxygen, when the compound undergoes a breaking-down process resulting in the formation of simpler, more stable, bodies. The act of dissociation liberates energy, which appears in the manifestations of life. Pfliiger has suggested that in the change from living to dead pro- toplasm the cyanogen grouping is converted to the inert ammonia grouping by the absorption of water. It is convenient to designate. GENERAL INTRODUCTION. 21 the exju-ef^siou, mass of liviiij; matter, hy the shorter terms hliii/t'ii or hiujjluiiin. Bij biixjcn m itndrrdood the umallcd qiiunt'dy oj /ivlmj matter that can manifest the property of nutrition. That part of nutrition desi}^Miated as metabolism is the most charaeteristic of all the properties of living matter. By it is meant the total series of changes hy which siihstanees are huilt uj) into living matter {(iiKiho/i^'^in ) and again broken down ( kutdbolixiii ). Anaholism and kataholism have op[)osite elfects on living matter, hut they, nevertheless, go on simultaneously in the same cell, and under normal conditions are always active. When they ei eqnih'hrliim. When the stimtilus is re- moved, anabolic processes are lessened, and therefore increa.*«ed kataholism now decreases also ; but kataholism, although decreas- ing, is in excess, and its reaction tends to increase anabolic proc- eisses until both are in equilibrium. There is thus an internal self-ad}}ist)nent of metabolism in living matter. It must be borne in mind that metabolism is probably not limited to the building-up and breakintr-down of the bio: (I, Miitlur-skiin >taf;o : '>. aster stage; c and d, mignuion of chromosomes ; ( , liiustrr .stu;;f ; /, (liiiij^'hlcr-i-olls. 26 qenehal introduction. which they group themselves to form the daughter-wreaths or dias- ter stage. The cytoplasm, while the above changes are taking place, has become constricted by a marked furrow running about the cell in a plane at right angles to the long axis of the spindle. The gradual deepening of the furrow separates the cell into two parts. During this time each of the daughter-wreaths undergoes retrogressive changes leading to the formation of ordinary resting nuclei. The connecting filaments of the spindle and the polar radiations disappear. The chromatic threads lengthen and be- come loosely coiled together ; a nuclear membrane is reformed, and nucleoli make their appearance. Sexual reproduction, or gamogenesis, is the most wide-spread form. When it occurs in unicellular organisms, it is known as conjugation. Two individuals, paramoecia for example, assume positions parallel to each other, and a fusion of their protoplasm takes place at their oral openings. Ciliates have two kinds of nuclei — a macro- and a micro-nucleus. The former degenerates in each individual, but the latter divides twice in succession. Three of the resulting daughter-nuclei go to. pieces, but the fourth divides once more, thus forming two nuclei for each cell. Now, one of each pair of the nuclei migrates into the other cell through the bridge of connecting protoplasm, and fuses with the nucleus which has remained there. The combination-nucleus now divides twice in succession, while the cells separate from each other and divide also. Each daughter-cell has two nuclei which grow into the macro- and the micro-nucleus. In the higher animals reproduction is more specialized. There exist two kinds of sexes, male and female, each of which consists of two groups of cells — somatic cells and germ cells. The latter serve for reproduction, while the former serve all the other func- tions of the body. The male and female germ-cells differ, the former being small and active, while the latter are comparatively large and passive. The fusion of their nuclei is the essential part of reproduction and is known as fertilization. In some metazoa the germ-cells of the female may undergo development without fertilization, which is known as parthenogenesis. The significance of fertilization has been much discussed. There are several views : 1. That it rejuvenates the protoplasm, renewing its power to divide asexual ly. GKSKHAl. ISTllohrcTlnS. 27 2. That roprodiK'tioM prcvciit.s variation ami preserves the uiii- f'orinity ot" tlie racv. .'{. That by iVt'sh coinbinatioii.s it Lfives rise to variations. The living matter of the fertilized ovum is acted upon by two forces — heredity, wliich preserves its characteristics, and athiptn- tioii, which changes tliem. Heredity includes the transmission of both actual and jniteiiiial characteristics from [nirents to oH'spring. The resemblance is most complete between child and parent, and tiiminishes directly backward along the ancestral line. The re- send)lances may be inKitmnica/, j>lnj,siol()(/lca/, or jtxijelto/tjtjica/, or all three variously combined and related. Characters that d(j not appear in the jjarent, but are transmitted from grandparent to child, are called latent and give rise to atavimn or neersioit. Tkia occurs mod often when two strains are crossed ; thus half-castes are usually more degraded than either their civilized or savarje parent. The inheritance of (ic^n/rer/ rharacter.'< is a problem that has not yet been solved. It cannot be denied to exist in unicellular oriranisms, where the protoplasm of the parent becomes directly that of the offspring. In the human being, cases of transmissal of acquired characters can be explained otherwise. However, germinal infections of syphilis can take place through the ovum or spermatozoon. Intra-uterine infections of typhoid, scarlatina, endocarditis, small-pox, measles, croui)()Us pneumonia, and anthrax have been okserved to take place, but these are not comparable to a modification of the germ-plasm through heredity in the ordi- nary sense. The basis of heredity lies undoulitedly in the substance of the germ-cells. Home biologiists maintain that the chromatic is the sole germinal substance. Others regard both protoplasm and nuclear matter as essential, since the characteristics of every cell depend upon its metabolism, and this in turn depends upon the integrity of protoplasm and nuclear matter. Whatever the basis is, it may be designated as rjmn-jidisni. The origin of germ-plasm is ex])lained by two views: 1. It may arise from small particles, r/cnuuuli's ('' lift/r (/rrm-':'' ), given off from the various cells of the body ami collected into germ-cells. 2. It may not be formed in the body, but bi- siinplv transmitted from generation to generation, an iicnition. Kxamples of" excitatiou by various stimuli are very familiar. The most obvious result of the actidn of rhcmicuh is seen in the production of movements. If, for instance, there are addeil to a medium containini^ amteine a tew drops of a weak solution of an acid, alkali, or salt, the activity of the animals is at first increased, but soon their psi'udo|)()ds are retracted and they take on a more or less spherical shape. The same effects are produced in other organisms possessing pseudopodia, while the cilia of infusoria have their movements enormously increased. Various forms of muscle- fibres (myoides, smooth and striatetl muscles) contract and tend to take on a spherical form. Crystals of .ut among the higher ani- mals the end-organs in the retina are alone clearly responsive to jiliotic stimii/dtloii. It has been found that when the skin is con- stantly ex])Osed to the intense light of the electric arc lamp that the ephhelial cells of the skin undergo a genuine necrosis, which is not brought about by the heat-rays, but by the short waves of the violet end of the spectrum. The stimulating power of light on the chlorophyll-containing bodies of green plants is easily shown for the absorption of carbon dioxide and the formation of starch take jilace only in the presence of light. The rhizojjod pelomvxa responds to sudden illumination in the same manner as it does to any other stimulus — namely, by quickly taking on a spherical form. Certain flagellate and ciliate organisms are also so sensitive to light that they respond by quick movements. The excitation effects of the electrical currents have been inves- tigated most throughly in nerve and muscle. A sudden change in the intensity of a current arouses a nerve impulse in the nerve, and calls forth a contraction of the muscle. An electrical cur- rent, however, stimidates also while it is flowing uninterru])t(Mlly through any living structure. This is shown in nerve by the heightened irritability at the kathode or region where the current leaves the nerve ; in actinospherium, by a disintegration of the organism at the region of the anode, where the current enters the structure and which ceases as soon as the current is interrupted. AmtTcba) and leucocytes witlulraw their pseudopods and become 32 GENERAL INTRODUCTION. spherical when subjected to an electrical shock ; smooth, striated, and cardiac muscle gives vigorous responsive contractions and re- laxations ; the protoplasm of plant-cells is formed into spherical masses, and phosphorescent animals emit light. The inhibition of living matter is much more difficult to recog- nize. A chemical inhibition is shown by the action of anaesthetics. Mechanical inhibition has been demonstrated by several investiga- tors by showing that the growth of bacteria is stopped by regular vibrations. Heat and cold will both produce thermal inhibition as they respectively approach the coagulation-point of protoplasm and the zero-point. There is no indisputable evidence of inhibi- tory power of light (p/io^ic inhibition). The changes at the posi- tive electrode when a current is passed through a nerve may be regarded as an example of inhibition by electricity. Cell Tropism. — Organisms that are capable of independent loco- motion when acted upon by an influence coming from a definite direction move either toward or away from the source of the stim- ulus. If the latter is a chemical irritant, the phenomenon is known as chemotropism or chemotaxis, and is positive or negative according as the animal moves toward or away from the source of the stimulus. In like manner, pressure, temperature, light, and electricity produce respectively baro-, thermo-, helio-, and gal- vanotropism. The Origin of Life. — It may be said that as long as the earth was a molten mass of excessively high temperature life could not have existed as we know it to-day. During the evolution of the earth living matter must have arisen as the result of physical and chemical factors, as all chemical compounds whatsoever have arisen. The formation of living matter was as necessarily the product of evolution as was the formation of water. At first it was probably capable of manifesting vital phenomena indefinitely, which, as a matter of fact, is true of germ-cells at the present time. Under proper circumstances by means of germ-plasm life is passed from individual to individual, and in this sense cannot be said to suffer death. Cell Death. — According to Weismann, death has been evolved for the good of the species, since in time, through wear and tear, the vitality of aged individuals is lessened and it is to the advan- tage of the species that such individuals should no longer propa-. gate nor even exist. The term death has, however, many shades OENEUM. isTi:<)i>r("rioy. .T5 of nioaiiiiijr. Ill one sense since living matter is continually iiii- rotoi>lasm ? What char.icterizes the elements of living matter? What is a cell? What are "histological dilferentiation " and " jiliysiological division of labor" ? What evidence is there that dead protoplasm ditl'ers from living? Descrilie the jiroperties of the cyanogen groii]>. What is a biogen ? What are metabolism, anabolism. and katal>olisin? 3— Phys. 34 SECRETION. What are the relations of anabolism to katabulism during rest, gfowth, and atrophy? Are all biogens alike ? Describe the internal self-adjustment of metabolism. What is meant by " contact changes" of biogens? What is food? What is ingestion ? What are enzymes ? How is starch formed in the plant-cell ? What is the source of the nitrogen of plants ? What is the function of the nucleus in cells? Explain why reproduction has been called " discontinuous growth," What is growth due to ? Effect of exercise ? Give the various stages of growth. Describe both methods of cell-division. What two methods of reproduction, and how do they differ? Describe conjugation. How do male and female germ-cells differ? What is fertilization ? What is parthenogenesis ? What is the object of fertilization? What forces are active during the development of the ovum? What is atavism or reversion ? Discuss the inheritance of acquired characters. What is the source of germ-plasm ? What is meant by preformation and epigenesis? What are variations of germ-plasm due to ? What is natural selection ? Define phylogeny and ontogeny. What opposite results may stimuli produce in living matter? How may stimuli produce necrobiotic changes? Give examples of excitation and inhibition of active protoj)lasra. Define positive and negative chemotropism. What can be said of the origin of life ? Give various meanings of the term death. What is the cause of somatic death ? CHAPTER 11. SECEETION. The term secretion may be used to designate either the liquid or semiliquid products of glandular organs which are discharged upon free or closed surfaces ; or to designate the process itself by which these products are formed. According as the surface is free (skin, mucous membrane) or closed (blood and lymph cavities) tlic socrction is (cruu'd an cxlcnittl or an inliriKil sccrdioii. Siidi siihstaiici'S s(^rviiig a useful purpose are ti/piraJ .srrntioiix ; when ol" IK) tiirtlier use, are excirtiouH. There is no longer any (loul)t that i/fiiiid-crf/s arc artive in (lie fonnnlion of tlirlr Hccniloiis. The proois are : 1. The irlaiul-cells undergo a niicroscopical ehange. 2. Spccitic sulislanccs in the secrt'tion which are not found in llic lilood or Ivniph. • ">. The liheration of eneriry in the form of heat, pressure, and electricity. 4, The results of the stinuilatiou of the nerve-supply. 5. The action of certain hysical and chemical properties of the living structure of gland- cells. By fi/lnifion is meant the passage of tluids through a mcmhrane as the result of differencas of hydrostatic pressure. Dllf'i(!iio)i is the interpenet ration of the molecules of two tluids when hrought into contact. Osmosis or dialysis is the diffusion that takes place through membranes separating two fluids. SALIVARY GLANDS. The production of saliva is brought about by the joint action of thre(^ larger pairs of glands, the parotids, fdihrndxi/larirs, and su/h lliH/}(((/s, and by iitnnmerablr sma/lrr ones lying in the mucous mem- brane of the mouth and tongue. In close proximity to the jiarotid lies a glandular mass called by Klein the inferior admaxiUarri (socia jHtrotidis of man), and in the connection with the sublingual is a separable portion, the superior admaxiUary. These, as well as many unicellular glands, pour their secretions into the buccal cavity. The distinction lietween nlbiiminous and mucous (jldixla becomes definite oidy when applied to individual cells. A series of glands might be gathered, showing every gradation from those entirelv mucous to those entirely albuminous. The demilunes of Heiden- hain in mucous glands are albuminous cells. The two types of cells differ not only histologically, but also in the character of their products. The secretion from albuminous cells contains, iicsides enzytnes, water, salts, and alitumin. while that from miieona C''//>' contains mucin, which niaUcs it striiiirv and viscid. 36 SECRETION. The activity of secretory cells is well shown by the salivary glands. During secretion the granules which are present gradu- ally disappear from the outer side of the cells, and a clear non- FiG. 3. v.sym V.J. nfi.sym.sm r.sm.p. v.sm. Diagrammatic representation of the submaxillary eland of the do,?, with its nerves and blood-vessels. The dissection has been on an animal lying on its back, but since all the parts shown in the figure cannot be seen from any one point of view, the figure does not give the exact anatomical relations of the several struc- tures (Foster). sm.gld. The submaxillary gland, into the duet (sm. d.) of which a canula has been tied. The sublingual gland and duct are not shown. n.L, n.V . The lingual branch of the fifth nerve ; the part n.l. is going to the tongue, ch.t, ch.t'., rht". The chorda tympani. The part ch.t". is proceeding from the facial nerve : at ch.t'. it becomes conjoined with the lingual n.l'., and afterward diverging, passes as rh.t. to the gland along the duct; the continuation of the nerve in company with the lin- gual n.l. is not shown. .«?w. fjl. The submaxillary ganglion with its several roots. n. car. The carotid artery, two small branches of which, o. sm,. n. and r. sm. p.. pass to the anterior and posterior parts of the gland, r. sm. The anterior and posterior veins from the gland, falling into v..j., the jugular vein. ?>. sym. The conjoined vagus and sympathetic trunks, rj. rer. s. The upper cervical ganglion, two branches of which, forming a plexus {n. f.) over the facial artery, are distributed fn. sym.. sm ) along the two glandular arteries to the anterior and posterior portions of the gland. The arrows indicate the direction taken by the nervous impulses during reflex stimulation of the arland. They ascend to the brain by the lingual and descend by the chorda tympani. stainable material is substituted. The nuclei become more spheri- cal and lie nearer the centre of the cell-body, which shrinks in size. The granular material is apparently used up in the forma- SAiJVAnv (;L.\.\ns. 37 tion iif" llic sccn'tioii, and since tlic ciizyuK'.s iorinod arc ppccilic Milislaiici'S, tlic lormcr arc taken to l»c tli«'ir source and desi^Miatcd as ziivKKjen (jniiiitlis. The forerunner oi' ptijaliii i.s called ptya/ino- (jni ; of jnjtsiii, /iiji>iiiiu(/eii, etc. The. pre SSI I rr in the duct of the submaxillary has been observed at 1!M) nun. Hi;, while the blood pressure in the carotid at the liiiK' was but 112 mm. Hg. The question of the amount of heat trivi'u otrdurini; the activity of the rliloric ariil of the gastric juice. During the activity of the i^astric irlaiids liistoioLrical changes take place especially in the chief colls, similar to those already de.-^cribeil in the salivary glands. They also have a double supply of cranial and si/nijiatltetic nerves. ^Stimulation of the vagi after a latent |)eriod of from four and one-half to ten minutes gives a distind How. The delay is due to the simultiineous irritiitiou of inhibitory fibres. Stimulation of the sympathetic gives no result. The etiect of psvchical states is shown in the "fictitious lueal " experi- ment, in which the a'sophagus of a dog is divided and the two ends are brought to the skin and sutured so as to open externally. Food taken by the dog does not reach the stomach, but neverthe- le.^^s causes a How of gastric juice, which has been shown to depend u\)Oii the integrity of the vagi. The sight of food is alone suffi- cient to cause a secretion. lu order to determine the mechanism of the normal secretion of the gastric juice investigators have converted a part of the fundus of the stomach into a blind pouch with an external opening, while the continuity of the stomach was established by uniting tlu- cut ends. The nerve-sup])ly was not destroyed. The introduction of food into the stomach brought out a secretion in the resected portion in from fifteen to thirty minutes. This was interpreted to be due to the absorption of digested substances from the stomach. The quantity of the gastric juice secreteends upon the character of the food. There is no evidence that the cells of the gastric glands can be stimulated directly. The How upon me<"hanical stimulation is effected through the fibres of the vagus and possibly of the sympathetic. PANCREAS. The cells of the pancreas are mainly of the albinninnns ttjpe, in additi(m to which irregular masses of cells (bodies of Langerhans) are to be found. The latter are clear an.s- kidsf. y. 41 INTESTINAL GLANDS. Evidence as a whole poiiilii to tlu- la rior (/niKjlioii of the solar plcxiia it} left intact, the actniniulation does not take place. SEROUS SECRETIONS. These are produced by the pleura, peritoneum, tuni<"i vairi- nalis, and by the synovial membranes of joints, tendon-sheath.s, etc. The synovial secretion is more glairy and viscid than is truly serous secretion, which is very much like lymph. The function of serous secretion is to prevent friction between surfaces that are in contact. It is of a pale yellow color, alkaline in reaction, viscid, and coagulable by heat. LACHRYMAL GLANDS. The conclusion reacheil for the salivary glands may be applied with little alteration to the glands of the na.sal mucous mem- brane and to the lachrymal glands. The latter resemble an alliuminous .salivary gland, receiving cranial secretory fibres by way of the fifth nerve, and ■■o/mjxdlictic fibres by way of the cervical .sympathetic. .Stimulation of most sensory nerves pro- duces a secretion reflexly. The ducts of the gland lead to the conjunctiva of the upper eyelid, and usually the secretion is just sutficient to keep the eye moi.st, and is drained into the nasal cavity by way of the lachrymal duct. When the secretion is formed in superabundance, it ap|)ears as fears. The.se are alka- line in reaction and contain 1 per cent, of solids, chiefly chloride of soilium. KIDNEY. Although tiie kidney is ric-hly supplied with nerves, there is no iiulisputable evidence of secretory fibres, but changes in the secre- tion of urine can be explained by variations in the blood-tlow. It has been estimated that the supply of blood to the kidney n)ay be from four to nineteen times as large as that of (»ther organs of the body, and equals per minute o.G per cent, of the total cpiantity 42 SECRETION. seut out by the left heart. The secretion of urine can be measured directly, but variations in blood-supply are determined by an in- strument called an oncometer. A rich supply of vasoconstrictor hbres for the kidney emerge from the cord in the lower thoracic spinal nerves (dog), pass through the sympathetic system, and reach the kidney as non-medullated nerves. Stimulation of these nerves causes a shrinkage of the organ and a diminution of the secretion. When the fibres are cut, the arteries dilate, the organ enlarges, more blood passes through the kidney, and the secretion is augmented. The vasodilator fibres to the kidney emerge from the cord through the anterior roots of the eleventh, twelfth, and thirteenth spinal nerves. Normally these fibres — i. e., constrictor's and dilators — are brought into activity reflexly and regulate the formation of the secretion. Any factor that increases the differ- ence in pressure in the renal artery and the renal vein will cause increased secretion of urine. Vascular dilatation of the vessels of the kidney, unless counterbalanced by a general fall of blood- pressure, will give an increased secretion. The following table is useful for reference : Table of the Relation of the Secretiox of Urine to Arterial Pressure (Kirke). A. Secretion of urine may be increased — (a) By increasing the general blood-pressure by — 1 . Increase of the force or frequency of the heart-beats. 2. Constriction of the small arteries of areas other than that of the kidney. {b) By increasing the local blood-pressure by relaxation of the renal artery, without compensating relaxation elseiohere by — 1. Division of the renal nerves (causing polyuria). 2. Division of the renal nerves and stimulation of the cord below the medulla (causing greater polyuria). 3. Division of the splanchnic nerves ; but the polyuria is less than in 1 or 2, as these nerves are distributed to a wider area, and the dilatation of the renal artery is accompanied by dilatation of other vessels, and therefore by a some- Avhat general increase of blood-supply. 4. Puncture of the floor of the fourth ventricle or mechanical irritation of the superior cervical ganglion of the sym- pathetic, possibly from the production of dilatation of the renal arteries. h'in.\i:y. 43 //. Sri'retinn i>f tin' urine viai/ lie iliniiiiis/inl — {a) liij diniiiiisluiiij l/ir i/iiicriil bfoinl-pifssurc />i/ — 1. IMiiiiimtion of tlif torro or rrf(|U('iuy df tlio lioart-ln'Jit.s. l:. l>ilatati()ii of rapillary aiTus titlicr iliaii that of tin- kiiliiry. ;>. division of tlic .-iiiiiial cord Ijcltiw tlu' medulla, wliirli cuuscs a dilatation of tin' irciifral alidominal area, ami uriiic ^CK- crally i-oasos hcin^ sciTctcd. (//) /{i/ inrrai.siiKj titf blood-firvssure by stiimilatioii of the spinul coril ht'low the iiiodulla. the constrietioii of the renal artery which riillows not iicinir compensated for hy the increase of jicneral Mood-pressure. ((•) By cons/iicfi(in of the rciuil aifcri/ l)y !stimulatin.'> equals aiS/if) iri-;iiiis 111' solids in 1000 cc. of urine. In usin;^ this iiirlluxl it must ho reinenihered tiial tiie liniils of error are nuieh widi'r in diseased than in healthy urine. The most ini|)ortaut constituents of the urine are urea, nric arid, .ranfliiii, lni/i(i.rant}iiii, gvanin, adniiii, rrratiiiln, hippitnc acid, coiijiujdtcd .'hy- sioioi,neal oxidation of j)roti'ids and albuminoids. One gramme of proteids yiehls ;■ of a gramme of urea, as determined from the con- tained nitrogen. But as some nitrogen is eliminated iu uric acid, ereatiuin, etc., the amount of urea cannot he ttiken as an indica- tion of the total i)roteid hroken down. Urea is also found in other secretions, as the milk and the perspiration. The kidnev does not manufacture urea, as is shown hv these focts : 1. I'rea does not form in the l)lood when irrigated tlirougli an isolated kidney. 2. The urea in the hlood (0.03 to 0.15 per cent.) accumulates steadily as long as the animal lives if the kidneys are extirpated. The evidence that urea is formed in the liver is as follows : 1. The hlood of a well-fed dog, when irrigated through an iso- lated liver, increases in the amount of urea contained, which is not true of the hlood of a fasting animal, from which jnay he concluded that the first contains sul)Stances which the liver can convert into urea. 2. This power is })ossessed only hy the liver. 3. Ammonium carhonate added to the blood and irrigated through the liver is converted, at least partially, into urea. 4. Removal of the liver decreases the percentage of urea in the blood. Trea arises from ])roteids by hydrolysis and oxidation with the formation of ammonia compounds, which are changed to urea in the liver. Ammonium carbamate may he one of the precursors of urea, having been found in the hlood of dogs, and is easily converted into urea by the loss of water. However, other and more complex anmionia conijiounds, like leucin and glycocoll, can be converted into urea hy tln' liver. Tiie hlood of the ])ortal vein 46 SECRETION. is normally three or four times as rich in anniionia compounds as is arterial blood. Since ured does not entirely disappear upon extirpation of the liver, it must have some other source, and a decomposition-product of proteid by trypsin — lysatinin — has been suggested as a possible source. Uric Acid. — Its total quantity in the urine in twenty-four hours varies from 0.2 to 1 gramme. In birds and reptiles it takes the place of urea as the main end-product of the disintegration of proteids, and its place of origin has been proved to be the liver. In mammals this has not been substantiated. According to one investigator, uric acid is derived from nucleins being their specific end-products : for, among other things, it is found that feeding with substances rich in nucleins, like the thymus gland, leads to an increased elimination of uric acid. Upon feeding an animal with uric acid it is found that some of it is excreted as urea. Xanthin, hypoxanthin, guanin, adenin, etc., which are closely related to uric acid, are probably derived from the same source. They are found in the greatest quantity in muscle. Creatinin is derived partly from proteids eaten and partly from the metabolism of proteids in the body. Muscle contains creatin as a constant constituent, which, when taken into the stomach, is eliminated as creatinin, the latter differing from creatin in con- taining one molecule less of water. The quantity of creatinin in the urine of man a day is about 1.12 grammes. Hippuric acid is excreted in the urine of man to the extent of about 0.7 gramme in twenty-four hours. Foods like vegetables, which contain substances that yield benzoic acid, increase the out- put, since a union of benzoic acid and glycocoll taking place in the kidney forms hippuric acid. Some, however, is the result of proteid putrefaction in the intestines. Conjugated sulphates are ethereal salts of organic compounds of the aromatic and indigo series. Among the most important organic radicals are phenol, cresol, indol, and skafol. These are formed by putrefactive processes in the intestines from proteids, and are partly excreted in the faeces and partly passed into the blood. Since they are injurious they are combined with sulphuric acid to form the conjugate sulphates, which are harmless. Sulphur is also excreted as simple sulphates and as unoxidized sulphur compounds. Water. — The quantities lost through the kidneys and skin stand in inverse proportion to one another. Since water lost through si-ynirnoss nr tuk skix. 47 the skill aHVcts llic iioniial coiistitwliitii of the iiriiic lliriiiit:li \\u: inv'.li'iiii of llu' l)lo()(l, it is to l)i' rxpcctcd that otiicr siii)Slaiiccs in ill,' riiculatioii niii^iit liave similar iiilliicncr. Tiiis, as a iiialtcr of fad. is true. A tomporarv alti-ralion of llu', lilood liy the a')sjori)tit»ii of large (|iiaiitilii's of waici- ami ilu' jn-esenee ol" diurctitw iaereases lln' ilow of water from the kidneys. It" saline diurcticx (potassium nitrate, soiliiiin chloride, urea, dextro.se, etc. ) are iii- jectt'd into i hr lilood. an al)iindant secretion soon takes place, uiiicli is accoiniianiiMl liv an cnlarii-cnicnl of ihc ki»i(k'.s ilw fat-jriohules, (certain alljimiiiious Ijudii-s known as m/ostrnm n>ipi()ic/cf<, \vlii(rli may 1r' cells ol" tin; gland or tiKiy, perhaps, have their origin in wandering connective-tissue corpuscles. The plasma of the milk consists of water holding in solution casein, lucto-ulhumin, lacto-glohulin, lacto.