GIFT OF 
 
 BIOLOGY 
 
 LIBRARY 
 
 G 
 
BLAISDELL'S SERIES OF PHYSIOLOGIES 
 
 BY ALBERT F. BLAISDELL, M.D. 
 
 CHILD'S BOOK OF HEALTH. 
 
 In easy lessons for primary grades. Fully illustrated. For intro- 
 duction, 30 cents. 
 
 HOW TO KEEP WELL. 
 
 A text-book of health for the lower gradet. For introduction, 45 
 cents. 
 
 OUR BODIES AND HOW WE LIVE. 
 
 An elementary text-book of physiology and hygiene for use in 
 schools. For introduction, 65 cents. 
 
 A PRACTICAL PHYSIOLOGY. 
 
 A text-book for higher schools. For introduction, $1.10. 
 
 HOW TO TEACH PHYSIOLOGY. 
 
 A handbook for teachers. Paper. Fully illustrated. Price, 10 
 cents. 
 
 GINN & COMPANY, PUBLISHERS. 
 
PRACTICAL PHYSIOLOGY 
 
 A TEXT-BOOK FOR HIGHER SCHOOLS 
 
 ALBERT F. BLAISDELL, M.D. 
 
 AUTHOR OF "CHILD'S BOOK OF HEALTH," "HOW TO KEEP WELL," 
 
 "OUR BODIES AND HOW WE LIVE," ETC., ETC. 
 
 BOSTON, U.S.A., AND LONDON 
 GINN & COMPANY, PUBLISHERS 
 
 1900 
 
BIOLOGY 
 LIBRARY 
 
 3 
 
 A 
 
 
 COPYRIGHT, 1897, B Y 
 ALBERT F. BLAISDELL 
 
 ALL RIGHTS RESERVED 
 

 PREFACE. 
 
 THE author has aimed to prepare a text-book on human 
 physiology for use in higher schools. The design of the book 
 is to furnish a practical manual of the more important facts 
 and principles of physiology and hygiene, which will be 
 adapted to the needs of students in high schools, normal 
 schools, and academies. 
 
 Teachers know, and students soon learn to recognize the 
 fact, that it is impossible to obtain a clear understanding of 
 the functions of the various parts of the body without first 
 mastering a few elementary facts about their structure. The 
 course adopted, therefore, in this book, is to devote a certain 
 amount of space to the anatomy of the several organs before 
 describing their functions. 
 
 A mere knowledge of the facts which can be gained in 
 secondary schools, concerning the anatomy and physiology of 
 the human body, is of little real value or interest in itself. 
 Such facts are important and of practical worth to young 
 students only so far as to enable them to understand the rela- 
 tion of these facts to the great laws of health and to apply 
 them to daily living. Hence, it has been the earnest effort 
 of the author in this book, as in his other physiologies for 
 schools, to lay special emphasis upon such points as bear upon 
 personal health. 
 
 Physiology cannot be learned as it should be by mere book 
 study. The result will be meagre in comparison with the capa- 
 
 451362 
 
iv PREFACE. 
 
 bilities of the subject. The study of the text should always 
 be supplemented by a series of practical experiments. Actual 
 observations and actual experiments are as necessary to illumi- 
 nate the text and to illustrate important principles in physi- 
 ology as they are in botany, chemistry, or physics. Hence, as 
 supplementary to the text proper, and throughout the several 
 chapters, a series of carefully arranged and practical experi- 
 ments has been added. For the most part, they are simple and 
 can be performed with inexpensive and easily obtained appara- 
 tus. They are so arranged that some may be omitted and 
 others added as circumstances may allow. 
 
 If it becomes necessary to shorten the course in physiology, 
 the various sections printed in smaller type may be omitted or 
 used for home study. 
 
 The laws of most of the states now require in our public 
 schools the study of the effects of alcoholic drinks, tobacco, and 
 other narcotics upon the bodily life. This book will be found 
 to comply fully with all such laws. 
 
 The author has aimed to embody in simple and concise lan- 
 guage the latest and most trustworthy information which can 
 be obtained from the standard authorities on modern physiol- 
 ogy, in regard to the several topics. 
 
 In the preparation of this text-book the author has had the 
 editorial help of his esteemed friend, Dr. J. E. Sanborn, of 
 Melrose, Mass., and is also indebted to the courtesy of 
 Thomas E. Major, of Boston, for assistance in revising the 
 proofs. 
 
 ALBERT F. BLAISDELL. 
 
 BOSTON, August, 1897. 
 
CONTENTS. 
 
 CHAPTER I. 
 
 INTRODUCTION . . . ... . 
 
 CHAPTER II. 
 THE BONES ...... . . . . . -21 
 
 CHAPTER III. 
 THE MUSCLES ........... 57 
 
 CHAPTER IV. 
 PHYSICAL EXERCISE ....... - ... 78 
 
 CHAPTER V. 
 FOOD AND DRINK .......... 97 
 
 CHAPTER VI. 
 DIGESTION ............ 119 
 
 CHAPTER VII. 
 THE BLOOD AND ITS CIRCULATION ....... 169 
 
 CHAPTER VIII. 
 RESPIRATION ........... 202 
 
 CHAPTER IX. 
 THE SKIN AND THE KIDNEYS ........ 235 
 
VI CONTENTS. 
 
 CHAPTER X. PAGE 
 
 THE NERVOUS SYSTEM 263 
 
 CHAPTER XI. 
 THE SPECIAL SENSES . 307 
 
 CHAPTER XII. 
 THE THROAT AND THE VOICE 356 
 
 CHAPTER XIII. 
 ACCIDENTS AND EMERGENCIES 367 
 
 CHAPTER XIV. 
 
 IN SICKNESS AND IN HEALTH , 386 
 
 Care of the Sick-Room, 386; Poisons and their Antidotes, 391; 
 Bacteria, 395 ; Disinfectants, 400 ; Management of Contagious 
 Diseases, 402. 
 
 CHAPTER XV. 
 
 EXPERIMENTAL WORK IN PHYSIOLOGY 405 
 
 Practical Experiments, 405 ; Use of the Microscope^ 407 ; Additional 
 Experiments, 409; Surface Anatomy and Landmarks, 415. 
 
 GLOSSARY . . . . . 421 
 
 INDEX 439 
 
PRACTICAL PHYSIOLOGY. 
 
 CHAPTER I. 
 
 INTRODUCTION. 
 
 I. The Study of Physiology. We are now to take up a 
 new study, and in a field quite different from any we have thus 
 far entered. Of all our other studies, mathematics, physics, 
 history, language, not one comes home to us with such pecu- 
 liar interest as does physiology, because this is the study of 
 ourselves. 
 
 Every thoughtful young person must have asked himself ^ 
 hundred questions about the problems of human life : how it 
 can be that the few articles of our daily food milk, bread, 
 meats, and similar things build up our complex bodies, and 
 by what strange magic they are transformed into hair, skin, 
 teeth, bones, muscles, and blood. 
 
 How is it that we can lift these curtains of our eyes an$ behold 
 all the wonders of the world around us, then drop the lids, and 
 though at noonday, are instantly in total darkness? How does 
 the minute structure of the ear report to us with equal accuracy 
 the thunder of the tempest, and the hum of the passing bee ? 
 Why is breathing so essential to our life, and why cannot we 
 stop breathing when we try ? Where within us, and how, burns 
 the mysterious fire whose subtle heat warms us from the first 
 breath of infancy till the last hour of life ? 
 
2 PRACTICAL PHYSIOLOGY. 
 
 These and scores of similar questions it is the province of 
 this deeply interesting study of physiology to answer. 
 
 2. What Physiology should Teach us. The study of phys- 
 iology is not only interesting, but it is also extremely useful. 
 Every reasonable person should not only wish to acquire the 
 knowledge how best to protect and preserve his body, but 
 should feel a certain profound respect for an organism so won- 
 derful and so perfect as his physical frame. For our bodies 
 are indeed not ourselves, but the frames that contain us, the 
 ships in which we, the real selves, are borne over the sea of 
 life. He must be indeed a poor navigator who is not zealous 
 to adorn and strengthen his ship, that it may escape the rocks 
 of disease and premature decay, and that the voyage of his life 
 may be long, pleasant, and successful. 
 
 But above these thoughts there rises another, that in study- 
 ing physiology we are tracing the myriad lines of marvelous 
 ingenuity and forethought, as they appear at every glimpse of 
 the work of the Divine Builder. However closely we study our 
 bodily structure, we are, at our best, but imperfect observers 
 of the handiwork of Him who made us as we are. 
 
 3. Distinctive Characters of Living Bodies. Even a very 
 meagre knowledge of the structure and action of our bodies 
 is enough to reveal the following distinctive characters : our 
 bodies are continually breathing, that is, they take in oxygen 
 from the surrounding air ; they take in certain substances 
 known as food, similar Jo those composing the body, which are 
 capable through a process called oxidation, or through other 
 chemical changes, of setting free a certain amount of energy. 
 
 Again, our bodies are continually making heat and giving 
 it out to surrounding objects, the production and the loss of 
 heat being so adjusted that the whole body is warm, that is, 
 of a temperature higher than that of surrounding objects. Our 
 
INTRODUCTION. 3 
 
 bodies, also, move themselves, either one part on another, or 
 the whole body from place to place. The motive power is not 
 from the outside world, but the energy of their movements 
 exists in the bodies themselves, influenced by changes in their 
 surroundings. Finally, our bodies are continually getting rid 
 of so-called waste matters, which may be considered products 
 of the oxidation of the material used as food, or of the sub- 
 stances which make up the organism. 
 
 4. The Main Problems of Physiology briefly Stated. We 
 
 shall learn in a subsequent chapter that the living body is con- 
 tinually losing energy, but by means of food is continually 
 restoring its substance and replenishing its stock of energy. 
 A great deal of energy thus stored up is utilized as mechanical 
 work, the result of physical movements. We shall learn later 
 on that much of the energy which at last leaves the body as 
 heat, exists for a time within the organism in other forms than 
 heat, though eventually transformed into heat. Even a slight 
 change in the surroundings of the living body may rapidly, 
 profoundly, and in special ways affect not only the amount, but 
 the kind of energy set free. Thus the mere touch of a hair 
 may lead to such a discharge of energy, that a body previously 
 at rest may be suddenly thrown into violent convulsions. This 
 is especially true in the case of tetanus, or lockjaw. 
 
 The main problem we have to solve in the succeeding pages 
 is to ascertain how it is that our bodies can renew their sub- 
 stance and replenish the energy which they are continually 
 losing, and can, according to the nature of their surroundings, 
 vary not only the amount, but the kind of energy which they 
 set free. 
 
 5. Technical Terms Defined. All living organisms are 
 studied usually from two points of view : first, as to their form 
 and structure ; second, as to the processes which go on within 
 
4 PRACTICAL PHYSIOLOGY. 
 
 them. The science which treats of all living organisms is 
 called biology. It has naturally two divisions, morphology, 
 which treats of the form and structure of living beings, and 
 physiology, which investigates their functions, or the special 
 work done in their vital processes. 
 
 The word anatomy, however, is usually employed instead of 
 morphology. It is derived from two Greek words, and means 
 the science of dissection. Human anatomy then deals with 
 the form and structure of the human body, and describes how 
 the different parts and organs are arranged, as revealed by 
 observation, by dissection, and by the microscope. 
 
 Histology is that part of anatomy which treats of the 
 minute structure of any part of the body, as shown by the 
 microscope. 
 
 Human physiology describes the various processes that go 
 on in the human body in health. It treats of the work done 
 by the various parts of the body, and of the results of the 
 .harmonious action of the several organs. Broadly speaking, 
 physiology is the science which treats of functions. By the 
 word function is meant the special work which an organ has 
 to do. An organ is a part of the body which does a special 
 work. Thus the eye is the organ of sight, the stomach of 
 digestion, and the lungs of breathing. 
 
 It is plain that we cannot understand the physiology of our 
 bodies without a knowledge of their anatomy. An engineer 
 could not understand the working of his engine unless well 
 acquainted with all its parts, and the manner in which they 
 were fitted together. So, if we are to understand the principles 
 of elementary physiology, we must master the main anatomical 
 facts concerning the organs of the body before considering 
 their special functions. 
 
 As a branch of study in our schools, physiology aims to 
 make clear certain laws which are necessary to health, so that 
 by a proper knowledge of them, and their practical applica- 
 
INTRODUCTION. 5 
 
 tk 
 
 tion, we may hope to spend happier and more useful, because 
 healthier, lives. In brief, the study of hygiene, or the science 
 of health, in the school curriculum, is usually associated with 
 that of physiology. 1 
 
 6. Chemical Elements in the Body. All of the various 
 complex substances found in nature can be reduced by chemi- 
 cal analysis to about 70 elements, which cannot be further 
 divided. By various combinations of these 70 elements all the 
 substances known to exist in the world of nature are built up. 
 When the inanimate body, like any other substance, is sub- 
 mitted to chemical analysis, it is found that the bone, 
 muscle, teeth, blood, etc., may be reduced to a few chemical 
 elements. 
 
 In fact, the human body is built up with 13 of the 70 
 elements, namely : oxygen, hydrogen, nitrogen, chlorine, 
 fluorine, carbon, phosphorus, sulphur, calcium, potassium, 
 sodium, magnesium, and iron. Besides these, a few of the 
 other elements, as silicon, have been found ; but they exist in 
 extremely minute quantities. 
 
 1 The Value of Physiological Knowledge. " If any one doubts the impor- 
 tance of an acquaintance with the fundamental principles of physiology as a means 
 to complete living, let him look around and see how many men and women he can 
 find in middle life, or later, who are thoroughly well. Occasionally only do we meet 
 with an example of vigorous health continued to old age ; hourly do we meet with 
 examples of acute disorder, chronic ailment, general debility, premature decrepitude. 
 Scarcely is there one to whom you put the question, who has not, in the course of his 
 life, brought upon himself illness from which a little knowledge would have saved 
 him. Here is a case of heart disease consequent on a rheumatic fever that followed 
 a reckless exposure. There is a case of eyes spoiled for life by overstudy. 
 
 " Not to dwell on the natural pain, the gloom, and the waste of time and money 
 thus entailed, only consider how greatly ill health hinders the discharge of all duties, 
 makes business often impossible, and always more difficult; produces irritability 
 fatal to the right management of children, puts the functions of citizenship out of the 
 question, and makes amusement a bore. Is it not clear that the physical sins 
 partly our ancestors' and partly our own which produce this ill health deduct more 
 from complete living than anything else, and to a great extent make life a failure 
 and a burden, instead of a benefaction and a pleasure?" HERBERT SPENCER. 
 
O PRACTICAL PHYSIOLOGY. 
 
 The following table gives the proportion in which these 
 various elements are present : 
 
 Oxygen 62.430 per cent 
 
 Carbon 21.150 " " 
 
 Hydrogen . 9.865 " " 
 
 Nitrogen 3.100 " " 
 
 Calcium 1.900 " " 
 
 Phosphorus . . 0.946 " " 
 
 Potassium 0.230 " " 
 
 Sulphur 0.162 " " 
 
 Chlorine 0.081 " " 
 
 Sodium 0.081 " " 
 
 Magnesium 0.027 " " 
 
 Iron 0.014 " " 
 
 Fluorine 0.014 " 
 
 100.000 
 
 As will be seen from this table, oxygen, hydrogen, and nitro- 
 gen, which are gases in their uncombined form, make up f of 
 the weight of the whole human body. Carbon, which exists in 
 an impure state in charcoal, forms more than of the weight 
 of the body. Thus carbon and the three gases named, make 
 up about 96 per cent of the total weight of the body. 
 
 7. Chemical Compounds in the Body. We must keep in 
 mind that, with slight exceptions, none of these 13 elements 
 exist in their elementary form in the animal economy. They 
 are combined in various proportions, the results differing 
 widely from the elements of which they consist. Oxygen and 
 hydrogen unite to form water, and water forms more than of 
 the weight of the whole body. In all the fluids of the body, 
 water acts as a solvent, and by this means alone the circulation 
 of nutrient material is possible. All the various processes of 
 secretion and nutrition depend on the presence of water for 
 their activities. 
 
INTRODUCTION. 7 
 
 8. Inorganic Salts. t A large number of the elements of the 
 body unite one with another by chemical affinity and form inor- 
 ganic salts. Thus sodium and chlorine unite and form chloride 
 of sodium, or common salt. This is found in all the tissues 
 and fluids, and is one of the most important inorganic salts the 
 body contains. It is absolutely necessary for continued existence. 
 By a combination of phosphorus with sodium, potassium, cal- 
 cium, and magnesium, the various phosphates are formed. 
 
 The phosphates of lime and soda are the most abundant of 
 the salts of the body. They form more than half the material 
 of the bones, are found in the teeth and in other solids and 
 in the fluids of the body. The special place of iron is in the 
 coloring matter of the blood. Its various salts are traced in 
 the ash of bones, in muscles, and in many other tissues and 
 fluids. These compounds, forming salts or mineral matters 
 that exist in the body, are estimated to amount to about 6 per 
 cent of the entire weight. 
 
 9. Organic Compounds. Besides the inorganic materials, 
 there exists in the human body a series of compound substances 
 formed of the union of the elements just described, but which 
 require the agency of living structures. They are built up 
 from the elements by plants, and are called organic. Human 
 beings and the lower animals take the organized materials they 
 require, and build them up in their own bodies into still more 
 highly organized forms. 
 
 The organic compounds found in the body are usually 
 divided into three great classes : 
 
 i,. Proteids, or albuminous substances. 
 
 2. Carbohydrates (starches, sugars, and gums). 
 
 3. Fats. 
 
 The extent to which these three great classes of organic ma- 
 terials of the body exist in the animal and vegetable kingdoms, 
 and are utilized for the food of man, will be discussed in the 
 
8 PRACTICAL PHYSIOLOGY. 
 
 chapter on food (Chapter V.). The Proteids, because they 
 contain the element nitrogen and the others do not, are fre- 
 quently called nitrogenous, and the other two are known as 
 non-nitrogenous substances. The proteids, the type of which 
 is egg albumen, or the white of egg, are found in muscle and 
 nerve, in glands, in blood, and in nearly all the fluids of the 
 body. A human body is estimated to yield on an average 
 about 1 8 per cent of albuminous substances. In the succeed- 
 ing chapters we shall have occasion to refer to various and 
 allied forms of proteids as they exist in muscle (myosin), 
 coagulated blood (fibrin), and bones (gelatin). 
 
 The Carbohydrates are formed of carbon, hydrogen, and 
 oxygen, the last two in the proportion to form water. Thus we 
 have animal starch, or glycogen, stored up in the liver. Sugar, 
 as grape sugar, is also found in the liver. The body of an average 
 . man contains about 10 per cent of Fats. These are formed of 
 carbon, hydrogen, and oxygen, in which the latter two are not 
 in the proportion to form water. The fat of the body consists 
 of a mixture which is liquid at the ordinary temperature. 
 
 Now it must not for one moment be supposed that the 
 various chemical elements, as the proteids, the salts, the fats, 
 etc., exist in the body in a condition to be easily separated one 
 from another. Thus a piece of muscle contains all the various 
 organic compounds just mentioned, but they are combined, and 
 in different cases the amount will vary. Again, fat may exist 
 in the muscles even though it is not visible to the naked eye, 
 and a microscope is required to show the minute fat cells. 
 
 10. Protoplasm. The ultimate elements of which the body 
 is composed consist of " masses of living matter," microscopic 
 in size, of a material commonly called protoplasm. 1 In its 
 
 1 The word protoplasm must not be misunderstood to mean a substance of a 
 definite chemical nature, or of an invariable morphological structure ; it is applied to 
 any part of a cell which shows the properties of life, and is therefore only a conve- 
 nient abbreviation for the phrase " mass of living matter." 
 
INTRODUCTION. 9 
 
 simplest form protoplasm appears to be a homogeneous, struc- 
 tureless material, somewhat resembling the raw white of an 
 egg. It is a mixture of several chemical substances and differs 
 in appearance and composition in different parts of the body. 
 
 Protoplasm has the power of appropriating nutrient material, 
 of dividing and subdividing, so as to form new masses like 
 itself. When not built into a tissue, it has the power of chang- 
 ing its shape and of moving from place to place, by means of 
 the delicate processes which it puts forth. Now, while there 
 are found in the lowest realm of animal life, organisms like 
 the amoeba of stagnant pools, consisting of nothing more than 
 minute masses of protoplasm, there are 
 others like them which possess a small 
 central body called a nucleus. This is 
 known as nucleated protoplasm. 
 
 II. Cells. When we carry back the 
 analysis of an organized body as far as 
 we can, we find every part of it made up FiG.i.-Diagr^mof a Cell. 
 of masses of nucleated protoplasm of A , nucleus; B, 
 
 various sizes and shapes. In all essential c > protoplasm. (Highly 
 
 magnified.) 
 
 features these masses conform to the type 
 
 of protoplasmic matter just described. Such bodies are called 
 cells. In many cells the nucleus is finely granular or reticu- 
 lated in appearance, and on the threads of the meshwork may 
 be one or more enlargements, called nucleoli. In some cases 
 the protoplasm at the circumference is so modified as to give 
 the appearance of a limiting membrane called the cell wall. In 
 brief, then, a cell is a mass of nucleated protoplasm ; the 
 nucleus may have a nucleolus, and the cell may be limited by a 
 cell wall. Every tissue of the human body is formed through 
 the agency of protoplasmic cells, although in most cases the 
 changes they undergo are so great that little evidence remains 
 of their existence. 
 
IO PRACTICAL PHYSIOLOGY. 
 
 There are some organisms lower down in the scale, whose 
 whole activity is confined within the narrow limits of a single 
 cell. Thus, the amoeba begins its life as a cell split off from its 
 parent. This divides in its turn, and each half is a complete 
 amoeba. When we come a little higher than the amoeba, we find 
 organisms which consist of several cells, and a specialization 
 of function begins to appear. As we ascend in the animal 
 scale, specialization of structure and of function is found con- 
 tinually advancing, and the various kinds of cells are grouped 
 together into colonies or organs. 
 
 12. Cells and the Human Organism. If the body be 
 studied in its development, it is found to originate from a single 
 mass of nucleated protoplasm, a single cell with a nucleus and 
 
 FIG. 2. Amoeboid Movement of a Human White Blood Corpuscle. 
 (Showing various phases of movement.) 
 
 nucleolus. From this original cell, by growth and development, 
 the body, with all its various tissues, is built up. Many fully 
 formed organs, like the liver, consist chiefly of cells. Again, 
 the cells are modified to form fibers, such as tendon, muscle, 
 and nerve. Later on, we shall see the white blood corpuscles 
 exhibit all the characters of the amoeba (Fig. 2). Even such 
 dense structures as bone, cartilage, and the teeth are formed 
 from cells. 
 
 In short, cells may be regarded as the histological units of 
 animal Structures ; by the combination, association, and modi- 
 fication of these the body is built up. Of the real nature of 
 the changes going on within the living protoplasm, the process 
 of building up lifeless material into living structures, and the 
 
INTRODUCTION. 1 1 
 
 process of breaking down by which waste is produced, we know 
 absolutely nothing. Could we learn that, perhaps we should 
 know the secret of life. 
 
 13. Kinds of Cells. Cells vary greatly in size, some of 
 the smallest being only ^^QTF ^ an * ncn or ^ ess m diameter. 
 They also vary greatly in form, as maybe seen in Figs. 3 and 5. 
 The typical cell is usually globular in form, other shapes being 
 the result of pressure or of similar modifying influences. The 
 globular, as well as the large, flat cells, are well shown in a 
 drop of saliva. Then there are the columnar cells, found in 
 various parts of the intestines, in which they are closely 
 arranged side by side. These cells sometimes have on the free 
 surface delicate prolongations called cilia. Under the micro- 
 scope they resemble a wave, as when the wind blows over 
 a field of grain (Fig. 5). There are besides cells known as 
 spindle, stellate, squamous or pavement, and various other names 
 suggested by their shapes. Cells are also described as to their 
 contents. Thus fat and pigment cells are alluded to in suc- 
 ceeding sections. Again, they may be described as to their 
 functions or location or the tissue in which they are found, 
 as epithelial cells, blood cells (corpuscles, Figs. 2 and 66), 
 nerve cells (Fig. 4), and connective-tissue cells. 
 
 14. Vital Properties of Cells. Each cell has a life of its 
 own. It manifests its vital properties in that it is born, grows, 
 multiplies, decays, and at last dies. 1 During its life it assimi- 
 lates food, works, rests, and is capable of spontaneous motion 
 
 1 " Did we possess some optic aid which should overcome the grossness of our 
 vision, so that we might watch the dance of atoms in the double process of making 
 and unmaking in the living body, we should see the commonplace, lifeless things 
 which are brought by the blood, and which we call food, caught up into and made 
 part of the molecular whorls of the living muscle, linked together for a while in the 
 intricate figures of the dance of life, giving and taking energy as they dance, and then 
 we should see how, loosing hands, they slipped back into the blood as dead, inert, 
 used-up matter." MICHAEL FOSTER, Professor of Physiology in the University 
 of Cambridge, England. 
 
12 
 
 PRACTICAL PHYSIOLOGY. 
 
 and frequently of locomotion. The cell can secrete and excrete 
 substance, and, in brief, presents nearly all the phenomena of 
 a human being. 
 
 Cells are produced only from cells by a process of self-divi- 
 sion, consisting of a cleavage of the whole cell into parts, each 
 of which becomes a separate and independent organism. Cells 
 rapidly increase in size up to a certain definite point which 
 they maintain during adult life. A most interesting quality of 
 
 cell life is motion, a beauti- 
 ful form of which is found 
 in ciliated epithelium. Cells 
 may move actively and pas- 
 sively. In the blood the 
 cells are swept along by the 
 current, but the white cor- 
 puscles seem able to make 
 their way actively through 
 the tissues, as if guided by 
 some sort of instinct. 
 
 Some cells live a brief life 
 of 12 to 24 hours, as is prob- 
 ably the case with many of the cells lining the alimentary canal ; 
 others may live for years, as do the cells of cartilage and bone. 
 In fact each cell goes through the same cycle of changes as 
 the whole organism, though doubtless in a much shorter time. 
 The work of cells is of the most varied kind, and embraces the 
 formation of every tissue and product, solid, liquid, or gaseous. 
 Thus we shall learn that the cells of the liver form bile, those 
 of the salivary glands and of the glands of the stomach and 
 pancreas form juices which aid in the digestion of food. 
 
 15. The Process of Life. All living structures are subject 
 to constant decay. Life is a condition of incessant changes, 
 dependent upon two opposite processes, repair and decay. 
 
 FIG. 3. Various Forms of Cells. 
 
 A, columnar cells found lining various parts of 
 the intestines (called columnar epithelium); 
 B, cells of a fusiform or spindle shape found 
 in the loose tissue under the skin and in other 
 parts (called connective-tissue cells); C, cell 
 having many processes or projections such 
 are found in connective tissue ; D, primitive 
 cells composed of protoplasm with nucleus, 
 and having no cell wall. All are represented 
 about 400 times their real size. 
 
INTRODUCTION. 13 
 
 Thus our bodies are not composed of exactly the same particles 
 from day to day, or even from one moment to another, although 
 to all appearance we remain the same individuals. The change 
 is so gradual, and the renewal of that which is lost may be so 
 exact, that no difference can be noticed except at long intervals 
 of time. 1 (See under " Bacteria," Chapter XIV.) 
 
 The entire series of chemical changes that take place in the 
 living body, beginning with assimilation and ending with excre- 
 tion, is included in one word, metabolism. The process of 
 building up living material, or the change by which complex 
 substances (including the living matter itself) are built up from 
 simpler materials, is called anabolism. The breaking down 
 of material into simple products, or the changes in which 
 complex materials (including the living substance) are broken 
 down into comparatively simple products, is known as katabol- 
 ism. This reduction of complex substances to simple, results 
 in the production of animal force and energy. Thus a complex 
 substance, like a piece of beef-steak, is built up of a large 
 number of molecules which required the expenditure of force 
 or energy to store up. Now when this material is reduced by 
 the process of digestion to simpler bodies with fewer molecules, 
 such as carbon dioxid, urea, and water, the force stored up in 
 the meat as potential energy becomes manifest and is used as 
 active life-force known as kinetic energy. 
 
 16. Epithelium. Cells are associated and combined in 
 many ways to form a simple tissue. Such a simple tissue is 
 called an epithelium or surface-limiting tissue, and the cells 
 
 1 " Our material frame is composed of innumerable atoms, and each separate and 
 individual atom has its birth, life, and death, and then its removal from the ' place 
 of the living.' Thus there is going on a continuous process of decay and death 
 among the individual atoms which make up each tissue. Each tissue preserves its 
 vitality for a limited space only, is then separated from the tissue of which it has 
 formed a part, and is resolved into its inorganic elements, to be in due course elimi- 
 nated from the body by the organs of excretion." MACLAREN'S Physical Education. 
 
14 PRACTICAL PHYSIOLOGY. 
 
 are known as epithelial cells. These are united by a very 
 small amount of a cement substance which belongs to the pro- 
 teid class of material. The epithelial cells, from their shape, 
 are known as squamous, columnar, glandular, or ciliated. Again, 
 the cells may be arranged in only a single layer, or they may 
 be several layers deep. In the former case the epithelium is 
 said to be simple ; in the latter, stratified, No blood-vessels 
 pass into these tissues ; the cells derive their nourishment by the 
 
 imbibition of the plasma of the blood 
 exuded into the subjacent tissue. 
 
 17. Varieties of Epithelium. 
 The squamous or pavement epithe- 
 lium consists of very thin, flattened 
 scales, usually with a small nucleus 
 FIG. 4. Nerve Cells from the in the center. When the nucleus 
 GrayMatteroftheCerebellum. hag disappeared they become mere 
 (Magnified 260 diameters.) . J 
 
 horny plates, easily detached. Such 
 
 cells will be described as forming the outer layer of the skin, 
 the lining of the mouth and the lower part of the nostrils. 
 
 The columnar epithelium consists of pear-shaped or elon- 
 gated cells, frequently as a single layer of cells on the surface 
 of a mucous membrane, as on the lining of the stomach and 
 intestines, and the free surface of the windpipe and large air- 
 tubes. 
 
 The glandular or spheroidal epithelium is composed of 
 round cells or such as become angular by mutual pressure. 
 This kind forms the lining of glands such as the liver, pan- 
 creas, and the glands of the skin. 
 
 The ciliated epithelium is marked by the presence of very 
 fine hair-like processes called cilia, which develop from the free 
 end of the cell and exhibit a rapid whip-like movement as long 
 as the cell is alive. This motion is always in the same direc- 
 tion, and serves to carry away mucus and even foreign particles 
 
INTRODUCTION. 
 
 in contact with the membrane on which the cells are placed. 
 This epithelium is especially common in the air passages, where 
 it serves to keep a free passage for the entrance and exit of 
 air. In other canals a similar office is filled by this kind of 
 epithelium. 
 
 1 8. Functions of Epithelial Tissues. The epithelial struc- 
 tures may be divided, as to their functions, into two main divi- 
 sions. One is chiefly protective 
 in character. Thus the layers 
 of epithelium which form the 
 superficial layer of the skin have 
 little beyond such an office to 
 discharge. The same is to a 
 certain extent true of the epi- 
 thelial cells covering the mucous 
 membrane of the mouth, and 
 those lining the air passages 
 and air cells of the lungs. 
 
 The second great division of 
 the epithelial tissues consists 
 of those whose cells are formed 
 
 FIG. 5. Various Kinds of Epithelial 
 Cells. 
 
 r t . i , . , ,A, columnar cells of intestine ; B, poly- 
 
 Of highly active protoplasm, and he dral cells of the conjunctiva; C, cili- 
 
 ated conical cells of the trachea ; 0, 
 ciliated cell of frog's mouth ; E, inverted 
 conical cell of trachea ; F, squamous cell 
 of the cavity of mouth, seen from its broad 
 surface ; G, squamous cell, seen edgeways. 
 
 are busily engaged in some sort 
 
 of secretion. Such are the cells 
 
 of glands, the cells of the 
 
 salivary glands, which secrete 
 
 the saliva, of the gastric glands, which secrete the gastric 
 
 juice, of the intestinal glands, and the cells of the liver and 
 
 sweat glands. 
 
 19. Connective Tissue. This is the material, made up of 
 fibers and cells, which serves to unite and bind together the 
 different organs and tissues. It forms a sort of flexible frame- 
 work of the body, and so pervades every portion that if all the 
 
1 6 PRACTICAL PHYSIOLOGY. 
 
 other tissues were removed, we should still have a complete 
 representation of the bodily shape in every part. In general, 
 the connective tissues proper act as packing, binding, and sup- 
 porting structures. This name includes certain tissues which 
 to all outward appearance vary greatly, but which are properly 
 grouped together for the following reasons : first, they all 
 act as supporting structures ; second, under certain conditions 
 one may be substituted for another ; third, in some places 
 they merge into each other. 
 
 All these tissues consist of a ground-substance, or matrix, 
 cells, and fibers. The ground-substance is in small amount in 
 connective tissues proper, and is obscured by a mass of fibers. 
 It is best seen in hyaline cartilage, where it has a glossy 
 appearance. In bone it is infiltrated with salts which give 
 bone its hardness, and make it seem so unlike other tissues. 
 The cells are called connective-tissue corpuscles, cartilage cells, 
 and bone corpuscles, according to the tissues in which they 
 occur. The fibers are the white fibrous and the yellow elastic 
 tissues. 
 
 The following varieties are usually described : 
 
 1 . White Fibrous Tissue. 
 
 2. Yellow Elastic Tissue. 
 
 I. Connective Tissues Areolar or Cellular Tissue. 
 
 Proper : 
 
 4- Adipose or Fatty Tissue. 
 5. Adenoid or Retiform Tissue. 
 
 {i . Hyaline. 
 2. White Fibro-cartilage. 
 3. Yellow Fibro-cartilage. 
 
 III. Bone and Dentine of Teeth. 
 
 20. White Fibrous Tissue. This tissue consists of bundles 
 of very delicate fibrils bound together by a small amount of 
 cement substance. Between the fibrils protoplasmic masses 
 
INTRODUCTION. 
 
 (connective-tissue corpuscles) are found. These fibers may b6 
 found so interwoven as to form a sheet, as in the periosteum 
 of the bone, the fasciae around muscles, and the capsules of 
 organs; or they may be aggregated into bundles and form rope- 
 like bands, as in the ligaments 
 of joints and the tendons of 
 muscles. On boiling, this tis- 
 sue yields gelatine. In general, 
 where white fibrous tissue 
 abounds, structures are held to- 
 gether, and there is flexibility, 
 but little or no distensibility. 
 
 FIG. 6. White Fibrous Tissue. 
 
 21. YellOW Elastic Tissue. (Highly magnified.) 
 
 The fibers of yellow elastic 
 
 tissue are much stronger and coarser than those of the white. 
 
 They are yellowish, tend to curl up at the ends, and are highly 
 
 elastic. It is these fibers which give elasticity to the skin and 
 
 to the coats of the arteries. The 
 typical form of this tissue occurs in 
 the ligaments which bind the verte- 
 brae together (Fig. 26), in the true 
 vocal cords, and in certain ligaments 
 of the larynx. In the skin and fasciae, 
 the yellow elastic is found mixed 
 with white fibrous and areolar tis- 
 
 FIG. 7 .- Yellow Elastic Tissue. sues - It: does not Y ield gelatine on 
 (Highly magnified.) boiling, and the cells are, if any, few. 
 
 22. Areolar or Cellular Tissue. This consists of bundles 
 of delicate fibers interlacing and crossing one another, forming 
 irregular spaces or meshes. These little spaces, in health, are 
 filled with fluid that has oozed out of the blood-vessels. The 
 areolar tissue forms a protective covering for the tissues of 
 delicate and important organs. 
 
1 8 PRACTICAL PHYSIOLOGY. 
 
 23. Adipose or Fatty Tissue. In almost every part of the 
 body the ordinary areolar tissue contains a variable quantity of 
 adipose or fatty tissue. Examined by the microscope, the fat 
 cells consist of a number of minute sacs of exceedingly delicate, 
 structureless membrane filled with oil. This is liquid in life, 
 but becomes solidified after death. This tissue is plentiful be- 
 neath the skin, in the abdominal cavity, on the surface of the 
 heart, around the kidneys, in the marrow 
 p-f^ i of bones, and elsewhere. Fat serves as 
 a soft packing material. Being a poor 
 conductor, it retains the heat, and fur- 
 nishes a store rich in carbon and hydro- 
 gen for use in the body. 
 
 24. Adenoid or Retiform Tissue. 
 This is a variety of connective tissue 
 found in the tonsils, spleen, lymphatic 
 FIG. 8. Fibro-Cartiiage Fi- glands, and allied structures. It con- 
 
 bers. (Showing network sur- sists Q f a yery fine network of fibrils 
 rounding cartilage cells.) . . . . J , . . 
 
 around which are cells of various sizes. 
 
 The tissue combining them is known as adenoid or gland-like 
 tissue. 
 
 25. Cartilage. Cartilage, or gristle, is a tough but highly 
 elastic substance. Under the microscope cartilage is seen to 
 consist of a matrix, or base, in which nucleated cells abound, 
 either singly or in groups. It has sometimes a fine ground- 
 glass appearance, when the cartilage is spoken of as hyaline. 
 In other cases the matrix is almost replaced by white fibrous 
 tissue. This is called white fibro-cartilage, and is found 
 where great strength and a certain amount of rigidity are 
 required. 
 
 Again, there is between the cells a meshwork of yellow 
 elastic fibers, and this is called yellow fibro-cartilage (Fig. 8). 
 The hyaline cartilage forms the early state of most of the 
 
INTRODUCTION. 
 
 bones, and is also a permanent coating 
 for the articular ends of long bones. 
 The white fibro-cartilage is found in A 
 the disks between the bodies of the ver- B 
 tebrae, in the interior of the knee joint, c 
 in the wrist and other joints, filling the 
 cavities of the bones, in socket joints, 
 and in the grooves for tendons. The 
 yellow fibro-cartilage forms the ex- 
 panded part of the ear, the epiglottis, 
 and other parts of the larynx. 
 
 26. General Plan of the Body. To 
 get a clearer idea of the general plan 
 on which the body is constructed, let 
 us imagine its division into perfectly 
 equal parts, one the right and the other 
 the left, by a great knife severing it 
 through the median, or middle line in 
 front, backward through the spinal 
 column, as a butcher divides an ox or 
 a sheep into halves for the market. In 
 a section of the body thus planned the 
 skull and the spine together are shown 
 to have formed a tube, containing the 
 brain and spinal cord. The other parts 
 of the body form a second tube (ven- 
 tral) in front of the spinal or dorsal 
 tube. The upper part of the second 
 tube begins with the mouth and is 
 formed by the ribs and breastbone. 
 Below the chest in the abdomen, the 
 walls of this tube would be made up 
 of the soft parts. 
 
 D .. V- 
 
 FIG. 9. Diagrammatic Lon- 
 gitudinal Section of the 
 Trunk and Head. (Show- 
 ing the dorsal and the ven- 
 tral tubes.) 
 
 A, the cranial cavity; B, the 
 cavity of the nose; C, the 
 mouth ; D, the alimentary 
 canal represented as a simple 
 straight tube ; E, the sympa- 
 thetic nervous system ; F, 
 heart; G, diaphragm; H, 
 stomach ; K, end of spinal 
 portion of cerebro-spinal ner- 
 vous system. 
 
2O PRACTICAL PHYSIOLOGY. 
 
 We may say, then, that the body consists of two tubes or 
 cavities, separated by a bony wall, the dorsal or nervous tube, 
 so called because it contains the central parts of the nervous 
 system ; and the visceral or ventral tube, as it contains the 
 viscera, or general organs of the body, as the alimentary canal, 
 the heart, the lungs, the sympathetic nervous system, and other 
 organs. 
 
 The more detailed study of the body may now be begun by 
 a description of the skeleton or framework which supports the 
 soft parts. 
 
 EXPERIMENTS. 
 
 For general directions and explanations and also detailed 
 suggestions for performing experiments, see Chapter XV. 
 
 Experiment i. To examine squamous epithelium. With an ivory 
 paper-knife scrape the back of the tongue or the inside of the lips or cheek ; 
 place the substance thus obtained upon a glass slide ; cover it with a thin 
 cover-glass, and if necessary add a drop of water. Examine with the 
 microscope, and the irregularly formed epithelial cells will be seen. 
 
 Experiment 2. To examine ciliated epithelium. Open a frog's mouth, 
 and with the back of a knife blade gently scrape a little of the membrane 
 from the roof of the mouth. Transfer to a glass slide, add a drop of salt 
 solution, and place over it a cover-glass with a hair underneath to prevent 
 pressure upon the cells. Examine with a microscope under a high power. 
 The cilia move very rapidly when quite fresh, and are therefore not easily 
 seen. 
 
 For additional experiments which pertain to the microscopic 
 examination of the elementary tissues and to other points in 
 practical histology, see Chapter XV. 
 
 NOTE. Inasmuch as most of the experimental work of this chapter depends 
 upon the use of the microscope and also necessarily assumes a knowledge of facts 
 which are discussed later, it would be well to postpone experiments in histology until 
 they can be more satisfactorily handled in connection with kindred topics as they are 
 met with in the succeeding chapters. 
 
CHAPTER II. 
 THE BONES. 
 
 27. The Skeleton. Most animals have some kind of frame- 
 work to support and protect the soft and fleshy parts of their 
 bodies. This framework consists chiefly of a large number of 
 bones, and is called the skeleton. It is like the keel and ribs 
 of a vessel or the frame of a house, the foundation upon which 
 the bodies are securely built. 
 
 There are in the adult human body 200 distinct bones, of many 
 sizes and shapes. This number does not, however, include 
 several small bones found in the tendons of muscles and in the 
 ear. The teeth 'are not usually reckoned as separate bones, 
 being a part of the structure of the skin. 
 
 The number of distinct bones varies at different periods of 
 life. It is greater in childhood than in adults, for many bones 
 which are then separate, to allow growth, afterwards become 
 gradually united. In early adult life, for instance, the skull 
 contains 22 naturally separate bones, but in infancy the number 
 is much greater, and in old age far less. 
 
 The bones of the body thus arranged give firmness, strength, 
 and protection to the soft tissues and vital organs, and also 
 form levers for the muscles to act upon. 
 
 28. Chemical Composition of Bone. The bones, thus form- 
 ing the framework of the body, are hard, tough, and elastic. 
 They are twice as strong as oak ; one cubic inch of compact 
 bone will support a weight of 5000 pounds. Bone is composed 
 of earthy or mineral matter (chiefly in the form of lime salts), 
 and of animal matter (principally gelatine), in the proportion 
 of two-thirds of the former to one-third of the latter. 
 
22 
 
 PRACTICAL PHYSIOLOGY. 
 
 FIG. io. The Skeleton. 
 
THE BONES. 
 
 The proportion of earthy to animal matter varies with age. 
 In infancy the bones are composed almost wholly of animal 
 matter. Hence, an infant's bones are rarely broken, but its 
 legs may soon become misshapen if walking is allowed too 
 early. In childhood, the bones still contain a larger percentage 
 of animal matter than in more advanced life, and are therefore 
 more liable to bend than to break ; while in old age, they con- 
 tain a greater percentage of mineral matter, and are brittle and 
 easily broken. 
 
 Experiment 3. To show the mineral matter in bone. Weigh a large 
 soup bone ; put it on a hot, clear fire until it is at a red heat. At first it 
 becomes black from the carbon of its organic matter, but at 
 last it turns white. Let it cool and weigh again. The animal 
 matter has been burnt out, leaving the mineral or earthy 
 part, a white, brittle substance of exactly the same shape, but 
 weighing only about two-thirds as much as the bone originally 
 weighed. 
 
 Experiment 4. To show the animal matter in bone. Add 
 a teaspoonful of muriatic acid to a pint of water, and place the 
 mixture in a shallow earthen dish. Scrape and clean a 
 chicken's leg bone, part of a sheep's rib, or any other small, 
 thin bone. Soak the bone in the acid mixture for a few days. 
 The earthy or mineral matter is slowly dissolved, and the 
 bone, although retaining its original form, loses its rigidity, 
 and becomes pliable, and so soft as to be readily cut. If the 
 experiment be carefully performed, a long, thin bone may even 
 be tied into a knot. 
 
 29. Physical Properties of Bone. If we take a leg 
 bone of a sheep, or a large end of beef shin bone, and 
 saw it lengthwise in halves, we see two distinct structures. 
 There is a hard and compact tissue, like ivory, forming the 
 outside shell, and a spongy tissue inside having the appearance 
 of a beautiful lattice work. Hence this is called cancellous 
 tissue, and the gradual transition from one to the other is 
 apparent. 
 
24 PRACTICAL PHYSIOLOGY. 
 
 It will also be seen that the shaft is a hollow 
 cylinder, formed of compact tissue, enclosing 
 a cavity called the medullary canal, which is 
 filled with a pulpy, yellow fat called marrow. 
 The marrow is richly supplied with blood- 
 vessels, which enter the cavity through small 
 openings in the compact tissue. In fact, all 
 over the surface of bone are minute canals 
 leading into the substance. One of these, 
 especially constant and large in many bones, 
 is called the nutrient foramen, and transmits 
 an artery to nourish the bone. 
 
 At the ends of a long bone, where it ex- 
 pands, there is no medullary canal, and the 
 bony tissue is spongy, with only a thin layer 
 of dense bone around it. In flat bones we 
 find two layers or plates of compact tissue at 
 the surface, and a spongy tissue between. 
 Short and irregular bones have no medullary 
 canal, only a thin shell of dense bone filled 
 with cancellous tissue. 
 
 h ' h Experiment 5. Obtain a part of a beef shin bone, 
 
 ' ' ,. or a portion of a sheep's or calf's leg, including if con- 
 
 lenethwise (Show- ven i ent tne knee joint. Have the bone sawed in two, 
 
 ing arrangement of lengthwise, keeping the marrow in place. Boil, scrape, 
 
 compact and can- an d carefully clean one half. Note the compact and 
 
 cellous tissue.) spongy parts, shaft, etc. 
 
 Experiment 6. Trim off the flesh from the second half. Note the 
 pinkish white appearance of the bone, the marrow, and the tiny specks of 
 blood, etc. Knead a small piece of the marrow in the palm ; note the 
 oily appearance. Convert some marrow into a liquid by heating. Con- 
 trast this fresh bone with an old dry one, as found in the fields. Fresh 
 bones should be kept in a cool place, carefully wrapped in a damp cloth, 
 while waiting for class use. 
 
THE BONES. 25 
 
 A fresh or living bone is covered with a delicate, tough, 
 fibrous membrane, called the periosteum. It adheres very 
 closely to the bone, and covers every part except at the joints 
 and where it is protected with cartilage. The periosteum is 
 richly supplied with blood-vessels, and plays a chief part in the 
 growth, formation, and repair of bone. If a portion of the 
 periosteum be detached by injury or disease, there is risk that 
 a layer of the subjacent bone will lose its vitality and be 
 cast off. 1 
 
 30. Microscopic Structure of Bone. If a very thin slice of 
 bone be cut from the compact tissue and examined under 
 a microscope, numerous minute openings are seen. Around 
 these are arranged rings of bone, with little black bodies in 
 them, from which radiate fine, dark lines. These openings are 
 sections of canals called Haversian canals, after Havers, an 
 English physician, who first discovered them. The black bodies 
 are minute cavities called lacuntz, while the fine lines are very 
 minute canals, canaliculi, which connect the lacunae and the 
 Haversian canals. These Haversian canals are supplied with 
 tiny blood-vessels, while the lacunae contain bone cells. Very 
 fine branches from these cells pass into the canaliculi. The 
 Haversian canals run lengthwise of the bone ; hence if the 
 bone be divided longitudinally these canals will be opened 
 along their length (Fig. 13). 
 
 Thus bones are not dry, lifeless substances, but are the 
 very type of activity and change. In life they are richly sup- 
 
 1 The periosteum is often of great practical importance to the surgeon. Instances 
 are on record where bones have been removed, leaving the periosteum, within which 
 the entire bone has grown again. The importance of this remarkable tissue is still 
 farther illustrated by experiments upon the transplantation of this membrane in the 
 different tissues of living animals, which has been followed by the formation of bone 
 in these situations. Some years ago a famous surgeon in New York removed the 
 whole lower jawbone from a young woman, leaving the periosteum and even retaining 
 in position the teeth by a special apparatus. The entire jawbone grew again, and 
 the teeth resumed their original places as it grew. 
 
26 
 
 PRACTICAL PHYSIOLOGY. 
 
 plied with blood from the nutrient artery and from the peri- 
 osteum, by an endless network of nourishing canals throughout 
 their whole structure. Bone has, therefore, like all other living 
 structures, a self -formative power, and draws from the blood 
 the materials for its own nutrition. 
 
 FIG. 13. 
 
 A, longitudinal section of bone, by which the Haversian canals are seen branching 
 and communicating with one another ; B, cross section of a very thin slice of 
 bone, magnified about 300 diameters little openings (Haversian canals) are 
 seen, and around them are ranged rings of bones with little black bodies (lacunas), 
 from which branch out fine dark lines (canaliculi) ; C, a bone cell, highly magni- 
 fied, lying in lacuna. 
 
 THE BONES OF THE HEAD. 
 
 31. The Head, or Skull. The bones of the skeleton, the 
 bony framework of our bodies, may be divided into those of 
 the head, the trunk, and the limbs. 
 
 The bones of the head are described in two parts, those 
 of the cranium, or brain-case, and those of the face. Taken 
 together, they form the skull. The head is usually said to con- 
 tain 22 bones, of which 8 belong to the cranium and 14 to the 
 face. In early childhood, the bones of the head are separate 
 to allow the brain to expand ; but as we grow older they gradu- 
 ally unite, the better to protect the delicate brain tissue. 
 
THE BONES. 2/ 
 
 32. The Cranium. The cranium is a dome-like structure, 
 made up in the adult of 8 distinct bones firmly locked together. 
 These bones are : 
 
 One Frontal, One Occipital, 
 
 Two Parietal, One Sphenoid, 
 
 Two Temporal, One Ethmoid. 
 
 The frontal bone forms the forehead and front of the head. 
 It is united with the two parietal bones behind, and extends 
 over the forehead to make the roofs of the sockets of the eyes. 
 It is this bone which, in many races of man, gives a dignity of 
 person and a beauty of form seen in no other animal. 
 
 The parietal bones form the sides and roof of the skull. 
 They are bounded anteriorly by the frontal bone, posteriorly 
 by the occipital, and laterally by the temporal and sphenoid 
 bones. The two bones make a beautiful arch to aid in the 
 protection of the brain. 
 
 The temporal bones, forming the temples on either side, 
 are attached to the sphenoid bone in front, the parietals above, 
 and the occipital behind. In each temporal bone is the cavity 
 containing the organs of hearing. These bones are so called 
 because the hair usually first turns gray over them. 
 
 The occipital bone forms the lower part of the base of the 
 skull, as well as the back of the head. It is a broad, curved 
 bone, and rests on the topmost vertebra (atlas) of the back- 
 bone ; its lower part is pierced by a large oval opening called 
 the foramen magnum, through which the spinal cord passes 
 from the brain (Fig. 15). 
 
 The sphenoid bone is in front of the occipital, forming a 
 part of the base of the skull. It is wedged between the bones 
 of the face and those of the cranium, and locks together four- 
 teen different bones. It bears a remarkable resemblance to a 
 bat with extended wings, and forms a series of girders to the 
 arches of the cranium. 
 
28 
 
 PRACTICAL PHYSIOLOGY. 
 
 The ethmoid bone is situated between the bones of the 
 cranium and those of the face, just at the root of the nose. 
 It forms a part of the floor of the cranium. It is a delicate, 
 spongy bone, and is so called because it is perforated with 
 
 FIG. 14. The Skull. 
 
 numerous holes like a sieve, through which the nerves of smell 
 pass from the brain to the nose. 
 
 33. The Face. The bones of the face serve, to a marked 
 extent, in giving form and expression to the human counte- 
 nance. Upon these bones depend, in a measure, the build of 
 the forehead, the shape of the chin, the size of the eyes, the 
 
THE BONES. 2Q 
 
 prominence of the cheeks, the contour of the nose, and other 
 marks which are reflected in the beauty or ugliness of the face. 
 
 The face is made up of fourteen bones which, with the 
 exception of the lower jaw, are, like those of the cranium, 
 closely interlocked with each other. By this union these bones 
 help form a number of cavities which contain most important 
 and vital organs. The two deep, cup-like sockets, called the 
 orbits, contain the organs of sight. In the cavities of the nose 
 is located the sense of smell, while the buccal cavity, or mouth, 
 is the site of the sense of taste, and plays besides an important 
 part in the first act of digestion and in the function of speech. 
 
 The bones of the face are : 
 
 Two Superior Maxillary, Two Palate, 
 
 Two Malar, Two Turbinated, 
 
 Two Nasal, One Vomer, 
 
 Two Lachrymal, One Lower Maxillary. 
 
 34. Bones of the Face. The superior maxillary or upper 
 jawbones form a part of the roof of the mouth and the entire 
 floor of the orbits. In them is fixed the upper set of teeth. 
 
 The malar or cheek bones are joined to the upper jaw- 
 bones, and help form the sockets of the eyes. They send an 
 arch backwards to join the temporal bones. These bones are 
 remarkably thick and strong, and are specially adapted to 
 resist the injury to which this part of the face is exposed. 
 
 The nasal or nose bones are two very small bones between 
 the eye sockets, which form the bridge of the nose. Very near 
 these bones are the two small lachrymal bones. These are 
 placed in the inner angles of the orbit, and in them are grooves 
 in which lie the ducts through which the tears flow from the 
 eyes to the nose. 
 
 The palate bones are behind those of the upper jaw and with 
 them form the bony part of the roof of the mouth. The in- 
 ferior turbinated are spongy, scroll-like bones, which curve 
 
3O PRACTICAL PHYSIOLOGY. 
 
 about within the nasal cavities so as to increase the surface of 
 
 the air passages of the nose. 
 
 The vomer serves as a thin and delicate partition between 
 
 the two cavities of the nose. 
 It is so named from its resem- 
 blance to a ploughshare. 
 
 The longest bone in the face 
 is the inferior maxillary, or 
 lower jaw. It has a horseshoe 
 shape, and supports the lower 
 set of teeth. It is the only 
 movable bone of the head, hav- 
 ing a vertical and lateral motion 
 by means of a hinge joint with 
 a part of the temporal bone. 
 
 35. Sutures of the Skull. Be- 
 fore leaving the head we must 
 notice the peculiar and admirable 
 
 manner in which the edges of the 
 FIG. 15. The Base of the Skull. . , . 
 
 bones of the outer shell of the 
 
 A, palate process of upper jawbone. B, zy- . . . 
 
 goma, forming zygomatic arch. C,condyle sku11 are J Omed together. These 
 
 for forming articulation with atlas. D, fo- edges of the bones* resemble the 
 
 ramen magnum. E, occipital bone. ^th of a saw. In adult life these 
 
 tooth-like edges fit into each other and grow together, suggesting the 
 dovetailed joints used by the cabinet-maker. When united these 
 serrated edges look almost as if sewed together ; hence their name, 
 sutures. This manner of union gives unity and strength to the skull. 
 In infants, the corners of the parietal bones do not yet meet, and 
 the throbbing of the brain may be seen and felt under these " soft 
 spots," or fontanelles, as they are called. Hence a slight blow to a 
 babe's head may cause serious injury to the brain (Fig. 14). 
 
 THE BONES OF THE TRUNK. 
 
 36. The Trunk. The trunk is that central part of the body 
 which supports the head and the upper pair of limbs. It 
 
THE BONES. 31 
 
 divides itself into an upper cavity, the thorax, or chest ; and 
 a lower cavity, the abdomen. These two cavities are separated 
 by a movable, muscular partition called the diaphragm, or 
 midriff (Figs. 9 and 49). 
 
 The bones of the trunk are variously related to each other, 
 and some of them become united during adult life into bony 
 masses which at earlier periods are quite distinct. For ex- 
 ample, the sacrum is in early life made up of five distinct 
 bones which later unite into one. 
 
 The upper cavity, or chest, is a bony enclosure formed by the 
 breastbone, the ribs, and the spine. It contains the heart and 
 the lungs (Fig. 86). 
 
 The lower cavity, or abdomen, holds the stomach, liver, 
 intestines, spleen, kidneys, and some other organs (Fig. 59). 
 
 The bones of the trunk may be subdivided into those of the 
 spine, the ribs, and the hips. 
 
 The trunk includes 54 bones usually thus arranged : 
 
 I. Spinal Column, 26 bones: 
 
 7 Cervical Vertebrae. 
 12 Dorsal Vertebras. 
 5 Lumbar Vertebrae. 
 
 i Sacrum, 
 i Coccyx. 
 
 {14 True Ribs. 
 6 False Ribs. 
 4 Floating Ribs. 
 
 III. Sternum. 
 
 IV. Two Hip Bones. 
 V. Hyoid Bone. 
 
 37. The Spinal Column. The spinal column, or back- 
 bone, is a marvelous piece of mechanism, combining offices 
 which nothing short of perfection in adaptation and arrange- 
 ment could enable it to perform. It is the central structure to 
 which all the other parts of the skeleton are adapted. It con- 
 
PRACTICAL PHYSIOLOGY. 
 
 sists of numerous separate bones, called vertebrae. The seven 
 upper ones belong to the neck, and 
 are called cervical vertebrae. The 
 next twelve are the dorsal vertebrae ; 
 these belong to the back and support 
 the ribs. The remaining five belong 
 to the loins, and are called lumbar 
 vertebrae. On looking at the diagram 
 of the backbone (Fig. 9) it will be seen 
 that the vertebrae increase in size and 
 strength downward, because of the 
 greater burden they have to bear, thus 
 clearly indicating that an erect posi- 
 tion is the one natural to man. 
 
 This column supports the head, en- 
 closes and protects the spinal cord, 
 and forms the basis for the attachment 
 of many muscles, especially those 
 which maintain the body in an erect 
 position. Each vertebra has an open- 
 ing through its center, and the separ- 
 ate bones so rest, one upon another, 
 that these openings form a continuous 
 canal from the head to the lower part 
 of the spine. The great nerve, known 
 as the spinal cord, extends from the 
 cranium through the entire length of 
 this canal. All along the spinal col- 
 umn, and between each two adjoining 
 bones, are openings on each side, 
 through which nerves pass out to be 
 distributed to various parts of the body. 
 Between the vertebrae are pads or 
 cushions of cartilage. These act as 
 
 COCCYX 
 
 FIG 16. The Spinal 
 Column. 
 
THE BONES. 33 
 
 " buffers," and serve to give the spine strength and elasticity 
 and to prevent friction of one bone on another. Each vertebra 
 consists of a body, the solid central portion, and a number of 
 projections called processes. Those which spring from the 
 posterior of each arch are the spinous processes. In the dorsal 
 region they are plainly seen and felt in thin persons. 
 
 The bones of the spinal column are arranged in three slight 
 and graceful curves. These curves not only give beauty and 
 strength to the bony framework of the body, but also assist in 
 the formation of cavities for important internal organs. This 
 arrangement of elastic pads between the vertebrae supplies 
 the spine with so many elastic springs, which serve to break 
 the effect of shock to the brain and the spinal cord from any 
 sudden jar or injury. 
 
 The spinal column rests on a strong three-sided bone called 
 the sacrum, or sacred-bone, which is wedged in between the 
 hip bones and forms the keystone of the pelvis. Joined to the 
 lower end of the sacrum is the coccyx, or cuckoo-bone, a taper- 
 ing series of little bones. 
 
 Experiment 7. Run the tips of the fingers briskly down the backbone, 
 and the spines of the vertebrae will be tipped with red so that they can be 
 readily counted. Have the model lean forward with the arms folded 
 across the chest ; this will make the spines of the vertebrae more 
 prominent. 
 
 Experiment 8. To illustrate the movement of torsion in the spine, or its 
 rotation round its own axis. Sit upright, with the back and shoulders well 
 applied against the back of a chair. Note that the head and neck can be 
 turned as far as 60 or 70. Now bend forwards, so as to let the dorsal 
 and lumbar vertebras come into play, and the head can be turned 30 more. 
 
 Experiment 9. To show how the spinal vertebra make a firm but flexi- 
 ble column. Take 24 hard rubber overcoat buttons, or the same number 
 of two-cent pieces, and pile them on top of each other. A thin layer of 
 soft putty may be put between the coins to represent the pads of cartilage 
 between the vertebrae. The most striking features of the spinal column 
 may be illustrated by this simple apparatus. 
 
34 PRACTICAL PHYSIOLOGY. 
 
 38. How the Head and Spine are Joined together. The head 
 rests upon the spinal column in a manner worthy of special notice. 
 This consists in the peculiar structure of the first two cervical verte- 
 brae, known as the axis and atlas. The atlas is named after the 
 fabled giant who supported the earth on his shoulders. This verte- 
 bra consists of a ring of bone, having two cup-like sockets into which 
 fit two bony projections arising on either side of the great opening 
 (foramen magnum) in the occipital bone. The hinge joint thus 
 formed allows the head to nod forward, while ligaments prevent it 
 from moving too far. 
 
 On the upper surface of the axis, the second vertebra, is a peg or 
 process, called the odontoid process from its resemblance to a tooth. 
 This peg forms a pivot upon which the head with the atlas turns. It 
 is held in its place against the front inner surface of the atlas by a 
 band of strong ligaments, which also prevents it from pressing on the 
 delicate spinal cord. Thus, when we turn the head to the right 
 or left, the skull and the atlas move together, both rotating on the 
 odontoid process of the axis. 
 
 39. The Ribs and Sternum. The barrel-shaped framework 
 of the chest is in part composed of long, slender, curved bones 
 called ribs. There are twelve ribs on each side, which enclose 
 and strengthen the chest ; they somewhat resemble the hoops 
 of a barrel. They are connected in pairs with the dorsal verte- 
 brae behind. 
 
 The first seven pairs, counting from the neck, are called the 
 true ribs, and are joined by their own special cartilages directly to 
 the breastbone. The five lower pairs, called \hzfalse ribs, are 
 not directly joined to the breastbone, but are connected, with 
 the exception of the last two, with each other and with the 
 last true ribs by cartilages. These elastic cartilages enable 
 the chest to bear great blows with impunity. A blow on the 
 sternum is distributed over fourteen elastic arches. The 
 lowest two pairs of false ribs, are not joined even by cartilages, 
 but are quite free in front, and for this reason are called float- 
 ing ribs. 
 
THE BONES. 
 
 35 
 
 The ribs are not horizontal, but slope downwards from the 
 backbone, so that when raised or depressed by the strong inter- 
 costal muscles, the size of the chest is alternately increased or 
 diminished. This movement of the ribs is of the utmost 
 importance in breathing (Fig. 91). 
 
 The sternum, or breastbone, is a long, flat, narrow bone 
 forming the middle front wall of the chest. It is connected 
 with the ribs and with the 
 collar bones. In shape it 
 somewhat resembles an 
 ancient dagger. 
 
 40. The Hip Bones. 
 
 Four immovable bones are 
 joined together so as to 
 form at the lower ex- 
 tremity of the trunk a 
 basin-like cavity called the 
 pelvis. These four bones 
 are the sacrum and the 
 coccyx, which have been 
 described, and the two hip 
 bones. 
 
 The hip bones are large, 
 irregularly shaped bones, 
 
 very firm and strong, and are sometimes called the haunch 
 bones or ossa innominata (nameless bones). They are united 
 to the sacrum behind and joined to each other in front. On 
 the outer side of each hip bone is a deep cup, or socket, 
 called the acetabulum, resembling an ancient vinegar cup, into 
 which fits the rounded head of the thigh bone. The bones of 
 the pelvis are supported like a bridge on the legs as pillars, 
 and they in turn contain the internal organs in the lower part 
 of the trunk. 
 
 FIG. 17. Thorax. (Anterior view.) 
 
36 PRACTICAL PHYSIOLOGY. 
 
 41. The Hyoid Bone. Under the lower jaw is a little horseshoe- 
 shaped bone called the hyoid bone, because it is shaped like the Greek 
 letter upsilon (T). The root of the tongue is fastened to its bend, 
 and the larynx is hung from it as from a hook. When the neck is in 
 its natural position this bone can be plainly felt on a level with the 
 lower jaw and about one inch and a half behind it. It serves to 
 keep open the top of the larynx and for the attachment of the muscles 
 which move the tongue. (See Fig. 46.) The hyoid bone, like the 
 knee-pan, is not connected with any other bone. 
 
 THE BONES OF THE UPPER LIMBS. 
 
 42. The Upper Limbs. Each of the upper limbs consists 
 of the upper arm, the forearm, and the hand. These bones 
 are classified as follows : 
 
 f Scapula, or shoulder-blade, 
 Upper Arm : -^ Clavicle, or collar bone, 
 ^ Humerus, or arm bone, 
 
 Forearm:/ 111118 ' 
 ^ Radius, 
 
 {& Carpal or wrist bones, 
 5 Metacarpal bones, 
 14 Phalanges, or finger bones, 
 
 making 32 bones in all. 
 
 43. The Upper Arm. The two bones of the shoulder, the 
 scapula and the clavicle, serve in man to attach the arm to the 
 trunk. The scapula, or shoulder-blade, is a flat, triangular 
 bone, placed point downwards, and lying on the upper and 
 back part of the chest, over the ribs. It consists of a broad, 
 flat portion and a prominent ridge or spine. At its outer angle 
 it has a shallow cup known as the glenoid cavity. Into this 
 socket fits the rounded head of the humerus. The shoulder- 
 blade is attached to the trunk chiefly by muscles, and is capable 
 of extensive motion. 
 
THE BONES. 
 
 37 
 
 The clavicle, or collar bone, is a slender bone with a double 
 curve like an italic f, and extends from the outer angle of the 
 shoulder-blade to the top of the breastbone. It thus serves like 
 
 >'(> 
 
 the 
 key- 
 stone 
 of an 
 arch to 
 hold the shoul- 
 der-blade firmly 
 in its place, but its 
 chief use is to keep the 
 shoulders wide apart, that 
 the arm may enjoy a freer 
 range of motion. This bone 
 is often broken J)y falls upon 
 the shoulder or arm. 
 
 The humerus is the strong- 
 est bone of the upper extrem- 
 ity. As already mentioned, its 
 rounded head fits into the socket 
 of the shoulder-blade, forming a 
 ball-and-socket joint, which permits 
 great freedom of motion. The shoul- 
 der joint resembles what mechanics 
 call a universal joint, for there is no part of 
 the body which cannot be touched by the hand. 
 
 When the shoulder is dislocated the head 
 of the humerus has been forced out of its 
 socket. The lower end of the bone is grooved to help form a 
 hinge joint at the elbow with the bones of the forearm (Fig. 27). 
 
 FIG. 1 8. 
 
 Left Scapula, or 
 Shoulder-Blade. 
 
PRACTICAL PHYSIOLOGY. 
 
 44. The Forearm. The forearm contains two long bones, 
 the ulna and the radius. The ulna, so called because it forms 
 the elbow, is the longer and larger bone of the forearm, and is 
 on the same side as the little finger. It is 
 connected with the humerus by a hinge joint 
 at the elbow. It is prevented from moving 
 too far back by a hook-like projection called 
 the olecranon process, which makes the sharp 
 point of the elbow. 
 
 The radius is the shorter of the two bones 
 of the forearm, and is on the same side as the 
 thumb. Its slender, upper end articulates 
 with the ulna and humerus ; its lower end is 
 enlarged and gives attachment in part to the 
 bones of the wrist. This bone radiates or 
 turns on the ulna, carrying the hand with it. 
 
 Experiment 10. Rest the forearm on a table, with 
 the palm up (an attitude called supination). The 
 radius is on the outer side and parallel with the ulna. 
 If now, without moving the elbow, we turn the hand 
 (pronation), as if to pick up something from the table, 
 the radius may be seen and felt crossing over the ulna, 
 while the latter has not moved. 
 
 FIG. 19. Left Cla- 
 vicle, or Collar 
 Bone. (Anterior 
 surface.) 
 
 45. The Hand. The hand is the executive 
 or essential part of the upper limb. Without 
 it the arm would be almost useless. It con- 
 sists of 27 separate bones, and is divided into three parts, the 
 wrist, the palm, and the fingers. 
 
 The carpus, or wrist, includes 8 short bones, arranged in two 
 rows of four each, so as to form a broad support for the hand. 
 These bones are closely packed, and tightly bound with liga- 
 ments which admit of ample flexibility. Thus the wrist is much 
 less liable to be broken than if it were to consist of a single 
 bone, while the elasticity from having the eight bones movable 
 
THE BONES. 
 
 39 
 
 FIG. 20. Left Humerus. FIG. 21. Left Radius and Ulna. 
 
4O . PRACTICAL PHYSIOLOGY. 
 
 on each other, neutralizes, to a great extent, a shock caused by 
 falling on the hands. Although each of the wrist bones has a 
 very limited mobility in relation to its neighbors, their combi- 
 nation gives the hand that freedom of action upon the wrist, 
 which is manifest in countless examples of the most accurate 
 and delicate manipulation. 
 
 The metacarpal bones are the five long bones of the back 
 of the hand. They are attached to the wrist and to the finger 
 bones, and may be easily felt by pressing the fingers of one 
 hand over the back of the other. The metacarpal bones of 
 the fingers have little freedom of movement, while the thumb, 
 unlike the others, is freely movable. We are thus enabled to 
 bring the thumb in opposition to each of the fingers, a matter 
 of the highest importance in manipulation. For this reason 
 the loss of the thumb disables the hand far more than the 
 loss of either of the fingers. This very significant opposition 
 of the thumb to the fingers, furnishing the complete grasp by 
 the hand, is characteristic of the human race, and is wanting in 
 the hand of the ape, chimpanzee, and ourang-outang. 
 
 The phalanges, or finger bones, are the fourteen small bones 
 arranged in three rows to form the fingers. Each finger has 
 three bones ; each thumb, two. 
 
 The large number of bones in the hand not only affords 
 every variety of movement, but offers great resistance to blows 
 or shocks. These bones are united by strong but flexible liga- 
 ments. The hand is thus given strength and flexibility, and 
 enabled to accomplish the countless movements so necessary 
 to our well-being. 
 
 In brief, the hand is a marvel of precise and adapted mechan- 
 ism, capable not only of performing every variety of work and 
 of expressing many emotions of the mind, but of executing its 
 orders with inconceivable rapidity. 
 
THE BONES. 
 
 THE BONES OF THE LOWER LIMBS. 
 
 46. The Lower Limbs. The 
 
 general structure and number of the 
 bones of the lower limbs bear a strik- 
 ing similarity to those of the upper 
 limbs. Thus the leg, like the arm, is 
 arranged in three parts, the thigh, 
 the lower leg, and the foot. The 
 thigh bone corresponds to the hume- 
 rus ; the tibia and fibula to the ulna 
 and radius ; the ankle to the wrist ; 
 and the metatarsus and the phalanges 
 of the foot, to the metacarpus and the 
 phalanges of the hand. 
 
 The bones of the lower limbs may 
 be thus arranged : 
 
 Thigh : Femur, or thigh bone, 
 
 ( Patella, or knee-cap, 
 Lower Leg : J Tibia, or shin bone, 
 
 t Fibula, or splint bone, 
 
 7 Tarsal orankle bones, 
 5 Metatarsal or instep 
 Foot : \ bones, 
 
 I 14 Phalanges, or toe 
 
 L bones, 
 
 making 30 bones in all. 
 
 47. The Thigh. The longest and 
 strongest of all the bones is the 
 femur, or thigh bone. Its upper 
 end has a rounded head which fits 
 into the acetabulum, or the deep cup- 
 like cavity of the hip bone, forming 
 
 FIG. 22. Right Femur, or 
 Thigh Bone. 
 
42 PRACTICAL PHYSIOLOGY. 
 
 a perfect ball-and-socket joint. When covered with cartilage, 
 the ball fits so accurately into its socket that it may be retained 
 by atmospheric pressure alone (sec. 50). 
 
 The shaft of the femur is strong, and is ridged and roughened 
 in places for the attachment of the muscles. Its lower end is 
 broad and irregularly shaped, having two prominences called 
 condyles, separated by a groove, the whole fitted for forming a 
 hinge joint with the bones of the lower leg and the knee-cap. 
 
 48. The Lower Leg. The lower leg, like the forearm, con- 
 sists of two bones. The tibia, or shin bone, is the long three- 
 sided bone forming the front of the leg. 
 The sharp edge of the bone is easily 
 felt just under the skin. It articulates 
 with the lower end of the thigh bone, 
 forming with it a hinge joint. 
 
 The fibula, the companion bone of 
 the tibia, is the long, slender bone on 
 the outer side of the leg. It is firmly 
 fixed to the tibia at each end, and is 
 
 FIG. 23. Patella, or 
 
 Knee-Cap commonly spoken of as the small bone 
 
 of the leg. Its lower end forms the 
 
 outer projection of the ankle. In front of the knee joint, 
 embedded in a thick, strong tendon, is an irregularly disk- 
 shaped bone, the patella, or knee-cap. It increases the lever- 
 age of important muscles, and protects the front of the knee 
 joint, which is, from its position, much exposed to injury. 
 
 49. The Foot. The bones of the foot, 26 in number, con- 
 sist of the tarsal bones, the metatarsal, and the phalanges. 
 The tarsal bones are the seven small, irregular bones which 
 make up the ankle. These bones, like those of the wrist, are 
 compactly arranged, and are held firmly in place by ligaments 
 which allow a considerable amount of motion. 
 
THE BONES. 
 
 43 
 
 One of the ankle bones, the os 
 calcis, projects prominently back- 
 wards, forming the heel. An ex- 
 tensive surface is thus afforded 
 for the attachment of the strong 
 tendon of the calf of the leg, called 
 the tendon of Achilles. The large 
 bone above the heel bone, the as- 
 tragalus, articulates with the tibia, 
 forming a hinge joint, and receives 
 the weight of the body. 
 
 The metatarsal bones, corre- 
 sponding to the metacarpals of the 
 hand, are five in number, and form 
 the lower instep. 
 
 The phalanges are the fourteen 
 bones of the toes, three in each 
 except the great toe, which, like 
 the thumb, has two. They resem- 
 ble in number and plan the corre- 
 sponding bones in the hand. The 
 bones of the foot form a double arch, 
 an arch from before backwards, 
 and an arch from side to side. 
 The former is supported behind 
 by the os calcis, and in front by 
 the ends of the metatarsal bones. 
 The weight of the body falls per- 
 pendicularly on the astragalus, 
 which is the key-bone or crown 
 of the arch. The bones of the 
 foot are kept in place by powerful 
 ligaments, combining great 
 strength with elasticity. 
 
 FIG. 24. Right Tibia and Fibula. 
 (Anterior surface.) 
 
44 
 
 PRACTICAL PHYSIOLOGY. 
 
 FIG. 25. Bones of Right Foot. 
 (Dorsal surface.) 
 
 THE JOINTS. 
 
 50. Formation of Joints. 
 
 The various bones of the 
 skeleton are connected to- 
 gether at different parts of 
 their surfaces by joints, 
 or articulations. Many dif- 
 ferent kinds of joints have 
 been described, but the 
 same general plan obtains 
 for nearly all. They vary 
 according to the kind and 
 the amount of motion. 
 
 The principal structures 
 which unite in the forma- 
 tion of a joint are : bone, 
 cartilage, sy no vial mem- 
 brane, and ligaments. 
 Bones make the chief ele- 
 ment of all the joints, and 
 their adjoining surfaces are 
 shaped to meet the special 
 demands of each joint (Fig. 
 27). The joint-end of bones 
 is coated with a thin layer 
 of tough, elastic cartilage. 
 This is also used at the 
 edge of joint-cavities, form- 
 ing a ring to deepen them. 
 The rounded heads of bones 
 which move in them are 
 thus more securely held in 
 their sockets. 
 
THE BONES. 
 
 45 
 
 Besides these structures, the muscles also help to maintain 
 the joint-surfaces in proper relation. Another essential to the 
 action of the joints is the pressure of the outside air. This 
 may be sufficient to keep the articular surfaces in contact even 
 after all the muscles are removed. Thus the hip joint is so 
 completely surrounded by ligaments as to be air-tight ; and the 
 union is very strong. But if the ligaments be pierced and air 
 allowed to enter the joint, the union at once becomes much less 
 close, and the head of the thigh bone falls away as far as the 
 ligaments will allow it. 
 
 51. Synovial Membrane. A very delicate connective 
 tissue, called the synovial membrane, lines the capsules of the 
 joints, and covers the ligaments connected with them. It secretes 
 the synovia, or joint oil, a thick and glairy fluid, like the white 
 of a raw egg, which thoroughly lubricates the inner surfaces of 
 the joints. Thus the friction and heat developed by movement 
 are reduced, and every part of a joint is enabled to act smoothly. 
 
 52. Ligaments. The bones are fastened together, held in 
 place, and their movements controlled, to a certain extent, by 
 bands of various forms, called ligaments. These are com- 
 posed mainly of bundles of white fibrous tissue placed parallel 
 to, or closely interlaced with, one another, and present a shining, 
 silvery aspect. They extend from one of the articulating bones 
 to another, strongly supporting the joint, which they some- 
 times completely envelope with a kind of cap (Fig. 28). This 
 prevents the bones from being easily dislocated. It is difficult, 
 for instance, to separate the two bones in a shoulder or leg of 
 mutton, they are so firmly held together by tough ligaments. 
 
 While ligaments are pliable and flexible, permitting free move- 
 ment, they are also wonderfully strong and inextensible. A 
 bone may be broken, or its end torn off, before its ligaments can 
 be ruptured. The wrist end of the radius, for instance, is often 
 torn off by force exerted on its ligaments without their rupture. 
 
46 PRACTICAL PHYSIOLOGY. 
 
 The ligaments are so numerous and various and are in some 
 parts so interwoven with each other, that space does not allow 
 even mention of those that are important. At the knee joint, 
 for instance, there are no less than fifteen distinct ligaments. 
 
 53. Imperfect Joints. It is only perfect joints that are 
 fully equipped with the structures just mentioned. Some joints 
 lack one or more, and are therefore called imperfect joints. 
 Such joints allow little or no motion and have 
 no smooth cartilages at their edges. Thus, the 
 bones of the skull are dovetailed by joints called 
 sutures, which are immovable. The union be- 
 tween the vertebrae affords a good example of 
 .imperfect joints which are partially movable. 
 
 54. Perfect Joints. There are various forms 
 
 of perfect joints, according to the nature and 
 FIG. 26. Elastic J 
 
 Tissue from the amount of movement permitted. I hey are 
 Ligaments about divided into hinge j oints, ball-and-socket j oints, 
 
 The hinge joints allow forward and back- 
 ward movements like a hinge. These joints are the most numer- 
 ous in the body, as the elbow, the ankle, and the knee joints. 
 
 In the ball-and-socket joints a beautiful contrivance 
 the rounded head of one bone fits into a socket in the other, 
 as the hip joint and shoulder joint. These joints permit free 
 motion in almost every direction. 
 
 In the pivot joint a kind of peg in one bone fits into a notch 
 in another. The best example of this is the joint between the 
 first and second vertebrae (see sec. 38). The radius moves 
 around on the ulna by means of a pivot joint. The radius, as 
 well as the bones of the wrist and hand, turns around, thus 
 enabling us to turn the palm of the hand upwards and down- 
 wards. In many joints the extent of motion amounts to only 
 a slight gliding between the ends of the bones. 
 
THE BONES. 
 
 47 
 
 55. Uses of the Bones. The bones serve many important 
 and useful purposes. The skeleton, a general framework, 
 affords protection, support, and leverage to the bodily tissues. 
 Thus, the bones of the skull and of the chest protect the brain, 
 the lungs, and the heart; the bones of the legs support the 
 weight of the body ; and the long bones 
 of the limbs are levers to which muscles 
 are attached. 
 
 Owing to the various duties they have 
 to perform, the bones are constructed in 
 many different shapes. Some are broad 
 and flat ; others, long and cylindrical ; 
 and a large number very irregular in 
 form. Each bone is not only different 
 from all the others, but is also curiously 
 adapted to its particular place and use. 
 
 Nothing could be more admirable 
 than the mechanism by which each one 
 of the bones is enabled to fulfill the 
 manifold purposes for which it was de- 
 signed. We have seen how the bones 
 of the cranium are united by sutures in 
 a manner the better to allow the delicate 
 brain to grow, and to afford it protec- 
 tion from violence. The arched ar- 
 rangement of the bones of the foot has several mechanical 
 advantages, the most important being that it gives firmness and 
 elasticity to the foot, which thus serves as a support for the 
 weight of the body, and as the chief instrument of locomotion. 
 
 The complicated organ of hearing is protected by a winding 
 series of minute apartments, in the rock-like portion of the 
 temporal bone. The socket for the eye has a jutting ridge of 
 bone all around it, to guard the organ of vision against injury. 
 Grooves and canals, formed in hard bone, lodge and protect 
 
 FIG. 27. Showing how the 
 Ends of the Bones are 
 shaped to form the Elbow 
 Joint. (The cut ends of 
 a few ligaments are seen.) 
 
4 8 
 
 PRACTICAL PHYSIOLOGY. 
 
 minute nerves and tiny blood-vessels. The surfaces of bones 
 are often provided with grooves, sharp edges, and rough pro- 
 jections, for the origin and insertion of muscles. 
 
 56. The Bones in Infancy and Childhood. The bones of 
 
 the infant, consisting almost wholly of cartilage, are not stiff 
 and hard as in after life, but flexible and elastic. As the 
 
 child grows, the bones become more 
 solid and firmer from a gradually 
 increased deposit of lime salts. In 
 time they become capable of sup- 
 porting the body and sustaining 
 the action of the muscles. The 
 reason is that well-developed bones 
 would be of no use to a child that 
 had not muscular strength to sup- 
 port its body. Again, the numerous 
 falls and tumbles that the child sus- 
 tains before it is able to walk, would 
 result in broken bones almost every 
 day of its life. As it is, young 
 children meet with a great variety 
 of falls without serious injury. 
 
 But this condition of things has 
 its dangers. The fact that a child's 
 bones bend easily, also renders 
 them liable to permanent change 
 of shape. Thus, children often be- 
 come bow-legged when allowed to 
 walk too early. Moderate exercise, 
 however, even in infancy, promotes the health of the bones as 
 well as of the other tissues. Hence a child may be kept too 
 long in its cradle, or wheeled about too much in a carriage, 
 when the full use of its limbs would furnish proper exercise and 
 enable it to walk earlier. 
 
 FIG. 28. External Ligaments 
 of the Knee. 
 
THE BONES. 
 
 49 
 
 57. Positions at School. Great care must be exercised by teachers 
 that children do not form the habit of taking injurious positions at 
 school. The desks should not be too low, causing a forward stoop ; 
 or too high, throwing one shoulder up and giving a twist to the spine. 
 If the seats are too low there will result an undue strain on the 
 shoulder and the backbone ; if too 
 high, the feet have no proper support, 
 the thighs may be bent by the weight 
 of the feet and legs, and there is a 
 prolonged strain on the hips and 
 back. Curvature of the spine and 
 round shoulders often result from 
 long-continued positions at school in 
 seats and at desks which are not 
 adapted to the physical build of the 
 occupant. 
 
 A few simple rules should guide 
 teachers and school officials in pro- 
 viding proper furniture for pupils. 
 Seats should be regulated according 
 to the size and age of the pupils, and 
 frequent changes of seats should be 
 made. At least three sizes of desks 
 should be used in every schoolroom, 
 and more in ungraded schools. The 
 feet of each pupil should rest firmly 
 on the floor, and the edge of the desk 
 should be about one inch higher 
 than the level of the elbows. A line 
 dropped from the edge of the desk 
 should strike the front edge of the 
 seat. Sliding down into the seat, 
 bending too much over the desk while writing and studying, sitting 
 on one foot or resting on the small of the back, are all ungraceful 
 and unhealthful positions, and are often taken by pupils old enough 
 to know better. This topic is well worth the vigilance of every 
 thoughtful teacher, especially of one in the lower grades. 
 
 FIG. 29. Section of the Knee Joint. 
 (Showing its internal structure.) 
 
 A, tendon of the semi-membranosus 
 muscle cut across; B, F, tendon of 
 same muscle; C, internal condyle 
 of femur; D, posterior crucial liga- 
 ment; E, internal interarticular 
 fibro-cartilage ; G, bursa under knee- 
 cap; H, ligament of knee-cap; K, 
 fatty mass under knee-cap ; L, ante- 
 rior crucial ligament cut across ; P, 
 patella, or knee-cap. 
 
$O PRACTICAL PHYSIOLOGY. 
 
 58. The Bones in After Life. Popular impression attri- 
 butes a less share of life, or a lower grade of vitality, to the 
 bones than to any other part of the body. But really they 
 have their own circulation and nutrition, and even nervous 
 relations. Thus, bones are the seat of active vital processes, 
 not only during childhood, but also in adult life, and in fact 
 throughout life, except perhaps in extreme old age. The final 
 knitting together of the ends of some of the bones with their 
 shafts does not occur until somewhat late in life. For example, 
 the upper end of the tibia and its shaft do not unite until the 
 twenty-first year. The separate bones of the sacrum do not 
 fully knit into one solid bone until the twenty-fifth year. 
 Hence, the risk of subjecting the bones of young persons to 
 undue violence from injudicious physical exercise as in rowing, 
 baseball, football, and bicycle-riding. 
 
 The bones during life are constantly going through the 
 process of absorption and reconstruction. They are easily 
 modified in their growth. Thus the continued pressure of 
 some morbid deposit, as a tumor or cancer, or an enlargement 
 of an artery, may cause the absorption or distortion of bones 
 as readily as of one of the softer tissues. The distortion re- 
 sulting from tight lacing is a familiar illustration of the facility 
 with which the bones may be modified by prolonged pressure. 
 
 Some savage races, not content with the natural shape of the 
 head, take special methods to mould it by continued artificial 
 pressure, so that it may conform in its distortion to the fashion of 
 their tribe or race. This custom is one of the most ancient and 
 widespread with which we are acquainted. .In some cases the 
 skull is flattened, as seen in certain Indian tribes on our Pacific 
 coast, while with other tribes on the same coast it is compressed 
 into a sort of conical appearance. In such cases the brain is 
 compelled, of course, to accommodate itself to the change in 
 the shape of .the head ; and this is done, it is said, without any 
 serious result. 
 
THE BONES. 51 
 
 59. Sprains and Dislocations. A twist or strain of the 
 ligaments and soft parts about a> joint is known as a sprain, 
 and may result from a great variety of accidents. When a per- 
 son falls, the foot is frequently caught under him, and the twist 
 comes upon the ligaments and tissues of the ankle. The liga- 
 ments cannot stretch, and so have to endure the wrench upon 
 the joint. The result is a sprained ankle. Next to the ankle, 
 a sprain of the wrist is most common. A person tries, by 
 throwing out his hand, to save himself from a fall, and the 
 weight of the body brings the strain upon the firmly fixed 
 wrist. As a result of a sprain, the ligaments may be wrenched 
 or torn, and even a piece of an adjacent bone may be torn off; 
 the soft parts about the injured joint are bruised, and the 
 neighboring muscles put to a severe stretch. A sprain may be 
 a slight affair, needing only a brief rest, or it may be severe 
 and painful enough to call for the most skillful treatment by a 
 surgeon. Lack of proper care in severe sprains often results 
 in permanent lameness. 
 
 A fall or a blow may bring such a sudden wrench or twist 
 upon the ligaments as to force a bone out of place. This 
 displacement is known as a dislocation. A child may trip or 
 fall during play and put his elbow out of joint. A fall from 
 horseback, a carriage, or a bicycle may result in a dislocation 
 of the shoulder joint. In playing baseball a swift ball often 
 knocks a finger out of joint. A dislocation must be reduced 
 at once. Any delay or carelessness may make a serious and 
 painful affair of it, as the torn and bruised parts rapidly swell 
 and become extremely sensitive. 
 
 60. Broken Bones. The bones, especially those of the 
 upper limbs, are often fractured or broken. The simple frac- 
 ture is the most common form, the bone being broken in a 
 single place with no opening through the skin. When properly 
 adjusted, the bone heals rapidly. Sometimes bones are crushed 
 into a number of fragments ; this is a comminuted fracture. 
 
52 PRACTICAL PHYSIOLOGY. 
 
 When, besides the break, there is an opening through the soft 
 parts and surface of the body, we have a compound fracture. 
 This is a serious injury, and calls for the best surgical treat- 
 ment. 
 
 A bone may be bent, or only partly broken, or split. This is 
 called "a green-stick fracture," from its resemblance to a half- 
 broken green stick. This fracture is more common in the 
 bones of children. 
 
 Fractures may be caused by direct violence, as when a bone 
 is broken at a certain point by some powerful force, as a blow 
 from a baseball bat or a fall from a horse. Again, a bone may 
 be broken by indirect violence, as when a person being about 
 to fall, throws out his hand to save himself. The force of the 
 fall on the hand often breaks the wrist, by which is meant 
 the fracture of the lower end of the radius, often known as the 
 "silver-fork fracture." This accident is common in winter 
 from a fall or slip on the ice. 
 
 Sometimes bones are broken at a distance from the point of 
 injury, as in a fracture of the ribs by violent compression of the 
 chest ; or fracture may occur from the vibration of a blow, as 
 when a fall or blow upon the top of the head produces fracture 
 of the bones at the base of the brain. 1 
 
 61. Treatment for Broken Bones. When a bone is broken 
 a surgeon is needed to set it, that is, to bring the broken parts 
 into their natural position, and retain them by proper appliances. 
 Nature throws out between and around the broken ends of 
 bones a supply of repair material known as plastic lymph, 
 which is changed to fibrous tissue, then to cartilage, and finally 
 
 1 The mechanism of this remarkable effect is clearly shown by an experiment 
 which the late Dr. Oliver Wendell Holmes used to take delight in performing in his 
 anatomical lectures at the Harvard Medical College. He had a strong iron bar made 
 into a ring of some eight inches in diameter, with a space left between the ends just 
 large enough to be filled by an English walnut. The ring was then dropped to the 
 floor so as to strike on the convexity just opposite to the walnut, which invariably 
 was broken to pieces. 
 
THE BONES. 53 
 
 to bone. This material serves as a sort of cement to hold the 
 fractured parts together. The excess of this at the point of 
 union can be felt under the skin for some time after the bone 
 is healed. 
 
 With old people a broken bone is often a serious matter, and 
 may cripple them for life or prove fatal. A trifling fall, for 
 instance, may cause a broken hip (popularly so called, though 
 really a fracture of the neck of the femur), from the shock of 
 which, and the subsequent pain and exhaustion, an aged person 
 may die in a few weeks. In young people, however, the parts 
 of a broken bone will knit together in three or four weeks after 
 the fracture is reduced ; while in adults, six or even more may 
 be required for firm union; After a broken bone is strong 
 enough to be used, it is fragile for some time ; and great care 
 must be taken, especially with children, that the injured parts 
 may not be broken again before perfect union takes place. 1 
 
 62. The Effect of Alcohol upon the Bones. While the 
 growth of the bones occurs, of course, mainly during the earlier 
 years of life, yet they do not attain their full maturity until 
 about the twenty-fifth year ; and it is stated that in persons 
 devoted to intellectual pursuits, the skull grows even after that 
 age. It is plainly necessary that during this period of bone 
 growth the nutrition of the body should be of the best, that 
 the bones may be built up from pure blood, and supplied with 
 all the materials for a large and durable framework. Else the 
 body will be feeble and stunted, and so through life fall short 
 of its purpose. 
 
 If this bony foundation be then laid wrong, the defect can 
 never be remedied. This condition is seen in young persons 
 who have been underfed and overworked. But the use of 
 alcoholic liquors produces a similar effect, hindering bone cell- 
 
 1 For the treatment of accidents and emergencies which may occur with reference 
 to the bones, see Chapter XIII. 
 
54 PRACTICAL PHYSIOLOGY. 
 
 growth and preventing full development. 1 The appetite is 
 diminished, nutrition perverted and impaired, the stature 
 stunted, and both bodily and mental powers are enfeebled. 
 
 63. Effect of Tobacco upon the Bones. Another narcotic, 
 the destructive influence of which is wide and serious, is 
 tobacco. Its pernicious influence, like that of alcohol, is pecu- 
 liarly hurtful to the young, as the cell development during the 
 years of growth is easily disturbed by noxious agents. The 
 bone growth is by cells, and a powerful narcotic like tobacco 
 retards cell-growth, and thus hinders the building up of the 
 bodily frame. The formation of healthy bone demands good, 
 nutritious blood, but if instead of this, the material furnished 
 for the production of blood is poor in quality or loaded with 
 poisonous narcotics, the body thus defrauded of its proper 
 building material becomes undergrown and enfeebled. 
 
 Two unfavorable facts accompany this serious drawback : 
 one is, that owing to the insidious nature of the smoky poison 2 
 (cigarettes are its worst form) ' the cause may often be un- 
 suspected, and so go on, unchecked ; and the other, that the 
 progress of growth once interrupted, the gap can never be fully 
 made up. Nature does her best to repair damages and to 
 restore defects, but never goes backwards to remedy neglects. 
 
 1 " Besides the danger connected with the use of alcoholic drinks which is com- 
 mon to them with other narcotic poisons, alcohol retards the growth of young cells 
 and prevents their proper development. Now, the bodies of all animals are made up 
 largely of cells, . . . and the cells being the living part of the animal, it is especially 
 important that they should not be injured or badly nourished while they are growing. 
 So that alcohol in all its forms is particularly injurious to young persons, as it 
 retards their growth, and stunts both body and mind. This is the theory of Dr. 
 Lionel S. Beale, a celebrated microscopist and thinker, and is quite generally ac- 
 cepted." DR. ROGER S. TRACY, of the New York Board of Health. 
 
 2 " In its action on the system nicotine is one of the most powerful poisons known. 
 A drop of it in a concentrated form was found sufficient to kill a dog, and small birds 
 perished at the approach of a tube containing it." WOOD'S Materia Medica. 
 
 " Tobacco appears to chiefly affect the heart and brain, and I have therefore 
 placed it among cerebral and cardiac poisons." TAYLOR'S Treatise on Poisons. 
 
THE BONES. 55 
 
 ADDITIONAL EXPERIMENTS. 
 
 Experiment n. Take a portion of the decalcified bone obtained from 
 Experiment 4, and wash it thoroughly in water : in this it is insoluble. 
 Place it in a solution of carbonate of soda and wash it again. Boil it in 
 water, and from it gelatine will be obtained. 
 
 Experiment 12. Dissolve in hydrochloric acid a small piece of the 
 powdered bone-ash obtained from Experiment 3. Bubbles of carbon 
 dioxid are given off, indicating the presence of a carbonate. Dilute the 
 solution ; add an excess of ammonia, and we find a white precipitate of the 
 phosphate of lime and of magnesia. 
 
 Experiment 13. Filter the solution in the preceding experiment, and to 
 the filtrate add oxalate of ammonia. The result is a white precipitate of 
 the oxalate of lime, showing there is lime present, but not as a phosphate. 
 
 Experiment 14. To the solution of mineral matters obtained from 
 Experiment 3, add acetate of soda until free acetic acid is present, recog- 
 nized by the smell (like dilute vinegar) ; then add oxalate of ammonia. 
 The result will be a copious white precipitate of lime salts. 
 
 Experiment 15. To show how the cancellous structure of bone is able to 
 support a great deal of weight. Have the market-man saw out a cubic inch 
 from the cancellous tissue of a fresh beef bone and place it on a table with its 
 principal layers upright. Balance a heavy book upon it, and then gradually 
 place upon it various articles and note how many pounds it will support 
 before giving way. 
 
 Experiment 16. Repeat the last experiment, using a cube of the decal- 
 cified bone obtained from Experiment 4. 
 
 NOTE. As the succeeding chapters are studied, additional experiments on bones 
 and their relation to other parts of the body, will readily suggest themselves to the 
 ingenious instructor or the thoughtful student. Such experiments may be utilized 
 for review or other exercises. 
 
REVIEW ANALYSIS: THE SKELETON (206 bones). 
 
 THE HEAD 
 (28 bones). 
 
 I. CRANIUM 
 
 (8 bones) 
 
 [I. 
 
 FACE ) 
 
 (14 bones) ) 
 
 THE TRUNK 
 
 (54 bones). 
 
 UPPER LIMBS 
 
 (64 bones). 
 
 LOWER LIMBS 
 (60 bones). 
 
 III. THE EAR 
 
 (6 bones) 
 
 I. SPINAL COLUMN |_ 
 
 (26 bones) j 
 
 II. THERlBS ) 
 (24 bones) ( 
 
 III. STERNUM. 
 
 IV. Two HIP BONES. 
 V. HYOID BONE. 
 
 I. UPPER ARM . . 
 II. FOREARM . . . 
 
 III. HAND 
 
 I. THIGH . . . . 
 II. LOWER LEG . . 
 
 III. FOOT . 
 
 1 Frontal, 
 
 2 Parietal, 
 2 Temporal, 
 i Occipital, 
 i Sphenoid, 
 
 1 Ethmoid. 
 
 2 Superior Maxillary, 
 2 Malar, 
 
 2 Nasal, 
 
 2 Lachrymal Bones, 
 
 2 Palate Bones, 
 
 2 Turbinated, 
 i Vomer, 
 
 1 Lower Maxillary. 
 
 Hammer, 
 
 Anvil, 
 
 Stirrup. 
 
 7 Cervical Vertebrae, 
 12 Dorsal Vertebrae, 
 
 5 Lumbar Vertebrae, 
 
 r Sacrum, 
 t Coccyx. 
 
 7 True Ribs, 
 
 3 False Ribs, 
 
 2 Floating Ribs. 
 
 Scapula, 
 Clavicle, 
 Humerus. 
 
 Ulna, 
 Radius. 
 
 8 Carpal Bones, 
 5 Metacarpal Bones. 
 14 Phalanges. 
 
 Femur. 
 
 Patella, 
 
 Tibia, 
 
 Fibula. 
 
 7 Tarsal Bones, 
 5 Metatarsal Bones, 
 14 Phalanges. 
 
CHAPTER III. 
 THE MUSCLES. 
 
 64. Motion in Animals. All motion of our bodies is pro- 
 duced by means of muscles. Not only the limbs are moved 
 by them, but even the movements of the stomach and of the 
 heart are controlled by muscles. Every part of the body which 
 is capable of motion has its own special set of muscles. 
 
 Even when the higher animals are at rest it is possible to 
 observe some kind of motion in them. Trees and stones never 
 move unless acted upon by external force, while the infant and 
 the tiniest insect can execute a great variety of movements. 
 Even in the deepest sleep the beating of the heart and the 
 motion of the chest never cease. In fact, the power to execute 
 spontaneous movement is the most characteristic property of 
 living animals. 
 
 65. Kinds of Muscles. Most of the bodily movements, such 
 as affect the limbs and the body as a whole, are performed by 
 muscles under our control. These muscles make up the red 
 flesh or lean parts, which, together with the fat, clothe the 
 bony framework, and give to it general form and proportion. 
 We call these muscular tissues voluntary muscles, because 
 they usually act under the control of the will. 
 
 The internal organs, as those of digestion, secretion, circula- 
 tion, and respiration, perform their functions by means of 
 muscular activity of another kind, that is, by that of muscles 
 not under our control. This work goes on quite independently 
 of the will, and during sleep. We call the instruments of this 
 activity involuntary muscles. The voluntary muscles, from 
 peculiarities revealed by the microscope, are also known as 
 
PRACTICAL PHYSIOLOGY. 
 
 striped or striated muscles. The involuntary from their 
 smooth, regular appearance under the microscope are called 
 the unstriped or non-striated muscles. 
 
 The two kinds of muscles, then, are the red, voluntary, 
 striated muscles, and the smooth, involuntary, non-striated 
 muscles. 
 
 66. Structure of Voluntary Muscles. The main substance 
 which clothes the bony framework of the body, and which 
 forms about two-fifths of its weight, is the volun- 
 tary muscular tissue. These muscles do not 
 cover and surround the bones in continuous 
 sheets, but consist of separate bundles of flesh, 
 varying in size and length, many of which are 
 capable of independent movement. 
 
 Each muscle has its own set of blood- 
 vessels, lymphatics, and nerves. It is the 
 blood that gives the red color to the flesh. 
 Blood-vessels and nerves on their way to other 
 parts of the body, do not pass through the 
 muscles, but between them. Each muscle is 
 FIG. 30. -Striated enveloped in its own sheath of connective tis- 
 (voiuntary) Mus- sue known as the fascia. Muscles are not 
 usually connected directly with bones, but by 
 
 cular Fibers. 
 
 A, fiber 
 
 into disks; B, fi- 
 brillae (highly mag- 
 nified); C, cross 
 section of a disk. 
 
 s means of white, glistening cords called tendons. 
 
 If a small piece of muscle be examined under 
 a microscope it is found to be made up of bun- 
 dles of fibers. Each fiber is enclosed within a 
 delicate, transparent sheath, known as the sarcolemma. If 
 one of these fibers be further examined under a microscope, it 
 will be seen to consist of a great number of still more minute 
 fibers called fibrillae. These fibers are also seen marked cross- 
 wise with dark stripes, and can be separated at each stripe into 
 disks. These cross markings account for the name striped or 
 striated muscle. 
 
THE MUSCLES. 
 
 59 
 
 The fibrillae, then, are bound together in a bundle to form a 
 fiber, which is enveloped in its own sheath, the sarcolemma. 
 These fibers, in turn, are further bound together to form larger 
 bundles called fasciculi, and these, too, are enclosed in a 
 sheath of connective tissue. The muscle itself is made up of a 
 number of these fasciculi bound together 
 by a denser layer of connective tissue. 
 
 Experiment 17. To show the gross structure of 
 muscle. Take a small portion of a large muscle, as 
 a strip of lean corned beef. Have it boiled until 
 its fibers can be easily separated. Pick the bundles 
 and fasciculi apart until the fibers are so fine as to 
 be almost invisible to the naked eye. Continue the 
 experiment with the help of a hand magnifying 
 glass or a microscope. 
 
 67. The Involuntary Muscles. These 
 muscles consist of ribbon-shaped bands 
 which surround hollow fleshy tubes or 
 cavities. We might compare them to India FIG. 31. 
 rubber rings on rolls of paper. As they 
 are never attached to bony levers, they (Highly magnified.) 
 have no need of tendons. 
 
 The microscope shows these muscles to consist not of fibers, 
 but of long spindle-shaped cells, united to form sheets or 
 bands. They have no sarcolemma, stripes, or cross markings 
 like those of the voluntary muscles. Hence their name of non- 
 striated, or unstriped, and smooth muscles. 
 
 The involuntary muscles respond to irritation much less 
 rapidly than do the voluntary. The wave of contraction passes 
 over them more slowly and more irregularly, one part contracting 
 while another is relaxing. This may readily be seen in the 
 muscular action of the intestines, called vermicular motion. It 
 is the irregular and excessive contraction of the muscular 
 walls of the bowels that produces the cramp-like pains of colic. 
 
 The smooth muscles are found in the tissues of the heart, 
 
 A, Muscular 
 
6o 
 
 PRACTICAL PHYSIOLOGY. 
 
 lungs, blood-vessels, stomach, and intestines. In the stomach 
 their contraction produces the motion by which the food is 
 churned about ; in the arteries and veins they help supply the 
 force by which the blood is driven along, and in the intestines 
 that by which the partly digested food is mainly kept in motion. 
 Thus all the great vital functions are carried on, regardless 
 of the will of the individual, or of any outward circumstances. 
 If it required an effort of the will to control the action 
 of the internal organs we could not think of anything 
 else. It would take all our time to attend to living. 
 Hence the care of such delicate and important ma- 
 chinery has wisely been put beyond our control. 
 
 Thus, too, these muscles act instinctively without 
 training ; but the voluntary need long and careful 
 education. A babe can use the muscles of swallow- 
 ing on the first day of its life as well as it ever can. 
 But as it grows up, long and patient education of its 
 voluntary muscles is needed to achieve walking, writ- 
 ing, use of musical instruments, and many other acts 
 of daily life. 
 
 FIG. 32. 
 
 A Spindle 
 Cell of In- 
 voluntary 
 Muscle. 
 (Highly 
 
 magnified.) 
 
 Experiment 18. To show the general appearance of the 
 muscles. Obtain the lower part of a sheep's or calf's leg, with 
 the most of the lean meat and the hoof left on. One or more 
 of the muscles with their bundles of fibers, fascia, and tendons, 
 are readily made out with a little careful dissection. The dis- 
 section should be made a few days before it is wanted and 
 the parts allowed to harden somewhat in dilute alcohol. 
 
 68. Properties of Muscular Tissue. The peculiar property 
 of living muscular tissue is irritability, or the capacity of 
 responding to a stimulus. When a muscle is irritated it 
 responds by contracting. By this act the muscle does not 
 diminish its bulk to any extent ; it simply changes its form. 
 The ends of the muscle are drawn nearer each other and the 
 middle is thicker. 
 
THE MUSCLES. 6l 
 
 Muscles do not shorten themselves all at once, but the con- 
 traction passes quickly over them in the form of a wave. They 
 are usually stimulated by nervous action. The delicate nerve 
 fibrils which end in the fibers communicate with the brain, the 
 center of the will power. Hence, when the brain commands, a 
 nervous impulse, sent along the nerve fibers, becomes the excit- 
 ing stimulus which acts upon the muscles and makes them 
 shorter, harder, and more rigid. 1 
 
 Muscles, however, will respond to other than this usual 
 stimulus. Thus an electrical current may have a similar effect. 
 Heat, also, may produce muscular contraction. Mechanical 
 means, such as a sharp blow or pinching, may irritate a muscle 
 and cause it to contract. 
 
 We must remember that this property of contraction is 
 inherent and belongs to the muscle itself. This power of con- 
 traction is often independent of the brain. Thus, on pricking 
 the heart of a fish an hour after removal from its body, obvious 
 contraction will occur. In this case it is not the nerve force 
 from the brain that supplies the energy for contraction. The 
 power of contraction is inherent in the muscle substance, and 
 the stimulus by irritating the nerve ganglia of the heart simply 
 affords the opportunity for its exercise. 
 
 Contraction is not, however, the natural state of a muscle. 
 In time it is tired, and begins to relax. Even the heart, the 
 hardest-working muscle, has short periods of rest between 
 its beats. Muscles are highly elastic as well as contractile. 
 By this property muscle yields to a stretching force, and 
 returns to its original length if the stretching has not been 
 excessive. 
 
 1 " Certain events occur in the brain ; these give rise to other events, to changes 
 which travel along certain bundles of fibers called nerves, and so reach certain 
 muscles. Arrived at the muscles, these changes in the nerves, which physiologists 
 call nervous impulses, induce changes in the muscles, by virtue of which these shorten 
 contract, bring their ends together, and so, working upon bony levers, bend the arm 
 or hand, or lift the weight." PROFESSOR MICHAEL FOSTER. 
 
62 
 
 PRACTICAL PHYSIOLOGY. 
 
 FIG. 33. Superficial Muscles of the Body (Front View). 
 
THE MUSCLES. 63 
 
 69. The Object of Contraction. The object of contraction 
 is obvious. Like rubber bands, if one end of a muscle be 
 fixed and the other attached to some object which is free to 
 move, the contraction of the muscle will bring the movable 
 body nearer to the fixed point. A weight fastened to the free 
 end of a muscle may be lifted when the muscle contracts. 
 Thus by their contraction muscles are able to do their work. 
 They even contract more vigorously when resistance is opposed 
 to them than when it is not. With increased weight there is 
 an increased amount of work to be done. The greater resist- 
 ance calls forth a greater action of the muscle. This is true 
 up to a certain point, but when the limit has been passed, the 
 muscle quickly fails to respond. 
 
 Again, muscles work best with a certain degree of rapidity 
 provided the irritations do not follow each other too rapidly. 
 If, however, the contractions are too rapid, the muscles become 
 exhausted and fatigue results. When the feeling of fatigue 
 passes away with rest, the muscle recovers its power. While 
 we are resting, the blood is pouring in fresh supplies of building 
 material. 
 
 Experiment 19. To show how muscles relax and contract. Lay your 
 left forearm on a table ; grasp with the right hand the mass of flesh on the 
 front of the upper arm. Now gradually raise the forearm, keeping the 
 elbow on the table. Note that the muscle thickens as the hand rises. 
 This illustrates the contraction of the biceps, and is popularly called " trying 
 your muscle." Reverse the act. Keep the elbow in position, bring the 
 forearm slowly to the table, and the biceps appears to become softer and 
 smaller, it relaxes. 
 
 Experiment 20. Repeat the same experiment with other muscles. With 
 the right hand grasp firmly the extended left forearm. Extend and flex the 
 fingers vigorously. Note the effect on the muscles and tendons of the fore- 
 arm. Grasp with the right hand the calf of the extended right leg, and 
 vigorously flex the leg, bringing it near to the body. Note the contractions 
 and relaxations of the muscles. 
 
64 PRACTICAL PHYSIOLOGY. 
 
 70. Arrangement of Muscles. Muscles are not connected 
 directly with bones. The mass of flesh tapers off towards the 
 ends, where the fibers pass into white, glistening cords known 
 as tendons. The place at which a muscle is attached to a 
 bone, generally by means of a tendon, is called its origin ; the 
 end connected with the movable bone is its insertion. 
 
 There are about 400 muscles in the human body, all neces- 
 sary for its various movements. They vary greatly in shape 
 and size, according to their position and use. Some are from 
 one to two feet long, others only a fraction of an inch. Some 
 are long and spindle-shaped, others thin and broad, while still 
 others form rings. Thus some of the muscles of the arm and 
 thigh are long and tapering, while the abdominal muscles are 
 thin and broad because they help form walls for cavities. 
 Again, the muscular fibers which surround and by their con- 
 traction close certain orifices, as those of the eyelids and lips, 
 often radiate like the spokes of a wheel. 
 
 Muscles are named according to their shape, position, division 
 of origin or insertion, and their function. Thus we have the 
 recti (straight), and the deltoid (A, delta), the brachial (arm), 
 pectoral (breast), and the intercostals (between the ribs), so 
 named from their position. Again, we have the biceps (two- 
 headed), triceps (three-headed), and many others with similar 
 names, so called from the points of origin and insertion. We 
 find other groups named after their special use. The muscles 
 which bend the limbs are called flexors while those which 
 straighten them are known as extensors. 
 
 After a bone has been moved by the contraction of a muscle, 
 it is brought back to its position by the contraction of another 
 muscle on the opposite side, the former muscle meanwhile 
 being relaxed. Muscles thus acting in opposition to each 
 other are called antagonistic. Thus the biceps serves as one 
 of the antagonists to the triceps, and the various flexors and 
 extensors of the limbs are antagonistic to one another. 
 
THE MUSCLES. 
 
 71. The Tendons. The muscles which move the bones by 
 their contraction taper for the most part, as before mentioned, 
 into tendons. These are commonly very strong cords, like 
 belts or straps, made up of white, fibrous tissue. 
 
 Tendons are most numerous about the larger joints, where 
 they permit free action and yet oc- 
 cupy but little space. Large and 
 prominent muscles in these places 
 would be clumsy and inconvenient. 
 If we bend the arm or leg forcibly, 
 and grasp the inside of the elbow 
 or knee joint, we can feel the ten- 
 dons beneath the skin. The numer- 
 ous tendons in the palm or on the 
 back of the hand contribute to its 
 marvelous dexterity and flexibility. 
 The thickest and strongest tendon 
 in the body is the tendon of Achil- 
 les, which connects the great mus- 
 cles in the calf of the leg with the 
 heel bone (sec. 49). 
 
 When muscles contract forcibly, 
 they pull upon the tendons which 
 transmit the movement to the bones 
 to which they are attached. Ten- 
 dons may be compared to ropes or 
 cords which, when pulled, are made 
 to act upon distant objects to which 
 one end is fastened. Sometimes the tendon runs down the 
 middle of a muscle, and the fibers run obliquely into it, the 
 tendon resembling the quill in a feather. Again, tendons are 
 spread out in a flat layer on the surface of muscles, in which 
 case they are called aponeuroses. Sometimes a tendon is found 
 in the middle of a muscle as well as at each end of it. 
 
 FIG. 34. The Biceps Muscle 
 dissected to show its Tendons. 
 
66 PRACTICAL PHYSIOLOGY. 
 
 72. SynOvial Sheaths and Sacs. The rapid movement of 
 the tendons over bony surfaces and prominences would soon 
 produce an undue amount of heat and friction unless some 
 means existed to make the motion as easy as possible. This 
 is supplied by sheaths which form a double lining around the 
 tendons. The opposed surfaces are lined with synovial mem- 
 brane, 1 the secretion from which oils the sheaths in which the 
 tendons move. 
 
 Little closed sacs, called synovial sacs or bursas, similarly 
 lined and containing fluid, are also found in special places be- 
 tween two surfaces where much motion is required. There 
 are two of these bursae near the patella, one superficial, just 
 under the skin ; the other deep beneath the bone (Fig. 29). 
 Without these, the constant motion of the knee-pan and its 
 tendons in walking would produce undue friction and heat and 
 consequent inflammation. Similar, though smaller, sacs are 
 found over the point of the elbow, over the knuckles, the ankle 
 bones, and various other prominent points. These sacs answer 
 a very important purpose, and are liable to various forms of 
 inflammation. 
 
 Experiment 21. Examine carefully the tendons in the parts dissected in 
 Experiment 18. Pull on the muscles and the tendons, and note how they 
 act to move the parts. This may be also admirably shown on the leg of a 
 fowl or turkey from a kitchen or obtained at the market. 
 
 Obtain the hoof of a calf or sheep with one end of the tendon of Achilles 
 still attached. Dissect it and test its strength. 
 
 73. Mechanism of Movement. The active agents of bodily 
 movements, as we have seen, are the muscles, which by their 
 contraction cause the bones to move one on the other. All these 
 movements, both of motion and of locomotion, occur accord- 
 ing to certain fixed laws of mechanics. The bones, to which a 
 
 1 The synovial membranes are almost identical in structure with serous mem- 
 branes (page 176), but the secretion is thicker and more like the white of egg. 
 
THE MUSCLES. 
 
 6 7 
 
 P W 
 
 great proportion of the muscles in the body are attached, act 
 as distinct levers. The muscles supply the power for moving 
 the bones, and the joints act as fulcrums or points of support. 
 The weight of the limb, the weight to be lifted, or the force to 
 overcome, is the resistance. 
 
 74. Levers in the Body. In mechanics three classes of levers are 
 described, according to the relative position of the power, the fulcrum, 
 and the resistance. All the movements of the bones can be referred 
 to one or another of these three classes. 
 
 Levers of the first class are those in which the fulcrum is between 
 the power and the 
 weight. The crow- 
 bar, when used to 
 lift a weight at one 
 end by the applica- 
 tion of power at the 
 other, with a block 
 as a fulcrum, is a 
 familiar example of 
 this class. There 
 are several exam- 
 ples of this in the 
 human body. The 
 head supported on the atlas is one. The joint between the atlas and 
 the skull is the fulcrum, the weight of the head is the resistance. 
 The power is behind, where the muscles from the neck are attached 
 to the back of the skull. The object of this arrangement is to keep 
 the head steady and balanced on the spinal column, and to move it 
 backward and forward. 
 
 Levers of the second class are those in which the weight is between 
 the fulcrum and the power. A familiar example is the crowbar when 
 used for lifting a weight while one end rests on the ground. This class 
 of levers is not common in the body. Standing on tiptoe is, however, 
 an example. Here the toes in contact with the ground are the fulcrum, 
 the power is the action of the muscles of the calf, and between these is 
 the weight of the body transmitted down the bones of the leg to the foot. 
 
 FIG. 35. Showing how the Bones of the Arm serve as 
 Levers. P, power; W, weight; F, fulcrum. 
 
68 PRACTICAL PHYSIOLOGY. 
 
 Levers of the third class are those in which the power is applied 
 at a point between the fulcrum and weight. A familiar example is 
 where a workman raises a ladder against a wall. This class of levers 
 is common in the body. In bending the forearm on the arm, familiarly 
 known as " trying your muscle," the power is supplied by the biceps 
 muscle attached to the radius, the fulcrum is the elbow joint at one 
 end of the lever, and the resistance is the weight of the forearm at 
 the other end. 
 
 Experiment 22. To illustrate how the muscles use the bones as levers. First, 
 practice with a ruler, blackboard pointer, or any other convenient object, 
 illustrating the different kinds of levers until the principles are familiar. 
 Next, illustrate these principles on the person, by making use of convenient 
 muscles. Thus, lift a book on the toes, by the fingers, on the back of the 
 hand, by the mouth, and in other ways. 
 
 These experiments, showing how the bones serve as levers, may be 
 multiplied and varied as circumstances may require. 
 
 75. The Erect Position. The erect position is peculiar to 
 man. No other animal naturally assumes it or is able to keep 
 it long. It is the result of a somewhat complex arrangement 
 of muscles which balance each other, some pulling backwards 
 and some forwards. Although the whole skeleton is formed 
 with reference to the erect position, yet this attitude is slowly 
 learned in infancy. 
 
 In the erect position the center of gravity lies in the joint 
 between the sacrum and the last lumbar vertebra. A line 
 dropped from this point would fall between the feet, just in 
 front of the ankle joints. We rarely stand with the feet close 
 together, because that basis of support is too small for a firm 
 position. Hence, in all efforts requiring vigorous muscular 
 movements the feet are kept more or less apart to enlarge the 
 basis of support. 
 
 Now, on account of the large number and flexibility of the 
 joints, the body could not be kept in an upright position with- 
 out the cooperation of certain groups of muscles. The mus- 
 cles of the calf of the leg, acting on the thigh bone, above the 
 
THE MUSCLES. 
 
 6 9 
 
 knee, keep the body from falling 
 forward, while another set in front 
 of the thigh helps hold the leg 
 straight. These thigh muscles 
 also tend to pull the trunk for- 
 ward, but in turn are balanced by 
 the powerful muscles of the lower 
 back, which help keep the body 
 straight and braced. 
 
 The head is kept balanced on 
 the neck partly by the central 
 position of the joint between the 
 atlas and axis, and partly by 
 means of strong muscles. Thus, 
 the combined action of these and 
 other muscles serves to balance 
 the body and keep it erect. A 
 blow on the head, or a sudden 
 shock to the nervous system, 
 causes the body to fall in a heap, 
 because the brain has for the time 
 lost its power over the muscles, 
 and they cease to contract. 
 
 76. Important Muscles. 
 
 There are scores of tiny muscles 
 about the head, face, and eyes, 
 which, by their alternate contrac- 
 tions and relaxations, impart to 
 the countenance those expres- 
 sions which reflect the feelings 
 and passions of the individual. 
 Two important muscles, the tem- 
 poral, near the temples, and the 
 masseter, or chewing muscle, are 
 
 B I 
 
 FIG. 36. Diagram showing the Action 
 of the Chief Muscles which keep the 
 Body Erect. (The arrows indicate 
 the direction in which these muscles 
 act, the feet serving as a fixed basis.) 
 [After Huxley.] 
 
 Muscles -which tend to keep the body 
 
 from falling forward. 
 A, muscles of the calf; B, of the back of 
 the thigh; C, of the spinal column. 
 
 Muscles which tend to keep the body 
 
 from falling backward. 
 D, muscles of the front of the leg; E, of 
 the front of the thigh ; F, of the front of 
 the abdomen ; G , of the front of the neck 
 
7O PRACTICAL PHYSIOLOGY. 
 
 the chief agents in moving the lower jaw. They are very large 
 in the lion, tiger, and other flesh-eating animals. On the inner 
 side of each cheek is the buccinator, or trumpeter's muscle, 
 which is largely developed in those who play on wind instru- 
 ments. Easily seen and felt under the skin in thin persons, 
 on turning the head to one side, is the sterno-cleido-mastoid 
 muscle, which passes obliquely down on each side of the 
 neck to the collar bone prominent in sculpture and 
 painting. 
 
 The chest is supplied with numerous muscles which move 
 the ribs up and down in the act of breathing. A great, fan- 
 shaped muscle, called the pectoralis major, lies on the chest. 
 It extends from the chest to the arm and helps draw the arm 
 inward and forward. The arm is raised from the side by a 
 large triangular muscle on the shoulder, the deltoid, so called 
 from its resemblance to the Greek letter delta, A. The biceps, 
 or two-headed muscle, forms a large part of the fleshy mass in 
 front of the arm. Its use is to bend the forearm on the arm, 
 an act familiarly known as " trying your muscle." Its direct 
 antagonist is the three-headed muscle called the triceps. It 
 forms the fleshy mass on the back of the arm, its use being 
 to draw the flexed forearm into a right line. 
 
 On the back and outside of the forearm are the extensors, 
 which straighten the wrist, the hand, and the fingers. On the 
 front and inside of the forearm are the flexors, which bend the 
 hand, the wrist, and the fingers. If these muscles are worked 
 vigorously, their tendons can be readily seen and felt under 
 the skin. At the back of the shoulder a large, spread-out 
 muscle passes upward from the back to the humerus. From 
 its wide expanse on the back it is known as the latissimus 
 dor si (broadest of the back). When in action it draws the 
 arm downward and backward, or, if one hangs by the hands, it 
 helps to raise the body. It is familiarly known as the " climb- 
 ing muscle." 
 
THE MUSCLES. 
 
 Passing to the lower extremity, the thigh muscles are the 
 largest and the most powerful in the body. In front a great, 
 
 FIG. 37. A Few of the Important Muscles of the Back. 
 
 four-headed muscle, quadriceps extensor, unites into a single 
 tendon in which the knee-cap is set, and serves to straighten 
 
/2 PRACTICAL PHYSIOLOGY. 
 
 the knee, or when rising from a sitting posture helps elevate 
 the body. On the back of the thigh are several large muscles 
 which bend the knee, and whose tendons, known as the " ham- 
 strings," are readily felt just behind the knee. On the back 
 of the leg the most important muscles, forming what is known 
 as the calf, are the gastrocnemius and the soleus. The first 
 forms the largest part of the calf. The soleus, so named from 
 resembling a sole-fish, is a muscle of broad, flattened shape, 
 lying beneath the gastrocnemius. The tendons of these two 
 muscles unite to form the tendon of Achilles, as that hero is 
 said to have been invulnerable except at this point. The 
 muscles of the calf have great power, and are constantly called 
 into use in walking, cycling, dancing, and leaping. 
 
 77. The Effect of Alcoholic Drinks upon the Muscles. 
 It is found that a man can do more work without alcohol 
 than with it. After taking it there may be a momentary 
 increase of activity, but this lasts only ten or fifteen minutes 
 at the most. It is followed by a rapid reduction of power that 
 more than outweighs the momentary gain, while the quality 
 of the work is decidedly impaired from the time the alcohol 
 is taken. 
 
 Even in the case of hard work that must be speedily done, 
 alcohol does not help, but hinders its execution. The tired 
 man who does not understand the effects of alcohol often 
 supposes that it increases his strength, when in fact it only 
 deadens his sense of fatigue by paralyzing his nerves. When 
 put to the test he is surprised at his self-deception. 
 
 Full intoxication produces, by its peculiar depression of the 
 brain and nervous system, an artificial and temporary paralysis 
 of the muscles, as is obvious in the pitifully helpless condition 
 of a man fully intoxicated. But even partial approach to in- 
 toxication involves its proportionate impairment of nervous 
 integrity, and therefore just so much diminution of muscular 
 
THE MUSCLES. 73 
 
 force. All athletes recognize this fact, as while training for a 
 contest, rigid abstinence is the rule, both from liquors and 
 tobacco. This muscular weakness is shown also in the un- 
 steady hand, the trembling limbs of the inebriate, his thick 
 speech, wandering eye, and lolling head. 
 
 78. Destructive Effect of Alcoholic Liquors upon Mus- 
 cular Tissue. Alcoholic liquors retard the natural chemical 
 changes so essential to good health, by which is meant the 
 oxidation of the nutritious elements of food. Careful demon- 
 stration has proved also that the amount of carbon dioxid 
 escaping from the lungs of intoxicated persons is from thirty 
 to fifty per cent less than normal. This shut-in carbon stifles 
 the nervous energy, and cuts off the power that controls mus- 
 cular force. This lost force is in close ratio to the retained 
 carbon : so much perverted chemical change, so much loss of 
 muscular power. Not only the strength but the fine delicacy 
 of muscular action is lost, the power of nice control of the 
 hand and fingers, as in neat penmanship, or the use of musical 
 instruments. 
 
 To this perverted chemical action is also due the fatty 
 degeneration so common in inebriates, affecting the muscles, 
 the heart, and the liver. These organs are encroached upon 
 by globules of fat (a hydrocarbon), which, while very good in 
 
 NOTE. It was proposed during the Civil War to give each soldier in a certain 
 army one gill of whiskey a day, because of great hardship and exposure. The emi- 
 nent surgeon, Dr. Frank H. Hamilton of New York, thus expressed his views of 
 the question : " It is earnestly desired that no such experiment will ever be repeated 
 in the armies of the United States. In our own mind, the conviction is established, 
 by the experience and observation of a life, that the regular routine employment of 
 alcoholic stimulants by man in health is never, under any circumstances, useful. We 
 make no exceptions in favor of cold or heat or rain." 
 
 " It seems to me to follow from these Arctic experiences that the regular use of 
 spirits, even in moderation, under conditions of great physical hardship, continued 
 and exhausting labor, or exposure to severe cold cannot be too strongly deprecated." 
 A. W. GREELY, retired Brigadier-General, U. S. A., and formerly leader of the 
 Greely Expedition. 
 
74 
 
 PRACTICAL PHYSIOLOGY. 
 
 their proper place and quantity, become a source of disorder 
 and even of death when they abnormally invade vital structures. 
 Other poisons, as phosphorus, produce this fatty decay more 
 rapidly; but alcohol causes it in a much more general way. 
 
 FIG. 38. Principal Muscles on the Left Side ot Neck. 
 
 A, buccinator; B, masseter; C, depressor anguli oris; D, anterior portion of the 
 digastric; E, mylo-hyoid; F, tendon of the digastric; G, sterno-hyoid ; H, sterno- 
 thyroid; K, omo-hyoid ; L, sternal origin of sterno-cleido-mastoid muscle; M, 
 superior fibers of deltoid; N, posterior scalenus; O, clavicular origin of sterno- 
 cleido-mastoid; P, sterno-cleido-mastoid; R, trapezius; S, anterior constrictor; 
 T, splenius capitis; V, stylo-hyoid ; W, posterior portion of the digastric; X, fasci- 
 culi of ear muscles ; Z, occipital. 
 
 This is proved by the microscope, which plainly shows the 
 condition mentioned, and the difference between the healthy 
 tissues and those thus diseased. 
 
THE MUSCLES. 75 
 
 79. Effect of Tobacco on the Muscles. That other promi- 
 nent narcotic, tobacco, impairs the energy of the muscles 
 somewhat as alcohol does, by its paralyzing effect upon the 
 nervous system. As all muscular action depends on the 
 integrity of the nervous system, whatever lays its deadening 
 hand upon that, saps the vigor and growth of the entire frame, 
 dwarfs the body, and retards mental development. This 
 applies especially to the young, in the growing age between 
 twelve or fourteen and twenty, the very time when the healthy 
 body is being well knit and compacted. 
 
 Hence many public schools, as well as our national naval 
 and military academies, rigidly prohibit the use of tobacco by 
 their pupils. So also young men in athletic training are strictly 
 forbidden to use it. 1 This loss of muscular vigor is shown by 
 the unsteady condition of the muscles, the trembling hand, and 
 the inability to do with precision and accuracy any fine work, 
 as in drawing or nice penmanship. 
 