>, 7 *><>,( )()(). They are not, as was formerly i)elievev the inijestion of thvroid extracts and hv feedin;j^ with the fresh -land. It appi'ars that th" ihyroitis and accessory thyroids, on the one hand, dilier from llu' parathyroids, on the oilier, in that removal of the lirsl causes slow trophic disturbances, while removal of the last results in acute disturbances and quick death. These glands may be regarded as functioning in two ways. They may either antagonize toxic substant-es that are found in the blood, or may produce a secretion which is necessary to the metabolisjn of the i)oily in general, and particularly of the central nervous system. There hius been isolated from the thyroid a substance which is peculiar iu containing a large percentage of iodine, and which is tor the most part, while in the gland, combined with proteids. It has been named iodothyrhi. The parathyroids contain relatively larger amounts of this substance. It is quite stable, and possesses llie same beneficial action as the thvroid extract. PANCREAS. Extirpation oi' the pancreas is followed by the apj)earance of sugar in the urine, polyuria, emaciation, muscular weaknes.s, and ultimate death. The result depends upon the completeness of the removal ; one-fourth to one-fifth of the gland remaining prevents the svniptoms. As in the case of the thyroid, they may be pre- vented bv grafting a portion of the gland anywhere under the skin or in the abdominal cavity. The sugar of the blood is in- crea.sed I'rom 0. 15 to O.-jO jier cent., and the glycogen of the liver disappears. C'arbohvdrate foods are not used \\\\ but are a)i]>a- rently eliminated in the urine. It is believed that the ])ancreas gives oft' a substance that is necessary either to the consumption of sugar in the body or else hinders the liberation of sugar from sugar-producing organs. It may be of the nature of an enzyme. 52 SECRETION. LIVER. The liver in its, production of urea and glycogen resembles those organs producing interual secretions. The blood of the portal vein brings sugars and proteids to the liver, which are con- verted into animal starch or glycogen (CgHjgOg)u. The latter can be seen in the liver-cells microscopically. As the demand arises, it is by a process of hydration changed to dextrose, and secreted back into the blood, to be made use of by other tissues. Urea is made by the liver-cells from ammonia compounds, and secreted into the blood, to be excreted by the kidney. In both cases the liver functions for the good of the entire body. It is possible that it may also be essential to the conservation of iron of broken-down hsemoglobin and in the formation of conjugate sulphates. SUPRARENAL CAPSULES (ADRENAL BODIES). The removal of these bodies is more quickly fatal than the removal of the thyroids, death occurring in a few hours or a few days. The symptoms are muscular weakness, loss of vascular tone, and great prostration, resembling those of Addison's disease, which involves lesions of the adrenals. The glands may normally be supposed to remove toxic substances from the body, which are formed chiefly in the muscles. Aqueous extracts of the medulla of the gland injected into the vessels of an animal will cause a marked slowing of the heart-beat and a simultaneous rise of blood- pressure if the vagi are intact. When the latter are cut, the heart-beat is increased in its rate and the blood-pressure rises enormously. The effect is due to a direct action upon the muscles of the blood-vessels. It requires very little of the substance to produce maximum effects, but they are of a transitory nature. It has been found to be present in the adrenal vein, and is increased by stimulation of the splanchnic giving evidence of distinct secre- tory fibres to the gland-cells. An imstable, basic body, called epinephrin, has been isolated, which gives the same physiological effects when injected into the circulation as does the extract. PITUITARY BODY. Extracts of the infundibular portion of the pituitary body cause a rise of blood-pressure and a slowing of the heart-beat TESTIS AXD OVARY rUVMI'S <:L.\SI> AM> SI'LIIES. 53 wln'ii injcctiMl iiitravciiou.sly. Kciiioval i.A' tlu- pituitary body is followiMl liy muscular tri'inor.s spasms, ilys|)im.'a, au«l Wt-atii. I'allio- loiricallv, legions of \\\v pituitary ar<; coniiectcil with a (litsejuje of the bones causing hypertrophy, known a.s acromnjali/. TESTIS AND OVARY. Hrown-S.'(piaril lirst invusliirated tin- internal secretion of the testis. He showed that an extract of the <;land or of the spermatic fluid when inji-cted unermt/( (C"JI,,N,). It is not essential to life, since the testes may he removed without fatal results. It is a well-known fact that ovariotomy and prema- ture menopause may he followed by abnormal mental symptoms and often by a irain in weiirht. In oKfeoinalaciti, a disease giving rise to a .softening of the bones, removal of the ovaries has been found to e.xert a favorable influence. In dogs complete ovariotomy is i"ol lowed by a lessening of the consumption of oxygen, which is increased again by feeding with ovarian extracts. These facts show the influence of the ovaries upon the general nutrition. KIDNEY. tSome investigators have describeil the effects of extract? of the kidney which cause a rise of blood-pressure. The active substance has been named rennia. THYMUS GLAND AND SPLEEN Extracts of the thymus and spleen seem to have no specific effect. The function of the latter organ is very little understoiMl. It may be renjoved from the organism without serious injury, giving rise, it is a.s.serte(l, to an enlargement of lymph-glands and to an increa.se in the amount of bone-marrow. It has also been found that the lunnber of red blood-corpuscles is diminisheil. The following suggestions of the function of the S|)leen have been offered : 1. That the spleen manufactures blood-corpuscles. This is 54 SECRETION. without doubt true iu man duriug foetal life and at birth, but it is not known that it contiuues throughout life. 2. That the spleen destroys the red blood-corpuscles. The evi- dence for this theory is that spleen tissue is rich in iron-holding compounds, and that certain amoeboid cells of the spleen have been seen apparently ingesting and destroying red blood-cells. 3. That the spleen produces uric acid. Uric acid is found in the spleen, but also in all lymphoid tissue. 4. That the spleen produces an enzyme which is carried to the pancreas iu the blood, converting trypsinogen into trypsin. A striking feature of the spleen is its rhythmic movements. It under- goes a slow expansion and relaxation, with definite periods of digestion. These are due to vasomotor changes, the maximum vasodilatation occurring about the fifth hour after a meal. In cats and dogs there are, in addition, rhythmical changes taking place from minute to minute which serve to maintain a constant circu- lation through the organ. The spleen is well supplied with nerves, stimulation of which produce a contraction. The chemical substances found in the spleen are interesting, since they indicate a marked metabolism. There is a large per- centage of iron in an unknown organic combination. In addition, there are fatty acids, fats, cholesterin, xanthin, hypoxanthin, adenin, guanin, and uric acid. QUESTIONS ON CHAPTER II. What is meant by the term secretion ? Distinguish between external and internal secretions and excretions. Give proofs that gland-cells are active during secretion. Define filtration, diffusion, and osmosis. What is the source of saliva? Discuss albuminous and mucous glands and their products. Describe the histological changes in salivary glands during activity. What are zymogen granules ? Describe the nerve-supply of the salivary glands. Give results of the stimulation of chorda tympani and sympathetic nerves. What are the proofs that secretion is not simply due to increased blood- supply? What is the relation of the composition of saliva to the strength of stimu- lation ? Give Heidenhain's and Langley's views on secretion. What is paralytic secretion ? Antilytic secretion ? Explain changes in secretion produced by drugs. Give mechanism of normal secretion of saliva. Discuss the cells of the gastric glands. Give the results of stimulation of their nerve-supply. QUESTIONS 0.\ CUM'TI-Jl //. 55 III wlial ways umy tlicRastric juici^ he caused to (low? Dcsi tIIk! cliaiifjos in ci-lls ply to pancreas. What causes the pancreatic juice to flow normally? How luucli liile is secreted in a day? What is the relation of hile-.socretion to the hlood-supi)ly ? Descrihe the cH'ect on l)ile-secretion produced hy stimulation of the cord and s])laiichiiic nerves. Wliat can lie said of the influence of the nerve-sui)ply on the cells of the intestinal mucous memhraiie? Discu.ss serous secretions. What is the nerve-supply of the lachrymal glands? What are tears? Are there secretory tilires to the kidney? (live the relation of the blood-sujjply to the secretion of urine. What is an oncometer? Descrihe the nerve-sui)ply to the kidney. In what way is the secretion of urine influenced hy nerves? (live evidence that cells are active in the formation of urine. Where iu the kidney does the excretion of water and s;ilts take place? Hive reasons for thinking that the cells of the glomerular epithelium are active in secretion. How is the action of diuretics explained? Descrihe the urine and state the amount formed. What is the color of the urine due to? Why is the urine of complex comjiosition ? What are the most important constituents of urine? Discuss the urea of the urine. What are the i)roofs that the kidney does not manufacture the urea? What evidence is there that urea is formed in the liver? What is the precursor of the urea iu the blood? Discuss the uric acid of the urine. What is the source of the xanthin bases? What is the source of creatinin ? Discuss hippuric acid of the urine. Wh;it are conjugate suli)hates? In what other forms is sulphur excreted from the body? What is the relation of the water lost through the kidney and the skin ? Discuss the action of caffein and digitalis on the secretion of water by the kidney. What are the inorganic salts of the urine? Discuss the secretions of the skin. How are the swi'at-glands stimulated to activity? Wliat is the method of action of temperature in jiroducing secretion of sweat ? Descrihe the properties and method of fonnation of the sebaceous secretinu. Describe the secretion of the mammary glands. What are colostrum corpu.scles? C'omjjare human milk with that of the cow. Describe the liistologi- ^^wiiit; to tlu; uncertainty <><' their slrue- liire. classiticalioiis of proteiils vary in minor ways. Il will l)e sniliciiiil lo hear in mind thai there are utinji/c and eoiiihincd jtro- t'iils. As concrete (examples of the first may he ^iven ej^g- alhunirii and lihrin ; of the second, iuemoglohin, mucin, and casi'in. SiinpU' j>rotei and fdurorholir acid. Both are present in human ])ile. and may be detected by Petfenkofera reaction, which consists in adding to the li(piifl to be tested a few drops of a 10 per cent, solution of cane- sugar, and then, carefully, strong suljjhuric acid. The temjiera- ture must be kept lielow 70° F. If bile-salts are pre.sent, a violet ring is fornuMl at the junction of the licjuids, which is due to the 64 DIGESTION. formation of a substance known as fiirfurol. The latter reacting with the bile-salts gives the color.' The bile-salts are reabsorbed, partially at least, and again given off by the liver. The value of this process is not known unless it is to economize material, since the bile-salts serve to hold the excretion cholesterin in solu- tion, which is constantly present in the bile, and serve also to assist in the absorption of fats from the intestine. GJiolesterin (C27H46O) is eliminated by the liver-cells and remains unchanged in the faeces. It is a crystallizable, insoluble substance, found particu- larly in the medullary substance of nerve-fibres. The nucleo- albumin of the bile is formed by the cells of the ducts and gall- bladder, and gives to bile its mucilaginous character. Bile has feeble antiseptic powers, and to some extent retards putrefactive changes in the intestine, and it also neutralizes the acid chyme from the stomach. INTESTINAL SECRETION. The intestinal secretion, or succus entericus, may be obtained by the Thirij- Vella fistula, which is made by cutting out a portion of the intestine and bringing the cut ends to the abdominal wall, so as to form two openings. It is a yellowish liquid of alkaline reaction, having no influence on proteids and fats, but may con- vert starches to maltose and dextrin, invert cane-sugar to dextrose and levulose, and change maltose to dextrose. This shows the presence of amylolytic and inverting enzymes. The latter is called invertase. SECRETION OF LARGE INTESTINE. This secretion is composed mainly of mucus, is scanty, alkaline in reaction, and has no enzymes of its own. Digestive changes occur, however, for some time, and are due to enzymes brought down from above. Extensive bacterial decomposition takes place. Bacteria may be found in any portion of the intestinal tract. It has been ascertained that the ileum, at its junction with the colon, is acid after a mixed diet. This is due to acetic acid (0.1 per cent), which is formed through the action of bacteria. In the large intestine bacterial decomposition results in the forma- tion of many substances. Some, like skatol, carbon dioxide, hy- drogen sulphide, etc., promote movements of the intestine ; some, 6T.1/.1/.I/M or Dici.sTioy. 65 like plu'iiol ami imlol. an- rr:il)>url)t'«l, to he eliniinatcfl in the urine. Faeces. — The t'n.'ee,s vary in eoinpositioii and amuunt with the nature auil tlie (luantity of the food. Uu a mixed diet tiie amount in tweuty-four hours varies from 100 to 500 grammes in weight. Its eonstituents are indige.>^til)le materials, undigestetl food-stuHs, inte.>:tinal secretions, products of l)aeterial action, chole.sterin, ex- cretin, mucus, piirment, salt.s gases, and micro-organisms. Among the products of bacterial action are indol (C«H;N) and ahitit' (C,H.,N), which are crystallizahle bodies giving odor to the ficces. The color is due to lii/drobillrnhin. SUMMARY OF DIGESTION. Proteid food is hut slightly altered in the mouth, and only in a mechanical way. The muscle-tibres of meat, for instance, are iTUshed, anil their connective-tis.sue sheaths broken by the action of the teeth, thus becoming somewhat white in appearance. Mixed with saliva, which has no digestive action on these food-stuHs, they are passed into the stomach and brought under the intluence of the gastric juice. By the combined action of the hydrochloric acid and the ferment pejwin proteids pass through a series of steps which consist es. g I'd ■p,o ?:§ 2g gs^ ■2Sd ■" So '3 « ^ ^v w ^; o p i* >yi (-( H oo ^■SmC M„ ;ii ^ Hi's -in 5 5;i^ B -2 bo'" °S 1 C^ cu goo M CO cu m S g -" .5 OS '0r:'d!Hoa;rC'G~cu sh ■CftH (D 0< ='■-'.2 rH"C -"•^^§-^ Pi; spin -+3 m 03 cS OS'S .Q a .■^ & 5 0) o 5«a .5 oi fl 2 =^'3 'oi a fli oj,-; ^ OS 2 o ,a2|oS *">&! 53 .2 I Y i o.S CD S ^ 3s f OS — OS CS CD m OS g cS :-a C3 NITROaEXOUS ORdAMC liODIKS. 6i> OQ M ^ Hi O Ph M H . ■ Xi *2 g «§o,2^ "3 tj g 3-5 S3 5 ? S£*^ . 09 Xi ' C3 c o a o >. CJ ^ J3 5j ■^ Si a ■Q-S'— L^ c ^ ^ c lold. liver t foui rived a 3 CO 3 w - o

wn in ligating the thoracic duct, which does not inter- fere with ti eir disappearance. Neverthele-ss they do not appear 82 ABSORPTION. in the blood as such, and if preseat, act as poisonous bodies which cannot be used by the tissues and are immediately excreted by the kidneys. It is probable that the epithelial cells convert them into serum albumin. Carbohydrates which are changed to diffusible sugars, dextrose, and levulose are also absorbed directly into the blood, and the portal vein has been found to show an increased percentage of sugar after meals. The lymph of the thoracic duct shows no such increase unless excessive quantities have been taken. Fats, it is conceivable, may be absorbed in an emulsified condition or as glycerine, fatty acids, and soaps. Experimentally it has been found that the greater part of the fat (60 per cent.) is passed through the epithelial cells and through the stroma of the villi to the central lacteal, which is the beginning of the thoracic duct. The remainder, however, remains unaccounted for and may be absorbed by the blood as fatty acid and glycerine. There is very likely a synthesis of the. latter substances in the body of the epi- thelial cells into neutral fat. The absorption of water and salts by the small intestine is very active, but there is also a secretion of water into the intestinal lumen, so that the contents remain of the same fluid consistency. Water and salts are absorbed directly by the blood unless excessive quantities are taken, when a portion passes through the lymphatic system, accelerating the rate of flow of the chyle. ABSORPTION FROM THE LARGE INTESTINE. The absorption from this part of the alimentary canal is con- siderable, as is shown by the changes in its contents, which, enter- ing the ileocsecal valve in a fluid state, are converted into solid faeces. Of the 15 per cent, proteid present, some is absorbed and some is destroyed by bacterial action. The results obtained from nutrient enemata consisting of egg-albumen, salt, and milkfat, shoxo the absorbing capacity of the large intestine. Animals may be kept alive by this method of nourishment, although no enzymes are present to digest the food. QUESTIONS ON CHAPTEE V. What conditions are present in the alimentary canal that favor filtration and osmosis ? Give proofs that epithelial cells are active during absorption. METABOLISM. 83 What jfflths may iihsorbed prcMlucts take in tlicir passage into the blood? Distuss the ahsorptidn tluit take> plaie in the stomach. What conditions in the small intestine favor absorption ? Wliat is the patli taken by abs'>rl>ed proteid? In what form il<> pmleids apj ear in tlic blood? Where are they clian}{eF MI'/l'MK H.ISM. 8!) organic combination witii footl-stiilis. ( uniirora do not crave salts UH hcrbivora do. This i.s explained hy ]iunge as l)eing the re.sult of the fact that phmtii contain an excess of jK)ta8sinni salts, which react with sodium chloride to form potassium chloride and a cor- nspondini; sodium salt, which are excreted ])y the kidneys when they reach above a normal limit. The following uses of cnlciniii xdlt.-f have been given : 1. riiey are necessary to the development of the bones, as a dill poor in calcium salts brings about a condition sinnlar to rickets in children. 2. They are necessary to the coagulation of blood, lymph, and milk. o. They are necessary to the rhythmic activity of the heart and to the normal activity of all protoi)lasm. The calcium acquired and lost by the body normally is very small in amount, and is excreted mainly through the intestinal walls. The main portion of the calcium of the fieces, however, is that ingested with the food, and simply passes through the canal. It is probable that the calcium, in order to be absorbed, must be in organic combination. The salts of iron are of importance in their relation to haemoglobin, which, being continually lost, must l)e replaced. ^lost of the iron of the food, including that of the luemoglobin of meats, is passed out imchanged in the fieces, and to this is added a slight excretion of iron from the intestinal walls. The iron absorbed by the system is probably in the form of organic compounds. DETERMINATION OF METABOLISM. In determining body-metabolism the nitrogen of the excreta is multiplied 1)y 6.2") to give the amount of ]iroteid destroyed. The value fi.2o is obtained from the proporti(m — proteid molecule : nitrogen contained : : 100 : IG. It has been ascertainele bodies are fats changed ? What are the function and the origin of the l)ody-fat? Give proofs as to the origin of fat. What values have water and .salts to the animal? What .salt especially undergoes a change in the bodj' ? Why do herbivora crave salt.s? What are the sources of the salts of the body? What are the uses of calcium salts? How is the amount of jiroteid broken down by an auinial determined from the nitrogen of the excreta? How is metabolism varied under difl'erent conditions? Is the excretion of urea increased by muscular work? Is the excretion of CO2 increased ? Give changes in nietabolism during starvation. How are the difterent organs atTected by starvation ? CHAPTER VII BLOOD AND LYMPH. BLOOD. The blood, a chemically complex fluid contained within the vessels of the body, hjis been recognized from the earliest times as indispensable to tlie life of man. An excefo^ive hemorrharje pros- trates, enfeebles, and may cause death. This becomes evident when it is known tliat the blood carries to the tissues material for their c/roirfh and rrjjalr, and removes from them inaffcr.-^ that have become rjf'cfr. It equalizes the tenijicratiirr of the body, and mtiintains uniform Imhihifioii rrlafions lietween the ('ell.-<. It is an intenial meflium. that liears the same relations to the ihxnm that the oidrr world does to the entire body. It forms in total nearly one-thirteenth of the bodi/-vs, and airain warm until tlu' acid ha.s nearly disappearetl. When cool, microscopic, characteristic, hrown (■rt/-- is^m itiL Fio. 6. Blue. '■"T^"T"" I = 5 iDdlgo. OxyhEemc)globin and NO;.-lia;moglobin. CO-hsemoglobiu. Reduced ha-moglobin. Hffimatin in acid solu- tion. Hfeniatin in alkaline solution. Reduced haematin. Polar spectrum with Fraunhofer's lines. JS i4 the presence of blood. The presence of cells of certain size and non-nucleate0 per cent.), but a portion aj)pears in the serum as a new, globulin-like proteid called yi^nn- 100 BLOOD AND LYMPH. globulin. Calcium salts are absolutely essential in order that this reaction may take place. Their exact behavior is still under dis- cussion. It has been stated that the disintegration of leucocytes and blood-jilates in the blood sets free a nucleo-albamin, which may be considered the precursor of the ferment and called prothrombin. Prothrombin unites with calcium to form the ferment, which has the power of reacting with a portion of the fibrinogen molecule by transferring its calcium to it and so giving rise to fibrin. Fibrin ferment was originally prepared by subjecting serum to an excess of alcohol, which coagulated the proteids. The latter were re- moved and extracted with water. Such preparations were found to coagulate fluids like hydrocele liquid, which normally do not clot spontaneously or at least very slowly. The nature of the action was believed to be that of an enzyme, since very small quantities produced great changes, and it was destroyed perma- nently by heating to 60° C. By allowing the blood to run from the vessels directly into alcohol it was found that the ferment is not present in normal blood ; that, moreover, it has its origin in the leucocytes is shown by the following facts : 1. In microscopic preparations of coagulating blood the fibrin fibrils radiate from broken-down leucocytes and from blood-plates. 2. Whatever prevents the disintegration of the white blood- cells retards the coagulation of the blood. Clotting within the blood-vessels may be brought about by the presence of foreign bodies or by injury to the epithelial lining of the vessels. A¥heu the clot is confined to the injured area, it is called a thrombus. General intravascular clotting is brought about by the injection of fibrin ferment, nucleo-albumins, etc., but this is not accomplished easily, owing to a defensive function for the body exerted by the cells of the liver. Sometimes the blood is rendered less coagulable by the injection of the above substances, constituting the negative phase of the injection. This is explained by the assumption of the predominance of histon over leuconuclein, both of which are formed by the breaking down of leucocytes. Histon retards the coagulation, while leuconuclein favors it. Nor- • mally the blood of the body is prevented from clotting by the integrity of the lining epithelium of the vessels. In the living test-tube experiment, for example, the jugular vein with its con- tained blood are removed from the neck of the horse, and it is found that the blood under these conditions remains fluid liLOOD. 101 until tlu' epithelial cells of tiu' Mood-vesst-ls undergo degenera- tive cluinged. If M not known wlidt jterccnttKji' of h/oud unnj he lost bij man thromjh hcmorrluKje witlioKt Jatal rrsiiUn, hut Jinlyintj from fxjtrri- niintu upon lower animals, if may be jnit at about -i per cent, of the boil I/- weight, or one-fourth of the total blood. Reijeneration of the blood takes place rapidly and is completed in from twenty-tour to tbrty-eight hour.s. xVt'ter severe homorrhafre recovery is more certain if a solution of solood-pressure from rising much above the normal. After the in- jection the arterial and venous pressures return quickly to the normal, generally within an hour. Injection of saline solution iliffers from transfusion of blood in that in the former case the blood-flow is accelerated. The solution injected must be isotonic with the blood of the animal, of the same temjierature. and every precaution taken to |)revent the entrance of air. When injection of salt solution is maintained for some time, the work of the heart is increased, and cardiac failure somi-times results. In the en- 102 BLOOD AND LYMPH. deavor to avoid the latter it has been found that blood-letting rapidly reduces arterial pressure, owing to a general paralysis of the vasomotor apparatus through overdistention, so that the ani- mal is easily killed by the hemorrhage. One hundred and fifty per cent, of the normal quantity of blood of the animal is the maximal amount that can be injected without directly endanger- ing the life of the animal. Transfusion of blood is dangerous for two reasons : 1. Strange blood, even after defibrination, carries an excess of fibrin ferment liable to cause intravascular clotting. 2. The blood of one animal has a globulicidal action and toxic effect on the corpuscles of another. By globulicidal action is meant that property of the serum of an animal which causes it to destroy the red corpuscles of the blood of another, thereby ren- dering it laky. The white corpuscles may be destroyed as well. As an example it may be said that man's serum is globulicidal to rabbit's blood. Similarly the blood of one animal may be poison- ous to that of another aside from its globulicidal action. Thus the injection of 10 c.c. of dog's serum will rapidly kill a rabbit. These properties are destroyed if the blood is heated to 60° F., and they may, as has been suggested, be the result of a proteid substance — an alexine — which is present in small quantities in the blood of every animal. LYMPH. Lymph is a pale, straw-colored liquid found in the extravascular spaces and lymph-vessels of the body, bathing every tissue-ele- ment. It is slightly alkaline, of a salty taste, and has ??o odor. It contains a number of leucocytes ; after meals, fat-globules ; accidentally, red corpuscles and blood-plates. Lymph contains the three blood-proteids, the extractives, and the salts. The last are in the same proportions as in the blood ; the proteids, especially the fibrinogen, are in lesser amounts. Lymph coagulates more slowly and less firmly than blood. During digestion there is a marked increase of fats in the lymph of the intestines, making it resemble milk, and it becomes known as cJiyle. The lymph de- rives substances from three sources — from the blood, from the tissues, and from the villi of the intestines. It is first collected into capil- lary spaces, which open into definite lymphatic vessels which Ql'KSTIOyS ON VlIM'Tim VII. lO.'i tiually empty their couteiits into the hlood-ve.ssels at the junetiou of the siihehivian and internal jii<,Mihir veiii.s. The eontinnal Ibrniation of lymph, aided by sui)sidiary forces, leads to a rela- tively hijjjh |)re.ssure in the lymph-spaces, which drives the lym[)h to the veins or points of lowest pressure. Among the Kiihsidiary forces may he meutit been succexiifiil. The capilla- ries, however, in different regions of the body have a different structure, which is not optically recognizable, but which gives them different permeabilities, so that they influence the character of the lymph formed, particularly in regard to the percentage of proteids. QUESTIONS ON CHAPTER YII. How docs excessive hemorrhaKe affect man ? Wliat is the function of the l)loo(l? What is the total quantity in the body of man? How (Iocs the quantity vary? How is the total <|uantity of an animal estimated? How is the hloml distrihutcil in tlie body? What arc I lie compoiiciits of the l)lood? What is the cause of the difference in colir in arterial and venous blood? What makes the blood opaque? What is laky blood? Give the physical and chemical properties of blood. Discuss the corpuscles of the blood. What is ha'in(ij,'lobin ? How is it held in the corijuscle? What is huMnochromorjcn ? What is the total area whicli the red corpuscles expose to tlie action of the air? Discuss some of the comiiouiids formed by luenioirlobin and various jjases. Explain why illuiniiiatint; <,'as is danj^'crous wiicn iiihalc|ioiesis? Win re are red (■iiri)ns(lcs formed? Describe the process. How are the white blood -cells cla.ssilied? 104 CIRCULATION. What is diapedesis ? What is the function of leucocytes? Discuss the blood-plates. Describe the plasma of the blood. By what methods may plasma be obtained free from corpuscles? Explain the effect of the injection of peptones into the blood of an animal. Why do oxalate solutions affect coagulation ? What are the chemical constituents of plasma? Give the percentage of serum-albumin in the blood of man. How is it separated from the globulins ? What facts indicate that there is more than one kind of serum-albumin. What is the percentage of serum-globulin in the blood? Give its probable source. What is the percentage of iibriuogen in the blood ? What substances are included under extractives? What peculiarity in the distribution of salts in the corpuscles and in the plasma ? Describe the process of clotting. How is the buffy coat produced? Give the chemistry of clotting. How is fibrin ferment obtained? How has it been shown that fibrin ferment is normally not present in the blood ? Give proof as to the origin of the fibrin ferment. How may intravascular clotting be produced ? Explain the "negative phase " produced by the injection of ferment into the vessels of an animal. What experiment shows that the epithelial lining of the vessels normally prevents clotting of the blood ? How much blood may be lost without fatal results ? Why is the injection of sodium chloride solution beneficial after severe hemorrhage ? Why is the transfusion of blood dangerous? What is meant by the globulicidal and toxic actions of the blood? What is defibrinated blood ? Give the composition and the physical properties of the lymph. What is chyle ? What is the source of lymph ? What forces cause the lymph to flow into the blood-vessels? To what extent do the capillaries influence the composition of the lymph ? CHAPTER VIII. CIRCULATION. THE HEART. The blood is forced through the vessels that contain it mainly by the rhythmic contractions of the heart. Its path, in general, is as follows : Beginning with its exit from the left ventricle it THE llEMir. 105 ]iasscs into llio aorta, ami tlinmirli its varidiis hranchcH is ra|)iper disc are two holes, a and h, continuous witli .1 and li respectively, and in the lower disc are two similar holes, n' an\ i\ sHtrht nltcratioii dftlie "niaxiimiin nmnonieter " it may lie converted into one lliat records ininiiiuini pressures. \\y the em- liloyineiit of .«iich iiiatioinelers it lias lieeii a.scerlaiiied upon a dog in one case that the inaxinium pressure in the ventricle rose as hii^h as 234 niui. Hg., while that in the aorta reached 212 mm. Iljr. The minimum of the left ventricle was minus 3H mm. lljr., wliile that of the aorta did not jjet lower than 120 mm. Hg. These values vary, but their relations to one another may he taken as an example of what is true of both ventricles. It is seen that tlie jire«sure in the artery is always hl(jh, fluctuating but little, while that of the ventricles rises above the highest arterial pressure and falls much l)elow. The pressure of the blood in the ventricle must overcome that within the arti'ry to open the semilunar valves and force the blood into the artery. As the pressure falls in the ven- tricle the semilunar valves close as soon as it is less than that of , , ., , 1 i -i. hdrse (after riiaiivomi aiui Miircy): the arterv, and prevent regurgita- «,o', bofrinninf; nfcaniiac cycle : '',/*', tinn WhpTi tlie nre=sure in the rise of pressure due to auricular sys- tion. >> nen ine yiresbure in me ^^^^, ^.^ pressure due to ventricular ventricles is at its lowest, the systole: rf', oscillations due to inertia: , , , , • n i.1 1 e,e', close of cardiac cycle. blood streams in from the large veins and from the auricles, because the pressure in the latter, although low, is higher than that in the ventricle. Curves of endocardiac pressure which are obtained by inserting a hollow probe into the various chambers of the heart difter in their form as the method is by air or by liquid. Pressure-curves from the ventricle transmitted by air are peaked, the pressure rising swiftlv to a m:iximum, and then as rapidly falling to or below atmosjiheric pressure. There follows then a slow gradual rise until the next systole of the ventricle. Transmission by water gives the same curve, with the excejition that the jieak is replaced by a plafirnt — /. ^., the pressure instead of falling after reaching a maximum is sustained for s(mie time. The latter is ])robably the truer form of the pressure change. The fluctuations of the plateau Simultnneous tracings from the ri>;ht auricle and ventricle down over the auricles, and some have contended that the tlow of venous blood is never checked, but that the contracting vi'ins and auricles carry it snioollily into the ventricles by com- pensating l»y tiicir contraction for the expansion of the auricles and ventricles and the opening of the cuspid valves. The aai.^e of the rhijthiiiic movements of the heart lies within itself, since it can be severed from the central nervous system with- out necessarily destroying its activity. For some time many ob- servers contended that the rich nerve-supply was essential, but it has been shown that many forms of contractile substance may be rhythmically active. A strip of muscle cut from the apex of a tortoise's heart, which contains no ganglion-cells, and suspended in a moist chamber, may beat as long as thirty hours with a slow rhythm. Very small microscopical pieces from the bulbus aortas of the frog, which are proliably devoid of nerve-cells, contract rhythmically. Curarized striated muscle placed in certain saline solutions will show a regular rhythm for hours. Many inverte- brates have hearts that are not provided with nerve-cells. The Jirarf of fhr nnhn/o hrafs before the iierrex Jiare r/ro)r)) Into if. The canliac contraction is preceded by a change of electrical potential, which sweeps over it in the form of a wave. Both nor- mally take the same course, beginning at the great veins and spreading rapidly over the auricles, then a short pause, after which they spread over the ventricles. At times the contraction may originate in the ventricle. Thus, by drawing a tight liga- ture about the heart at tlie junction of the auricles and ventricles, the rhythm of the b.eart is disturbed and the ventricle beats with an independent slower rhythm. If the rJrctrienJ cha)i(/e.< of the beating heart are investigated, it is found that the base becomes negative before the apex, and that this condition of negative potential pas.«es along in the form of a wave to the apex. Its speed has been found to average at lea.'Jt 50 mm. a second. The /(iteiit jtrriod of frog's heart-muscle is about 0.08 of a second, but the change of potential takes place instantly after the applica- tion of the stimulus. The excitation wave can be made to paijS S— Phys. 114 CIRCULATION. Fig. 11. s.r /// DiacTammatic representation of the course of cardiac auKmentor fibres in the frng (Foster) : T'.r., roots of vagus (and ninth) nerve, r/. T'., ganglion of same. Cr., line of cranial wall. TV/., vagus trunk, ix., ninth, glossopharyngeal nerve, .s. V. C, superior vena cava. Sy., sympathetic nerve in neck. G. r., junction of sympathetic ganglion with vagus ganglion .sending i. c, intra-cranial fibres, passing to Gasserian ganglion. The rest of the fibres pass along the vagus trunk. (Ji, splanchnic ganglion connected with the first spinal nerve. G", splanchnic gan- glion of the second spinal nerve. ^?i. T'., annulus of Vieussens. yl. «&., subclavian artery. G'li, splanchnic ganglion of the third spinal nerve. III., third spinal nerve, r. c, ramus communicans. The course of the augmentor fibres is shown by the thick black line. They may be traced from the spinal cord by the anterior root of the third spinal nerve, through the ramus communicans to the corresponding splanchnic ganglion f?'". and thence by the second ganglion G^^, the annulus of Vieussens, and the first ganglion G^, to the cervical sympathetic Sy, and so by the vagus trunk to the supe- rior vena cava S. V. C. THE in:.\i:r OJ. Fig. r_'. niiiKrainnialic reprcsenta- tiiin i>l" tlif ciinliiil iiiliiliitDry and aiiKiiU'iitor lil>ri-s in the i\i>ii. '\'\w uiipiT |H>riii>n >>( ilie ti^'iiri' ri'iircscnts tlic inliil>i- im-y, the luwor the iiunnK'nlor, lihrVs I Kosteri : r. l';/., roots of the \m;iis. r.S]i..\i\, roots of siiiniil iiceessory : hotli tirawn very iliiii^rununatieally. (i..l., Kiin^'liiiii jiij,'iilure. (i. 'Jr. \'(i'., unn^^Wiiu trunci vaji. Sji.Ar., spinal accessory trnnlc. cxt. >'/). .!<•., external" spinal acces- sory. i.Sii.Ar., internal spinal accessory. \'.;us nerve. ".''., l>ranelies troiliK to heart. ('.Sy.. cervi- cal sympathetic. G.C, lower cervical jran^jlion. ^I..'--/)., suli- clavian arterv. Aii.\'., annn- lus of Vieiissi'ns. G.SI. {T/i.h. f^anKlion stellatuin or first thoracic fian^'lion. G.TIi.-, (i.rh?, (;.rh.\ second, third, and fourth thoracic Kan.i,dia. I). 11.. I). III.. IKIV.. /^r., sec- ond, third, fonith, and fifth thoracic spinal lU'rves r.c. ramus comniunicans. n.c, nerves (cardiac) passing; to heart (superior vena cava) from cervical eannlion and from the annulus of Vieus- sens. The inhibitory fibres, shown by black line, run in the upper (medullary roots) of the siiiiuil accessory, l>y the internal branch of the spinal accessory, i)ast the ganplion trunci v'a^i, alon^ the trunk of the vagus, and so by branches to the sujierior vena cava and the lieart. The au).cnientc)r fibres, also shown \>\ black line, pass from the spinal cord by the anterior roots of Llie second and third thoracic nerves (i)f)Ssibly also from fourth and fifth as indicated by broken black line), i)ass the second and first (stellate) thoracic nantilia by the annu- lus of Vieiissens to the lower cervical (;"nuH<>n, from whence, as also from the annulus itself, they juiss alone the cardiac nerves to the superior vena cava. n.Tr.Vn 11 r.Vg. Sp.Ac. O.TliX 116 CIRCULATION. over the heart in any direction, and the speerf with which it travels indicates that it passes through muscle and not througli nerve. The duration of the pause or block in the frog's heart has been found to be from 0.15 to 0.30 of a second. The speed of the ex- citation-wave in embryonic muscle (3 to 11 meters a second) makes it plausible that in the lieart the block is due to the fact that the excitation-wave is transmitted through embryonic muscle- fibres that exist between the auricle and ventricle. It is found that when a heart is subjected to a series of stimuli it will respond regularly when the rate is slow, but when it becomes too rapid, the stimuli will not all be able to call forth a response. The heart- muscle loses its irritability during a part of its systole, and regains it during the remainder of the systole and the following diastole. During a part of the cardiac cycle, therefore, it is refractory to stimuli. A stimulus falling within the refractory period is without effect. A stimulus falling within the non-refractory period calls Fig. 13. l/\/lA/\/W\/L_.yvAAAA. Effect of stimulation of pneumogastric nerve upon action of heart in frog. To be read from left to right (Chapman). out a contraction, but does not disturb the rhythm of the heart, because it is followed by a pause of extra length. This is called the compensatory jmuse. The first systole after an extra contrac- tion and a compensatory pause is of marked strength. The nerves of the heart are branches of the vagus and the syvijMthetic. Some of the fibres of the vagus which are derived from the spinal accessory terminate in end-baskets which surround sympathetic ganglion-cells whose axis-cylinder processes end on the muscle-fibres. Other fibres of the vagus end in end-brushes in the pericardium and endocardium. Fibres of the sympathetic system arise from cells in the cord and pass out through the white rami, ending in the inferior cervical and stellate ganglia on cells whose axis-cylinder processes in turn pass either directly to the heart-muscle or to a third neuron lying in the heart. Stimulation of the vagus fibres along any portion of their path from the medulla to the heart inhibits the heart's action. The 77/a; ii/Airr 117 eHW't is not iinnuMlinte, l)ut follows u latent periofi which oxteuds oviT a lu'at or (wo. The inlilhifion inanifi'sts itself at first hy a leii;.ftheiiiii<; of the duralioii of (he diaslole without any ehanjre in the systole. A stronj,aM- sdniulation lengthens the .systole also, and may stop the heat of the heart altogether. Inhibition is further xlioH'tt hy a /('xsniinf/ oi' the force of the (•otilraction ; by an increase of ]>reKKurt' in the lieort during diastole; \)\ on increase in the amount of residual blood ; hy a decrease in the injtiit and oiifjtitt of the ventricle, and hy diminished ventricular tonus. It inav further he said that during vagus excitation the j)roj)agati(«i of the cardiac excitation is more ditiicnlt. A demarcation current tlerived from a jMjrtion of the auricle is increased by var/us excita- tion, although the auricle shows no visible change of form. The heart cannot be continuously inhibited by prolonged stimulation. Fig. 14. 'y.vA\z\\\z%%mmwMmmwmm/immm'aiivMMmmMv^ Effect produced by stimulatidU f)f ]< ripliernl cml nf tlu' iKcvliintiriK iutvl' of the heart. The licart beats mure quickly. Stiimilatiuii begun at >' ^LaudoJs). It e-scajies from the influence of the vagus and resumes its former rhythm with perhaps increased force. Immediate stitnulafiini of the second r«7».*i after the heart has escaped from the influence of the first is without effect, making it probable that both uerve.< act upon the same mechanism in the heart. Stimulation of the siimj»athetic or augmevtor fibres causes an in- crea.se in the rate of the heart-beat from 7 to 70 per cent., the amount of increase de]HMiding upon the heart's rate before stimu- lation. A lonff excitation jiroduces no (jreater acceleration than a sfitirt one. The force of the beat, the pjilse-ndume, and the sj)erd i)f the e.rcitation-u'ave are all increased. The latent ])eriod is usually a long one, extending from two to ten seconds. The accel- eration may continue for .several minutes after the excitation has ceasetl. It ha.s been found that pressure brought to bear U|M>n the human heart where a defect in the chest-wall makes it acces>i- 118 CIRCULATION. ble can be felt by the subject, and direct stimulation of the sur- face of the heart in animals may cause movements of the limbs. Vaaal or \ extra-canZ. infiid. centn Diagrammatic view of the nerves influencing the action of the heart. The right half represents the course of the inhibitory, and the left the course of the accelerating nerves of the heart: the arrows showing the direction in which impressions are conveyed. The ellipse at the upper extremity of the vagus looking like the section of the nerve is intended to represent the vagal nucleus or centre. In this diagram the nerves are incorrectlv made to cross, instead of passing behind, the aorta (Chapman). The latter event is absent when the vagi are cut, so that it is thought the vagus carries afferent fibred to the brain, Stimulation Tiih: iiF.Ain: I r.i of the oontnil end t)i" tlu- cut vaji:us when the other is intact slows the licarl-nilc. This cl led disappears when hoth vai^i arc cut. The ilej)re!ul does modify the force of the contraction. The varioK.'i condttuenU of the complex jiu id, blood, have diffrrint rnlueft in maintaining the activity of the heart. Tliis has been investigateil bv the use of nutrient solutions of definitely known comjtosition. The results obtained are briefly ad follows : Nutrient fiiiiy the addition of oxalate compounds, the heart cea.ses to beat, but spontaneous contractions return when calcium is again added. A well-known nutrient solution is Ringer .<, which is a mixture of 1(10 c.c. of a 0.(> per cent, sodium chloride solution saturated with tribasic calcium phosphate and 2 e.c. of a 1 per cent, solution of potassium chloride. O.njijen is essential to the ])rolonged activity i)f the heart. Carbon dioxide is injurious when present in large ipiantities. A heart poisoned with the latter substance shows an irregular aeries of eoidi'actions. It has not heen isatisfactorily de- monstrated that organic substances are immediately necessary to {\\v rhythmic activity of the heart. ARTERIES, CAPILLARIES AND VEINS. The continuously high /)rr.' VFISS. 1 L'.'} wall of the vessel, which, through its elasticity, tends gradually to return to its normal size during every diastole of the heart. It is at all times, however, stretched, and therefore always exerts a pressure upon tiu' blood within. Under normal condition.s the amount of lilood accommodated l)y the yielding artery during each systole is eipial to the amount that passes from the arteries and to the capillaries during tiie diastole of the heart. Each in- crease of pressure' caused by the heart-beat is propagated in the form of a wave through the arterial system, and constitutes what is called the jiulxr. The pressure in the capillaries and veins is caused by the same factors that are present in the aorta — power of the /(rar<, reaixtance oi' friction, and c/nxtirifij of hlDodvexsrl-ivall'^. But in the cajnlla- rirs and rciii.s their is no jmlxr and the jjirxfutre is lotr. The cau.se of the latter becomes obvious when it is taken into consideration that a part of the force of the heart has l)een lost in overcoming the friction of the bloodve.-^sels. In addition, the friction which the blood has yet to overcome in its passage back to the heart is but a fraction of the total friction which it encountered at first. Diminished resistance ahead means lowered pressure. The blood in the capillaries has become pulseless, because the elasticity of the arteries displaces the blood in the capillaries at the same rate that the systole of the heart does. There are siihxirJiani forces that assist the heart in propelling the blood. Among these may be mentioned the coniractionx of the skelefnl miixclex, the constant jmll of the Jibrcx of the lumj, and the movemenU of rexpirafion. The muscles, in contracting, press upon the veins moving the contained blood onward, since the valve? prevent all back-flow. The fibres of the lungs, through their elasticity, are constantly pulling upon the walls of the heart and the large veins, which "tends to draw the blood into them. This effect is increased with each inspiration, and the blood then rushes in at a (juickcr rate ; during the following exjnration the blood flows more slowly again. There may in this way arise a diMinct pvhe in the large revovs vexHels of the ched, which may extend along the rcivx to the root of the vrck. In this region, in deep respirations, there may be an intermittent flow of blood from a cut vein. The Ideeding occurs during each expiration and ceases during each inspiration, when the blood is sucked past the Wounil and not jircssed out of it. Owing to this reason air may 124 CIRCULATION. be drawn into the vein, an event which causes immediate This region is, therefore, known as the dangerous region. death. Trace of the radial pulse taken by the sphygmograph (Daltoii). By the term arterial pulse is meant the fluctuations of arterial pressure that correspond to the beats of the heart. The pulse is dependent upon : 1. The contractions of the heart. 2. Upon the resistance produced by the friction of the blood in the vessels, o. Upon the elasticity of the bloodvessel-walls. An abnormal change in either of the three will modify its character. An artery not only increases in its girth as the pulse-wave sweeps over it, but also in its length, which can readily be seen when the vessel has a sinuous course. The increase in girth can be felt with the finger, and forms a constant means of diagnosis. The rate of the pulse-wave is from 3 to 9 metres a second. As the blood moves on an average in the arteries only a half metre in the same time, it is clear that it is not the travelling of the blood that produces Fig. 18. Dicrotic pulse of typhoid fever (Marey). the pulse, but a wave of pressure. A number of terms describe the character of the pulse. In regard to its tension it may be : Of high tension or of low tension. Incompressible or compressible. Hard or soft. Very hard (wiry^ or very soft Tgaseous). JSigh tension is indicative of high blood-pressure, and can be AriTi:nir:s, capiilmiiks .ixn veins. 12;', liU'iisiin'd 1)V a s|ili\ ir'iiiiiiutcr. In iciranl In its sizr the pulse niiiy 1)0 : Larj^c or small. Very larj^e (l)oun(lin>j the .tudilrn chh'fure of the ■'.(• of a second in a (a|iillary •] mni. Ions:. The pulmonary circulation ilitiers in minor res|)ects from the siisfi-itiir. The total j'rirlioii is Icsh, m correspondence with wliicli the riijht ventricular walls are far thinner than those of the left ventricle. Owinj; to the fact that the pnlmoimry .■<- sumed, therefore, that centres exist in the cord which normally are control lc V. respectively the second and (ifth dorsal nerve : Av. V. anntdus of Vieussens. The patlis of the constrictor fibres are shown by tbcarrows The dotted line in Itie spinal cord, S'p. ('., is to indicate the passage of constrictor impulses down the conl fr^m the vaso- motor centre in the medulla. 130 CIRCULATION. related. Thus stimulation of the tongue causes dilatation of the vessels of the submaxillary gland. There is no sufficient evidence of the existence of vasomotor centres in any portion of the brain except the bulb. The fact that stimulation of the same nerve gives rise sometimes to a reflex dilatation instead of the more usual constriction, has given rise to the conception of special pres- sor and depressor fibres. The former constrict, the latter dilate. The cardiac depressor nerve is a good example. CIRCULATION OF LYMPH, The lymph, in moving from the tissue-gaps and lymph-capil- laries to the veins, passes from a point of relatively high pressure to one of low pressure. The pressure in the lymph-capillaries has been estimated at from 12 to 25 ram. of Hg. ; in the thoracic duct, near its entrance into the veins, it is very near to zero, and often is negative. In some of the lower animals there are separate lymph- hearts which act as force-pumps to drive the lymph on. In man such lymph-hearts do not exist, but the movement is brought about by other factors : 1. By the continual formation of new lymph. 2. By the muscular movements of the body compressing the lymphatics, which force the lymph on in the proper direction, the reverse flow being prevented by valves. The chyle is aided in its flow by the action of the muscular fibres of the small intestine and also by the contractions of the villi. In the mouse the chyle has been seen to flow with the intermittent movements corresponding to the peristaltic waves. The contractility of the ivalls of the lymph-vessels themselves probably aid the flow. 3. The thoracic aspiration of the chest on inspiration draws the lymph into the thoracic cavity in the same manner as it draws the venous blood. The movement of the lymph is, without doubt, irregular, but in the course of a day a considerable amount is poured into the veins. An accumulation of lymph in the gaps of the tissues constitutes dropsy, and such tissue is said to be ocdemor tous. A substance in solution injected into the blood can be de- tected at the mouth of the thoracic duct in from four to seven minutes. QUESTIONS OX CIIAPTFJi Mil. 131 QUESTIONS ON CUAPTEK VIII. Give the path of the I»1(«mI throuuli thi- body. Givi- the putli of thi- hliuKi lliniu;ih tho jioital systfUi. Wluil is iiicaiil l)y ■' ciii-iilation uf ilir hlood"'? What I'liiiiiiun is I'lillilKd l>y the ciiriilatiuii ? Wlii-nci- iliM.',s the lioarl ilerivc il.s uMt-rgy ? Dcliiie systole and diastule. By wliat meaus is tlie hUnid forced in one direction only? How nnuh time is retiuiied by the hlood to eoniplete its eireiiitV What dilferent events take place during a cardiac cycle? What are the changes in the size of the heart due to? What is the contlition of the heart when relaxed ? What changes take place in the heart during systole when the thorax is open? How are these changes luoditied in the unopened chest? Give the changes of color of the heart during contraction. Why does the heart not move from the chest-wall during sj'stole? Where is the apex-beat felt? What is meant by "negative impulse"? Describe the sounds of the heart. With what portions of the cardiac cycle do they coincide? What is the cause of the heart-.sounds? Where can the sounds be best heard? Discuss the rate of the heart-heat. Describe the character of the contractions of the auricle and ventricle. Give the times involved by the various events of the cardiac cycle. What changes take place in regard to the time occupied by the cardiac cycle events when the heart-rate is quickened? Describe the action of the valves during a heart-beat. What is the pulse-volume? How is the iiulso- volume obtained? What is its value? How is the work of the heart calculati'd ? How are intraventricular ])ressures determined? How much work does the heart do in a day? What are the relative jiressures in ventricle and aorta? Discuss endocardiac pressure curves obtained from ventricle with different methods. What are the oscillations of tho plateau due to? In what way may the times of closure and opening of the valves be ascer- tained on intracardi;ic jire.ssure-cnrves? Define "period of reception" and "period of ejection." Discn.ss periods of complete closure of the ventricles. fan the ventricles alone niaintain circulation? What is the function of the auricles? What variations in pressure arc there in the auricles? DiscMiss the entrance of the blood into the auricles from the veins. Discuss the cause of the rhythmic activity of the heart. What is the "cardiac excitation wave"? Where does the contnK'tioii of the heart begin? What is the effect of tying a ligature about the aiiriculoventriculargroove? What is the speed of the cardiac excitation wave? WTiat is the latent period of the frog's heart-muscle? What is the time- value of the block of the heart's contnu-tiou? 132 CIRCULATION. What is the cause of the block ? Give evidence. What is meant by the refractory period of the heart^beat? Define compensatory pause. What are the sources of the nerve-fibres to the heart? Describe their course. Discuss the effect of stimulation of the vagus on the heart-beat. How does stimulation of the vagus afl'ect a demarcation current from the auricle ? Discuss the end-apparatus by means of which the vagi inhibit the heart. What is the eflect of stimulation of the augmentor fibres on the heart-beat ? Give the lengths of the latent periods of inhibition and acceleration. What evidence that afferent fibres run from the heart to the central nervous system ? Discuss the function and the effects of stimulation of the central cut end of the depressor nerve. Are the vagi and depressor nerves continuously active ? How do weak and strong stimulation of sensory nerves affect the heart? What effect has dilatation of the stomach on the heart? Discuss the situation and action of the cardio-inhibitory centre. Discuss the action of the accelerator centre. Where are the ligatures of Stannius placed, and what effect do they pro- duce? What is the peculiarity in the distribution of bloodvessels to the heart? What is an infarct ? How does the antemia resulting from hemorrhage differ in its action from that caused by ligating the coronary artery ? How do the contractions of the heart favor the entrance of blood into the coronary arteries? In what ways does the blood-supply to the heart affect its beat? Discuss the constituents of the blood that cause the rhythmic activity of the heart. How do the actions of potassium and calcium salts differ? What is Ringer's solution ? What effect has carbon dioxide on the heart? Why does the blood move from the arteries to the veins ? How is blood- pressure measured ? Describe a mercurial manometer. What is the form of blood- pressure curves obtained from an artery? What is meant by mean blood-pressure? What are the mean blood-pressures in arteries, capillaries, and veins? What is the cause of the high pressures in the arteries? What are the causes of blood -pressure in capillaries and veins? Why does the pressure decline from arteries to veins? Why is there no pulse in the veins? Discuss the action of subsidiary forces that aid the heart in circulation. What is the pulse ? Its cause ? How does the character of the pulse vary ? What is a spbygmogram? What is the dicrotic wave ? Its cause ? How are rapid changes in the velocity of the blood measured ? Give the rate of flow of the blood and the causes for its variations. How long does the blood remain in the capillaries ? How does the pulmonary difl"er from the systemic circulation? What governs the distribution of the blood in the body ? JUCaVl RATION. 133 What urc vasomotor libns? (Jive proofs that tliij' exist. Are vasomotor lilircs iircsont in Vfiiis? (live tilt' miaiis ol' (lisUiiKnisiiiiiK lu-twifii dilator ami constrictor fibres. Discuss IIk- location of the vasomotor cent re and its commnnicatiuiis. What is till' ovidcncf that siiinal ami symiiallu-lic vasomotor centres exist? What are Tranhe-Ilerinj; waves and their cause? I low do vasomotor rellexes arise? What are pressor and depressor lihres? Discuss the factors that cause tlic llow of the lymph. What constitutes ilropsy ? What is the rapidity of the lymph circulation? CHAPTER IX. RESPIRATION. The expression resplrafiom\Xi\n'\xcQs two distinct ideas. It may mean the entrance of oxi/gcn into and the exit of carbon dioxide Iroin an animal, or it may have reference to the visceral — muscu- lar and pulmonary, etc. — movements by which these f/ases are caused to fow in and out of the Innrj.