 ADDITIONAL EXPERIMENTS. 
 
 Experiment 23. To examine the minute structure of voluntary muscular 
 fiber. Tease, with two needles set in small handles, a bit of raw, lean meat, 
 on a slip of glass, in a little water. Continue until the pieces are almost 
 invisible to the naked eye. 
 
 Experiment 24. Place a clean, dry cover-glass of about the width of the 
 slip, over the water containing the torn fragments. Absorb the excess of 
 moisture at the edge of the cover, by pressing a bit of blotting-paper against 
 it for a moment. Place it on the stage of a microscope and examine with 
 highest obtainable power, by light reflected upward from the mirror beneath 
 the stage. Note the apparent size of the finest fibers ; the striation of the 
 fibers, or their markings, consisting of alternate dim and bright cross bands. 
 Note the arrangement of the fibers in bundles, each thread running parallel 
 with its neighbor. 
 
 1 " Smoking among students or men training for contests is a mistake. It not only 
 affects the wind, but relaxes the nerves in a way to make them less vigorous for the 
 coming contest. It shows its results at once, and when the athlete is trying to do his 
 best to win he will do well to avoid it." JOSEPH HAMBLEN SEARS, Harvard Coach, 
 and Ex-Captain of the Harvard Football Team, Article in In Sickness and in Health. 
 
76 PRACTICAL PHYSIOLOGY. 
 
 experiment 25. To examine the minute structure of invohintary mus- 
 cular fiber, a tendon, or a ligament. Obtain a very small portion of the 
 muscular coat of a cow's or a pig's stomach. Put it to soak in a solution of 
 one dram of bichromate of potash in a pint of water. Take out a morsel 
 on the slip of glass, and tease as directed for the voluntary muscle. Exam- 
 ine with a high power of the microscope and note : (i) the isolated cells, 
 long and spindle-shaped, that they are much flattened; (2) the arrangement 
 of the cells, or fibers, in sheets, or layers, from the torn ends of which they 
 project like palisades. 
 
 Experiment 26. Tease out a small portion of the tendon or ligament in 
 water, and examine with a glass of high power. Note the large fibers in the 
 ligament, which branch and interlace. 
 
 Experiment 27. With the head slightly bent forwards, grasp between 
 the fingers of the right hand the edge of the left sterno-cleido-mastoid, just 
 above the collar bone. Raise the head and turn it from left to right, and 
 the action of this important muscle is readily seen and felt. In some per- 
 sons it stands out in bold relief. 
 
 Experiment 28. The tendons which bound the space (popliteal) behind 
 the knee can be distinctly felt when the muscles which bend the knee are in 
 action. On the outer side note the tendons of the biceps of the leg, running 
 down to the head of the fibula. On the inside we feel three tendons of 
 important muscles on the back of the thigh which flex the leg upon the 
 thigh. 
 
 Experiment 29. To sho%v the ligamentous action of the muscles. Standing 
 with the back fixed against a wall to steady the pelvis, the knee can be 
 flexed so as to almost touch the abdomen. Take the same position and 
 keep the knee rigid. .When the heel has been but slightly raised a sharp 
 pain in the back of the thigh follows any effort to carry it higher. Flexion 
 of the leg to a right angle, increases the distance from the lines of insertion 
 on the pelvic bones to the tuberosities of the tibia by two or three inches 
 an amount of stretching these muscle cannot undergo. Hence the knee 
 must be flexed in flexion of the hip. 
 
 Experiment 30. A similar experiment may be tried at the wrist. Flex 
 the wrist with the fingers extended, and again with the fingers in the fist. 
 The first movement can be carried to 90, the second only to 30, or in 
 some persons up to 60. Making a fist had already stretched the extensor 
 muscles of the arm, and they can be stretched but little farther. Hence, 
 needless pain will be avoided by working a stiff wrist with the parts loose, 
 or the fingers extended, and not with a clenched fist. 
 
REVIEW ANALYSIS: IMPORTANT MUSCLES. 
 
 LOCATION. 
 
 HEAD 
 
 AND 
 
 NECK. 
 
 TRUNK. 
 
 UPPER 
 LIMBS. 
 
 LOWER 
 LIMBS. 
 
 NAME. 
 
 Occipito-frontalis . . 
 
 Orbicularis palpebrarum 
 Levator palpebrarum . 
 Temporal .... 
 Masseter . 
 
 Sterno-cleido -mastoid 
 
 Platysma myoides . 
 
 Pectoralis major . . 
 
 Pectoralis minor . . 
 
 Latissimus dorsi . . 
 
 Serratus magnus . . 
 
 Trapezius . . . . 
 
 Rhomboideus . . . 
 
 Intercostals . . . . 
 
 External oblique . . 
 
 Internal oblique . . 
 
 Rectus abdominis . 
 
 Deltoid .... 
 
 Biceps .... 
 Triceps .... 
 Brachialis anticus 
 Supinator longus . 
 Flexor carpi radialis 
 Flexor carpi ulnaris 
 
 Gluteus maximus . 
 Adductors of thigh 
 Sartorius . . . 
 Rectus femoris . . 
 Vastus externus . 
 Vastus internus . 
 Biceps femoris . . 
 
 Gracilis . 
 
 Tibialis anticus 
 Peroneus longus 
 Gastrocnemius . 
 Soleus 
 
 CHIEF FUNCTION. 
 
 moves scalp and raises eye- 
 brow. 
 
 shuts the eyes, 
 opens the eyes. 
 
 raise the lower jaw. 
 
 j depresses head upon neck and 
 I neck upon chest, 
 depresses lower jaw and lower 
 lip. 
 
 j draws arm across front of 
 ( chest. 
 
 depresses point of shoulder. 
 
 draws arm downwards and 
 backwards. 
 
 assists in raising ribs, 
 backward movements of head 
 
 and shoulder, 
 raise and depress the ribs, 
 various forward movements 
 
 of trunk, 
 compresses abdominal viscera 
 
 and acts upon pelvis. 
 
 carries arm outwards and up- 
 wards. 
 
 flexes elbow and raises arm. 
 extends the forearm, 
 flexor of elbow, 
 flexes the forearm. 
 
 flexors of wrist. 
 
 adducts the thigh. 
 
 draw the leg inwards. 
 
 crosses the legs. 
 
 flexes the thigh. 
 
 extensor of leg. 
 
 extensor of leg upon thigh. 
 
 flexes leg upon thigh. 
 
 flexes the leg and adducts 
 
 thigh. 
 
 draws up inner border of foot, 
 raises outer edge of foot, 
 keep the body erect, and aid 
 
 in walking and running. 
 
CHAPTER IV. 
 PHYSICAL EXERCISE. 
 
 80. Importance of Bodily Exercise. Nothing is so essen- 
 tial to success in life as sound physical health. It enables 
 us to work with energy and comfort, and better to endure 
 unusual physical and mental strains. While others suffer the 
 penalties of feebleness, a lower standard of functional activi- 
 ties, and premature decay, the fortunate possessor of a sound 
 mind in a sound body is better prepared, with proper applica- 
 tion, to endure the hardships and win the triumphs of life. 1 
 
 This element of physical capacity is as necessary to a useful 
 and energetic life, as are mental endowment and intellectual 
 acquirement. Instinct impels us to seek health and pleasure 
 in muscular exercise. A healthy and vigorous child is never 
 still except during sleep. The restless limbs and muscles of 
 school children pent up for several hours, feel the need of 
 movement, as a hungry man craves food. This natural desire 
 for exercise, although too often overlooked, is really one of the 
 necessities of life. One must be in ill health or of an imper- 
 fect nature, when he ceases to feel this impulse. Indeed, 
 motion within proper bounds is essential to the full develop- 
 ment and perfect maintenance of the bodily health. Unlike 
 
 1 " There is no profession, there is no calling or occupation in which men can be 
 engaged, there is no position in life, no state in which a man can be placed, in 
 which a fairly developed frame will not be valuable to him ; there are many of these, 
 even the most purely and highly intellectual, in which it is essential to success 
 essential simply as a means, material, but none the less imperative, to enable the 
 mind to do its work. Year by year, almost day by day, we see men (and women), 
 falter and fail in the midst of their labors ; . . . and all for want of a little bodily 
 stamina a little bodily power and bodily capacity for the endurance of fatigue, or 
 protracted unrest, or anxiety, or grief." MACLAREN'S Physical Education. 
 
PHYSICAL EXERCISE. 79 
 
 other machines, the human body becomes within reasonable 
 limits, stronger and more capable the more it is used. 
 
 As our tenure of life at best is short, it is our duty to 
 strive to live as free as possible from bodily ills. It is, there- 
 fore, of paramount importance to rightly exercise every part 
 of the body, and this without undue effort or injurious strain. 
 
 Strictly speaking, physical exercise refers to the functional 
 activity of each and every tissue, and properly includes the 
 regulation of the functions and movements of the entire body. 
 The word exercise, however, is used usually in a narrower sense 
 as applied to those movements that are effected by the contrac- 
 tion of the voluntary muscles. 
 
 Brief reference will be made in this chapter only to such 
 natural and systematic physical training as should enter into the 
 life of every healthy person. 
 
 81. Muscular Activity. The body, as we have learned, 
 is built up of certain elementary tissues which are combined 
 to make bones, muscles, nerves, and other structures. The 
 tissues, in turn, are made up of countless minute cells, each 
 of which has its birth, lives its brief moment to do its work in 
 the animal economy, is separated from the tissue of which it 
 was a part, and is in due time eliminated by the organs of ex- 
 cretion, the lungs, the skin, or the kidneys. Thus there is 
 a continuous process of growth, of decay, and removal, among 
 the individual cells of each tissue. 
 
 NOTE. The Incessant Changes in Muscular Tissue. " In every tiny block 
 of muscle there is a part which is really alive, there are parts which are becoming alive, 
 there are parts which have been alive, and are now dying or dead ; there is an 
 upward rush from the lifeless to the living, a downward rush from the living to the 
 dead. This is always going on, whether the muscle be quiet and at rest, or whether 
 it be active and moving, some of the capital of living material is being spent, changed 
 into dead waste ; some of the new food is always being raised into living capital. 
 But when the muscle is called upon to do work, when it is put into movement, the 
 expenditure is quickened, there is a run upon the living capital, the greater, the more 
 urgent the call for action." PROFESSOR MICHAEL FOSTER. 
 
8o 
 
 PRACTICAL PHYSIOLOGY. 
 
 These ceaseless processes are greatly modified by the activity 
 of the bodily functions. Every movement of a muscle, for 
 instance, involves change in its component cells. And since 
 the loss of every atom of the body is in direct relation to its 
 activity, a second process is necessary to repair this constant 
 
 waste; else the body would 
 rapidly diminish in size 
 and strength, and life itself 
 would soon end. This 
 process of repair is accom- 
 plished, as we shall learn 
 in Chapters VI. and VII. , 
 by the organs of nutrition, 
 which convert the food 
 into blood. 
 
 82. Effect of Exercise 
 upon the Muscles. Sys- 
 tematic exercise influences 
 the growth and structure 
 of the muscles of the body 
 in a manner somewhat re- 
 markable. Muscular exercise makes muscular tissue ; from 
 the lack of it, muscles become soft and wasted. Muscles 
 properly exercised not only increase in size, both as a whole 
 and in their individual structure, but afe better enabled to get 
 rid of material which tends to hamper their movements. 
 Thus muscular exercise helps to remove any needless ac- 
 cumulation of fat, as well as useless waste matters, which may 
 exist in the tissues. As fat forms no permanent structural part 
 of the organism, its removal is, within limits, effected with no 
 inconvenience. 
 
 Muscular strength provides the joints with more powerful 
 ligaments and better developed bony parts. After long con- 
 
 FIG. 39. Showing how the Muscles of the 
 Back may be developed by a Moderate 
 Amount of Dumb-Bell Exercise at Home. 
 (From a photograph.) 
 
PHYSICAL EXERCISE. 
 
 8l 
 
 finement to the bed from disease, the joints have wasted liga- 
 ments, thin cartilages, and the bones are of smaller proportions. 
 Duly exercised muscles influence the size of the bones upon 
 which they act. Thus the bones of a well-developed man are 
 stronger, firmer, and larger than those of a feeble person. 
 
 He who has been physically well trained, has both a more 
 complete and a more intelligent use of his muscles. He has 
 acquired the art of causing his mus- 
 cles to act in concert. Movements 
 once difficult are now carried on with 
 ease. The power of coordination is 
 increased, so that a desired end is 
 attained with the least amount of 
 physical force and nervous energy. 
 In learning to row, play baseball, 
 ride the bicycle, or in any other exer- 
 cises, the beginner makes his move- 
 ments in a stiff and awkward manner. 
 He will use and waste more muscular 
 force in playing one game of ball, or 
 in riding a mile on his wheel, than an 
 expert would in doing ten times the 
 work. He has not yet learned to 
 balance one set of muscles against 
 their antagonists. 
 
 In time, however, acts which were 
 
 FIG. 40. The Standard Spe- 
 cial Chest Weight. 
 
 A convenient machine by means 
 
 first done only with effort and by a O f which ail the muscles of the 
 
 body may be easily and pleas- 
 antly exercised with sufficient 
 variations in the movements to 
 relieve it of monotony. 
 A space 6 ft. wide, 6 ft. deep, and 
 
 is developed in the spinal cord and 
 the muscular centers 
 
 conscious will, become automatic. 
 The will ceases to concern itself. By 
 what is called reflex action, memory 
 
 7 ft. high nearly in front of the 
 machine is required for exercise." 
 
 (sec. 273). 
 
 There is thus a great saving of actual brain work, and one 
 important cause of fatigue is removed. 
 
82 PRACTICAL PHYSIOLOGY. 
 
 83. Effect of Exercise on Important Organs. The impor- 
 tance of regular exercise is best understood by noting its effects 
 upon the principal organs of the body. As the action of the 
 heart is increased both in force and frequency during exercise, 
 the flow of blood throughout the body is augmented. This 
 results from the force of the muscular contractions which play 
 their part in pressing the blood in the veins onward towards the 
 heart. Exercise also induces a more vigorous respiration, and 
 under increased breathing efforts the lung capacity is increased 
 and the size of the chest is enlarged. The amount of air inspired 
 and expired in a given time is much larger than if the body 
 were at rest. The blood is thus supplied with a much larger 
 amount of oxygen from the air inhaled, and gives off to the 
 air a corresponding excess of carbon dioxid and water. 
 
 Again, exercise stimulates and strengthens the organs of 
 digestion. The appetite is improved, as is especially noted 
 after exercise in the open air. The digestion is more complete, 
 absorption becomes more rapid, the peristaltic movements of 
 the bowels are promoted, and the circulation through the liver 
 is more vigorous. More food is taken to supply the force 
 necessary for the maintenance of the mechanical movements. 
 Ample exercise also checks the tendency towards a torpid 
 circulation in the larger digestive organs, as the stomach and 
 the liver, so common with those who eat heartily, but lead 
 sedentary lives. In short, exercise may be regarded as a great 
 regulator of nutrition. 
 
 Exercise increases the flow of blood through the small vessels 
 of the skin, and thus increases the radiation of heat from the 
 surface. If the exercise be vigorous and the weather hot, a 
 profuse sweat ensues, the rapid evaporation of which cools the 
 body. The skin is thus a most important regulator of the 
 bodily temperature, and prevents any rise above the normal 
 which would otherwise result from vigorous exercise. (See 
 sees. 226 and 241). 
 
PHYSICAL EXERCISE. 
 
 84. Effect of Exercise upon the Personal Appearance. Judicious 
 and systematic exercise, if moderately employed, soon gives a more 
 upright and symmetrical figure, and an easier and more graceful car- 
 riage. Rounded shoulders become 
 square, the awkward gait disap- 
 pears, and there is seen a graceful 
 poise to the head and a bearing 
 of the body which mark those 
 whose muscles have been well 
 trained. A perfectly formed skele- 
 ton and well-developed muscles 
 give the graceful contour and per- 
 fect outline to the human body. 
 The lean, soft limbs of those who 
 have never had any physical edu- 
 cation, often look as if they be- 
 longed to persons recovering from 
 sickness. The effects of sound 
 physical exercise are well exhibited 
 in the aspect of the neck, shoul- 
 ders, and chest of one who has 
 been well trained. This is notice- 
 able in gymnasts and others who 
 
 FIG. 41. Young Woman practicing at 
 Home with the " Whitely Exerciser." 
 (From a photograph.) 
 
 practice upon the horizontal bar, 
 with chest weights, dumb-bells, 
 and other apparatus which de- 
 velop more especially the muscles of the upper half of the trunk. 
 Exercise improves the condition of the tissues generally. They 
 become more elastic, and in all respects sounder. The skin becomes 
 firm, clear, and wholesome. Hence, every part of the surface of 
 the body rapidly takes on a change in contour, and soon assumes 
 that appearance of vigor and soundness which marks those of firm 
 physical condition. The delicate, ruddy aspect of the complexion, 
 the swing about the body and the bearing of the head and shoulders, 
 of young women whose physical training has been efficient, are in 
 marked contrast with those characteristics in persons whose educa- 
 tion in this respect has been neglected. 
 
84 PRACTICAL PHYSIOLOGY. 
 
 85. Effect of Unsuitable or Excessive Exercise. But 
 
 exercise, like everything else which contributes to our welfare, 
 may be carried to excess. The words excessive and unsuitable, 
 when applied to muscular exertion, are relative terms, and 
 apply to the individual rather than to amount of work done. 
 Thus what may be excessive for one person, might be suitable 
 and beneficial to another. Then the condition of the individual, 
 rather than the character of the muscular work, is always a 
 most important factor. 
 
 Breathlessness is, perhaps, the most common effect of undue 
 exertion. Let a middle-aged person, who is out of practice, 
 run a certain distance, and he is soon troubled with his breath- 
 ing. The respirations become irregular, and there is a sense 
 of oppression in his chest. He pants, and his strength gives 
 out. His chest, and not his legs, has failed him. He is said 
 to be " out of breath." He might have practiced dumb-bells 
 or rowed for some time without inconvenience. 
 
 The heart is often overstrained, and at times has been 
 ruptured during violent exertion, as in lifting an immense 
 weight. The various forms of heart-disease are common with 
 those whose occupations involve severe muscular effort, as pro- 
 fessional athletes and oarsmen. Haemorrhages of various kinds, 
 especially from the lungs, or rupture of blood-vessels in the 
 brain, are not uncommon results of over-exertion. 
 
 Excessive repetition of muscular movements may lead to per- 
 manent contractions of the parts involved. Thus sailors, 
 mechanics, and others frequently develop a rigidity of the 
 tendons of the hand which prevents the full extension of the 
 fingers. So stenographers, telegraphers and writers occasionally 
 suffer from permanent contractions of certain muscles of the 
 arm, known as writer's cramp, due to their excessive use. But 
 the accidents which now and then may result from severe 
 physical exertion, should discourage no one from securing the 
 benefits which accrue from moderate and reasonable exercise. 
 
PHYSICAL EXERCISE. 85 
 
 86. Muscular Fatigue. We all know how tiresome it is to 
 hold the arm outstretched horizontally even for a few moments. 
 A single muscle, the deltoid, in this case does most of the 
 work. Even in a vigorous man, this muscle can act no longer 
 than four to six minutes before the arm drops helpless. We 
 may prolong the period by a strong effort of the will, but a 
 
 FIG. 42. A Well-Equipped Gymnasium. 
 (From a photograph.) 
 
 time soon comes when by no possible effort are we able to hold 
 out the arm. The muscle is said to be fatigued. It has by no 
 means lost its contractile power, for if we apply a strong electric 
 stimulus to it, the fatigue seems to disappear. Thus we see 
 the functional power of a muscle has a definite limit, and in 
 fatigue that limit is reached. 
 
 The strength of the muscle, its physical condition, the work 
 it has done, and the mental condition of the individual, all 
 
86 PRACTICAL PHYSIOLOGY. 
 
 modify the state of fatigue. In those difficult acts which 
 involve a special effort of the will, the matter of nerve exhaus- 
 tion is largely concerned. Thus, the incessant movements in 
 St. Vitus' dance result in comparatively little fatigue, because 
 there is no association of the brain with the muscular action. 
 If a strong man should attempt to perform voluntarily the 
 same movements, he would soon have to rest. None of the 
 movements which are performed independently of the will, as 
 the heart-beats and breathing movements, ever involve the sen- 
 sation of fatigue. As a result of fatigue the normal irritability 
 of muscular tissue becomes weakened, and its force of contract- 
 tion is lessened. There is, also, often noticed in fatigue a 
 peculiar tremor of the muscles, rendering their movements 
 uncertain. The stiffness of the muscles which comes on during 
 severe exercise, or the day after, are familiar results of fatigue. 
 
 This sense of fatigue should put us on guard against danger. 
 It is a kind of regulator which serves in the ordinary actions 
 of life to warn us not to exceed the limits of useful exercise. 
 Fatigue summons us to rest long before all the force of the 
 motor organs has been expended, just as the sensation of 
 hunger warns us that we need food, long before the body has 
 become weak from the lack of nourishment. 
 
 We should never forget that it is highly essential to maintain 
 an unused reserve of power, just as a cautious merchant always 
 keeps at the bank an unexpended balance of money. If he 
 overspends his money he is bankrupt, and the person who over- 
 spends his strength is for the time physically bankrupt. In each 
 case the process of recovery is slow and painful. 
 
 87. Rest for the Muscles. Rest is necessary for the 
 tissues, that they may repair the losses sustained by work; 
 that is, a period of rest must alternate with a period of activity. 
 Even the heart, beating ceaselessly, has its periods of absolute 
 rest to alternate with those of work. A steam-engine is always 
 
PHYSICAL EXERCISE. / 
 
 slowly, but surely, losing its fitness for work. At last it stops 
 from the need of repair. Unlike the engine, the body is con- 
 stantly renewing itself and undergoing continual repair. Were 
 it not for this power to repair and renew its various tissues, the 
 body would soon be worn out. 
 
 This repair is really a renovation of the structure. Rest and 
 work are relative terms, directly opposed to each other. Work 
 quickens the pulse and the respiration, while rest slows both. 
 During sleep the voluntary muscles are relaxed, and those of 
 organic life work with less energy. The pulse and the respira- 
 tion are less frequent, and the temperature lower than when 
 awake. Hence sleep, "tired Nature's sweet restorer," may be 
 regarded as a complete rest. 
 
 The periods of rest should vary with the kind of exercise. 
 Thus exercise which produces breathlessness requires frequent 
 but short rests. The trained runner, finding his respiration 
 embarrassed, stops a moment to regain his breath. Exercises 
 of endurance cause fatigue less quickly than those of speed, but 
 require longer rest. Thus a man not used to long distances 
 may walk a number of hours without stopping, but while fatigue 
 is slow to result, it is also slow to disappear. Hence a lengthy 
 period of rest is necessary before he is able to renew his 
 journey. 
 
 88. Amount of Physical Exercise Required. The amount 
 
 of physical exercise that can be safely performed by each per- 
 son, is a most important and practical question. No rule can 
 be laid down, for what one person bears well, may prove very 
 injurious to another. To a certain extent, each must be guided 
 by his own judgment. If, after taking exercise, we feel fatigued 
 and irritable, are subject to headache and sleeplessness, or find 
 it difficult to apply the mind to its work, it is plain that we have 
 been taxing our strength unduly, and the warnings should be 
 heeded. 
 
88 
 
 PRACTICAL PHYSIOLOGY. 
 
 Age is an important factor in the problem, as a young man 
 may do with ease and safety, what might be injurious to an 
 older person. In youth, when the body is making its most active 
 development, the judicious use of games, sports, and gymnastics 
 is most beneficial. In advanced life, both the power and the 
 
 inclination for exercise 
 fail, but even then effort 
 should be made to take 
 a certain reasonable 
 amount of exercise. 
 
 Abundant evidence 
 shows that physical 
 development is most 
 active from thirteen to 
 seventeen years of age ; 
 this manifests itself 
 clearly by increase in 
 weight. Hence this 
 period of life is of great 
 consequence. If at this 
 
 FIG. 43. Student exercising in the School Gym- 
 nasium on the Rowing Machine, 
 photograph.) 
 
 (From a age a boy or girl is sub- 
 jected to undue physi- 
 cal strain, the development may suffer, the growth be retarded, 
 and the foundation laid for future ill health. 
 
 The proper amount of exercise must vary greatly with circum- 
 stances. It may be laid down as a fairly safe rule, that a 
 person of average height and weight, engaged in study or in 
 any indoor or sedentary occupation, should take an amount of 
 exercise equivalent to walking five or six miles a day. Growing 
 children, as a rule, take more exercise than this, while most men 
 working indoors take far less, and many women take less 
 exercise than men. Exercise may be varied in many ways, 
 the more the better ; but for the most part it should always be 
 taken in the open air. 
 
PHYSICAL EXERCISE. 89 
 
 89. Time for Exercise. It is not prudent to do hard work 
 or take severe exercise, just before or just after a full meal. The 
 best time is one or two hours after a meal. Vigorous exercise 
 while the stomach is busily digesting food, may prove injurious, 
 and is apt to result sooner or later in dyspepsia. On the other 
 hand, severe exercise should not be taken on an empty stomach. 
 Those who do much work or study before breakfast, should first 
 take a light lunch, just enough to prevent any faint feeling. 
 With this precaution, there is no better time for moderate exer- 
 cise than the early morning. 
 
 In the case of children, physical exercises should not be 
 undertaken when they are overtired or hungry. Neither is it 
 judicious for adults to take vigorous exercise in the evening, 
 after a long and arduous day's work. 
 
 90. Walking, Running, and Jumping. Walking is gener- 
 ally regarded as the simplest and most convenient mode of tak- 
 ing exercise. Man is essentially a walking animal. When taken 
 with a special object in view, it is the best and most pleasant of 
 all physical activities. It is suited for individuals of all ages 
 and occupations, and for residents of every climate. The child, 
 the athlete, and the aged are all able to indulge in this simple 
 and effective means of keeping the body in health. 
 
 In walking, the muscles of the entire body are brought into 
 action, and the movements of breathing and the circulation of 
 the blood are increased. The body should be erect, the chest 
 thrown out, the head and shoulders held back, and the stride 
 long and elastic. It is an excellent custom to add to the use- 
 fulness of this fine exercise, by deep, voluntary inhalations of 
 pure air. 
 
 Running is an excellent exercise for children and young 
 people, but should be sparingly indulged in after the age of 
 thirty-five. If it be accompanied with a feeling of faint- 
 ness, breathlessness, and palpitation of the heart, the exer- 
 
9O PRACTICAL PHYSIOLOGY. 
 
 cise is too severe, and its continuance may do serious harm. 
 Running as an exercise is beneficial to those who have kept 
 themselves in practice and in sound condition. It brings into 
 play nearly every muscle of the body, and thus serves to de- 
 velop the power of endurance, as well as strength and capacity 
 for rapid movement. 
 
 Jumping may well be left to boys and young men under 
 twenty, but skipping with a rope, allied to jumping, is an 
 admirable and beneficial form of exercise. It brings into 
 action many muscles without putting undue strain upon any 
 particular group. 
 
 91. Skating, Swimming, and Rowing. Skating is a de- 
 lightful and invigorating exercise. It calls into play a great 
 variety of muscles, and is admirably adapted for almost all 
 ages. It strengthens the ankles and helps give an easy and 
 graceful carriage to the body. Skating is especially valuable, 
 as it can be enjoyed when other out-door exercises are not 
 convenient. 
 
 Every child above ten years of age should be taught to 
 swim. The art, once mastered, is never forgotten. It calls 
 into use a wide combination of muscles. This accomplishment, 
 so easily learned, should be a part of our education, as well as 
 baseball or bicycling, as it may chance to any one to save his 
 own life or that of a companion. 
 
 In many respects rowing is one of the most perfect exercises 
 at our command. It expands the chest, strengthens the body, 
 and gives tone to the muscles of the abdomen. It is very suit- 
 able for girls and women, as no other exercise is so well adapted 
 to remedy the muscular defects so marked in their sex. Even 
 elderly persons can row day after day without difficulty. The 
 degree of muscular effort required, can be regulated so that 
 those with weak hearts and weak lungs can adjust them- 
 selves to the exercise. 
 
PHYSICAL EXERCISE. 9 1 
 
 92. Bicycling as an Exercise. The bicycle as a means of 
 taking exercise has come into popular use with remarkable 
 rapidity. Sharp competition bids fair to make the wheel more 
 popular and less expensive than ever. Its phenomenal use by 
 persons of all ages and in all stations of life, is proof of the 
 enthusiasm with which this athletic exercise is employed by 
 women as well as by men. 
 
 Mechanical skill has removed most of the risks to health 
 and person which once existed. A good machine, used by 
 its owner with judgment, is the most convenient, the safest, 
 and the least expensive means of traveling for pleasure or 
 exercise. It is doing more than any other form of exercise to 
 improve the bodily condition of thousands whose occupations 
 confine them all day to sedentary work. Dependent upon no 
 one but himself, the cyclist has his means of" exercise always 
 at hand. No preparation is necessary to take a spin of ten 
 miles or so on the road, during a summer evening or before 
 breakfast. 
 
 Bicycling brings into active use the muscles of the legs as 
 well as those of the trunk and arms. It seems to benefit those 
 who suffer from dyspepsia, constipation, and functional dis- 
 orders of the liver. 
 
 A special caution must be used against overdoing in cycling, 
 for the temptation by rivalry, making a record, by social com- 
 petition on the road, is stronger in this form of exercise than 
 in any other, especially for young folks. Many cases have 
 occurred of permanent injury, and even loss of life, from col- 
 lapse simply by excessive exertion and exhaustion. 
 
 93. Outdoor Games and Physical Education. While out- 
 door games are not necessary to maintain health, yet we can 
 scarcely overestimate the part that the great games of baseball, 
 football, tennis, golf, and croquet, play in the physical develop- 
 ment of young people. When played in moderation and under 
 
Q2 PRACTICAL PHYSIOLOGY. 
 
 suitable conditions, they are most useful and beneficial exer- 
 cises. They are played in the open air, and demand a great 
 variety of vigorous muscular movement, with a considerable 
 amount of skill and adroitness of action. These games not 
 only involve healthful exercise, but develop all those manly 
 and wholesome qualities so essential to success in life. 
 
 A vigorous body is well-nigh essential to success, but equally 
 important are readiness of action, sound judgment, good temper, 
 personal courage, a sense of fair play, and above all, a spirit of 
 honor. Outdoor games, when played in a reasonable and 
 honorable manner, are most efficient and practical means to 
 develop these qualities in young people. 
 
 94. The School and Physical Education. The advantages to be 
 derived, during the school period, from the proper care and develop- 
 ment of the body, should be understood and appreciated by school 
 officials, teachers, and parents.. The school period is the best time 
 to shape the lives of pupils, not mentally or morally alone, but physi- 
 cally as well. This is the time, by the use of a few daily exercises at 
 school, to draw back the rounding shoulders, to form the habit of 
 sitting and standing erect, to build up strong and comely arms and 
 chests, and otherwise to train pupils to those methods which will serve 
 to ripen them into vigorous and well-knit men and women. 
 
 Teachers can by a little effort gain the knowledge requisite prop- 
 erly to instruct their pupils in a few systematic exercises. Gratify- 
 ing results will follow just as the teacher and pupils evince interest 
 and judgment in the work. It is found by experience that pupils are 
 not only quick to learn, but look forward eagerly to the physical exer- 
 cises as an interesting change from the routine of school life. 
 
 There should be a stated time for these school exercises, as for 
 any other duty. There can be practiced in the schoolroom a great 
 variety of interesting and useful exercises, which call for little or no 
 expense for apparatus. Such exercises should no more interfere with 
 the children's usual games than any other study does. Under no 
 circumstances should the play hours be curtailed. 
 
PHYSICAL EXERCISE. 
 
 93 
 
 95. Physical Exercises in School. Physical exercises of 
 some sort, then, should be provided for pupils in our schools, 
 especially in large towns and cities, where there is little oppor- 
 tunity for outdoor games, and they should form a part of the 
 regular course of study. The object should be the promotion 
 of sound health rather than the development of muscle, or per- 
 forming feats of agility or strength. Exercises with dumb-bells 
 and wands, or even without any apparatus, practiced a few 
 
 FIG. 44. Physical Exercises as carried on in Schools. 
 (From photographs.) 
 
 times a day, for five minutes at a time, do a great deal of good. 
 They relax the tension of body and mind, and introduce an 
 element of pleasure into the routine of school life. They 
 increase the breathing power and quicken the action of the 
 heart. 
 
 NOTE. " In early boyhood and youth nothing can replace the active sports so 
 much enjoyed at this period; and while no needless restrictions should be placed 
 upon them, consideration should be paid to the amount, and especially to the charac- 
 ter, of the games pursued by delicate youth. For these it would be better to develop 
 the weakened parts by means of systematic physical exercises and by lighter sports." 
 DR. JOHN M. KEATING on " Physical Development " in Pepper's Cyclopaedia of 
 the Diseases of Children. 
 
94 PRACTICAL PHYSIOLOGY. 
 
 If vigorously and systematically carried out, these exercises 
 invigorate all the tissues and organs of the body, and stimulate 
 them to renewed activity. They serve to offset the lack of proper 
 ventilation, faulty positions at the desks, and the prolonged 
 inaction of the muscles. To secure the greatest benefit from 
 physical training in school, it is important that the pupils be 
 interested in these exercises, and consider them a recreation, 
 and not a task. 1 
 
 96. Practical Points about Physical Exercise. The main 
 object in undertaking systematic and graduated physical exer- 
 cises is not to learn to do mere feats of strength and skill, but 
 the better to fit the individual for the duties and the work of life. 
 Exercises should be considered with reference to their availa- 
 bility from the learner's standpoint. The most beneficial 
 exercises ordinarily are the gentle ones, in which no strain is 
 put upon the heart and the respiration. The special aim is to 
 secure the equal use of all the muscles, not the development 
 of a few. The performance of feats of strength should never 
 come within the scope of any educational scheme. Exercises 
 which call for sustained effort, violent exertion, or sudden 
 strain are best avoided by those who have had no preparation 
 or training. 
 
 Regular exercise, not sudden and occasional prolonged exer- 
 tion, is necessary for health. The man or woman who works 
 in an office or store all the week, and on Sunday or a holiday 
 indulges in a long spin on the bicycle, often receives more harm 
 than good from the exertion. Exercise should be taken, so 
 
 1 " One-half the struggle of physical training has been won when a boy can be 
 induced to take a genuine interest in his bodily condition, to want to remedy its 
 defects, and to pride himself on the purity of his skin, the firmness of his muscles, and 
 the uprightness of his figure Whether the young man chooses afterwards to use the 
 gymnasium, to run, to row, to play ball, or to saw wood, for the purpose of improving 
 his physical condition, matters little, provided he accomplishes that object." DR. 
 D. A. SARGENT, Director of the Hemenway Gymnasium at Harvard University. 
 
PHYSICAL EXERCISE. 95 
 
 far as is convenient, in the open air, or in a large and well- 
 ventilated room. 1 
 
 After the more violent exercises, as baseball, football, a long 
 ride on the bicycle, or even after a prolonged walk, a warm 
 bath should be taken at the first convenient opportunity. Care 
 should be taken to rub down thoroughly, and to change a part 
 or all of the clothing. Exercise is comparatively valueless 
 until the idea of taking it for health is quite forgotten in the 
 interest and pleasure excited by the occasion. No exercise 
 should be carried to such a degree as to cause fatigue or 
 exhaustion. Keep warmly clad after exercise, avoid chills, 
 and always stop exercising as soon as fatigue is felt. 
 
 Wear clothing which allows free play to all the muscles of 
 the body. The clothing should be light, loose, and made of 
 wool. Care should be taken not to take cold by standing about 
 in clothes which are damp with perspiration. In brisk walking 
 and climbing hills keep the mouth shut, especially in cold 
 weather, and breathe through the nose, regulating the pace so 
 that it can be done without discomfort. 
 
 97. Effect of Alcoholic Liquors and Tobacco upon Physical 
 Culture. As a result of the unusual attention given to physical 
 culture in the last few years, hundreds of special instructors are 
 now employed in training young people in the theory and prac- 
 tice of physical exercise. These expert teachers, to do their 
 work with thoroughness and discipline, recognize the necessity 
 of looking after the daily living of their students. The time 
 of rising and retiring, the hours of sleep, the dress, the care of 
 
 1 " It is health rather than strength that is the great requirement of modern men 
 at modern occupations ; it is not the power to travel great distances, carry great 
 burdens, lift great weights, or overcome great material obstructions ; it is simply that 
 condition of body, and that amount of vital capacity, which shall enable each man in 
 his place to pursue his calling, and work on in his working life, with the greatest 
 amount of comfort to himself and usefulness to his fellowmen." MACLAREN'S 
 Physical Education. 
 
96 PRACTICAL PHYSIOLOGY. 
 
 the diet, and many other details of personal health become an 
 important part of the training. 
 
 Recognizing the fact that alcoholic drink and tobacco are so 
 disastrous to efficiency in any system of physical training, these 
 instructors rigidly forbid the use of these drugs under all cir- 
 cumstances. While this principle is perhaps more rigorously 
 enforced in training for athletic contests, it applies equally to 
 those who have in view only the maintenance of health. 
 
 Books on Physical Education. There are many excellent books on physical 
 education, which are easily obtained for reading or for reference. Among these 
 one of the most useful and suggestive is Blackie's well-known book, " How to Get 
 Strong and how to Stay so." This little book is full of kindly advice and practical 
 suggestions to those who may wish to begin to practice health exercises at home 
 with inexpensive apparatus. For more advanced work, Lagrange's " Physiology of 
 Bodily Exercise " and the Introduction to Maclaren's " Physical Education " may be 
 consulted. A notable article on " Physical Training ' by Joseph H. Sears, an Ex- 
 Captain of the Harvard Football Team, may be found in Roosevelt's " In Sickness 
 and in Health." 
 
 Price lists and catalogues of all kinds of gymnastic apparatus are easily obtained 
 on application to firms handling such goods. 
 
 Various Systems of Physical Exercises. The recent revival of popular interest 
 in physical education has done much to call the attention of the public to the use- 
 fulness and importance of a more thorough and systematic use of physical exercises, 
 both at home and in the schools. It is not within the scope of this book to describe 
 the various systems of gymnastic and calisthenic exercises now in common use in this 
 country. For the most part they have been modified and rearranged from other 
 sources, notably from the two great systems, i.e., Swedish and German. 
 
 For a most comprehensive work on the Swedish system, the teacher is referred to 
 the " Swedish System of Educational Gymnastics," with 264 illustrations, by Baron 
 Nils Posse. There is also a small manual for teachers, called " Handbook of 
 School Gymnastics of the Swedish Systems," by the same author. 
 
CHAPTER V. 
 FOOD AND DRINK. 
 
 98. Why we need Food. The body is often compared to a 
 steam-engine in good working order. An engine uses up fuel 
 and water to obtain from them the energy necessary to do its 
 work. So, we consume within our bodies certain nutritious 
 substances to obtain from them the energy necessary for our 
 activities. Just as the energy for the working of the engine is 
 obtained from steam by the combustion of fuel, so the energy 
 possessed by our bodies results from the combustion or oxida- 
 tion within us of the food we eat. Unless this energy is 
 provided for the body it will have but little power of doing 
 work, and like an engine without steam, must soon become 
 motionless. 
 
 99. Waste and Repair. A steam-engine from the first 
 stroke of its piston-rod begins to wear out, and before long 
 needs repair. All work involves waste. The engine, unless 
 kept in thorough repair, would soon stop. So with our bodies. 
 In their living cells chemical changes are constantly going on ; 
 energy, on the whole, is running down ; complex substances are 
 being broken up into simpler combinations. So long as life 
 lasts, food must be brought to the tissues, and waste products 
 carried away from them. It is impossible to move a single 
 muscle, or even to think for one moment, without some minute 
 part of the muscular or brain tissue becoming of no further 
 use in the body. The transformation of dead matter into living 
 tissue is the ever-present miracle which life presents even in its 
 lowest forms. 
 
98 PRACTICAL PHYSIOLOGY. 
 
 In childhood the waste is small, and the amount of food 
 taken is more than sufficient to repair th'e loss. Some of the 
 extra food is used in building up the body, especially the 
 muscles. As we shall learn in Chapter VIII., food is also 
 required to maintain the bodily heat. Food, then, is necessary 
 for the production of energy, for the repair of the body, for the 
 building up of the tissues, and for the maintenance of bodily 
 heat. 
 
 100. Nature of the Waste Material. An ordinarily healthy 
 person passes daily, on an average, by the kidneys about 50 
 ounces of waste material, of which 96 per cent is water, and 
 from the intestines, on an average, 5 ^ ounces, a large propor- 
 tion of which is water. By the skin, in the shape of sweat 
 and insensible perspiration, there is cast out about 23 ounces, 
 of which 99 per cent is water ; and by the lungs about 34 
 ounces, 10 of which are water and the remainder carbon 
 dioxid. 
 
 Now if we omit an estimate of the undigestible remains of 
 the food, we find that the main bulk of what daily leaves the 
 body consists of water, carbon dioxid, and certain solid matters 
 contained in solution in the renal secretion and the sweat. 
 The chief of these solid matters is urea, a complex product 
 made up of four elements, carbon, hydrogen, oxygen, and nitro- 
 gen. Water contains only two elements, hydrogen and oxygen ; 
 and carbon dioxid also has only two, carbon and oxygen. 
 Hence, what we daily cast out of our bodies consists essentially 
 of these four elements in the form mainly of water, carbon 
 dioxid, and urea. 
 
 These waste products represent the oxidation that has taken 
 place in the tissues in producing the energy necessary for the 
 bodily activities, just as the smoke, ashes, clinkers, and steam 
 represent the consumption of fuel and water in the engine. 
 Plainly, therefore, if we could restore to the body a supply of 
 
FOOD AND DRINK. 99 
 
 these four elements equivalent to that cast out, we could make 
 up for the waste. The object of food, then, is to restore to the 
 body an amount of the four elements equal to that consumed. 
 In other words, and briefly: The purpose of food is to 
 supply the waste of the tissues and to maintain the normal 
 composition of the blood. 
 
 101. Classification of Foods. Foods may be conveniently 
 divided into four great classes, to which the name f ood-stuffs 
 or alimentary principles has been given. They correspond to 
 the chief " proximate principles " of which the body consists. 
 To one or the other of these classes all available foods belong. 1 
 The classification of food-stuffs usually given is as follows : 
 
 I. Proteids, or Nitrogenous Foods. 
 
 II. Starches and Sugars, or Carbohydrates. 
 
 III. Fats and Oils. . 
 
 IV. Inorganic or Mineral Foods, Water, Salt. 
 
 102. Proteids, or Nitrogenous Foods. The proteids, fre- 
 quently spoken of as the nitrogenous foods, are rich in one or 
 more of the following organic substances : albumen, casein, 
 fibrin, gelatine, myosin, gluten, and legumin. 
 
 The type of this class of foods is albumen, well known as the 
 white of an egg. The serum of the blood is very rich in albu- 
 men, as is lean meat. The curd of milk consists mainly of 
 casein. Fibrin exists largely in blood and flesh foods. Gela- 
 tine is obtained from the animal parts of bones and connective 
 tissue by prolonged boiling. One of the chief constituents of 
 
 *To this classification may be added what are called albuminoids, a group 
 of bodies resembling proteids, but having in some respects a different nutritive 
 value. Gelatine, such as is found in soups or table gelatine is a familiar example of 
 the albuminoids. They are not found to any important extent in our raw foods, and 
 do not therefore usually appear in the analyses of the composition of foods. The 
 albuminoids closely resemble the proteids, but cannot be used like them to build up 
 protoplasm. 
 
IOO PRACTICAL PHYSIOLOGY. 
 
 muscular fiber is myosin. Gluten exists largely in the cereals 
 wheat, barley, oats, and rye. The proteid principle of peas and 
 beans is legumin, a substance resembling casein. 
 
 As the name implies, the proteids, or nitrogenous foods, con- 
 tain nitrogen ; carbohydrates and fats, on the contrary, do not 
 contain nitrogen. The principal proteid food-stuffs are milk, 
 eggs, flesh foods of all kinds, fish, and the cereals among vege- 
 table foods. Peas and beans are rich in proteids. The essen- 
 tial use of the proteids to the tissues is to supply the material 
 from which the new proteid tissue is made or the old proteid 
 tissue is repaired. They are also valuable as sources of energy to 
 the body. Now, as the proteid part of its molecule is the most 
 important constituent of living matter, it is evident that proteid 
 food is an absolute necessity. If our diet contained no proteids, 
 the tissues of the body would gradually waste away, and death 
 from starvation would result. All the food-stuffs are necessary 
 in one way or another to the preservation of perfect health, but 
 proteids, together with a certain proportion of water and inor- 
 ganic salts, are absolutely necessary for the bare maintenance 
 of animal life that is, for the formation and preservation of 
 living protoplasm. 
 
 103. Starches and Sugars. The starches, sugars, and 
 gums, also known as carbohydrates, enter largely into the 
 composition of foods of vegetable origin. They contain no 
 nitrogen, but the three elements, carbon, hydrogen, and oxygen, 
 the last two in the same proportion as in water. The starches 
 are widely distributed throughout the vegetable kingdom. They 
 are abundant in potatoes and the cereals, and in arrowroot, 
 rice, sago, and tapioca. Starch probably stands first in impor- 
 tance among the various vegetable foods. 
 
 The sugars are also widely distributed substances, and 
 include the cane, grape, malt, maple, and milk sugars. Here 
 also belong the gums and cellulose found in fruit, cereals, and all 
 
FOOD AND DRINK. J IOI 
 
 vegetables which form the basis of the plant cells and fibers. 
 Honey, molasses, and manna are included in this class. 
 
 The physiological value of the starches and sugars lies in the 
 fact that they are oxidized in the body, and a certain amount 
 of energy is thereby liberated. The energy of muscular work 
 and of the heat of the body comes largely from the oxidation, 
 or destruction, of this class of foods. Now, inasmuch as we 
 are continually giving off energy from the body, chiefly in the 
 form of muscular work and heat, it is evident that material for 
 the production of this energy must be taken in the food. The 
 carbohydrates constitute the bulk of our ordinary food. 
 
 104. Fats and Oils. These include not only the ordinary 
 fats of meat, but many animal and vegetable oils. They are 
 alike in chemical composition, consisting of carbon and hydro- 
 gen, with a little oxygen and no nitrogen. The principal kinds 
 of fat used as food are the fat of meat, butter, suet, and lard ; 
 but in many parts of the world various vegetable oils are 
 largely used, as the olive, palm, cotton seed, cocoanut, and 
 almond. 
 
 The use of the fats in the body is essentially the same as that 
 of the starches and sugars. Weight for weight they are more 
 valuable than the carbohydrates as sources of energy, but the 
 latter are more easily digested, and more easily oxidized in the 
 body. An important use of fatty foods is for the maintenance 
 of the bodily heat. The inhabitants of Arctic regions are thus 
 enabled, by large use of the fat and oil from the animals they 
 devour, to endure safely the severe cold. Then there is reason 
 to believe that fat helps the digestion of other foods, for it is 
 found that the body is better nourished when the fats are used 
 as food. When more fat is consumed than is required to keep 
 up the bodily heat and to yield working power, the excess is 
 stored up in various parts of the body, making a sort of reserve 
 fuel, which may be drawn upon at any future time. 
 
IO2 
 
 PRA'CTlCAL PHYSIOLOGY. 
 
 105. Saline or Mineral Foods. All food contains, besides 
 the substances having potential energy, as described, certain 
 saline matters. Water and salts are not usually considered 
 foods, but the results of scientific research, as well as the 
 experience of life, show that these substances are absolutely 
 necessary to the body. The principal mineral foods are salt, 
 lime, iron, magnesia, phosphorus, potash, and water. Except 
 common salt and water, these substances are usually taken only 
 in combination with other foods. 
 
 These saline matters are essential to health, and when not 
 present in due proportion nutrition is disturbed. If a dog be 
 fed on food freed from all salines, but otherwise containing 
 proper nutrients, he soon suffers from weakness, after a time 
 amounting to paralysis, and often dies in convulsions. 
 
 About 200 grains of common salt are required daily by an 
 adult, but a large proportion of this is in our food. Phosphate 
 of lime is obtained from milk and meats, and carbonate of lime 
 from the hard water we drink. Both are required for the bones 
 and teeth. The salts of potash, which assist in purifying the 
 blood, are obtained from vegetables and fruits. An iron salt is 
 found in most foods, and sulphur in the yolk of eggs. 
 
 106. Water. Water is of use chiefly as a solvent, and 
 while not strictly a food, is necessary to life. It enters into the 
 construction of every tissue and is constantly being removed 
 from the body by every channel of waste. 1 
 
 1 The amount of water in various tissues of the body is given by the following 
 table in parts of 1000: 
 
 SOLIDS. 
 
 Enamel, 
 
 Dentine, 
 
 Bone, 
 
 Fat, 
 
 Cartilage, 
 
 Liver, 
 
 Skin, 
 
 486 
 299 
 55 
 693 
 720 
 
 Brain, 
 Muscle, 
 Spleen, 
 Kidney, 
 Vitreous hu- 
 mor, 
 
 
 LIQUIDS. 
 
 
 750 
 
 Blood, 
 
 79 i 
 
 Serum, 
 
 959 
 
 757 
 
 Bile, 
 
 864 
 
 Gastric juice, 
 
 973 
 
 758 
 
 Blood plasma, 
 
 901 
 
 Tears, 
 
 982 
 
 827 
 
 Chyle, 
 
 928 
 
 Saliva, 
 
 995 
 
 
 Lymph, 
 
 958 
 
 Sweat, 
 
 995 
 
 987 
 
 
 
 
 
FOOD AND DRINK. 
 
 103 
 
 As a solvent water aids digestion, and as it forms about 80 
 per cent of the blood, it serves as a carrier of nutrient material 
 to all the tissues of the body. 
 
 IMPORTANT ARTICLES OF DIET. 
 
 107. Milk. The value of milk as a food cannot be over- 
 estimated. It affords nourishment in a very simple, convenient, 
 and perfect form. It is the sole food provided for the young of 
 all animals which nourish their young. It is an ideal food 
 containing, in excellent proportions, all the four elements neces- 
 sary for growth and health in earlier youth. 
 
 Cheese is the nitrogenous part of milk, which has been 
 coagulated by the use of rennet. The curd is then carefully 
 
 Composition of Food Materials. Careful analyses have been made of the dif- 
 ferent articles of food, mostly of the raw, or uncooked foods. As might be expected, 
 the analyses on record differ more or less in the percentages assigned to the various 
 constituents, but the following table will give a fair idea of the fundamental nutritive 
 value of the more common foods : 
 
 In 100 parts 
 
 Water 
 
 Proteid 
 
 Fat 
 
 Carbohydrate 
 
 Ash 
 
 Digestible 
 
 Cellulose 
 
 Meat 
 
 76.7 
 
 20.8 
 
 1.5 
 
 0.3 
 
 
 1.7 
 
 EsrcrS 
 
 73 7 
 
 12.6 
 
 12. 1 
 
 
 
 
 Cheese 
 
 /J'/ 
 
 36-60 
 
 25-33 
 
 7-30 
 
 3-7 
 
 
 
 3-4 
 
 Cow's Milk . . . 
 
 87.7 
 
 3-4 
 
 3-2 
 
 4.8 
 
 
 
 0.7 
 
 Wheat Flour .... . 
 
 13-3 
 
 10.2 
 
 0.9 
 
 74.8 
 
 0.3 
 
 o-S 
 
 Wheat Bread .-...-' . 
 
 35-6 
 
 7-i 
 
 0.2 
 
 55-5 
 
 0.3 
 
 i.i 
 
 Rye Flour .... 
 
 13-7 
 
 "5 
 
 2.1 
 
 69.7 
 
 1.6 
 
 M 
 
 Rye bread .... 
 
 42-3 
 
 6.1 
 
 0.4 
 
 49.2 
 
 0.5 
 
 1-5 
 
 Rice ...... 
 
 J3- 1 
 
 7.0 
 
 O.g 
 
 77-4 
 
 0.6 
 
 I.O 
 
 Corn 
 
 X 3- ' 
 
 9-9 
 
 4.6 
 
 68.4 
 
 2 e 
 
 T C 
 
 Macaroni .... 
 
 10. I 
 
 9.0 
 
 0-3 
 
 79.0 
 
 **3 
 
 0.3 
 
 a 
 0-5 
 
 Peas and Beans . . 
 
 12-15 
 
 23-26 
 
 H 
 
 49-54 
 
 4-7 
 
 2-3 
 
 Potatoes .... 
 
 75-5 
 
 2.0 
 
 0.2 
 
 20.6 
 
 0.7 
 
 I.O 
 
 Carrots . ... 
 
 87.1 
 
 I.O 
 
 O.2 
 
 Q 1 
 
 I A 
 
 
 Cabbage 
 
 90 
 
 2-3 
 
 o-5 
 
 ?'6 
 
 4-6 
 
 1.4 
 
 1-2 
 
 0.9 
 
 '3 
 
 Fruit 
 
 84 
 
 0.5 
 
 
 
 10 
 
 4 
 
 0.5 
 
 
IO4 PRACTICAL PHYSIOLOGY. 
 
 dried, salted, and pressed. Cheese is sometimes difficult of 
 digestion, as on account of its solid form it is not easily acted 
 upon by the digestive fluids. 
 
 108. Meats. The flesh of animals is one of our main 
 sources of food. Containing a large amount of proteid, it 
 is admirably adapted for building up and repairing the tissues 
 of the body. The proportion of water is also high, varying 
 from 50 to 75 per cent. The most common meats used in this 
 country are beef, mutton, veal, pork, poultry, and game. 
 
 Beef contains less fat and is more nutritious than either 
 mutton or pork. Mutton has a fine flavor and is easily digested. 
 Veal and lamb, though more tender, are less easily digested. 
 Pork contains much fat, and its fiber is hard, so that it is the 
 most difficult to digest of all the meats. Poultry and game 
 have usually a small proportion of fat, but are rich in phosphates 
 and are valued for their flavor. 
 
 109. Eggs. Consisting of about two-thirds water and the 
 rest albumen and fat, eggs are often spoken of as typical natu- 
 ral food. The white of an egg is chiefly albumen, with traces 
 of fat and salt ; the yolk is largely fat and salts. The yellow 
 color is due partly to sulphur. It is this which blackens a silver 
 spoon. Eggs furnish a convenient and concentrated food, and 
 if properly cooked are readily digested. 
 
 HO. Fish. Fish forms an important and a most nutritious 
 article of diet, as it contains almost as much nourishment as 
 butcher's meat. The fish- eating races and classes are remark- 
 ably strong and healthy. Fish is less stimulating than meat, 
 and is thus valuable as a food for invalids and dyspeptics. To 
 be at its best, fish should be eaten in its season. As a rule shell- 
 fish, except oysters, are not very digestible. Some persons are 
 unable to eat certain kinds of fish, especially shell-fish, without 
 eruptions on the skin and other symptoms of mild poisoning. 
 
FOOD AND DRINK. 10$ 
 
 in. Vegetable Foods. This is a large and important group 
 of foods, and embraces a remarkable number of different kinds 
 of diet. Vegetable foods include the cereals, garden vege- 
 tables, the fruits, and other less important articles. These 
 foods supply a certain quantity of albumen and fat, but their 
 chief use is to furnish starches, sugars, acids, and salts. The 
 vegetable foods indirectly supply the body with a large amount 
 of water, which they absorb in cooking. 
 
 112. Proteid Vegetable Foods. The most important proteid 
 vegetable foods are those derived from the grains of cereals 
 and certain leguminous seeds, as peas and beans. The grains 
 when ground make the various flours or meals. They contain 
 a large quantity of starch, a proteid substance peculiar to them 
 called gluten, and mineral salts, especially phosphate of lime. 
 Peas and beans contain a smaller proportion of starch, but more 
 proteid matter, called legumin, or vegetable casein. Of the 
 cereal foods, wheat is that most generally useful. Wheat, and 
 corn and oatmeal form most important articles of diet. Wheat 
 flour has starch, sugar, and gluten nearly everything to 
 support life except fat. 
 
 Oatmeal is rich in proteids. In some countries, as Scotland, 
 it forms an important article of diet, in the form of porridge 
 or oatmeal cakes. 
 
 Corn meal is not only rich in nitrogen, but the proportion of 
 fat is also large; hence it is a most important and nutritious 
 article of food. Rice, on the other hand, contains less proteids 
 than any other cereal grain, and is the least nutritious. Where 
 used as a staple article of food, as in India, it is commonly 
 mixed with milk, cheese, or other nutritious substances. Peas 
 and beans, distinguished from all other vegetables by their large 
 amount of proteids excel in this respect even beef, mutton, 
 and fish. They take the place of meats with those who believe 
 in a vegetable diet. 
 
IO6 PRACTICAL PHYSIOLOGY. 
 
 113. Non-proteid Vegetable Foods. The common potato is 
 the best type of non-proteid vegetable food. When properly 
 cooked it is easily digested and makes an excellent food. It con- 
 tains about 75 per cent of water, about 20 per cent of carbohy- 
 drates, chiefly starch, 2 per cent of proteids, and a little fat and 
 saline matters. But being deficient in flesh-forming materials, 
 it is unfit for an exclusive food, but is best used with milk, meat, 
 and other foods richer in proteid substances. Sweet potatoes, 
 of late years extensively used as food, are rich in starch and 
 sugar. Arrowroot, sago, tapioca, and similar foods are nutri- 
 tious, and easily digested, and with milk furnish excellent 
 articles of diet, especially for invalids and children. 
 
 Explanation of the Graphic Chart. The graphic chart, on the next 
 page, presents in a succinct and easily understood form the composition 
 of food materials as they are bought in the market, including the 
 edible and non-edible portions. It has been condensed from Dr. W. 
 O. Atwater's valuable monograph on " Foods and Diet." This work 
 is known as the Yearbook of the U. S. Department of Agriculture 
 for 1894. 
 
 KEY : I, percentage of nutrients ; 2, fuel value of i pound in calories. The unit 
 of heat, called a calorie, or gramme-degree, is the amount of heat which is 
 necessary to raise one gramme (1543 grains) of water one degree centigrade 
 (1.8 Fahr.). A, round beef; B, sirloin beef; C, rib beef; D, leg of mutton; 
 E, spare rib of pork; F, salt pork; G, smoked ham; H, fresh codfish; I, 
 oysters; J, milk; K, butter; L, cheese; M, eggs; N, wheat bread; O, corn 
 meal; P, oatmeal; Q, dried beans; R, rice; S, potatoes; T, sugar. 
 
 This table, among other things, shows that the flesh of fish contains 
 more water than that of warm-blooded animals. It may also be seen 
 that animal foods contain the most water ; and vegetable foods, 
 except potatoes, the most nutrients. Proteids and fats exist only in 
 small proportions in most vegetables, except beans and oatmeal. 
 Vegetable foods are rich in carbohydrates while meats contain none. 
 The fatter the meat the less the amount of water. Thus very lean 
 meat may be almost four-fifths water, and fat pork almost one-tenth 
 water. 
 
FOOD AND DRINK. 
 
 COMPOSITION OF FOOD MATERIALS. 
 
 Nutritive ingredients, refuse, and fuel value. 
 
 Nutrients. Non-Nutrients. 
 
 Protein. Fats. Carbo- Mineral 
 
 hydrates, matters. 
 
 Water. Refuse. 
 
 Fuel Value. 
 Calories. 
 
 90 100 
 
 10 
 
 40 
 
 50 
 
 80 
 
 70 
 
 80 
 
 400 800 1200 1600 2000 2400 2800 3200 3600 
 
 FIG. 45. Graphic Chart of the Composition of Food Materials. 
 
108 PRACTICAL PHYSIOLOGY. 
 
 114. Non-proteid Animal Foods. Butter is one of the most 
 digestible of animal fats, agreeable and delicate in flavor, and 
 is on this account much used as a wholesome food. Various 
 substitutes have recently come into use. These are all made 
 from animal fat, chiefly that of beef, and are known as butter- 
 ine, oleomargarine, and by other trade names. These prepara- 
 tions, if properly made, are wholesome, and may be useful 
 substitutes for butter, from which they differ but little in 
 composition. 
 
 115. Garden Vegetables. Various green, fresh, and succu- 
 lent vegetables form an essential part of our diet. They are 
 of importance not so much on account of their nutritious ele- 
 ments, which are usually small, as for the salts they supply, 
 especially the salts of potash. It is a well-known fact that the 
 continued use of a diet from which fresh vegetables are excluded 
 leads to a disease known as scurvy. They are also used for 
 the agreeable flavor possessed by many, and the pleasant 
 variety and relish they give to the food. The undigested resi- 
 due left by all green vegetables affords a useful stimulus to 
 intestinal contraction, and tends to promote the regular action 
 of the bowels. 
 
 116. Fruits. A great variety of fruits, both fresh and dry, 
 is used as food, or as luxuries. They are of little nutritive 
 value, containing, as they do, much water and only a small 
 amount of proteid, but are of use chiefly for the sugar, vege- 
 table acids, and salts they contain. 
 
 In moderate quantity, fruits are a useful addition to our regu- 
 lar diet. They are cooling and refreshing, of agreeable flavor, 
 and tend to prevent constipation. Their flavor and juiciness 
 serve to stimulate a weak appetite and to give variety to an 
 otherwise heavy diet. If eaten in excess, especially in an 
 unripe or an overripe state, fruits may occasion a disturbance 
 of the stomach and bowels, often of a severe form. 
 
FOOD AND DRINK. IOQ 
 
 117. Condiments. The refinements of cookery as well as 
 the craving of the appetite, demand many articles which cannot 
 be classed strictly as foods. They are called condiments, and 
 as such may be used in moderation. They give flavor and 
 relish to food, excite appetite and promote digestion. Condi- 
 ments increase the pleasure of eating, and by their stimulating 
 properties promote secretions of the digestive fluids and excite 
 the muscular contractions of the alimentary canal. 
 
 The well-known condiments are salt, vinegar, pepper, ginger, 
 nutmeg, cloves, and various substances containing ethereal 
 oils and aromatics. Their excessive use is calculated to excite 
 irritation and disorder of the digestive organs. 
 
 118. Salt. The most important and extensively used of the 
 condiments is common salt. It exists in all ordinary articles 
 of diet, but in quantities not sufficient to meet the wants 
 of the bodily tissues. Hence it is added to many articles of 
 food. It improves their flavor, promotes certain digestive 
 secretions, and meets the nutritive demands of the body. The 
 use of salt seems based upon an instinctive demand of the sys- 
 tem for something necessary for the full performance of its 
 functions. Food without salt, however nutritious in other 
 respects, is taken with reluctance and digested with difficulty. 
 
 Salt has always played an important and picturesque part in 
 the history of dietetics. Reference to its worth and necessity 
 abounds in sacred and profane history. In ancient times, salt 
 was the first thing placed on the table and the last removed. 
 The place at the long table, above or below the salt, indicated 
 rank. It was everywhere the emblem of hospitality. In parts 
 of Africa it is so scarce that it is worth its weight in gold, and is 
 actually used as money. Torture was inflicted upon prisoners of 
 state in olden times by limiting the food to water and bread, with- 
 out salt. So intense may this craving for salt become, that men 
 have often risked their liberty and even their lives to obtain it. 
 
IIO PRACTICAL PHYSIOLOGY. 
 
 119. Water. The most important natural beverage is pure 
 water ; in fact it is the only one required. Man has, however, 
 from the earliest times preferred and daily used a variety of 
 artificial drinks, among which are tea, coffee, and cocoa. 
 
 All beverages except certain strong alcoholic liquors, consist 
 almost entirely of water. It is a large element of solid foods, 
 and our bodies are made up to a great extent of water. Every- 
 thing taken into the circulating fluids of the body, or eliminated 
 from them, is done through the agency of water. As a solvent 
 it is indispensable in all the activities of the body. 
 