^. The lungs of man are of vital iin])ortance in the interchange of oxygen and carbon dioxide, while the tkin is of but .■inhxidianj importance. This condition of affairs is reversed in the frog. The hmfjs consist of an enormous number of air-vesicles or alveoli which communicate by means of a series of passages with the trachea and the external air. Their total area is more than one hundred times the superficial area of the skin, and their walls form a delicate partition in intimate rela- tion to the blood^capillaries of the htnci. Before birth the liin(is are airle.^s {atelectatic), but after having once been expanded, they never regain their atelectatic condition, becau.se during col- laji.-'c the pas.-^acjes cloxc fir.4 and so imprison some air in the alveoli. The Imigs are enclosed in the air-tight thorax, and sepa- rateil from its walls by a double layer of jdeiira. The thora.r of the child grows faxter than the hnujx, so that the latter become didended in an air-tight cavity. Whenever the thorax is o]iened, the lungs, owing to the ela.dieiti/ of their structure, immediately shrink together. It follows, therefore, that the lungs are always tentling to shrink and thus jniUing away from the thoracic walls and didplinirpn. This produces a prcx.'nire in the pleural cavity below that of the aimoaphere, and it is called a negative pressure 134 RESFIBA TION. whenever atmospheric pressure is regarded as a standard. The negative pressure has been found to vary greatly under different conditions, but may be put at minus 6 mm. of Hg at the end of a quiet expiration, and at minus 9 mm. of Hg at the end of a quiet inspiration. During forced inspiration the value may reach minus 40 mm. of Hg. The pressure in the pleural cavity — i. e., outside of the lungs and within the thorax — is known as intra- thoracic pressure, while that within the lungs and respiratory passages is called the intrapulmonary pressure. The variations in pressure are caused by changes in the capacity of the thorax, which may enlarge in all directions. It is obvious that when the thorax increases in size the decreased pressure within causes the entrance of air from the outside, where it is at a higher pressure. The air rushes through the trachea and inflates the lungs. This constitutes an insjnration. The opposite process, or an expulsion of air by a decrease in the size of the thorax, is expiration, and both together form respiration. The lungs during respiration are entirely passive, and merely follow the thoracic walls because the atmospheric pressure acting on their inner surfaces is greater than that between the lungs and the thoracic walls. The pleurae are moistened with lymph, and slide over each other without fric- tion. Inspiration is an active process brought about by certain mus- cles which, by their action, enlarge the thorax in a vertical, anteroposterior, and lateral direction. The upper part of the thoracic cage being fixed, the vertical diameter is increased by the descent of the diaphragm in contracting. Other muscles act on the ribs, so that they turn on their axes, with the result that their sternal ends are raised up and carried forward, enlarging the anteroposterior diameter; at the same time the direction of the axes of the ribs causes them to rotate outward and upward, so in- creasing the lateral diameter. The chief muscles of inspiration are the diaphragm, the scaleni, the serrati postici superiores et infe- riores, the levatores costarum breves et longi, and the external intercostals and interchondrals. The diaphragm projects into the thoracic cavity in the form of a flattened dome. During contrac- tion it descends from 5.5 to 11.5 mm. in quiet respiration, and about 42 mm. in deep inspiration. There is a tendency for the dia- phragm to pull in its points of attachments — the lower ribs, with their cartilages, and the lower portion of the sternum, but usually RESPIRA TJ'jy. 135 this is counterbalanced by the pressure of the abdominal viscera. The ."•errati po.slici iiit'eriore.< assist the (liaphra;zni by fixing the ninth, teiitli, eleventh, and twelfth rii»s. Tlie sealeni lix the fir>^t and second ril)s. The serrati postici .^nperiores? help to fix the second rib, and raise the thirer tension. During /brcerf iiispiration additional muscles are brought into play to i)ermit a more powerful inspiratory act. Besides the muscles already enumerated, the following are brought into play: The trapezei and rhoniboidei fix the shoulders ; the pect. The rair of respiration vurietj with the most diverse internal untl external eonditions. In tiie normal adult the rate is about 18 cycles a minute when the l)ody is in repose. Tlie ratio to the pulse-rate may be put at 1 : 4. During quiet respiration tlie inflow and outllow of air, wiiich amounts to about aOO c.e., or 30 cubic inches, is known as the tidal air. It does not go lower than the large l)ronchi. The volume of expired air, owing to its increased temperature, is greater than that inspired, but the actual quantity is less. ( 'omjtlonoda/ air (about 1 iJO{) c.c.) is the amount that can be inspired after an ordinary iuspiratiou. Fig. 22. Tracinp of thoracic respiratory movements obtained by means of Marey's pneu mograph (Fostcrt. A wliole respiratory jiliase is cvjinprised between n and a ; in- spiration, during' which the lever most forcible ins|)iration, and is equal to the sum of the vital capacity and re- sidual air (4500 c.c. ). It may caMly be ca/eii/alcd that man in tn'ody-faur hours respires about 10,800 litres of air, which is equal to a space 71 feet in three dimensions. The ratio of the quantity of (jxygen absorbed 138 BESPIBATION. to the carbon dioxide given off is known as the respiratory quo- tient. While in the lungs the air loses 4.78 volumes of O^ in 100, and gains 4.34 volumes of CO^ in 100, so that the value of the 4.34 . respiratory quotient, , is equal to 0.901. This value is subject to great variations, because the production of carbon dioxide is to some extent independent of the amount of oxygen absorbed. This is so for several reasons : 1. COj may result not only from oxidation changes, but from intramolecular splitting, so that the elimination of CO^ in normal quantity may continue when absorption of 0^ has entirely ceased. 2. Some food-stuffs require more O^ for their complete oxidation than others. The air during its sojourn in the lungs is altered in addition to its Og and CO^ contents by assuming the te^nperature of the body, regardless of the teviperature of the outside atmosphere ; by an increase of its aqueous vapor ; and by the jwesence of volatile organic bodies. The nitrogen remains unchanged. The quantity of tvater lost by the lungs varies inversely with the amount in the atmos- phere, and directly with the quantity of air inspired. The blood in its passage through the lungs becomes aerated. The O^ and COj in arterial and venous blood together form about 60 volumes of the blood in 100. The proportions of the gases to each other are constant in the arterial blood, but vary in the venous blood in different localities. The oxygen of the air enters the alveoli of the lung, passes into the blood through the delicate epithelial walls, and is carried to the tissues, where it is taken up by the cells. Very little is used up in the blood. The CO^ given off by the cells is carried to the alveoli of the lungs by the blood, and is there given off. But the air that is inspired does not reach the alveoli directly, because the lungs are never completely emptied of air. It becomes necessary, therefore, to consider the methods by means of which the inter- change of gases is brought about. The air-currents that are set up mechanically probably help to equalize the composition of the air in the lungs. Besides, the heart with each contraction as it shrinks in size expands the lungs slightly and causes a movement of air into the chest synchronous with its beat. These are known as cardiopneumatic movements. In addition to the mechanical factors, the physical process of diffusion is of great importance. RESl'IlLlTloy. 139 The rapidity of diHusioii depemls, among other things, upon the dilii'r(Mi<'i.'H ot" the partial pri'ssiires of the gases in various regions. If the total atmospheric pressure is 700 mm. Ilg and ().^ forms 1^ of the gaseous constitueuts of the air, then it will exert a press- ure of its own equal to i of 7G(), or lo2 mm. Hg ; and carhon dioxide, forming 0.04 volume in 100 of the air, will exert a pressure of of 760, or about 0.30 ram. Ilg. It has heeu esti- mated that tiie partial pressures of O^ aud CO„ in alveolar air are equal to 100 and 2o mm. Hg, respectively. The difiereuces in partial pressures, therefore, will cause O.^ to diffuse toward the alveoli, aud CO., from the alveoli to the outside air. The f/nxe:^ in the blood are not only in solution, but also in weak chemical combination, so that diffusion from the alveoli into the blooil and vice versa is somewhat com[)licated. The amount of a gas that is absorbed when lirought in contact with water depends upon the relative solahilifii, the temperature, aud the baronidric pressure. Eacli, of a mixture of gases, is absorl)ed independently of the others. The relative solubility is expresseil by the coeffi- cient of a6.sor/j/io/i of the fluid, which is experimentally determined, and is found to be in inverse ratio to the temperature and in direct relation to the pressure. The absorption-coefficient of water for O^, as an example, at zero C/entigrade and 7()0 mm. pressure, is equal to 0.04S9. This means that under the given conditions of temperature and pressure 1 volume of water will take up 0.04S9 volume of O.,. Since, however, the O., forms but i of the quantity of the air, water will absorl) from the atmosphere only i of 0.0489 volume, which is equal to 0.009-f , or nearly 0.01 volume. As the partial pressure of O^ is raised or lowered, O., will leave or enter the water, so that the gas in solution is said to be under ten- sion. The absorption-coefficient of blood for O., is about that of water, but at the bodily temperature is decreased to less than i. Every volume of blood should, therefore, contain •' volume of oxv- gen in 100 ; but experiment shows that there is much more present. Upon subjecting blood to a vacuum, O,, is given ofl' according to the laws of partial pressures and tensions until tiie pressure is lowered to -,',y of an atmosphere. From -J^ to ^^ of an atmosphere the great bulk of ()., is given off. Below ■^^, physical laws, as given above, again prevail. The explanation of this is that the O, is held in chemical combination with the hiemoijlobin, antl is 140 RESPIRATION. set free at J^ to ^^ of an atmosphere. This pressure is termed the tension of dissociation. Venous blood contains 45 volumes of GO^ in 100. Of this, 5 per cent, is in simple solution ; 10 to 20 per cent., in firm chemi- cal combination ; and 75 to 80 per cent., in loose chemical combi- nation. The largest amount is connected with the red blood-cells. While the CO^ absorbed by water increases regularly with the increase of pressure, that absorbed by solutions of hsemoglobin is relatively large for low pressures and small for high pressures. The quantity in the blood is in excess of what physical laws will permit. It is found that the partial pressures of O^ and CO^ in venous blood are about 22 and 41 mm. Hg, respectively. Com- paring the pressures of 0^ in the lung, alveoli, blood, and tissues (152, 100, 22, 0), with those of CO, (0.3, 23, 41, 58), it is seen that Oj and CO, will diffuse in opposite directions. Pure oxygen at a pressure of 1 atmosphere may be breathed without injury. At higher pressures it acts as an irritant and produces inflamma- tion. When less than 13 volumes of oxygen are present in the air in 100, it is insufficient to maintain the life of man. Pure COj is fatal in from two to three minutes. N, H, and CH^ cause no inconvenience if sufficient O^ is present. Nitrous oxide and ozone produce ansesthesia, and finally death. Air containing 2 volumes of CO, in 100 is rapidly fatal. Eupnoea is normal, easy breathing. Apnoea is a condition of suspended breathing. Hyperpnoea is increased respiratory activity. Polypncea is a condition of deep, labored breathing. Asphyxia is characterized by convulsive breathing, followed finally by infre- quent and feeble respirations. Apnoea can be induced in man or animals by rapid, deep respiratory movements or by forcing air into the lungs with a bellows. It is brought about by using pure 0, or H., ; lasting for a longer time when the former is used. But the fact that it can be produced with H, shows that the condition can- not be due to a superabundance of 0, in the blood. When the vagi are cut, H, no longer brings about apnoea. It is believed that in the violent inflation of the lungs the sensory endings of the pneurnogastric in the lungs are stimulated, which produces a temporary paralysis of the respiratory centre. The increased amount of O, in the alveoli and blood, however, prolongs the condition. Hyperpnoea is produced usually by the products of muscular activity which excite the respiratory centre. The nature ni:si'i!:ATf(>y. Ml of thc-^e products is unknown, l)ut tlie «lecTeas((l alkalinity of the blood iudirates that tlu-y may he of an aeid cliaracler. Polypnceu is due to direct stimulation of the respiratory ceutre throuirh the temjjerature of the hlood or throuj,'ii reflex excitation of cutaneous nerves. Dyspnua may he the result of a deficiency of U^, or due to an excess of CO.,, in the hlootl. Oxygen dyspn«ea is charac- terized hy frequent deep inspirations ; carl)on diijxide dyspud-a, by iufrequent, viirorous expirations. In the former, death is severe ; there is a marked rise of blood-pressure and violent con- vulsions. In the latter, death takes place more quietly, the bloofl-pressure rises less, and no motor disturbances are present. Cardiac and hemorrhagic dyspnoeas are due to a lack of 0^ chiefl}'. Asphyxia is divided into three stages — 1. One of hyperpua^a ; 2. One of dyspnwa and convulsions ; 3. One of collapse. If asphyxia is brought aliout by ligating the trachea, the proc- ess lasts for four or five minutes. The first stage lasts one min- ute, the second a little longer, and the third from two to three minutes. If produced by a very gradual deprival of 0.„ there may be no motor disturbances. In the fii-st stage the respirations are increased in depth and frequency. Inspiration is pronounced. During the second stage expirations become violent and convul- sive. During the third stage respirations are shallow, the pupils dilated, motor reflexes disappear, consciousness is lost, convulsive twitches are present, the limbs are stretched and rigid, the head and body arched backward, and finally the heart ceases beat- ing. During the first and second stages the gums, lips, and skin become blue, the heart-beats are less frequent, and the blood- pressure is increased. During the third stage a general depres- sion ensues. After death the hlood is almost black, the arteries empty, and the veins and lungs congested. Death from drowning is due usually to as|)hyxia, but sometimes is due to a cessation of the activity of the heart. The rf.--jtiraton/ morrmenfs have a marked effect ujioti the blood- pres^nre. In the carotid artery with every ins|)iration it rises, and with every ex))iration it falls (Fig. 23). The two events are, however, not exactly synchronous, the pre.piraliirati<>ns become vigorous. When, however, the cnmviissunil fibres are intact, excitation or i))}iibition of one side afj'erts the otjier as well. After section of one vagus, for instance, the respiraiiunx are slower and the inspirations stronger on both sides. Excitation of the central end of the cut nerve increases the respiratory rate of both sides. Each half of the centre is divided into an inspiratorij and an expiraforti portion. Weak stimulation of the i)ixpirator;i part increaxex the rate of breathing, while a strong sfimnlatio)i arrests respiration in the insjiirator;/ pha.se. Stimulation in like manner of the expiratory part of the centre diminislies the rate, and finally causes an arrest in the expiratorv jiiiasc. Ollirr rrspiraton/ centres have been described. One in the tuber cinereum, known as the polrjjmo'ic centre, is excited by a high crternal temperature, and causes a very rapid rate of breathing. Destruction of the 144 RESFIRATION. tuber ciuereum stops all acceleration by heat. A centre in the optic thalamus in the floor of the third ventricle is excited by im- pulses from the nerves of sight and hearing. It is an accelerator centre. Centres have also been described in the anterior and posterior corpora quadrigemina and in the brain-cortex. The existence of these, as well as of those described in the cord, is doubtful. After section of the cord in the cervical region, of the posterior roots of the cervical spinal nerves, of the medulla from all parts lying above it, of the vagi and glossopharyngeal nerves, the respi- ratory movements still continue, which indicates that the centre is automatically active. The rhythm may be affected by the ivill and by the emotions, by the quality and the temperature of the blood, and by afferent impulses coming over various nerves, but particu- larly the tenth. Section of 07ie vagus slows and deepens the respiration. Stimulation of the central cut end with stimuli of proper strength restores the rate, if it does not further increase it. It is believed, therefore, that while the blood alone may bring about rhythmical discharges, these are controlled by impulses coming over afferent nerves. Among the latter are the fifth, ninth, tenth, and various cutaneous nerves. Excitation of the superior laryngeal fibres causes increased expiratory movements, and perhaps an arrest in the expii-atory phase. Excitation of the glossopharyngeal nerves has a similar effect, but the inhibitory influence lasts for three or four successive respiratory acts. Irri- tating gases affect the trigeminal nerve-endings in the nose or the endings of the tenth nerve in the larynx and lungs. The effect of the excitation of the cutaneous nerves may be seen in a cold douche, which primarily increases the respiratory rate and may cause its cessation. The efferent respiratory nerves are the phrenics, which supply the diaphragm ; certain spinal nerves supplying respiratory mus- cles, as the pneumogastrics. Section of one phrenic causes paraly- sis of the diaphragm on the corresponding side. Section of the cord just below the fifth cervical nerve stops the costal movements, but does not affect the diaphragm, because the nuclei of origin of the phrenics lie just above the section. If the section had been placed somewhat higher, respiration ceases entirely, but the asso- ciated movements of the larynx and face continue. During /orcec? breathing the facial, hypoglossal, and spinal accessory nerves are /v'A'.V/V/M 770.V. 145 culled into action. Diiriiiu^ iifrriiic life the rrxjtiraionj reiifre is in jin iijiiKcif condition, on account ot" a loiv Irrilnhi/ifi/ of tlic rrxj/i- Kitonj centre and the lar^c amount, relatively, of oxy<,a'n in the l)loo(l. Cases have iii-en seen in which the child has made respi- ratory etibrts while within the intact fcetal niemhruues. Such au attem|)t draws some (»f the anniiotic fluid into the nose, causing inhibition of all further efforts. After birth, iclien xjKinfaiieon.i rexpinition ix about to take place, it ix well to roiwre all in urns or other matter from the iioxe, to avoid inxpiration of them. The nerves which are distributed to the linif/ tixxne are the piieiimoyaxfricx, xijntpathetic, and dorsal nerves. Among the jineumogastric fibres are broncJioconstrictors and bronchodilatorx. Excitation of one vac/us causes a constriction of the brouchi of both lungs ; section of the nerve causes a dilatation of the bronchi iu the corresponding lung ; stiviulation of both peripheral and central ends of the cut nerve causes constriction of the bronchi of both lungs, which is more pronounced with the stimulation of the peripheral end. Asjthi/xia causes bronchoco)ixfrlctioii, ])nt not after the vagi are sectioned. The sympathetic fibres are trophic and vasomotor in function. There are a num])er of involuntary and voluntary special respiratory acts, largely reflex, which result from modifications of inspiration and expiration. Sighing. — This results from a prolonged inspiration, the air passing noiselessly through the larynx and being expelled rather suddenly. Hiccough. — This resembles sighing, but the inspiration is sudden, due to a spasmodic action of the diaphragm. Cough. — This results from a deep ins]>iration followed by a forced and sudden expiration, during which the glottis is closed momentarily by the s|3asmodic action of the vocal cords. Sneezing. — In this case after a deep inspiration the air is di- rected through the nasal passages by a sudden and forced vxytx- ration. Speaking. — In this case there is a voluntary expiration, ami the vocal cords ])eing rendered tense by their musch's vibrate as the air passes over them, proilucing sound. Singing. — This varii'S from speaking only iu the dificring ten- sion and position of the vocal cords, and the consequently difierent sounds produced. 10— Phys. 146 RESPIRATION. Sniffing. — This results from rapid repeated but incomplete nasal inspirations. Sobbing. — Tiiis consists of a series of convulsive inspirations, during which the glottis is more or less closed. Laughing. — This results from a series of short and rapid expi- rations. Yawning. — This is an act of inspiration more or less involun- tary accompanied by a stretching of various facial muscles. Sucking. — This is caused chiefly by the depressor muscles of the OS hyoides, which, by drawing down and back the floor of the mouth, produces a partial vacuum in it.. QUESTIONS ON CHAPTER IX. What two different meaniugs are included in the term respiration? What purpose do the lungs of man serve ? What is the total area of the alveoli of the lung? What is the condition of the lungs before birth? What are inspiration and expiration ? Why do the lungs follow the walls of the thorax? In what directions is the thorax enlarged in inspiration ? Why does the air enter the lungs in inspiration ? Tell in detail by what mechanism the thorax is enlarged in inspiration. What are the chief muscles of inspiration ? Give the action of each. How is expiration brought about ? Give the action of the muscles of forced expiration. What are associated respiratory movements? Describe the character and significance of respiratory sounds. What is the force of the respiratory muscles equal to? What is the value of nasal breathing ? Describe a respiratory tracing. Describe the Cheyne-Stokes respiration. What are the relative lengths of inspiration and expiration ? What is the rate of breathing, and how is it varied ? Define and give values of tidal air; complemental and supplemental air; residual air and vital capacity. What is the stationary air equal to ? What is the lung capacity ? What volume of air passes through the lungs of man in a day? What is the respiratory quotient? Explain why it varies. How is the air altered in the lungs ? How does the quantity of water vapor given off by the lungs vary? How is the carbon dioxide held in the blood? What is the evidence that CO2 is held in chemical combination? Compare the partial pressures of O2 and CO2 in the external air, alveoli, blood, and tissues. What is the efl'ect of breathing pure oxygen ? Give the effects of breathing other gases. QUESTIONS OX ClIAPTKn fX. 147 Define the terms— eupucea, apnuea, liypcrpua'a, polypna'a, dyspncea, aud asi)h.vxia. Discuss apna^i and its eanses. IIiiw is liyperiUKi-a i)r(ithiced? lli(\v is iiolyjind'a produced? Wliat is dy>piia-a dnc to',' Discuss asjihyxia in detail. What is (hath l)y drowuinK due to? (Jive the tiiiie-rehilions of the respiratory movements to the respiratory hiood-pri'ssure chaiij;es. Kx])iain in detail how respiratory movements produee changes in blood- ])ressure. What are the changes in the heart-rate during respiration? Discuss the resi)ii-iUory centre in the medulla. What can he said of other resi)iraliiry centres? What is the proof that the bulbar resi)iratorj' centre is automatically rhythmic? What happens to the blood in its passage through the lungs? What is the amount of O2 and CO2 in the blood? What factoi-s bring the O2 of the air to the alveoli of the lung? What are cardiopiieuiiiatic movements? Exjilain what is meant Ity the jtartial pressure of a gas. Exi>lain iu detail the diti'usion of O2 from the outer air into the alveoli. In what ways are the gases of the blood held ? W'hat factors govern the amount of a gas ab.sorbed by a liquid? What is meant by the coefficient of absorption ? What is the absorption-coetHcient of serum? In what way is the gas in the blood under tension? How much oxygen should the blood take up according to physical laws? Does it in reality hold more or less? How is the discrepancy explained? What is meant by tension of dissociation? How may the respiratory rhythm be affected? What is the effect upon the respiration of sectioning the vagi? Of stimu- lation of the central end? What are the aflferent nerves that control the activity of the respiratory centre? What is the effect of excitation of the superior laryngeal and glossopharyn- geal nerves ? Through what nerves do irritating gases affect respiration? What afferent nerves are involved in respiration? What is the effect of sectioning a phrenic ner%e? Give the effect of sectioning tlio cord just below the fifth spinal nerve. Discuss the condition of the res]>iratory centre in the frctus. What nerves are distributed to the lung tissue ? Discuss the kinds of filires in the vagus which are supplied to the bronchi. Wliat does stimulation of the central and peripheral ends of tiie fibres l>ring about? Define — sighing, hiccough, cough, sneezing, speaking, singing, sniffing, sobbing, laughing, yawning, and sucking. 148 ANIMAL HEAT. CHAPTER X. ANIMAL HEAT. Warm-blooded and cold-blooded animals are respectively designated as homothermous and poikilothermous. The former have a body-temperature that varies very little from a certain normal which is characteristic for the species, while the temperature of the latter varies directly with the medium in which they live, although usually from a fraction to several degrees higher. Man is warm-blooded — the normal temp)erature being about 98.5° F. (37° C). The temperature is not invariable, and in the internal organs may be as high as 100° F. under normal conditions. In the rectum the temperature is about 1 degree F. higher than in the mouth or armpit. The warmest blood in the body is that com- ing from the liver during digestion, and the coolest is that comwig from exposed parts, such as the tips of the ears and the nose. In health the temperature varies slightly with the external temperature, age, exercise, sex, constitution, etc. The temperature of a newborn child is about 37.86° C. In the adult there is a diurnal variation of 1 to 1.5 degrees F. ; being lowest in the morning and highest late in the afternoon. This corresponds to the usual temperature-ranges in fever. In ordinary pathological conditions the temperature does not remain long at a point below 95° F. nor above 105° F. without fatal results. Under conditions of prolonged exposure to cold and the algid stage of cholera, recovery has occurred after a bodily temperature as low as 75° F. On the other hand, in some cases of extreme fever, as from sunstroke, recovery has been noted after a temperature of 110° to 112° F. It has been proved that the source of animal heat is the potential energy of the foods. The latter is converted into heat either directly as the result of chemical decompositions or indirectly through muscular movements, friction, etc. About 90 per cent, is formed directly. The heat liberated by an animal may be meas- ured by calculating the potential energy from the food ingested or from the amounts of oxygen absorbed and carbon dioxide given off. This is indirect calorimetry. Direct calorimetry consists in meas- uring the heat directly by means of a calorimeter. A calorimeter is an apparatus by means of which the amount of heat given off ANIMAL HEAT. 149 bv an anirnjil may be luea^juriHl. It usually consii?ts of two cou- ceutric c'a.erature of the calorimeter 10 degrees C, the (juantity of heat that it has given otf would be equal to 10 times the calorimetric equivalent, or to 350 kilogramme-tlegrees. The quantity of heat given to the air is determined by measuring the amount of air passing through the calorimeter, and its temjierature on its entrance and exit. The volume of the air must be corrected for the increased temj>erature and then reduced to weight, after which it is multi{)lied by the sjiecitic heat of air at 0° C, and then by the number of degrees of the increase of temperature. By ■•^prcijic heat is meant the heat required to raise the temperature of any substance 1 de- gree C, and is usually compared to water as a standard. The specific heat of the animal body is about 0.8. The formula for the correction of the volume of air is : V P 760 (1 -^ 0.003665O * V is ob.*ervefl volume at 0° C and 760 nmi. Hg ; T', dei^ired volume at 0° C. and 760 mm. Hg ; P, observed pressure ; antl /, mean temperature. The value of 760 ( 1 -\- 0.0086(>5 ) is ol> tained from standard tables while the barometric pressure and aqueous tension are omitted, being too small to produce apprecia- ble error. A litre of dry air at 0° C. weighs 0.0012113 kilo- gramme. 150 ANIMAL HEAT. The measurement of the aqueous vapor of the air before enter- ing and after leaving the calorimeter gives the data for the estima- tion of the heat lost through evaporation. If it is found that the total quantity of water evaporated from the animal is 100 grammes, it is only necessary to multiply by 582 (since it requires this num- ber of calories to evaporate 1 gramme of water), in order to obtain the heat in kilogramme-degrees that is lost by evaporation. The principal part of the total heat produced by the body is generated by muscular activity. Subsidiary sources are the chemical action going on during diges- tion, friction of muscles, blood, warm foods, sun's rays, etc. In calorimetric determinations these are neglected. Throughout life the body maintains a constant temperature, so that there is a regulation of heat produced and heat dissipated. The production of heat is known technically as thermogenesis ; the dissipation of heat, as thermolysis ; and the regulation of the rela- tions between them, as thermotaxis. It is evident that if thermo- genesis and thermolysis vary together, the body-temperature will remain unchanged ; but an increase in thermogenesis with a con- stant or decreased thermolysis will raise the body-temperature. Further, a decrease in thermogenesis with constant or increased thermolysis will lower the body-temperature. The production of heat probably takes place in all the tissues of the body, since they all undergo oxidative changes, but the muscles are the main source of the heat not only when active, but when at rest. During activ- ity the greater part of their chemical energy is liberated as heat, only one-fifth appearing as mechanical energy. The work of the heart is entirely converted to heat, forming about 5 to 10 per cent, of the total amount produced in the bod3^ It is known that when a muscle is separated from the central nervous system it continues to produce heat, but much less than before. Specific thermogenic fibres have not been isolated. It has been claimed that the act of shivering has as its only purpose the production of heat, so that if the muscular contractions of shivering are brought about by im- pulses passing over ordinary motor nerves, they must have a spe- cific thermogenic function. The proofs of thermogenic ceritres are the following : 1. Excitation of the skin by heat or cold brings about changes in heat-production entirely independent of vasomotor changes. 2. Injury or excitation of certain parts of the brain is followed QUESTloys <).\ CIIAl'Th'R X. 151 bv increase*! heat-production ; excitation of other parts of the bruin, by u decrease of lieat-|)njduction. 8. Injury to tlie spinal cord brings alioul ciian<.'c.< in thenno- genesis without viUsoniotor disturbances. 4. Operations upon certain parts of the cerel)ro8pinai axis lead to an increase or decreiuse in tlie carbon dioxide excreted. Of tiie.se centres, those that increase tiiernio^enesis are called thermo-arrrlcrator centres, while those that diminish therniof.'enesis are called (Iwrmo-inJiilntonj centres. These two kinds act upou and govern a third kind of centre, called (jeiwral or automatic centres. The latter are located in the sjnnal cord. The thermo- accelerator centres probably exist in the caudate nuclei, pons, and bulb. The inhibitory centres have been located in the dog in the sulcus craciatus and at the junction of the nuprufujlvian and post- st/li'ian fiiisures. Ciianges in the external temperature or in the temperature of the blood affect the centres in the brain, which in turn act upon the general centres in the anterior cornu ol' the gray matter of tlie cord. Heat intiueuces the thermo-inhibitory, and cold the thermo-accelerator centres. Heat is lost by an organism through radiation and conduction from the skin, by the evaporation of water from the skin and lungs, and in warming food and inspired air. Thermoli/iiis is brought about by complex mechanisms. If the temperature of the bodv becomes too hi(/h, the actlritij of the heart is increased, peripheral vascular dilata- tion takes place, there are increased respiratory acfirify and secretion of ■•(iveat. These processes all tend to increase the losi^ of heat. When the external temperature becomes excessive, thennotaxis fails. Cold, for instance, may cause heat-dissipation to take place more rapidly than heat-px-oduction, so that the tem))erature of the body continually decreases until death ensues. The post-mortem rise of temperature is due to the fact that chemical activity will continue in the tissues for some time after the mechanisms of thermolysis have been rendered incompetent. QUESTIONS ON CHAPTER X. Define the terms honiotlu-rmotis and pnikilothcrmous. (live the bi>(ly-tciii)ieratiirc" of mail. In what ways ilncs it vary? Where are the warmest ami tlie cnhlest hlood of the body to be found? What factors iiillueiiee h()(ly-temi>erature? What is the source of tlie energy of heat? 152 NERVE AND MUSCLE. What percentage of heat is directly formed from the chemical energy of the food ? What are direct and indirect calorimetry ? Describe a calorimeter. Describe fully how the calorimetric equivalent is obtained. Why is it necessary to obtain the calorimetric equivalent in calorimetry ? Explain in detail how the heat lost to the air is calculated. What is the specific heat of a body ? Explain how the heat lost by evaporation of water is obtained. What organs are principally concerned in heat-production ? What subsidiary sources of heat are there? How much heat does the heart produce ? Define thermogenesis, thermolysis, and thermotaxis. Discuss thermota.xis. What is the eflect upon heat-production when a muscle is separated from the central nervous system ? Discuss the phenomenon of shivering. What is the proof that thermogenic centres exist? What classes of thermogenic centres are there, and where are thev located? •' How is thermolysis brought about? Explain the post-mortem rise of temperature. CHAPTER XI. NERVE AND MUSCLE. Most of the cells of the body in the division of labor have developed preeminently some one or other of the fundamental properties of protoplasm. Thus, muscle is characterized by con- tractility, but has not entirely lost the properties of nutrition, con- ductivity, and irritability. Nerves are characterized by their con- ductivity, but possess also nutrition and irritability. Both muscle and nerve in the adult condition have lost the power of reproduc- tion. The properties that they possess in common are irritability, conductivity, and nutrition. The phenomena of muscle and nerve can best be studied in cold-blooded animals. The frog's gastroc- nemius (Fig. 24) is usually the most convenient, and when the sciatic nerve supplying the muscle is dissected out carefully at the same time there results a nerve-muscle preparation. If the nerve of such a preparation is in any manner excited, the muscle re- sponds by a sharp and quick contraction or twitch. The excita- tion of the nerve has given rise to a disturbance of unknown nature in the substance of the nerve, which passes rapidly along NERVE AM) MUSCLE. 153 its length to the motor cvd-plalr and rrcitis tlio innxcle-jibre, which responds l»y its eharacti'rislic fit net ion, coiitniclioii. Tiiat muscle in irrilahh independently ot" nerves issliown in a number of ways : 1. Ihj the Curare J'Jx/xrtmciif. — Tiiis is made as follows : De- stroy the brain of a frog, hy pithing, and tie off all the structures of the left leg with the exception of the sciatic nerve. Inject a Via. 24. A muscle-nerve preparation (Foster): m, the nuisck', pustrocnemiiis of frog; n, the sciatic nerve, all the branches beinvrcut away except that sui>plyin>; the muscle ; /.femur; c^, clamp; /. n., tendo .Achilles ; .f;). c, end of s:>inal ciiuai. sufficient amount of curare solution to destroy the reflex ruove- nients of the right leg when the toe is pinched. U)ion trial it will he found that Ktinin/afion of the right i^rinti'- nerve when severed from the cord calls forth no movements, while rj-rltofion of the ff'ft .sciatic does cause movements of the corrospomling leg. TF7i''» the >ifimuhif< i.< applied ilirecthi to the »i (/.^'cA.s', theij both rrftpond. The drug curare has destroyed the motor end-plates. 154 NERVE AND MUSCLE. so that nervous excitation of the muscle can no longer take place and the muscle-substance is stimulated directly. 2. The sartorias muscle of the frog contains no nerve-fibres at its tips, which nevertheless are excitable. 3. The heart of the embryo beats rhythmically before nerve- fibres are developed. 4. Muscle whose motor nerve has degenerated as the result of previous section is excitable. When such a muscle, when dying, is struck sharply, there arises a local swelling, called an idiomus- cular contraction. An irritant or stimulus is any external influence which can Fig. 25. Diagram of an induction coil (Foster) : + positive pole, end of negative element ; — negative pole, end of positive element of battery; K, Du Bois-Reymond's key; pr. c, primary coil, current shown by feathered arrow ; sc. c, secondary coil, current shown by unfeathered arrow. ' excite living matter to action. There are five classes of irritants : mechanical, thermal, electrical, chemical, and physiological. The effect they produce upon living matter depends not only upon their efficiency, but also upon the irritability of the living material on which they act. The most desirable stimulus for experimental purposes is the electrical current, which produces very little injury and may be finely graded as to strength, time, and place of appli- cation. It may be either a constant or an induced current. The former, also called a voltaic current, is such as is furnished by any cell like the Grove or Daniell. The latter is obtained by the use of an induction coil (Fig. 25). This instrument consists NERVE AM) Mi'SCLE. 155 essentially of two coils of copper wire, one ofwlii<-h is placed within the other, hut htiirrcn irlilrh tlirre in no mclallir contirclion. The inner coil of heavy wire ( pmnanj roil ) is connected with a source of electricity, like a cell. The enrls (»f the outer coil (ncc- oiidanj coil), which consists of many turns of line wire carefully insulated, are connected with electrodes, hy means (jf which the induce< arise at the anode. Moreover, during c/cctrotoiim the co/i- FiG. 26. Muscle-nrrvc preparations: with the nerve exposed in ^1 to a desfCTifiinf/ and in B to an asrending constant current ' Foster). In eat-h, a is the anode, k the Itatliode of the constant current; x represents the spot where the induction-shocks, used to test the irritability of the nerve, are sent in. ductivify is increased slightly at the kathode, and decreased greatly at the anode. When the current ceases to flow, the conductivity is greatly lowered at the kathode and is raised at the anode. Re- flection will make clear that with an ascending current the closing contraction fails to apjiear because the conductivity is so lowered at the region of the anode that the excitation which arises at the kathode cannot reach the muscle With a descending current the opening contraction fails to appear because the comluctivity is so lowered at the kathode that the nerve-impulse generated at the 158 NERVE AND MUSCLE. anode cannot reach the muscle. The impulses that originate at the electrode nearest the muscle are the only ones that are effec- tive. At some point between the electrodes the region of increased irritability merges into that of decreased irritability. This point is nearer the anode, but with increase of strength of current it approaches the kathode. The facts relating to the effect of direc- tion of current on the resulting contraction constitute what is known as Pfiuger's law. Current-strength. Ascending current. Descending current. " Make." "Break." " Make." " Break." Contraction. Contraction. Contraction. Medium current . ^ Contraction. Contraction. Contraction. Contraction. When a nerve intact within the tissues of an animal is sub- jected to an electrical current, it is impossible to prevent the spread of the latter through the surrounding tissues. At the poi7it of entrance of the current it spreads out hrusli-lihe, to be concentrated again at the point of exit. Directly under the physi- cal anode the current enters the nerve, flows through it at varying angles, and so forms in the nerve a physiological anode and kathode. The same thing happens at the point of exit of the cur- rent. Therefore there are four points from which an impulse may be generated. There may be : 1. An anodic closing contraciion, which is the result of an im- pulse generated at the physiological kathode under the physical anode. 2. An anodic opening contraction, which is the result of a change developed at the physiological anode under the physical anode. 3. A kathodic closing contraction, which is the result of an im- pulse generated at the physiological kathode under the physical kathode. 4. A kathodic opening contraction, which is the result of an impulse generated at the physiological anode under the physical kathode. h'KItVK ASH MCSCLK. 1 oO These are al)l)roviat('(l, rc'S|M'<-tively, ACC, A()('. KCC, K()(". When the stiimihuiiiir ciirreiit is increased ;.'rali'niriif<. The ante- rior roots of spinal nerves whicii contain Hhres transmittini; normally in only one direction may he shown to transmit also in the opposite direction hy means of the electrical change accom- panying a uerve-im pulse. The rate of conduction varies in different tissues, and is roughly related to the function. In muscles all gradations are to be found, from the 0.02 to O.Oo metre per second of the smooth muscle-tihres of the rabbit's ureters, to the 10 or lo metres per second in human muscles. The rate in nerves may be put at 27 metres per .second iu frogs and 35 metres per second in man. The conductiou process Fic. Diagram of muscle-curve (Collins nnd Rockwelll : a, point of application of current; 6, point of begiuning contraction ; c, maximum ; d, return to normal. sweeps over irritable tissue in the form of a wave, which in muscle is about 800 mm. long, while in nerve it is about 18 mm. long. ConduHion is influenced l)y the same factors that affect ooiifracfi/ifij. The nature of the process has not l>een determined, but must be either of phjisical or chemical character. It is intimately depen- dent upon metaboli.vn, yet all attempts to show its chemical nature have, in nerves, resulted negatively. The movements made by striated muscles are too (juick to be followed accuratelv by the eye, so that resource is had to what is known as the (jnijihic inetho'I. The muscle, by means of a mech- anism, is made to write its contractions ami relaxations on a sur- face moving at a uniform rate. The entire arrangenu-nt constitutes a myogrnph, and the record thus obtained is a myoiimm (Fig. 27). The myogram of a simple muscle-contraction consists of three 11— Phys. 162 • NERVE AND MUSCLE. distinct portions. Immediately succeeding the stimulation is an interval {latent period) of about y^-^ of a second, during which the muscle makes no apparent change. During the next -^^-^ of a second the muscle shortens, and during the last -j^-^ of a sec- ond it lengthens again. Contraction and relaxation take place at first slowly, then faster, and finally slowly again. The entire time involved may be put at an average of y-^ of a second. The time-relations vary with the nature of the muscle and the con- ditions under which it works. Finer methods of determination have reduced the late7it period to a mechanical and an electrical latent period of 0.004 and 0.001 seconds, respectively. The latent period of the motor end-plates is about 0.002 to 0.003 of a second. When the striated muscle of a frog is submitted to a series of equal induction shocks at a regular rate, a series of contractions are recorded, of which the first four or five fall in height, and are known as the introductory contractions. After this there is an increase in the height regularly to a maximum which forms the "treppe" or staircase. Following this again, the contractions lose in height until they disappear, which is known as fatigue. It is very probable that the introductory contractions are caused by polarization changes brought about by the stimulating current.^ It is now assumed generally that the molecules of any solution which is a conductor of electricity are in a state of dissociation — i. e., the molecules are divided into two or more parts, called ions. Thus sodium chloride in water becomes separated into a sodium ion charged positively with electricity and into a chlorine ion charged negatively. The passage of a galvanic current through such a solution is accomplished by means of the ions, and gives rise to electrolytic phenomena consisting of a migra- tion of the positively charged ions or kations to the negative pole of the galvanic circuit. In like manner the negatively charged ions or anions move toward the positive. This effect is brought about in any moist tissue that will conduct, and is then said to be polarized. The difference of potential between the kations and anions sets up a current (polarization current) in a direction oppo- site to that of the inducing current. It happens thus that a polarization current produced in any 1 From unpublished experiments made in the Physiological Laboratory of the University of Michigan. NERVE AM) MUSCLE. lf)3 tissue — frofj's muscle, lor instJiucc — will weaken the stinuilating current and conse(|uently tlie cHect which the latter produces. In a seriej^ of stimulations the ])olari/.ation etiects should theoret- ically hecome greater as the excitation |»roer unit cross-section. This for the frog is 3 kilogramnies |>er square centimeter. The heat liberated by active tissue is measured by a thermopile or a bolometer. The first consists of a certain number of junctions of two dissimilar metals like antimony and bismuth, which develop an electrical current whenever any two of the junctions are at a ditfereut temperature. The action of a bolometer dejiends U{X)n the fact that the electrical resistance of a wire varies with the temperature. An isolated muscle has by means of these instruments been found to produce by a single contraction per gramme of muscle substance sufficient heat to raise 3 milligrammes of water 1 degree centigrade. Electrical energy is exhibited by many forms of living matter. Whenever any portion of the latter becomes active or in any man- ner undergoes katabolic changes, a difference of potential manifests itself in that the active portion becomes negative to the rest. The difference of potential is generally small, requiring a sensitive galvanometer or electrometer to measure it. but in some electrical fishes becomes as high as 200 volts. When a muscle or nerve is intact and uninjure*— €^ Diagram illustrating the electric currents of nerve and muscle : being purely diagrammatic, it may serve for a piece either of nerve or of muscle, except that the currents at the transverse section cannot be shown in a nerve. The arrows show the direction of the current through the galvanometer (Foster) : ab, the equator. The strongest currents are those shown by the dark lines, as from a, at equator, to x or to y a: the cut enris. The current froni a to c is weaker than from a to y, though both, as shown by the arrows, have the same direction. A current is shown from e, which is near the equator, to/, which i>; further from the equator. The current (in muscle) from a point in the circumference to a point nearer the centre of the trans- verse section is shown at gh. From a to 6, or from z to y, there is no current, as indi- cated by the dotted lines. to currents of action. When a current of action is superimposed upon a current of rest, the needle of the galvanometer having been deflected to a certain extent by the latter, is made to move back toward the zero point, giving rise to a negative variation. When the nerve of one (A) of two nerve-muscle preparations is laid lengthwise over the muscle of the other preparation (B), and the nerve of B is stimulated with an interrupted current, both muscles are thrown into tetanus. That this phenomenon is not yEIil'E AM> MC6CLE. 167 due to a spread of the exciting current throuirh the prepara- tions i:? ^howu by ligatiui: the uer\-e of B Wiween the electrodes and the nmst-le, when all c«jntra<-tion* cease. As a matter of fact, the muscle-tihres of B jrive rise to currents of action that are cir- cuited through the fibres? of nerve resting on it* surface. The ner\-e-fibre:s of A are thus stimulated and cause the muscle to contract. Thii phenomenon m known ws secondary tetanua. As the wave of a nerve-impulse sweejis by the electrodes, it changes the potential successively of one and then of the other, so that the needle of the galvanometer is dedei."te«l at one instant in a positive direction and in the next in a negative direction. Currents of action are therefore dipha-nc. Changes of irritability due to the passage of a constant current have been alluded to under electro- tonic changes. There are to be observed at the same time varia- tions in the electrical currents of the nerve itself — ». e., variations in the currents of rest. The constant current causes in the nerve outside of the electrodes the appearance of another current that has the same direction as itself, and is called the electrotonie cur- rent. The electrotonie current adds to or takes away firom the currents of rest acconiing as they are dowing in the same direction or in an opposite direction. The strength of the electrotonie cur- rent is dependent upon the strength of the polarizing current, the length of the region between the electrodes, and the condition of the nerve. A dead nerre does not manifest electrotonie currents, and they may be stopped by a ligature or by crushing the nerve. Whenever a muscle dies, it undergoes a change manifesting itself in a loss of translucency, of extensibility and ela-iticity, by the development of a gradual contraction, of increased heat-pro- duction and acidity. This change is called rigor morti-i. It usually affects the bo2, .'58, and 84. Neurones whose tihres hcgin in sensory structures in the skiu, mus- cles, or tendons, carry impulses into the central nervous system, and are known as afferoit neurones. Those whose iihres carry impulses from the central system to the structures which the central nervous system controls are known as efferent fibres. Fig. "t}.— T'nder surfiice or base of the cere- brum and cerehelhini, and of the pons Varolii and medulla oblongata, also the anterior sur- face of the spinal cord. Id show the mode of orifrin of the spiiial nerves fmui the spinal cord, and the cranial nerves fmni the base of the brain: a, a. cerebral hemispheres : h, rifilit half of cerebellum: m, medulla obliin<,'at!i ; above this is a transverse white mass, the pons Varolii; r, C, the spinal cord, showing; its cer- vical and himbar enlargements, and its pointed terminations; f, the caiida e(iuina, formed by the elongated roots y the four lower cervical and lirst dorsal spinal nerves; /, tlii' lumbar plexus; .<, the sacral ]>Kxns, formed by the last lumtiar nerve and first four sacral nerves: t sliows a piece of the sheath of the conl cut open, and with it a portion f)f the ligamenium deiilicu- laHim which s\i)>ports the cord; .1, a trans- verse section tbrouirli the conl, to show the form of the gray cornua or horns, in the midst of the white substance, li shows the sanu- parts, and also the membrane of the cord ; anres ; 3. The efferent fibres leaving by way of the ventral roots and passing to the muscles or to the ganglia of the sympathetic system. The sensory stimuli that are received pass up the nerve-trunks Fin. !W.— Scheme of the nerves of a sopment of the spinnl cord (Foster) : Or. srray : H', white matter of spinal cord: .1, anterior; /*, posterior rfiot : (?, panelion on the posterior root; .V, whole nerve; .V, spinal nerve proper, endinp in .V, skeletal or somatic mnsclc; .s', somatic sensory cell or surface: A', in other ways; r, visceral nerve i white ramtis comnuiiiicansrpassinreganglionic fibres, while those passing from the ganglia to the peripheral structures are termed postganglionic flhres. It is found that each preganglionic fibre is distributed to more than one cell in the ganglion, so that an im- pulse passes out of the ganglion over a number of paths. Normally, impulses are always coming into the cord from all parts of the body ; are diff'used throughout the centrrJ nervous CENTRAL MiJiVurS SYSTEM. 17' system to a jjreater or less extent ; and are the cause of efrerent impulses that (•(intiiuially are leaviiiL'' the cord to he transmitted to the various strudnrr.s of the liodv, kecpinir them in a stafr of tone. This is uoticeal)le in many patli()h)gieal cases, especially iti the Kk!. :i7. Facial paralysis of the right side. (Dalton.) insane, where phases of mental exaltation and depression are de- picted in the expression of the face, so that they appear like (lifer- ent persons. The leirs of a pithed frog do not liany- in a perfectly relaxed position unless the sciatic nerve is severed. Kigor mortis 12— Phys. 178 CENTRAL NERVOUS SYSTEM. usually sets in, in both legs of the frog at the same time, but when the sciatic nerve of one limb is cut immediately after the killing rigor mortis is delayed in that leg. This is accounted for by the fact that the impulses from the cord hasten the onset of rigor mortis. Spinal reflexes are more or less modified by impulses coming from the brain or from other sources. This is shown by Exner's experiment, in which a rabbit was prepared in such a way that an electrical stimulus could be applied either to the cerebral cortex or to the skin of the foot, both being followed by the same muscular response. Excitation, simultaneously, of both places gave a pro- portionally greater response than excitation of either alone. If the skin was so weakened that a muscular response did not follow when applied alone, it could be made effective by stimulating the cerebral cortex 0.6 of a second previously. Excitation of the cortex had the effect of making the nerve-cells involved more irri- table, so that they were able to respond to a weaker stimulus. The increase of irritability passed away in three seconds. It has been shown that the patellar tendon-reflex could be reinforced by a vol- untary contraction or by a sensory stimulation if the interval between them was less than 0.4 of a second. As the interval became greater than 0.4 of a second, the knee-jerk was diminished or inhibited until the time-difference was 1.7 seconds, after which the two phenomena ceased to influence each other. A simple method of showing inhibition of reflexes is to dip the toe of a pithed frog into dilute acid. A contraction results. If the exper- iment is now repeated while at the same time the other toe is pinched, it will be found that the latent period of the reflex is greatly prolonged, or that no contraction at all follows. It has been shown that stimulation of the cortical areas for the flexors of the arms simultaneously gives rise to an inhibition of the exten- sors, and that when the extensors are brought into action there is an inhibition of the flexors. Voluntary responses differ from reflexes in that they are less predictable, more variable, and that instead of following in a very short interval they may be delayed for a long while — possibly for years. The most complex voluntary reactions involve the entire central nervous system, and especially the cerebral cortex. The path taken by the impulse is longer and involves more neurones, so that in its course it may become much more modified. CESTnAL SERVOrs SYSTEM. 179 Impulses over afFcrcnt fibres pas.s aloiiir the posterior spinal nerve-rootd aud euter the curii. Their path is then aloug Hhreti Fi(i. ;j8. Diagram showing pathway of the sensory impulses : on the left side S ^ represent afTerent spinal nerve-fibres ; C. an afferent cranial nerve-fibre. These fibres terminaie near central cells, the neurone ."< of which crosses the middle line and ends in the opposite hemisphere. (Van Gehuchten.) that ascend the posterior columns, and may be either alone: a short-path or a lontj-path fibre. If it is the htfrr, they are carried to the dorsal funiculi, to terminate about cells in the nuclei of the 180 CENTRAL NERVOUS SYSTEM. gracilus and cuneatus. Here the impulse is taken up by a second set of neurones, which decussate, and then go forward in the medial lemniscus, to end either in the ventral portion of the thalamus or in the cerebral cortex. From the thalamus the impulse may pass along a third set of neurones to the cortex. Cranial afferent nerves, which are not of special sensation, like those of the fifth, the vestibular portion of the eighth, ninth, and tenth, have a sim- ilar course. Impulses taking short-path fibres pass largely to cells in the dorsal cornu of the cord, many passing by way of the col- laterals. Cells of the dorsal gray horn send their axones across the cord to the lateral columns of the opposite side and pass to the thalamus through the medial lemniscus. Fig. 39. Degeneration of spinal nerves and nerve-roots after section (Dalton) : a, anterior root ; p, posterior root ; g, ganglion ; A, section of nerve-trunk beyond the ganglion ; B, section of anterior root ; C, section of posterior root ; D, excision of ganglion. Pathways or tracts of the cord may be studied by means of degenerations. A nerve-fibre will degenerate when by section it is removed from the cell-body that governs its nutrition. If the dorsal roots are sectioned between the posterior root- ganglion and the cord, the resulting degeneration will extend down the dorsal columns for two or three centimetres, and up to the nuclei in the dorsal columns of the bulb mainly on the same side as the section. On passing upward, however, the area of degen- eration constantly becomes less, owing to the fact that fibres con- tinually are leaving the posterior columns and passing into the gray matter of the cord. When the cord is hemisected, the ascend- ing fibres that degenerate are in the dorsal columns, in the dorso- lateral ascending tract, and in the ventrolateral descending- CENTRAL M:ii\'()l'S SYSTEM. IHI aHceudlng tract. Most of the (IcirciicratcMl lilires arc to ho found on the same side as tlie section, nltliou^zli a few are on the opposite side. Strong xti)iii(/al!oii oi' Keiixorrj wervea like the .