 It has been estimated that an average-sized adult loses by 
 means of the lungs, skin, and kidneys about eighty ounces of 
 water every twenty-four hours. To restore this loss about four 
 pints must be taken daily. About one pint of this is obtained 
 from the food we eat, the remaining three pints being taken as 
 drink. One of the best ways of supplying water to the body 
 is by drinking it in its pure state, when its solvent properties 
 can be completely utilized. The amount of water consumed 
 depends largely upon the amount of work performed by the 
 body, and upon the temperature. 
 
 Being one of the essential elements of the body, it is highly 
 important that water should be free from harmful impurities. 
 If it contain the germs of disease, sickness may follow its use. 
 Without doubt the most important factor in the spread of 
 disease is, with the exception of impure air, impure water. 
 The chief agent in the spread of typhoid fever is impure water. 
 So with cholera, the evidence is overwhelming that filthy 
 water is an all-powerful agent in the spread of this terrible 
 disease. 
 
 120. Tea, Coffee, and Cocoa. The active principle of tea 
 is called theine ; that of coffee, caffeine, and of cocoa, theo- 
 bromine. They also contain an aromatic, volatile oil, to which 
 they owe their distinctive flavor. Tea and coffee also contain 
 
FOOD AND DRINK. Ill 
 
 an astringent called tannin, which gives the peculiar bitter 
 taste to the infusions when steeped too long. In cocoa, the 
 fat known as cocoa butter amounts to fifty per cent. 
 
 121. Tea. It has been estimated that one-half of the 
 human race now use tea, either habitually or occasionally. 
 Its use is a prolific source of indigestion, palpitation of the 
 heart, persistent wakefulness, and of other disorders. When 
 used at all it should be only in moderation. Persons who 
 cannot use it without feeling its hurtful effects, should leave 
 it alone. It should not be taken on an empty stomach, nor 
 sipped after every mouthful of food. 
 
 122. Coffee. Coffee often disturbs the rhythm of the heart 
 and causes palpitation. Taken at night, coffee often causes 
 wakefulness. This effect is so well known that it is often 
 employed to prevent sleep. Immoderate use of strong coffee 
 may produce other toxic effects, such as muscular tremors, 
 nervous anxiety, sick-headache, palpitation, and various un- 
 comfortable feelings in the cardiac region. Some persons 
 cannot drink even a small amount of tea or coffee without 
 these unpleasant effects. These favorite beverages are unsuit- 
 able for young people. 
 
 123. Cocoa. The beverage known as cocoa comes from the 
 seeds of the cocoa-tree, which are roasted like the coffee berries 
 to develop the aroma. Chocolate is manufactured cocoa, 
 sugar and flavors being added to the prepared seeds. Choco- 
 late is a convenient and palatable form of highly nutritious 
 food. For those with whom tea and coffee disagree, it may be 
 an agreeable beverage. The large quantity of fat which it 
 contains, however, often causes it to be somewhat indigestible. 
 
 124. Alcoholic Beverages. There is a class of liquids 
 which are certainly not properly food or drink, but being so 
 commonly used as beverages, they seem to require special 
 
112 PRACTICAL PHYSIOLOGY. 
 
 notice in this chapter. In view of the great variety of alcoholic 
 beverages, the prevalence of their use, and the very remarkable 
 deleterious effects they produce upon the bodily organism, they 
 imperatively demand our most careful attention, both from a 
 physiological and an hygienic point of view. 
 
 125. Nature of Alcohol. The ceaseless action of minute 
 forms of plant life, in bringing about the decomposition of the 
 elaborated products of organized plant or animal structures, 
 will be described in more detail (sees. 394-398). 
 
 All such work of vegetable organisms, whether going on in 
 the moulding cheese, in the souring of milk, in putrefying meat, 
 in rotting fruit, or in decomposing fruit juice, is essentially one 
 of fermentation, caused by these minute forms of plant life. 
 There are many kinds of fermentation, each with its own 
 special form of minute plant life or micro-organism. 
 
 In this section we are more especially concerned about that 
 fermentation which results from the decomposition of sweet 
 fruit, plant, or other vegetable, juices which are composed 
 largely of water containing sugar and flavoring matters. 
 
 This special form of fermentation is known as alcoholic or 
 vinous fermentation, and the micro-organisms that cause it are 
 familiarly termed alcoholic ferments. The botanist classes 
 them as Saccharomycetes, of which there are several varieties. 
 Germs of Saccharomycetes are found on the surfaces and stems 
 of fruit as it is ripening. While the fruit remains whole these 
 germs have no power to invade the juice, and even when the 
 skins are broken the conditions are less favorable for their 
 work than for that of the moulds, 1 which are the cause of the 
 rotting of fruit. 
 
 1 The work of some kinds of moulds may be apparent to the eye, as in the growths 
 that form on old leather and stale bread and cheese. That of others goes on unseen, 
 as when acids are formed in stewed fruits. Concerning the work of the different 
 kinds of moulds, Troussart says : " Mucor mucedo devours our preserves ; Ascophora 
 mucedo turns our bread mouldy ; Molinia is nourished at the expense of our fruits ; 
 
FOOD AND DRINK. 113 
 
 But when fruit is crushed and its juice pressed out, the 
 Saccharomycetes are carried into it where they cannot get the 
 oxygen they need from the air. They are then able to obtain 
 oxygen by taking it from the sugar of the juice. By so doing 
 they cause a breaking up of the sugar and a rearrangement of 
 its elements. Two new substances are formed in this decom- 
 position of sugar, viz., carbon dioxid, which arises from the 
 liquid in tiny bubbles, and alcohol, a poison which remains in 
 the fermenting fluid. 
 
 Now we must remember that fermentation entirely changes 
 the nature of the substance fermented. For all forms of 
 decomposition this one law holds good. Before alcoholic fer- 
 mentation, the fruit juice was wholesome and beneficial ; after 
 fermentation, it becomes, by the action of the minute germs, a 
 poisonous liquid known as alcohol, and which forms an essen- 
 tial part of all intoxicating beverages. 
 
 Taking advantage of this great law of fermentation which 
 dominates the realm of nature, man has devised means to 
 manufacture various alcoholic beverages from a great variety 
 of plant structures, as ripe grapes, pears, apples, and other 
 fruits, cane juices, corn, the malt of barley, rye, wheat, and 
 other cereals. 
 
 The process differs according to the substance used and the 
 manner in which it is treated, but the ultimate outcome is 
 always the same, viz., the manufacture of a beverage contain- 
 ing a greater or less proportion of alcoholic poison. By the 
 process of distillation, new and stronger liquor is made. Bev- 
 erages thus distilled are known as ardent spirits. Brandy is 
 distilled from wine, rum from fermented molasses, and com- 
 mercial alcohol mostly from whiskey. 
 
 Mucor herbarium destroys the herbarium of the botanist ; and Choetonium chartatum 
 develops itself on paper, on the insides of books and on their bindings, when they 
 come in contact with a damp wall." TROUSSART'S Microbes, Ferments, and 
 Moulds. 
 
114 PRACTICAL PHYSIOLOGY. 
 
 The poisonous element in all forms of intoxicating drinks, 
 and the one so fraught with danger to the bodily tissues, is the 
 alcohol they contain. The proportion of the alcoholic ingre- 
 dient varies, being about 50 per cent in brandy, whiskey, and 
 rum, about 20 to 15 per cent in wines, down to 5 per cent, or 
 less, in the various beers and cider ; but whether the propor- 
 tion of alcohol be more or less, the same element of danger 
 is always present. 
 
 .126. Effects of Alcoholic Beverages upon the Human 
 System. One of the most common alcoholic beverages is 
 wine, made from the juice of grapes. As the juice flows from 
 the crushed fruit the ferments are washed from the skins and 
 stems into the vat. Here they bud and multiply rapidly, pro- 
 ducing alcohol. In a few hours the juice that was sweet and 
 wholesome while in the grape is changed to a poisonous liquid, 
 capable of injuring whoever drinks it. One of the gravest 
 dangers of wine-drinking is the power which the alcohol in 
 it has to create a thirst which demands more alcohol. The 
 spread of alcoholism in wine-making countries is an illustration 
 of this fact. 
 
 Another alcoholic beverage, common in apple-growing dis- 
 tricts, is cider. Until the microscope revealed the ferment 
 germ on the " bloom " of the apple-skin, very little was known 
 of the changes produced in cider during the mysterious process 
 of "working." Now, when we see the bubbles of gas in the 
 glass of cider we know what has produced them, and we know 
 too that a poison which we do not see is there also in corre- 
 sponding amounts. We have learned, too, to trace the wrecked 
 hopes of many a farmer's family to the alcohol in the cider 
 which he provided so freely, supposing it harmless. 
 
 Beer and other malt liquors are made from grain. By 
 sprouting the grain, which changes its starch to sugar, and 
 then dissolving out the sugar with water, a sweet liquid is 
 
FOOD AND DRINK. 115 
 
 obtained which is fermented with yeast, one kind of alcoholic 
 ferment. Some kinds of beer contain only a small percentage 
 of alcohol, but these are usually drunk in proportionately large 
 amounts. The life insurance company finds the beer drinker 
 a precarious risk ; the surgeon finds him an unpromising sub- 
 ject ; the criminal court finds him conspicuous in its proceed- 
 ings. The united testimony from all these sources is that beer 
 is demoralizing, mentally, morally, and physically. 
 
 127. Cooking. The process through which nearly all food 
 used by civilized man has to pass before it is eaten is known as 
 cooking. Very few articles indeed are consumed in their natural 
 state, the exceptions being eggs, milk, oysters, fruit and a few vege- 
 tables. Man is the only animal that cooks his food. Although 
 there are savage races that have no knowledge of cooking, 
 civilized man invariably cooks most of his food. It seems to 
 be true that as nations advance in civilization they make a 
 proportionate advance in the art of cooking. 
 
 Cooking answers most important purposes in connection 
 with our food, especially from its influence upon health. It 
 enables food to be more readily chewed, and more easily 
 digested. Thus, a piece of meat when raw is tough and tena- 
 cious, but if cooked the fibers lose much of their toughness, 
 while the connective tissues are changed into a soft and jelly- 
 like mass. Besides, the meat is much more readily masticated 
 and acted upon by the digestive fluids. So cooking makes 
 vegetables and grains softer, loosens their structure, and en- 
 ables the digestive juices readily to penetrate their substance. 
 
 Cooking also improves or develops flavors in food, especially 
 in animal foods, and thus makes them attractive and pleasant 
 to the palate. The appearance of uncooked meat, for example, 
 is repulsive to our taste, but by the process of cooking, agree- 
 able flavors are developed which stimulate the appetite and 
 the flow of digestive fluids. 
 
Il6 PRACTICAL PHYSIOLOGY. 
 
 Another important use of cooking is that it kills any minute 
 parasites or germs in the raw food. The safeguard of cooking 
 thus effectually removes some important causes of disease. 
 The warmth that cooking imparts to food is a matter of no 
 slight importance ; for warm food is more readily digested, and 
 therefore nourishes the body more quickly. 
 
 The art of cooking plays a very important part in the matter 
 of health, and thus of comfort and happiness. Badly cooked 
 and ill-assorted foods are often the cause of serious disorders. 
 Mere cooking is not enough, but good cooking is essential. 
 
 EXPERIMENTS. 
 EXPERIMENTS WITH THE PROTEIDS. 
 
 31. As a type of the group of proteids we take the white of egg, egg- 
 white or egg-albumen. Break an egg carefully, so as not to mix the white 
 with the yolk. Drop about half a teaspoonful of the raw white of egg into 
 half a pint of distilled water. Beat the mixture vigorously with a glass 
 rod until it froths freely. Filter through several folds of muslin until a 
 fairly clear solution is obtained. 
 
 32. To a small quantity of this solution in a test tube add strong nitric 
 acid, and boil. Note the formation of a white precipitate, which turns yellow. 
 After cooling, add ammonia, and note that the precipitate becomes orange. 
 
 33. Add to the solution of egg-albumen, excess of strong solution of 
 caustic soda (or potash), and then a drop or two of very dilute solution (one 
 per cent) of copper sulphate. A violet color is obtained which deepens on 
 boiling. 
 
 34. Boil a small portion of the albumen solution in a test tube, adding 
 drop by drop dilute acetic acid (two per cent) until a flaky coagulum of 
 insoluble albumen separates. 
 
 EXPERIMENTS WITH STARCH. 
 
 35. Wash a potato and peel it. Grate it on a nutmeg grater into a 
 tall cylindrical glass full of water. Allow the suspended particles to sub- 
 side, and after a time note the deposit. The lowest layer consists of a 
 white powder, or starch, and above it lie coarser fragments of cellulose and 
 other matters. 
 
FOOD AND DRINK. 1 1/ 
 
 36. Examine under the microscope a bit of the above white deposit. 
 Note that each starch granule shows an eccentric hilum with concentric 
 markings. Add a few drops of very dilute solution of iodine. Each granule 
 becomes blue, while the markings become more distinct. 
 
 37. Examine a few of the many varieties of other kinds of starch 
 granules, as in rice, arrowroot, etc. Press some dry starch powder 
 between the thumb and forefinger, and note the peculiar crepitation. 
 
 38. Rub a few bits of starch in a little cold water. Put a little of the 
 mixture in a large test tube, and then fill with boiling water. Boil until an 
 imperfect opalescent solution is obtained. 
 
 39. Add powdered dry starch to cold water. It is insoluble. Filter and 
 test the filtrate with iodine. It gives no blue color. 
 
 40. Boil a little starch with water ; if there is enough starch it sets on 
 cooling and a paste results. 
 
 41. Moisten some flour with water until it forms a tough, tenacious 
 dough ; tie it in a piece of cotton cloth, and knead it in a vessel containing 
 water until all the starch is separated. There remains on the cloth a 
 grayish white, sticky, elastic "gluten," made up of albumen, some of the 
 ash, and fats. Draw out some of the gluten into threads, and observe its 
 tenacious character. 
 
 42. Shake up a little flour with ether in a test tube, with a tight-fitting 
 cork. Allow the mixture to stand for an hour, shaking it from time to time. 
 Filter off the ether, and place some of it on a perfectly clean watch glass. 
 Allow the ether to evaporate, when a greasy stain will be left, thus showing 
 the presence of fats in the flour. 
 
 43. Secure a specimen of the various kinds of flour, and meal, peas, 
 beans, rice, tapioca, potato, etc. Boil a small quantity of each in a test 
 tube for some minutes. Put a bit of each thus cooked on a white plate, 
 and pour on it two or three drops of the tincture of iodine. Note the 
 various changes of color, blue, greenish, orange, or yellowish. 
 
 EXPERIMENTS WITH MILK. 
 
 44. Use fresh cow's milk. Examine the naked-eye character of the milk. 
 Test its reaction with litmus paper. It is usually neutral or slightly alkaline. 
 
 45. Examine with the microscope a drop of milk, noting numerous 
 small, highly refractive oil globules floating in a fluid. 
 
 46. Dilute one ounce of milk with ten times its volume of water. Add 
 cautiously dilute acetic acid until there is a copious, granular-looking pre- 
 
Il8 PRACTICAL PHYSIOLOGY. 
 
 cipitate of the chief proteid of milk (caseinogen), formerly regarded as a 
 derived albumen. This action is hastened by heating. 
 
 47. Saturate milk with Epsom salts, or common salt. The proteid and 
 fat separate, rise to the surface, and leave a clear fluid beneath. 
 
 48. Place some milk in a basin ; heat it to about 100 F., and add a few 
 drops of acetic acid. The mass curdles and separates into a solid curd 
 (proteid and fat) and a clear fluid (the whey), which contains the lactose. 
 
 49. Take one or two teaspoonf uls of fresh milk in a test tube ; heat it, 
 and add a small quantity of extract of rennet. Note that the whole mass 
 curdles in a few minutes, so that the tube can be inverted without the curd 
 falling out. Soon the curd shrinks, and squeezes out a clear, slightly 
 yellowish fluid, the whey. 
 
 50. Boil the milk as before, and allow it to cool ; then add rennet. No 
 coagulation will probably take place. It is more difficult to coagulate boiled 
 milk with rennet than unboiled milk. 
 
 51. Test fresh milk with red litmus paper; it should turn the paper pale 
 blue, showing that it is slightly alkaline. Place aside for a day or two, and 
 then test with blue litmus paper ; it will be found to be acid. This is due 
 to the fact that lactose undergoes the lactic acid fermentation. The lactose 
 is converted into lactic acid by means of a special ferment. 
 
 52. Evaporate a small quantity of milk to dryness in an open dish. 
 After the dry residue is obtained, continue to apply heat ; observe that it 
 chars and gives off pungent gases. Raise the temperature until it is red 
 hot ; allow the dish then to cool ; a fine white ash will be left behind. This 
 represents the inorganic matter of the milk. 
 
 EXPERIMENTS WITH THE SUGARS. 
 
 53. Cane sugar is familiar as cooking and table sugar. The little white 
 grains found with raisins are grape sugar, or glucose. Milk sugar is readily 
 obtained of the druggist. Prepare a solution of the various sugars by 
 dissolving a small quantity of each in water. Heat each solution with sul- 
 phuric acid, and it is seen to darken or char slowly. 
 
 54. Place some Fehling solution (which can be readily obtained at the 
 drug store as a solution, or tablets may be bought which answer the same 
 purpose) in a test tube, and boil. If no yellow discoloration takes place, it 
 is in good condition. Add a few drops of the grape sugar solution and 
 boil, when the mixture suddenly turns to an opaque yellow or red color. 
 
 55. Repeat same experiment with milk sugar. 
 
CHAPTER VI. 
 DIGESTION. 
 
 128. The Purpose of Digestion. As we have learned, our 
 bodies are subject to continual waste, due both to the wear and 
 tear of their substance, and to the consumption of material for 
 the production of their heat and energy. The waste occurs in 
 no one part alone, but in all the tissues. 
 
 Now, the blood comes into direct contact with every one of 
 these tissues. The ultimate cells which form the tissues are 
 constantly being bathed by the myriads of minute blood-vessels 
 which bring to the cells the raw material needed for their 
 continued renewal. These cells are able to select from the 
 nutritive fluid whatever they require to repair their waste, and 
 to provide for their renewed activity. At the same time, the 
 blood, as it bathes the tissues, sweeps into its current and 
 bears away the products of waste. 
 
 Thus the waste occurs in the tissues and the means of repair 
 are obtained from the blood. The blood is thus continually 
 being impoverished by having its nourishment drained away. 
 How, then, is the efficiency of the blood maintained? The 
 answer is that while the ultimate purpose of the food is for 
 the repair of the waste, its immediate destination is the blood. 1 
 
 129. Absorption of Food by the Blood. How does the 
 food pass from the cavity of the stomach and intestinal canal 
 into the blood-vessels? There are no visible openings which 
 
 1 " The physiological wear of the organism is constantly being repaired by the 
 blood ; but in order to keep the great nutritive fluid from becoming impoverished, 
 the matters which it is constantly losing must be supplied from some source out of 
 the body, and this necessitates the ingestion of articles which are known as food." 
 FLINT'S Text-book of Human Physiology. 
 
120 
 
 PRACTICAL PHYSIOLOGY. 
 
 permit communication. It is done by what in physics is known 
 as endosmotic and exosmotic action. That is, whenever there 
 are two solutions of different densities, separated only by an 
 animal membrane, an interchange will take place between them 
 through the membrane. 
 
 To illustrate : in the walls of the stomach and intestines 
 there is a network of minute vessels filled with blood, a liquid 
 
 containing many 
 substances in solu- 
 tion. The stomach 
 and intestinal canal 
 also contain liquid 
 food, holding many 
 substances in solu- 
 tion. A membrane, 
 made up of the ex- 
 tremely thin walls of 
 the blood-vessels 
 and intestines, sep- 
 arates the liquids. 
 An exchange takes 
 place between the 
 blood and the con- 
 tents of the stomach 
 
 FIG. 46. Cavities of the Mouth, Pharynx, etc. (Section 
 
 in the middle line designed to show the mouth in its and OOWe\S, by which 
 
 relations to the nasal fossae, the pharynx, and the the dissolved Sub- 
 
 larynx.) stances of food pass 
 
 A, sphenoidal sinus ; B, internal orifice of Eustachian tube ; through the SCparat- 
 C, velum palati ; D, anterior pillar of soft palate; E, pos- 
 terior pillar of soft palate ; F, tonsil; H, lingual portion of m g membranes into 
 
 the pharynx; K, lower portion of the pharynx; L, larynx; $16 blood 
 M, section of hyoid bone ; N, epiglottis ; O, palatine arch. 
 
 This change, by 
 
 which food is made ready to pass into the blood, constitutes 
 food-digestion, and the organs concerned in bringing about 
 this change in the food are the digestive organs. 
 
DIGESTION. 121 
 
 130. The General Plan of Digestion. It is evident that 
 the digestive organs will be simple or complex, according to 
 the amount of change which is necessary to prepare the food 
 to be taken up by the blood. If the requisite change is slight, 
 the digestive organs will be few, and their structure simple. 
 But if the food is varied and complex in composition, the 
 
 FIG. 47. Diagram of the Structure of Secreting Glands. 
 
 A, simple tubular gland ; B, gland with mouth shut and sac formed ; C, gland with a 
 coiled tube ; D, plan of part of a racemose gland. 
 
 digestive apparatus will be complex. This condition applies 
 to the food and the digestion of man. 
 
 The digestive apparatus of the human body consists of the 
 alimentary canal and tributary organs which, although outside 
 of this canal, communicate with it by ducts. The alimentary 
 canal consists of the mouth, the pharynx, the oesophagus, the 
 stomach, and the intestines. Other digestive organs which 
 are tributary to this canal, and discharge their secretions into 
 it, are the salivary glands, 1 the liver, and the pancreas. 
 
 1 Glands. Glands are organs of various shapes and sizes, whose special work it is 
 to separate materials from the blood for further use in the body, the products being 
 known as secretion and excretion. The means by which secretion and excretion 
 are effected are, however, identical. The essential parts of a gland consist of a base- 
 ment membrane, on one side of which are found actively growing cells, on the other 
 is the blood current, flowing in exceedingly thin-walled vessels known as the capil- 
 laries. The cells are able to select from the blood whatever material they require 
 and which they elaborate into the particular secretion. In Fig. 47 is illustrated, 
 diagrammatically, the structure of a few typical secreting glands. The continuous 
 line represents the basement membrane. The dotted line represents the position of 
 the cells on one side of the basement membrane. The irregular lines show the posi- 
 tion of the blood-vessels. 
 
122 PRACTICAL PHYSIOLOGY. 
 
 The digestive process is subdivided into three steps, which 
 take place in the mouth, in the stomach, and in the intestines. 
 
 131. The Mouth. The mouth is the cavity formed by the 
 lips, the cheeks, the palate, and the tongue. Its bony roof 
 is made up of the upper jawbone on each side, and the palate 
 bones behind. This is the hard palate, and forms only the 
 front portion of the roof. The continuation of the roof is called 
 the soft palate, and is made up of muscular tissue covered with 
 mucous membrane. 
 
 The mouth continues behind into the throat, the separation 
 between the two being marked by fleshy pillars which arch up 
 from the sides to form the soft palate. In the middle of this 
 arch there hangs from its free edge a little lobe called the 
 uvula. On each side where the pillars begin to arch is an 
 almond-shaped body known as the tonsil. When we take cold, 
 one or both of the tonsils may become inflamed, and so swollen 
 as to obstruct the passage into the throat. The mouth is lined 
 with mucous membrane, which is continuous with that of the 
 throat, oesophagus, stomach, and intestines (Fig. 51). 
 
 132. Mastication, or Chewing. The first step of the pro- 
 cess of digestion is mastication, the cutting and grinding of 
 the food by the teeth, effected by the vertical and lateral move- 
 ments of the lower jaw. While the food is thus being crushed, 
 it is moved to and fro by the varied movements of the tongue, 
 that every part of it may be acted upon by the teeth. The 
 advantage of this is obvious. The more finely the food is divided, 
 the more easily will the digestive fluids reach every part of it, 
 and the more thoroughly and speedily will digestion ensue. 
 
 The act of chewing is simple and yet important, for if hur- 
 riedly or imperfectly done, the food is in a condition to cause 
 disturbance in the digestive process. Thorough mastication 
 is a necessary introduction to the more complicated changes 
 which occur in the later digestion. 
 
DIGESTION. ' 123 
 
 133. The Teeth. The teeth are attached to the upper and 
 lower maxillary bones by roots which sink into the sockets of 
 the jaws. Each tooth consists of a crown, the visible part, 
 and one or more fangs, buried in the sockets. There are in 
 adults 32 teeth, 16 in each jaw. 
 
 Teeth differ in name according to their form and the uses 
 to which they are specially adapted. Thus, at the front of the 
 jaws, the incisors, or cutting teeth, number eight, two on each 
 side. They have a single root and the crown is beveled behind, 
 presenting a chisel-like edge. The incisors divide the food, and 
 are well developed in rodents, as squirrels, rats, and beavers. 
 
 Next come the canine teeth, or cuspids, two in each jaw, so 
 called from their resemblance to the teeth of dogs and other 
 flesh-eating animals. These teeth have single roots, but their 
 crowns are more pointed than in the incisors. The upper two 
 are often called eye teeth, and the lower two, stomach teeth. 
 Next behind the canines follow, on each side, two bicuspids. 
 Their crowns are broad, and they have two roots. The three 
 hindmost teeth in each jaw are the molars, or grinders. These 
 are broad teeth with four or five points on each, and usually 
 each molar has three roots. 
 
 The last molars are known as the wisdom teeth, as they do 
 not usually appear until the person has reached the " years 
 of discretion." All animals that live on grass, hay, corn, and 
 the cereals generally, have large grinding teeth, as the horse, 
 ox, sheep, and elephant. 
 
 The following table shows the teeth in their order : 
 
 Mo. Bi. Ca. In. In. Ca. Bi. Mo. 
 
 Upper 3212 
 Lower 3212 
 
 i 2 3 = 16 
 
 I 2 
 
 The vertical line indicates the middle of the jaw, and shows 
 that on each side of each jaw there are eight teeth. 
 
124 PRACTICAL PHYSIOLOGY. 
 
 134. Development of the Teeth. The teeth just described are the 
 permanent set, which succeeds the temporary or milk teeth. The 
 latter are twenty in number, ten in each jaw, of which the four in 
 the middle are incisors. The tooth beyond on each side is an eye 
 tooth, and the next two on each side are bicuspids, or premolars. 
 
 The milk teeth appear during the first and second years, and last 
 until about the sixth or seventh year, from which time until the twelfth 
 
 FIG. 48. Temporary and Permanent Teeth together. 
 
 Temporary teeth: A, central incisors; B, lateral incisors; C, canines; D, anterior 
 molars; E, posterior molars. Permanent teeth: F, central incisors; H, lateral 
 incisors; K, canines; L, first bicuspids; M, second biscuspids ; N, first molars. 
 
 or thirteenth year, they are gradually pushed out, one by one, by the 
 permanent teeth. The roots of the milk teeth are much smaller than 
 those of the second set. 
 
 The plan of a gradual succession of teeth is a beautiful provision 
 of nature, permitting the jaws to increase in size, and preserving the 
 relative position and regularity of the successive teeth. 
 
 135. Structure of the Teeth. If we should saw a tooth down 
 through its center we would find in the interior a cavity. This 
 is the pulp cavity, which is filled with the dental pulp, a deli- 
 
DIGESTION. 
 
 125 
 
 FIG. 49. Showing the Principal Organs of the Thorax and Abdomen in situ. (The 
 principal muscles are seen on the left, and superficial veins on the right.) 
 
126 
 
 PRACTICAL PHYSIOLOGY. 
 
 cate substance richly supplied with nerves and blood-vessels, 
 which enter the tooth by small openings at the point of the root. 
 The teeth are thus nourished like other parts of the body. The 
 exposure of the delicate pulp to the air, due to the decay of 
 the dentine, gives rise to the pain of toothache. 
 
 Surrounding the cavity on all sides is the hard substance 
 known as the dentine, or tooth ivory. Outside the dentine of 
 the root is a substance closely resembling bone, called cement. 
 In fact, it is true bone, but lacks the Haversian canals. The 
 root is held in its socket by a dense 
 fibrous membrane which surrounds the 
 cement as the periosteum does bone. 
 The crown of the tooth is not covered 
 by cement, but by the hard enamel, 
 which forms a strong protection for 
 the exposed part. When the teeth are 
 first " cut," the surface of the enamel is 
 coated with a delicate membrane which 
 answers to the Scriptural phrase " the 
 skin of the teeth." This is worn off 
 
 in adult life. 
 FIG. 50. Section of Face. 
 (Showing the parotid and 
 submaxillary glands.) 1 3*>' InSallVatlOn. The thorough 
 
 mixture of the saliva with the food is 
 
 called insalivation. While the food is being chewed, it is 
 moistened with a fluid called saliva, which flows into the 
 mouth from six little glands. There are on each side of the 
 mouth three salivary glands, which secrete the saliva from 
 the blood. The parotid is situated on the side of the face in 
 front of the ear. The disease, common in childhood, during 
 which this gland becomes inflamed and swollen, is known as the 
 " mumps." The submaxillary gland is placed below and to 
 the inner side of the lower jaw, and the sublingual is on the 
 floor of the mouth, between the tongue and the gums. Each 
 
DIGESTION. 127 
 
 gland opens into the mouth by a little duct. These glands 
 somewhat resemble a bunch of grapes with a tube for a stalk. 
 
 The saliva is a colorless liquid without taste or smell. Its 
 principal element, besides water, is a ferment called ptyalin, 
 which has the remarkable property of being able to change 
 starch into a form of cane-sugar, known as maltose. 
 
 Thus, while the food is being chewed, another process is 
 going on by which starch is changed into sugar. The saliva 
 also moistens the food into a mass for swallowing, and aids in 
 speech by keeping the mouth moist. 
 
 The activity of the salivary glands is largely regulated by 
 their abundant supply of nerves. Thus, the saliva flows into 
 the mouth, even at the sight, smell, or thought of food. This 
 is popularly known as "making the mouth water." The flow 
 of saliva may be checked by nervous influences, as sudden 
 terror and undue anxiety. 
 
 Experiment 56. To show the action of saliva on starch. Saliva for 
 experiment may be obtained by chewing a piece of India rubber and collect- 
 ing the saliva in a test tube. Observe that it is colorless and either trans- 
 parent or translucent, and when poured from one vessel to another is 
 glairy and more or less adhesive. Its reaction is alkaline to litmus paper. 
 
 Experiment 57. Make a thin paste from pure starch or arrowroot. 
 Dilute a little of the saliva with five volumes of water, and filter it. This 
 is best done through a filter perforated at its apex by a pin-hole. In this 
 way all air-bubbles are avoided. Label three test tubes A, B, and C. 
 In A, place starch paste; in B, saliva; and in C one volume of saliva and 
 three volumes of starch paste. Place them for ten minutes in a water bath 
 at about 104 Fahrenheit. 
 
 Test portions of all three for a reducing sugar, by means of Fehling's 
 solution or tablets. 1 A and B give no evidence of sugar, while C reduces 
 the Fehling, giving a yellow or red deposit of cuprous oxide. Therefore, 
 starch is converted into a reducing sugar by the saliva. This is done by 
 the ferment ptyalin contained in saliva. 
 
 1 Tablets and other material for Fehling and additional tests for sugar can be pur- 
 chased at a drug store. The practical details of these and other tests which assume 
 some knowledge of chemistry, should be learned from some manual on the subject. 
 
128 PRACTICAL PHYSIOLOGY. 
 
 137. The Pharynx and (Esophagus. The dilated upper 
 part of the alimentary canal is called the pharynx. It forms a 
 blind sac above the level of the mouth. The mouth opens 
 directly into the pharynx, and just above it are two openings 
 leading into the posterior passages of the nose. There are also 
 little openings, one on each side, from which begin the Eusta- 
 chian tubes, which lead upward to the ear cavities. 
 
 The windpipe opens downward from the pharynx, but this 
 communication can be shut off by a little plate or lid of cartilage, 
 the epiglottis. During the act of swallowing, this closes down 
 over the entrance to the windpipe, like a lid, and prevents the 
 food from passing into the air-passages. This tiny trap-door 
 can be seen, by the aid of a mirror, if we open the mouth wide 
 and press down the back of the tongue with the handle of a 
 spoon (Figs. 46, 84, and 85). 
 
 Thus, there are six openings from the pharynx ; the oesopha- 
 gus being the direct continuation from it to the stomach. If we 
 open the mouth before a mirror we see through the fauces the 
 rear wall of the pharynx. In its lining membrane is a large 
 number of glands, the secretion from which during a severe 
 cold may be quite troublesome. 
 
 The oesophagus, or gullet, is a tube about nine inches long, 
 reaching from the throat to the stomach. It lies behind the 
 windpipe, pierces the diaphragm between the chest and abdo- 
 men, and opens into the stomach. It has in its walls muscular 
 fibers, which, by their worm-like contractions, grasp the suc- 
 cessive masses of food swallowed, and pass them along down- 
 wards into the stomach. 
 
 138. Deglutition, or Swallowing. The food, having been 
 well chewed and mixed with saliva, is now ready to be swal- 
 lowed as a soft, pasty mass. The tongue gathers it up and 
 forces it backwards between the pillars of the fauces into the 
 pharynx. 
 
DIGESTION. 
 
 I2 9 
 
 If we place the fingers on the " Adam's apple, " and then 
 pretend to swallow something, we can feel the upper part of the 
 windpipe and the closing of its lid (epiglottis), so as to cover 
 the entrance and prevent the 
 passage of food into the 
 trachea. 
 
 There is only one pathway 
 for the food to travel, and 
 that is down the oesophagus. 
 The slow descent of the food 
 may be seen if a horse or dog 
 be watched while swallowing. 
 Even liquids do not fall or 
 flow down the food passage. 
 Hence, acrobats can drink 
 while standing on their heads, 
 or a horse with its mouth 
 below the level of the oeso- 
 phagus. The food is under 
 the control of the will until it 
 has entered the pharynx ; all 
 the later movements are in- 
 voluntary. 
 
 FIG. 51. A View into the Back Part of 
 the Adult Mouth. (The head is repre- 
 sented as having been thrown back, and 
 the tongue drawn forward.) 
 
 A, B, incisors; C, canine; D, E, bicuspids; 
 F, H, K, molars ; M, anterior pillar of the 
 fauces; N, tonsil; L, uvula; O, upper 
 part of the pha:/nx; P, tongue drawn 
 forward ; R, linear ridge, or raph. 
 
 easily described. It has been 
 
 compared to a bagpipe, which it resembles somewhat, when 
 moderately distended. When empty it is flattened, and in 
 some parts its opposite walls are in contact. 
 
 We may describe the stomach as a pear-shaped bag, with the 
 
 139. The Stomach. The 
 stomach is the most dilated 
 portion of the alimentary 
 canal and the principal organ 
 of digestion. Its form is not 
 
I3O PRACTICAL PHYSIOLOGY. 
 
 large end to the left and the small end to the right. It lies 
 chiefly on the left side of the abdomen, under the diaphragm, 
 and protected by the lower ribs. The fact that the large end 
 of the stomach lies just beneath the diaphragm and the heart, 
 and is sometimes greatly distended on account of indigestion 
 or gas, may cause feelings of heaviness in the chest or palpita- 
 
 D 
 
 FIG. 52. The Stomach. 
 A, cardiac end ; B, pyloric end ; C, lesser curvature ; D, greater curvature. 
 
 tion of the heart. The stomach is subject to greater variations 
 in size than any other organ of the body, depending on its con- 
 tents. Just after a moderate meal it averages about twelve 
 inches in length and four in diameter, with a capacity of about 
 four pints. 
 
 The orifice by which the food enters is called the cardiac 
 opening, because it is near the heart. The other opening, by 
 which the food leaves the stomach, and where the small intes- 
 tine begins, is the pyloric orifice, and is guarded by a kind of 
 valve, known as the pylorus, or gatekeeper. The concave 
 border between the two orifices is called the small curvature, 
 and the convex as the great curvature, of the stomach. 
 
DIGESTION. 
 
 140. Coats of Stomach. The walls of the stomach are formed by 
 four coats, known successively from without as serous, muscular, 
 sub-mucous, and mucous. The outer coat is the serous membrane 
 which lines the abdomen, the peritoneum (note, p. 135). The second 
 coat is muscular, having three sets of involuntary muscular fibers. 
 The outer set runs lengthwise from the cardiac orifice to the pylorus. 
 The middle set encircles all parts of the stomach, while the inner set 
 consists of oblique fibers. The third 
 coat is the sub-mucous, made up of 
 loose connective tissues, and binds the 
 mucous to the muscular coat. Lastly 
 there is the mucous coat, a moist, pink, 
 inelastic membrane, which completely 
 lines the stomach. When the stomach 
 is not distended, the mucous layer is 
 thrown into folds presenting a corru- 
 gated appearance. 
 
 FIG. 53. Pits in the Mucous 
 Membrane of the Stomach, and 
 Openings of the Gastric Glands. 
 (Magnified 20 diameters.) 
 
 141. The Gastric Glands. If we 
 
 were to examine with a hand lens 
 the inner surface of the stomach, 
 we would find it covered with little 
 pits, or depressions, at the bottom of which would be seen dark 
 dots. These dots are the openings of the gastric glands. In 
 the form of fine, wavy tubes, the gastric glands are buried in 
 the mucous membrane, their mouths opening on the surface. 
 When the stomach is empty the mucous membrane is pale, but 
 when food enters, it at once takes on a rosy tint. This is due to 
 the influx of blood from the large number of very minute blood- 
 vessels which are in the tissue between the rows of glands. 
 
 The cells of the gastric glands are thrown into a state of 
 greater activity by the increased quantity of blood supply. 
 As a result, soon after food enters the stomach, drops of fluid 
 collect ait the mouths of the glands and trickle down its walls 
 to mix with the food. Thus these glands produce a large 
 quantity of gastric juice, to aid in the digestion of food. 
 
132 
 
 PRACTICAL PHYSIOLOGY. 
 
 142. Digestion in the Stomach. When the food, thoroughly 
 mixed with saliva, reaches the stomach, the cardiac end of that 
 organ is closed as well as the pyloric 
 valve, and the muscular walls contract 
 on the contents. A spiral wave of motion 
 begins, becoming more rapid as diges- 
 tion goes on. Every particle of food is 
 thus constantly churned about in the 
 stomach and thoroughly mixed with the 
 gastric juice. The action of the juice 
 is aided by the heat of the parts, a 
 temperature of about 99 Fahrenheit. 
 
 The gastric juice is a thin almost 
 colorless fluid with a sour taste and 
 odor. The reaction is distinctly acid, 
 normally due to free hydrochloric acid. 
 Its chief constituents are two ferments 
 called pepsin and rennin, free hydro- 
 chloric acid, mineral salts, and 95 per 
 
 A highly magtifld' view of a C6nt f Water ' 
 
 peptic or gastric gland, which Pepsin, the important constituent of 
 
 is represented as giving off . . 
 
 branches, it shows the col- the gastric juice, has the power, in the 
 Presence of an acid, of dissolving the 
 
 duct D of the gland, from proteid food-Stuffs. Some of which IS 
 
 which two tubes branch off. ,. , 
 
 Each tube is lined with col- converted into what are called peptones, 
 
 umnar epithelial ceils and b ^ so luble and capable of filtering 
 
 there is a minute central pas- 
 
 sage with the "neck" at N. through membranes. The gastric juice 
 
 Here and there are seen other . . . , 
 
 special cells called parietal has no action on starchy foods, neither 
 
 does * act on fats > except to dissolve 
 gastric juice. The principal the albuminous walls of the fat cells. 
 
 cells are represented at C. . ,. . . , -i r 
 
 The fat itself is thus set free in the form 
 
 of minute globules. The whole contents of the stomach now 
 assume the appearance and the consistency of a thick soup, 
 usually of a grayish color, known as chyme. 
 
DIGESTION. 133 
 
 It is well known that "rennet" prepared from the calf's 
 stomach has a remarkable effect in rapidly curdling milk, and 
 this property is utilized in the manufacture of cheese. Now, a 
 similar ferment is abundant in the gastric- juice, and may be 
 called rennin. It causes milk to clot, and does this by so acting 
 on the casein as to make the milk set into a jelly. Mothers 
 are sometimes frightened when their children, seemingly in 
 perfect health, vomit masses of curdled milk. This curdling 
 of the milk is, however, a normal process, and the only note- 
 worthy thing is its rejection, usually due to overfeeding. 
 
 Experiment 58. To show that pepsin and acid are necessary for gastric 
 digestion. Take three beakers, or large test tubes ; label them A, B, C. 
 Put into A water and a few grains of powdered pepsin. Fill B two-thirds 
 full of dilute hydrochloric acid (one teaspoonful to a pint), and fill C two- 
 thirds full of hydrochloric acid and a few grains of pepsin. Put into each 
 a small quantity of well-washed fibrin, and place them all in a water bath at 
 104 Fahrenheit for half an hour. 
 
 Examine them. In A, the fibrin is unchanged ; in , the fibrin is clear 
 and swollen up ; in C, it has disappeared, having first become swollen and 
 clear, and completely dissolved, being finally converted into peptones. 
 Therefore, both acid and ferment are required for gastric digestion. 
 
 Experiment 59. Half fill with dilute hydrochloric acid three large test 
 tubes, labelled A, B, C. Add to each a few grains of pepsin. Boil B, and 
 make C faintly alkaline with sodic carbonate. The alkalinity may be 
 noted by adding previously some neutral litmus solution. Add to each an 
 equal amount a few threads of well-washed fibrin which has been 
 previously steeped for some time in dilute hydrochloric acid, so that it is 
 swollen and transparent. Keep the tubes in a water-bath at about 104 
 Fahrenheit for an hour and examine them at intervals of twenty minutes. 
 
 After five to ten minutes the fibrin in A is dissolved and the fluid begins 
 to be turbid. In B and C there is no change. Even after long exposure 
 to 100 Fahrenheit there is no change in B and C. 
 
 After a variable time, from one to four hours, the contents of 
 "the stomach, which are now called chyme, begin to move on 
 in successive portions into the next part of the intestinal canal. 
 The ring-like muscles of the pylorus relax at intervals to allow 
 
134 PRACTICAL PHYSIOLOGY. 
 
 the muscles of the stomach to force the partly digested mass 
 into the small intestines. This action is frequently repeated, 
 until even the indigestible masses which the gastric juice 
 cannot break down are crowded out of the stomach into the 
 intestines. From three to four hours after a meal the stomach 
 is again quite emptied. 
 
 A certain amount of this semi-liquid mass, especially the 
 peptones, with any saccharine fluids, resulting from the partial 
 conversion of starch or otherwise, is at 
 once absorbed, making its way through 
 the delicate vessels of the stomach into the 
 blood current, which is flowing through the 
 gastric veins to the portal vein of the liver. 
 
 143. The Small Intestine. At the py- 
 loric end of the stomach the alimentary 
 canal becomes again a slender tube called 
 
 .;. ASmallPortion ., . . . , 
 
 of the MUCOUS Mem- the sma11 intestine. This is about twenty 
 brane of the Small in- feet long and one inch in diameter, and is 
 testine. (Vilii are seen divided, for the convenience of description, 
 
 surrounded with the . 
 
 openings of the tubu- mt three P artS 
 
 lar glands.) [Magni- The first 12 inches is called the duode- 
 fied 20 diameters.] num> j nto tn j s portion opens the bile duct 
 
 from the liver with the duct from the pancreas, these having been 
 first united and then entering the intestine as a common duct. 
 
 The next portion of the intestine is called the jejunum, 
 because it is usually empty after death. 
 
 The remaining portion is named the ileum, because of the 
 many folds into which it is thrown. It is the longest part of 
 the small intestine, and terminates in the right iliac region, 
 opening into the large intestine. This opening is guarded by 
 the folds of the membrane forming the ileo-caecal valve, which 
 permits the passage of material from the small to the large 
 intestine, but prevents its backward movement. 
 
DIGESTION. 135 
 
 144. The Coats of the Small Intestine. Like the stomach, the 
 small intestine has four coats, the serous, muscular, sub-mucous, 
 and mucous. The serous is the peritoneum. 1 The muscular consists 
 of an outer layer of longitudinal, and an inner layer of circular fibers, 
 by contraction of which the food is forced along the bowel. The 
 sub-mucous coat is made up of a loose layer of tissue in which the 
 blood-vessels and nerves are distributed. The inner, or mucous, sur- 
 face has a fine, velvety feeling, due to a countless number of tiny, 
 thread-like projections, called villi. They 
 stand up somewhat like the "pile" on 
 velvet. It is through these villi that the 
 digested food passes into the blood. 
 
 The inner coat of a large part of the 
 small intestine is thrown into numerous 
 transverse folds called valvulcz conni- 
 
 ventes. These seem to serve two pur- ,, 
 
 FIG. 56. Sectional View of 
 
 poses, to increase the extent of the surface intestinal Villi. (Black dots 
 of the bowels and to delay mechanically represent the glandular open- 
 the progress of the intestinal contents. in 8 s -) 
 Buried in the mucous layer throughout the length, both of the small 
 and large intestines, are other glands which secrete intestinal fluids. 
 Thus, in the lower part of the ileum there are numerous glands in oval 
 patches known as Peyer's patches. These are very prone to become 
 inflamed and to ulcerate during the course of typhoid fever. 
 
 1 The Peritoneum. The intestines do not lie in a loose mass in the abdominal 
 cavity. Lining the walls of this cavity, just as in a general way, a paper lines 
 the walls of a room, is a delicate serous membrane, called the peritoneum. It 
 envelops, in a greater or less degree, all the viscera in the cavity and forms folds by 
 which they are connected with each other, or are attached to the posterior wall. Its 
 arrangement is therefore very complicated. When the peritoneum comes in con- 
 tact with the large intestine, it passes over it just as the paper of a room would pass 
 over a gas pipe which ran along the surface of the wall, and in passing over it binds 
 it down to the wall of the cavity. The small intestines are suspended from the back 
 wall of the cavity by a double fold of the peritoneum, called the mesentery. The 
 bo'wels are also protected from external cold by several folds of this membrane loaded 
 with fat. This is known as the great omentum. 
 
 The peritoneum, when in health, secretes only enough fluid to keep its surface 
 lubricated so that the bowels may move freely and smoothly on each other and on the 
 other viscera. In disease this fluid may increase in amount, and the abdominal 
 cavity may become greatly distended. This is known as ascites or dropsy. 
 
136 
 
 PRACTICAL PHYSIOLOGY. 
 
 145. The Large Intestine. The large intestine begins in 
 the right iliac region and is about five or six feet long. It is 
 much larger than the small intestine, joining it obliquely at a 
 short distance from its end. A blind pouch, or dilated pocket, 
 is thus formed at the place of junction, called the caecum. A 
 valvular arrangement called the ileo-caecal valve, which is pro- 
 vided with a button-hole slit, forms a kind of movable partition 
 
 between this part of the large 
 intestine and the small intestine. 
 Attached to the caecum is a 
 worm-shaped tube, about the size 
 of a lead pencil, and from three 
 to four inches long, called the 
 vermiform appendix. Its use is 
 unknown. This tube is of great 
 surgical importance, from the fact 
 that it is subject to severe in- 
 flammation, often resulting in an 
 internal abscess, which is always 
 
 A, B, tubular glands seen in vertical sec- 
 
 tion with their orifices at c, opening dangerous and may prove fatal. 
 
 upon the membrane between the villi; Inflammation of the appendix JS 
 D, villus. (Magnified 40 diameters.) ... 
 
 known as appendicitis, a name 
 
 quite familiar on account of the many surgical operations 
 performed of late years for its relief. 
 
 The large intestine passes upwards on the right side as the 
 ascending colon, until the under side of the liver is reached, 
 where it passes to the left side, as the transverse colon, below 
 the stomach. It there turns downward, as the descending 
 colon, and making an S-shaped curve, ends in the rectum. 
 Thus the large intestine encircles, in the form of a horseshoe, 
 the convoluted mass of small intestines. 
 
 Like the small intestine, the large has four coats. The 
 mucous coat, however, has no folds, or villi, but numerous 
 closely set glands, like some of those of the small intestine. 
 
 FIG. 57. Tubular Glands of the 
 Small Intestines. 
 
DIGESTION. 137 
 
 The longitudinal muscular fibers of the large intestine are 
 arranged in three bands, or bundles, which, being shorter than 
 the canal itself, produce a series of bulgings or pouches in its 
 walls. This sacculation of the large bowel is supposed to be 
 designed for delaying the onward flow of its contents, thus 
 allowing more time for the absorption of the liquid material. 
 The blood-vessels and nerves of this part of the digestive canal 
 are very numerous, and are derived from the same sources as 
 those of the small intestine. 
 
 146. The Liver. The liver is a part of the digestive appa- 
 ratus, since it forms the bile, one of the digestive fluids. It is 
 a large reddish-brown organ, situated just below the diaphragm, 
 and on the right side. The liver is the largest gland in the 
 body, and weighs from 50 to 60 ounces. It consists of two 
 lobes, the right and the left, the right being much the larger. 
 The upper, convex surface of the liver is very smooth and 
 even ; but the under surface is irregular, broken by the en- 
 trance and exit of the various vessels which belong to the 
 organ. It is held in its place by five ligaments, four of which 
 are formed by double folds of the peritoneum. 
 
 The thin front edge of the liver reaches just below the 
 bony edge of the ribs; but the dome-shaped diaphragm rises 
 slightly in a horizontal position, and the liver passes up and is 
 almost wholly covered by the ribs. In tight lacing, the liver 
 is often forced downward out from the cover of the ribs, and 
 thus becomes permanently displaced. As a result, other 
 organs in the abdomen and pelvis are crowded together, and 
 also become displaced. 
 
 147. Minute Structure of the Liver. When a small piece 
 of the liver is examined under a microscope it is found to be 
 made up of masses of many-sided cells, each about T ^Vi> of an 
 inch in diameter. Each group of cells is called a lobule. 
 When a single lobule is examined under the microscope it 
 
138 
 
 PRACTICAL PHYSIOLOGY. 
 
 appears to be of an irregular, circular shape, with its cells 
 arranged in rows, radiating from the center to the circumfer- 
 ence. Minute, hair-like channels separate the cells one from 
 another, and unite in one main duct leading from the lobule. 
 
 It is the lobules which give to the 
 liver its coarse, granular appear- 
 ance, when torn across. 
 
 Now there is a large vessel called 
 the portal vein that brings to the 
 liver blood full of nourishing ma- 
 terial obtained from the stomach 
 and intestines. On entering the 
 liver this great vein conducts it- 
 self as if it were an artery. It 
 divides and subdivides into smaller 
 and smaller branches, until, in the 
 form of the tiniest vessels, called 
 capillaries, it passes inward among 
 
 FIG. 58. Diagrammatic Section 
 of a Villus. 
 
 A, layer of columnar epithelium cover- , n , r , 
 
 ing the villus; B, central lacteal of the Cells tO the Very Center of the 
 
 villus; C, unstriped muscular fibers ; heoatic lobules 
 D, goblet cell. 
 
 148. The Bile. We have in the liver, on a grand scale, 
 exactly the same conditions as obtain in the smaller and 
 simpler glands. The thin-walled liver cells take from the 
 blood certain materials which they elaborate into an important 
 digestive fluid, called the bile. 1 This newly manufactured fluid 
 is carried away in little canals, called bile ducts. These minute 
 ducts gradually unite and form at last one main duct, which 
 carries the bile from the liver. This is known as the hepatic 
 duct. It passes out on the under side of the liver, and as 
 
 1 The human bile when fresh is generally of a bright golden red, sometimes of a 
 greenish-yellow color. It becomes quite green when kept, and is alkaline in reaction. 
 When it has been vomited it is distinctly yellow, because of its action on the gastric 
 juice. The bile contains a great deal of coloring matter ; and its chief ingredients are 
 two salts of soda, sodium taurocholate and glycocholate. 
 
DIGESTION. 1 39 
 
 it approaches the intestine, it meets at an acute angle the cystic 
 duct which proceeds from the gall bladder and forms with it 
 the common bile duct. The common duct opens obliquely 
 into the horseshoe bend of the duodenum. 
 
 The cystic duct leads back to the under surface of the 
 liver, where it expands into a sac capable of holding about 
 two ounces of fluid, and is known as the gall bladder. Thus 
 the bile, prepared in the depths of the liver by the liver cells, is 
 carried away by the bile ducts, and may pass directly into the 
 intestines to mix with the food. If, however, digestion is not 
 going on, the mouth of the bile duct is closed, and in that 
 case the bile is carried by the cystic duct to the gall bladder. 
 Here it remains until such time as it is needed. 
 
 149. Blood Supply of the Liver. We must not forget that 
 the liver itself, being a large and important organ, requires con- 
 stant nourishment for the work assigned to it. The blood 
 which is brought to it by the portal vein, being venous, is not 
 fit to nourish it. The work is done by the arterial blood 
 brought to it by a great branch direct from the aorta, known 
 as the hepatic artery, minute branches of which in the form 
 of capillaries, spread themselves around the hepatic lobules. 
 
 The blood, having done its work and now laden with impuri- 
 ties, is picked up by minute veinlets, which unite again and 
 again till they at last form one great trunk called the hepatic 
 vein. This carries the impure blood from the liver, and 
 finally empties it into one of the large veins of the body. 
 
 After the blood has been robbed of its bile-making materials, 
 it is collected by the veinlets that surround the lobules, and 
 finds its way with other venous blood into the hepatic vein. 
 In brief, blood is brought to the liver and distributed through 
 its substance by two distinct channels, the portal vein and the 
 hepatic artery, but it leaves the liver by one distinct channel, 
 the hepatic vein. 
 
140 
 
 PRACTICAL PHYSIOLOGY. 
 
 150. Functions of the Liver. We have thus far studied 
 the liver only as an organ of secretion, whose work is to elabo- 
 rate bile for future use in the process of digestion. This is, 
 however, only one of its functions, and perhaps not the most 
 
 CYSTIC PORTAL HEPATIC ROUND 
 ARTERY VEIN DUCT LIGAMENT 
 
 HEPATIC 
 ARTERY 
 
 FIG. 59. Showing the Relations of the Duodenum and Other Intestinal Organs. 
 (A portion of the stomach has been cut away.) 
 
 important. ,In fact, the functions of the liver are not single, 
 but several. The bile is not wholly a digestive fluid, but 
 it contains, also, materials which are separated from the blood 
 
DIGESTION. 141 
 
 to be cast out of the body before they work mischief. Thus, the 
 liver ranks above all others as an organ of excretion, that is, 
 it separates material of no further use to the body. 
 
 Of the various ingredients of the bile, only the bile salts are 
 of use in the work of digestion, for they act upon the fats in the 
 alimentary canal, and aid somehow in their emulsion and 
 absorption. They appear to be themselves split up into other 
 substances, and absorbed with the dissolved fats into the 
 blood stream again. 
 
 The third function of the liver is very different from those 
 already described. It is found that the liver of an animal well 
 and regularly fed, when examined soon after death, contains a 
 quantity of a carbohydrate substance not unlike starch. This 
 substance, extracted in the form of a white powder, is really an 
 animal starch. It is called glycogen, or liver sugar, and is 
 easily converted into grape sugar. 
 
 The hepatic cells appear to manufacture this glycogen and 
 to store it up from the food brought by the portal blood. It is 
 also thought the glycogen thus deposited and stored up in the 
 liver is little by little changed into sugar. Then, as it is wanted, 
 the liver disposes of this stored-up material, by pouring it, in a 
 state of solution, into the hepatic vein. It is thus steadily 
 carried to the tissues, as their needs demand, to supply them 
 with material to be transformed into heat and energy. 
 
 151. The Pancreas. The pancreas, or sweetbread, is much 
 smaller than the liver. It is a tongue-like mass from six to 
 eight inches long, weighing from three to four ounces, and is 
 often compared in appearance to a dog's tongue. It is some- 
 what the shape of a hammer with the handle running to a 
 point. 
 
 The pancreas lies behind the stomach, across the body, from 
 right to left, with its large head embraced in the horseshoe 
 bend of the duodenum. It closely resembles the salivary glands 
 
142 PRACTICAL PHYSIOLOGY. 
 
 in structure, with its main duct running from one end to the 
 other. This duct at last enters the duodenum in company with 
 the common bile duct. 
 
 The pancreatic juice, the most powerful in the body, is a 
 clear, somewhat viscid, fluid. It has a decided alkaline reaction 
 and is not unlike saliva in many respects. Combined with the 
 bile, this juice acts upon the large drops of fat which pass from 
 the stomach into the duodenum and emulsifies them. This 
 process consists partly in producing a fine subdivision of the 
 particles of fat, called an emulsion, and partly in a chemical 
 decomposition by which a kind of soap is formed. In this way 
 the oils and fats are divided into particles sufficiently minute to 
 permit of their being absorbed into the blood. 
 
 Again, this most important digestive fluid produces on starch 
 an action similar to that of saliva, but much more powerful. Dur- 
 ing its short stay in the mouth, very little starch is changed 
 into sugar, and in the stomach, as we have seen, the action of 
 the saliva is arrested. Now, the pancreatic juice takes up the 
 work in the small intestine and changes the greater part of the 
 starch into sugar. Nor is this all, for it also acts powerfully 
 
 Experiment 60. To show the action of pancreatic juice upon oils or fats. 
 Put two grains of Fairchild's extract of pancreas into a four-ounce bottle. 
 Add half a teaspoonful of warm water, and shake well for a few minutes ; 
 then add a tablespoonful of cod liver oil ; shake vigorously. 
 
 A creamy, opaque mixture of the oil and water, called an emulsion, will 
 result. This will gradually separate upon standing, the pancreatic extract 
 settling in the water at the bottom. When shaken it will again form an 
 emulsion. 
 
 Experiment 61. To show the action of pancreatic juice on starch. Put 
 two tablespoonfuls of smooth starch paste into a goblet, and w r hile still so 
 warm as just to be borne by the mouth, stir into it two grains of the 
 extract of pancreas. The starch paste will rapidly become thinner, and 
 gradually change into soluble starch, in a perfectly fluid solution. Within 
 a few minutes some of the starch is converted through intermediary stages 
 into maltose. Use the Fehling test for sugar. 
 
DIGESTION. 
 
 143 
 
 upon the proteids not acted upon in the stomach, and changes 
 them into peptones that do not differ materially from those 
 resulting from gastric digestion. The remarkable power which 
 the pancreatic juice possesses of acting on all the food-stuffs 
 appears to be due mainly to the presence of a specific element 
 or ferment, known as trypsin. 
 
 152. Digestion in the Small Intestines. After digestion in 
 the stomach has been going on for some time, successive 
 portions of the semi-digested food begin to pass into the duo- 
 denum. The pancreas now takes on new activity, and a copi- 
 ous flow of pancreatic juice is poured along its duct into the 
 
 FIG. 60. Diagrammatic Scheme of Intestinal Absorption. 
 
 A, mesentery; B, lacteals and mesentery glands ; C, veins of intestines; R.C, receptacle of 
 the chyle (receptaculum chyli) ; P.V, portal vein; H.V, hepatic veins; S.V.C, superior 
 vena cava ; R.A, right auricle of the heart ; I.V.C, inferior vena cava. 
 
 'intestines. As the food is pushed along over the common 
 opening of the bile and pancreatic ducts, a great quantity of 
 bile from this reservoir, the gall bladder, is poured into the 
 intestines. These two digestive fluids are now mixed with the 
 chyme, and act upon it in the remarkable manner just described. 
 The inner surface of the small intestine also secretes a liquid 
 called intestinal juice, the precise functions of which are not 
 known. The chyme, thus acted upon by the different digestive 
 fluids, resembles a thick cream, and is now called chyle. The 
 chyle is propelled along the intestine by the worm-like contrac- 
 
144 PRACTICAL PHYSIOLOGY. 
 
 tions of its muscular walls. A function of the bile, not yet 
 mentioned, is to stimulate these movements, and at the same 
 time by its antiseptic properties to prevent putrefaction of the 
 contents of the intestine. 
 
 i53 Digestion in the Large Intestines. Digestion does 
 not occur to any great extent in the large intestines. The food 
 enters this portion of the digestive canal through the ileo- 
 caecal valve, and travels through it slowly. Time is thus given 
 for the fluid materials to be taken up by the blood-vessels of 
 the mucous membrane. The remains of the food now become 
 less fluid, and consist of undigested matter which has escaped 
 the action of the several digestive juices, or withstood their 
 influence. Driven onward by the contractions of the muscular 
 walls, the refuse materials at last reach the rectum, from which 
 they are voluntarily expelled from the body. 
 
 ABSORPTION. 
 
 154. Absorption. While food remains within the alimentary 
 canal it is as much outside of the body, so far as nutrition is 
 concerned, as if it had never been taken inside. To be of any 
 service the food must enter the blood ; it must be absorbed. 
 The efficient agents in absorption are the blood-vessels, the 
 lacteals, and the lymphatics. The process through which the 
 nutritious material is fitted to enter the blood, is called absorp- 
 tion. It is a process not confined, as we shall see, simply to 
 the alimentary canal, but one that is going on in every tissue. 
 
 The vessels by which the process of absorption is carried on 
 are called absorbents. The story, briefly told, is this : certain 
 .food materials that have been prepared to enter the blood, 
 filter through the mucous membrane of the intestinal canal, 
 and also the thin walls of minute blood-vessels and lymphatics, 
 and are carried by these to larger vessels, and at last i^ach the 
 heart, thence to be distributed to the tissues. 
 
DIGESTION. 145 
 
 155. Absorption from the Mouth and Stomach. The lining 
 of the mouth and oesophagus is not well adapted for absorption. 
 That this does occur is shown by the fact that certain poisonous 
 chemicals, like cyanide of potash, if kept in the mouth for a 
 few moments will cause death. While we are chewing and 
 swallowing our food, no doubt a certain amount of water and 
 common salt, together with sugar which has been changed from 
 starch by the action of the saliva, gains entrance to the blood. 
 
 In the stomach, however, absorption takes place with great 
 activity. The semi-liquid food is separated from the enormous 
 supply of blood-vessels in the mucous membrane only by a thin 
 porous partition. There is, therefore, nothing to prevent the 
 exchange taking place between the blood and the food. Water, 
 along with any substances in the food that have become dis- 
 solved, will pass through the partition and enter the blood- 
 current. Thus it is that a certain amount of starch that has 
 been changed into sugar, of salts in solution, of proteids con- 
 verted into peptones, is taken up directly by the blood-vessels 
 of the stomach. 
 
 156. Absorption by the Intestines. Absorption by the 
 intestines is a most active and complicated process. The 
 stomach is really an organ more for the digestion than the 
 absorption of food, while the small intestines are especially 
 constructed for absorption. In fact, the greatest part of absorp- 
 tion is accomplished by the small intestines. They have not 
 only a very large area of absorbing surface, but also structures 
 especially adapted to do this work. 
 
 157. The Lacteals. We have learned in Section 144 that 
 the mucous lining of the small intestines is crowded with mil- 
 lions of little appendages called villi, meaning "tufts of hair." 
 These are only about -fa of an inch long, and a dime will cover 
 more tl^an five hundred of them. Each villus contains a loop of 
 blood-vessels, and another vessel, the lacteal, so called from the 
 
146 PRACTICAL PHYSIOLOGY. 
 
 Latin word lac, milk, because of the milky appearance of the fluid 
 it contains. The villi are adapted especially for the absorp- 
 tion of fat. They dip like the tiniest ringers into the chyle, 
 and the minute particles of fat pass through their cellular 
 covering and gain entrance to the lacteals. The milky material 
 sucked up by the lacteals is not in a proper condition to be 
 poured at once into the blood current. It is, as it were, in too 
 crude a state, and needs some special preparation. 
 