•, movements of tail (ancl trunk); 4, retraction with adduction of opposite arm ; .^, supination and tlexion of the forearm, by which the arm is raised toward the mouth : I'l, action of zypromatics, by whicli the anf;le of mouth is retracted and elevated: 7, elevatinn of ala of nose and upper lip: 8, openin^r of mouth witli i>rotrusion of tonsrue : ;•, ri'traction of tonpue: lo, retraction of opposite angle of niuuth ; (7, b. r, d, preliensile movenu'nts : 11, retraction and adduction of opposite arm: I.', advance of the opposite hind liml); 13, complex movements of thigh, leg, and foot: 14, 15, vision (sensory); IR, hearing (sensory;. At the decussation of the. pjiraniids the irreater ininiher of the fii)res from the internal capsule of each side cross to the opposite side, and when they reach the cord are jTrouped together to form the crossf'<1 piiramidal trart oi' the latrral cohnnnx. A les.yramidiil tractx of the a)itcrior columns. Injury to the cortex of one hemisphere will produce degenera- 184 CENTRAL NERVOUS SYSTEM. tion of the cross-pyramidal tracts of both sides, but that on the side opposite the lesion is much more marked. The direct pyramidal tracts are well defined in man and monkeys, but extend only to the mid-dorsal region. Before their termination they cross to the other side of the cord in the gray commissure. The motor fibres of both pyramidal tracts end in relation with motor cells in the anterior horns of the spinal cord, which cells in turn send their axones to the muscles by way of the anterior spinal nerve-roots. There is no direct relation between the size of a cortical motor area and the mass of the muscles that it controls, but the size is correlated with the complexity of the reactions that the muscles take part in. Each region is divisible into subsidiary areas. For instance, if the electrodes are moved from one limit of the arm- area to the other, there will be a regular contraction of the mus- cles from the shoulder to the phalanges. Areas thus called motor are not purely so, for they also contain fibres that bring afferent impulses from the skin, muscles, tendons, or viscera to the cortex. There are some purely sensory areas which produce no response on stimulation. Of these, there are four principal ones : 1. The olfactory area, which extends over the uncinate gyrus, the gyrus hippocampi, and a part of the gyrus fornicatus near the callosum. 2. The visual area, which is found about the calcarine fissure, all through the cuneus extending to the occipital lobe. 3. The auditory area, which includes the transverse gyri in the Sylvian fissure and the first temporal gyrus. 4. The body-sense area, which is found about the two central gyri and extends forward to the frontal gyri, and from the pre- cuneus over one-half of the mesial surface of the hemisphere. As the result of common experience it is known that a motor response may follow any sensory stimulation whatsoever, so that motor and sensory areas must be connected. The fibres that bring this about are called association-fibres. Their function is to fur- nish pathways which are more or less intricate between different areas, and to retain previous impressions as memories which modify any other impulses passing over them. When the motor and sensory areas are contrasted with the surface that remains of the cortex, it is found that extensive areas give no response upon direct stimulation. They may be designated as latent areas. They include the ventral surface of the hemisphere, a considerable CESTRAL MinVOVS SYSTEM. 185 portion of" the ni(!.sijil surfju'c, and parts of tlie frontal, parietal, and temporal lohos. The frontal rej^ion is conni'eted liy iihrea with the |)ons and eerehelhiiii. Removal of this portion of the brain is followed hy transient sensory and motor ilislurliaiices. Jinnoi'dl of hoth lohes eanses the animal to lose all curiosity, atJeetion, pleasure, and capacity to learn. It is in this portion of the brain that the intelligence is centred ; it is the organ of the mind. Memory, reason, emotions, and all the other attributes of the mind are ^^:- / # / f 0$i0W Diasram of human brain in transverse vertical section (Dalton): 1, tuber an- nulare : 2, 2, crura cerebri ; 3, 3, internal capsule; 4, 4, corona radiata ; 5, 6, cerebral ganglia ; 7, corpus callosum. with which they end send their axones to the cerebral cortex. Some cells in the cortex, in turn, send axones back to the thala- mus. Cell-groups which increase the responsiveness of the central system are probably located here. Lesions are accompanied by a loss of power to express the emotions through the muscles of the face. When they extend to the internal capsule and to the crura cerebri, paralysis results. Lesions in the crura lead to paralysis of the opposite side of the CENTRAL NERVOUS SYSTEM. 1m7 l)ody, both of sensation and of motion, of a degree depending npon tiie extent of the lesions ; and, besides, result in a paralysis of the motor oeuli nerve of the same side aa the lesions. There is a derangement of the ooilnlination of movements, sliown in rotary movements when the suhjeet attempts to walk. It is inferred that co'irdinating im|)ulses pass througli the crura. The a)ik'rior cor/ioni (ji((alri(iriiiiiidy; XII', nucleus of the hypoglossal: ^ funiculus teres: a, nucleus of the acusticus; m, stria- mcdullares: i,-, and 3. middle, su]>eri()r, and inferior cerebellar peduncle, respectively : /, fovea anterior: J, eniinentia teres igenu nervi facialis) : n, locus cooruleus. The right half of the figure represents the nerve-nuclei diagranimatieally : I', motor trigeminal nucleus: I', median, and l", inferior sen- sory trigemiiuil nuclei : 17, n\iclc\is of abduccMis: 177, facial nucleus: 1777, poste- rior median acoustic nucleus: 1777'. anterior meiiian ; 17/7", posterior lateral; VIII'", anterior lateral acoustic nuclei : 7A', glossopharyngeal nucleus: A', A7, and A'/7, nuclei of vagus, spinal accessory, and liypoglossal nerves, respectively. The Roman numerals at the side of the figure, from I'to A7/, represent the correspond- ing nerve-roots (Erb). V. The tn'rfeyninus )ierve breaks up into three branches : of these, the first and seconrl are entirely sensory, while the third is motor. Section of the motor root of the nerve results in a paral- 190 CENTRAL NERVOUS SYSTEM. Fig. 44. ysis of the muscles of mastication. Destruction of the sensory root results in complete anaesthesia of the skin of the face and the mucous membrane of the mouth. The anaesthesia of the conjunc- tiva, of the nostrils, and of the lips prevents the reflex self-pro- tection which belongs to the parts, and they become easily injured. The nerve-cells are located in the Gasserian ganglion. The periph- eral axones extend to the skin, while the central axones upon reaching the bulb divide into a shorter branch, which extends cephalad and a longer branch which extends caudad, both con- necting with cells in the sub- stantia gelatinosa. One set of neurones is thought to pass di- rect to the cerebellum. VI. The abducens supplies the external rectus muscle of the eye. VII. The facial is a motor nerve which parallels in its dis- tribution the sensory portion of the fifth. It supplies the super- ficial muscles which give the power to the features reflecting the emotions. If the nerve is sectioned, the face on that side is devoid of motion and becomes smooth and expressionless. The eyelids do not close and the lips do not oppose properly on account of the defective action of the or- bicularis muscle. There is difii- culty in drinking and in speaking for the same reason. VIII. The cochlear jwrtion of the auditory is the nerve of hearing. The cell-bodies of these fibres are situated in the spiral A partly diagrammatic view of the floor of the aqueduct, looking upward (dorsally), nuclei of the third and fourth nerves, and the decussating fibres of the latter all shown; the third nerve nuclei are subdivided into an anterior nucleus, the Edinger- Westphal nucleus fa and h), and a posterior nucleus ; the ijosterior nu- cleus has a dorsal, a ventral and a mesial portion; the decussation of the fibres from the dorsal portion of the posterior nucleus of the third nerve is shown. (Edinger.) ci:\ TIL I /. m:i: \ 'o i 's s ystem. IIJI paii superior olive, the lateral lemniscus, and the inferior collicus. They may jrive collaterals (o each, or may end iu any of these gray masses. Cells of the dorsal 192 CENTRAL NERVOUS SYSTEM. nucleus send their axones across the floor of the fourth ventricle, forming the strise acusticse. The vestibular portion of the eighth nerve transmits impulses from the ampullae of the semicircular canals, and therefore serves the sense of equilibrium. The cell-bodies of these fibres are located in the vestibular ganglion, and their central axones are Fig. 46. Diagram of the facial nerve and its distribution : 1, facial nerve at its entrance into the internal auditory meatus; 2, its exit at the stylomastoid foramen; 3, 4, temporal and posterior auricular branches, distributed to the muscks of the exter- nal ear and to the occipitalis ; 5, branches to the frontalis muscle ; 6, branches to the stylohyoid and digastric muscles; 7, branches to the upper part of the platysma myoides ; 8, branch of communication with the superficial cervical nerve of the cervical plexus. divided into a branch passing cephalad and one passing caudad, which terminate with various nuclei, and also pass to the cerebellum. IX. The glossopharyngeal nerve is the nerve of taste and of deglutition. It is motor as well as sensory in function. Its dis- tribution is to all the muscles of deglutition, and stimulation contracts, while section paralyzes them. The very numerous WKiaiiT AM> ciiowrn III- nil', iuims. \\y.\ comu'clioiis of tlu- iiorvi' comiylifalr ils ()ii;.'-iii and iiitcrirrc with a clear coiiiiJrc^luMision of llu' unaided I'unclioii n|' liu- nerve. The cells of the tihress lie in the huilt on the medial siile oi" the tractiid solitarius. Their axoiie.s are sent ci'|ihalad lhriiu,i,di the medial lemniscus. Lalcd bivcdUjdlion--* have kIioivh that the chief path af the t< (To|)inard\ Classes. >rales. Females. Macroc'cplialic 192.") to ITOf 174.S to 1.^01 Larcro 1700 " 14-j1 1.-)()0 " 1.",")] Medium 14-30 " ]'2.')1 1.S.50 " ll.")l Smalt 12.'>0 " 1001 ILiO " Wl Microceplialic 1000 " oOO 900" 28.3 In comparinLT brain-weights, the method of rt'inoval of tlie ence|)halon should always be considered, since retention of |>ia antl the fluids of the ventricles affects the result, l.-?— Phys. 194 CENTRAL NERVOUS SYSTEM. In Boyd's method, after the skullcap has beeu removed but the pia left intact, the hemispheres are sliced away in horizontal sec- tions as far down as the tentorium. By means of a section pass- ing in front of the corpora quadrigemina the remainder of the hemispheres is removed. The cerebellum, including the quad- rigemina, pons, and bulb, is finally removed. Each portion is weighed separately. Sometimes the pia and the fluid within the ventricles are included in the weight of the brain, and sometimes act. Broca gives the following table for the weight of the pia, for normal males : 20 to 30 years 45 grammes. 31 " 41 " 50 60 " : 60 «' The ventricles have a capacity of 26 c.c. of water. In considering the weights of different brains, it is assumed that the proportion of nervous to non-nervous tissue is constant, so that different weighings may be compared. If this be the case, then the variations in weight may be due to greater size of the individ- ual nerve-elements, indicating a greater potential energy, or they may be due to a greater number of nerve-elements giving rise to more possible pathways. A minute study of the proportional weights of different parts of the brain shows that variations due to sex, age, and stature are very .constant, which is in harmony with the view that weight-differences are due to the size of the nerve-elements rather than to variations in their number. In the latter case brain-weights would show independent variations in different parts of the encephalon. All parts of the central nervous system of males are heavier than corresponding parts of females. The weight varies, in each, directly with the stature and inversely with old age. The brains of criminals do not differ in any marked way from those of ordi- nary hospital patients. Insane (excluding microcephalics) have no characteristic brain-weight, except in such cases where a con- gestion of the brain has occurred, when the weight is markedly increased ; on the other hand, insanity due to destructive changes of brain-tissue is marked by a low brain-weight. As a whole, individuals whose brains during the years of growth have been under favorable circumstances possess the heavier brains. In some degree the size of the brain bears a direct relation to the )VF.i<:irr AM) <:nn\\rii or riii: hums. Hi-'i hitrlh'ct of tlic iiiilividiial. Itiit lliis is iiol ahsulute. Tlic (Icplli of the sulci ami llu- coiistMniciit size aii^ in the walls of the ve.ssels of the |)ia, anut to sleep at will by closing the eye and stopping the ear. In aildition, sleep has been attril)Uteil to the following inlluences : 1. ( "hemical intlueiices ; 198 CENTRAL NERVOUS SYSTEM. 2. Circulatory influences ; 3. Histological influences. Those who hold to chemical influences in the production of sleep, maintain that during normal activity of the body various substances are formed which are circulated in the blood and directly lessen the activity of the nerve-cells or indirectly diminish the supply of blood to the brain. In the theories of circulatorg influ- ences a fatigue of the vasomotor centre is looked upon as the cause of the anaemia of the brain resulting in sleep. In the third set of theories sleep is supposed to be due to a separation of the dendrites of the brain-cells due to a shrinkage of the nerve-cell bodies or to an intrusion of neuroglia-cells between them. During sleep the capability of the nervous system to transmit impulses is not entirely lost. The cerebral cortex is most affected, the spinal cord least. The close relation between dreams and external stimuli is well known, and it has been proved experi- mentally that vasomotor changes, induced by external stimuli, may take place without awakening the sleeper. The period of deep sleep is short and falls within the first two hours after its onset. During this time the pulse and breathing are slower, the intestines and bladder are at rest, the output of carbon dioxide is lessened, and the consumption of oxygen still more so ; metabolism is less vigorous and the temperature falls. The respiration is said to become thoracic in type and to take on a more or less pronounced Cheyne-Stokes rhythm. The visual axes are probably parallel and directed to a distance, but the pupils are contracted. The latter is peculiar, since an absence of light should bring about dilatation. This is connected perhaps with important actions taking place in lower levels of the brain. Loss of sleep is more injurious than starvation. Dogs have re- covered from a period of starvation of twenty days, but a loss of sleep of five days proved fatal. The body -temperature fell 8° C. below normal and the reflexes disappeared. The red blood-cor- puscles first were diminished, but later increased in number. Post- mortem examination revealed widespread fatty degeneration and cerebral hemorrhage. In experiments made by Patrick and Gilbert, three subjects were observed for ninety hours while being deprived of sleep. The gain in weight which resulted was lost during the first sleep after the experiment. A decreased pulse-rate and a lowered body- WEiaiir AM) ciiowrii OF Till-: hums. n»:> U'iii|)oratiire were observed. In jreiieral, lliere was a loss of all powers ex<»']»t ill a<'Ut('iiess of vision, wliidi was increased. Hibernation. — This is comiefted cio.sely witli sleep, occurring perioilically in many irroui)S of animals and in a few manimal.s. It is characlerized l»y a les-seiieil metaltolism resnlliiiLr from a fall of the e.xternal temperaliire, and may he producctl artificially in summer hy cold. The hearl heats very slowly and not very vi;:- orously. while respiration is very slow and feei)le. ^Nevertheless, the hlood, arterial as well as venous, is bright scarlet in color, owiiiiT to the little oxyyen consumed hy the tissues. A hihernating dormouse has been observed to gain in weight, which was due en- tirely to an exee.ss of oxygen takeu in. Muscles and nerves reinaine aliowm OF Till: HUMS. 'JOl more viixonms. A siiiiilnr ri'Siill lullous scdioii of IIk- ci-rclicllMr ]n'ilmicli's. Time Involved in Nervous Processes. — WIkmicvit a in-rvc- iiiipiilsc passes from one neurone to another, there is a delay in its transmission. In the fro;.', tor exanipU', it takes twice as hmj: tor an impulse to pass from themidtlle of the cereljral hemisphere.*; to the optic lohes as from the hulh to the lumbar enlargement, allhoule signals, the reac- 202 CE^TBAL NERVOUS SYSTEM. tion-time may be prolonged from 0.016 to 0.062 second, the time varying with the sensation employed. It is shortened by prac- tice, so that in time it becomes more of the retiex type. Nerve-centres. — It is very difficult to give a satisfactory defini- tion of what is meant by a centre. In general, any portion of the central nervous system where impulses originate or undergo modi- fication is a centre. The modification of the impulse may be in strength, in direction, or in time. There is no doubt that many of the so-called centres of the central nervous system are not really such, and of the remainder all are not equivalent in power, which depends mainly upon the number of paths by which impulses may reach them. By association-centres are meant portions of the cerebral cortex that lie between sensory centres and whose function it is to retain previous impressions as memories. Flechsig calls the association- centres "organs of thought." The conception of association-fibres and -centres gives an explanation of many pathological phenomena. In order to do this, it is necessary to assume association-paths between most or all motor and sensory areas. These are better organized in some cases than in others, so that the communication, for example, between visual, auditory, and motor centres is more complicated and complete than that between auditory, gustatory, and motor centres. There exist, besides, differences in the two hemispheres. Broca first showed that a lesion of the third frontal convolution of the left hemisphere resulted in a loss of the power of speech. It was soon found that lesions of the corresponding area of the right hemisphere do not produce so great a disturb- ance, particularly in right-handed persons. It is concluded, therefore, that in most persons the speech-centre is developed more highly on the left side. A greater perfection of the right eye and ear, involving corresponding changes in motor areas, sus- tains the idea that in these respects at least the hemispheres differ. Speech involves both sensory and motor areas of the cortex. Nerve-impulses, reaching the sensory areas, affect consciousness. Through the senses of hearing, sight, or touch, certain disturb- ances in the medium external to the nervous system are able to arouse in the sensory areas the idea of words. Any permanent interruption of impulses to the sensory areas will result in deaf- ness, blindness, or touch-ausesthesia. The portion of the brain sr/:i: the corpus callosum, and thus to the opposite hemisphere, and to the internal capsule. I^esions of purely motor areas or paths ressult in a loss ot' c.xjjression ihrouirh paralysis of the neccssarv muscles. The effects |)roduced l»y an interruption of the impulse along its incoming or outgoing [»ath arc easily understood. When, however, a lesion occurs witliin the central nervous system in- volving any of the paths required in speech, the results are more com|)licateil. Lesions of sensory areas give rise to .ieimory ajthu.'^'a. When these are situated in the occipital region, there results an inability to form a comprehension of written language. Words are seen, hut are not understo^td. This is known as nhwin or u'ord-bliiiilnt'iix. In this case spoken language is readily under- stood. Similarly there may he no rd-deafii €■■<■<, when written lan- guage is understood, but spoken language becomes a mere series of noises without meaning. The lesions in this case exist in the first and second temporal gyri and in the gyrus supraniarginalis. A destruction of the paths connecting the auditory centre with the speech-centre would cause word-deafness. In alexia there is always an inal)ility to write. Motor (ij}Ji(i.'ia. 2U4 CENTRAL NERVOUS SYtiTEM. QUESTIONS ON CHAPTER XII. How may the central nervous system be divided ? What is a neurone ? What is the length of the longest axones ? What are collaterals ? How do the branches of nerve-cells and collaterals end? By what means are impulses transmitted from one neurone to another? What is the function of the nervous system ? What are afferent, efferent, and centi-al neurones ? What is a reflex act? What is shock ? How is it produced ? Describe the path of a simjjle reflex. Discuss a reflex act involving consciousness. Discuss the spread of an impulse iu the cord. What is the latent period of a reflex act? How is it affected by an increase in the strength of the stimulus? Discuss the summation of stimuli in the cord. What is the smallest number of segments that can produce a reflex in the frog ? How is the cord modified as the animal ascends in the scale of development ? Name some of the reflexes found in man. Why is it that many reflexes uncontrolled in children are brought under the will later in life ? Discuss the diflTusion of impulses in the cord. What are preganglionic and postganglionic fibres? Discuss the cause of tone of the body. How are spinal reflexes normally modified ? Give experimental proof. Stimulation of the cortical areas controlling the flexors produce what effect upon the extensors? How do voluntary responses differ from reflexes ? Give in detail the afferent path of impulses from the skin to the cortex. What cranial fibres have the same course? How are pathways in the nervous system determined ? Describe the degeneration following section of the posterior spinal nerve- roots. What proof is there that vasomotor impulses pass through the lateral tracts of the cord ? Give the percentage of impulses passing over the posterior and lateral columns. What path do impulses from muscles and tendons take ? What is the path of dermal impulses? Describe the effects of hemisection of the cord. What effect in general have impulses when they reach the cortex ? What is the result of stimulating certain areas of the cortex ? What is the direction of the fibres tliat leave the cortex ? Give proof. Give in detail the path taken by motor fibres from the cortex to the mus- cles. What degeneration follows unilateral lesion of the motor areas of the cortex ? Wliat is the relation of the size of the cortical motor areas to the muscles they control? How may each motor area be divided? Are motor areas purely motor ? Name the principal sensory areas. Give their location. QrESTinys n\ rjT.\pTi:n xir. 'iO") Wlial :irc as.s(ifiatioii-(itirc's? Wlial is till- liitKiioii of iissdciiitidii-fibri's? What ari" lat('ii( areas? Wlicrt' loralcd V Wliat symptoms follow li-sioiis of tlic frontal areas? What is tile I'uiielioii of the cerehnitn ? (live the results of tin- removal of the eerehrimi. What is the fiiiutioii of tlie ctTehelliiin ? Give the results of removal of the eerehelliim. What symiiloms follow seetioii of the commissural lihresof the corebellum? What are the forced movements tliat follow injury to the eerehelliim? Discuss the function of the thalamus. Name lilires that connect it with other parts of the hniin. What symptoms follow lesions of thei-rura? What are the functions of the iinailrijiemina ? What symptoms follow lesions of the ([uailriyeniina ? What are the functions of the iiieduUa? Discuss the resultsof division of the spinal cord. What is the behavior of a frog whose brain has l)een destroyed with the COnl left intact? Wiiat is the behavior of such an animal when only tlie lieniisplieres hav*- been remove(l ? Discuss the function of each of the cranial nerves. What is the path of the fibres of tlie first cninial nerve? What is the jiatli of tlie tibres of the second cranial nerve? What syni])tonis result iVom jiaralysis of the third nerve? What .symiitonis result from paralysis of the fourth ? Discuss the path of the fibres of the fifth. What is the result of .section of the seventh? Discuss the jiath of the tibres of the cochlear portion of the eighth nerve. What is the path of tlie vestibular fibres of tlie eighth? Where are the cells of tlie fibres r)f the ninth located ? Discuss the functions of the tenth. What symptoms result from section of the twelfth? Explain fieiieral fatigue. How is the inlnieranial pressure regulated? What can be said of the nietabolism of brain-cells? What is the cause of sleep? Discu.ss sleep. Discuss hypnotism. What is meant by the knee-jerk? (live the evidence for regarding the knee-jerk a reflex act. (live the evidence that knee-jerk is not a reflex act. Define nerve-centre and association-centre. What is meant by alexia and agraphia? In what ways are apheniia and agraphia produced? What is amnesia? Distinguish amnesia from motor ajihasia. 206 THE SPECIAL SENSES. CHAPTER XIII. THE SPECIAL SENSES. SIGHT. The eye is a special orgau by uieans of which certain rhythmic disturbances of the ether atfect consciousness and produce the sen- sation of light. Among other functions that the eye serves are the determination of color, of distance, and of form. It consists of Horizontal section of the riglit eyeball (Collins and Rockwell): 1. optic nerve; 2, sclerotic coat ; 3, cornea ; 4, canal of Schlemm ; 5, choroid coat : 6, ciliary muscle ; 7, iris; 8, crystalline lens; 9, retina; 10, hyaloid membrane; 11, canal of" Petit; 12, vitreous body. various adjustable refracting media, by means of which the rays of light are focused properly on the retina, and of various mus- cles and accessory structures by means of which the eye is moved in different directions and is protected. S ft; I IT. 'jo; Tlir iniisr/m nf (hr n/f scrvr lo move tlie ('yel)all lliroii^'-li \vi ill all directions. W'licii tlic (ixia of risimi points straijrlit ahead, the eye is in the prliiKiri/ position. If it moves iVoiii this position, so that the axi.s of vision rotates either ahoiit the trans- verse or vertical axis, then the eye is in a nccutidar;/ position. All other positi«)ns are called tertian/. In order to understand clearly the nature of the ima{?e received by the eye, it is only necessary to review the images cast by a convex lens. If a double-convex lens is taken and the imajic formed by a luminous object is noted, it is seen that it is an inverted imaffe at the jioiiit of focus (jf the lens if the luminous object is {)laced at a distance. Keferriiil' iiiuitrc I'V omivox Ions. same is true for B and b. Therefore a screen j)laced at focus, F, will receive an inverted image, ob, of the luminous object AH. If the lens were more convex, the imaLre would be formed nearer the lens; if the lens were flatter, the ima< becomes less, and the convexity cannot be increa.«ed for near vision. The ciliary nuis- clc may also bo weaker and aid in the production of the error. Astigmatism is a delect in the vision due to irrcLndarity in the globe of the eye whereby the diameter in one plane is greater 14— Phys. 210 THE SPECIAL SENSES. than in another. Thus the cornea or the retina may be an uneven surface and the image focus definitely in one part and falsely in another. In this condition vertical, variously oblique, and hori- zontal lines are not seen with equal distinctness. Astigmatism is corrected by the use of cylindrical or prismatic glasses, which have to be accurately adapted to the needs of each case. This error, if serious, usually accompanies other defects of vision. Diplopia is the condition which results from a want of liarmony in the eyes, so that the image of each eye is perceived separately — that is, two images are seen. Diplopia is caused commonly by paralysis or spasm in one of the lateral straight muscles, which results from a want of harmony in the eyes. If the eyes are turned so that the axes of vision separate, the condition is known as external strabismus, or squint; if the axes are crossed, the result is internal strabismus, or cross-eye. When a pencil of rays falls on a spherical, refracting surface, those at the periphery of the surface will be refracted more than those which lie near the axis, and will come to a focus sooner. This phenomenon is known as spherical aberration, and exists also as an imperfection in the eye, where it is corrected largely by the greater refractive index of the centre of the lens, and partly as well by the fact that the iris cuts oif the peripheral rays. Contraction or dilatation of the pupil is a reflex act, and the afferent impulse is carried through the optic nerve, while the motor impulse comes through the third cranial nerve, acting from a centre just beneath the aqueduct of Sylvius and the corpora quadrigemiua. The increase in the amount of light that comes to the retina causes a contraction of the pupil, and a decrease is fol- lowed by a dilatation. The pupil is controlled also by fibres of the sympathetic and fifth nerve which connect with the ciliary ganglion. Drugs are active in controlling the action of the iris, Atropin both locally and internally dilates the pupil ; o/)i«m taken internally, and eserin applied locally, contract it. If in obtaining an image of an object through a double convex lens the lens be too large, there will be seen around the image formed a halo of prismatic colors. This is called achromatism, and is produced by an tmequal refraction of light-rays by the peripheral portions of the lens. The unequal refraction results in a dispersion of the light, so that it is broken up into the primary colors. This defect is remedied by putting a shutter in siniiT. 211 front of the lens, and so liinitini,' the entranre of li{;lit to the (vntral portions of tlie lens, where the index of refraction is con- stant. In the eye the iris acts as a shutter, thus rnakinj^ the image achromatic, hut in some defective eyes where there is con- siderahle fault in the focus of the image on tiie retina a visii)le band of color appears. Under certain conditions a nuiid)er of ohjects lying within the eye itself become visible. Of these intraocular images, the most common are known as musca' vo/ita)itrs. These are in the form of beails, streaks, or patches. They have an independent motion, which is increased l)y the movements of the eye. They are of greater s|)ecitic gravity than the medium in which they are found, and are suj)posed to l)e the remains of the ('m/jrijo)iic structure of the vitreoua body. Under normal conditions the pupil appears as a black spot. The reason for this is that the source of light and the retina lie in conjugate foci, so that any light which escapes absorption by the retinal pigment is reflected hack whence it came. Therefore the eye of an ol)server who views it from another direction will see no light coming from it. By means of an ophtlialmoscope, however, a strong light is thrown into the fundus of the eye, which upon reflection is viewed by an observer through an opening iu the re- flector. The fundus is seen to have a reddish background in which the retinal vessels are visible. The most important struct- ures are the ro(h and cones. They are closely packed on the outer surface of the retina, the rods over the greater part of the retina being the more numerous. They are cylindrical bodies of a transparent substance placcvd parallel to one another and per- pendicular to the surface of the eyeball. The cones, which are modifications of the rods, are very similar to the latter, but do not reach the same level. These structures are connected more or less directly with the fibres of the optic nerve. Where this nerve enters the retina, a little to the inner side of the most pos- terior point of the eyeltall, there are no rods or cones, so that an image focused at tliis point will be followed by no ])erception. This ])oint is called the hliiid xpot. If the left eye is covered and the right directed steadily upon the cross in Fig. 51, the circular spot will be visible at the same time, though less distinctly. As the book is moved slowly backward and forward, a point will be found at which the round spot disappeai-s, reappearing as the 212 THE SPECIAL SENSES. book is held nearer or farther, or as it is inclined in either direc- tion and the image is carried from the blind spot. At the exact centre of the retina — that is, the most posterior point of the eye — there is a small yellow area (jnacula lutea) with a central depression (fovea centralis). Here none of the fibres of the optic nerve are to be found, but a great increase in the number of cones as well as an increase in their size. If the object looked at is focused directly upon the macula lutea, the image is seen with greatest clearness. In everyday life images are received upon the macula lutea, and rays of light entering the eye at an angle are focussed on some other part of the retina, and are not defined so clearly. A retina which has been protected from the light for a time has a purplish-red color, due to a coloring-matter termed visual purple. This is confined to the outer portions of the rods and does not Fig. 51. reach the cones. It is bleached by light, but restored by the pig- ment epithelium. The retina of a rabbit may be impressed with an image focused upon it and then treated with a 4 per cent, solution of alum, which "fixes" it and prevents the restoration of the visual purple. Such a picture is called an optogram. Vibrations of the ether form the normal stimulus for the retina, the rods and cones of which form, perhaps, the only structures of man that can supply the necessary conditions for the transfor- mation of radiant energy into the energy of a nerve-impulse. The ether- vibrations vary widely in their frequency, and only certain ones are capable of affecting the eye. The impulses they generate pass to the brain by way of the optic nerves, giving the sensation of light. If the optic nerves are examined in a superficial manner, they will be seen to leave each eye and pass backward through the SIGHT. '2i:i optic foramina until they reach tlie body of the sphenoids. Here they cross one another in tlie form of an X (optic chiasm;, the fibres intermingling, and the right nerve apparently i)assing over ¥ui. 52. Left Eye Rhjht Eye Optic radio Optic radiation Cortex of occipital lobe witli cortical cells 1, external geniculate body; 2, pulvinar: S, anterior quadripeininate body; 4, inter- nal geniculate body ; •'), citniniissurc of <;ud(U'n. iCoUiiis ami Hockwell.) to the left side and the left nerve to the right side. The posterior limhs of the X jiass backward, and are called the optic tracts. The optic tract.s in their course curve around the crura cerebri to 214 THE SPECIAL SENSES. terminate in the ganglion-cells of the pulvinar, anterior quadri- gemina, and external geniculate bodies. From these, ganglion- cell fibres, called the optic radiations, pass backward to terminate in the ganglion-cells of the cortex of the posterior part of the occipital lobes. A closer examination of the optic nerves will show that each consists of two distinct bundles of fibres laterally placed. The inner set of fibres conies from the inner half of the retina ; the outer bundle comes from the outer half of the retina. If these bundles are traced to the optic chiasm, it is noted that the inner bundles decussate and pass to the opposite side of the brain. Thus the left pulvinar, left anterior quadrigeminate, and external geniculate bodies receive fibres from the inner half of the right eye, and from the outer half of the left eye. The commissure of Gudden, which connects the internal geniculate bodies, probably plays no part in vision. When an image is properly received on the retina, it excites the rods and cones to activity. When the impulses reach the basal ganglia, the sensation of light is not aroused. Light is not perceived until the impulses reach the cortex of the cerebrum. The pulvinars, the external geniculate bodies, and the anterior quadrigemina form the j^rhnary vision centre. The character of the sensations aroused depends upon three modifications of light : 1. Color, which depends upon the rate of vibration of the ether- waves. 2. Intensity, which depends upon the energy of the vibrations. 3. Saturation, which depends upon the amount of white light mixed with light of one wave-length. It is easily demonstrated for man that luminosity is recognized more easily than color, and this probably holds true for all organ- isms. Colored objects appear colorless when the light is too feeble, and if the light is increased in intensity the colors appear, but as it becomes too strong there is a tendency for all colors to pass into white. This is most noticeable in the yellow. DiflTerent regions of the retina vary also in their power to distinguish colors. Red is lost at a short distance from the macula lutea, while the violet is lost only at the borders of the retina. Stimulation of the retina is followed normally by a latent period, then by a period during which the effect of the excitation reaches a maximum ; from the maximum there is a slow decline in the effect, which is analogous to fatigue, and when the stimulation has siC'iiT. 215 ceased there is an after-effect which sh)\vly passes away. When a very hritive liicultii'.s can juil^e inure correctly h of the canalis cochlearis. The llnid wave in the canalis cochlearis is in 220 THE SPECIAL SENSES. a position to irritate the hair-cells of the organ of Corti. These cells seem to be able to respond to particular tones by their sensi- tiveness to certain rates of vibration. But the fact that the organs of Corti are absent in birds which evidently are capable of appreciating musical tones shows that they are accessory and not absolutely essential. The branch of the eighth nerve, having received its impulses from the cells of the organ of Corti, transmits them to the centre under the acoustic tubercle in the floor of the fourth ventricle ; Fig. 57. Diagrammatic view of the relative position of the parts of the ear (Chapman) : EM, external meatus ; T?/M, tympanic membrane ; Tij. tympanum ; M, malleus ; I, incus; S, stapes; R, round window; O, oval window; SG, semicircular canal; U, utriculus; S, sacculus ; V, vestibule; SV, scala vestibula ; ST, scala tympani; MC, membranous cochlea ; LS, lamina ossea ; Em, Eustachian tube ; AN, auditory nerve. thence fibres pass by means of the trapezium in the pons to the opposite side, and through the lower fillet of that side to the pos- terior quadrigeminal body, whence by means of the brachium, internal geniculate body, optic thalamus, and internal capsule, they proceed to the cortex of the first and second temporal con- volutions. By suhjeetive hearing is meant sounds that are heard distinctly and yet are not produced by physical sound-waves from the exterior, nor are they hallucinations. They may be due to dis- turbances of the auditory apparatus or to abnormal conditions of SENSE OF EQl'ILinnirM. 221 surrounding organs. Thus huzzing or ringing in the cjirs may result from the liypeneniiji of the parts and the increa.M-d rush (if hlood, or from disease in the auditory nerve or some other portion of the apparatus. Ilalhicinalions are purely creations of a cr/W/r//y which makes tliem musical, otherwise they are known as noises. The range of musical notes that can he appreciated by the hun)an ear is about .seven octaves. There are about oOOO hair-cells in the organ of Corti, and it is easily seen that this would allow an enormous capabUity to within the central system. The skin is an organ for the detection of temperature-changes, and its power in this respect varies in different portions of the body. The intensity of the sensation depends upon the area stimu- lated. There is very little doubt that there are two distinct tem- perature-nerves, which serve, respectively, for the appreciation of heat and cold. The areas to which the nerves are distributed can be located in the skin as cold and heat points. That this sensa- tion is distinct from ordinary tactile sensation has been inferred from the fact that when the ordinary touch is blunted the tempera- ture-sense remains unimpaired. Temperature-sensations are not accurate ; they are only relative — that is, the temperature of various things is inferred from the temperature of the skin and its habitual surroundings. It is related that Arctic explorers have found the water warm when swimming in pools on icebergs, and a drop of mercury at 80° F. is said to feel cold in the tropics. A more simple illustration is that of immersing one hand in water at 40^ F. and the other in water at 120° F., and then plunging both into water at 80° F., when one hand will feel hot and the other cold. During a chill the temperature of the body is often very high, and yet the sensation is that of cold. COMMON SENSATION. By common sensation is meant that state of mind, more or less definite, by which the condition and position of the body at any moment are known. Such perceptions cannot be located distinctly in any organ or set of organs, as, for instance, hunger, thirst, etc. Besides these there are some sensations which involve certain organs which must be classed under this head ; thus inclinations QUESTIOyS ON CHAPTER XIII. 'I'll to cough or to sneeze, to vomit, (lefecate, und urinate. Many of these sensations occupy the border-line hetween common sensi- bility and the special sense of touch, such as tickling and itching. Pain is a common sensation, but is allied very closely to touch. It is the sensation which results from intensifying any common sensation, and ditlers from the special sensations in not being well localized and in the long latent period that precedes its develof)- ment. According to one investigator, j)ain-point.s are se|)arate from pressure-points and are more numerous. More than lOU are found to every square centimeter of the skin, and they require 1000 times as great a stimulus for their excitation as do the pressure- points. Hunger and thirst are })eculiar sensations, which ordinarily depend partly on local and partly on general causes. Local causes of hunger and thirst are an empty stomach and certain conditions of the mucous meni])rane. These sensations are felt largely as the result of habit, and depend thus upon the condition of secreting and absorbing mechanisms. By taking a body in the hand and raising it, a sense of resist- ance is felt in the muscles, by the intensity of which the weight of the l)ody can be determined more accurately than by the press- ure-sense alone. This is called the muscular soise. It is devel- oped to an exceedingly fine degree in some occupations ; for ex- ample, postal clerks detect overweight letters with wonderful accuracy and quickness. ]\Iuscular sensation is allied closely to common sensation. It may be due to a consciousness of the amount of energy sent to motor cells or to the inflow of sensory impulses which indicate the tension to which the muscle has been subjected. The latter view is corroborated by the existence of sensory endings, the muscle-spindles, in muscles and tendons. The centre for the muscular sense is in the upper part of the quadrate lobule on the mesial surface of the heniisi)here. Its involvement by pressure lirings al)out inability to locate the posi- tion, say, of the hand or foot without the aid of sight. QUESTIONS ON CHAPTER XIII. What are the functions of the eye V Give the essential parts of the eye. What are primary, sccojulary, and tertiary positions of the eye? How is an image formed on the retina? Discuss accommodation. 228 THE SPECIAL SENSES. Discuss the effect of drugs on accommodation. Give the nervous mechanisms of accommodations. Define near- and far-points and the range of accommodation. What is an emmetropic ej^e ? Discuss myopia and hypermetropia. What are presbyopia and astigmatism ? Discuss diplopia of the eye. Define spherical aberration and achromatism. Give the nervous mechanisms that control the iris. Discuss intraocular images. Why does the pupil appear black ? What is an ophthalmoscope ? What are the most important structures of the retina ? What are the blind spot, macula lutea, and fovea centralis ? How may the blind spot be demonstrated ? What is the visual purple ? How may an optogram be obtained ? What supplies the normal stimulus to the retina? Give the course of the optic fibres. What constitutes the primary vision centre? Upon what physical conditions does the sensation of light depend ? How can it be shown that luminosity is recognized more easily by the eye than color ? How do different portions of the retina vary in their power to distinguish color ? Give the various phases of the activity of the retina when stimulated. Distinguish between positive and negative after-images. What is irradiation ? What is the relation of color to white light? Discuss the color theories. How is color-blindness explained? What is the proportion of color-blind in men and women? What reason can be given for this? Discuss the perception of distance. Discuss the illusion produced by Zollner's lines. Discuss binocular vision. Discuss the correction for the inversion of the retinal image. What does clearness of vision depend upon? Where are the physical vibrations of sound transformed into nervous im- pulses ? How do the sound-waves of the air reach the organ of Corti? Are the organs of Corti absolutely essential to the appreciation of musical tones ? How are the impulses conveyed from the ear to the brain ? What is subjective hearing and its causes? Upon what factors do musical sounds depend? How do noises differ from musical sounds? What is the musical range of the ear? What is the range of audibility of the ear? How is the distance of sounds estimated? Discuss the power of the ear to appreciate small intervals of time. What is meant by equilibrium of the body? How is the sense of equilibrium brought about? What is the effect of injury to the semicircular canals of an animal? ni.rnonucTioN. 229 What proi.f is tlicrc lliai llir sciiiiciiculiir .aiials aiil in pii-scrviiiK iMjiiilil)- rium ? What is llif situatiuii of tlic Dllacloiy iiiiicdiis nicmhraiu;? Wlial is llio rdiulitidii of siiltstain-cs tlial cxcitf siiicil ? Wliat is tiu' iminprtaiuc (if siiifll in llic- lnwcr animals V (!ivf instaiu-is of tlic dclicai-y of IIil- imwvr nf smell Y (iivc tin- ciiiir.-f of l\\v (iH'aclory lilni'S. I)is<-uss till! relation of common siMisihility and .smell. What is the location of the .scnse-orKiUis of taste? What are the nerves of t.isteY What is the relation of smell to taste? Does taste (lei>eii(l npon concentration (U- on the qnantity of the stimulating .substance? How is taste divided ? Give evidence of special end-organs for each divi.sion. How does cocaine affect the seiisihility of the tongue? What is the function of the ton},'iK!? What is an after-taste? What are the orj^ans of cutaneous sensation? What sensations are included in cutaneous sensations? (live Weber's and Feehner's laws. Discuss the discriminating power of diflerent i)arts of the body to pres.snre. What interval must elapse between touch-stimuli in order that they may give .separate impressions? DiseiLss the localization of touch-sensations. What factor determines the recognition of two points of the .skin .stimuhited simultaneously? Discuss the situation of touch-areas. What fact shows that improved touch-discrimination is a central phenom- enon ? Discuss t em i)t-ra lure-sensations. What is a common sensation? Discuss the sensations of htinsrcr ami thirst. What sensations are on the border-line between common sensation and special sensation? What evidence is there for separate jiain-iioiiits in the skin? What is meant by the muscular sense? Wliat is muscular sense due to? Locate centre and give effects of injury. CHAPTER XIV. REPRODITCTTON. Reproduotiox is a process by means of whicli life is perpetu- ated because tbe existence of individuals is limited. There are tiro mcfhrxJx of reiirodiiction — the axexiinJ and the sexual. The former is the more jirimitive form, and is rostrictcil to the lower oriranisms. It is not diHicidt to conceive a reason for reproduction 230 REPRODUCTION. in cells, for as the mass of living matter increases, its volume in- creases as the cube, while its surface increases only as the square. There will finally result therefore a condition when the absorptive surface is too small for the amount of living matter, and a division will cause a relative increase of surface. Sexual reproduction is derived probably from the asexual method, and consists in the union of male and female elements. The most primitive examples are to be found in some of the unicellular organisms where there is a fusion of the two sexes, known as conjugation. The resultant mass divides and so produces its offspring. In somewhat more highly differentiated forms there are simply an exchange and a fusion of nuclear matter. In the higher animals there is a fusion of nuclear matter of two individuals brought about by the produc- tion of two kinds of sexual cells — ova and spermatozoa. In some animals, like the worms, both sexual elements exist in the same in- dividual, but this condition is found only abnormally in the highest animals. Here the sexes present wide anatomical, physiological, and psychological differences. These differences fall into two groups — jjrimary and secondary. The primary sexual characters are the most pronounced, and consist of those pertaining to the sexual organs and their functions. The secondary sexual charac- ters are accessory to the primary ones, and include the differences in voice, growth of hair on the face, the mammary glands, etc., in man and woman. The sexual cells differ widely in appearance. The spermatozoon consists of an elliptical head, a short middle piece, and a tapering tail. It is undoubtedly a cell which arises from a testicular cell known as the spermatocyte. The latter divides into four spermatids which grow directly into spermatozoa. It is important as well as interesting to know that the number of chromosomes in the head of the spermatozoon are one-half the number normally present in the body-cells of the individual. The spermatozoon is adapted to vigorous activity. It seeks the ovum by means of the movements of its tail, which is lashed from side to side, causing it to progress. and at the same time to rotate. The rapidity with which it moves is from 1.2 to 3.6 mm. per second. Spermatozoa will live in the male genital passages for months, and they probably will live in the female for a long while, but the exact time is not known. They are produced in large numbers. One estimate puts the production at 226,257,000 per week. The spermatozoa are contained in a iiu'i-jihrrrios. 231 Hnid which conies from tlie ivMrx partly, luil chiefly from acceHaunj .scrua/ (j/tiiiilx — the siiuiiKtl rcKiclrx, [\\v jnostnfr ij/mid, ami ( oirjjcr » glands. Together these coiistitiu'iits form the xvmni, which may be described as a vvliiiish viscid fluid with ii characteristic odor. The amount passed at a time is from O.o to 6 c.c. In some ani- mals it contains fihriiKxjcn, which enal)les it to clot within the female passages, thus preventing esca|)e of the spermatozoa. The arum in its j)erf'ected state as it leaves the (Irudfuni J'ol/ir/r is founil to be a minute globular cell containing a nucleus and nucleolus as well as a cell-membrane. It undergoes a process analogous to what takes place in the formation of a spermatozoon, which is known as maturation. It begins as the ovum is leaving the ovary, anil consists of a karyoJdvetlc division of the nucleus twice in succession. With each division half of the nucleus is extruded together with a small amount of protoplasm as the jtolar bodies. The first i)olar body usually divides into two parts, mak- ing three jKilar bodies, all of which degenerate. As the result of these divisions the ovum has left one-half of the nnndier of chro- mosomes of a body-cell. The union of the nuclei of ovum and spermatozo<")n restores to their original nund)er the chromosomes of the species. Ova are develoi)ed within specialized cavities of the ovarv lined bv epithelial cells known as Graafian follicles. A Graafian follicle moves toward the surface of the ovary, ruptures, and discharges the ovum, giving rise to the process of ovulation. This is in most animals a periodic phenomenon, and in woman probably begins at puberty with the first menstruation and con- tinues until the climacteric. Gases of pregnancy at the ages of seven, eight, and nine years show that it may occur very early. After the ovum has been set free from the ovary it in some unknown manner reaches the Fallopian tubes. It is possible that in woman, as has been observed in some animals, the fimbriated ends of the tubes clasp the ovaries when the eggs are discharged. The cilia lining the tubes gradually carry the Q^\i: toward the uterus, which it reaches in from four to eight days. Imprequiition or fertilization usually takes place in the tubes because the cilia, while they carry the ovum in one direction, act as a guiding stimulus to the spermatozoa, whi<'h move in the oppo- site (lirection to meet the ovum. In case the ovum is fertilized, it passes on to the uterus, where it is retained and develops to the end of the endjryonic period. 232 REPR OD UCTION. The uterus is active monthly iu that it discharges a bloody, mucous liquid through the vagina. This is called menstruation. Some days before the flow the mucous membrane of the body of the uterus begins to thicken by the growth of its connective tissue and by the engorgement of its bloodvessels until it is from two to three times its normal thickness. The swollen capillaries become rupt- ured and the epithelial cells undergo a fatty degeneration. Usually only the superficial portions of the mucous membrane are involved, and those cases where it is removed to its deepest layers are very likely pathological. The flow continues for four days or more, during which 100 to 200 c.c. of blood are lost. The latter is slimy with mucus, does not coagulate, contains disintegrated tis- sue, epithelial cells, and has a characteristic odor. Menstruation is accompanied by many other symptoms. The ovaries and breasts are congested, dark rings form about the eyes, mental depression often exists, skin and breath have a characteristic odor. The in- termenstrual period exhibits a gradual increase in nervous tension and metabolic activity, manifested in an increased production and excretion of urea, in a higher temperature, and an increase in the strength and rate of the heart-beat. These reach their maximum a few days before the menstrual flow, and then undergo a rapid fall, reaching a minimum with the cessation of the flow. The first menstruation is an index of puberty, and occurs in temperate climates at the age of from fourteen to seventeen. The time varies with the climate, food, growth, environment, etc. Occasionally menstruation may be entirely absent in otherwise normal women. The removal of the ovaries puts an end to further menstruation. Its cessation at the age of forty-five to forty-eight marks the meiv- opause or climacterie. The meaning of menstruation has been much discussed. In the lower mammalia reproduction is limited to seasonal periods, which are characterized by sexual excitement, congestion and swelling of the external genital organs, and a uterine discharge. During the remainder of the year sexual excitement is absent. These periods of excitement are known as rut or heat. Domestication with its regular food-supply and care has increased productiveness by rendering the reproductive periods more frequent. This has taken place iu like manner in the human, but has progressed further in that woman during the menstrual flow has largely lost sexual desire. According to Pfliiger, menstruation is a prepara- iiKi'iinnrcTioy. 2.'i3 tion of the uterine surface for the reception of the inipre;^nated egg. The nwclitniixui hy which the uterus is prepared is aa follows — The growth of tlie cells of the ovary reflex ly, l>y constant stiuiulalion of the spinal cord, causes a dilatation of the vessels of the genital organs, which results in a breaking down of the mucous nuMuhrane of the uterus. At the same time the increased hlood-supply causes a ripening of the (Jraaiian iollicle. It is the general view that ovulation and menstruation are the result of a conuuou cause, but either, in the human, may occur without the other. It is probable that ovulation takes place a few days before the onset of the menstrual period. ('aj>n!(tti()ii is the act of sexual union th:vt has for its object the introduction of semen into the genital passages of the female. It is preceded by a preliminary period of sexual excitement, during which the i)enis becomes swollen, turgid, and erect, while the vulva also becomes firm and turgid. There are vaf^rahir phenomena. In the penis the arteries relax, tilling the cavernous spaces with blood, while simultaneously the exit of the blood is prevented by the contractions of the erector penis and bulbocarernosKs muscles. The penis is then introduced into the vagina, and as a result of muscular movements producing friction U])on delicate sensory nerve-endiugs of the glans penis and clitoris there are produced intense nervous sensations which lead to a cUnia.r or orr/a.wi, con- sisting of the ejnnihdion of the semi)ial tluid into the upper end of the vagina. There is at the same time a secretion in the female from the r/fanrls of Bartholin, and perhaps also rhythmical opening and ckmnff of the cervical canal. Erection is a reflex act, the centre Iving in the lumbar cord. It may be aroused by im- pulses arising from the walls of the testes due to the pressure of contained semen, or from the nerve-endings in the skin of the penis or from the brain. The efferent nerves are the yiervi eri- genie!