 The intestines are suspended to the posterior wall of the 
 abdomen by a double fold of peritoneum called the mesentery. 
 In this membrane are some 150 glands about the size of an 
 almond, called mesenteric glands. Now the lacteals join these 
 glands and pour in their fluid contents to undergo some impor- 
 tant changes. It is not unlikely that the mesenteric glands 
 may intercept, like a filter, material which, if allowed to enter 
 the blood, would disturb the whole body. Thus, while the 
 glands might suffer, the rest of the body might escape. This 
 may account for the fact that these glands and the lymphatics 
 may be easily irritated and inflamed, thus becoming enlarged 
 and sensitive, as often occurs in the axilla. 
 
 Having been acted upon by the mesenteric glands, and 
 passed through them, the chyle flows onward until it is poured 
 into a dilated reservoir for the chyle, known as the recepta- 
 culum chyli. " This is a sac-like expansion of the lower end of 
 the thoracic duct. Into this receptacle, situated at the level of 
 the upper lumbar vertebrae, in front of the spinal column, are 
 poured, not only the contents of the lacteals, but also of the 
 lymphatic vessels of the lower limbs. 
 
 158. The Thoracic Duct. This duct is a tube from fifteen 
 to eighteen inches long, which passes upwards in front of the 
 spine to reach the base of the neck, where it opens at the 
 junction of the great veins of the left side of the head with 
 those of the left arm. Thus the thoracic duct acts as a kind 
 
DIGESTION. 
 
 147 
 
 of feeding pipe to carry along the nutritive material obtained 
 from the food and to pour it into the blood current. It is to be 
 remembered that the lacteals are in reality lymphatics the 
 lymphatics of the intestines. 
 
 159. The Lymphatics. In nearly every tissue and organ of 
 the body there is a marvelous network of vessels, precisely like 
 the lacteals, called the 
 lymphatics. These are 
 busily at work taking up 
 and making over anew 
 waste fluids or surplus 
 materials derived from 
 the blood and tissues 
 generally. It is esti- 
 mated that the quantity 
 of fluid picked up from 
 the tissues by the lym- 
 phatics and restored 
 daily to the circulation 
 is equal to the bulk of 
 the blood in the body. 
 The lymphatics seem to 
 start out from the part 
 in which they are found, like the rootlets of a plant in the soil. 
 They carry a turbid, slightly yellowish fluid, called lymph, very 
 much like blood without the red corpuscles. 
 
 Now, just as the chyle was not fit to be immediately taken 
 up by the blood, but was passed through the mesenteric glands 
 to be properly worked over, so the lymph is carried to the 
 lymphatic glands, where it undergoes certain changes to fit it 
 for being poured into the blood. Nature, like a careful house- 
 keeper, allows nothing to be wasted that can be of any further 
 service in the animal economy (Figs. 63 and 64). 
 
 FIG. 61. Section of a Lymphatic Gland. 
 
 strong fibrous capsule sending partitions into the 
 gland; B, partitions between the follicles or 
 pouches of the cortical or outer portion ; C, par- 
 titions of the medullary or central portion ; D, E, 
 .masses of protoplasmic matter in the pouches of 
 the gland; F, lymph-vessels which bring lymph to 
 the gland, passing into its center; G, confluence 
 of those leading to the efferent vessel ; H , vessel 
 which carries the lymph away from the gland. 
 
148 PRACTICAL PHYSIOLOGY. 
 
 The lymphatics unite to form larger and larger vessels, and 
 at last join the thoracic duct, except the lymphatics of the 
 right side of the head and chest and right arm. These open 
 by the right lymphatic duct into the venous system on the 
 right side of the neck. 
 
 The whole lymphatic system may be regarded as a necessary 
 appendage to the vascular system (Chapter VII.). It is conven- 
 ient, however, to treat it under the general topic of absorption, 
 in order to complete the history of food digestion. 
 
 160. The Spleen and Other Ductless Glands. With the lym- 
 phatics may be classified, for convenience, a number of organs called 
 ductless or blood glands. Although they apparently prepare mate- 
 rials for use in the body, they have no ducts or canals along which 
 may be carried the result of their work. Again, they are called 
 blood glands because it is supposed they serve some purpose in pre- 
 paring material for the blood. 
 
 The spleen is the largest of these glands. It lies beneath the dia- 
 phragm, and upon the left side of the stomach. It is of a deep red color, 
 full of blood, and is about the size and shape of the palm of the hand. 
 
 The spleen has a fibrous capsule from which partitions pass in- 
 wards, dividing it into spaces by a framework of elastic tissue, with 
 plain muscular fibers. These spaces are filled with what is called 
 the spleen pulp, through which the blood filters from its artery, just 
 as a fluid would pass through a sponge. The functions of the spleen 
 are not known. It appears to take some part in the formation of 
 blood corpuscles. In certain diseases, like malarial fever, it may be- 
 come remarkably enlarged. It may be wholly removed from an 
 animal without apparent injury. During digestion it seems to act as 
 a muscular pump, drawing the blood onwards with increased vigor 
 along its large vein to the liver. 
 
 The thyroid is another ductless gland. It is situated beneath the 
 muscles of the neck on the sides of " Adam's apple " and below it. 
 It undergoes great enlargement in the disease called goitre. 
 
 The thymus is also a blood gland. It is situated around the wind- 
 pipe, behind the upper part of the breastbone. Until about the end 
 of the second year it increases in size, and then it begins gradually to 
 
DIGESTION. 
 
 149 
 
 shrivel away. Like the spleen, the thyroid and thymus glands are sup- 
 posed to work some change in the blood, but what is not clearly known. 
 The suprarenal capsules are two little bodies, one perched on the top 
 of each kidney, in shape not unlike that of a conical hat. Of their 
 functions nothing definite is known. 
 
 EXPERIMENTS. 
 
 The action produced by the tendency of fluids to mix, or become equally 
 diffused in contact with each other, is known as osmosis, a form of mole- 
 cular attraction allied to that of adhesion. The various physical processes 
 by which the products of digestion are transferred from the digestive canal 
 to the blood may be illustrated in a general way by 
 the following simple experiments. 
 
 The student must, however, understand that the 
 necessarily crude experiments of the classroom may 
 not conform in certain essentials to these great pro- 
 cesses conducted in the living body, which they are 
 intended to illustrate and explain. 
 
 Experiment 62. Simple Apparatus for Illustrating 
 Endosmotic Action. " Remove carefully a circular por- 
 tion, about an inch in diameter, of the shell from one 
 end of an egg, which may be done without injuring the 
 membranes, by cracking the shell in small pieces, which 
 are picked off with forceps. A small glass tube is then 
 introduced through an opening in the shell and mem- 
 branes of the other end of the egg, and is secured in a 
 vertical position by wax or plaster of Paris, the tube 
 penetrating the yelk. The egg is then placed in a 
 wine-glass partly filled with water. In the course of a 
 few minutes, the water will have penetrated the ex- 
 posed membrane, and the yelk will rise in the tube." 
 FLINT'S Human Physiology, page 293. 
 
 FIG. 62. 
 
 Experiment 63. Stretch a piece of moist bladder across a glass tube, 
 a common lamp-chimney will do. Into this put a strong saline solution. 
 Now suspend the tube in a wide-mouthed vessel of water. After a short 
 time it will be found that a part of the salt solution has passed through into 
 the water, while a larger amount of water has passed into the tube and 
 raised the height of the liquid within it. 
 
I5O PRACTICAL PHYSIOLOGY. 
 
 161. The Quantity of Food as Affected by Age. The 
 quantity of food required to keep the body in proper condition 
 is modified to a great extent by circumstances. Age, occupa- 
 tion, place of residence, climate, and season, as well as individ- 
 ual conditions of health and disease, are always important 
 factors in the problem. In youth the body is not only growing, 
 but the tissue changes are active. The restless energy and 
 necessary growth at this time of life cannot be maintained with- 
 out an abundance of wholesome food. This food supply for 
 young people should be ample enough to answer the demands 
 of their keen appetite and vigorous digestion. 
 
 In adult life, when the processes of digestion and assimila- 
 tion are active, the amount of food may without harm, be in 
 excess of the actual needs of the body. This is true, how- 
 ever, only so long as active muscular exercise is taken. 
 
 In advanced life the tissue changes are slow, digestion is less 
 active, and the ability to assimilate food is greatly diminished. 
 Growth has ceased, the energy which induced activity is gone, 
 and the proteids are no longer required to build up worn-out 
 tissues. Hence, as old age approaches, the quantity of nitro- 
 genous foods should be steadily diminished. 
 
 Experiment 64. Obtain a sheep's bladder and pour into it a heavy 
 solution of sugar or some colored simple elixir, found at any drug store. 
 Tie the bladder carefully and place it in a vessel containing water. After a 
 while it will be found that an interchange has occurred, water having passed 
 into the bladder and the water outside having become sweet. 
 
 Experiment 65. Make a hole about as big as a five-cent piece in the 
 large end of an egg. That is, break the shell carefully and snip the outer 
 shell membrane, thus opening the space between the outer and inner mem- 
 branes. Now put the egg into a glass of water, keeping it in an upright 
 position by resting on a napkin-ring. There is only the inner shell membrane 
 between the liquid white of the egg (albumen) and the water. 
 
 An interchange takes place, and the water passes towards the albumen. 
 As the albumen does not pass out freely towards the water, the membrane 
 becomes distended, like a little bag at the top of the egg. 
 
DIGESTION. I 5 I 
 
 162. Ill Effects of a too Generous Diet. A generous diet, 
 even of those who take active muscular exercise, should be 
 indulged in only with vigilance and discretion. Frequent sick 
 or nervous headaches, a sense of fullness, bilious attacks, and 
 dyspepsia are some of the after-effects of eating more food 
 than the body actually requires. The excess of food is not 
 properly acted upon by the digestive juices, and is liable to 
 undergo fermentation, and thus to become a source of irritation 
 to the stomach and the intestines. If too much and too rich 
 food be persistently indulged in, the complexion is apt to become 
 muddy, the skin, especially of the face, pale and sallow, and 
 more or less covered with blotches and pimples ; the breath has 
 an unpleasant odor, and the general appearance of the body is 
 unwholesome. 
 
 An excess of any one of the different classes of foods may 
 lead to serious results. Thus a diet habitually too rich in 
 proteids, as with those who eat meat in excess, often over- 
 taxes the kidneys to get rid of the excess of nitrogenous waste, 
 and the organs of excretion are 'not able to rid the tissues of 
 waste products which accumulate in the system. From the 
 blood, thus imperfectly purified, may result kidney troubles 
 and various diseases of the liver and the stomach. 
 
 163. Effect of Occupation. Occupation has an important 
 influence upon the quantity of food demanded for the bodily 
 support. Those who work long and hard at physical labor, 
 need a generous amount of nutritious food. A liberal diet of 
 the cereals and lean meat, especially beef, gives that vigor to 
 the muscles which enables one to undergo laborious and pro- 
 longed physical exertion. On the other hand, those who follow 
 a sedentary occupation do not need so large a quantity of food. 
 Brain-workers who would work well and live long, should not 
 indulge in too generous a diet. The digestion of heavy meals 
 involves a great expenditure of nervous force. Hence, the 
 
152 
 
 PRACTICAL PHYSIOLOGY. 
 
 forces of the brain-worker, being required for mental exertion, 
 should not be expended to an unwarranted extent on the task 
 of digestion. 
 
 164. Effect of Climate. Climate also has a marked influence on 
 the quantity of food demanded by the system. Much more food of 
 all kinds is consumed in cold than in warm climates. The accounts 
 by travelers of the quantity of food used by the inhabitants of the 
 frigid zone are almost beyond belief. A Russian admiral gives an 
 
 instance of a man who, in his pres- 
 ence, ate at a single meal 28 pounds 
 of rice and butter. Dr. Hayes, tte 
 Arctic traveler, states from personal 
 observation that the daily ration of 
 the Eskimos is 1 2 to 15 pounds of 
 meat. With the thermometer rang- 
 ing from 60 to 70 F. below zero, 
 there was a persistent craving for 
 strong animal diet, especially fatty 
 foods. 1 
 
 The intense cold makes such a 
 drain upon the heat-producing power 
 of the body that only food contain- 
 ing the largest proportion of carbon 
 is capable of making up for the loss. 
 
 In tropical countries, on the other hand, the natives crave and subsist 
 
 mainly upon fruits and vegetables. 
 
 165. The Kinds of Food Required. An appetite for plain, 
 well-cooked food is a safe guide to follow. Every person in 
 good health, taking a moderate amount of daily exercise, should 
 have a keen appetite for three meals a day and enjoy them. 
 Food should be both nutritious and digestible. It is nutritious 
 in proportion to the amount of material it furnishes for the 
 nourishment of the tissues. It is digestible in a greater or 
 less degree in respect to the readiness with which it yields to 
 
 1 Nansen emphasizes this point in his recently published work, Farthest North. 
 
 FIG. 63. Lymphatics and Lym- 
 phatic Glands of the Axilla. 
 
DIGESTION. 153 
 
 the action of the digestive fluids, and is prepared to be taken 
 up by the blood. This digestibility depends partly upon the 
 nature of the food in its raw state, partly upon the effect 
 produced upon it by cooking, and to some extent upon its 
 admixture with other foods. Certain foods, as the vegetable 
 albumens, are both nutritious and digestible. A hard-working 
 man may grow strong and maintain vigorous health on most of 
 them, even if deprived of animal food. 
 
 While it is true that the vegetable albumens furnish all that 
 is really needed for the bodily health, animal food of some 
 kind is an economical and useful addition to the diet. Races 
 of men who endure prolonged physical exertion have dis- 
 covered for themselves, without the teaching of science, the 
 great value of meat. Hence the common custom of eating 
 meat with bread and vegetables is a sound one. It is un- 
 doubtedly true that the people of this country, as a rule, eat 
 meat too often and too much at a time. The judicious admix- 
 ture of different classes of foods greatly aids their digestibility. 
 
 The great abundance and variety of food in this country, 
 permit this principle to be put into practice. A variety of 
 mixed foods, as milk, eggs, bread, and meat, are almost inva- 
 riably associated to a greater or less extent at every meal. 
 
 Oftentimes where there is of necessity a sameness of diet, 
 there arises a craving for special articles of food. Thus on 
 long voyages, and during long campaigns in war, there is an 
 almost universal craving for onions, raw potatoes, and other 
 vegetables. 
 
 166. Hints about Meals. On an average, three meals 
 each day, from five to six hours apart, is the proper number 
 for adults. Five hours is by no means too long a time to in- 
 tervene between consecutive meals, for it is not desirable to 
 introduce new food into the stomach, until the gastric diges- 
 tion of the preceding meal has been completed, and until the 
 
154 PRACTICAL PHYSIOLOGY. 
 
 stomach has had time to rest, and is in condition to receive 
 fresh material. The stomach, like other organs, does its work 
 best at regular periods. 1 
 
 Eating out of mealtimes should be strictly avoided, for it 
 robs the stomach of its needed rest. Food eaten when the 
 body and mind are wearied is not well digested. Rest, even 
 for a few minutes, should be taken before eating a full meal. 
 It is well to lie down, or sit quietly and read, fifteen minutes 
 before eating, and directly afterwards, if possible. 
 
 Severe exercise and hard study just after a full meal, are 
 very apt to delay or actually arrest digestion, for after eating 
 heartily, the vital forces of the body are called upon to help the 
 stomach digest its food. If our bodily energies are compelled, 
 in addition to this, to help the muscles or brain, digestion is 
 retarded, and a feeling of dullness and heaviness follows. 
 Fermentative changes, instead of the normal digestive changes, 
 are apt to take place in the food. 
 
 167. Practical Points about Eating. We should not eat 
 for at least two or three hours before going to bed. When we 
 are asleep, the vital forces are at a low ebb, the process of diges- 
 tion is for the time nearly suspended, and the retention of 
 incompletely digested food in the stomach may cause bad 
 dreams and troubled sleep. But in many cases of sleeplessness, 
 a trifle of some simple food, especially if the stomach seems to 
 feel exhausted, often appears to promote sleep and rest. 
 
 1 We should make it a point not to omit a meal unless forced to do so. 
 Children, and even adults, often have the habit of going to school or to work in a 
 hurry, without eating any breakfast. There is almest sure to be a fainting, or " all- 
 gone " feeling at the stomach before another mealtime. This habit is injurious, and 
 sure to produce pernicious results. 
 
 NOTE. The table on the next page shows the results of many experiments to 
 illustrate the time taken for the gastric digestion of a number of the more common 
 solid foods. There are a good many factors of which the table takes no account, 
 such as the interval since the last meal, state of the appetite, amount of work and 
 exercise, method of cooking, and especially the quantity of food. 
 
TABLE SHOWING THE DIGESTIBILITY OF THE MORE 
 COMMON SOLID FOODS. 
 
 FOOD. 
 
 How 
 COOKED. 
 
 TIME IN 
 STOMACH. 
 HOURS. 
 
 FOOD. 
 
 How 
 
 COOKED. 
 
 TIME IN 
 STOMACH. 
 HOURS. 
 
 Apples, sweet and mel- 
 low 
 
 Raw 
 
 ii 
 
 Milk 
 
 Raw 
 
 2i 
 
 Apples, sour and hard . 
 Apple dumpling . . 
 Bass, striped, fresh 
 Beans, pod .... 
 Beef, with salt only 
 " fresh, lean. . . 
 
 u u ti 
 
 " old, hard, salted . 
 Beefsteak 
 
 Boiled 
 Broiled 
 Boiled 
 
 Raw 
 Fried 
 Roasted 
 Boiled 
 Broiled 
 
 4 
 3 
 3 
 4 
 
 2| 
 
 3 
 4 
 3* 
 4| 
 
 ? 
 
 Mutton, fresh . . . 
 
 a u 
 
 
 Oysters, fresh . / . 
 
 U 11 
 
 Parsnips 
 Pig 
 
 Pig's feet, soused . . 
 Pork recently salted 
 
 Broiled 
 Boiled 
 Roasted 
 Raw 
 Roasted 
 Stewed 
 Boiled 
 Roasted 
 Boiled 
 u 
 
 3 
 3 
 
 3i 
 
 4 
 
 34 
 
 3* 
 
 *4 
 
 4 
 i 
 
 ,1 
 
 Beets 
 
 Boiled 
 
 sl 
 
 u 
 
 Fried 
 
 42 
 
 4* 
 
 Bread, corn .... 
 
 Baked 
 
 1 
 
 it 
 
 Raw 
 
 
 " wheat, fresh . 
 Butter . . . 
 
 Melted 
 
 34 
 
 i 
 
 " steaks . . . 
 
 Fried 
 Stewed 
 
 3* 
 
 Cabbage, with vinegar 
 
 it a 
 
 " heads. . . 
 Carrots 
 
 Raw 
 
 Boiled 
 Raw 
 Boiled 
 
 2 
 
 44 
 
 4 
 
 41 
 
 " fat or lean . . 
 Potatoes 
 
 H 
 
 tl 
 
 Roasted 
 Baked 
 Boiled 
 
 5i 
 ^i 
 
 34 
 2 i 
 
 Cheese, old, strong . . 
 Chicken, full-grown 
 " soup . . . 
 Codfish, cured, dried . 
 Corncake . 
 
 Raw 
 
 Fricassee 
 Boiled 
 
 u 
 
 Baked 
 
 34 
 
 2| 
 
 3 
 
 2 
 2f 
 
 Rice 
 Sago 
 Salmon, salted . . . 
 Soup, barley .... 
 " beans 
 
 Boiled 
 
 u 
 u 
 It 
 
 H 
 
 *a 
 
 'f 
 
 4 
 
 4 
 
 Custard 
 
 
 2! 
 
 u beef vegetables 
 
 
 3 
 
 Duck, domestic . . . 
 " wild .... 
 Eggs, fresh, whipped . 
 
 it 
 
 Roasted 
 
 
 
 Raw 
 
 M 
 
 4 
 44 
 4 
 
 2 
 
 bread . . . 
 " marrow bone . 
 " mutton . . . 
 
 
 a 
 H 
 RaVpH 
 
 4 
 
 4 
 
 34 
 ,1 
 
 " soft-boiled . . 
 " hard-boiled . . 
 
 Boiled 
 
 u 
 
 Fried 
 
 3 
 34 
 *i 
 
 Suet, beef, fresh . . 
 " mutton . . . 
 Tapioca 
 
 Boiled 
 u 
 
 2 2 
 
 Si 
 
 44 
 
 Fowl, domestic . . . 
 Gelatin. . . . '. '. 
 
 Boiled 
 Roasted 
 Boiled 
 
 4 
 4 
 
 2^ 
 
 Tripe, soused . . . 
 Trout, salmon, fresh . 
 
 u a 
 
 ti 
 u 
 Fried 
 
 * 
 
 T i 
 
 Goose 
 
 Roasted 
 
 2i 
 
 
 Roasted 
 
 1 ^ 
 
 yl 
 
 Green corn and beans . 
 Hash, meat and vege- 
 tables 
 
 Boiled 
 Warmed 
 
 3l 
 
 2i 
 
 " domestic . . 
 
 a a 
 
 Turnips 
 
 Boiled 
 Roasted 
 Boiled 
 
 2 t 
 
 i 
 
 4 
 *i 
 
 Lamb 
 
 Broiled 
 
 2i 
 
 Veal 
 
 Roasted 
 
 J2 
 
 Liver 
 
 u 
 
 
 
 Fried 
 
 4 
 
 ,1 
 
 Milk 
 
 Boiled 
 
 
 
 RrnilpH 
 
 45 
 
 ti 
 
 
 
 
 
 
 J f 
 
156 PRACTICAL PHYSIOLOGY. 
 
 The state of mind has much to do with digestion. Sudden 
 fear or joy, or unexpected news, may destroy the appetite at 
 once. Let a hungry person be anxiously awaiting a hearty 
 meal, when suddenly a disastrous telegram is brought him ; all 
 appetite instantly disappears, and the tempting food is refused. 
 Hence we should laugh and talk at our meals, and drive away 
 anxious thoughts and unpleasant topics of discussion. 
 
 The proper chewing of the food is an important element in 
 digestion. Hence, eat slowly, and do not "bolt" large frag- 
 ments of food. If imperfectly chewed, it is not readily acted 
 upon by the gastric juice, and often undergoes fermentative 
 changes which result in sour stomach, gastric pain, and other 
 digestive disturbance. 
 
 If we take too much drink with our meals, the flow of the 
 saliva is checked, and digestion is hindered. It is not desir- 
 able to dilute the gastric juice, nor to chill the stomach with a 
 large amount of cold liquid. 
 
 Do not take food and drink too hot or too cold. If they are 
 taken too cold, the stomach is chilled, and digestion delayed. 
 If we drink freely of ice-water, it may require half an hour 
 or more for the stomach to regain its natural heat. 
 
 It is a poor plan to stimulate a flagging appetite with highly 
 spiced food and bitter drinks. An undue amount of pepper, 
 mustard, horseradish, pickles, and highly seasoned meat-sauces 
 may stimulate digestion for the time, but they soon impair it. 
 
 NOTE. The process of gastric digestion was studied many years ago by Dr. Beau- 
 mont and others, in the remarkable case of Alexis St. Martin, a French-Canadian, 
 who met with a gun-shot wound which left a permanent opening into his stomach, 
 guarded by a little valve of mucous membrane. Through this opening the lining of 
 the stomach could be seen, the temperature ascertained, and numerous experiments 
 made as to the digestibility of various kinds of food. 
 
 It was by these careful and convincing experiments that the foundation of our 
 exact knowledge of the composition and action of gastric juice was laid. The 
 modest book in which Dr. Beaumont published his results is still counted among the 
 classics of physiology. The production of artificial fistulae in animals, a method that 
 has since proved so fruitful, was first suggested by his work. 
 
DIGESTION. 
 
 57 
 
 It cannot be too strongly stated that food of a simple char- 
 acter, well cooked and neatly served, is more productive of 
 healthful living than a great variety of fancy dishes which un- 
 duly stimulate the digestive organs, and create a craving for 
 food in excess of the bodily needs. 
 
 168. The Proper Care of the Teeth. It is our duty not 
 only to take the very best care of our teeth, but to retain them 
 as long as possible. Teeth, 
 as we well know, are prone 
 to decay. We may inherit 
 poor and soft teeth: our mode 
 of living may make bad teeth 
 worse. If an ounce of pre- 
 vention is ever worth a pound 
 of cure, it is in keeping the 
 teeth in good order. Bad 
 teeth and toothless gums 
 mean imperfect chewing of 
 the food and, hence, impaired 
 digestion. To attain a health- 
 ful old age, the power of 
 vigorous mastication must be 
 preserved. 
 
 One of the most frequent 
 causes of decay of the teeth 
 is the retention of fragments 
 of food between and around 
 them. The warmth and 
 moisture of the mouth make 
 these matters decompose 
 quickly. The acid thus generated attacks the enamel of the 
 teeth, causing decay of the dentine. Decayed teeth are often 
 the cause of an offensive breath and a foul stomach. 
 
 FIG. 64. Lymphatics on the Inside 
 of the Right Hand. 
 
158 PRACTICAL PHYSIOLOGY. 
 
 To keep the teeth clean and wholesome, they should be 
 thoroughly cleansed at bedtime and in the morning with a 
 soft brush and warm water. Castile soap, and some prepared 
 tooth-powder without grit, should be used, and the brush should 
 be applied on both sides of the teeth. 
 
 The enamel, once broken through, is never renewed. The 
 tooth decays, slowly but surely : hence we must guard against 
 certain habits which injure the enamel, as picking the teeth 
 with pins and needles. We should never crack nuts, crush 
 hard candy, or bite off stout thread with the teeth. Stiff 
 tooth-brushes, gritty and cheap tooth-powders, and hot food 
 and drink, often injure the enamel. 
 
 To remove fragments of food which have lodged between 
 adjacent teeth, a quill or wooden toothpick should be used. 
 Even better than these is the use of surgeon's floss, or silk, 
 which when drawn between the teeth, effectually dislodges 
 retained particles. If the teeth are not regularly cleansed they 
 become discolored, and a hard coating known as tartar accumu- 
 lates on them and tends to loosen them. It is said that after 
 the age of thirty more teeth are lost from this deposit than 
 from all other causes combined. In fact decay and tartar are 
 the two great agents that furnish work for the dentist. 1 
 
 169. Hints about Saving Teeth. We should exercise the greatest 
 care in saving the teeth. The last resort of all is to lose a tooth by 
 extraction. The skilled dentist will save almost anything in the shape 
 of a tooth. 
 
 People are often urged and consent to have a number of teeth 
 extracted which, with but little trouble and expense, might be kept 
 
 1 The teeth of children should be often examined by the dentist, especially from 
 the beginning of the second dentition, at about the sixth year, until growth is com- 
 pleted. In infancy the mother should make it a part of her daily care of the 
 child to secure perfect cleanliness of the teeth. The child thus trained will not, when 
 old enough to rinse the mouth properly or to use the brush, feel comfortable after a 
 meal until the teeth have been cleansed. The habit thus formed is almost sure to be 
 continued through life. 
 
DIGESTION. 1 59 
 
 and do good service for years. The object is to replace the teeth 
 with an artificial set. Very few plates, either partial or entire, are 
 worn with real comfort. They should always be removed before 
 going to sleep, as there is danger of their being swallowed. 
 
 The great majority of drugs have no injurious effect upon the teeth. 
 Some medicines, however, must be used with great care. The acids 
 used in the tincture of iron have a great affinity for the lime salts of 
 the teeth. As this form of iron is often used, it is not unusual to see 
 teeth very badly stained or decayed from the effects of this drug. 
 The acid used in the liquid preparations of quinine may destroy the 
 teeth in a comparatively short time. After taking such medicines the 
 mouth should be thoroughly rinsed with a weak solution of common 
 soda, and the teeth cleansed. 
 
 170. Alcohol and Digestion. The influence of alcoholic 
 drinks upon digestion is of the utmost importance. Alcohol 
 .is not, and cannot be regarded from a physiological point of 
 view as a true food. The reception given to it by the stomach 
 proves this very plainly. It is obviously an unwelcome in- 
 truder. It cannot, like proper foods, be transformed into any 
 element or component of the human body, but passes on, in- 
 nutritious and for the most part unappropriated. Taken even 
 into the mouth, by any person not hardened to its use, its 
 effect is so pungent and burning as at once to demand its rejec- 
 tion. But if allowed to pass into the stomach, that organ im- 
 mediately rebels against its intrusion, and not unfrequently 
 ejects it with indignant emphasis. The burning sensation it 
 produces there, is only an appeal for water to dilute it. 
 
 The stomach meanwhile, in response to this fiery invitation, 
 secretes from its myriad pores its juices and watery fluids, 
 to protect itself as much as possible from the invading liquid. 
 It does not digest alcoholic drinks ; we might say it does not 
 attempt to, because they are not material suitable for digestion, 
 and also because no organ can perform its normal work while 
 smarting under an unnatural irritation. 
 
l6o PRACTICAL PHYSIOLOGY. 
 
 Even if the stomach does not at once eject the poison, it 
 refuses to adopt it as food, for it does not pass along with the 
 other food material, as chyme, into the intestines, but is seized 
 by the absorbents, borne into the veins, which convey it to the 
 heart, whence the pulmonary artery conveys it to the lungs, 
 where its presence is announced in the breath. But wherever 
 alcohol is carried in the tissues, it is always an irritant, every 
 organ in turn endeavoring to rid itself of the noxious material. 
 
 171. Effect of Alcoholic Liquor upon the Stomach. The 
 methods by which intoxicating drinks impair and often ruin 
 digestion are various. We know that a piece of animal food, 
 as beef, if soaked in alcohol for a few hours, becomes hard and 
 tough, the fibers having been compacted together because of 
 the abstraction of their moisture by the alcohol, which has a 
 marvelous affinity for water. In the same way alcohol hardens 
 and toughens animal food in the stomach, condensing its fibers, 
 and rendering it indigestible, thus preventing- the healthful 
 nutrition of the body. So, if alcohol be added to the clear, 
 liquid white of an egg, it is instantly coagulated and trans- 
 formed into hard albumen. As a result of this hardening 
 action, animal food in contact with alcoholic liquids in the 
 stomach remains undigested, and must either be detained there 
 so long as to become a source of gastric disturbance, or else 
 be allowed to pass undigested through the pyloric gate, and 
 then may become a cause of serious intestinal disturbance. 1 
 
 1 " If the amount of alcohol be increased, or the repetition become frequent, some 
 part of it undergoes acid fermentation in the stomach, and acid eructations or vomit- 
 ings occur. With these phenomena are associated catarrh of the stomach and liver 
 with its characteristic symptoms, loss of appetite, feeble digestion, sallowness, 
 mental depression, and headache." JAMES C. WILSON, Professor in the Jefferson 
 Medical College, Philadelphia. 
 
 " Man has recourse to alcohol, not for the minute quantity of energy which may 
 be supplied by itself, but for its powerful influence on the distribution of the energy 
 furnished by other things. That influence is a very complex one." PROFESSOR 
 MICHAEL FOSTER. 
 
DIGESTION. l6l 
 
 This peculiar property of alcohol, its greedy absorption of 
 water from objects in contact with it, acts also by absorbing 
 liquids from the surface of the stomach itself, thus hardening 
 the delicate glands, impairing their ability to absorb the food- 
 liquids, and so inducing gastric dyspepsia. This local injury 
 inflicted upon the stomach by all forms of intoxicants, is serious 
 and protracted. This organ is, with admirable wisdom, so con- 
 structed as to endure a surprising amount of abuse, but it was 
 plainly not intended to thrive on alcoholic liquids. The appli- 
 cation of fiery drinks to its tender surface produces at first 
 a marked congestion of its blood-vessels, changing the natural 
 pink color, as in the mouth, to a bright or deep red. 
 
 If the irritation be not repeated, the lining membrane soon 
 recovers its natural appearance. But if repeated and con- 
 tinued, the congestion becomes more intense, the red color 
 deeper and darker ; the entire surface is the subject of chronic 
 inflammation, its walls are thickened, and sometimes ulcerated. 
 In this deplorable state, the organ is quite unable to perform 
 its normal work of digestion. 1 
 
 172. Alcohol and the Gastric Juice. But still another 
 destructive influence upon digestion appears in the singular 
 fact that alcohol diminishes the power of the gastric juice to 
 do its proper work. Alcohol coagulates the pepsin, which is 
 the dissolving element in this important gastric fluid. A very 
 simple experiment will prove this. Obtain a small quantity of 
 gastric juice from the fresh stomach of a calf or pig, by gently 
 pressing it in a very little water. Pour the milky juice into a 
 clear glass vessel, add a little alcohol, and a white deposit will 
 presently settle to the bottom. This deposit contains the pep- 
 
 1 " When constantly irritated by the direct action of alcoholic drinks, the stomach 
 gradually undergoes lasting structural changes. Its vessels remain dilated and con- 
 gested, its connective tissue becomes excessive, its power of secreting gastric juice 
 diminishes, and its mucous secretions abnormally abundant." H. NEWELL MAR- 
 TIN, late Professor of Physiology in Johns Hopkins University. 
 
1 62 PRACTICAL PHYSIOLOGY. 
 
 sin of the gastric juice, the potent element by which it does its 
 special work of digestion. The ill effect of alcohol upon it is 
 one of the prime factors in the long series of evil results from 
 the use of intoxicants. 
 
 173. The Final Results upon Digestion. We have thus 
 explained three different methods by which alcoholic drinks 
 exercise a terrible power for harm ; they act upon the food so 
 as to render it less digestible; they injure the stomach so as 
 seriously to impair its power of digestion; and they deprive 
 the gastric juice of the one principal ingredient essential to 
 its usefulness. 
 
 Alcoholic drinks forced upon the stomach are a foreign 
 substance ; the stomach treats them as such, and refuses to go 
 on with the process of digestion till it first gets rid of the poi- 
 son. This irritating presence and delay weaken the stomach, 
 so that when proper food follows, the enfeebled organ is ill 
 prepared for its work. After intoxication, there occurs an 
 obvious reaction of the stomach and digestive organs, against 
 the violent and unnatural disturbance. The appetite is extin- 
 guished or depraved, and intense headache racks the frame; 
 the whole system is prostrated, as from a partial paralysis (all 
 these results being the voice of Nature's sharp warning of this 
 
 " Chemical experiments have demonstrated that the action of alcohol on the 
 digestive fluids is to destroy its active principle, the pepsin, thus confirming the 
 observations of physiologists that its use gives rise to the most serious disorders of 
 the stomach and the most malignant aberrations of the entire economy." PRO- 
 FESSOR E. C. YOUMANS, author of standard scientific works. 
 
 " The structural changes induced by the habitual use of alcohol and the action of 
 this agent on the pepsin, seriously impair the digestive power. Hence it is, that 
 those who are habitual consumers of alcoholic fluids suffer from disorders of digestion." 
 ROBERT BARTHOLOW, recently Professor of Materia Medica in the University of 
 Pennsylvania. 
 
 "Alcohol in any appreciable quantity diminishes the solvent power of the gastric 
 fluid so as to interfere with the process of digestion instead of aiding it." PRO- 
 FESSOR W. B. CARPENTER, the eminent English physiologist. 
 
DIGESTION. 163 
 
 great wrong), and a rest of some days is needed before the 
 system fully recovers from the injury inflicted. 
 
 It is altogether an error to suppose the use of intoxicants is 
 necessary or even desirable to promote appetite or digestion. 
 In health, good food and a stomach undisturbed by artificial 
 interference furnish all the conditions required. More than 
 these is harmful. If it may sometimes seem as if alcoholic 
 drinks arouse the appetite and invigorate digestion, we -must not 
 shut our eyes to the fact that this is only a seeming, and that 
 their continued use will inevitably ruin both. In brief, there 
 is no more sure foe to good appetite and normal digestion 
 than the habitual use of alcoholic liquors. 
 
 174. Effect of Alcoholic Drinks upon the Liver. It is to 
 be noted that the circulation of the liver is peculiar ; that the 
 capillaries of the hepatic artery unite in the lobule with those 
 of the portal vein, and thus the blood from both sources is 
 combined ; and that the portal vein brings to the liver the blood 
 from the stomach, the intestines, and the spleen. From the 
 fact that alcohol absorbed from the stomach enters the portal 
 vein, and is borne directly to the liver, we would expect to 
 find this organ suffering the full effects of its presence. And 
 all the more would this be true, because we have just learned 
 that the liver acts as a sort of filter to strain from the blood its 
 impurities. So the liver is especially liable to diseases pro- 
 duced by alcoholics. Post mortems of those who have died 
 while intoxicated show a larger amount of alcohol in the liver 
 than in any other organ. Next to the stomach the liver is an 
 early and late sufferer, and this is especially the case with hard 
 drinkers, and even more moderate drinkers in hot climates. 
 Yellow fever occurring in inebriates is always fatal. 
 
 The effects produced in the liver are not so much functional 
 as organic; that is, not merely a disturbed mode of action, but 
 a destruction of the fabric of the organ itself. From the use 
 
164 PRACTICAL PHYSIOLOGY. 
 
 of intoxicants, the liver becomes at first irritated, then inflamed, 
 and finally seriously diseased. The fine bands, or septa, which 
 serve as partitions between the hepatic lobules, and so maintain 
 the form and consistency of the organ, are the special subjects of 
 the inflammation. Though the liver is at first enlarged, it soon 
 becomes contracted; the secreting cells are compressed, and 
 are quite unable to perform their proper work, which indeed is 
 a very important one in the round of the digestion of food and 
 the purification of the blood. This contraction of the septa 
 in time gives the whole organ an irregularly puckered appear- 
 ance, called from this fact a hob-nail liver or, popularly, gin 
 liver. The yellowish discoloration, usually from retained or 
 perverted bile, gives the disease the medical name of cirrhosis. 1 
 It is usually accompanied with dropsy in the lower extremities, 
 caused by obstruction to the return of the circulation from the 
 parts below the liver. This, disease is always fatal. 
 
 175. Fatty Degeneration Due to Alcohol. Another form 
 of destructive disease often occurs. There is an increase of 
 fat globules deposited in the liver, causing notable enlarge- 
 ment and destroying its function. This is called fatty degener- 
 ation, and is not limited to the liver, but other organs are 
 likely to be similarly affected. In truth, this deposition of fat 
 is a most significant occurrence, as it means actual destruction 
 of the liver tissues, nothing less than progressive death of the 
 organ. This condition always leads to a fatal issue. Still 
 other forms of alcoholic disease of the liver are produced, one 
 being the excessive formation of sugar, constituting what is 
 known as a form of diabetes. 
 
 1 " Cirrhosis of the liver is notoriously frequent among drunkards, and is in fact 
 almost, though not absolutely, confined to them." ROBERT T. EDES, formerly 
 Professor of Materia Medica in Harvard Medical College. 
 
 " Alcohol acts on the liver by producing enlargement of that organ, and a fatty 
 deposit, or 'hob-nailed' liver mentioned by the English writers." PROFESSOR 
 W. B. CARPENTER. 
 
DIGESTION. 165 
 
 176. Effect of Tobacco on Digestion. The noxious in- 
 fluence of tobacco upon the process of digestion is nearly 
 parallel to the effects of alcohol, which it resembles in its irri- 
 tant and narcotic character. Locally, it stimulates the secre- 
 tion of saliva to an unnatural extent, and this excess of secretion 
 diminishes the amount available for normal digestion. 
 
 Tobacco also poisons the saliva furnished for the digestion 
 of food, and thus at the very outset impairs, in both of these 
 particulars, the general digestion, and especially the digestion 
 of the starchy portions of the food. For this reason the 
 amount of food taken, fails to nourish as it should, and either 
 more food must be taken, or the body becomes gradually 
 impoverished. 
 
 The poisonous nicotine, the active element of tobacco, exerts 
 a destructive influence upon the stomach digestion, enfeebling 
 the vigor of the muscular walls of that organ. These effects 
 combined produce dyspepsia, with its weary train of bane- 
 ful results. 
 
 The tobacco tongue never presents the natural, clear, pink 
 color, but rather a dirty yellow, and is usually heavily coated, 
 showing a disordered stomach and impaired digestion. Then, 
 too, there is dryness of the mouth, an unnatural thirst that 
 demands drink. But pure water is stale and flat to such a 
 mouth: something more emphatic is needed. Thus comes the 
 unnatural craving for alcoholic liquors, and thus are taken the 
 first steps on the downward grade. 
 
 " There is no doubt that tobacco predisposes to neuralgia, vertigo, indigestion, 
 and other affections of the nervous, circulatory and digestive organs." W. H. 
 HAMMOND, the eminent surgeon of New York city and formerly Surgeon General, 
 U. S. A. 
 
 Drs. Seaver of Yale University and Hitchcock of Amherst College, instructors of 
 physical education in these two colleges, have clearly demonstrated by personal ex- 
 amination and recorded statistics that the use of tobacco among college students 
 checks growth in weight, height, chest-girth, and, most of all, in lung capacity. 
 
1 66 PRACTICAL PHYSIOLOGY. 
 
 ADDITIONAL EXPERIMENTS. 
 
 Experiment 66. Test a portion of C (Experiment 57) with solution of 
 iodine ; no blue color is obtained, as all the starch has disappeared, having 
 been converted into a reducing sugar, or maltose. 
 
 Experiment 67. Make a thick starch paste ; place some in test tubes, 
 labeled A and B. Keep A for comparison, and to B add saliva, and ex- 
 pose both to about 104 F. A is unaffected, while B soon becomes fluid 
 within two minutes and loses its opalescence; this liquefaction is a 
 process quite antecedent to the saccharifying process which follows. 
 
 Experiment 68. To show the action of gastric juice on milk. Mix 
 two teaspoonfuls of fresh milk in a test tube with a few drops of neutral 
 artificial gastric juice; 1 keep at about 100 F. In a short time the milk 
 curdles, so that the tube can be inverted without the curd falling out. By 
 and by whey is squeezed out of the clot. The curdling of milk by the 
 rennet ferment present in the gastric juice, is quite different from that pro- 
 duced by the " souring of milk," or by the precipitation of caseinogen by 
 acids. Here the casein (carrying with it most of the fats) is precipitated 
 in a neutral fluid. 
 
 Experiment 69. To the test tube in the preceding experiment, add 
 two teaspoonfuls of dilute hydrochloric acid, and keep at 100 F. for two 
 hours. The pepsin in the presence of the acid digests the casein, gradually 
 dissolving it, forming a straw-colored fluid containing peptones. The pep- 
 tonized milk has a peculiar odor and bitter taste. 
 
 Experiment 70. To show the action of rennet on milk. Place milk in 
 a test tube, add a drop or two of commercial rennet, and place the tube in 
 
 i Preparation of Artificial Gastric Juice, (a) Take part of the cardiac end of 
 the pig's stomach, which has been previously opened and washed rapidly in cold 
 water, and spread it, mucous surface upwards, on the convex surface of an inverted 
 capsule. Scrape the mucous surface firmly with the back of a knife blade, and rub 
 up the scrapings in a mortar with fine sand. Add water, and rub up the whole vigor- 
 ously for some time, and filter. The filtrate is an artificial gastric juice. 
 
 (b) From the cardiac end of a pig's stomach detach the mucous membrane in 
 shreds, dry them between folds of blotting-paper, place them in a bottle, and cover 
 them with strong glycerine for several days. The glycerine dissolves the pepsin, and 
 on filtering, a glycerine extract with high digestive properties is obtained. 
 
 These artificial juices, when added to hydrochloric acid of the proper strength, 
 have high digestive powers. 
 
 Instead of (a) or () use the artificial pepsin prepared for the market by the 
 wholesale manufacturers of such goods. 
 
DIGESTION. 167 
 
 a water-bath at about 100 F. The milk becomes solid in a few minutes, 
 forming a curd, and by and by the curd of casein contracts, and presses 
 out a fluid, the whey. 
 
 Experiment 71. Repeat the experiment, but previously boil the rennet. 
 No such result is obtained as in the preceding experiment, because the 
 rennet ferment is destroyed by heat. 
 
 Experiment 72. To show the effect of the pancreatic ferment (tryp- 
 siri) upon albuminous matter. Half fill three test tubes, A, B, C, with one- 
 per-cent solution of sodium carbonate, and add 5 drops of liquor pancrea- 
 ticus, or a few grains of Fairchild's extract of pancreas, in each. Boil B, 
 and make C acid with dilute hydrochloric acid. Place in each tube an 
 equal amount of well-washed fibrin, plug the tubes with absorbent cotton, 
 and place all in a water-bath at about 100 F. 
 
 Experiment 73. Examine from time to time the three test tubes in the 
 preceding experiment. At the end of one, two, or three hours, there is 
 no change in B and C, while in A the fibrin is gradually being eroded, and 
 finally disappears ; but it does not swell up, and the solution at the same 
 time becomes slightly turbid. After three hours, still no change is observ- 
 able in B and C. 
 
 Experiment 74. Filter A, and carefully neutralize the filtrate with very 
 dilute hydrochloric or acetic acid, equal to a precipitate of alkali-albumen. 
 Filter off the precipitate, and on testing the filtrate, peptones are found. 
 The intermediate bodies, the albumoses, are not nearly so readily obtained 
 from pancreatic as from gastric digests. 
 
 Experiment 75. Filter B and C, and carefully neutralize the filtrates. 
 They give no precipitate. No peptones are found. 
 
 Experiment 76. To show the action of pancreatic juice upon the al- 
 buminous ingredients (casein) of milk. Into a four-ounce bottle put two 
 tablespoonf uls of cold water ; add one grain of Fairchild's extract of pan- 
 creas, and as much baking soda as can be taken up on the point of a pen- 
 knife. Shake well, and add four tablespoonf uls of cold, fresh milk. Shake 
 again. 
 
 Now set the bottle into a basin of hot water (as hot as one can bear the 
 hand in), and let it stand for about forty-five minutes. While the milk is 
 digesting, take a small quantity of milk in a goblet, and stir in ten drops 
 or more of vinegar. A thick curd of casein will be seen. 
 
 Upon applying the same test to the digested milk, no curd will be made. 
 This is because the pancreatic ferment (trypsin) has digested the casein 
 into " peptone," which does not curdle. This digested milk is therefore 
 called " peptonized milk." 
 
1 68 PRACTICAL PHYSIOLOGY. 
 
 Experiment 77. To show the action of bile. Obtain from the butcher 
 some ox bile. Note its bitter taste, peculiar odor, and greenish color. It 
 is alkaline or neutral to litmus paper. Pour it from one vessel to another, 
 and note that strings of mucin (from the lining membrane of the gall 
 bladder) connect one vessel with the other. It is best to precipitate the 
 mucin by acetic acid before making experiments; and to dilute the clear 
 liquid with a little distilled water. 
 
 Experiment 78. Test for bile pigments. Place a few drops of bile on 
 a white porcelain slab. With a glass rod place a drop or two of strong 
 nitric acid containing nitrous acid near the drop of bile ; bring the acid 
 and bile into contact. Notice the succession of colors, beginning with 
 green and passing into blue, red, and yellow. 
 
 Experiment 79. To show the action of bile on fats. Mix three tea- 
 spoonfuls of bile with one-half a teaspoonful of almond oil, to which some 
 oleic acid is added. Shake well, and keep the tube in a water-bath at about 
 1 00 F. A very good emulsion is obtained. 
 
 Experiment 80. To show that bile favors filtration and the absorption 
 of fats. Place two small funnels of exactly the same size in a filter stand, 
 and under each a beaker. Into each funnel put a filter paper; moisten 
 the one with water (A) and the other with bile (B). Pour into each an 
 equal volume of almond oil ; cover with a slip of glass to prevent evapora- 
 tion. Set aside for twelve hours, and note that the oil passes through B, 
 but scarcely any through A. The oil filters much more readily through 
 the one moistened with bile, than through the one moistened with water. 
 
 EXPERIMENTS WITH THE FATS. 
 
 Experiment 81. Use olive oil or lard. Show by experiment that they 
 are soluble in ether, chloroform and hot water, but insoluble in water alone. 
 
 Experiment 82. Dissolve a few drops of oil or fat in a teaspoonful of 
 ether. Let a drop of the solution fall on a piece of tissue or rice paper. 
 Note the greasy stain, which does not disappear with the heat. 
 
 Experiment 83. Pour a little cod-liver oil into a test tube; add a few 
 drops of a dilute solution of sodium carbonate. The whole mass becomes 
 white, making an emulsion. 
 
 Experiment 84. Shake up olive oil with a solution of albumen in a 
 test tube. Note that an emulsion is formed. 
 
CHAPTER VII. 
 THE BLOOD AND ITS CIRCULATION. 
 
 177. The Circulation. All the tissues of the body are 
 traversed by exceedingly minute tubes called capillaries, which 
 receive the blood from the arteries, and convey it to the veins. 
 These capillaries form a great system of networks, the meshes 
 of which are filled with the elements of the various tissues. 
 That is, the capillaries are closed vessels, and the tissues lie 
 outside of them, as asbestos packing may be used to en- 
 velop hot-water pipes. The space between the walls of the 
 capillaries and the cells of the tissues is filled with lymph. 
 As the blood flows along the capillaries, certain parts of the 
 plasma of the blood filter through their walls into the lymph, 
 and certain parts of the lymph filter through the cell walls of 
 the tissues and mingle with the blood current. The lymph 
 thus acts as a medium of exchange, in which a transfer of 
 material takes place between the blood in the capillaries and the 
 lymph around them. A similar exchange of material is constantly 
 going on between the lymph and the tissues themselves. 
 
 This, then, we must remember, that in every tissue, so 
 long as the blood flows, and life lasts, this exchange takes place 
 between the blood within the capillaries and the tissues without. 
 
 The stream of blood to the tissues carries to them the 
 material, including the all-important oxygen, with which they 
 build themselves up and do their work. The stream from 
 the tissues carries into the blood the products of certain chem- 
 ical changes which have taken place in these tissues. These 
 products may represent simple waste matter to be cast out or 
 material which may be of use to some other tissue. 
 
I/O PRACTICAL PHYSIOLOGY. 
 
 In brief, the tissues by the help of the lymph live on the 
 blood. Just as our bodies, as a whole, live on the things 
 around us, the food and the air, so do the bodily tissues live 
 on the blood which bathes them in an unceasing current, and 
 which is their immediate air and food. 
 
 178. Physical Properties of Blood. The blood has been 
 called the life of the body from the fact that upon it depends 
 our bodily existence. The blood is so essentially the nutrient 
 
 element that it is called some- 
 times very aptly " liquid flesh." 
 It is a red, warm, heavy, alkaline 
 fluid, slightly salt in taste, and 
 has a somewhat fetid odor. Its 
 color varies from bright red in 
 the arteries and when exposed 
 FIG. 65. Blood Corpuscles of Van- to the air, to various tints from 
 ous Animals. (Magnified to the dark purple to red in the veins. 
 
 The color of the blood is due to 
 A '^T^f?4^^ the colo g constituent of the red 
 
 of acetic acid, showing the central nu- COrpUSCleS, JlCBmOglobin, which is 
 cleus; E bird; F, camel; G, fish; H, feri hter Qr darker ^ ft contains 
 crab or other invertebrate animal. 
 
 more or less oxygen. 
 
 The temperature of the blood varies slightly in different 
 parts of the circulation. Its average heat near the surface is 
 in health about the same, viz. 98^- F. Blood is alkaline, but 
 outside of the body it soon becomes neutral, then acid. The 
 chloride of sodium, or common salt, which the blood contains, 
 gives it a salty taste. In a hemorrhage from the lungs, the 
 sufferer is quick to notice in the mouth the warm and saltish 
 taste. The total amount of the blood in the body was formerly 
 greatly overestimated. It is about T ^ of the total weight of 
 the body, and in a person weighing 156 pounds would amount 
 to about 12 pounds. 
 
THE BLOOD AND ITS CIRCULATION. I /I 
 
 179. Blood Corpuscles. If we put a drop of blood upon a 
 glass slide, and place upon it a cover of thin glass, we can 
 flatten it out until the color almost disappears. If we examine 
 this thin film with a microscope, we see that the blood is not 
 altogether fluid. We find that the liquid part, or plasma, is of 
 a light straw color, and has floating in it a multitude of very 
 minute bodies, called corpuscles. These are of two kinds, the 
 red and the colorless. The former are much more numerous, 
 and have been compared somewhat fancifully to countless 
 myriads of tiny fishes in a swiftly flowing stream. 
 
 180. Red Corpuscles. The red corpuscles are circular 
 disks about ^^^ of an inch in diameter, and double concave 
 in shape. They tend to adhere in long rolls like piles of coins. 
 They are soft, flexible, and elastic, readily squeezing through 
 openings and passages narrower than their pwn diameter, then 
 at once resuming their own shape. 
 
 The red corpuscles are so very small, that rather more than 
 ten millions of them will lie on a surface one inch square. 
 Their number is so enormous that, if all the red corpuscles in 
 a healthy person could be arranged in a continuous line, it is 
 estimated that they would reach four times around the earth ! 
 The principal constituent of these corpuscles, next to water, 
 and that which gives them color is hcemoglobin, a compound 
 containing iron. As all the tissues are constantly absorbing 
 oxygen, and giving off carbon dioxid, a very important office 
 of the red corpuscles is to carry oxygen to all parts of the body. 
 
 181. Colorless Corpuscles. The colorless corpuscles are 
 
 larger than the red, their average diameter being about ^W 
 of an inch. While the red corpuscles are regular in shape, 
 and float about, and tumble freely over one another, the color- 
 less are of irregular shape, and stick close to the glass slide 
 on which they are placed. Again, while the red corpuscles are 
 changed only by some influence from without, as pressure and 
 
172 
 
 PRACTICAL PHYSIOLOGY. 
 
 the like, the colorless corpuscles spontaneously undergo active 
 and very curious changes of form, resembling those of the 
 amoeba, a very minute organism found in stagnant water 
 (Fig. 2). 
 
 The number of both red and colorless corpuscles varies a 
 great deal from time to time. For instance, the number of the 
 latter increases after meals, and quickly diminishes. There is 
 reason to think both kinds of corpuscles are 
 continually being destroyed, their place being 
 supplied by new ones. While the action of the 
 colorless corpuscles is important to the lymph 
 and the chyle, and in the coagulation of the 
 blood, their real function has not been ascer- 
 tained. 
 
 Experiment 85. To show the blood corpuscles. A 
 moderately powerful microscope is necessary to examine 
 blood corpuscles. Let a small drop of blood (easily 
 obtained by pricking the finger with a needle) be placed 
 upon a clean slip of glass, and covered with thin glass, 
 such as is ordinarily used for microscopic purposes. 
 
 The blood is thus spread out into a film, and may be 
 readily examined. At first the red corpuscles will be 
 seen as pale, disk-like bodies floating in the clear fluid. 
 Soon they will be observed to stick to each other by 
 their flattened faces, so as to form rows. The colorless 
 corpuscles are to be seen among the red ones, but are 
 much less numerous. 
 
 FIG. 66. Blood 
 Corpuscles of Man. 
 
 A, red corpuscles ; 
 B, the same seen 
 edgeways; C, the 
 same arranged in 
 rows ; D , white cor- 
 puscles with nuclei. 
 
 182. The Coagulation of the Blood. Blood when shed 
 from the living body is as fluid as water. But it soon becomes 
 viscid, and flows less readily from one vessel to another. Soon 
 the whole mass becomes a nearly solid jelly called a clot. 
 The vessel containing it even can be turned upside down, with- 
 out a drop of blood being spilled. If carefully shaken out, the 
 mass will form a complete mould of the vessel. 
 
THE BLOOD AND ITS CIRCULATION. 
 
 At first the clot includes the whole mass of blood, takes the 
 shape of the vessel in which it is contained, and is of a uniform 
 color. But in a short time a pale yellowish fluid begins to 
 ooze out, and to collect on the surface. The clot gradually 
 shrinks, until at the end of a few hours it is much firmer, and 
 floats in the yellowish fluid. The white corpuscles become 
 entangled in the upper portion of clot, giving it a pale yellow 
 look on the top, known as the buffy coat. As the clot is 
 attached to the sides of the vessel, the 
 shrinkage is more pronounced toward the & 
 center, and thus the surface of the clot is 
 hollowed or cupped, as it is called. This 
 remarkable process is known as coagula- 
 tion, or the clotting of blood ; and the 
 liquid which separates from the clot is FlG . 6;> _ Diagram of 
 called serum. The serum is almost en- Clot with Buffy Coat, 
 tirely free from corpuscles, these being A, serum ; B, cupped upper 
 entangled in the fibrin. 
 
 This clotting of the blood is due to the 
 formation in the blood, after it is with- 
 drawn from the living body, of a sub- 
 stance called fibrin. 1 It is made up of a network of fine white 
 threads, running in every direction through the plasma, and is 
 a proteid substance. The coagulation of the blood may be 
 retarded, and even prevented, by a temperature below 40 F., 
 or a temperature above 120 F. The addition of common salt 
 also prevents coagulation. The clotting of the blood may be 
 hastened by free access to air, by contact with roughened sur- 
 faces, or by keeping it at perfect rest. 
 
 surface of dot ; c, white 
 
 corpuscles in upper layer 
 
 of clot; D, lower por- 
 tion f clot with red cor - 
 
 puscles. 
 
 1 The cause of the clotting of blood is not yet fully understood. Although the 
 process has been thoroughly investigated we have not yet a satisfactory explanation 
 why the circulating blood does not clot in healthy blood-vessels. The ablest physiol- 
 ogists of our day do not, as formerly, regard the process as a so-called vital, but a 
 purely chemical one. 
 
PRACTICAL PHYSIOLOGY. 
 
 This power of coagulation is of the most vital importance. 
 But for this, a very small cut might cause bleeding sufficient 
 to empty the blood-vessels, and death would speedily follow. 
 In slight cuts, Nature plugs up the wound with clots of blood, 
 and thus prevents excessive bleeding. The unfavorable effects 
 of the want of clotting are illustrated in some persons in whom 
 bleeding from even the slightest wounds continues till life is in 
 danger. Such persons are called "bleeders," and surgeons 
 hesitate to perform on them any operation, however trivial, even 
 the extraction of a tooth being often followed by an alarming 
 loss of blood. 
 
 Experiment 86. A few drops of fresh blood may be easily obtained to 
 illustrate important points in the physiology of blood, by tying a string 
 tight around the finger, and piercing it with a clean needle. The blood 
 runs freely, is red and opaque. Put two or three drops of fresh blood on 
 a sheet of white paper, and observe that it looks yellowish. 
 
 Experiment 87. Put two or three drops of fresh blood on a white 
 individual butter plate inverted in a saucer of water. Cover it with an 
 inverted goblet. Take off the cover in five minutes, and the drop has set 
 into a jelly-like mass. Take it off in half an hour, and a little clot will be 
 seen in the watery serum. 
 
 Experiment 88. To show the blood-clot. Carry to the slaughter house 
 a clean, six or eight ounce, wide-mouthed bottle. Fill it with fresh blood. 
 Carry it home with great care, and let it stand over night. The next day 
 the clot will be seen floating in the nearly colorless serum. 
 
 Experiment 89. Obtain a pint of fresh blood; put it into a bowl, and 
 whip it briskly for five minutes, with a bunch of dry twigs. Fine white 
 threads of fibrin collect on the twigs, the blood remaining fluid. This is 
 " whipped " or defibrinated blood, which has lost the power of coagulating 
 spontaneously. 
 
 183. General Plan of Circulation. All the tissues of the 
 body depend upon the blood for their nourishment. It is 
 evident then that this vital fluid must be continually renewed, 
 else it would speedily lose all of its life-giving material. Some 
 
THE BLOOD AND ITS CIRCULATION. 
 
 provision, then, is necessary not only to have the blood 
 renewed in quantity and quality, but also to enable it to carry 
 away impurities. 
 
 So we must have an apparatus of circulation. We need 
 first a central pump from which branch off large pipes, which 
 divide into smaller and smaller branches until they reach 
 the remotest tissues. 
 Through these pipes the 
 blood must be pumped 
 and distributed to the 
 whole body. Then we 
 must have a set of return 
 pipes by which the blood, 
 after it has carried nour- 
 ishment to the tissues, 
 and received waste mat- 
 ters from them, shall be 
 brought back to the cen- 
 tral pumping station, to 
 be used again. We must 
 have also some apparatus 
 to purify the blood from 
 the waste matter it has 
 collected. 
 
 This central pump is 
 
 the heart. The pipes FIG. 68. -Anterior View of the Heart. 
 
 leading from it and grad- A - su P erior vena cava; B| right auride; C| rigl f 
 
 ventricle ; D, left ventricle ; E, left auricle ; F, pul- 
 Ually growing Smaller and moharyvein; H, pulmonary artery; K, aorta; L, 
 
 smaller are the arteries. right subclavian artei r; M, right common carotid 
 
 artery ; N , left common carotid artery. 
 
 The very minute vessels 
 
 into which they are at last subdivided are capillaries. The 
 pipes which convey the blood back to the heart are the veins. 
 Thus, the arteries end in the tissues in fine, hair-like vessels, the 
 capillaries ; and the veins begin in the tissues in exceedingly 
 
1 7 6 
 
 PRACTICAL PHYSIOLOGY. 
 
 small tubes, the capillaries. Of course, there can be no 
 break in the continuity between the arteries and the veins. 
 The apparatus of circulation is thus formed by the heart, the 
 arteries, the capillaries, and the veins. 
 
 184. The Heart. The heart is a pear-shaped, muscular 
 organ roughly estimated as about the size of the person's 
 closed fist. It lies in the chest behind the breastbone, and is 
 lodged between the lobes of the lungs, which partly cover it. 
 In shape the heart resembles a cone, the base of which is 
 directed upwards, a little backwards, and to the right side, 
 while the apex is pointed downwards, forwards, and to the left 
 side. During life, the apex of the heart beats against the 
 chest wall in the space between the fifth and sixth ribs, and 
 about an inch and a half to the left of the middle line of the 
 body. The beating of the heart can be readily felt, heard, and 
 often seen moving the chest wall as it strikes against it. 
 
 The heart does not hang free in the chest, but is suspended 
 and kept in position to some extent by the great vessels con- 
 nected with it. It is enclosed in a 
 bell-shaped covering called the peri- 
 cardium. This is really double, with 
 two layers, one over another. The inner 
 or serous layer covers the external sur- 
 face of the heart, and is reflected back 
 upon itself in order to form, like all 
 membranes of this kind, a sac without 
 
 FIG. 69. Diagram illustrat- , . , , . , , , 
 
 ing the structure of a Se- an opening. 1 The heart is thus covered 
 
 1 Serous Membranes. The serous membranes 
 form shut sacs, of which one portion is applied to the 
 walls of the cavity which it lines ; the other is reflected 
 over the surface of the organ or organs contained in 
 the cavity. The sac is completely closed, so that no 
 communication exists between the serous cavity and 
 the parts in its neighborhood. The various serous 
 membranes are the pleura which envelops the lungs ; 
 
 rous Membrane. 
 A, the viscus, or organ, enveloped 
 by serous membrane; B, layer 
 of membrane lining cavity ; C , 
 membrane reflected to envelop 
 viscus ; D, outer layer of vis- 
 cus, with blood-vessels at E 
 communicating with the gen- 
 eral circulation. 
 
THE BLOOD AND ITS CIRCULATION. 
 
 by the pericardial sac, but is not contained inside its cavity. 
 The space between the two membranes is filled with serous 
 fluid. This fluid permits the heart and the pericardium to glide 
 upon one another with the least possible amount of friction. 1 
 
 The heart is a hollow organ, but the cavity is divided into 
 two parts by a muscular partition forming a left and a right side, 
 between which there is no communication. These two cavities 
 are each divided by a horizontal partition into an upper and a 
 lower chamber. These partitions, however, include a set of 
 valves which open like folding doors between the two rooms. 
 If these doors are closed there are two separate rooms, but if 
 open there is practically only one room. The heart thus has 
 four chambers, two on each side. The two upper chambers are 
 called auricles from their supposed resemblance to the ear. 
 The two lower chambers are called ventricles, and their walls 
 form the chief portion of the muscular substance of the organ. 
 There are, therefore, the right and left auricles, with their thin, 
 soft walls, and the right and left ventricles, with their thick and 
 strong walls. 
 