^. The clitoris is the homologue of the penis. The sexual excitement accompanying an orgasm is more intense usually in the male. The diHrhnrr/e of semen begins with power- ful peristaltic waves, probably in the rasa efferentia, and ends with rhi/thmic contractions of the ischiocavernosns and bttlbocaveniosns muscles. This is also a rellex act with the centre in the hnnbar portion of the cord. The spermatozoa ))robably reach the Fallo- pian tube mainly by their own movements, but it is possil)le that 234 BEPR OD UCTION. after coitus the uterus may exert a suction and draw them from the vagina. It is claimed by some that the uterus dips down into the pool" formed by the discharged semen. The time involved in the passage of the spermatozoa to the ovary is unknown, except that it is quite short ; in the rabbit the time is only two and three- quarters hours. When spermatozoa meet an ovum, they surround it in great numbers until one of them succeeds in uniting with the Qgg, after which the remainder perish. When fertilized, the ovum undergoes repeated segmentation, increases in bulk, histolog- ical differentiation and the physiological division of labor set in, until finally there results a new individual that is expelled at the proper time. In stick cases where more than one spermato- zoon succeeds in entering the ovum (^polyspermy) the embryo dies early. While in the uterus the growing foetus derives by far the greater part of its nourishment from the mother by means of the placenta. Here the circulation of the child is brought into intimate relation to that of the mother, but they are nevertheless separated by four layers of cells : 1. The wall of the choriouic capillary. 2. The cells of the chorion. 3. The cells of the uterine follicle. 4. The wall of the uterine sinus. Although there is no direct communication, there is an exchange of material between the mother's blood and the foetal blood. The mother's blood furnishes to the foetal blood food and oxygen, and in turn removes the carbon dioxid and excrementitious material which the foetus must lose. The placental circulation supplies the place taken in after-life by the alimentary and respiratory tracts. When the placenta is expelled, a part of the maternal tissue is left behind, and there is, of course, a loss of blood contained in the uterine sinuses, but the general balance of the circulation is not disturbed at childbirth. The reason for this is the oblique entrance of the placental vessels. They enter the sinuses at an angle, and are therefore compressed by the muscular tissue of the uterus in its contracted state. There are two distinct types of circulation in foetal life — the vitelline and the placental circulation. In both types the blood is driven on by the heart, the essential difference being the site where the foetal blood is enriched. The vitelline circulation precedes that of the placenta, and as soon as RF.vuoi) I V 'Tio.v. 2:35 tlie latter is formed the ionuer disappears. Tlie vitiHiiie ciicula- tiou ill the liiniian is very short-lived. Thii placental circitlatiuii presents two proininent lealiires in which it dif}ei*s from ai' the asexual iiii-thod. Wliy (iiK's a ;ir()\viii;{ mass of iirotoiilasm divide? What is tiif cssi-ntial Tact of sexual reiiroiliu-lion'.' Deserilte various sta;,'es in the develo|mieiit of sexual reproducticii). What are the primary and secondary sexual characters? Describe the development of a si>ermato/,oon. What diU'erence is tlu're lulween the sexual elements? lu what respects are they alike? What is the rale of movement of a spermatozoon? What is semen? What is meant hy the maturation of the ovum? What is a Ciraalian follicle? Descrihe ovulation. How does the ovum reach the uterus? What is fertiliwitiou ? Where does it take jdace? Describe the process and development of menstruation. How long does menstruation last ? What are the symptoms accompany- ing it? Give the physiological causes of menstruation. Discuss puberty. What is the menojiause? What is the object of menstruation? W'hat is the relation of ovulation to menstruation? Describe copulation. Discu.ss the erection of the penis. Discuss the nervous mechanism of an orgasm. How do spermatozoa reach the Fallopian tubes? What is polyspermy ? How many ty])es of foetal circulation are there? Describe the placental circulation. What changes take jtlace in fietal circulation at birth? What is the length of the period of gestation in the human being? From what time does it jirobablj- date? What is the earliest sign of pregnancy? What is the cause of the exjiulsion of the foetus from the uterus? Di.scu.ss the occurrence f)f twins. Discuss the determination of sex. What is the Hofacker-Sadler law? What is Schenk's hypothesis? What are the most probable determining factors of sex? Is the production of sex self-regulating? APPENDIX. CHEMICAL TESTS COMMONLY USED IN PHYSIOLOGICAL ANALYSIS. Fob Proteids : Nitric Acid coagulates all except jjeptones. Heal. — All are coagulated hy boiling, except peptones. Xanthroprotrir JiidfliDii. — A solution boiled with strong nitric acid becomes yellow: the color is deepened i)y the addition of aninjoiiia. Biuret Rcdrtioii. — With a trace of copper sulphate and an excess of po- tassiinn or sodium hydrate tliey give a purple reaction. Millon's licucliuii. — With a solution of metallic mercury in strong nitric acid (Millons reagent) they give a white or pinkish reaction, and the color becomes more pink on boiling. For Starch : Iodine Ecactioii. — Add to a solution of starch a small quantity of tincture of iodine, and a blue reaction results. The color disappears on heating and returns on cooling. (itycogen. — Same test gives reddish reaction, port-wine color, which dis- appears on heating ajid returns on cooling. For Sugar (Gluco.'^e) : Moore'?, Test. — Boil solution of sugar with an excess of potassium hydrate, brown color-reaction. Trommer's Test. — Add to solution a sufficient amount of potassium hydrate to render it quite strongly alkaline. Then add a solution of copper sulphate, drop by drop, until a distinct lilue tinge is visible. Heat, and the presence of sugar is shown by appearance of red, yellow, or orange color-reaction. Fehliiif/s Tei(t Solution. — An alkaline copper solution by which a quantita- tive test may be made. The solution is somewhat unstable, and is for this reason to be tested by boiling before using. The strength of the solution is such that 1 cubic cni. (15 minims) will be exactly decolorized by 7,-J(, of a gramme (0.075 grain) of glucose. This test is very delicate, and is quite commonly used for urinary examinations to detect glycosuria. The Fermentation Tesl.—ll' a small (juantity of yeast be addeil to a sugar solution, the fungus of the yeast (saccharomyces) will cause the sugar to be decomposed into carbonic acid and alcohol, if the process be continued until tlie sugar is entirely broken up, the amount of carbon dioxide evolved indicates the proportion of sugar present. For Bile Salts: Pettenkofer's Ti'."!. — Upon the addition of sulphuric acid to a .solution of bile-sidts in water there is a precipitation of the salts, which arc redissolved by a further addition of the acid. If a drop of a solution of cane-sugar be added, a deep cherry color is developed. 16— Phys. 241 242 APPENDIX. For Bile Pigments : Gmelin's Te-4. — Add a small quantity of nitroso-nitric acid to a solution of the bile pigments, and a play of colors results, besrinning with green and changing to blue, violet, red, ami yellow. Tliis is seen best on a white back- ground; therefore a plate is often used for this test. METRIC SYSTEM. 1 Inch -2 '3 4 1 Millimetres. 2 .3 . -t 5 6 1 7 id 1 9 10 Ceu.jnetres. The area of the figure within the heavy lines is that of a square decimetre. A cube one of whose sides is this area is a cubic decimetre or litre. A litre of water at the temperature of 4° C. weighs a Jdlofframme. A litre is 1.76 pint ; a pint is 0.568 of a litre. The smaller figures in dotted lines represent the areas of a square centimetre and of a squre inch. A cubic centimetre of water at 4° C. weighs a gramme. i i i Sqaare Inch. Sqnare : Centi- : me-.re. niPORTANT EQUIVALENTS OF THE METRIC SYSTEM. Gramme ^loi grains. Metre =39| inches. Centigramme ^ /^ grain. Milligramme = j^, grain. Kilogramme ^= 2.2 pounds. Centimetre Millimetre Micromillimetre ^1 inch. — ^ inch. — jrkins inch COMPARATIVE SCALES, showing at a glance the exact e^iulvaJent of ordinaxy weights and measurea in those of the Metric Sj-stem. and vien vena. CENTliSRAOe FAHRENHEIT OECISnAMS CENTIMETEBS _ i:i - U £ IpinC =lt) r a CUSIC _ U XO — r- 3 — 1 20 ^ « ;^ 2 50 ^—3 lrt.£jr.=60 z r aOO ETERS 1 I'J — 1 3=20 FUUlO Dh-ACHfllS cuorc CENTl 1 - ^ — - 3 ~ 4 ^ 5 I S I — ORACHMS GRAMS ; ^ — to 3 Z *— — 5 i S I — • : 3 Lr = S 1»=12- ^ '~ l/l.03. = i Tlw aqaivalents of fratftioas, whethtfr large or small, may lia Rmnd witll great nitfetj by tteae scales. For iastance. .', grain = H o f thB metric emiivalenr, of T grains, and 1-aW graitt =I-taOO of tHe metric equivalent of JO grains. Tliis mettled is, of course, reversible. •243 INDEX. ABDUCENS nerve, 190 Absorption, general principles of, bO inflnence of leucocytes on, 97 | in the large intestines, 82 in the small intestines, 81 in the stomach, 81 of fats, 82 of proteids. 81 of sugars. 82 of water and salts, 82 paths of, 81 spectrum of oxyhsfimoglobin, 95 Accommodation, 208 range of, 208 Achroodextrin, (50, 66 Acid, butyric, 50 capric, 50 caproic, 50 glycocholic, 63 hippuric. 46 hydrochloric, 39 myristic, 50 oleic, 50 palmitic, 50 stearic, 50 taurocholic, 63 uric, 46 Acquired characters, inheritance of, 27 Acromegaly, 53 Action-current in the muscles, 166 in the nerves, 166 Adenin, 46 After-birth. 77 After-images, 215 After-sensation, 225 After-taste, 224 Agomogenesis, 23 Agraphia, 203 Air, complemental, 137 residual, 137 respiratory changes in, 138 stationary, 137 Air, supplemental, 137 tidal, i:;7 Albuminoids, derivation of, 57 digestion of, 65 nutritive value of, 86 Albuminous glands, 35 Aldoses, 57 Alexia. 203 Alexine, 102 Allonomous equilibrium, 21 Amnesia, 203 Amphopeptones, 62 Aujylodextrine, 60 Amylopsin, 63 Anabolism, definition of, 21 Anelectrotonus, 156 Animal heat, source of, 14H Anode, physical definition of. 156 physiological definition of, 158 Antilytic secretion, 38 Antipeptone, 62 Antiperistalsis. intestinal, 73 Apex beat. 107 Apha.sia, 203 Aphemia, 203 Apnoea, definition of. 140 Aqueous humor, 207 Articulations, varieties of. 77 Asexual reproduction, 23, 229 Asphj-xia, 141 stages of, 141 Assimilation, general characteristics of, 22 Association centres, 207 fibres of the cortex, 184 Astigmatism. 210 Atalectiisis. 133 Atavism, 27 Auditorv nerve, cochlear portion of, 190 vestibular portion of. 192 Augmentor centre of the heart, 119 Auricular systole, duration of, 108 245 246 INDEX. Aurieuloventricular valves, 108 Autonomous equilibrium, 21 Axone, definitiou of, 169 length of, 169 BACTEEIAL decomposition in the intestines, 64 Banting diet, 88 Basophiles, 96 Bile, amount secreted, 40, 63 antiseptic action of, 64 composition of, 63 relation of, to fat absorption, 64 salts, chemical tests for, 240 Bile-acids, 63 detection of, 63 Bile-pigmeuts, 63 chemical tests for, 242 origin of, 63 Bilirubin, 63 Biliverdin, 63 Biogen, definition of, 21 Bioplasm, definition of, 21 Biuret test for proteids, 57, 240 Blind-spot, 211 Blood, circulation of, 105 coagulation of, 98 distribution of, in body, 92 functions of, 91 globucidal action of, 102 oxidations in, 92 period of ejection of the, 98 of reception of the, 99 reaction of, 92 regeneration of, after hemorrhage, 101 specific gravity of, 100 total quantity of, in the body, 91 transfusion of, 102 Blood-corpuscles, varieties of, 102 Blood-gases, 138 tension of, 139 Blood-plasma, color of, 92 composition of, 92 Blood-plates, 93 Blood -pressui-e. aortic, 121, 122 capillary, 123 changes in, 122 efi'ect of, on renal secretion, 42 methods of measuring, 122 origin of, 122 Bolometer, 165 Brain, blood supply of the, 197 growth of the, 195 specific gravity of the, 196 Brain, vasomotor activity in the, 197 Brain-weight, decrease of, during old age, 196 method of determination of, 194 relation of, to insanity, 194 to social environment, 194 table of, 193 Buffy coat, 99 pAFFEIN, action of, on kidneys, 47 \J Calcium salts, relation of, to blood clotting, 100 Calorie, definition of, 84 Calorimeter, 148 Calorimetric equivalent, 149 Calorimetry, direct and indirect, 85, 148 Capsules, suprarenal, extirpation of, 52 Carbohydrates, absorption of, in the intestines, 82 chemistry of, 57 combustion equivalent of, 84 digestion of, 66 in the intestines, 63 in the stomach, 62 dynamic value of, 87 synthesis of, 58 Carbomonoxide haemoglobin, 94 Cardiac centre, 187 cycle, analysis of, 106 definition of, 106 duration of, 108 nerves, 116 Cardiopneumatic movements, 138 Catalvsis, 59 Cell, definition of, 19, 20 differentiation, 19, 20 division, 23-30 Cells, growth of, 23 of the brain, 195 Centre, augmentor, of the heart, 119 cardiac, 187 cardio-inhibitory, 119 defecation, 75 deglutition, 72 for muscle sense, 227 micturition, 76 of speech, 203 respiratory, 160, 187, 237 sweat, 48 thermo-accelerator, 151 thermogenic, 150 thermo-inhibitory, 151 thermotactic, 187 INDEX. 247 Centre, vasomotor, 12H, 187 Ci'iitros, association, 'JO"J in tlif nicdiiUa, 1S7 ('t'lfbcllniii. illVcts of rinioval of, IH.'i functions of, l^.'i Cerebi'al lieniisjiluTcs, effects of re- moval of, 1W5 relative physiological value of, 185 Cerumen, 48 Characters, acquired, inheritance of, 27 Chemotaxis, 32 Chemotropisni, 32 C'iieyne-Stukos respiration, 136 (."iiohi};;ogut'S, 10 Chok'Sterin, (J4 of sebaceous secretion, 48 Chyme. 62 Circulating proteid, 98 Circulation, fa?tal, course of, 235. 236, 237 types of. 224 of the blood, 104, 105 of the brain and cord, 197 of the lymph, 130 l>nlni(inary, 127 rate of, 105 renal, 42 Coagulation of blood, causes of. 99 conditions necessary for, 99, 100 retarding influences affecting, 97, 9S value of. 99 Coclilear root of the auditorv nerve, 190 Coefficient of absorption of liquids for gases. 1.30 Color-blindness, 216 Color theories, 215 Colostrum corpuscles. 49 Combustion equivalent of foods. 84 Common sensation, definition of, 137 Conceptions, multiple. 237 Condiments, nutritive value of, .58 Conduction by contiguity, 160 directions of, 160 process, nature of, 160 rate of. 161 Conductivity, definition of, 18 influences afft-cting, 161 Conjugated sulphates, 46 Conjugation, 26, 230 Contractility, definition of. IH Contractions, introductory. 162 normal tetanic, nature of, 164 Contracture, definition of, Ui3 from fatigue, 163 relation of. to tctuniLS, 164 Copulation, 2.3.3 Cornea. <'urvalure of, 207 Coronary arteries, circulation in, 121 Corpora Aurantii, 109 qnadrigemina, functions of tin-. 1.S7 Corpuscles of the blood, 93 salivary, 60 Ck)rtex cerebri, effects of localized stimulation of. 182 Cortical areas, motor, 182 sensory, 184 stimulation, effect of, 178 Coughing, 145 Cranial nerves, 231 Creatin, 46 Creatinin, 46 Cresol, elimination of, 46 Crura, lesions of the, 235 Crystalline lens, 207 elasticity of, 209 Curara, action of, 153 Currents of action, diphasic character of. 167 in muscle, 166 in nerves, 166 of rest, 165 Cutaneous sensations, 224 DEATH of the tissues, 33 somatic, 33 theory of, .32. 33 Decomposition, bacterial, in the intes- tines, 64 Defecation, 75 cerebral control of. 75 Degeneration of spinal cord after hemisection. IhO Deglutition, 71 centre for, 72 nervous regulation of, 72 stages of, 71 Denmrcation currents. 165 Dendrites, definition of, 170 Determination of sex, theories regard- ing, 2.38 Deuteroprofeose. definition of, 61 Dialysis, definition of. ;i5 Diapedesis, 97 Di arthrosis. 77 Diffusion, definition of, .35 of impulses in the cord, 176 248 INDEX. Digestion, definition of, 56 gastric, 61 intestinal, 62 of fats, 58, 66 of proteids, 65 of starch, 60-66 panci-eatic, 62 salivary, 60 summary of, 65 Digitalis, action of, on the kidneys, 47 Diplopia, 210 Diuretics, action of, 44 Dropsy, 130 Du Bois-Eeymond's law, 155 I EJACULATION, 233 J Electrical phenomena in muscle and nerve, 156, 157, 158 Electrotonic changes, 156 current, definition of, 167 Emraetropia, 208 Endocardiac pressure curves. 111 Energy, potential, of foods, 84 Enzyme action, theories of, 59 Enzymes, classification of, 60 composition of, 59 definition of, 59 Eosinophiles, 96 Epigenesis, theory of, 28 Epinephrin, 52 Equilibrium, allonomous, 21 autonomous 21 carbon, 29 of the body, definition of, 221 nitrogenous, 86 sense of, 222 Erythroblasts, 96 Erythrocytes, 93 Erythrodextrin, 60 Eupnoea, definition of, 140 Excitation wave, cardiac, 113 Excretion, definition of, 35 Exercise, efi"ect of, on growth, 23 on metabolism, 89 on pulse-rate, 108 Exhaustion, 160 Expiration, forced, movements of, 135 muscles of, 135 Eye, functions of, 206 positions of, 207 FACIAL nerve, 199 Faeces, composition of, 65 Far-point, 208 Fat, combustion equivalent of, 84 Fatigue, cause of, 160 of muscle, 160, 163 of nerve, 160 production of, 196 Fats, absorption of, 63, 82 chemistry of, 58 composition of, 58 digestion of, 63, 66 dynamic value of, 88 nutritive value of, 88 origin of, in the body, 88 Fechner's law, 224 Fehling's solution, 240 Fermentation test, 240 Fertilization, 26, 231 significance of, 26, 27 Fibrin, 99 ferment, 98 origin of, 100 Fibrinogen, 98, 99 Filtration, definition of, 35 Food, combustion equivalent of, 84 composition of, 56 definition of, 22 dynamic value of, 84 Food-stufis, classification of, 56 Foramen ovale in the fcetal heart, 236 Fovea centralis, 212 Franklin theory of color vision, 215 Furfural, 64 GAMOGENESIS, 26 Gases in the blood, respiratory changes in, 139 poisonous inhalation of, 140 Gastric digestion of proteids, 61 juice, acidity of, 61 compositioii of, 61 secretion, eflect of the diet on, 39 normal mechanism of, 39 stimulants for, 39 Germ-plasm as a basis of heredity, 27 origin of, 27 28 structure of, 28 Gestation, dui-ation of, 237 Gland, mammary, 48 pancreatic, 39 parotid, 35 sublingual, 35 submaxillary, 35 thyroid, efiects of removal of, 50 Gland-cells, activity of, during secre- tion, 35 mammary, histological changes in, 50 INDEX. 249 QIaiids, albuminous, secretion from, 3.') elcctriral clianjii.'s in, 37 gastric, iS"^ intestinal, II laclirynial, -11 niucuus, secretion from, '.]iy sweat, IS elTect of exercise on, 48 of iieat on, 48 Glol)in, !»:{ tilobuciilal action of tiic blood, 10'2 Cilonuruli, renal, secretory function of, 43 Glossopharyngeal nerve, 19:2 Glycogen, amount of, in the liver, 87 in muscle, 87 function of, 87 of the liver, 52 reserve store of, 87 test for, 240 Gmellin's reaction, ()3, 240 Gra])liic niutluxl of studying muscu- lar contractions, 61 Growth, inrtuence of exercise on, 2.'5 of temperatui'c on, 31 of brain, 195 Guanin, 46 H.EMATIN, 93 rittniatopoiesis, 96 ILvniiii. 91 Hicniochroniogcn, 93 Haemoglobin, 93 compounds of. with gases, 94 decomposition products of, 93 oxygen capacity of, 93 Hallucinations, 201 Hearing, 219 subjective, 220 Heart, anannia of. 120 augmentor nerves of. 117 changes in form of, 106 compensatory pause of. 116 electrical changes of, 113 fibrillary contractions of. 120 muscle, refractory jieriod of, 116 rhythmicity of. 113 nerves of, IKi nutrition of. 120 work done by, 110 Heart-beat, conduction of, from auri- cles to ventricles, 105 heat produced by, 105 rate of. 108 Heart-sounds. 107 Heat-centres, 151 Heat-dissipation, estimation of, 149 Heat-production, estimation of, 149 Heat, source of, l.")l Heller's test, .")7 Heuiipeptone, 62 Hemisection of cord, degeneration fol- lowing in. 180 l)hysiological eH'cct of. IHI Hemorrhage, fatal, limits of, 101 regeuei-ation of l)lood after, 101 relation of, to blood jircssure, 101 Siiline injections after. 101 Heredity, definition of. 27 physical basis of, 27 theories of, 27 Hering's theory of color vision, 215 Heteroprotcose, 61 Hibernation, 199 Hiccough, 145 Hipi)uric acid, amount of, in urine, 46 source of, 46 Histon, 98 Hofacker-Sadler law, 238 Homothcrmous animals, 148 Hunger, 227 Hydrochloric acid of the gastric juice, 39 secretion of, 39 source of. 39-61 test for. 61 Hypermetropia. 209 Hypcrpncea, definition of, 140 Hypnotism, 199 Hypoglossal nerve. 193 Hypoxanthin. 46 IMPREGNATION. 231 Indol, elimination of, 46 Induction apparatus, schema of. 154 Infections, intra-uterine, 27 Inhibitory centre, cardiac. 119 respiratory. 1 13 nerves of heart. IKi of pancreas, 40 of respiration. 143. 144 of salivary glands. 37 of stomach. .39 Inorganic salts of the blood, 98 Internal secretion, definition of. .3.5 Intestines, absorption in. 81 innervation of. 7.") peristaltic movements of. 73 rhythmic movements of, 75 Intracranial pressure, 197 250 INDEX. Intraocular images, 211 Intrapulmonary pressure, 134 Intravascular clotting, 100 Introductory contractions, 162 Invertase, 64, 66 Iodine reaction for starch, 58, 240 lodothyrin, 51 Iris, 162 Irradiation, 217 Irritability, definition of, 18 Irritants, classification of, 154 Isodyuamic equivalence of foods, 85 JAUNDICE, 40 Joints, classification of, 77 movements of, 77 KAEYOKINESIS, 23, 26 Katabolisra, definition of, 21 Katelectrotonus, 156 Kathode, physical definition of, 156 physiological definition of, 158 Rations, 162 Ketoses, 57 Kidneys, blood-flow through, 42 internal secretion of, 53 vasomotor nerves of, 42 Knee-jerk, centre for the, 199 significance of, 200 variations of, 200 Kymograph, 122 LABOE, nature of, 81 physiological division of, 20 Langerhans, bodies of, 39 Language, -79 Larynx, 78 Latent areas of the cortex, 184 period of muscle, 162 of reflex actions, 176 of retinal stimulation, 214 Laughing, 146 Leucin, formation of, 62 Leucocytes, 93 classification of, 96 functions of, 97 movements of, 97 Leucocytosis, 97 Leuconuclein, 100 Life, general hypothesis of, 32 Liver, extirpation of, 46 internal secretion of, 52 urea formation in, 45 Living matter, electrical energy of, 165 inhibition of, 32 Living matter, molecular structure of, 20, 21 results of stimuli on, 28, 29 Localization of cortical cell-groups for aS"erent impulses, 182 of touch-sensations, 225 Locomotor mechanisms, 77 Lymph, composition of, 102 movements of, 103, 130 origin of, 102 pressure of, 103, 130 physical properties of, 102 Lysatinin, relation of, to urea forma- tion, 46 MACULA lutea, 212 Maltase, 66 Maltose in starch digestion, 60 Mastication, 71 Medulla, centres in the, 187 functions of the, 187 Menopause, 232 Menstruation, 232 age of onset, 231 cessation of, 232 relation of ovulation to, 233 theory of, 232 Metabolism, 83 definition of, 21 determination of, 89 during sleep, 90 starvation, 90 efiect of temperature on, 90 intensity of, in the brain, 197 internal self-adjustment of, 21 Metric system, 242 Microcytes, 93 Micturition, 75 centre for, 76 nervous mechanism of, 76 Milk, composition of, 49 reaction of, 49 Millon's test for proteid, 240 Moore's test, 240 Motor areas, degeneration of, after re- moval, 183 physiological characters of, 182 Mucous glands, 35 Multiple conceptions, 237 Muscse volitantes, 211 Muscles, absolute force of, 165 action-currents in, 166 exhaustion of, 160 fatigue of, 160 irritability of, 153 INDEX. 251 Muscles, latent i>orlod of, Ki'J reaction in, loS Muscrlc-cnrrents. asccnfi Musck'-sotinds, Kil Muscular contractions, loH Krapliic nietiiod of studying;, Uil source (»r energy in, lt)."> exen'isc, clVect of, on ^rowtii. "J.'J ou nietabolisiu, 81) on pulse-rate, 10b on sweat jilauds, 48 sense. 227 Musical sounds, characteristics of, 221 Myogram, 161 Mvo-tra])!), KU Myopia, 208 Myosin, 168 ferment, 168 Myosiiioi^'en, 167 Myx7 coiitractiirt' of. 1(>7 inlliicMcu of nervous system on, 17H nature of changes in, 1(57 Running, 7s SALIVA, composition of, t>0 proiH-rties of, tJO source of, 3.") uses of, (JO Salivary cori)uscles, HO glands, ner\es of, 37 secretion, action of drugs on, 38 cerebral control of, 37 normal mechauisni of, S8 Salts, calcium, uses of, s9 elimination of, 88 inorganic, of the urine, 47 nutritive value of, 58, 88 of iron, importance of, 89 Schenk's theory, 2:iS Sebaceous secretion, 48 Secreting glands, histological changes in, 3G, 37 Secretion, antilytic, 38 biliary, 40 circulatory factors in, 37 definition of, 34 gastric, 39 intestinal, 41 mammary. 48 pancreatic. 40 paralytic, 3::* salivary, 35 action of drugs on, 38 cerebral control of, 37 sebaceous, character of, 48 function of, 48 sweat, 47 thyroid, 50 urinary, 42 Secretions, general characteristics of, :J4, 3.-> Secretorv nerves, mofle of action of, 37, 38 of kidney, 42 of liver, 40 of pancreas, 40 of stomach. 3!) of sweat glands, 48 Segmentation, 2.'U Seiiiiliinar valves. 108 Sensation, common, definition of, 224 . Sense of touch, '22ii Sensory cortical areas, motor responses I from, 1*1 Sex of olTspring, determination of, 238 . Sexual characters, 2^J0 elements. 230 I reproduction, 23, 2(i, 229 ! Shivering, l.">0 ! Shock, nature of, 173 Sighing, 145 Singing, 115 Skatol. elimination of, 46 Sleep, cause of. I!t7 condition of the pupils in, 198 effect of loss of. 198 on metabolism, 90 ' Smegma prseputii, 48 i Smell. 222 ; Sneezing, 145 Sniffing, 146 Sobbing, 146 Sodium chloride, amount of, in the I urine, 47 Somatic death, :i3 Speaking, 115 Specific gravitv of urine, 44 Spectrum, 95, 96 ; Speech, dependence upon hearing, 203 j elements of, 202 i Speech-centre, 203 I Spermatids. 230 '. Spermatocyte, 230 ! Spermatozoa, movements of, 230 Sphj-gmogram, 125 Sphygmograph, 125 Spinal accessory nerve, 193 cord, degeneration of, from hemi- section, ISO results of section of the, 187 weight of, 195 Splanchnic nerves, gastric fibres of, 39 influence of, on bile secretion, 40 on blood pressure, 119 Spleen, function of, 53 rhythmic movements of, 54 vasomotor nerves of, 54 Staircase contractions, 162 Standing, 78 Starch, chemical test for, 58, 240 digestion of, 60, 63 hydrolysis of, .58 Steapsin, 63 Stensou's experiment. 1.59 254 INDEX. Stimulation of the cortex, 178 Stimuli, classification of, 28 definition of, 154 efi"ect of changing intensity of, 155 varying strength of, 155 results of, on living matter, 28, 29 Stomach, absorption in, 81 glands of, 39 immunity of, to its own secretion, 67 innervation of, 72 movements of, 72 Strabismus, 210 Succus entericus, 64 ferments of, 64 Sucking, 146 Sugars, absorption of, in the intestines, 82 in the stomach, 81 chemical tests for, 240 Supplemental air, definition of, 137 Suprarenal capsules, 52 Suture, 77 Sympathetic nerves, cardiac fibres of, 116 postganglionic fibres, 176 preganglionic fibres, 176 secretory fibres, to pancreas, 40 to salivary glands, 37 to stomach, 39 stimulation, efiect of, on heart, 117 Symphysis, 77 Syndesmosis, 77 Synovial fluid, 41 Syutonin, 61 Systole, auricular, 108 ventricular, 105 TACTILE areas of the skin, 225 Taste, nerves of, 223 organs of, 223 Taste-buds, 223 Taste-sensations, 223 Tears, 41 Temperature, effect of, on growth, 31 nerves, 226 postmortem rise of, 151 sense, 226 variations of, 148 Tension of the blood gases, 139 Testes, internal secretion of, 52 Testicular extract, eflTect of, 53 Tetanus, analysis of, 164 secondary, 167 Thernio-accelerator centres, 151 Thermogenesis, 150 Thermogenesis, mechanism of, 150 Thermo-inhibitory centres, 151 Thermolysis, 150 mechanism of, 151 Thermopile, 165 Thermotactic centre, 187 Therm otaxis, 150 Thirst, 227 Thiry-Vella fistula, 64 Thymus gland, 53 Thyroidectomy, 50 Thyroids, function of, 51 grafting of, 51 internal secretion of, 51 Tidal air, definition of, 137 Tissue proteid, 85 Tonus, muscular, in the insane, 177 reflex origin of, 176 Transfusion of blood, 102 Traube-Hering waves, 129 Trigeminal nerves, 189 Trommer's test, 240 Trophic nerves of the salivary glands, 38 Trypsin, 62 Trj'ptic digestion, products of, 62 value of, 62 Tyrosin, formation of, 62 UEEA, amount of, in the urine, 45 antecedents of, 45 elimination of, 44 formation of, in the liver, 58 origin of, in the body, 45 in the liver, 45 preparation of, from proteid, 45 presence of, in the sweat, 48 Uric acid, formation of, in the liver, 46 origin of, in birds, 46 Urine, acidity of, 44 constituents of the, 45 estimation of solids, 44 secretion of, 43 specific gravity of, 44 Urobilin, 44 VAGUS, afferent fibres of the, 193 cardiac fibres of, 116 effect on heart, 119 gastric branches of, 39-72 respiratory function of, 145 secretory fibres, to pancreas, 40 to stomach, 39 stimulative effect of, on heart, 116 IXPhX. Valves, iiuriculovoiitricular. inr> sciiiilmiar, HI.") Ids N'alvulii' roiinivoiiti'S, value of, in ab- sorption, 81 Vasoconstrictor nerves, definition of, 1J7 \a.so(lilator ncrve.s, dclinilion of, 127 Viusoniotor centre, 187 inedullary, 128 centres, spinal, 128 synipatlietic, 128 nerves, 127 reflexes, orifiin of, 129 Vein, entrance of air into, 124 pulsation in, cause of, 110 reual, eflect of compression on uri- nary secretion, 44 Vena? f hcbesii, 120 Venous jiulse, resjtiratory, 123 Ventricular systole, duration of, 108 Ventrilotiuism, 221 Vernix caseosa, 48 Vestibular root of auditory nerve, 192 Vision, binocular. 218 clearness of, 219 Visual purple, 212 Vital capacity of the lungs, 137 Vitreous humor, 207 Voice, 79 pitch of, 79 Voice, register of, 79 V(»luntarv reactions, afferent paths rif, 178 Vomiting, 73 causes of, 73 centres for, 73 nervous mechanism of, 73 WALKING, 7H Wandering cells, definition of. 97 Water, amount lost tliroujih lungs, 138 elimination of, 4() imbibition of, 88 nutritive value of, 88 Weber's law, 224 I Whispering, 79 I XANTHIN, 4B Xantho-proteic reaction. 240 YAWNING. M(! Young-Helinboltz theory of color vision, 215 ZOLLNER'S lines, 217 Zymogen granules, definition of, ■37 COLUMBIA UNIVERSITY This hook is due on the date indicated below, or at the expiration of a definite period after the date of borrowing, as provided by tlie rules of the Library or l:)y special ar- rangement with the Librarian in charge. DATE BORROWED DATE DUE DATE BORROWED DATE DUE C28!e38)M50 QP40 Guenther G93