 185. The Valves of the Heart. The heart is a valvular 
 pump, which works on mechanical principles, the motive power 
 being supplied by the contraction of its muscular fibers. Re- 
 garding the heart as a pump, its valves assume great impor- 
 tance. They consist of thin, but strong, triangular folds of 
 tough membrane which hang down from the edges of the pas- 
 sages into the ventricles. They may be compared to swinging 
 curtains which, by opening only one way, allow the blood to flow 
 
 the pericardium which surrounds the heart ; the peritoneum which invests the 
 viscera of the abdomen, and the arachnoid in the spinal canal and cranial cavity. 
 In health the serous membranes secrete only sufficient fluid to lubricate and keep soft 
 and smooth the opposing surfaces. 
 
 1 A correct idea may be formed of the arrangement of the pericardium around the 
 heart by recalling how a boy puts on and wears his toboggan cap. The pericardium 
 encloses the heart exactly as this cap covers the boy's head. 
 
178 
 
 PRACTICAL PHYSIOLOGY. 
 
 FIG. 70. Lateral Section of the Right Chest. 
 (Showing the relative position of the heart 
 and its great vessels, the oesophagus and 
 trachea.) 
 
 A, inferior constrictor muscle (aids in conveying 
 food down the oesophagus); B, resophagus; C, 
 section of the right bronchus ; D, two right pul- 
 monary veins ; E, great azygos vein crossing 
 oesophagus and right bronchus to empty into 
 the superior vena cava; F, thoracic duct; H, 
 thoracic aorta ; K, lower portion of oesophagus 
 passing through the diaphragm ; L, diaphragm 
 as it appears in sectional view, enveloping the 
 heart; M, inferior vena cava passing through 
 diaphragm and emptying into auricle ; N, right 
 auricle ; O, section of right branch of the pul- 
 monary artery ; P, aorta ; R, superior vena cava ; 
 S, trachea. 
 
 from the auricles to the 
 ventricles, but by instantly 
 folding back prevent its re- 
 turn. 
 
 The valve on the right 
 side is called the tricuspid, 
 because it consists of three 
 little folds which fall over 
 the opening and close it, 
 being kept from falling too 
 far by a number of slender 
 threads called chordae ten- 
 dinae. The valve on the 
 left side, called the mitral, 
 from its fancied resem- 
 blance to a bishop's mitre, 
 consists of two folds which 
 close together as do those 
 of the tricuspid valve. 
 
 The slender cords which 
 regulate the valves are only 
 just long enough to allow 
 the folds to close together, 
 and no force of the blood 
 pushing against the valves 
 can send them farther back, 
 as the cords will not stretch. 
 The harder the blood in 
 the ventricles pushes back 
 against the valves, the 
 tighter the cords become, 
 and the closer the folds are 
 brought together, until the 
 way is completely closed. 
 
THE BLOOD AND ITS CIRCULATION. 
 
 179 
 
 From the right ventricle a large vessel called the pulmonary 
 artery passes to the lungs, and from the left ventricle a large 
 vessel called the aorta arches out to the general circulation of 
 the body. The openings from the ventricles into these vessels 
 are guarded by the semilunar 
 valves. Each valve has three 
 folds, each half-moon -shaped, 
 hence the name semilunar. 
 These valves, when shut, pre- 
 vent any backward flow of the 
 blood on the right side between 
 the pulmonary artery and the 
 right ventricle, and on the left 
 side between the aorta and 
 the left ventricle. 
 
 186. General Plan of the 
 Blood-vessels Connected with 
 the Heart. There are numer- 
 ous blood-vessels connected 
 with the heart, the relative 
 position and the use of which 
 must be understood. The two 
 largest veins in the body, the 
 superior vena cava and the 
 inferior vena cava, open into 
 the right auricle. These two 
 veins bring venous blood from 
 all parts of the body, and pour it into the right auricle, whence 
 it passes into the right ventricle. 
 
 From the right ventricle arises one large vessel, the pul- 
 monary artery, which soon divides into two branches of nearly 
 equal size, one for the right lung, the other for the left. Each 
 branch, having reached its lung, divides and subdivides again 
 
 FIG. 71. Right Cavities of the Heart. 
 
 A, aorta; B, superior vena cava; C, C, right 
 pulmonary veins ; D, inferior vena cava ; 
 E, section of coronary vein ; F, right ven- 
 tricular cavity ; H, posterior curtain of the 
 tricuspid valve ; K, right auricular cavity ; 
 M, fossa ovalis, oval depression, partition 
 between the auricles formed after birth. 
 
ISO PRACTICAL PHYSIOLOGY. 
 
 and again, until it ends in hair-like capillaries, which form a 
 very fine network in every part of the lung. Thus the blood 
 is pumped from the right ventricle into the pulmonary artery, 
 and distributed throughout the two lungs (Figs. 86 and 88). 
 
 We will now turn to the left side of the heart, and notice 
 the general arrangement of its great vessels. Four veins, 
 called the pulmonary veins, open into the left auricle, two 
 from each lung. These veins start from very minute vessels, 
 the continuation of the capillaries of the pulmonary artery. 
 They form larger and larger vessels until they become two 
 large veins in each lung, and pour their contents into the left 
 auricle. Thus the pulmonary artery carries venous blood from 
 the right ventricle to the lungs, as the pulmonary veins carry 
 arterial blood from the lungs to the left auricle. 
 
 From the left ventricle springs the largest arterial trunk in 
 the body, over one-half of an inch in diameter, called the 
 aorta. From the aorta other arteries branch off to carry the 
 blood to all parts of the body, only to be again brought back 
 by the veins to the right side, through the cavities of the 
 ventricles. We shall learn in Chapter VIII. that the main 
 object of pumping the blood into the lungs is to have it puri- 
 fied from certain waste matters which it has taken up in its 
 course through the body, before it is again sent on its journey 
 from the left ventricle. 
 
 187. The Arteries. The blood-vessels are flexible tubes 
 through which the blood is borne through the body. There 
 are three kinds, the arteries, the veins, and the capillaries, 
 and these differ from one another in various ways. 
 
 The arteries are the highly elastic and extensible tubes 
 which carry the pure, fresh blood outwards from the heart to 
 all parts of the body. They may all be regarded as branches 
 of the aorta. After the aorta leaves the left ventricle it rises 
 towards the neck, but soon turns downwards, making a curve 
 known as the arch of the aorta. 
 
THE BLOOD AND ITS CIRCULATION. 
 
 181 
 
 From the arch are given off the arteries which supply the 
 head and arms with blood. These are the two carotid arteries, 
 which run up on each side of the neck to the head, and the 
 two subclavian arteries, which pass beneath the collar bone to 
 the arms. This great arterial 
 trunk now passes down in front 
 of the spine to the pelvis, where 
 it divides into two main branches, 
 which supply the pelvis and the 
 lower limbs. 
 
 The descending aorta, while 
 passing downwards, gives off 
 arteries to the different tissues 
 and organs. Of these branches 
 the chief are the coeliac artery, 
 which subdivides into three great 
 branches, one each to supply 
 the stomach, the liver, and the 
 spleen ; then the renal arteries, 
 one to each kidney; and next two 
 others, the mesenteric arteries, to 
 the intestines. The aorta at last 
 divides into two main branches, FIG. 72. Left Cavities of the Heart, 
 the common iliac arteries, which, A, B, right pulmonary veins ; with s, 
 by their subdivisions, furnish the 
 -arterial vessels for the pelvis and 
 the lower limbs. 
 
 The flow of blood in the 
 arteries is caused by the muscular force of the heart, aided by 
 the elastic tissues and muscular fibers of the arterial walls, and 
 to a certain extent by the muscles themselves. Most of the 
 great arterial trunks lie deep in the fleshy parts of the body ; 
 but their branches are so numerous and become so minute 
 that, with a few exceptions, they penetrate all the tissues of the 
 
 openings of the veins ; E, D, C, aortic 
 valves ; R, aorta ; P, pulmonary artery ; 
 O, pulmonic valves; H, mitral valve;. 
 K, columnae carnceae ; M, right ventric- 
 ular cavity; N, interventricular septum. 
 
1 82 
 
 PRACTICAL PHYSIOLOGY. 
 
 body, so much so, that the point of the finest needle cannot 
 be thrust into the flesh anywhere without wounding one or 
 more little arteries and thus drawing blood. 
 
 188. The Veins. The veins are the blood-vessels which 
 carry the impure blood from the various tissues of the body to 
 the heart. They begin in the minute capillaries at the extremi- 
 ties of the four limbs, and everywhere throughout the body, 
 and passing onwards toward the heart, receive constantly 
 fresh accessions on the way from myriad 
 other veins bringing blood from other 
 wayside capillaries, till the central veins 
 gradually unite into larger and larger 
 vessels until at length they form the two 
 great vessels which open into the right 
 auricle of the heart. 
 
 These two great venous trunks are 
 the inferior vena cava, bringing the 
 blood from the trunk and the lower 
 limbs, and the superior vena cava, 
 
 . the he ad and 
 
 These two large trunks 
 
 FlG -73- 
 
 gitudinai section of a vein, 
 
 showing the valves closed. 
 
 the upper limbs. 
 
 meet ^ they 
 
 The four pulmonary veins, as we have "'learned, carry the 
 arterial blood from the lungs to the left auricle. 
 
 A large vein generally accompanies its corresponding artery, 
 but most veins lie near the surface of the body, just beneath 
 the skin. They may be easily seen under the skin of the hand 
 and forearm, especially in aged persons. If the arm of a 
 young person is allowed to hang down a few moments, and 
 then tightly bandaged above the elbow to retard the return of 
 the blood, the veins become large and prominent. 
 
 The walls of the larger veins, unlike arteries, contain but little 
 of either elastic or muscular tissue ; hence they are thin, and 
 
THE BLOOD AND ITS CIRCULATION. 
 
 when empty collapse. The inner surfaces of many of the veins 
 are supplied with pouch-like folds, or pockets, which act as 
 valves to impede the backward flow of the blood, while they 
 do not obstruct blood flowing forward toward the heart. These 
 valves can be shown by letting the forearm hang down, and 
 sliding the finger upwards over the veins (Fig. 73). 
 
 The veins have no force-pump, like the arteries, to propel 
 their contents towards their destination. The onward flow of 
 the blood in them is due to various 
 causes, the chief being the pressure 
 behind of the blood pumped into 
 the capillaries. Then as the pocket- 
 like valves prevent the backward 
 flow of the blood, the pressure of 
 the various muscles of the body 
 urges along the blood, and thus 
 promotes the onward" flow. 
 
 The forces which drive the blood 
 through the arteries are sufficient to 
 carry the blood on through the capillaries. It is calculated 
 that the onward flow in the capillaries is about ^V to 53 f an 
 inch in a second, while in the arteries the blood current flows 
 about 1 6 inches in a second, and in the great veins about 4 
 inches every second. 
 
 189. The Capillaries. The capillaries are the minute, 
 hair-like tubes, with very thin walls, which form the connection 
 between the ending Of the finest arteries and the beginning of 
 the smallest veins. They are distributed through every tissue 
 of the body, except the epidermis and its products, the epithe- 
 lium, the cartilages, and the substance of the teeth. In fact, 
 the capillaries form a network of the tiniest blood-vessels, so 
 minute as to be quite invisible, at least one-fourth smaller than 
 the finest line visible to the naked eye. 
 
 FIG. 74. The Structure of 
 Capillaries. 
 
 Capillaries of various sizes, showing 
 cells with nuclei. 
 
184 PRACTICAL PHYSIOLOGY. 
 
 The capillaries serve as a medium to transmit the blood from 
 the arteries to the veins ; and it is through them that the blood 
 brings nourishment to the surrounding tissues. In brief, we 
 may regard the whole body as consisting of countless groups 
 of little islands surrounded by ever-flowing streams of blood. 
 The walls of the capillaries are of the most delicate structure, 
 consisting of a single layer of cells loosely connected. Thus 
 there is allowed the most free interchange between the blood 
 and the tissues, through the medium of the lymph. 
 
 The number of the capillaries is inconceivable. Those in 
 the lungs alone, placed in a continuous line, would reach thou- 
 sands of miles. The thin walls of the capillaries are admirably 
 adapted for the important interchanges that take place between 
 the blood and the tissues. 
 
 190. The Circulation of the Blood. It is now well to study 
 the circulation as a whole, tracing the course of the blood from 
 a certain point until it returns to the same point. We may 
 conveniently begin with the portion of blood contained at any 
 moment in the right auricle. The superior and inferior venae 
 cavae are busily filling the auricle with dark, impure blood. 
 When it is full, it contracts. The passage leading to the right 
 ventricle lies open, and through it the blood pours till the 
 ventricle is full. Instantly this begins, in its turn, to contract. 
 The tricuspid valve at once closes, and blocks the way back- 
 ward. The blood is now forced through the open semilunar 
 valves into the pulmonary artery. 
 
 The pulmonary artery, bringing venous* blood, by its alter- 
 nate expansion and recoil, draws the blood along until it 
 reaches the pulmonary capillaries. These tiny tubes surround 
 the air cells of the lungs, and here an exchange takes place. 
 The impure, venous blood here gives up its debris in the shape 
 of carbon dioxid and water, and in return takes up a large 
 amount of oxygen. Thus the blood brought to the lungs by 
 
THE BLOOD AND ITS CIRCULATION. 
 
 I8 5 
 
 the pulmonary arteries leaves the lungs entirely different in 
 character and appearance. This part of the circulation is 
 often called the lesser or pulmonic circulation. 
 
 The four pulmonary veins bring back bright, scarlet blood, 
 and pour it into the left auricle of the heart, whence it passes 
 through the mitral valve into the 
 left ventricle. As soon as the left 
 ventricle is full, it contracts. The 
 mitral valve instantly closes and 
 blocks the passage backward into 
 the auricle ; the blood, having no 
 other way open, is forced through 
 the semilunar valves into the 
 aorta. Now red in color from 
 its fresh oxygen, and laden with 
 nutritive materials, it is distrib- 
 uted by the arteries to the various 
 tissues of the body. Here it gives 
 up its oxygen, and certain nutri- 
 tive materials to build up the 
 tissues, and receives certain prod- 
 ucts of waste, and, changed to a 
 purple color, passes from the cap- 
 illaries into the veins. 
 
 All the veins of the body, except 
 those from the lungs and the heart 
 itself, unite into two large veins, 
 as already described, which pour 
 their contents into the right au- 
 ricle of the heart, and thus the 
 grand round of circulation is con- 
 tinually maintained. This is called the systemic circulation, 
 The whole circuit of the blood is thus divided into two por 
 tions, very distinct from each other. 
 
 FIG. 75. Diagram illustrating the 
 Circulation. 
 
 1, right auricle ; 2, left auricle ; 3, right 
 ventricle ; 4, left ventricle ; 5, vena 
 cava superior; 6, vena cava inferior ; 
 7, pulmonary arteries, 8, lungs; 9, 
 pulmonary veins ; 10, aorta; 11, ali- 
 mentary canal ; 12, liver; 13, hepatic 
 artery; 14, portal vein ; 15, hepatic 
 vein. 
 
1 86 PRACTICAL PHYSIOLOGY. 
 
 191. The Portal Circulation. A certain part of the sys- 
 temic or greater circulation is often called the portal cir- 
 culation, which consists of the flow of the blood from the 
 abdominal viscera through the portal vein and liver to the he- 
 patic vein. The blood brought to the capillaries of the 
 stomach, intestines, spleen, and pancreas is gathered into 
 veins which unite into a single trunk called the portal vein. 
 The blood, thus laden with certain products of digestion, is 
 carried to the liver by the portal vein, mingling with that sup- 
 plied to the capillaries of the same organ by the hepatic artery. 
 From these capillaries the blood is carried by small veins which 
 unite into a large trunk, the hepatic vein, which opens into 
 the inferior vena cava. The portal circulation is thus not an 
 independent system, but forms a kind of loop on the systemic 
 circulation. 
 
 The lymph-current is in a sense a slow and stagnant side 
 stream of the blood circulation ; for substances are constantly 
 passing from the blood-vessels into the lymph spaces, and 
 returning, although after a comparatively long interval, into 
 the blood by the great lymphatic trunks. 
 
 Experiment 90. To illustrate the action of the heart, and how it pumps 
 the blood in only one direction. Take a Davidson or Household rubber 
 syringe. Sink the suction end into water, and press the bulb. As you let 
 the bulb expand, it fills with water ; as you press it again, a valve prevents 
 the water from flowing back, and it is driven out in a jet along the other 
 pipe. The suction pipe represents the veins ; the bulb, the heart ; and 
 the tube end, out of which the water flows, the arteries. 
 
 NOTE. The heart is not nourished by the blood which passes through it. The 
 muscular substance of the heart itself is supplied with nourishment by two little 
 arteries called the coronary arteries, which start from the aorta just above two 
 of the semilunar valves. The blood is returned to the right auricle (not to either of 
 the venae cavae) by the coronary vein. 
 
 The longest route a portion of blood may take from the moment it leaves the left 
 ventricle to the moment it returns to it, is through the portal circulation. The short- 
 est possible route is through the substance of the heart itself. The mean time which 
 the blood requires to make a complete circuit is about 23 seconds. 
 
THE BLOOD AND ITS CIRCULATION. l8/ 
 
 192. The Rhythmic Action of the Heart. To maintain a steady 
 flow of blood throughout the body the action of the heart must be 
 regular and methodical. The heart does not contract as a whole. 
 The two auricles contract at the same time, and this is followed at 
 once by the contraction of the two ventricles. While the ventricles 
 are contracting, the auricles begin to relax, and after the ventricles 
 contract they also relax. Now comes a pause, or rest, after which 
 the auricles and ventricles contract again in the same order as be- 
 fore, and their contsactions are followed by the same pause as before. 
 These contractions and relaxations of the various parts of the heart 
 follow one another so regularly that the result is called the rhythmic 
 action of the heart. 
 
 The average number of beats of the heart, under normal conditions, 
 is from 65 to 75 per minute. Now the time occupied from the instant 
 the auricles begin to contract until after the contraction of the ventri- 
 cles and the pause, is less than a second. Of this time one-fifth is 
 occupied by the contraction of the auricles, two-fifths by the contrac- 
 tion of the ventricles, and the time during which the whole heart is 
 at rest is two-fifths of the period. 
 
 193. Impulse and Sounds of the Heart. The rhythmic 
 action of the heart is attended with various occurrences worthy 
 of note. If the hand be laid flat over the chest wall on the 
 left, between the fifth and sixth ribs, the heart will be felt beat- 
 ing. This movement is known as the beat or impulse of the 
 heart, and can be both seen and felt on the left side. The 
 heart-beat is unusually strong during active bodily exertion, 
 and under mental excitement. 
 
 The impulse of the heart is due to the striking of the lower, 
 tense part of the ventricles the apex of the heart against 
 the chest wall at the moment of their vigorous contraction. 
 It is important for the physician to know the exact place where 
 the heart-beat should be felt, for the heart may be displaced 
 by disease, and its impulse would indicate its new position. 
 
 Sounds also accompany the heart's action. If the ear be 
 applied over the region of the heart, two distinct sounds will 
 
i88 
 
 PRACTICAL PHYSIOLOGY. 
 
 be heard following one another with perfect regularity. Their 
 character may be tolerably imitated by pronouncing the sylla- 
 bles lubb, dup. One sound is heard immediately after the other, 
 then there is a pause, then come the two sounds again. The 
 
 first is a dull, muffled sound, 
 known as the "first sound," 
 followed at once by a shorter 
 and sharper sound, known 
 as the "second sound" of 
 the heart. 
 
 The precise cause of the 
 first sound is still doubtful, 
 but it is made at the moment 
 the ventricles contract. The 
 second sound is, without 
 doubt, caused by the sudden 
 closure of the semilunar 
 valves of the pulmonary art- 
 ery and the aorta, at the 
 moment when the contrac- 
 tion of the ventricles is com- 
 pleted. 
 
 The sounds of the heart 
 are modified or masked by 
 
 FIG. 76. Muscular Fibers of the 
 
 Ventricles. 
 
 A, superficial fibers common to both ventricles ; 
 B, fibers of the left ventricle ; C, deep fibers 
 
 passing upwards toward the base of the heart; blowing "murmurs" when the 
 D, fibers penetrating the left ventricle. 
 
 cardiac orifices or valves are 
 
 roughened, dilated, or otherwise affected as the result of disease. 
 Hence these new sounds may often afford indications of the great- 
 est importance to physicians in the diagnosis of heart-disease. 
 
 194. The Nervous Control of the Heart. The regular, 
 rhythmic movement of the heart is maintained by the action 
 of certain nerves. In various places in the substance of the 
 heart are masses of nerve matter, called ganglia. From these 
 
THE BLOOD AND ITS CIRCULATION. 1 89 
 
 ganglia there proceed, at regular intervals, discharges of nerve 
 energy, some of which excite movement, while others seem to 
 restrain it. The heart would quickly become exhausted if the 
 exciting ganglia had it all their own way, while it would stand 
 still if the restraining ganglia had full sway. The influence of 
 one, however, modifies the other, and the result is a moderate 
 and regular activity of the heart. 
 
 The heart is also subject to other nerve influences, but from 
 outside of itself. Two nerves are connected with the heart, the 
 pneumogastric and the sympathetic (sees. 271 and 265). 
 The former appears to be connected with the restraining gan- 
 glia ; the latter with the exciting ganglia. Thus, if a person 
 were the subject of some emotion which caused fainting, the 
 explanation would be that the impression had been conveyed 
 to the brain, and from the brain to the heart by the pneumo- 
 gastric nerves. The result would be that the heart for an 
 instant ceases to beat. Death would be the result if the nerve 
 influence were so great as to restrain the movements of the 
 heart for any appreciable time. 
 
 Again, if the person were the subject of some emotion by which 
 the heart were beating faster than usual, it would mean that there 
 was sent from the brain to the heart by the sympathetic nerves 
 the impression which stimulated it to increased activity. 
 
 195. The Nervous Control of the Blood-vessels. The tone 
 and caliber of the blood-vessels are controlled by certain vaso- 
 motor nerves, which are distributed among the muscular fibers 
 of the walls. These nerves are governed from a center in the 
 medulla oblongata, a part of the brain (sec. 270). If the 
 nerves are stimulated more than usual, the muscular walls con- 
 tract, and the quantity of the blood flowing through them and 
 the supply to the part are diminished. Again, if the stimulus 
 is less than usual, the vessels dilate, and the supply to the part 
 is increased. 
 
PRACTICAL PHYSIOLOGY. 
 
 Now the vaso-motor center may be excited to increased 
 activity by influences reaching it from various parts of the 
 body, or even from the brain itself. As a result, the nerves 
 are stimulated, and the vessels contract. Again, the normal 
 influence of the vaso-motor center may be suspended for a 
 time by what is known as the inhibitory or restraining effect. 
 The result is that the tone of the blood-vessels becomes dimin- 
 ished, and their channels widen. 
 
 The effect of this power of the nervous system is to give it 
 a certain control over the circulation in particular parts. 
 Thus, though the force of the heart and the general average 
 blood-pressure remain the same, the state of the circulation 
 may be very different in different parts of the body. The im- 
 portance of this local control over the circulation is of the 
 utmost significance. Thus an organ at work needs to be more 
 richly supplied with blood than when at rest. For example, 
 when the salivary glands need to secrete saliva, and the 
 stomach to pour out gastric juice, the arteries that supply 
 these organs are dilated, and so the parts are flushed with an 
 extra supply of blood, and thus are aroused to greater activity. 
 
 Again, the ordinary supply of blood to a part may be les- 
 sened, so that the organ is reduced to a state of inactivity, as 
 occurs in the case of the brain during sleep. We have in the 
 act of blushing a visible example of sudden enlargement of the 
 smaller arteries of the face and neck, called forth by some 
 mental emotion which acts on the vaso-motor center and 
 
 Experiment 91. Hold up the ear of a white rabbit against the light 
 while the animal is kept quiet and not alarmed. The red central artery 
 can be seen coursing along the translucent organ, giving off branches 
 which by subdivision become too small to be separately visible, and the 
 whole ear has a pink color and is warm from the abundant blood flowing 
 through it. Attentive observation will show also that the caliber of the 
 main artery is not constant ; at somewhat irregular periods of a minute or 
 more it dilates and contracts a little. 
 
THE BLOOD AND ITS CIRCULATION. 
 
 RADIAL ARTERY- 
 RADIAL VEIN 
 
 FIG. 77. Some of the Principal Organs of the Chest and Abdomen. (Blood- 
 vessels on the left ; muscles on the right.) 
 
192 
 
 PRACTICAL PHYSIOLOGY. 
 
 diminishes its activity. The reverse condition occurs in the 
 act of turning pale. Then the result of the mental emotion 
 is to cause the vaso-motor nerves to exercise a more powerful 
 control over the capillaries, thereby closing them, and thus 
 
 shutting off the flow of blood. 
 In brief, all over the body, 
 the nervous system, by its vaso- 
 motor centers, is always super- 
 vising and regulating the distri- 
 bution of blood in the body, 
 sending now more and now 
 less to this or that part. 
 
 196. The Pulse. When the 
 FIG. 78. Capillary Blood- Vessels in the finger is placed on any part 
 
 Web of a Frog's Foot, as seen with r , , u , , 
 
 the Microscope f the b d y wher6 an artr y 1S 
 
 located near the surface, as, for 
 
 example, on the radial artery near the wrist, there is felt an 
 intermittent pressure, throbbing with every beat of the heart. 
 This movement, frequently visible to the eye, is the result of 
 the alternate expansion of the artery by the wave of blood, 
 and the recoil of the arterial walls by their elasticity. In other 
 words, it is the wave produced by throwing a mass of blood 
 into the arteries already full. The blood-wave strikes upon 
 the elastic walls of the arteries, causing an increased distention, 
 followed at once by contraction. This regular dilatation and 
 rigidity of the elastic artery answering to the beats of the heart, 
 is known as the pulse. 
 
 The pulse may be easily found at the wrist, the temple, and 
 the inner side of the ankle. The throb of the two carotid 
 arteries may be plainly felt by pressing the thumb and finger 
 backwards on each side of the larynx. The progress of the 
 pulse-wave must not be confused with the actual current of the 
 blood itself. For instance, the pulse-wave travels at the rate 
 
THE BLOOD AND ITS CIRCULATION. 
 
 193 
 
 of about 30 feet a second, and takes about T \^ of a second 
 to reach the wrist, while the blood itself is from 3 to 5 seconds 
 in reaching the same place. 
 
 The pulse-wave may be compared to the wave produced by 
 a stiff breeze on the surface of a slowly moving stream, or the 
 jerking throb sent along a rope when shaken. The rate of the 
 pulse is modified by age, fatigue, posture, exercise, stimulants, 
 disease, and many other circum- 
 stances. At birth the rate is about 
 140 times a minute, in early in- 
 fancy, 120 or upwards, in the 
 healthy adult between 65 and 75, 
 the most common number being 72. 
 In the same individual, the pulse is 
 quicker when standing than when 
 lying down, is quickened by excite- 
 ment, is faster in the morning, 
 and is slowest at midnight. In 
 old age the pulse is faster than 
 in middle life; in children it is quicker than in adults. 
 
 As the pulse varies much in its rate and character in disease, 
 it is to the skilled touch of the physician an invaluable help in 
 the diagnosis of the physical condition of his patient. 
 
 Experiment 92. To find the pulse. Grasp the wrist of a friend, press- 
 ing with three fingers over the radius. Press three fingers over the radius 
 in your own wrist, to feel the pulse. 
 
 Count by a watch the rate of your pulse per minute, and do the same 
 with a friend's pulse. Compare its characters with your own pulse. 
 
 Observe how the character and frequency of the pulse are altered by 
 posture, muscular exercise, a prolonged, sustained, deep inspiration, pro- 
 longed expiration, and other conditions. 
 
 197. Effect of Alcoholic Liquors upon the Organs of Cir- 
 culation. Alcoholic drinks exercise a destructive influence 
 upon the heart, the circulation, and the blood itself. These 
 
 FIG. 79. Circulation in the Cap- 
 illaries, as seen with the Micro- 
 scope. 
 
194 
 
 PRACTICAL PHYSIOLOGY. 
 
 vicious liquids can reach the heart only indirectly, either 
 from the stomach by the portal vein to the liver, and thence to 
 the heart, or else by way of the lacteals, 
 and so to the blood through the thoracic 
 duct. But by either course the route is 
 direct enough, and speedy enough to ac- 
 complish a vast amount of ruinous work. 
 
 The influence of alcohol upon the heart 
 and circulation is produced mainly through 
 the nervous system. The inhibitory nerves, 
 as we have seen, hold the heart in check, 
 exercise a restraining control over it, very 
 much as the reins control an active horse. 
 In health this inhibitory influence is pro- 
 tective and sustaining. But now comes 
 the narcotic invasion of alcoholic drinks, 
 which paralyze the inhibitory nerves, with 
 the others, and at once the uncontrolled 
 heart, like the unchecked steed, plunges 
 on to violent and often destructive results. 
 This action, because it is quicker, has 
 been considered also a stronger action, and 
 the alcohol has therefore been supposed to 
 produce a stimulating effect. But later re- 
 searches lead to the conclusion that the 
 effect of alcoholic liquors is not properly 
 that of a stimulant, but of a narcotic para- 
 FIG. 80.- TWO Principal tyzant, and that while it indeed quickens, 
 Arteries of the Front of it also really weakens the heart's action, 
 the Leg (Anterior Tibial Thig yiew WQuld seem susta i ned by the f act 
 and Dorsalis Pedis). 
 
 that the more the intoxicants are pushed, 
 
 the deeper are the narcotic and paralyzing effects. After hav- 
 ing obstructed the nutritive and reparative functions of the vital 
 fluid for many years, their effects at last may become fatal. 
 
THE BLOOD AND ITS CIRCULATION. 1 95 
 
 This relaxing effect involves not only the heart, but also the 
 capillary system, as is shown in the complexion of the face 
 and the color of the hands. In moderate drinkers the face is 
 only flushed, but in drunkards it is purplish. The flush attend- 
 ing the early stages of drinking is, of course, not the flush of 
 health, but an indication of disease. 1 
 
 198. Effect upon the Heart. This forced overworking of 
 the heart which drives it at a reckless rate, cuts short its periods 
 of rest and inevitably produces serious heart-exhaustion. If 
 repeated and continued, it involves grave changes of the struc- 
 ture of the heart. The heart muscle, endeavoring to compen- 
 sate for the overexertion, may become much thickened, making 
 the ventricles smaller, and so fail to do its duty in properly 
 pumping forward the blood which rushes in from the auricle. 
 Or the heart wall may by exhaustion become thinner, making 
 the ventricles much too large, and unable to send on the cur- 
 rent. In still other cases, the heart degenerates with minute 
 particles of fat deposited in its structures, and thus loses its 
 power to propel the nutritive fluid. All three of these con- 
 ditions involve organic disease of the valves, and all three 
 often produce fatal results. 
 
 199. Effect of Alcohol on the Blood-vessels. Alcoholic 
 liquors injure not only the heart, but often destroy the blood- 
 vessels, chiefly the larger arteries, as the arch of the aorta or 
 
 1 " Alcohol taken in small and single doses, acts almost exclusively on the brain 
 and the blood-vessels of the brain, whereas taken in large and repeated doses its 
 chief effects are always nervous effects. The first effects of alcohol on the function 
 of inhibition are to paralyze the controlling nerves, so that the blood-centers are 
 dilated, and more blood is let into the brain. In consequence of this flushing of the 
 brain, its nerve centers are asked to do more work." DR. T. S. CLOUSTON, Medical 
 Superintendent of the 'Royal Asylum, Edinburgh. 
 
 " Alcoholic drinks prevent the natural changes going on in the blood, and obstruct 
 the nutritive and reparative functions." PROFESSOR E. L. YOUMANS, well-known 
 scientist and author of Class Book of Chemistry. 
 
196 
 
 PRACTICAL PHYSIOLOGY. 
 
 the basilar artery of the brain. In the walls of these vessels 
 may be gradually deposited a morbid product, the result of 
 disordered nutrition, sometimes chalky, sometimes bony, with 
 
 usually a dangerous 
 dilatation of the tube. 
 In other cases the 
 vessels are weak- 
 ened by an unnat- 
 ural fatty deposit. 
 Though these dis- 
 ordered conditions 
 differ somewhat, the 
 morbid results in all 
 are the same. The 
 weakened and stiff- 
 ened arterial walls 
 lose the elastic spring 
 of the pulsing cur- 
 rent. The blood fails 
 to sweep on with its 
 accustomed vigor. 
 At last, owing per- 
 haps to the pressure, 
 against the obstruc- 
 tion of a clot of 
 
 FIG. 81. Showing the Carotid Artery and Jugular 
 Vein on the Right Side, with Some of their Main 
 Branches. (Some branches of the cervical plexus, 
 and the hypoglossal nerve are also shown.) 
 
 some unusual strain of work or passion, 
 
 blood, or perhaps to 
 the enfeebled vessel 
 
 bursts, and death speedily ensues from a form of apoplexy. 
 
 NOTE. " An alcoholic heart loses its contractile and resisting power, both through 
 morbid changes in its nerve ganglia and in its muscle fibers. In typhoid fever, 
 muscle changes are evidently the cause of the heart-enfeeblement ; while in diph- 
 theria, disturbances in innervation cause the heart insufficiency. ' If the habitual 
 use of alcohol causes the loss of contractile and resisting power by impairment of 
 both the nerve ganglia and muscle fibers of the heart, how can it act as a heart 
 tonic?'" DR. ALFRED L. LOOMIS, Professor of Medicine in the Medical Depart- 
 ment of the University of the City of New York. 
 
THE BLOOD AND ITS CIRCULATION. 1 97 
 
 200. Other Results from the Use of Intoxicants. Other 
 disastrous consequences follow the use of intoxicants, and these 
 upon the blood. When any alcohol is present in the circulation, 
 its greed for water induces the absorption of moisture from the 
 red globules of the blood, the oxygen-carriers. In consequence 
 they contract and harden, thus becoming unable to absorb, as 
 theretofore, the oxygen in the lungs. Then, in turn, the oxida- 
 
 FIG 82. The Right Axillary 
 and Brachial Arteries, with 
 Some of their Main Branches. 
 
 tion of the waste matter in the tissues is prevented ; thus the 
 corpuscles cannot convey carbon dioxid from the capillaries, 
 and this fact means that some portion of refuse material, not 
 being thus changed and eliminated, must remain in the blood, 
 rendering it impure and unfit for its proper use in nutrition. 
 Thus, step by step, the use of alcoholics impairs the functions 
 of the blood corpuscles, perverts nutrition, and slowly poisons 
 the blood. 
 
 NOTE. " Destroy or paralyze the inhibitory nerve center, and instantly its con- 
 trolling effect on the heart mechanism is lost, and the accelerating agent, being no 
 longer under its normal restraint, runs riot. The heart's action is increased, the pulse 
 is quickened, an excess of blood is forced into the vessels, and from their becoming 
 engorged and dilated the face gets flushed, all the usual concomitants of a general 
 engorgement of the circulation being the result." DR. GEORGE HARLEY, F.R.S., 
 an eminent English medical author. 
 
PRACTICAL PHYSIOLOGY. 
 
 201. Effect of Tobacco upon the Heart. While tobacco 
 poisons more or less almost every organ of the body, it is upon 
 the heart that it works its most serious wrong. Upon this 
 most important organ its destructive effect is to depress and 
 paralyze. Especially does this apply to the young, whose 
 bodies are not yet knit into the vigor that can brave invasion. 
 
 The nicotine of tobacco acts through the nerves that control 
 the heart's action. Under its baneful influence the motions 
 of the heart are irregular, now feeble and fluttering, now 
 thumping with apparently much force : but both these forms 
 of disturbed action indicate an abnormal condition. Fre- 
 quently there is severe pain in the heart, often dizziness with 
 gasping breath, extreme pallor, and fainting. 
 
 The condition of the pulse is a guide to this state of the 
 heart. In this the physician reads plainly the existence of the 
 " tobacco heart," an affection as clearly known among medical 
 men as croup or measles. There are few conditions more dis- 
 tressing than the constant and impending suffering attending a 
 tumultuous and fluttering heart. It is stated that one in every 
 four of tobacco-users is subject, in some degree, to this dis- 
 turbance. Test examinations of a large number of lads who 
 had used cigarettes showed that only a very small percentage 
 escaped cardiac trouble. Of older tobacco-users there are 
 very few but have some warning of the hazard they invoke. 
 Generally they suffer more or less from the tobacco heart, 
 and if the nervous system or the heart be naturally feeble, 
 they suffer all the more speedily and intensely. 
 
 " The habitual use of alcohol produces a deleterious influence upon the whole 
 economy. The digestive powers are weakened, the appetite is impaired, and the 
 muscular system is enfeebled. The blood is impoverished, and nutrition is imperfect 
 and disordered, as shown by the flabbiness of the skin and muscles, emaciation, or an 
 abnormal accumulation of fat." DR. AUSTIN FLINT, Senior, formerly Professor of 
 the Practice of Medicine in Bellevue Medical College, and author of many standard 
 medical works. 
 
 " The immoderate use of the strong kind of tobacco, which soldiers affect, is often 
 very injurious to them, especially to very young soldiers. It renders them nervous 
 
THE BLOOD AND ITS CIRCULATION. 1 99 
 
 and shaky, gives rise to palpitation, and is a factor in the production of the irritable 
 or so-called " trotting-heart " and tends to impair the appetite and digestion." 
 London Lancet. 
 
 " I never smoke because I have seen the most efficient proofs of the injurious 
 effects of tobacco on the nervous system/' DR. BROWN-SEQUARD, the eminent 
 French physiologist. 
 
 " Tobacco, and especially cigarettes, being a depressant upon the heart, should be 
 positively forbidden." DR. J. M. KEATING, on " Physical Development," in Cyclo- 
 pedia of the Diseases of Children. 
 
 ADDITIONAL EXPERIMENTS. 
 
 Experiment 93. Touch a few drops of blood fresh from the finger, 
 with a strip of dry, smooth, neutral litmus paper, highly glazed to prevent 
 the red corpuscles from penetrating into the test paper. Allow the blood 
 to remain a short time ; then wash it off with a stream of distilled water, 
 when a blue spot upon a red or violet ground will be seen, indicating its 
 alkaline reaction, due chiefly to the sodium phosphate and sodium car- 
 bonate. 
 
 Experiment 94. Place on a glass slide a thin layer of defibrinated 
 blood ; try to read printed matter through it. This cannot be done. 
 
 Experiment 95. To make blood transparent or laky. Place in each of 
 three test tubes two or three teaspoonfuls of defibrinated blood, obtained 
 from Experiment 89, labeled A, B, and C. A is for comparison. To B 
 add five volumes of water, and warm slightly, noting the change of color 
 by reflected and transmitted light. By reflected light it is much darker, 
 it looks almost black ; but by transmitted light it is transparent. Test 
 this by looking at printed matter as in Experiment 94. 
 
 Experiment 96. To fifteen or twenty drops of defibrinated blood in a 
 test tube (labeled D) add five volumes of a lo-per-cent solution of common 
 salt. It changes to a very bright, florid, brick-red color. Compare its color 
 with A, B) and C. It is opaque. 
 
 Experiment 97. Wash away the coloring matter from the twigs (see 
 Experiment 89) with a stream of water until the fibrin becomes quite white. 
 It is white, fibrous, and elastic. Stretch some of the fibers to show their 
 extensibility ; on freeing them, they regain their elasticity. 
 
 Experiment 98. Take some of the serum saved from Experiment 88 
 and note that it does not coagulate spontaneously. Boil a little in a test 
 tube over a spirit lamp, and the albumen will coagulate. 
 
2OO PRACTICAL PHYSIOLOGY. 
 
 Experiment 99. To illustrate in a general "way that blood is really a 
 mass of red bodies which give the red color to the fluid in -which they float. 
 Fill a clean white glass bottle two-thirds full of little red beads, and then fill 
 the bottle full of water. At a short distance the bottle appears to be filled 
 with a uniformly red liquid. 
 
 Experiment 100. To show how blood holds a mineral substance in solu- 
 tion. Put an egg-shell crushed fine, into a glass of water made acid by a 
 teaspoonful of muriatic acid. After an hour or so the egg-shell will dis- 
 appear, having been dissolved in the acid water. In like manner the blood 
 holds various minerals in solution. 
 
 Experiment 101. To hear the sounds of the heart. Locate the heart 
 exactly. Note its beat. Borrow a stethoscope from some physician. 
 Listen to the heart-beat of some friend. Note the sounds of your own 
 heart in the same way. 
 
 Experiment 102. To show how the pulse may be studied. " The move- 
 ments of the artery in the human 
 body as the pulse-wave passes 
 through it may be shown to con- 
 sist in a sudden dilatation, fol- 
 lowed by a slow contraction, 
 interrupted by one or more sec- 
 ondary dilatations. This dem- 
 onstration may be made by 
 pressing a small piece of look- 
 ing-glass about one centimeter 
 square (?- of an inch) upon the 
 wrist over the radial artery, in 
 such a way that with each pulse 
 beat the mirror may be slightly 
 FIG. 83.- How the Pulse may be studied by tilted. If the wrist be now held 
 Pressing a Mirror over the Radial Artery. in such a position that sunlight 
 
 will fall upon the mirror, a spot 
 
 of light will be reflected on the opposite side of the room, and its motion 
 upon the wall will show that the expansion of the artery is a sudden move- 
 ment, while the subsequent contraction is slow and interrupted." BOW- 
 DITCH'S Hints for Teachers of Physiology. 
 
 Experiment 103. To illustrate the effect of muscular exercise in quick- 
 ening the pulse. Run up and down stairs several times. Count the pulse 
 both before and after. Note the effect upon the rate. 
 
THE BLOOD AND ITS CIRCULATION. 2OI 
 
 Experiment 104. 7<? show the action of the elastic walls of the arteries. 
 Take a long glass or metal tube of small caliber. Fasten one end to the 
 faucet of a water-pipe (one in a set bowl preferred) by a very short piece 
 of rubber tube. Turn the water on and off alternately and rapidly, to imi- 
 tate the intermittent discharge of the ventricles. The water will flow from 
 the other end of the rubber pipe in jets, each jet ceasing the moment the 
 water is shut off. 
 
 The experiment will be more successful if the rubber bulb attached to 
 an ordinary- medicine-dropper be removed, and the tapering glass tube be 
 slipped on to the outer end of the rubber tube attached to the faucet. 
 
 Experiment 105. Substitute a piece of rubber tube for the glass tube, 
 and repeat the preceding experiment. Now it will be found that a continu- 
 ous stream flows from the tube. The pressure of water stretches the elas- 
 tic tube, and when the stream is turned off, the rubber recoils on the 
 water, and the intermittent flow is changed into a continuous stream. 
 
 Experiment 106. To illustrate some of the phenomena of circulation. 
 Take a common rubber bulb syringe, of the Davidson, Household, or any 
 other standard make. Attach a piece of rubber tube about six or eight 
 feet long to the delivery end of the syringe. 
 
 To represent the resistance made by the capillaries to the flow of blood, 
 slip the large end of a common glass medicine-dropper into the outer end 
 of the rubber tube. This dropper has one end tapered to a fine point. 
 
 Place the syringe flat, without kinks or bends, on a desk or table. 
 Press the bulb slowly and regularly. The water is thus pumped into the 
 tube in an intermittent manner, and yet it is forced out of the tapering end 
 of the glass tube in a steady flow. 
 
 Experiment 107. Take off the tapering glass tube, or, in the place of 
 one long piece of rubber tube, substitute several pieces of glass tubing 
 connected together by short pieces of rubber tubes. The obstacle to the 
 flow has thus been greatly lessened, and the water flows out in intermittent 
 jets to correspond to the compression of the bulb. 
 
CHAPTER VIII. 
 RESPIRATION. 
 
 202. Nature and Object of Respiration. The blood, as we 
 have learned, not only provides material for the growth and 
 activity of all the tissues of the body, but also serves as a 
 means of removing from them the products of their activity. 
 These are waste products, which if allowed to remain, would 
 impair the health of the tissues. Thus the blood becomes 
 impoverished both by the addition of waste material, and from 
 the loss of its nutritive matter. 
 
 We have shown, in the preceding chapter, how the blood 
 carries to the tissues the nourishment it has absorbed from the 
 food. We have now to consider a new source of nourishment 
 to the blood, viz., that which it receives from the oxygen of 
 the air. We are also to learn one of the methods by which 
 the blood gets rid of poisonous waste matters. In brief, we 
 are to study the set of processes known as respiration, by 
 which oxygen is supplied to the various tissues, and by which 
 the principal waste matters, or chief products of oxidation, 
 are removed. 
 
 Now, the tissues are continually feeding on the life-giving 
 oxygen, and at the same time are continually producing car- 
 bon dioxid and other waste products. In fact, the life of the 
 tissues is dependent upon a continual succession of oxidations 
 and deoxidations. When the blood leaves the tissues, it is 
 poorer in oxygen, is burdened with carbon dioxid, and has had 
 its color changed from bright scarlet to purple red. This is 
 the change from the arterial to venous conditions which has 
 been described in the preceding chapter. 
 
RESPIRATION. 
 
 203 
 
 Now, as we have seen, the change from venous to arterial 
 blood occurs in the capillaries of the lungs, the only means of 
 communication between the pulmonary arteries and the pul- 
 monary veins. The blood in the pulmonary capillaries is sep- 
 arated from the air only by a delicate tissue formed of its own 
 wall and the pulmonary membrane. Hence a gaseous inter- 
 change, the essential step in respiration, very readily takes 
 place between the blood and the air, by which the latter gains 
 moisture and carbon dioxid, and loses its oxygen. These changes 
 in the lungs also restore to the dark blood its rosy tint. 
 
 The only condition absolutely necessary to the purification 
 of the blood is an organ having a delicate 
 membrane, on one side of which is a thin 
 sheet of blood, while the other side is 
 in such contact with the air that an inter- 
 change of gases can readily take place. 
 The demand for oxygen is, however, so 
 incessant, and the accumulation of carbon 
 dioxid is so rapid in every tissue of the 
 human body, that an All-Wise Creator has 
 provided a most perfect but complicated 
 set of machinery to effect this wonderful 
 purification of the blood. 
 
 We are now ready to begin the study 
 of the arrangement and working of the res- 
 piratory apparatus. With its consideration, we complete our 
 view of the sources of supply to the blood, and begin our study 
 of its purification. 
 
 203. The Trachea, or Windpipe. If we look into the mouth 
 of a friend, or into our own with a mirror, we see at the back 
 part an arch which is the boundary line of the mouth proper. 
 There is just behind this a similar limit for the back part of 
 Lhe nostrils. The funnel-shaped cavity beyond, into which 
 
 FIG. 84. 
 
 The Epiglottis. 
 
204 
 
 PRACTICAL PHYSIOLOGY. 
 
 both the mouth and the posterior nasal passages open, is 
 called the pharynx. In its lower part are two openings. ; the 
 trachea, or windpipe, in front, and the oesophagus behind. 
 The trachea is surmounted by a box-like structure of carti- 
 lage, about four and one- 
 half inches long, called the 
 larynx. The upper end 
 of the larynx opens into 
 the pharynx or throat, and 
 is provided with a lid, 
 the epiglottis, which 
 closes under certain cir- 
 cumstances (sees. 137 and 
 349). The larynx contains 
 the organ of voice, and is 
 more fully described in 
 Chapter XII. 
 
 The continuation of the 
 larynx is the trachea, a 
 tube about three-fourths of 
 an inch in diameter, and 
 about four inches long. 
 It extends downwards 
 along the middle line of 
 the neck, where it may 
 
 FIG. 85. Larynx, Trachea, and the Bronchi. 
 (Front view.) 
 
 A, epiglottis ; B, thyroid cartilage ; C, cricoid- 
 thyroid membrane, connecting with the cricoid 
 cartilage below, all forming the larynx ; D, one 
 of the rings of the trachea. 
 
 readily be felt in front, 
 below the Adam's apple. 
 
 The walls of the wind- 
 pipe are strengthened by 
 a series of cartilaginous 
 rings, each somewhat the shape of a horseshoe or like the letter 
 C, being incomplete behind, where they come in contact with 
 the oesophagus. Thus the trachea, while always open for the 
 passage of air, admits of the distention of the food-passage. 
 
RKSl'l RATION. 
 
 205 
 
 204. The Bronchial Tubes. The lower end of the wind- 
 pipe is just behind the upper part of the sternum, and there it 
 divides into two branches, called bronchi. Each branch enters 
 the lung of its own side, and breaks up into a great number of 
 
 FIG. 86. Relative Position of the Lungs, Heart, and its Great Vessels, 
 
 A, left ventricle ; B, right ventricle; C, left auricle; D, right auricle; E. superior vena 
 cava; F, pulmonary artery; G, aorta; H , arch of the aorta ; K, innominate artery ; 
 L, right common carotid artery; M, right subclavian artery; N, thyroid cartilage 
 forming upper portion of the larynx ; O, trachea. 
 
 smaller branches, called bronchial tubes. These divide into 
 smaller tubes, which continue subdividing till the whole lung 
 is penetrated by the branches, the extremities of which are 
 extremely minute. To all these branches the general name of 
 bronchial tubes is given. The smallest are only about one- 
 fiftieth of an inch in diameter. 
 
2O6 
 
 PRACTICAL PHYSIOLOGY. 
 
 Now the walls of the windpipe, and of the larger bronchial 
 tubes would readily collapse, and close the passage for air, 
 but for a wise precaution. The horseshoe-shaped rings of car- 
 tilage in the trachea and the plates of cartilage in the bronchial 
 tubes keep these passages open. Again, these air passages have 
 elastic fibers running the length of the tubes, which allow them 
 to stretch and bend readily with the movements of the neck. 
 
 205. The Cilia of the Air Passages. The inner surfaces 
 of the windpipe and bronchial tubes are lined with mucous 
 
 membrane, continuous with that of 
 the throat, the mouth, and the nostrils, 
 the secretion from which serves to 
 keep the parts moist. 
 
 Delicate, hair-like filaments, not un- 
 like the pile on velvet, called cilia, 
 spring from the epithelial lining of 
 the air tubes. Their constant wavy 
 movement is always upwards and out- 
 wards, towards the mouth. Thus any 
 excessive secretion, as of bronchitis 
 or catarrh, is carried upwards, and 
 finally expelled by coughing. In this 
 way, the lungs are kept quite free 
 
 'its Divisions and"subdiAdsion7. from particles of foreign matter de- 
 (Showing groups of air cells at rived from the air. Otherwise we 
 
 the termination of minute bron- fa M ff and ft be j d 
 chial tubes.) 
 
 from the accumulation of mucus and 
 
 dust in the air passages. Thus these tiny cilia act as dusters 
 which Nature uses to keep the air tubes free and clean (Fig. 5). 
 
 206. The Lungs. The lungs, the organs of respiration, 
 are two pinkish gray structures of a light, spongy appearance, 
 that fill the chest cavity, except the space taken up by the 
 heart and large vessels. Between the lungs are situated 
 
 FIG. 87. Bronchial tube, with 
 
RESPIRATION. 
 
 2O7 
 
 the large bronchi, the oesophagus, the heart in its pericardium, 
 and the great blood-vessels. The base of the lungs rests on 
 the dome-like diaphragm, which separates the chest from the 
 abdomen. This partly muscular and partly tendinous partition 
 is a most important 
 factor in breathing. 
 
 Each lung is 
 covered, except at 
 one point, with an 
 elastic serous mem- 
 brane in a double 
 layer, called the 
 pleura. One layer 
 closely envelops the 
 lung, at the apex of 
 which it is reflected 
 to the wall of the 
 chest cavity of its 
 own side, which it 
 lines. The two layers 
 thus form between 
 them a closed sac, a 
 serous cavity (see 
 Fig. 69, also note, 
 p. 176). 
 
 In health the two 
 pleural surfaces of the lungs are always in contact, and they 
 secrete just enough serous fluid to allow the surfaces to glide 
 smoothly upon each other. Inflammation of this membrane is 
 called pleurisy. In this disease the breathing becomes very 
 painful, as the secretion of glairy serum is suspended, and the 
 dry and inflamed surfaces rub harshly upon each other. 
 
 The root of the lung, as it is called, is formed by the bronchi, 
 two pulmonary arteries, and two pulmonary veins. The nerves 
 
 FIG. 88. The Lungs with the Trachea, Bronchi, and 
 Larger Bronchial Tubes exposed. (Posterior view.) 
 
 A, division of left bronchus to upper lobe ; B, left branch 
 of the pulmonary artery ; C, left bronchus ; D, left superior 
 pulmonary vein ; E, left inferior pulmonary vein ; F, left 
 auricle ; K, inferior vena cava ; L, division of right bronchus 
 to lower lobe; M, right inferior pulmonary vein ; N, right 
 superior pulmonary vein ; O, right branch of the pulmon- 
 ary artery ; P, division of right bronchus to upper lobe ; 
 R, left ventricle ; S, right ventricle. 
 
208 
 
 PRACTICAL PHYSIOLOGY. 
 
 and lymphatic vessels of the lung also enter at the root. If we 
 only remember that all the bronchial tubes, great and small, 
 are hollow, we may compare the whole system to a short bush or 
 tree growing upside down in the chest, of which the trachea is 
 the trunk, and the bronchial tubes the branches of various sizes. 
 
 207. Minute Structure of the Lungs. If one of the small- 
 est bronchial tubes be traced in its tree-like ramifications, it 
 will be found to end in an irregular funnel-shaped passage wider 
 than itself. Around this passage are grouped a number of 
 honeycomb-like sacs, the air cells 1 or alveoli of the lungs. 
 These communicate freely with the passage, and through it with 
 the bronchial branches, but have no other openings. The whole 
 
 FIG. 89. 
 A, diagrammatic representation of the ending of a bronchial tube in air sacs or alveoli; 
 
 B, termination of two bronchial tubes in enlargement beset with air sacs (Huxley); 
 
 C, diagrammatic view of an air sac. a lies within sac and points to epithelium 
 lining wall ; b, partition between two adjacent sacs, in which run capillaries ; 
 c, elastic connective tissue (Huxley). 
 
 arrangement of passages and air cells springing from the end 
 of a bronchial tube, is called an ultimate lobule. Now each 
 lobule is a very small miniature of a whole lung, for by the 
 grouping together of these lobules another set of larger lobules 
 is formed. 
 
 1 The word " cell " is not used in this connection in its technical signification of a 
 histological unit of the body (sec. 12), but merely in its primary sense of a small cavity. 
 
RESPIRATION. 
 
 209 
 
 In like manner countless numbers of these lobules, bound 
 together by connective tissue, are grouped after the same fashion 
 to form by their aggregation the lobes of the lung. The right 
 lung has three such lobes; and the left, two. Each lobule has a 
 
 Maximum inspiration 
 
 Complonental air 
 
 Ordinary inspiration 
 
 TIDAL AIR 
 
 Ordinary expiration 
 
 Supplemental air 
 Maximum expiration 
 
 Residual air 
 
 y Vital capacity 
 
 Capacity of equilibrium 
 
 FIG. 90. Diagram to illustrate the Amounts of Air contained by the Lungs in 
 Various Phases of Ordinary and of Forced Respiration. 
 
 branch of the pulmonary artery entering it, and a similar rootlet 
 of the pulmonary vein leaving it. It also receives lymphatic 
 vessels, and minute twigs of the pulmonary plexus of nerves. 
 
 The walls of the air cells are of extreme thinness, consisting 
 of delicate elastic and connective tissue, and lined inside by a 
 single layer of thin epithelial cells. In the connective tissue 
 run capillary vessels belonging to the pulmonary artery and veins. 
 Now these delicate vessels running in the connective tissue are 
 surrounded on all sides by air cells. It is evident, then, that the 
 blood flowing through these capillaries is separated from the 
 air within the cells only by the thin walls of the vessels, and 
 the delicate tissues of the air cells. 
 
2IO PRACTICAL PHYSIOLOGY. 
 
 This arrangement is perfectly adapted for an interchange 
 between the blood in the capillaries and the air in the air cells. 
 This will be more fully explained in sec. 214. 
 
 208. Capacity of the Lungs. In breathing we alternately take 
 into and expel from the lungs a certain quantity of air. With each 
 quiet inspiration about 30 cubic inches of air enter the lungs, and 30 
 cubic inches pass out with each expiration. The air thus passing into 
 and out of the lungs is called tidal air. After an ordinary inspira- 
 tion, the lungs contain about 230 cubic inches of air. By taking a 
 deep inspiration, about 100 cubic inches more can be taken in. This 
 extra amount is called complemental air. 
 
 After an ordinary expiration, about 200 cubic inches are left in 
 the lungs, but by forced expiration about one-half of this may be 
 driven out. This is known as supplemental air. The lungs can 
 never be entirely emptied of air, about 75 to 100 cubic inches always 
 remaining. This is known as the residual air. 
 
 The air that the lungs of an adult man are capable of containing 
 is thus composed : 
 
 Complemental air 100 cubic inches. 
 
 Tidal " 30 " 
 
 Supplemental " 100 " " 
 
 Residual " . 100 " " 
 
 Total capacity of lungs ...... 330 " " 
 
 If, then, a person proceeds, after taking the deepest possible 
 breath, to breath out as much as he can, he expels : 
 
 Complemental air 100 cubic inches. 
 
 Tidal " 30 " " 
 
 Supplemental " 100 " " 
 
 230 
 
 This total of 230 cubic inches forms what is called the vital 
 capacity of the chest (Fig. 90). 
 
RESPIRATION. 211 
 
 209. The Movements of Breathing. The act of breathing 
 consists of a series of rhythmical movements, succeeding one 
 another in regular order. In the first movement, inspiration, 
 the chest rises, and there is an inrush of fresh air ; this is at 
 once followed by expiration, the falling of the chest walls, and 
 the output of air. A pause now occurs, and the same breath- 
 ing movements are repeated. 
 
 The entrance and the exit of air into the respiratory passages 
 are accompanied with peculiar sounds which are readily heard 
 on placing the ear at the chest wall. These sounds are greatly 
 modified in various pulmonary diseases, and hence are of great 
 value to the physician in making a correct diagnosis. 
 
 In a healthy adult, the number of respirations should be from 
 1 6 to 18 per minute, but they vary with age, that of a newly 
 born child being 44 for the same time. Exercise increases the 
 number, while rest diminishes it. In standing, the rate is 
 more than when lying at rest. Mental emotion and excitement 
 quicken the rate. The number is smallest during sleep. Dis- 
 ease has a notable effect upon the frequency of respirations. 
 In diseases involving the lungs, bronchial tubes, and the pleura, 
 the rate may be alarmingly increased, and the pulse is quick- 
 ened in proportion. 
 
 210. The Mechanism of Breathing. The chest is a cham- 
 ber with bony walls, the ribs connecting in front with the 
 breastbone, and behind with the spine. The spaces between 
 the ribs are occupied by the intercostal muscles, while large 
 muscles clothe the entire chest. The diaphragm serves as a 
 movable floor to the chest, which is an air-tight chamber with 
 movable walls and floor. In this chamber are suspended the 
 lungs, the air cells of which communicate with the outside 
 through the bronchial passages, but have no connection with 
 the chest cavity. The thin space between the lungs and the 
 rib walls, called the pleural cavity, is in health a vacuum. 
 
212 
 
 PRACTICAL PHYSIOLOGY. 
 
 Now, when the diaphragm contracts, it descends and thus 
 increases the depth of the chest cavity. A quantity of air is 
 now drawn into the lungs and causes them to expand, thus 
 filling up the increased space. As soon as the diaphragm re- 
 laxes, returning to its arched position and 
 reducing the size of the chest cavity, the 
 air is driven from the lungs, which then 
 diminish in size. After a short pause, 
 the diaphragm again contracts, and the 
 same round of operation is constantly 
 repeated. 
 
 The walls of the chest being movable, 
 by the contractions of the intercostals 
 and other muscles, the ribs are raised 
 and the breastbone pushed forward. 
 The chest cavity is thus enlarged from 
 side to side and from behind forwards. 
 Thus, by the simultaneous descent of 
 the diaphragm and the elevation of the 
 ribs, the cavity of the chest is increased 
 
 in three directions, downwards, side- 
 FiG.9i.-DiagrammaticSec- ^ forwardg 
 
 tion of the Trunk. (Show- * ' 
 
 ing the expansion of the It is thus evident that inspiration is due 
 chest and the movement of to a series of muscular contractions. 
 
 the ribs by action of the ., , -u 
 
 lungs.) [The dotted lines As soon as the contractions cease, the 
 indicate the position dur- elastic lung tissue resumes its original 
 ing inspiration.] position, just as an extended rubber 
 
 band recovers itself. As a result, the original size of the chest 
 
 cavity is restored, and the inhaled air is driven from the lungs. 
 
 Expiration may then be regarded as the result of an elastic 
 
 recoil, arid not of active muscular contractions. 
 
 211. Varieties of Breathing. This is the mechanism of 
 quiet, normal respiration. When the respiration is difficult, 
 additional forces are brought into play. Thus when the wind- 
 
RESPIRATION. 2 I 3 
 
 pipe and bronchial tubes are obstructed, as in croup, asthma, 
 or consumption, many additional muscles are made use of to 
 help the lungs to expand. The position which asthmatics often 
 assume, with arms raised to grasp something for support, is 
 from the need of the sufferer to get a fixed point from which 
 the muscles of the arm and chest may act forcibly in raising 
 the ribs, and thus securing more comfortable breathing. 
 
 The visible movements of breathing vary according to cir- 
 cumstances. In infants the action of the diaphragm is marked, 
 and the movements of the abdomen are especially obvious. 
 This is called abdominal breathing. In women the action of 
 the ribs as they rise and fall, is emphasized more than in men, 
 and this we call costal breathing. In young persons and in 
 men, the respiration not usually being impeded by tight cloth- 
 ing, the breathing is normal, being deep and abdominal. 
 
 Disease has a marked effect upon the mode of breathing. 
 Thus, when children suffer from some serious chest disease, 
 the increased movements of the abdominal walls seem distress- 
 ing. So in fracture of the ribs, the surgeon envelops the 
 overlying part of the chest with long strips of firm adhesive 
 plaster to restrain the motions of chest respiration, that they 
 may not disturb the jagged ends of the broken bones. Again, 
 in painful diseases of the abdomen, the sufferer instinctively 
 suspends the abdominal action and relies upon the chest 
 breathing. These deviations from the natural movements of 
 respiration are useful to the physician in ascertaining the seat 
 of disease. 
 
 212. The Nervous Control of Respiration. It is a matter 
 of common experience that one's breath may be held for a 
 short time, but the need of fresh air speedily gets the mastery, 
 and a long, deep breath is drawn. Hence the efforts of crim- 
 inals to commit suicide by persistent restraint of their breath- 
 ing, are always a failure. At the very worst, unconsciousness 
 ensues, and then respiration is automatically resumed. Thus 
 
214 PRACTICAL PHYSIOLOGY. 
 
 a wise Providence defeats the purpose of crime. The move- 
 ments of breathing go on without our attention. In sleep the 
 regularity of respiration is even greater than when awake. 
 There is a particular part of the nervous system that presides 
 over the breathing function. It is situated in that part of the 
 brain called the medulla oblongata, and is fancifully called the 
 "vital knot" (sec. 270). It is injury to this respiratory center 
 which proves fatal in cases of broken neck. 
 
 From this nerve center there is sent out to the nerves that 
 supply the diaphragm and other muscles of breathing, a force 
 which stimulates them to regular contraction. This breathing 
 center is affected by the condition of the blood. It is stimu- 
 lated by an excess of carbon dioxid in the blood, and is quieted 
 by the presence of oxygen. 
 
 Experiment 108. To locate the lungs. Mark out the boundaries of the 
 lungs by " sounding " them ; that is, by percussion, as it is called. This 
 means to put the forefinger of the left hand across the chest or back, 
 and to give it a quick, sharp rap with two or three fingers. Note where 
 it sounds hollow, resonant. This experiment can be done by the student 
 with only imperfect success, until practice brings some skill. 
 
 Experiment 109. Borrow a stethoscope, and listen to the respiration 
 over the chest on the right side. This is known as auscultation. Note the 
 difference of the sounds in inspiration and in expiration. Do not confuse 
 the heart sounds with those of respiration. The respiratory murmurs may be 
 heard fairly well by applying the ear flat to the chest, with only one garment 
 interposed. 
 
 Experiment no. Get a sheep's lungs, with the windpipe attached. 
 Ask for the heart and lungs all in one mass. Take pains to examine the 
 specimen first, and accept only a good one. Parts are apt to be hastily 
 snipped or mangled. Examine the windpipe. Note the horseshoe-shaped 
 rings of cartilage in front, which serve to keep it open. 
 
 Experiment in. Examine one bronchus, carefully dissecting away the 
 lung tissue with curved scissors. Follow along until small branches of the 
 bronchial tubes are reached. Take time for the dissection, and save the 
 specimen in dilute alcohol. Put pieces of the lung tissue in a basin of 
 water, and note that they float. 
 
RESPIRATION. 2 I 5 
 
 The labored breathing of suffocation and of lung diseases is 
 due to the excessive stimulation of this center, caused by the 
 excess of carbon dioxid in the blood. Various mental influ- 
 ences from the brain itself, as the emotions of alarm or joy or 
 distress, modify the action of the respiratory center. 
 
 Again, nerves of sensation on the surface of the body convey 
 influences to this nerve center and lead to its stimulation, re- 
 sulting in a vigorous breathing movement. Thus a dash of 
 cold water on the face or neck of a fainting person instantly 
 produces a deep, long-drawn breath. Certain drugs, as opium, 
 act to reduce the activity of this nerve center. Hence, in 
 opium poisoning, special attention should be paid to keeping 
 up the respiration. The condition of the lungs themselves is 
 made known to the breathing center, by messages sent along 
 the branches of the great pneumogastric nerve (page 276), 
 leading from the lungs to the medulla oblongata. 
 
 213. Effects of Respiration upon the Blood. The blood 
 contains three gases, partly dissolved in it and partly in chem- 
 ical union with certain of its constituents. These are oxygen, 
 carbon dioxid, and nitrogen. The latter need not be taken 
 into account. The oxygen is the nourishing material which 
 the tissues require to carry on their work. The carbon dioxid 
 is a waste substance which the tissues produce by their activity, 
 and which the blood carries away from them. 
 
 As before shown, the blood as it flows through the tissues 
 loses most of its oxygen, and carbon dioxid takes its place. 
 Now if the blood is to maintain its efficiency in this respect, it 
 must always be receiving new supplies of oxygen, and also have 
 some mode of throwing off its excess of carbon dioxid. This, 
 then, is the double function of the process of respiration. 
 Again, the blood sent out from the left side of the heart is of 
 a bright scarlet color. After its work is done, and the blood 
 returns to the right side of the heart, it is of a dark purple 
 
2l6 PRACTICAL PHYSIOLOGY. 
 
 color. This change in color takes place in the capillaries, and 
 is due to the fact that there the blood gives up most of its 
 oxygen to the tissues and receives from them a great deal of 
 carbon dioxid. 
 
 In brief, while passing through the capillaries of the lungs the 
 blood has been changed from the venous to the arterial blood. 
 That is to say, the blood in its progress through the lungs has 
 rid itself of its excess of carbon dioxid and obtained a fresh 
 supply of oxygen. 1 
 
 214. Effects of Respiration upon the Air in the Lungs. 
 It is well known that if two different liquids be placed in a 
 vessel in contact with each other and left undisturbed, they 
 do not remain separate, but gradually mix, and in time will be 
 perfectly combined. This is called diffusion of liquids. The 
 same thing occurs with gases, though the process is not visible. 
 This is known as the diffusion of gases. It is also true that 
 two liquids will mingle when separated from each other by a 
 membrane (sec. 129). In a similar manner two gases, espe- 
 cially if of different densities, may mingle even when separated 
 from each other by a membrane. 
 
 In a general way this explains the respiratory changes 
 that occur in the blood in the lungs. Blood containing oxygen 
 and carbon dioxid is flowing in countless tiny streams through 
 the walls of the air cells of the lungs. The air cells themselves 
 contain a mixture of the same two gases. A thin, moist 
 membrane, well adapted to allow gaseous diffusion, separates 
 the blood from the air. This membrane is the delicate wall 
 of the capillaries and the epithelium of the air cells. By 
 
 1 " The student must guard himself against the idea that arterial blood contains 
 no carbonic acid, and venous blood no oxygen. In passing through the lungs 
 venous blood loses only a part of its carbonic acid ; and arterial blood, in passing 
 through the tissues, loses only a part of its oxygen. In blood, however venous, there 
 is in health always some oxygen ; and in even the brightest arterial blood there is 
 actually more carbonic acid than oxygen." T. H. HUXLEY. 
 
RESPIRATION. 
 
 217 
 
 experiment it has been found that the pressure of oxygen in 
 the blood is less than that in the air cells, and that the pressure 
 of carbon dioxid gas in the blood is greater than that in the 
 air cells. As a result, a diffusion of gases ensues. The blood 
 gains oxygen and loses 
 carbon dioxid, while the 
 air cells lose oxygen and 
 gain the latter gas. 
 
 The blood thus be- 
 comes purified and re- 
 invigorated, and at the 
 same time is changed in 
 color from purple to 
 scarlet, from venous to 
 arterial. It is now evident 
 that if this interchange 
 
 is tO Continue, the air in A, small branch of pulmonary artery ; B, twigs of 
 
 pulmonary artery anastomosing to form peripheral 
 network of the primitive air cells ; C, capillary net- 
 work around the walls of the air sacs ; D, branches 
 of network converging to form the veinlets of the 
 pulmonary veins. 
 
 FIG. 92. Capillary Network of the Air Cells 
 and Origin of the Pulmonary Veins. 
 
 the cells must be con- 
 stantly renewed, its oxy- 
 gen restored, and its 
 excess of carbon dioxid 
 removed. Otherwise the process just described would be 
 reversed, making the blood still more unfit to nourish the 
 tissues, and more poisonous to them than before. 
 
 215. Change in the Air in Breathing. The air which we exhale 
 during respiration differs in several important particulars from the 
 air we inhale. Both contain chiefly the three gases, though in differ- 
 ent quantities, as the following table shows. 
 
 Inspired air contains 
 Expired air contains 
 
 Oxygen. 
 20.81 
 16.03 
 
 Nitrogen. 
 
 79-15 
 
 79-58 
 
 Carbon dioxid. 
 
 .04 - 
 4-38 
 
 That is, expired air contains about five per cent less oxygen and 
 five per cent more carbon dioxid than inspired air. 
 
2l8 PRACTICAL PHYSIOLOGY. 
 
 The temperature of expired air is variable, but generally is higher 
 than that of inspired air, it having been in contact with the warm air 
 passages. It is also loaded with aqueous vapor, imparted to it like 
 the heat, not in the depth of the lungs, but in the upper air 
 passages. 
 
 Expired air contains, besides carbon dioxid, various impurities, 
 many of an unknown nature, and all in small amounts. When the 
 expired air is condensed in a cold receiver, the aqueous product is 
 found to contain organic matter, which, from the presence of micro- 
 orgaAisms, introduced in the inspired air, is apt to putrefy rapidly. 
 Some of these organic substances are probably poisonous, either so 
 in themselves, as produced in some manner in the breathing appara- 
 tus, or poisonous as being the products of decomposition. For it is 
 known that various animal substances give rise, by decomposition, to 
 distinct poisonous products known as ptomaines. It is possible 
 that some of the constituents of the expired air are of an allied 
 nature. See under Bacteria " (Chapter XIV). 
 
 At all events, these substances have an injurious action, for an 
 atmosphere containing simply one per cent of pure carbon dioxid has 
 very little hurtful effect on the animal economy, but an atmosphere in 
 which the carbon dioxid has been raised one per cent by breathing is 
 highly injurious. 
 
 The quantity of oxygen removed from the air by the breathing of 
 an adult person at rest amounts daily to about 1 8 cubic feet. About 
 the same amount of carbon dioxid is expelled, and this could be repre- 
 sented by a piece of pure charcoal weighing 9 ounces. The quantity 
 of carbon dioxid, however, varies with the age, and is increased also 
 by external cold and by exercise, and is affected by the kind of food. 
 The amount of water, exhaled as vapor, varies from 6 to 20 ounces 
 daily. The average daily quantity is about one-half a pint. 
 
 216. Modified Respiratory Movements. The respiratory 
 column of air is often used in a mechanical way to expel bodies 
 from the upper air passages. There are also, in order to 
 secure special ends, a number of modified movements not dis- 
 tinctly respiratory. The following peculiar respiratory acts call 
 for a few words of explanation. 
 
RESPIRATION. 
 
 2I 9 
 
 A sigh is a rapid and generally audible expiration, due to 
 the elastic recoil of the lungs and chest walls. It is often 
 caused by depressing emotions. Yawning is a deep inspira- 
 tion with a stretching of the muscles of the face and mouth, 
 and is usually excited by fatigue or drowsiness, but often occurs 
 from a sort of contagion. 
 
 Hiccough is a sudden jerking inspiration due to the spas- 
 modic contraction of the diaphragm and of the glottis, caus- 
 ing the air to rush suddenly through the larynx, and produce 
 this peculiar sound. Snoring is caused by vibration of the soft 
 palate during sleep, and is habitual with some, although it occurs 
 with many when the system is unusually exhausted and relaxed. 
 
 Laughing consists of a series of short, rapid, spasmodic 
 expirations which cause the peculiar sounds, with characteristic 
 movements of the facial muscles. Crying, caused by emotional 
 states, consists of sudden jerky expirations with long inspira- 
 tions, with facial movements indicative of distress. In sobbing, 
 which often follows long-continued crying, there is a rapid 
 series of convulsive inspirations, with sudden involuntary con- 
 tractions of the diaphragm. Laughter, and sometimes sobbing, 
 like yawning, may be the result of involuntary imitation. 
 
 Experiment 112. Simple Apparatus to Illustrate the Movements of the 
 Lungs in the Chest. T is a bottle from 
 which the bottom has been removed ; D, a 
 flexible and elastic membrane tied on the 
 bottle, and capable of being pulled out by 
 the string S, so as to increase the capacity 
 of the bottle. L is a thin elastic bag repre- 
 senting the lungs. It communicates with 
 the external air by a glass tube fitted air- 
 tight through a cork in the neck of the 
 bottle. \Vhen D is drawn down, the pres- 
 sure of the external air causes L to expand. 
 When the string is let go, L contracts 
 again, by virtue of its elasticity. FIG. 93. 
 
22O PRACTICAL PHYSIOLOGY. 
 
 Coughing is produced by irritation in the upper part of the 
 windpipe and larynx. A deep breath is drawn, the opening 
 of the windpipe is closed, and immediately is burst open with 
 a violent effort which sends a blast of air through the upper 
 air passages. The object is to dislodge and expel any mucus 
 or foreign matter that is irritating the air passages. 
 
 Sneezing is like coughing ; the tongue is raised against the 
 soft palate, so the air is forced through the nasal passages. It 
 is caused by an irritation of the nostrils or eyes. In the begin- 
 ning of a cold in the head, for instance, the cold air irritates 
 the inflamed mucous membrane of the nose, and causes 
 repeated attacks of sneezing. 
 
 217. How the Atmosphere is Made Impure. The air 
 
 around us is constantly being made impure in a great variety 
 of ways. The combustion of fuel, the respiration of men and 
 animals, the exhalations from their bodies, the noxious gases 
 and effluvia of the various industries, together with the changes 
 of fermentation and decomposition to which all organized 
 matter is liable, all tend to pollute the atmosphere. 
 
 The necessity of external ventilation has been foreseen for 
 us. The forces of nature, the winds, sunlight, rain, and 
 growing vegetation, all of great power and universal distri- 
 bution and application, restore the balance, and purify the air. 
 As to the principal gases, the air of the city does not differ 
 materially from that of rural sections. There is, however, a 
 vastly greater quantity of dust and smoke in the air of towns. 
 The breathing of this dust, to a greater or less extent laden 
 with bacteria, fungi, and the germs of disease, is an ever-present 
 and most potent menace to public and personal health. It is 
 one of the main causes of the excess of mortality in towns and 
 cities over that of country districts. 
 
 This is best shown in the overcrowded streets and houses of 
 great cities, which are deprived of the purifying influence of 
 
RESPIRATION. 221 
 
 sun and air. The fatal effect of living in vitiated air is espe- 
 cially marked in the mortality among infants and children 
 living in the squalid and overcrowded sections of our great 
 cities. The salutary effect of sunshine is shown by the fact 
 that mortality is usually greater on the shady side of the street. 
 
 218. How the Air is Made Impure by Breathing. It is 
 
 not the carbon dioxid alone that causes injurious results to 
 health, it is more especially the organic matter thrown off 
 in the expired air. The carbon dioxid which accompanies the 
 organic matter is only the index. In testing the purity of air 
 it is not difficult to ascertain the amount of carbon dioxid 
 present, but it is no easy problem to measure the amount of 
 organic matter. Hence it is the former that is looked for in 
 factories, churches, schoolrooms, and when it is found to exceed 
 .07 per cent it is known that there is a hurtful amount of organic 
 matter present. 
 
 The air as expelled from the lungs contains, not only a cer- 
 tain amount of organic matter in the form of vapor, but minute 
 solid particles of debris and bacterial micro-organisms (Chap. 
 XIV). The air thus already vitiated, after it leaves the mouth, 
 putrefies very rapidly. It is at once absorbed by clothing, 
 curtains, carpets, porous walls, and by many other objects. It 
 is difficult to dislodge these enemies of health even by free 
 ventilation. The close and disagreeable odor of a filthy or 
 overcrowded room is due to these organic exhalations from 
 the lungs, the skin, and the unclean clothing of the occupants. 
 
 The necessity of having a proper supply of fresh air in en- 
 closed places, and the need of removal of impure air are thus 
 evident. If a man were shut up in a tightly sealed room con- 
 taining 425 cubic feet of air, he would be found dead or nearly 
 so at the end of twenty-four hours. Long before this time he 
 would have suffered from nausea, headache, dizziness, and 
 other proofs of blood-poisoning. These symptoms are often felt 
 
222 PRACTICAL PHYSIOLOGY. 
 
 by those who are confined for an hour or more in a room where 
 the atmosphere has been polluted by a crowd of people. The 
 unpleasant effects rapidly disappear on breathing fresh air. 
 
 219. The Effect on the Health of Breathing Foul Air. 
 People are often compelled to remain indoors for many hours, 
 day after day, in shops, factories, or offices, breathing air 
 perhaps only slightly vitiated, but still recognized as " stuffy." 
 Such persons often suffer from ill health. The exact form 
 of the disturbance of health depends much upon the heredi- 
 tary proclivity and physical make-up of the individual. Loss 
 of appetite, dull headache, fretfulness, persistent weariness, 
 despondency, followed by a general weakness and an impover- 
 ished state of blood, often result. 
 
 Persons in this lowered state of health are much more prone 
 to suffer from colds, catarrhs, bronchitis, and pneumonia than 
 if they were living in the open air, or breathing only pure air. 
 Thus, in the Crimean War, the soldiers who lived in tents in 
 the coldest weather were far more free from colds and lung 
 troubles than those who lived in tight and ill-ventilated huts. 
 In the early fall when typhoid fever is prevalent, the grounds 
 of large hospitals are dotted with canvas tents, in which patients 
 suffering from this fever do much better* than in the wards. 
 
 This tendency to inflammatory diseases of the air passages 
 is aggravated by the overheated and overdried condition of 
 the air in the room occupied. This may result from burning 
 gas, from overheated furnaces and stoves, hot-water pipes, and 
 other causes. Serious lung diseases, such as consumption, are 
 more common among those who live in damp, overcrowded, or 
 poorly ventilated homes. 
 
 220. The Danger from Pulmonary Infection. The germ 
 of pulmonary consumption, known as the bacillus tuberculosis, 
 is contained in the breath and the sputa from the lungs of its 
 victims. It is not difficult to understand how these bacilli may 
 
RESPIRATION. 223 
 
 be conveyed through the air from the lungs of the sick to those 
 of apparently healthy people. Such persons may, however, be 
 predisposed, either constitutionally or by defective hygienic 
 surroundings, to fall victims to this dreaded disease. Over- 
 crowding, poor ventilation, and dampness all 
 tend to increase the risk of pulmonary in- 
 fection. 
 
 It must not be supposed that the tubercle 
 bacillus is necessarily transmitted directly FIG. 94. 
 
 through the air from the lungs of the sick to Example of a Micro- 
 
 i IT r ,i_ i 1.1 Organism Bacillus 
 
 be implanted in the lungs of the healthy. Tubercuk)sis in Spu - 
 The germs may remain for a time in the dust tum. (Magnified 
 
 _, , , , , about 500 diameters.) 
 
 and debris of damp, filthy, and overcrowded 
 houses. In this congenial soil they retain their vitality for a long 
 time, and possibly may take on more virulent infective properties 
 than they possessed when expelled from the diseased lungs. 1 
 
 221. Ventilation. The question of a practicable and eco- 
 nomical system of ventilation for our homes, schoolrooms, 
 workshops, and public places presents many difficult and per- 
 plexing problems. It is perhaps due to the complex nature of 
 the subject, that ventilation, as an ordinary condition of daily 
 health, has been so much neglected. The matter is practically 
 ignored in building ordinary houses. The continuous renewal 
 of air receives little if any consideration, compared with the 
 provision made to furnish our homes with heat, light, and 
 
 1 " Consumption is a disease which can be taken from others, and is not simply 
 caused by colds. A cold may make it easier to take the disease. It is usually caused 
 by germs which enter the body with the air breathed. The matter which consump- 
 tives cough or spit up contains these germs in great numbers frequently millions 
 are discharged in a single day. This matter spit upon the floor, wall, or elsewhere 
 is apt to dry, become pulverized, and float in the air as dust. The dust contains the 
 germs, and thus they enter the body with the air breathed. The breath of a consump- 
 tive does not contain the germs and will not produce the disease. A well person 
 catches the disease from a consumptive only by in some way taking in the matter 
 coughed up by the consumptive." Extract from a circular issued by the Board of 
 Health of New York City. 
 
224 PRACTICAL PHYSIOLOGY. 
 
 water. When the windows are closed we usually depend for 
 ventilation upon mere chance, on the chimney, the fireplace, 
 and the crevices of doors and windows. The proper ventilation 
 of a house and its surroundings should form as prominent a con- 
 sideration in the plans of builders and architects as do the grading 
 of the land, the size of the rooms, and the cost of heating. 
 
 The object of ventilation is twofold : First, to provide for 
 the removal of the impure air ; second, for a supply of pure 
 air. This must include a plan to provide fresh air in such a 
 manner that there shall be no draughts or exposure of the 
 occupants of the rooms to undue temperature. Hence, what 
 at first might seem an easy thing to do, is, in fact, one of the 
 most difficult of sanitary problems. 
 
 222. Conditions of Efficient Ventilation. To secure proper 
 ventilation certain conditions must be observed. The pure air 
 introduced should not be far below the temperature of the 
 room, or if so, the entering current should be introduced 
 towards the ceiling, that it may mix with the warm air. 
 
 Draughts must be avoided. If the circuit from entrance to 
 exit is short, draughts are likely to be produced, and impure 
 air has less chance of mixing by diffusion with the pure air. 
 The current of air introduced should be constant, otherwise 
 the balance may occasionally be in favor of vitiated air. If a 
 mode of ventilation prove successful, it should not be interfered 
 with by other means of entrance. Thus, an open door may 
 prevent the incoming air from passing through its proper chan- 
 nels. It is desirable that the inlet be so arranged that it can be 
 diminished in size or closed altogether. For instance, when 
 the outer air is very cold, or the wind blows directly into the 
 inlet, the amount of cold air entering it may lower the tempera- 
 ture of the room to an undesirable degree. 
 
 In brief, it is necessary to have a thorough mixing of pure 
 and impure air, so that the combination at different parts of 
 
RESPIRATION. 225 
 
 the room may be fairly uniform. To secure these results, 
 the inlets and outlets should be arranged upon principles of 
 ventilation generally accepted by authorities on public health. 
 It seems hardly necessary to say that due attention must be 
 paid to the source from which the introduced air is drawn. If 
 it be taken from foul cellars, or from dirty streets, it may be as 
 impure as that which it is designed to replace. 
 
 ANIMAL HEAT. 
 
 223. Animal or Vital Heat. If a thermometer, made for 
 the purpose, be placed for five minutes in the armpit, or under 
 the tongue, it will indicate a temperature of about 98 1 F., 
 whether the surrounding atmosphere be warm or cold. This 
 is the natural heat of a healthy person, and in health it rarely 
 varies more than a degree or two. But as the body is con- 
 stantly losing heat by radiation and conduction, it is evident 
 that if the standard temperature be maintained, a certain 
 amount of heat must be generated within the body to make 
 up for the loss externally. The heat thus produced is known 
 as animal or vital heat. 
 
 This generation of heat is common to all living organisms. 
 When the mass of the body is large, its heat is readily percep- 
 tible to the touch and by its effect upon the thermometer. In 
 mammals and birds the heat-production is more active than in 
 fishes and reptiles, and their temperatures differ in degree even 
 in different species of the same class, according to the special 
 organization of the animal and the general activity of its func- 
 tions. The temperature of the frog may be 85 F. in June and 
 41 F. in January. The structure of its tissues is unaltered 
 and their vitality unimpaired by such violent fluctuations. But 
 in man it is necessary not only for health, but even for life, that 
 the temperature should vary only within narrow limits around 
 the mean of 981 F. 
 
226 PRACTICAL PHYSIOLOGY. 
 
 We are ignorant of the precise significance of this constancy 
 of temperature in warm-blooded animals, which is as important 
 and peculiar as their average height. Man, undoubtedly, must 
 possess a superior delicacy of organization, hardly revealed by 
 structure, which makes it necessary that he should be shielded 
 from the shocks and jars of varying temperature, that less highly 
 endowed organisms endure with impunity. 
 
 224. Sources of Bodily Heat. The heat of the body is 
 generated by the chemical changes, generally spoken of as 
 those of oxidation, which are constantly going on in the tissues. 
 Indeed, whenever protoplasmic materials are being oxidized 
 (the process referred to in sec. 15 as katabolism) heat is being 
 set free. These chemical changes are of various kinds, but 
 the great source of heat is the katabolic process, known as 
 oxidation. 
 
 The vital part of the tissues, built up from the complex 
 classes of food, is oxidized by means of the oxygen carried by 
 the arterial blood, and broken down into simpler bodies which 
 at last result in urea, carbon dioxid, and water. Wherever 
 there is life, this process of oxidation is going on, but more 
 energetically in some tissues and organs than in others. In 
 other words, the minutest tissue in the body is a source of 
 heat in proportion to the activity of its chemical changes. 
 The more active the changes, the greater is the heat produced, 
 and the greater the amount of urea, carbon dioxid, and water 
 eliminated. The waste caused by this oxidation must be 
 made good by a due supply of food to be built up into 
 protoplasmic material. For the production of heat, therefore, 
 food is necessary. But the oxidation process is not as simple 
 and direct as the statement of it might seem to indicate. 
 Though complicated in its various stages, the ultimate result is 
 as simple as in ordinary combustion outside of the body, and 
 the products are the same. 
 
RESPIRATION. 22? 
 
 The continual chemical changes, then, chiefly by oxidation 
 of combustible materials in the tissues, produce an amount of 
 heat which is efficient to maintain the temperature of the living 
 body at about 98^ F. This process of oxidation provides not 
 only for the heat of the body, but also for the energy required 
 to carry on the muscular work of the animal organism. 
 
 225. Regulation of the Bodily Temperature. While bodily 
 heat is being continually produced, it is also as continually being 
 lost by the lungs, by the skin, and to some extent, by certain 
 excretions. The blood, in its swiftly flowing current, carries 
 warmth from the tissues where heat is being rapidly generated, 
 to the tissues or organs in which it is being lost by radiation, 
 conduction, or evaporation. Were there no arrangement by 
 which heat could be distributed and regulated, the temperature 
 of the body would be very unequal in different parts, and 
 would vary at different times. 
 
 The normal temperature is maintained with slight variations 
 throughout life. Indeed a change of more than a degree above 
 or below the average, indicates some failure in the organism, or 
 some unusual influence. It is evident, then, that the mechan- 
 isms which regulate the temperature of the body must be 
 exceedingly sensitive. 
 
 The two chief means of regulating the temperature of the 
 body are the lungs and the skin. As a means of lowering 
 the temperature, the lungs and air passages are very inferior to 
 the skin ; although, by giving heat to the air we breathe, they 
 stand next to the skin in importance. As a regulating power 
 they are altogether subordinate to the skin. 
 
 Experiment 113. To show the natural temperature of the body. Bor- 
 row a physician's clinical thermometer, and take your own temperature, 
 and that of several friends, by placing the instrument under the tongue, 
 closing the mouth, and holding it there for five minutes. It should be 
 thoroughly cleansed after each use. 
 
228 PRACTICAL PHYSIOLOGY. 
 
 226. The Skin as a Heat-regulator. The great 'regulator 
 of the bodily temperature is, undoubtedly, the skin, which per- 
 forms this function by means of a self-regulating apparatus with 
 a more or less double action. First, the skin regulates the loss 
 of heat by means of the vaso-motor mechanism. The more 
 blood passes through the skin, the greater will be the loss of 
 heat by conduction, radiation, and evaporation. Hence, any 
 action of the vaso-motor mechanism which causes dilatation 
 of the cutaneous capillaries, leads to a larger flow of blood 
 through the skin, and will tend to cool the body. On the 
 other hand, when by the same mechanism the cutaneous 
 vessels are constricted, there will be a smaller flow of blood 
 through the skin, which will serve to check the loss of heat 
 from the body (sees. 195 and 270). 
 
 Again, the special nerves of perspiration act directly as 
 regulators of temperature. They increase the loss of heat 
 when they promote the secretion of the skin, and diminish the 
 loss when they cease to promote it. 
 
 The practical working of this heat-regulating mechanism is 
 well shown by exercise. The bodily temperature rarely rises 
 so much as a degree during vigorous exercise. The respiration 
 is increased, the cutaneous capillaries become dilated from the 
 quickened circulation, and a larger amount of blood is circulat- 
 ing through the skin. Besides this, the skin perspires freely. 
 A large amount of heat is thus lost to the body, sufficient to 
 offset the addition caused by the muscular contractions. 
 
 It is owing to the wonderful elasticity of the sweat-secreting 
 mechanism, and to the increase in respiratory activity, and the 
 consequent increase in the amount of watery vapor given off 
 by the lungs, that men are able to endure for days an atmo- 
 sphere warmer than the blood, and even for a short time at a 
 temperature above that of boiling water. The temperature of 
 a Turkish bath may be as high as 150 to 175 F. But an atmo- 
 spheric temperature may be considerably below this, and yet 
 
RESPIRATION. 32Q 
 
 if long continued becomes dangerous to life. In August, 1896, 
 for instance, hundreds of persons died in this country, within 
 a few days, from the effects of the excessive heat. 
 
 A much higher temperature may be borne in dry air than in 
 humid air, or that which is saturated with watery vapor. Thus, 
 a shade temperature of 100 F. in the dry air of a high plain 
 may be quite tolerable, while a temperature of 80 F. in the 
 moisture-laden atmosphere of less elevated regions, is oppres- 
 sive. The reason is that in dry air the sweat evaporates freely, 
 and cools the skin. In saturated air at the bodily temperature 
 there is little loss of heat by perspiration, or by evaporation 
 from the bodily surface. 
 
 This topic is again discussed in the description of the skin 
 as a regulator of the bodily temperature (sec. 241). 
 
 227. Voluntary Means of Regulating the Temperature. 
 
 The voluntary factor, as a means of regulating the heat loss 
 in man, is one of great importance. Clothing retards the loss 
 of heat by keeping in contact with it a layer of still air, which 
 is an exceedingly bad conductor. When a man feels too warm 
 and throws off his coat, he removes one of the badly conduct- 
 ing layers of air, and increases the heat loss by radiation and 
 conduction. The vapor next the skin is thus allowed a freer 
 access to the surface, and the loss of heat by evaporation of 
 the sweat becomes greater. This voluntary factor by which 
 the equilibrium is maintained must be regarded as of great 
 importance. This power also exists in the lower animals, but 
 to a much smaller extent. Thus a dog, on a hot day, runs out 
 his tongue and stretches his limbs so as to increase the sur- 
 face from which heat is radiated and conducted. 
 
 The production, like the loss, of heat is to a certain extent 
 under the control of the will. Work increases the production 
 of heat, and rest, especially sleep, less.ens it. Thus the inhab- 
 itants of very hot countries seek relief during the hottest part 
 
23O PRACTICAL PHYSIOLOGY. 
 
 of the day by a siesta. The quantity and quality of food also 
 influence the production of heat. A larger quantity of food is 
 taken in winter than in summer. Among the inhabitants of 
 the northern and Arctic regions, the daily consumption of food 
 is far greater than in temperate and tropical climates. 
 
 228. Effect of Alcohol upon the Lungs. It is a well recog- 
 nized fact that alcohol when taken into the stomach is carried 
 from that organ to the liver, where, by the baneful directness 
 of its presence, it produces a speedy and often disastrous effect. 
 But the trail of its malign power does not disappear there. 
 From the liver it passes to the right side of the heart, and 
 thence to the lungs, where its influence is still for harm. 
 
 In the lungs, alcohol tends to check and diminish the breath- 
 ing capacity of these organs. This effect follows from the 
 partial paralyzing influence of the stupefying agent upon the 
 sympathetic nervous system, diminishing its sensibility to the 
 impulse of healthful respiration. This diminished capacity 
 for respiration is clearly shown by the use of the spirometer, a 
 simple instrument which accurately records the cubic measure 
 of the lungs, and proves beyond denial the decrease of the 
 lung space. 
 
 " Most familiar and most dangerous is the drinking man's inability to resist lung 
 diseases." DR. ADOLPH FRICK, the eminent German physiologist of Zurich. 
 
 " Alcohol, instead of preventing consumption, as was once believed, reduces the 
 vitality so much as to render the system unusually susceptible to that fatal disease." 
 R. S. TRACY, M.D., Sanitary Inspector of the N. Y. City Health Dept. 
 
 " In thirty cases in which alcoholic phthisis was present a dense, fibroid, pigmented 
 change was almost invariably present in some portion of the lung far more frequently 
 than in other cases of phthisis." Annual of Medical Sciences. 
 
 " There is no form of consumption so fatal as that from alcohol. Medicines affect 
 the disease but little, the most judicious diet fails, and change of air accomplishes 
 but slight real good. ... In plain terms, there is no remedy whatever for alcoholic 
 phthisis. It may be delayed in its course, but it is never stopped ; and not infre- 
 quently, instead of being delayed, it runs on to a fatal termination more rapidly than 
 is common in any other type of the disorder." DR. B. W. RICHARDSON in Diseases 
 of Modern Life. 
 
RESPIRATION. 231 
 
 229. Other Results of Intoxicants upon the Lungs. But 
 a more potent injury to the lungs comes from another cause. 
 The lungs are the arena where is carried on the ceaseless inter- 
 change of elements that is necessary to the processes of life. 
 Here the dark venous blood, loaded with effete material, lays 
 down its carbon burden and, with the brightening company of 
 oxygen, begins again its circuit. But the enemy intrudes, and 
 the use of alcohol tends to prevent this benign interchange. 
 
 The continued congestion of the lung tissue results in its be- 
 coming thickened and hardened, thus obstructing the absorption 
 of oxygen, and the escape of carbon dioxid. Besides this, alcohol 
 destroys the integrity of the red globules, causing them to 
 shrink and harden, and impairing their power to receive oxygen. 
 Thus the blood that leaves the lungs conveys an excess of the 
 poisonous carbon dioxid, and a deficiency of the needful oxy- 
 gen. This is plainly shown in the purplish countenance of the 
 inebriate, crowded with enlarged veins. This discoloration of 
 the face is in a measure reproduced upon the congested mu- 
 cous membrane of the lungs. It is also proved beyond ques- 
 tion by the decreased amount of carbon dioxid thrown off in 
 the expired breath of any person who has used alcoholics. 
 
 The enfeebled respiration explains (though it is only one of 
 the reasons) why inebriates cannot endure vigorous and pro- 
 longed exertion as can a healthy person. The hurried circu- 
 lation produced by intoxicants involves in turn quickened 
 respiration, which means more rapid exhaustion of the life 
 forces. The use of intoxicants involves a repeated dilatation 
 of the capillaries, which steadily diminishes their defensive 
 power, rendering the person more liable to yield to the in- 
 vasion of pulmonary diseases. 1 
 
 1 " The lungs from the congested state of their vessels produced by alcohol are more 
 subject to the influence of cold, the result being frequent attacks of bronchitis. It has 
 been recognized of late years that there is a peculiar form of consumption of the 
 lungs which is very rapidly fatal and found only in alcohol drinkers." PROFESSOR 
 H. NEWELL MARTIN. 
 
232 PRACTICAL PHYSIOLOGY. 
 
 230. Effect of Alcoholics upon Disease. A theory has pre- 
 vailed, to a limited extent, that the use of intoxicants may act 
 as a preventive of consumption. The records of medical 
 science fail to show any proof whatever to support this impres- 
 sion. No error could be more serious or more misleading, 
 for the truth is in precisely the opposite direction. Instead 
 of preventing, alcohol tends to develop consumption. Many 
 physicians of large experience record the existence of a dis- 
 tinctly recognized alcoholic consumption, attacking those 
 constitutions broken down by dissipation. This form of 
 consumption is steadily progressive, and always fatal. 
 
 The constitutional debility produced by the habit of using 
 alcoholic beverages tends to render one a prompt victim to the 
 more severe diseases, as pneumonia, and especially epidemical 
 diseases, which sweep away vast numbers of victims every year. 
 
 231. Effect of Tobacco upon the Respiratory Passages. 
 The effects of tobacco upon the throat and lungs are fre- 
 quently very marked and persistent. The hot smoke must 
 very naturally be an irritant, as the mouth and nostrils were 
 not made as a chimney for heated and narcotic vapors. The 
 smoke is an irritant, both by its temperature and from its de- 
 structive ingredients, the carbon soot and the ammonia which 
 it conveys. It irritates and dries the mucous membrane of 
 the mouth and throat, producing an unnatural thirst which be- 
 comes an enticement to the use of intoxicating liquors. The 
 inflammation of the mouth and throat is apt to extend up the 
 Eustachian tube, thus impairing the sense of hearing. 
 
 But even these are not all the bad effects of tobacco. The 
 inhalation of the poisonous smoke produces unhealthful effects 
 upon the delicate mucous membrane of the bronchial tubes 
 and of the lungs. Upon the former the effect is to produce 
 an irritating cough, with short breath and chronic bronchial 
 catarrh. The pulmonary membrane is congested, taking cold 
 
RESPIRATION. 233 
 
 becomes easy, and recovery from it tedious. Frequently the 
 respiration is seriously disturbed, thus the blood is imperfectly 
 aerated, and so in turn the nutrition of the , entire system is 
 impaired. The cigarette is the defiling medium through which 
 these direful results frequently invade the system, and the 
 easily moulded condition of youth yields readily to the destruc- 
 tive snare. 
 
 " TJie first effect of a cigar upon any one demonstrates that tobacco can poison by 
 its smoke and through the lungs." London Lancet, 
 
 " The action of the heart and lungs is impaired by the influence of the narcotic on 
 the nervous system, but a morbid state of the larynx, trachea, and lungs results from 
 the direct action of the smoke." r DR. LAYCOCK, Professor of Medicine in the 
 University of Edinburgh. 
 
 ADDITIONAL EXPERIMENTS. 
 
 Experiment 114. To illustrate the arrangement of the lungs and the 
 two pleura. Place a large sponge which will represent the lungs in a thin 
 paper bag which just fits it ; this will represent the pulmonary layer of the 
 pleura. Place the sponge and paper bag inside a second paper bag, which 
 will represent the parietal layer of the pleura. Join the mouths of the two 
 bags. The two surfaces of the bags which are now in contact will represent 
 the two moistened surfaces of the pleurae, which rub together in breathing. 
 
 Experiment 115. To show how the lungs may be filled with air. Take 
 one of the lungs saved from Experiment 1 10. Tie a glass tube six inches 
 long into the larynx. Attach a piece of rubber to one end of the glass tube. 
 Now inflate the lung several times, and let it collapse. When distended, 
 examine every part of it. 
 
 Experiment 116. To take your own bodily temperature or that of a 
 friend. If you cannot obtain the use of a physician's clinical thermometer, 
 unfasten one of the little thermometers found on so many calendars and 
 advertising sheets. Hold it for five minutes under the tongue with the lips 
 closed. Read it while in position or the instant it is removed. The natural 
 temperature of the mouth is about 98^ F. 
 
 Experiment 117. To show the vocal cords. Get a pig's windpipe in 
 perfect order, from the butcher, to show the vocal cords. Once secured, it 
 can be kept for an indefinite time in glycerine and water or dilute alcohol. 
 
 Experiment 118. To show that the air we expire is warm. Breathe on 
 a thermometer for a few minutes. The mercury will rise rapidly. 
 
234 
 
 PRACTICAL PHYSIOLOGY. 
 
 Experiment 119. To show that expired air is moist. Breathe on a 
 mirror, or a knife blade, or any polished metallic surface, and note the 
 deposit of moisture. 
 
 Experiment 1 20. To show that the expired air contains carbon dioxtd. Put 
 a glass tube into a bottle of lime water and breathe through the tube. The 
 A liquid will soon become cloudy, because the carbon dioxid 
 
 of the expired air throws down the lime held in solution. 
 
 Experiment 121. "A substitute for a clinical ther- 
 mometer may be readily contrived by taking an ordinary 
 house thermometer from its tin case, and cutting off the 
 lower part of the scale so that the bulb may project freely. 
 With this instrument the pupils may take their own and 
 each other's temperatures, and it will be found that what- 
 ever the season of the year or the temperature of the 
 room, the thermometer in the mouth will record about 
 99 F. Care must, of course, be taken to keep the ther- 
 mometer in the mouth till it ceases to rise, and to read 
 while it is still in position." PROFESSOR H. P. BOWDITCH. 
 
 Experiment 122. To illustrate the manner in which the 
 movements of inspiration cause the air to enter the lungs. 
 Fit up an apparatus, as represented in Fig. 95, in which a 
 stout glass tube is provided with a sound cork, B, and also 
 an air-tight piston, D, resembling that of an ordinary 
 syringe. A short tube, A, passing through the cork, has a 
 small India-rubber bag, C, tied to it. Fit the cork in the 
 tube while the piston is near the top. Now, by lowering 
 the piston we increase the capacity of the cavity containing 
 the bag. The pressure outside the bag is thus lowered, 
 and air rushes into it through the tube, A, till a balance is 
 restored. The bag is thus stretched. As soon as we let 
 the P iston tne elasticity of the bag, being free to act, 
 
 Movements of drives out the air just taken in, and the piston returns to 
 
 Respiration. its former place. 
 
 FIG. 95. 
 
 Apparatus for 
 Illustrating the 
 
 It will be noticed that in this experiment the elastic bag and its tube 
 represent the lungs and trachea; and the glass vessel enclosing it, the 
 thorax. 
 
 For additional experiments on the mechanics of respiration, see Chap- 
 ter XV. 
 
CHAPTER IX. 
 THE SKIN AND THE KIDNEYS. 
 
 232. The Elimination of Waste Products. We have traced 
 the food from the alimentary canal into the blood. We have 
 learned that various food materials, prepared by the diges- 
 tive processes, are taken up by the branches of the portal vein, 
 or by the lymphatics, and carried into the blood current. The 
 nutritive material thus absorbed is conveyed by the blood 
 plasma and the lymph to the various tissues to provide them 
 with nourishment. 
 
 We have learned also that oxygen, taken up in the air cells 
 of the lungs, is being continually carried to the tissues, and that 
 the blood is purified by being deprived in the lungs of its excess 
 of carbon dioxid. From this tissue activity, which is mainly 
 oxidation, are formed certain waste products which, as we have 
 seen, are absorbed by the capillaries and lymphatics and carried 
 into the venous circulation. 
 
 In their passage through the blood and tissues, the albu- 
 mens, sugars, starches, and fats are converted into carbon 
 dioxid, water, and urea, or some closely allied body. Certain 
 articles of food also contain small amounts of sulphur and phos- 
 phorus, which undergo oxidation into sulphates and phosphates. 
 We speak, then, of carbon dioxid, salts, and water as waste 
 products of the animal economy. These leave the body by 
 one of the three main channels, the lungs, the skin, or the 
 kidneys. 
 
 The elimination of these products is brought about by a 
 special apparatus called organs of excretion. The worn-out 
 substances themselves are called excretions, as opposed to 
 
236 
 
 PRACTICAL PHYSIOLOGY. 
 
 secretions, which are elaborated for use in the body. (See 
 note, p. 121.) As already shown, the lungs are the main 
 channels for the elimination of carbon dioxid, and of a portion 
 of water as vapor. By the skin the body gets rid of a small 
 portion of salts, a little carbon dioxid, and a large amount of 
 water in the form of perspiration. From the kidneys are 
 eliminated nearly all the urea and allied bodies, the main 
 
 portion of the salts, and a large 
 amount of water. In fact, practi- 
 cally all the nitrogenous waste 
 leaves the body by the kidneys. 
 
 of the renal epithelium ; S, the skin ; 
 o, oxygen ; h, hydrogen; n, nitrogen. 
 
 233. The Skin. The skin is 
 
 an important and unique organ of 
 the body. It is a blood-purifying 
 organ as truly as are the lungs and 
 the kidneys, while it also performs 
 FIG. 96. -Diagrammatic Scheme to other and complex duties. It is 
 illustrate in a very General Way not merely a protective covering 
 
 Absorption and Excretion. for ^ surface of the body This 
 
 A, represents the alimentary canal ;!-,..,,, . 
 
 the pulmonary surface;K, the surface 1S mdeed the HlOSt apparent, but 
 
 in some respects the least im- 
 portant, of its functions. This 
 protective duty is necessary and efficient, as is proved by the 
 familar experience of the pain when a portion of the outer skin 
 has been removed. 
 
 The skin, being richly supplied with nerves, is an important 
 organ of sensibility and touch. In some parts it is closely 
 attached to the structures beneath, while in others it is less 
 firmly adherent and rests upon a variable amount of fatty 
 tissue. It thus assists in relieving the abrupt projections and 
 depressions of the general surface, and in giving roundness 
 and symmetry to the entire body. The thickness of the skin 
 varies in different parts of the body. Where exposed to pres- 
 
THE SKIN AND THE KIDNEYS. 237 
 
 sure and friction, as on the soles of the feet and in the palms 
 of the hands, it is much thickened. 
 
 The true skin is T ^ to of an inch in thickness, but in certain 
 parts, as in the lips and ear passages, it is often not more than 
 T i^ of an inch thick. At the orifices of the body, as at the 
 mouth, ears, and nose, the skin gradually passes into mucous 
 membrane, the structure of 
 the two being practically 
 identical. As the skin is an 
 outside covering, so is the 
 mucous membrane a more 
 delicate inside lining for all 
 
 Cavities into Which the aper- FIG. 97 - - A Layer of the Cuticle from the 
 tures Open, as the alimentary Palm of the Hand. (Detached by macer- 
 
 canal and the lungs. ation.) 
 
 The skin ranks as an important organ of excretion, its product 
 being sweat, excreted by the sweat glands. The amount of this 
 excretion evaporated from the general surface is very consider- 
 able, and is modified as becomes necessary from the varied con- 
 ditions of the temperature. The skin also plays an important 
 part in regulating the bodily temperature (sec. 241). 
 
 234. The Cutis Vera, or True Skin. The skin is remark- 
 ably complex in its structure, and is divided into two distinct 
 layers, which may be readily separated: the deeper layer, 
 the true skin, dermis, or corium ; and the superficial layer, or 
 outer skin, the epidermis, cuticle, or scarf skin. 
 
 The true skin consists of elastic and white fibrous tissue, 
 the bundles of which interlace in every direction. Throughout 
 this feltwork structure which gradually passes into areolar tis- 
 sue are numerous muscular fibers, as about the hair-follicles 
 and the oil glands. When these tiny muscles contract from 
 cold or by mental emotion, the follicles project upon the surface, 
 producing what is called "goose flesh." 
 
238 PRACTICAL PHYSIOLOGY. 
 
 The true skin is richly supplied with blood-vessels and 
 nerves, as when cut it bleeds freely, and is very sensitive. The 
 surface of the true skin is thrown into a series of minute eleva- 
 tions called the papillae, upon which the outer skin is moulded. 
 These abound in blood-vessels, lymphatics, and peculiar nerve- 
 endings, which will be described in connection with the organ 
 of touch (sec. 314). The papillae are large and numerous in 
 sensitive places, as the palms of the hands, the soles of the 
 feet, and the fingers. They are arranged in parallel curved 
 lines, and form the elevated ridges seen on the surface of the 
 outer skin (Fig. 103). 
 
 235. The Epidermis, or Cuticle. Above the true skin is the 
 epidermis. It is semi-transparent, and under the microscope 
 resembles the scales of a fish. It is this layer that is raised 
 by a blister. 
 
 As the epidermis has neither blood-vessels, nerves, nor lym- 
 phatics, it may be cut without bleeding or pain. Its outer 
 surface is marked with shallow grooves which correspond to 
 the deep furrows between the papillae of the true skin. The 
 inner surface is applied directly to the papillary layer of the 
 true skin, and follows closely its inequalities. The outer skin 
 is made up of several layers of cells, which next to the true 
 skin are soft and active, but gradually become harder towards 
 the surface, where they are flattened and scale-like. The 
 upper scales are continually being rubbed off, and are replaced 
 by deeper cells from beneath. There are new cells continually 
 being produced in the deeper layer, which push upward the 
 cells already existing, then gradually become dry, and are cast 
 off as fine, white dust. Rubbing with a coarse towel after a 
 hot bath removes countless numbers of these dead cells of the 
 outer skin. During and after an attack of scarlet fever the 
 patient " peels," that is, sheds an unusual amount of the scaly 
 cells of the cuticle. 
 
THE SKIN AND THE KIDNEYS. 
 
 239 
 
 The deeper and more active layer of the epidermis, the 
 mucosum, is made up of cells some of which contain minute 
 granules of pigment, or coloring matter, that give color to the 
 skin. The differences in the tint, as brunette, fair, and blond, 
 are due mainly to the amount of coloring matter in these pig- 
 ment cells. In the European this amount is generally small, 
 while in other peoples the color cells may be brown, yellow, or 
 
 FIG. 98. Surface of the Palm of the Hand, showing the Openings of the Sweat 
 Glands and the Grooves between the Papillae of the Skin. (Magnified 4 
 diameters.) [In the smaller figure the same epidermal surface is shown, as 
 seen with the naked eye.] 
 
 even black. The pinkish tint of healthy skin, and the rosy-red 
 after a bath are due, not to the pigment cells, but to the pres- 
 sure of capillaries in the true skin, the color of the blood being 
 seen through the semi-transparent outer skin. 
 
 Experiment 123. Of course the living skin can be examined only in a 
 general way. Stretch and pull it, and notice that it is elastic. Note any 
 liver spots, white scars, moles, warts, etc. Examine the outer skin care- 
 fully with a strong magnifying glass. Study the papillae on the palms. 
 Scrape off with a sharp knife a few bits of the scarf skin, and examine 
 them with the microscope. 
 
 236. The Hair. Hairs varying in size cover nearly the 
 entire body, except a few portions, as the upper eyelids, the 
 palms of the hands, and the soles of the feet. 
 
 The length and diameter of the hairs vary in different per- 
 sons, especially in the long, soft hairs of the head and beard. 
 The average number of hairs upon a square inch of the scalp is 
 about 1000, and the number upon the entire head is estimated 
 as about 120,000. 
 
240 
 
 PRACTICAL PHYSIOLOGY. 
 
 Healthy hair is quite elastic, and may be stretched from 
 one-fifth to one-third more than its original length. An ordi- 
 nary hair from the head will support a weight of six to seven 
 ounces. The hair may become strongly electrified by friction, 
 especially when brushed vigorously in cold, dry weather. An- 
 other peculiarity of the hair is that it readily absorbs moisture. 
 
 237. Structure of the Hair. The hair and the nails are 
 structures connected with the skin, being modified forms of 
 the epidermis. A hair is formed by a depression, or furrow, 
 the inner walls of which consist of the infolded outer skin. 
 This depression takes the form of a sac and 
 is called the hair-follicle, in which the roots 
 of the hair are embedded. At the bottom 
 of the follicle there is an upward projec- 
 tion of the true skin, a papilla, which con- 
 tains blood-vessels and nerves. It is covered 
 with epidermic cells which multiply rapidly, 
 thus accounting for the rapid growth of the 
 hair. Around each papilla is a bulbous 
 expansion, the hair bulb, from which the 
 hair begins to grow. 
 
 The cells on the papilla are the means by 
 which the hairs grow. As these are pushed 
 upwards by new ones formed beneath, they 
 are compressed, and the shape of the follicle 
 determines their cylindrical growth, the shaft 
 of the hair. So closely are these cells welded to form the 
 cylinder, that even under a microscope the hair presents only a 
 fibrous appearance, except in the center, where the cells are 
 larger, forming the medulla, or pith (Fig. 106). 
 
 The medulla of the hair contains the pigment granules or 
 coloring matter, which may be of any shade between a light 
 yellow and an intense black. It is this that gives the great 
 
 FIG. 99. Epidermis 
 of the Foot. 
 
 It will be noticed that 
 there are only a few 
 orifices of the sweat 
 glands in this region. 
 (Magnified 8 diam- 
 eters.) 
 
THE SKIN AND THE KIDNEYS. 
 
 2 4 I 
 
 variety in color. Generally with old people the pigment is 
 absent, the cells being occupied by air; hence the hair becomes 
 gray or white. The thin, flat scales on the surface of the hair 
 overlap like shingles. Connected with the hair-follicles are 
 small bundles of muscular fibers, which run 
 obliquely in the skin and which, on shorten- 
 ing, may cause the hairs to become more 
 upright, and thus are made to " stand on 
 end." The bristling back of an angry cat 
 furnishes a familiar illustration of this mus- 
 cular action. 
 
 Opening into each hair-follicle are usually 
 one or more sebaceous, or oil, glands. 
 These consist of groups of minute pouches 
 lined with cells producing an oily material 
 which serves to oil the hair and keep the 
 skin moist and pliant. 
 
 238. The Nails. The nails are also 
 formed of epidermis cells which have 
 undergone compression, much like those 
 forming the shaft of a hair. In other 
 words, a nail is simply a thick layer of 
 horny scales built from the outer part of 
 the scarf skin. The nail lies upon very 
 fine and closely set papillae, forming its 
 matrix, or bed. It is covered at its base 
 with a fold of the true skin, called its root, 
 from beneath which it seems to grow. 
 
 The growth of the nail, like that of the hair and the outer 
 skin, is effected by the production of new cells at the root and 
 under surface. The growth of each hair is limited ; in time it 
 falls out and is replaced by a new one. But the nail is kept 
 of proper size simply by the removal of its free edge. 
 
 FIG. loo. Hair and 
 
 Hair-Follicle. 
 A, root of hair; B, bulb of 
 the hair ; C, internal root 
 sheath; D, external root 
 sheath ; E, external mem- 
 brane of follicle ; F, mus- 
 cular fibers attached to 
 the follicle ; H, compound 
 sebaceous gland with its 
 duct, K ; L, simple seba- 
 ceous gland; M, opening 
 of the hair-follicle. 
 
242 
 
 PRACTICAL PHYSIOLOGY. 
 
 239. The Sweat Glands. Deep in the substance of the 
 true skin, or in the fatty tissue beneath it, are the sweat glands. 
 Each gland consists of a single tube with a blind end, coiled in 
 a sort of ball about ^ of an inch in diameter. From this coil 
 the tube passes upwards through the dermis in a wavy course 
 until it reaches the cuticle, which it penetrates with a number 
 of spiral turns, at last opening on the surface. The tubes con- 
 sist of delicate walls of membrane lined with cells. The coil of 
 
 FIG. 101. Concave or Adher- 
 ent Surface of the Nail. 
 
 A, border of the root ; B, whitish 
 portion of semi-lunar shape 
 (the lunula); C, body of nail. 
 The continuous line around 
 border represents the free 
 edge. 
 
 FIG. 1 02. Nail in Position. 
 A, section of cutaneous fold (B) turned back 
 to show the root of the nail ; B, cutaneous 
 fold covering the root of the nail; C, 
 semi-lunar whitish portion (lunula); D, 
 free border. 
 
 the gland is enveloped by minute blood-vessels. The cells of 
 the glands are separated from the blood only by a fine partition, 
 and draw from it whatever supplies they need for their special 
 work. 
 
 With few exceptions every portion of the skin is provided 
 with sweat glands, but they are not equally distributed over 
 the body. They are fewest in the back and neck, where it is 
 estimated they average 400 to the square inch. They are 
 thickest in the palms of the hands, where they amount to 
 nearly 3000 to each square inch. These minute openings 
 occur in the ridges of the skin, and may be easily seen with a 
 hand lens. The length of a tube when straightened is about 
 
THE SKIN AND THE KIDNEYS. 243 
 
 of an inch. The total number in the body is estimated at 
 about 2,500,000, thus making the entire length of the tubes 
 devoted to the secretion of sweat about 10 miles. 
 
 240. Nature and Properties of Sweat. The sweat is a 
 
 turbid, saltish fluid with a feeble but characteristic odor due to 
 certain volatile fatty acids. Urea is always present in small 
 quantities, and its proportion may be largely increased when 
 there is deficiency of elimination by the kidneys. Thus it is 
 often observed that the sweat is more abundant when the kid- 
 neys are inactive, and the reverse is true. This explains the 
 increased excretion of the kidneys in cold weather. Of the 
 inorganic constituents of sweat, common salt is the largest 
 and most important. Some carbon dioxid passes out through 
 the skin, but not more than -fa as much as escapes by the 
 lungs. 
 
 The sweat ordinarily passes off as vapor. If there is no 
 obvious perspiration we must not infer that the skin is inactive, 
 since sweat is continually passing from the surface, though 
 often it may not be apparent. On an average from i- to 4 
 pounds of sweat are eliminated daily from the skin in the form 
 of vapor. This is double the amount excreted by the lungs, 
 and averages about ^ T of the weight of the body. 
 
 The visible sweat, or sensible perspiration, becomes abundant 
 during active exercise, after copious drinking of cold water, on 
 taking certain drugs, and when the body is exposed to exces- 
 sive warmth. Forming more rapidly than it evaporates it col- 
 lects in drops on the surface. The disagreeable sensations 
 produced by humid weather result from the fact that the 
 atmosphere is so loaded with vapor that the moisture of the 
 skin is slowly removed by evaporation. 
 
 Experiment 124. Study the openings of the sweat glands with the aid 
 of a strong magnifying glass. They are conveniently examined on the 
 palms. 
 
244 PRACTICAL PHYSIOLOGY. 
 
 A man's weight may be considerably reduced within a short 
 time by loss through the perspiration alone. This may explain 
 to some extent the weakening effect of profuse perspiration, as 
 from night sweats of consumption, convalescence from typhoid 
 fever, or the artificial sweating from taking certain drugs. 
 
 241. The Skin as a Regulator of the Temperature of the 
 Body. We thus learn that the skin covers and protects the 
 more delicate structures beneath it ; and that it also serves as 
 an important organ of excretion. By means of the sweat the 
 skin performs a third and a most important function, viz., that 
 of regulating the temperature of the body. 
 
 The blood-vessels of the skin, like those of other parts of 
 the body, are under the control of the nervous system, which 
 regulates their diameter. If the nervous control be relaxed, 
 the blood-vessels dilate, more blood flows through them, and 
 more material is brought to the glands of the skin to be acted 
 upon. External warmth relaxes the skin and its blood-vessels. 
 There results an increased flow of blood to the skin, with in- 
 creased perspiration. External cold, on the other hand, con- 
 tracts the skin and its blood-vessels, producing a diminished 
 supply of blood and a diminished amount of sweat. 
 
 Now, it is a law of physics that the change from liquid to 
 vapor involves a loss of heat. A few drops of ether or of any 
 volatile liquid placed on the skin, produce a marked sense of 
 coldness, because the heat necessary to change the liquid into 
 vapor has been drawn rapidly from the skin. This principle 
 holds good for every particle of sweat that reaches the mouth 
 of a sweat gland. As the sweat evaporates, it absorbs a cer- 
 tain amount of heat, and cools the body to that extent. 
 
 242. How the Action of the Skin may be Modified. After 
 profuse sweating we feel chilly from the evaporation of a large 
 amount of moisture, which rapidly cools the surface. When 
 the weather is very warm the evaporation tends to prevent the 
 
THE SKIN AND THE KIDNEYS. 
 
 245 
 
 bodily temperature from rising. On the other hand, if the 
 weather be cold, much less sweat is produced, the loss of heat 
 from the body is greatly lessened, and its temperature pre- 
 vented from falling. Thus it is plain why medicine is given 
 and other efforts are made to sweat the fever patient. The 
 increased activity of the skin helps to reduce the bodily heat. 
 
 The sweat glands are under the control of certain nerve 
 fibers originating in the spinal 
 cord, and are not necessarily 
 excited to action by an in- 
 creased flow of blood through 
 the skin. In other words, the 
 sweat glands may be stimulated 
 to increased action both by an 
 increased flow of blood, and 
 also by reflex action upon the 
 vaso-dilator nerves of the parts. 
 These two agencies, while work- 
 ing in harmony through the 
 vaso-dilators, produce phenom- 
 ena which are essentially inde- 
 pendent of each other. Thus 
 a strong emotion, like fear, may 
 cause a profuse sweat to break out, with cold, pallid skin. 
 During a fever the skin may be hot, and its vessels full of blood, 
 and yet there may be no perspiration. 
 
 The skin may have important uses with which we are not 
 yet acquainted. Death ensues when the heat of the body has 
 been reduced to about 70 F., and suppression of the action of 
 -the skin always produces a lowering of the temperature. Warm- 
 blooded animals usually die when more than half of the general 
 surface has been varnished. Superficial burns which involve 
 a large part of the surface of the body, generally have a fatal 
 result due to shock. 
 
 FIG. 103. Papillae of the Skin of the 
 Palm of the Hand. 
 
 In each papilla are seen vascular loops (dark 
 lines) running up from the vascular net- 
 work below; the tactile corpuscles with 
 their nerve branches (white lines) which 
 supply the papillae. 
 
246 
 
 PRACTICAL PHYSIOLOGY. 
 
 If the skin be covered with some air-tight substance like a 
 coating of varnish, its functions are completely arrested. The 
 bodily heat falls very rapidly. Symptoms of blood-poisoning 
 arise, and death soon ensues. The reason 
 is not clearly known, unless it be from the 
 sudden retention of poisonous exhalations. 
 
 243. The Skin and the Kidneys. There 
 is a close relationship between the skin and 
 the kidneys, as both excrete organic and 
 saline matter. In hot weather, or in con- 
 ditions producing great activity of the skin, 
 the amount of water excreted by the kid- 
 neys is diminished. This is shown in the 
 case of firemen, stokers, bakers, and others 
 who are exposed to great heat, and drink 
 heavily and sweat profusely, but do not 
 have a relative increase in the functions of 
 the kidneys. In cool weather, when the 
 skin is less active, a large amount of water 
 is excreted by the kidneys, as is shown by 
 the experience of those who drive a long 
 distance in severe weather, or who have 
 caught a sudden cold. 
 
 244. Absorbent Powers of the Skin. 
 The skin serves to some extent as an 
 organ for absorption. It is capable of 
 absorbing certain substances to which it is 
 
 freely exposed. Ointments rubbed in, are absorbed by the 
 lymphatics in those parts where the skin is thin, as in the bend 
 of the elbow or knee, and in the armpits. Physicians use medi- 
 cated ointments in this way, when they wish to secure prompt 
 and efficient results. Feeble infants often grow more vigorous 
 by having their skin rubbed vigorously daily with olive oil. 
 
 FIG. 104. Magnified 
 View of a Sweat Gland 
 with its Duct. 
 
 The convoluted gland is 
 seen surrounded with big 
 fat -cells, and may be 
 traced through the der- 
 mis to its outlet in the 
 horny layers of the epi- 
 dermis. 
 
THE SKIN AND THE KIDNEYS. 
 
 A slight amount of water is absorbed in bathing. Sailors 
 deprived of fresh water have been able to allay partially their 
 intense thirst by soaking their clothing in salt water. The 
 extent to which absorption occurs through the healthy skin is, 
 however, quite limited. If the outer skin be removed from 
 parts of the body, the exposed surface absorbs rapidly. Vari- 
 ous substances may thus be absorbed, and rapidly passed into 
 the blood. When the physician wishes remedies to act through 
 the skin, he sometimes raises a small blister, and dusts over 
 the surface some drug, a fine powder, like morphine. 
 
 The part played by the skin as an organ of touch will be 
 considered in sections 314 and 315. 
 
 Experiment 125. To illustrate the sense of temperature. Ask the person 
 to close his eyes. Use two test tubes, one filled with cold and the other 
 with hot water, or two spoons, one hot and one cold. Apply each to 
 different parts of the surface, and ask the person whether the touching body 
 is hot or cold. Test roughly the sensibility of different parts of the body 
 with cold and warm metallic-pointed rods. 
 
 Experiment 126. Touch fur, wood, and metal. The metal feels coldest, 
 although all the objects are at the same temperature. Why? 
 
 Experiment 127. Plunge the hand into water at about 97 F. One ex- 
 periences a feeling of heat. Then plunge it into water at about 86 F. ; at 
 first it feels cold, because heat is abstracted from the hand. Plunge the 
 other hand direct into water at 86 F. without previously placing it in water 
 at 97 F., it will feel pleasantly warm. 
 
 Experiment 128. To illustrate warm and cold spots. With a blunt me- 
 tallic point, touch different parts of the skin. Certain points excite the 
 sensation of warmth, others of cold, although the temperatures of the skin 
 and of the instrument remain constant. 
 
 245. Necessity for Personal Cleanliness. It is evident that 
 the skin, with its myriads of blood-vessels, nerves, and sweat and 
 oil glands, is an exceedingly complicated and important struc- 
 ture. The surface is continually casting off perspiration, oily 
 material, and dead scales. By friction and regular bathing we 
 
248 PRACTICAL PHYSIOLOGY. 
 
 get rid of these waste materials. If this be not thoroughly 
 done, the oily secretion holds the particles of waste substances 
 to the surface of the body, while dust and dirt collect, and 
 form a layer upon the skin. When we remember that this 
 dirt consists of a great variety of dust particles, poisonous 
 matters, and sometimes germs of disease, we may well be im- 
 pressed with the necessity of personal cleanliness. 
 
 This layer of foreign matter on the skin is in several ways 
 injurious to health. It clogs the pores and retards perspira- 
 tion, thus checking the proper action of the skin as one of the 
 chief means of getting rid of the waste matters of the body. 
 Hence additional work is thrown upon other organs, chiefly the 
 lungs and the kidneys, which already have enough to do. This 
 extra work they can do for only a short time. Sooner or later 
 they become disordered, and illness follows. Moreover, as 
 this unwholesome layer is a fertile soil in which bacteria may 
 develop, many skin diseases may result from this neglect. It 
 is also highly probable that germs of disease thus adherent to 
 the skin may then be absorbed into the system. Parasitic 
 skin diseases are thus greatly favored by the presence of an 
 unclean skin. It is also a fact that uncleanly people are more 
 liable to take cold than those who bathe often. 
 
 The importance of cleanliness would thus seem too apparent 
 to need special mention, were it not that the habit is so much 
 neglected. The old and excellent definition that dirt is suitable 
 matter, but in the wrong place, suggests that the place should 
 be changed. This can be done only by regular habits of per- 
 sonal cleanliness, not only of the skin, the hair, the teeth, the 
 nails, and the clothing, but also by the rigid observance of 
 a proper system in daily living. 
 
 246. Baths and Bathing. In bathing we have two distinct 
 objects in view, to keep the skin clean and to impart vigor. 
 These are closely related, for to remove from the body worn- 
 
THE SKIN AND THE KIDNEYS. 249 
 
 out material, which tends to injure it, is a direct means of giv- 
 ing vigor to all the tissues. Thus a cold bath acts upon the 
 nervous system, and calls out, in response to the temporary 
 abstraction of heat, a freer play of the general vital powers. 
 Bathing is so useful, both locally and constitutionally, that it 
 should be practiced to such an extent as experience proves to 
 be beneficial. For the general surface, the use of hot water 
 once a week fulfills the demands of cleanliness, unless in 
 special occupations. Whether we should bathe in hot or cold 
 water depends upon circumstances. Most per- 
 sons, especially the young and vigorous, soon 
 become accustomed to cool, and even cold water 
 baths, at all seasons of the year. 
 
 The hot bath should be taken at night before 
 going to bed, as in the morning there is usually 
 more risk of taking cold. The body is readily 
 chilled, if exposed to cold when the blood-vessels FlG ' "S E jf 
 
 thelial Cells 
 
 of the skin have been relaxed by heat. Hot from the Sweat 
 baths, besides their use for the purposes of Glands, 
 cleanliness, have a sedative influence upon the The ceils are very 
 nervous system, tending to allay restlessness and 
 weariness. They are excellent after severe mentary 
 physical or mental work, and give a feeling of 
 restful comfort like that of sleep. 
 
 Cold baths are less cleansing than hot, but serve as an ex- 
 cellent tonic and stimulant to the bodily functions. The best 
 and most convenient time for a cold bath is in the morning, 
 immediately after rising. To the healthy and vigorous, it is, if 
 taken at this time, with proper precautions, a most agreeable 
 and healthful luxury. The sensation of chilliness first felt is 
 caused by the contraction of the skin and its blood-vessels, so 
 that the blood is forced back, as it were, into the deeper parts 
 of the body. This stimulates the nervous system, the breath- 
 ing becomes quicker and deeper, the heart beats more vigor- 
 
25O PRACTICAL PHYSIOLOGY. 
 
 ously, and, as a consequence, the warm blood is sent back to 
 the skin with increased force. This is known as the stage of 
 reaction, which is best increased by friction with a rough towel. 
 This should produce the pleasant feeling of a warm glow all 
 over the body. 
 
 A cold bath which is not followed by reaction is likely to do 
 more harm than good. The lack of this reaction may be due 
 to the water being too cold, the bath too prolonged, or to the 
 bather being in a low condition of health. In brief, the ruddy 
 glow which follows a cold bath is the main secret of its favor- 
 able influence. 
 
 The temperature of the water should be adapted to the age 
 and strength of the bather. The young and robust can safely 
 endure cold baths, that would be of no benefit but indeed an 
 injury to those of greater age or of less vigorous conditions of 
 health. After taking a bath the skin should be rapidly and 
 vigorously rubbed dry with a rough towel, and the clothing at 
 once put on. 
 
 247. Rules and Precautions in Bathing. Bathing in cold 
 water should not be indulged in after severe exercise or great 
 fatigue, whether we are heated or not. Serious results have 
 ensued from cold baths when the body is in a state of exhaus- 
 tion or of profuse perspiration. A daily cold bath when the 
 body is comfortably warm, is a safe tonic for almost all persons 
 during the summer months, and tends especially to restore the 
 appetite. Cold baths, taken regularly, render persons who are 
 susceptible to colds much less liable to them, and less likely 
 to be disturbed by sudden changes of temperature. Persons 
 suffering from heart disease or from chronic disease of any 
 important organ should not indulge in frequent cold baths, 
 except by medical advice. Owing to the relaxing nature of 
 hot baths, persons with weak hearts or suffering from debility 
 may faint while taking them. 
 
THE SKIN AND THE KIDNEYS. 
 
 251 
 
 Outdoor bathing should not be taken for at least an hour 
 after a full meal, and except for the robust it is not prudent to 
 bathe with the stomach empty, especially before breakfast. It 
 is a wise rule, in outdoor or sea bathing, to come out of the 
 water as soon as the glow of reaction is felt. It is often advis- 
 able not to apply cold water very freely to the head. Tepid or 
 even hot water is preferable, especially by those subject to 
 severe mental strain. But it is often 
 a source of great relief during men- 
 tal strain to bathe the face, neck, 
 and chest freely at bedtime with 
 cold water. It often proves efficient 
 at night in calming the sleeplessness 
 which results from mental labor. 
 
 Hot baths, if taken at bedtime, 
 are often serviceable in preventing 
 a threatened cold or cutting it short, 
 the patient going immediately to 
 bed, with extra clothing and hot 
 drinks. The free perspiration in- 
 duced helps to break up the cold. 
 
 Salt water acts more as a stimu- 
 lant to the skin than fresh water. 
 Salt-water bathing is refreshing 
 and invigorating for those who are 
 healthy, but the bather should come 
 out of the water the moment there 
 is the slightest feeling of chilliness. 
 The practice of bathing in salt 
 water more than once a day is unhealthful, and even dangerous. 
 Only the strongest can sustain so severe a tax on their power 
 of endurance. Sea bathing is beneficial in many ways for 
 children, as their skin reacts well after it. In all cases, brisk 
 rubbing with a rough towel should be had afterwards. 
 
 FIG. 106. Magnified Section of 
 the Lower Portion of a Hair 
 and Hair-Follicle. 
 
 A, membrane of the hair-follicle, cells 
 with nuclei and pigmentary gran- 
 ules; B, external lining of the root 
 sheath ; C, internal lining of the 
 root sheath; D, cortical or fibrous 
 portion of the hair shaft ; E, medul- 
 lary portion (pith) of shaft ; F, hair- 
 bulb, showing its development from 
 cells from A. 
 
PRACTICAL PHYSIOLOGY. 
 
 The golden rule of all bathing is that it must never be fol- 
 lowed by a chill. If even a chilliness occur after bathing, it 
 must immediately be broken up by some appropriate methods, 
 as lively exercise, brisk friction, hot drinks, and the application 
 of heat. 
 
 Swimming is a most valuable accomplishment, combining 
 bathing and exercise. Bathing of the feet should never be 
 neglected. Cleanliness pf the hair is also another matter 
 requiring strict attention, especially in children. 
 
 248. Care of the Hair and Nails. The hair brush should not be 
 too stiff, as this increases the tendency towards scurfiness of the 
 
 head. If, however, the hair is brushed 
 too long or too hard, the scalp is greatly 
 stimulated, and an increased production of 
 scurf may result. If the head be washed 
 too often with soap its natural secretion is 
 checked, and the scalp becomes dry and 
 
 scaly. The various hair pomades are as a 
 
 FIG. 107. Longitudinal Sec- 
 
 tion of a Finger-Nail. rule undesirable and unnecessary. 
 
 A, last phalanx of the fingers; B, Th e nails should be kept in proper con- 
 true skin on the dorsal surface ditiori, else they are not only unsightly, but 
 
 of the finger; C epidermis ; D, serye ^ ^ f f d j 
 
 true skin ; E, bed of the nail ; ' 
 
 F, superficial layer of the nail; The nails are often injured by too much 
 
 H, true skin of the pulp of the interference, and should never be trimmed 
 
 to the quick. The upper surfaces should 
 
 on no account be scraped. The nail-brush is sufficient to cleanse 
 them without impairing their smooth and polished surfaces. 
 
 249. Use of Clothing. The chief use of clothing, from a 
 hygienic point of view, is to assist in keeping the body at a 
 uniform temperature. It also serves for protection against 
 injury, and for personal adornment. The heat of the body, as 
 we have learned, is normally about 98^ F, This varies but 
 slightly in health. A rise of temperature of more than one 
 degree is a symptom of disturbance. The normal temperature 
 
THE SKIN AND THE KIDNEYS. 253 
 
 does not vary with the season. In summer it is kept down by 
 the perspiration and its rapid evaporation. In winter it is 
 maintained by more active oxidation, by extra clothing, and by 
 artificial heat. 
 
 The whole matter of clothing is modified to a great extent 
 by climatic conditions and local environments, topics which 
 do not come within the scope of this book. 
 
 250. Material Used for Clothing. It is evident that if clothing 
 is to do double duty in preventing the loss of heat by radiation, and 
 in protecting us from the hot rays of the sun, some material must be 
 used that will allow the passage of heat in either direction. The 
 ideal clothing should be both a bad conductor and a radiator of heat. 
 At the same time it must not interfere with the free evaporation of 
 the perspiration, otherwise chills may result from the accumulation 
 of moisture on the surface of the body. 
 
 Wool is a bad conductor, and should be worn next the skin, both 
 in summer and winter, especially in variable climates. It prevents, 
 better than any other material, the loss of heat from the body, and 
 allows free ventilation and evaporation. Its fibers are so lightly 
 woven that they make innumerable meshes enclosing air, which is one 
 of the best of non-conductors. 
 
 Silk ranks next to wool in warmth and porosity. It is much softer 
 and less irritating than flannel or merino, and is very useful for sum- 
 mer wear. The practical objection to its general use is the expense. 
 Fur ranks with wool as a bad conductor of heat It does not, how- 
 ever, like wool, allow of free evaporation. Its use in cold countries 
 is universal, but in milder climates it is not much worn. 
 
 Cotton and linen are good conductors of heat, but are not absorb- 
 ents of moisture, and should not be worn next the skin. They are, 
 however, very durable and easily cleansed. As an intermediate 
 clothing they may be worn at all seasons, especially over wool or 
 silk. Waterproof clothing is also useful as a protection, but should 
 not be worn a longer time than necessary, as it shuts in the perspira- 
 tion, and causes a sense of great heat and discomfort. 
 
 The color of clothing is of some importance, especially if exposed 
 directly to the sun's rays. The best reflectors, such as white and 
 
254 PRACTICAL PHYSIOLOGY. 
 
 light gray clothing, absorb comparatively little heat and are the 
 coolest, while black or dark-colored materials, being poor reflectors 
 and good absorbents, become very warm. 
 
 251. Suggestions for the Use of Clothing. Prudence and 
 good sense should guide us in the spring, in changing winter 
 flannels or clothing for fabrics of lighter weight. With the 
 fickle climate in most sections of this country, there are great 
 risks of severe colds, pneumonia, and other pulmonary diseases 
 from carelessness or neglect in this matter. A change from 
 heavy to lighter clothing should be made first in the outer gar- 
 ments, the underclothing being changed very cautiously. 
 
 The two essentials of healthful clothing are cleanliness and 
 dryness. To wear garments that are daily being soiled by 
 perspiration and other cutaneous excretions, is a most uncleanly 
 and unhealthful practice. Clothing, especially woolen under- 
 clothing, should be frequently changed. One of the objections 
 to the use of this clothing is that it does not show soiling to 
 the same extent as do cotton and linen. 
 
 Infectious and contagious diseases may be conveyed by the 
 clothing. Hence, special care must be taken that all clothing 
 in contact with sick people is burned or properly disinfected. 
 Children especially are susceptible to scarlet fever, diphtheria, 
 and measles, and the greatest care must be exercised to pre- 
 vent their exposure to infection through the clothing. 
 
 We should never sleep in a damp bed, or between damp 
 sheets. The vital powers are enfeebled during sleep, and there 
 is always risk of pneumonia or rheumatism. The practice of 
 sitting with wet feet and damp clothing is highly injurious to 
 health. The surface of the body thus chilled may be small, 
 yet there is a grave risk of serious, if not of fatal, disease. No 
 harm may be done, even with clothing wet with water or damp 
 with perspiration, so long as exercise is maintained, but the 
 failure or inability to change into dry garments as soon as the 
 body is at rest is fraught with danger. 
 
THE SKIN AND THE KIDNEYS. 255 
 
 Woolen comforters, scarfs, and fur mufflers, so commonly 
 worn around the neck, are more likely to produce throat trou- 
 bles and local chill than to have any useful effect. Harm 
 ensues from the fact that the extra covering induces local 
 perspiration, which enfeebles the natural defensive power of 
 the parts ; and when the warmer covering is removed, the per- 
 spiring surface is readily chilled. Those who never bundle 
 their throats are least liable to suffer from throat ailments. 
 
 252. Ill Effects of WearingTightly Fitting Clothing. The 
 
 injury to health caused by tight lacing, when carried to an 
 extreme, is due to the compression and displacement of vari- 
 ous organs by the pressure exerted on them. Thus the lungs 
 and the heart may be compressed, causing short breath on 
 exertion, palpitation of the heart, and other painful and danger- 
 ous symptoms. The stomach, the liver, and other abdominal 
 organs are often displaced, causing dyspepsia and all its atten- 
 dant evils. The improper use of corsets, especially by young 
 women, is injurious, as they interfere with the proper develop- 
 ment of the chest and abdominal organs. The use of tight 
 elastics below the knee is often injurious. They obstruct the 
 local venous circulation and are a fruitful source of cold feet 
 and of enlarged or varicose veins. 
 
 Tightly fitting boots and shoes often cause corns, bunions, 
 and ingrowing nails ; on the other hand, if too loosely worn, 
 they cause corns from friction. Boots too narrow in front 
 crowd the toes together, make them overlap, and render walk- 
 ing difficult and painful. High-heeled boots throw the weight 
 of the body forwards, so that the body rests too much on the 
 toes instead of on the heels, as it should, thus placing an undue 
 strain upon certain groups of muscles of the leg, in order to 
 maintain the balance, while other groups are not sufficiently 
 exercised. Locomotion is never easy and graceful, and a firm, 
 even tread cannot be expected. 
 
256 PRACTICAL PHYSIOLOGY. 
 
 The compression of the scalp by a tight-fitting hat interferes 
 with the local circulation, and may cause headaches, neuralgia, 
 or baldness, the nutrition of the hair-follicles being diminished 
 by the impaired circulation. The compression of the chest and 
 abdomen by a tight belt and various binders interferes with the 
 action of the diaphragm, the most important muscle of 
 respiration. 
 
 253. Miscellaneous Hints on the Use of Clothing. Chil- 
 dren and old people are less able to resist the extreme changes 
 of temperature than are adults of an average age. Special care 
 should be taken to provide children-with woolen underclothing, 
 and to keep them warm and in well-ventilated rooms. Neither 
 the chest nor limbs of young children should be unduly ex- 
 posed, as is often done, to the cold blasts of winter or the 
 fickle weather of early spring. Very young children should 
 not be taken out in extremely cold weather, unless quite warmly 
 clad and able to run about. The absurd notion is often enter- 
 tained that children should be hardened by exposure to the 
 cold. Judicious "hardening" means ample exposure of well- 
 fed and well-clothed children. Exposure of children not thus 
 cared for is simple cruelty. The many sicknesses of children, 
 especially diseases of the throat and lungs, may often be traced 
 directly to gross carelessness, ignorance, or neglect with refer- 
 ence to undue exposure. The delicate feet of children should 
 not be injured by wearing ill-fitting or clumsy boots or shoes. 
 Many deformities of the feet, which cause much vexation and 
 trouble in after years, are acquired in early life. 
 
 No one should sleep in any of the clothes worn during the 
 day, not even in the same underclothing. All bed clothing 
 should be properly aired, by free exposure to the light and air 
 every morning. Never wear wet or damp clothing one moment 
 longer than necessary. After it is removed rub the body thor- 
 oughly, put on at once dry, warm clothing, and then exercise 
 
THE SKIN AND THE KIDNEYS. 
 
 vigorously for a few minutes, until a genial glow is felt. . Neg- 
 lect of these precautions often results in rheumatism, neuralgia, 
 and diseases of the chest, especially among delicate people and 
 young women. 
 
 Pupils should not be allowed to sit in the schoolroom with 
 any outer garments on. A person who has become heated in 
 a warm room should not expose himself to cold without extra 
 clothing. We must not be in a hurry to put on heavy clothes 
 for winter, but having once worn them, they must not be left 
 off until milder weather renders the change safe. The cheaper 
 articles of clothing are often dyed with lead or arsenic. 
 Hence such garments, like stockings and colored underclothing, 
 worn next the skin have been known to produce severe symp- 
 toms of poisoning. As a precaution, all such articles should be 
 carefully washed and thoroughly rinsed before they are worn. 
 
 THE KIDNEYS. 
 
 254. The Kidneys. The kidneys are two important organs 
 in the abdomen, one on each side of the spine. They are of a 
 reddish-brown color, and are enveloped by a transparent cap- 
 sule made up of a fold of the peritoneum. Embedded in fat, 
 the kidneys lie between the upper lumbar vertebrae, and the 
 crest of the hip bone. The liver is above the right kidney, 
 and the spleen above the left, while both lie close against the 
 rear wall of the abdomen, with the intestines in front of them. 
 The human kidneys, though somewhat larger, are exactly of 
 the same shape, color, and general appearance as those of the 
 sheep, so commonly seen in the markets. 
 
 The kidneys are about four inches long, two inches across, one 
 inch thick, and weigh from 4^ to 5^ ounces each. The hollow 
 or concave side of the kidneys is turned inwards, and the deep 
 fissure of this side, known as the hilus, widens out to form the 
 pelvis. Through the hilus the renal artery passes into each 
 
2 5 8 
 
 PRACTICAL PHYSIOLOGY. 
 
 kidney, and from each hilus passes outwards the renal vein, a 
 branch of the inferior vena cava. 
 
 A tube, called the ureter, passes out from the concave bor- 
 der of each kidney, turns downwards, and enters the bladder 
 
 in the basin of the pelvis. 
 This tube is from 12 to 14 
 inches long, about as large 
 as a goose quill, and conveys 
 the secretion of the kidneys 
 to the bladder. 
 
 255. Structure of the 
 Kidneys. The pelvis is sur- 
 rounded by reddish cones, 
 about twelve in number, pro- 
 jecting into it, called the 
 pyramids of Malpighi. The 
 apices of these cones, known 
 as the papilla, are crowded 
 with minute openings, the 
 mouths of the uriniferous 
 
 tubules, which form the sub- 
 FIG. 108 Vertical Section of the Kidney. gtance Q the kidney> These 
 A, pyramids of Malpighi ; B, apices, or papillae, ,. ., , . , , ,, 
 
 of the pyramids, surrounded by subdivisions of ll6 Parallel in the medullary 
 the pelvis known as cups or calices ; C, pelvis or Central Structure, but On 
 of the kidney : D, upper end of ureter. , . , , 
 
 reaching the cortical or outer 
 
 layer, they wind about and interlace, ending, at last, in dilated 
 closed sacs called Malpighian capsules. 
 
 256. Function of the Kidneys. The Malpighian capsules 
 are really the beginning of the tubules, for here the work of 
 excretion begins. The thin wall of the capillaries within each 
 capsule separates the blood from the cavity of the tubule. The 
 blood-pressure on the delicate capillary walls causes the exuda- 
 tion of the watery portions of the blood through the cell walls 
 
THE SKIN AND THE KIDNEYS. 259 
 
 into the capsule. The epithelial cell membrane allows the water 
 of the blood with certain salts in solution to pass, but rejects the 
 albumen. From the capsules, the excretion passes through the 
 tubules into the pelvis, and on through the ureters to the bladder. 
 But the "delicate epithelial walls of the tubules through which it 
 passes permit the inflow of urea and other waste products from 
 the surrounding capillaries. By this twofold process are separ- 
 ated from the blood the fluid portions of the renal secretion 
 with soluble salts, and the urea with other waste material. 
 
 257. How the Action of the Kidneys may be Modified. The 
 
 action of the kidneys is subject to very marked and sudden modifica- 
 tions, especially those operating through the nervous system. Thus 
 whatever raises the blood-pressure in the capillaries of the capsules, 
 will increase the quantity of fluid filtering through them. That is, the 
 watery portion of the secretion will be increased without necessarily 
 adding to its solids. So anything which lowers the blood-pressure 
 will diminish the watery portion of the secretion, that is, the secre- 
 tion will be scanty, but concentrated. 
 
 The Renal Secretion. The function of the kidneys is to secrete a fluid com- 
 monly known as the urine. The average quantity passed in 24 hours by an adult 
 varies from 40 to 60 fluid ounces. Normal urine consists of about 96 per cent 
 of water and 4 per cent of solids. The latter consist chiefly of certain nitrogenous 
 substances known as urea and uric acid, a considerable quantity of mineral salts, 
 and some coloring matter. Urea, the most important and most abundant constit- 
 uent of urine, contains the four elements, but nitrogen forms one-half its weight. 
 While, therefore, the lungs expel carbon dioxid chiefly, the kidneys expel nitrogen. 
 Both of these substances express the result of oxidations going on in the- body. 
 The urea and uric acids represent the final result of the breaking down in the body 
 of nitrogenous substances, of which albumen is the type. 
 
 Unusual constituents of the urine are albumen, sugar, and bile. When albumen 
 is present in urine, it often indicates some disease of the kidneys, to which the 
 term albuminuria or Bright's Disease is applied. The presence of grape sugar or 
 glucose indicates the disease known as diabetes. Bile is another unusual constituent 
 of the urine, appearing \VL jaundice. 
 
 The bladder is situated in the pelvic cavity or in the lowest part of the abdomen. 
 When full, the bladder is pear-shaped ; when empty, it is collapsed and lies low in 
 the pelvis. The functions of the bladder are to collect and retain the urine, which 
 has reached it drop by drop from the kidneys through the ureters, until a certain 
 quantity accumulates, and then to expel it from the body. 
 
260 
 
 PRACTICAL PHYSIOLOGY. 
 
 In the kidneys, as elsewhere, the vaso-motor nerves are distributed 
 to the walls of the blood-vessels, and modify the quantity and the 
 pressure of blood in these organs. Thus, some strong emotion, like 
 
 FIG. 109. Vertical Section of the Back. (Showing kidneys in situ and the 
 
 relative position of adjacent organs and vessels.) [Posterior view.] 
 A, i2th dorsal vertebra; B, diaphragm; C, receptaculum chyli; D, small intestines. 
 
 fear or undue p.nxiety, increases the blood-pressure, drives more blood 
 to the kidneys, and causes a larger flow of watery secretion. When 
 the atmosphere is hot, there is a relaxation of the vessels of the skin, 
 
THE SKIN AND THE KIDNEYS. 26 1 
 
 with a more than ordinary flow of blood, which is thus withdrawn 
 from the deeper organs. The blood-pressure in the kidneys is not 
 only diminished, but the total quantity passing through them in a 
 given time is much lessened. As a result, the secretion of the kid- 
 neys is scanty, but it contains an unusual percentage of solids. 
 
 When the atmosphere is cold, the reverse is true. The cutaneous 
 vessels contract, the blood is driven to the deeper organs with increased 
 pressure, and there is a less amount of sweat, but an increased renal 
 secretion, containing a smaller proportion of solids. Certain d~ugs have 
 the power of increasing or diminishing the renal secretion. As the 
 waste matters eliminated by the kidneys are being constantly produced 
 in the tissues, the action of the renal organs is continuous, in marked 
 contrast with the intermittent flow of most of the secretions proper, as 
 distinguished from the excretions. 
 
 258. Effects of Alcoholic Drinks upon the Kidneys. The 
 
 kidneys differ from some of the other organs in this : those 
 ean rest a while without any harm to themselves, or to the 
 body. We can keep the eyes closed for a few days, if neces- 
 sary, without injury, and in fact often with benefit ; or, we can 
 abstain from food for some days, if need be, and let the stomach 
 rest. But the kidneys cannot, with safety, cease their work. 
 Their duty in ridding the blood of waste products, and of any 
 foreign or poisonous material introduced, must be done not 
 only faithfully, but continually, or the whole body at once suffers 
 from the evil effects of the retained waste matters. 
 
 This vital fact is the key to the injurious results developed 
 in the kidneys by the use of alcoholic drinks. These two 
 organs have large blood-vessels conveying full amounts of 
 blood to and from their structures, and they feel very quickly 
 the presence of alcohol. Alcoholic liquors excite and irritate 
 the delicate renal membranes, and speedily disturb and event- 
 ually destroy their capacity to excrete the proper materials 
 from the blood. 
 
 The continued congestion of the minute structure of the 
 
262 PRACTICAL PHYSIOLOGY. 
 
 kidney cuts off the needed nutrition of the organ, and forms 
 the primary step in the series of disasters. Sometimes from 
 this continued irritation, with the resulting inflammation, and 
 sometimes from change of structure of the kidney by fatty 
 degeneration, comes the failure to perform its proper function. 
 Then, with this two-edged sword of disaster, the urea, which 
 becomes a poisonous element, and should be removed, is re- 
 tained in the system, while the albumen, which is essential to 
 healthy blood, is filtered away through the diseased kidney. 
 
 259. Alcoholic Liquors as a Cause of Bright's Disease. 
 The unfortunate presence of albumen in the urine is often a 
 symptom of that insidious and fatal malady known as albumi- 
 nuria or Bright's disease, often accompanied with dropsy and 
 convulsions. One of the most constant causes of this disease 
 is the use of intoxicants. It is not at all necessary to this fatal 
 result that a person be a heavy drinker. Steady, moderate 
 drinking will often accomplish the work. Kidney diseases 
 produced by alcoholic drinks, are less responsive to medical 
 treatment and more fatal than those arising from any other 
 known cause. 1 
 
 Experiment 129. Obtain a sheep's kidney in good order. Observe that 
 its shape is something like that of a bean, and note that the concave part 
 (hilus), when in its normal position, is turned towards the backbone. Notice 
 that all the vessels leave and enter the kidney at the hilus. Observe a 
 small thick-walled vessel with open mouth from w r hich may be pressed a 
 few drops of blood. This is the renal artery. Pass a bristle down it. 
 With the forceps, or even with a penknife, lift from the kidney the fine 
 membrane enclosing it. This is the kidney capsule. 
 
 Divide the kidney in halves by a section from its outer to near its inner 
 border. Do not cut directly through the hilus. Note on the cut surfaces, 
 on the outer side, the darker cortical portion, and on the inner side, the 
 smooth, pale, medullary portion. Note also the pyramids of Malpighi. 
 
 1 " The relation to Bright's Disease is not so clearly made out as is assumed by 
 some writers, though I must confess to myself sharing the popular belief that alcohol 
 is one among its most important factors." ROBERT T. EDES, M.D, 
 
CHAPTER X. 
 THE NERVOUS SYSTEM. 
 
 260. General View of the Nervous System. Thus far we 
 have learned something of the various organs and the manner 
 in which they do their work. Regarding our bodily structure 
 as a kind of living machine, we have studied its various parts, 
 and found that each is designed to perform some special work 
 essential to the well-being of the whole. As yet we have 
 learned of no means by which these organs are enabled to adjust 
 their activities to the needs of other tissues and other organs. 
 We are now prepared to study a higher, a more wonderful and 
 complex agency, the nervous system, the master tissue, 
 which controls, regulates, and directs every other tissue of the 
 human body. 
 
 The nervous system, in its properties and mode of action, 
 is distinct from all the other systems and organs, and it shares 
 with no other organ or tissue the power to do its special work. 
 It is the medium through which all impressions are received. 
 It connects all the parts of the body into an organism in which 
 each acts in harmony with every other part for the good of the 
 whole. It animates and governs all movements, voluntary or 
 involuntary, secretion, excretion, nutrition ; in fact all the 
 processes of organic life are subject to its regulating power. 
 The different organs of the body are united by a common 
 sympathy which regulates their action : this harmonious result 
 is secured by means of the nervous system. 
 
 This system, in certain of its parts, receives impressions, and 
 generates a force peculiar to itself. We shall learn that there 
 can be no physical communication between or coordination of 
 
264 PRACTICAL PHYSIOLOGY. 
 
 the various parts of organs, or harmonious acts for a desired 
 result, without the nerves. General impressions, as in ordinary 
 sensation, or special impressions, as in sight, smell, taste, or 
 hearing, every instinct, every act of the will, and every thought 
 are possible only through the action of the nerve centers. 
 
 261. Nerve Cells. However complicated the structure of 
 nerve tissue in man seems to be, it is found to consist of only 
 two different elements, nerve cells and nerve fibers. These 
 are associated and combined in many ways. They 
 are arranged in distinct masses called nerve cen- 
 ters, or in the form of cords known as nerves. 
 The former are made up of nerve fibers ; the latter 
 of both cells and fibers. 
 
 Nerve cells, which may be regarded as the cen- 
 tral organs of the nerve fibers, consist of masses of 
 cell protoplasm, with a large nucleus and nudeolus. 
 F They bear a general resemblance to other cells, but 
 
 Nerve Cells varv rnuch in size and shape. Nerve cells grow, 
 from the become active, and die, as do other cells. A num- 
 ' ber of processes branch off from them, some cells 
 giving one or two, others many. The various kinds of nerve 
 cells differ much in the shape and number of processes. One 
 of the processes is a strand which becomes continuous with the 
 axis cylinder of the nerve fibers ; that is, the axis cylinders of 
 all nerve fibers are joined in one place or another with at least 
 one cell. 
 
 Each part of this system has its own characteristic cell. 
 Thus we have in the spinal cord the large, irregular cells with 
 many processes, and in the brain proper the three-sided cells 
 with a process jutting out from each corner. So characteristic 
 are these forms of cells, that any particular part of nerve struc- 
 ture may be identified by the kind of cells seen under the 
 microscope. Nerve cells and nerve fibers are often arranged in 
 
THE NERVOUS SYSTEM. 265 
 
 groups, the various cells of the groups communicating with one 
 another. This clustered arrangement is called a nerve center. 
 
 262. Nerve Fibers. The nerve fibers, the essential ele- 
 ments of the nerves, somewhat resemble tubes filled with a 
 clear, jelly-like substance. They consist of a rod, or central 
 core, continuous throughout the whole length of the nerve, 
 called the axis cylinder. This core is surrounded by the 
 white substance of Schwann, or 
 medullary sheath, which gives 
 the nerve its characteristic ivory- 
 white appearance. The whole 
 is enclosed in a thin, delicate 
 sheath, known as neurilemma. 
 
 The axis cylinder generally 
 passes without any break from 
 the nerve centers to the end of FlG " ' Nerve Cells from the Gray 
 
 Matter of the Brain. 
 
 the fibers. 1 The outer sheath 
 
 (neurilemma) is also continuous throughout the length of the 
 fibers. The medullary sheath, on the other hand, is broken 
 at intervals of about ^ of an inch, and at the same intervals 
 nuclei are found along the fiber, around each of which is a 
 minute protoplasmic mass. Between each pair of nuclei the 
 sheath is interrupted. This point is known as the node of 
 Ranvier. 
 
 Some nerve fibers have no inner sheath (medullary), the 
 outer alone protecting the axis cylinder. These are known as 
 the non-medullary fibers. They are gray, while the ordinary 
 medullary fibers are white in appearance. The white nerve fi- 
 bers form the white part of the brain and of the spinal cord, and 
 the greater part of the cerebro-spinal nerves. The gray fibers 
 
 1 Thus the fibers which pass out from the sacral plexus in the loins, and extend by 
 means of the great sciatic nerve and its branches to the ends of the toes, may be 
 more than a yard long. 
 
266 
 
 PRACTICAL PHYSIOLOGY. 
 
 occur chiefly in branches from the sympathetic ganglia, though 
 found to some extent in the nerves of the cerebro-spinal system. 
 In a general way, the nerve fibers resemble an electric cable 
 wire with its central rod of copper, and its outer non-conduct- 
 ing layer of silk or gutta-percha. Like the copper rod, the 
 axis cylinder along which the nerve im- 
 pulse travels is the essential part of a 
 nerve fiber. In a cut nerve this cylinder 
 projects like the wick of a candle. It is 
 really the continuation of a process of 
 a nerve cell. Thus the nerve cells and 
 nerve fibers are related, in that the proc- 
 ess of one is the axis cylinder and 
 essential part of the other. 
 
 It'-.^l The separate microscopic threads or 
 
 Jll fibers, bound together in cords of vari- 
 1 I able size, form the nerves. Each strand 
 
 llfjjll I IS] or cord is surrounded and protected by 
 
 its own sheath of connective tissue, made 
 up of nerves. According to its size a 
 nerve may have one or many of these 
 strands. The whole nerve, not unlike a 
 minute tendon in appearance, is covered 
 by a dense sheath of fibrous tissue, in 
 which the blood-vessels and lymphatics 
 are distributed to the nerve fibers. 
 
 FIG. ii2. Medullated 
 Nerve Fibers. 
 
 A, a medullated nerve fiber, 
 showing the subdivision of 
 the medullary sheath into 
 cylindrical sections imbri- 
 cated with their ends ; a 
 nerve corpuscle with an 
 oval nucleus is seen be- 
 tween the neurilemma and 
 the medullary sheath. B, a 
 medullated nerve fiber at 
 a node or constriction of 
 Ranvier; the axis cylinder 
 passes uninterruptedly from 
 one segment into the other, 
 but the medullary sheath is 
 interrupted. 
 
 263. The Functions of the Nerve 
 Cells and Nerve Fibers. The nerve 
 cells are a highly active mass of living 
 material. They find their nourishment 
 in the blood, which is supplied to them 
 in abundance. The blood not only serves as nourishment, but 
 also supplies new material, as it were, for the cells to work 
 
THE NERVOUS SYSTEM. 
 
 267 
 
 over for their own force or energy. Thus we may think of the 
 nerve cells as a sort of a miniature manufactory, deriving their 
 material from the blood, and developing from it nervous energy. 
 
 The nerve fibers, on the other hand, are 
 conductors of nervous energy. They fur- 
 nish a pathway along which the nerve 
 energy generated by the cells may travel. 
 Made up as they are of living nerve sub- 
 stance, the fibers can also generate energy, 
 yet it is their special function to conduct 
 influences to and from the cells. 
 
 264. The Nervous System Compared to a 
 Telegraphic System. In men and other highly 
 organized animals, nerves are found in nearly 
 every tissue and organ of the body. They 
 penetrate the most minute muscular fibers ; 
 
 FIG. 1 13 . Non- Medul- 
 
 lated Fibers. 
 , j . , , c Two nerve fibers, showing 
 
 glands, and are found in the coats of even the nodes or constrictions 
 
 they are closely connected with the cells of the 
 
 of Ranvier and the axis 
 cylinder. The medullary 
 sheath has been dissolved 
 away. The deeply stained 
 oblong nuclei indicate the 
 nerve corpuscles within 
 the neurilemma. 
 
 the smallest blood-vessels. They are among 
 
 the chief factors of the structure of the sense 
 
 organs, and ramify through the skin. Thus 
 
 the nervous system is the system of organs 
 
 through the functions of which we are brought 
 
 into relation with the world around us. When 
 
 we hear, our ears are bringing us into relation with the outer world. 
 
 So sight opens up to us another gateway of knowledge. 
 
 It will help us the better to understand the complicated functions 
 of the nervous system, if we compare' it to a telegraph line. The 
 brain is the main office, and the multitudes of nerve fibers branching 
 off to all parts of the body are the wires. By means of these, nerve 
 messages are constantly being sent to the brain to inform it of what 
 is going on in various parts of the body, and asking what is to be 
 done in each case. The brain, on receiving the intelligence, at once 
 sends back the required instructions. Countless messages are sent 
 to and fro with unerring accuracy and marvelous rapidity. 
 
268 PRACTICAL PHYSIOLOGY. 
 
 Thus, when we accidentally pick up something hot, it is instantly 
 dropped. A nerve impulse passes from the nerves of touch in the 
 fingers to the brain, which at once hurries off its order along another 
 set of nerves for the hand to drop the burning object. These exam- 
 ples, so common in daily life, may be multiplied to any extent. 
 Almost every voluntary act we perform is executed under the direc- 
 tion of the nervous system, although the time occupied is so small 
 that it is beyond our power to estimate it. The very frequency with 
 which the nerves act tends to make us forget their beneficent work. 
 
 265. Divisions of the Nervous System. This system in 
 man consists of two great divisions. The first is the great 
 nerve center of the body, the cerebro-spinal system, which 
 rules the organs of animal life. This includes the brain, 
 the spinal cord, and the cerebro-spinal nerves. Nerves are 
 given off from the brain and the cord, and form the mediums 
 of communication between the external parts of the body, the 
 muscles or the sense organs, and the brain. 
 
 The second part is the sympathetic system, which regulates 
 the organic life. This consists of numerous small nerve cen- 
 ters arranged in oval masses varying greatly in size, called 
 ganglia or knots. These are either scattered irregularly through 
 the body, or arranged in a double chain of knots lying on the 
 front of the spine, within the chest and abdomen. From this 
 chain large numbers of nerves are given off, which end chiefly 
 in the organs of digestion, circulation, and respiration. The 
 sympathetic system serves to bring all portions of the animal 
 economy into direct sympathy with one another. 
 
 266. The Brain as a Whole. The brain is the seat of the 
 intellect, the will, the affections, the emotions, the memory, and 
 sensation. It has also many other and complex functions. In 
 it are established many reflex, automatic, and coordinating cen- 
 ters, which are as independent of consciousness as are those 
 of the spinal cord. 
 
THE NERVOUS SYSTEM. 269 
 
 The brain is the largest and most complex mass of nerve 
 tissue in the body, made up of an enormous collection of gray 
 cells and nerve fibers. This organ consists of a vast number 
 of distinct ganglia, or separate masses of nerve matter, each 
 
 FIG. 114. The Upper Surface of the Cerebrum. (Showing its division 
 into two hemispheres, and also the convolutions.) 
 
 capable of performing separate functions, but united through 
 the cerebral action into a harmonious whole. 
 
 The average weight of the adult human brain is about 50 
 ounces for men and 45 ounces for women. Other things being 
 equal, the size and weight of the brain bear a general relation 
 to the mental power of the individual. As a rule, a large, 
 healthy brain stands for a vigorous and superior intellect. 
 The brains of many eminent men have been found to be 8 to 
 12 ounces above the average weight, but there are notable 
 
27O PRACTICAL PHYSIOLOGY. 
 
 exceptions. The brains of idiots are small ; indeed, any 
 weight under a certain size, about 30 ounces, seems to be 
 invariably associated with an imbecile mind. 
 
 The human brain is absolutely heavier than that of any other 
 animal, except the whale and elephant. Comparing the size 
 of these animals with that of man, it is instructive to notice 
 how much larger in proportion to the body is man's brain. 
 The average proportion of the weight of the brain to the weight 
 of the body is greater in man than in most animals, being 
 about i to 36. In some small birds, in the smaller monkeys, 
 and in some rodents, the proportional weight of the brain to 
 that of the body is even greater than in man. 
 
 267. The Cerebrum. The three principal masses which 
 make up the brain when viewed as a whole are : 
 
 1 . The cerebrum, or brain proper. 
 
 2. The cerebellum, or lesser brain. 
 
 3. The medulla oblongata. 
 
 The cerebrum comprises nearly seven-eighths of the entire 
 mass, and fills the upper part of the skull. It consists of two 
 halves, the right and left cerebral hemispheres. These are 
 almost separated from each other by a deep median fissure. 
 The hemispheres are united at the bottom of the fissure by a 
 mass of white fibers passing from side to side. Each of these 
 hemispheres is subdivided into three lobes, so that the entire 
 cerebrum is made up of six distinct lobes. 
 
 The cerebrum has a peculiar convoluted appearance, its 
 deep folds being separated by fissures, some of them nearly an 
 inch in depth. 
 
 It is composed of both white and gray matter. The former 
 comprises the greater part of the mass, while the . latter is 
 spread over the surface in a layer of about | of an inch 
 thick. The gray matter is the portion having the highest 
 
THE NERVOUS SYSTEM. 27! 
 
 functions, and its apparent quantity is largely increased by 
 being formed in convolutions. 
 
 The convolutions of the cerebrum are without doubt associ- 
 ated with all those higher actions which distinguish man's life; 
 but all the convolutions are not of equal importance. Thus it 
 is probable that only the frontal part of the brain is the intel- 
 lectual region, while certain convolutions are devoted to the 
 service of the senses. 
 
 The cerebrum is the chief seat of the sensations, the intel- 
 lect, the will, and the emotions. A study of cerebral injuries 
 and diseases, and experiments upon the lower animals, prove 
 that the hemispheres, and more especially the gray matter, are 
 connected with mental states. The convolutions in the human 
 brain are more prominent than in that of the higher animals, 
 most nearly allied to man, although some species of animals, 
 not especially intelligent, have marked cerebral convolutions. 
 The higher races of men have more marked convolutions than 
 those less civilized. 
 
 A view of the under surface of the brain, which rests on the 
 floor of the skull, shows the origin of important nerves, called 
 the cranial nerves, the cerebellum, the structure connecting 
 the Optic nerves (optic commissure), the bridge of nervous 
 matter (pons Varolii) connecting the two hemispheres of the 
 cerebellum, and lastly numerous and well-marked convolutions. 
 
 268. The Cerebellum. The cerebellum, or lesser brain, 
 lies in the back of the cranium, and is covered over in man by 
 the posterior lobe of the cerebrum. It is, at it were, astride of 
 the back of the cerebro-spinal axis, and consists of two hemi- 
 spheres joined by a central mass. On its under surface is a 
 depression which receives the medulla oblongata. The cere- 
 bellum is separated from the cerebrum by a horizontal partition 
 of membrane, a portion of the dura mater. In some animals, 
 as in the cat, this partition is partly bone. 
 
2/2 
 
 PRACTICAL PHYSIOLOGY. 
 
 The cerebellum is connected with other parts of the nervous 
 system by strands of white matter on each side, radiating from 
 the center and divided into numerous branches. Around these 
 branches the gray matter is arranged in a beautiful manner, 
 suggesting the leaves of a tree : hence its name, arbor vitae, 
 or the tree of life. 
 
 The functions of the cerebellum are not certainly known. 
 It appears to influence the muscles of the body so as to regu- 
 
 FIG. 115. A Vertical Section of the Brain. 
 
 A, frontal lobe of the cerebrum ; B, parietal lobe ; C, parieto-occipital lobe with fissure 
 between this lobe and D, the occipital lobe; E, cerebellum ; F, arbor vitae ; H, 
 pons Varolii ; K, medulla oblongata ; L, portion of lobe on the opposite side of 
 brain. The white curved band above H represents the corpus callosum. 
 
 late their movements ; that is, it serves to bring the various 
 muscular movements into harmonious action. The mechanism 
 by which it does this has not yet been clearly explained. In 
 an animal from which the cerebellum has been removed, the 
 functions of life do not appear to be destroyed, but all power 
 of either walking or flying straight is lost. 
 
THE NERVOUS SYSTEM. 2/3 
 
 Disease or injury of the cerebellum usually produces blind- 
 ness, giddiness, a tendency to move backwards, a staggering, 
 irregular gait, and a feeling of insecurity in maintaining various 
 positions. There is no loss of consciousness, or other disturb- 
 ance of the mental functions. 
 
 269. The Membranes of the Brain. The brain and spinal 
 cord are protected by three important membranes, known as 
 the meninges, the dura mater, the arachnoid, and the pia 
 mater. 
 
 The outer membrane, the dura mater, is much thicker and 
 stronger than the others, and is composed of white fibrous and 
 elastic connective tissue. It closely lines the inner surface of 
 the skull, and forms a protective covering for the brain. Folds 
 of it pass between the several divisions of the brain and serve 
 to protect them. 
 
 The arachnoid is a thin membrane which lies beneath the 
 dura mater. It secretes a serous fluid which keeps the inner 
 surfaces moist. 
 
 The pia mater is a very delicate, vascular membrane which 
 covers the convolutions, dips into all the fissures, and even 
 penetrates into the interior of the brain. It is crowded with 
 blood-vessels, which divide and subdivide very minutely before 
 they penetrate the brain. The membranes of the brain are 
 sometimes the seat of inflammation, a serious and painful dis- 
 ease, commonly known as brain fever. 
 
 270. The Medulla Oblongata. This is the thick upper part 
 of the spinal cord, lying within the cavity of the skull. It is 
 immediately under the cerebellum, and forms the connecting 
 link between the brain and the spinal cord. It is about an 
 inch and a quarter long, and from one-half to three-fourths of 
 an inch wide at its upper part. The medulla oblongata con- 
 sists, like the spinal cord, of columns of white fibers and 
 
2/4 PRACTICAL PHYSIOLOGY. 
 
 masses of gray matter, but differently arranged. The gray 
 matter is broken up into masses which serve as centers of 
 
 origin for various nerves. 
 
 The functions of the me- 
 dulla oblongata are closely 
 connected with the vital proc- 
 esses. It is a great nerve 
 tract for transmitting sensory 
 and motor impressions, and 
 also the seat of a number 
 of centers for reflex actions 
 of the highest importance to 
 life. Through the posterior 
 part of the medulla the sen- 
 sory impressions pass, that 
 is, impressions from below 
 upwards to the brain result- 
 ing in sensation or feeling. 
 In the anterior part of the 
 medulla, pass the nerves for 
 motor transmission, that is, 
 nerve influences from above 
 downwards that shall result 
 in muscular contractions in 
 some part of the body. 
 
 FIG. 1 16. Illustrating the General Arrange- The medulla is also the 
 ment of the Nervous System. (Posterior sea t o f a number of reflex 
 
 centers connected with the 
 
 influence of the nervous system on the blood-vessels, the move- 
 ments of the heart, of respiration, and of swallowing, and on the 
 secretion of saliva. This spot has been called the "vital knot." 
 In the medulla also are centers for coughing, vomiting, swal- 
 lowing, and the dilatation of the pupil of the eye. It is also in 
 part the deep origin of many of the important cranial nerves. 
 
THE NERVOUS SYSTEM. 2/5 
 
 271. The Cranial Nerves. The cranial or cerebral nerves 
 
 consist of twelve pairs of nerves which pass from the brain 
 through different openings in the base of the skull, and are 
 distributed over the head and face, also to some parts of the 
 trunk and certain internal organs. These nerves proceed in 
 pairs from the corresponding parts of each side of the brain, 
 chiefly to the organs of smell, taste, hearing, and sight. 
 
 The cranial nerves are of three kinds : sensory, motor, and 
 both combined, viz., mixed. 
 
 Distribution and Functions of the Cranial Nerves. The cranial 
 nerves are thus arranged in pairs : 
 
 The first pair are the olfactory nerves, which pass down through 
 the ethmoid bone into the nasal cavities, and are spread over the inner 
 surface of the nose. They are sensory, and are the special nerves 
 of smell. 
 
 The second pair are the optic nerves, which, under the name of 
 the optic tracts, run down to the base of the brain, from which an 
 optic nerve passes to each eyeball. These are sensory nerves, and 
 are devoted to sight. 
 
 The third, fourth, and sixth pairs proceed to the muscles of the 
 eyes and control their movements. These are motor nerves, the 
 movers of the eye. 
 
 Each of the fifth pair of nerves is in three branches, and proceeds 
 mainly to the face. They are called tri-facial, and are mixed nerves, 
 partly sensory and partly motor. The first branch is purely sensory, 
 and gives sensibility to the eyeball. The second gives sensibility to 
 the nose, gums, and cheeks. The third (mixed) gives the special 
 sensation of taste on the front part of the tongue, and ordinary sen- 
 sation on the inner side of the cheek, on the teeth, and also on the 
 scalp in front of the ear. The motor branches supply the chewing 
 muscles. 
 
 The seventh pair, the facial, proceed to the face, where they 
 spread over the facial muscles and control their movements. The 
 eighth pair are the auditory, or nerves of hearing, and are distributed 
 to the special organs of hearing. 
 
PRACTICAL PHYSIOLOGY. 
 
 The next three pairs of nerves all arise from the medulla, and 
 escape from the cavity of the skull through the same foramen. They 
 are sometimes described as one pair, namely, the eighth, but it is 
 more convenient to consider them separately. 
 
 The ninth pair, the glosso-pharyngeal, are partly sensory and partly 
 motor. Each nerve contains two roots : 
 one a nerve of taste, which spreads over 
 the back part of the tongue ; the other a 
 motor nerve, which controls the muscles 
 engaged in swallowing. 
 
 The tenth pair, the pneumogastric, also 
 known as the vagus or wandering nerves, 
 are the longest and most complex of all the 
 cranial nerves. They are both motor and 
 sensory, and are some of the most impor- 
 tant nerves in the body. Passing from the 
 medulla they descend near the oesophagus 
 to the stomach, sending off, on their way, 
 branches to the throat, the larynx, the lungs, 
 and the heart. Some of their branches 
 restrain the movements of the heart, others 
 convey impressions to the brain, which 
 result in quickening or slowing the move- 
 ments of breathing. Other branches pass 
 to the stomac h, and convey to the brain 
 -Passions which inform us of the con- 
 munis; D, fifth nerve; E, motor dition of that organ. These are the nerves 
 
 E s^Wszi ^. which we ex p erience the feelings o 
 
 pharyngeal nerve; K, pneumo- pain in the stomach, hunger, nausea, and 
 r^'v^; a ; X other vague impressions which we 
 extremity of spinal cord; o, often associate with that organ. 
 
 decussation of the anterior pyra- ,, , , , . , . , 
 
 mids ; R, anterior pyramids of The eleventh pair, the spinal accessory. 
 the medulla oblongata ; s, pons a re strictly motor, and supply the muscles 
 
 of the neck and the back. 
 
 The twelfth pair, the hypoglossal, are also motor, pass to the 
 muscles of the tongue, and help control the delicate movements in 
 the act of speech. 
 
 FIG. 117. Anterior View of 
 the Medulla Oblongata. 
 
THE NERVOUS SYSTEM. 
 
 272. The Spinal Cord. This is a long, rod-like mass of 
 white nerve fibers, surrounding a central mass of gray matter. 
 It is a continuation of the medulla oblongata, and is lodged 
 in the canal of the spinal column. It extends from the base 
 of the skull to the lower border of the first lumbar vertebra, 
 where it narrows off to a slender filament of gray substance. 
 
 The spinal cord is from 16 to 18 inches long, and has about 
 che thickness of one's little finger, weighing about i^ ounces. 
 Like the brain, it is enclosed in three membranes, which in 
 fact are the continuation of those within the skull. They 
 protect the delicate cord, and convey vessels for its nourish- 
 ment. The space between the two inner membranes contains 
 a small quantity of fluid, supporting the cord, as it were in a 
 water-bath. It is thus guarded against shocks. 
 
 The cord is suspended and kept in position in the canal by 
 delicate ligaments at regular intervals between the inner and 
 outer membranes. Finally, between the canal, enclosed by its 
 three membranes, and the bony walls of the spinal canal, 
 there is considerable fatty tissue, a sort of packing material, 
 imbedded in which are some large blood-vessels. 
 
 273. Structure of the Spinal Cord. The arrangement of 
 the parts of the spinal cord is best understood by a transverse 
 section. Two fissures,, one behind, the other in front, pene- 
 trate deeply into the cord, very nearly dividing it into lateral 
 halves. In the middle of the isthmus which joins the two 
 halves, is a very minute opening, the central canal of the cord. 
 This tiny channel, just visible to the naked eye, is connected 
 with one of the openings of the medulla oblongata, and extends, 
 as do the anterior and posterior fissures, the entire length of 
 the cord. 
 
 The spinal cord, like the brain, consists of gray and white 
 matter, but the arrangement differs. In the brain the white 
 matter is within, and the gray matter is on the surface. In 
 
278 PRACTICAL PHYSIOLOGY. 
 
 the cord the gray matter is arranged in two half-moon-shaped 
 masses, the backs ' of which are connected at the central part. 
 The white matter, consisting mainly of fibers, running for the 
 most part in the direction of the length of the cord, is outside 
 of and surrounds the gray crescents. Thus each half or side 
 of the cord has its own gray crescent, the horns of which point 
 one forwards and the other backwards, called respectively the 
 anterior and posterior cornua or horns. 
 
 It will also be seen that the white substance itself, in each 
 half of the cord, is divided by the horns of the gray matter 
 and by fibers passing from them into three parts, which are 
 known as the anterior, posterior, and lateral columns. 
 
 Experiment 130. Procure at the market an uninjured piece of the spinal 
 cord from the loin of mutton or the sirloin or the rib of beef. After noting 
 its general character while fresh, put it to soak in dilute alcohol, until it is 
 sufficiently hard to be cut in sections. 
 
 274. The Spinal Nerves. From the gray matter on each 
 side of the spinal cord 31 spinal nerves are given off and dis- 
 tributed chiefly to the muscles and the skin. They pass out 
 at regular intervals on each side of the canal, by small open- 
 ings between the vertebrae. Having escaped from the spine, 
 they pass backwards and forwards, ramifying in the soft parts 
 of the body. The first pair pass out between the skull and 
 the atlas, the next between the atlas and the axis, and so on 
 down the canal. The eighth pair, called cervical, pass out in 
 the region of the neck ; twelve, called dorsal, in the region of 
 the ribs ; five are lumbar, and five sacral, while the last pair 
 leave the cord near the coccyx. 
 
 Each spinal nerve has two roots, one from the anterior, the 
 other from the posterior portion of the cord. These unite and 
 run side by side, forming as they pass between the vertebra 
 one silvery thread, or nerve trunk. Although bound up in one 
 bundle, the nerve fibers of the two roots remain quite distinct, 
 and perform two entirely different functions. 
 
THE NERVOUS SYSTEM. 
 
 279 
 
 C-r 
 
 After leaving the spinal cord, each nerve divides again and 
 again into finer and finer threads. These minute branches are 
 distributed through the muscles, and terminate on the surface 
 of the body. The anterior roots become motor nerves, their 
 branches being distributed to cer- 
 tain muscles of the body, to control 
 their movements. The posterior roots 
 develop into sensory nerves, their 
 branches being distributed through 
 the skin and over the surface of the 
 body to become nerves of touch. In 
 brief, the spinal nerves divide and 
 subdivide, to reach with their twigs 
 all parts of the body, and provide 
 every tissue with a nerve center, a 
 station from which messages may be 
 sent to the brain. 
 
 A, anterior median fissure ; B, pos- 
 
 275. The Functions Of the Spinal tenor median fissure; C, anterior 
 
 Nerves. The messages which pass 
 
 along the spinal nerves to and from 
 
 the brain are transmitted mostly 
 
 through the gray matter of the cord, 
 
 but some pass along the white matter 
 
 on the outer part. As in the brain, however, all the active 
 
 powers of the cord are confined to the gray matter. The 
 
 spinal nerves themselves have nothing to do with sensation or 
 
 will. They are merely conductors to carry messages to and 
 
 fro. They neither issue commands nor feel a sensation. 
 
 Hence, they consist entirely of white matter. 
 
 276. Functions of the Spinal Cord. The spinal cord is 
 the principal channel through which all impulses from the 
 trunk and extremities pass to the brain, and all impulses to 
 the trunk and extremities pass from the brain. That is, the 
 
 FIG. 118. Side View of the 
 Spinal Cord. (Showing the 
 fissures and columns.) 
 
 lateral fissure ; D, posterior lateral 
 fissure ; E, lateral column ; F, an- 
 terior column; G, posterior col- 
 umn ; H, posterior median col- 
 umn; K, anterior root ; L, posterior 
 root; M, ganglion of N, a spinal 
 nerve. 
 
28O PRACTICAL PHYSIOLOGY. 
 
 spinal cord receives from various parts of the body by means 
 of its sensory nerves certain impressions, and conveys them 
 to the brain, where they are interpreted. 
 
 The cord also transmits by means of its motor nerves the 
 commands of the brain to the voluntary muscles, and so causes 
 movement. Thus, when the cord is divided at any point, com- 
 pressed, as by a tumor or broken bone, or disorganized by dis- 
 ease, the result is a complete loss of sensation and voluntary 
 movement below the point of injury. If by accident a man 
 has his spinal cord injured at some point, he finds he has lost 
 all sensation and power of motion below that spot. The im- 
 pulse to movement started in his brain by the will does not 
 reach the muscles he wishes to move, because traveling down 
 the spinal cord, it cannot pass the seat of injury. 
 
 So the impression produced by pricking the leg with a pin, 
 which, before pain can be felt, must travel up the spinal cord 
 to the brain, cannot reach the brain because the injury obstructs 
 the path. The telegraph wire has been cut, and the current 
 can no longer pass. 
 
 277. The Spinal Cord as a Conductor of Impulses. The 
 
 identity in structure of the spinal nerves, whether motor or 
 sensory, and the vast number of nerves in the cord make it 
 impossible to trace for any distance with the eye, even aided 
 by the microscope and the most skillful dissection, the course 
 of nerve fibers. The paths by which the motor impulses travel 
 down the cord are fairly well known. These impulses origi- 
 nate in the brain, and passing down keep to the same side 
 of the cord, and go out by nerves to the same side of the 
 body. 
 
 The sensory impulses, however, soon after they enter the 
 cord by the nerve of one side, cross in the cord to the opposite 
 side, up which they travel to the brain. Thus the destruction 
 of one lateral half of the cord causes paralysis of motion on 
 
THE NERVOUS SYSTEM. 
 
 281 
 
 the same side as the injury, but loss of sensation on the oppo- 
 site side, because the posterior portion destroyed consists of 
 fibers which have crossed from the opposite side. 
 
 Experiment proves that if both roots of a spinal nerve be 
 cut, all those parts 
 of the body to 
 which they send 
 branches become 
 paralyzed, and 
 ha ve neither 
 sense of pain nor 
 power of volun- 
 tary movement. 
 The parts might 
 even be cut or 
 burned without 
 pain. It is pre- 
 cisely like cutting 
 a telegraph wire 
 and stopping the 
 current. 
 
 Experi men t 
 also proves that 
 
 FIG. 119. The Base of the Brain. 
 
 A, anterior lobe of the cerebrum ; B, olfactory nerve ; C, sphen- 
 oid portion of the posterior lobe ; D, optic chiasm ; E, optic 
 tract; F, abducens; H, M, hemispheres of the cerebellum; 
 K, occipital portion of the occipital lobe ; L, fissure separat- 
 ing the hemispheres ; N, medulla oblongata ; O, olivary body ; 
 P, anterior pyramids; R, pons Valorii ; S, section of olfactory 
 
 if only the pos- 
 terior root of a 
 spinal nerve be 
 cut, all sensation 
 is lost in the parts 
 to which the nerve 
 passes, but the 
 power of moving these parts is retained. But if the anterior 
 root alone be divided, all power of motion in the parts supplied 
 by that nerve is lost, but sensation remains. From these and 
 many other experiments, it is evident that those fibers of a 
 
 nerve, with the trunk removed to show sulcus in which it is 
 lodged ; T, anterior extremity of median fissure. 
 
282 PRACTICAL PHYSIOLOGY. 
 
 nerve which are derived from the anterior root are motor, and 
 those from the posterior root sensory, fibers. Impulses sent 
 from the brain and spinal cord to muscles will, therefore, pass 
 along the anterior roots through those fibers of the nerves 
 which are derived from these (motor) roots. On the other 
 hand, impressions or sensations passing to the brain will enter 
 the spinal cord and reach the brain through the posterior or 
 sensory roots. 
 
 278. The Spinal Cord as a Reflex Center. Besides this 
 function of the spinal cord as a great nerve conductor to carry 
 sensations to the brain, and bring back its orders, it is also an 
 independent center for what is called reflex action. By means 
 of its sensory nerves it receives impressions from certain parts 
 of the body, and on its own authority sends back instructions 
 to the muscles by its motor nerves, without consulting the 
 brain. This constitutes reflex action, so called because the 
 impulse sent to the spinal cord by certain sensory nerves is 
 at once reflected or sent back as a motor impulse to the 
 muscles. 
 
 This reflex action is a most important function of the spinal 
 cord. This power is possessed only by the gray matter of the 
 cord, the white substance being simply a conductor. 
 
 The cells of gray matter are found all along the cord, but 
 are grouped together in certain parts, notably in the cervical 
 and lumbar regions. The cells of the anterior horns are in 
 relation with the muscles by means of nerve fibers, and are 
 also brought into connection with the skin and other sensory 
 surfaces, by means of nerve fibers running in the posterior 
 part of the cord. Thus there is established in the spinal cord, 
 without reference to the brain at all, a reflex mechanism. 
 
 279. Reflex Centers. For the purpose of illustration, we 
 might consider the body as made up of so many segments piled 
 
THE NERVOUS SYSTEM. 283 
 
 one on another, each segment presided over by a similar seg- 
 ment of spinal cord. Each bodily segment would have sensory 
 and motor nerves corresponding to its connection with the 
 spinal cord. The group of cells in each spinal segment is 
 intimately connected with the cells of the segments above and 
 below. Thus an impression reaching the cells of one spinal 
 segment might be so strong as to overflow into the cells of 
 other segments, and thus cause other parts of the body to be 
 affected. 
 
 Take as an example the case of a child who has eaten im- 
 proper food, which irritates its bowels. Sensory nerves of the 
 bowels are disturbed, and powerful impressions are carried up 
 to a center in the spinal cord. These impressions may now 
 overflow into other centers, from which spasmodic discharges 
 of nerve energy may be liberated, which passing to the muscles, 
 throw them into violent and spasmodic contraction. In other 
 words, the child has a fit, or convulsion. All this disturbance 
 being the result of reflex action (the spasmodic motions being 
 quite involuntary, as the brain takes no part in them), the child 
 meanwhile is, of course, entirely unconscious and, however it 
 may seem to be distressed, really suffers no pain. 
 
 Scattered along the entire length of the spinal cord, espe- 
 cially in the upper part, are groups of nerve cells which preside 
 over certain specific functions of animal life ; that is, definite 
 collections of cells which control definite functions. Thus 
 there are certain centers for maintaining the action of the 
 heart, and the movements of breathing; and low down in the 
 cord, in the lumbar regions, are centers for the control of 
 the various abdominal organs. 
 
 Numerous other reflex centers are described by physiologists, 
 but enough has been said to emphasize the great importance 
 of the spinal cord as an independent nerve center, besides its 
 function as a conductor of nervous impulses to and from the 
 brain. 
 
284 PRACTICAL PHYSIOLOGY. 
 
 280. The Brain as a Reflex Center. The brain, as we 
 have just stated, is the seat of consciousness and intelligence. 
 It is also the seat of many reflex, automatic, and coordinating 
 centers. These give rise to certain reflex actions which are 
 as entirely independent of consciousness as are those of 
 the spinal cord. These acts take place independently of the 
 will, and often without the consciousness of the individual. 
 Thus, a sudden flash of light causes the eyes to blink, as the 
 result of reflex action. The optic nerves serve as the sensory, 
 and the facial nerves as the motor, conductors. The sudden 
 start of the whole body at some loud noise, the instinctive 
 dodging a threatened blow, and the springing back from sud- 
 den danger, are the results of reflex action. The result ensues 
 in these and in many other instances, without the conscious- 
 ness of the individual, and indeed beyond his power of control. 
 
 281. The Importance of Reflex Action. Reflex action is 
 thus a marvelous provision of nature for our comfort, health, 
 and safety. Its vast influence is not realized, as its number- 
 less acts are so continually going on without our knowledge. 
 In fact, the greater part of nerve power is expended to produce 
 reflex action. The brain is thus relieved of a vast amount of 
 work. It would be impossible for the brain to serve as a 
 " thinking center " to control every act of our daily life. If 
 we had to plan and to will every heart-beat or every respira- 
 tion, the struggle for life would soon be given up. 
 
 The fact that the gray cells of the spinal cord can originate 
 a countless number of reflex and automatic activities is not 
 only of great importance in protecting the body from injury, 
 but increases vastly the range of the activities of our daily life. 
 
 Even walking, riding the bicycle, playing on a piano, and 
 numberless other such acts may be reflex movements. To 
 learn how, requires, of course, the action of the brain, but by 
 frequent repetition the muscles become so accustomed to cer- 
 
THE NERVOUS SYSTEM. 
 
 28 5 
 
 tain successive movements, that they are continued by the cord 
 without the control of the brain. Thus we may acquire a sort 
 of artificial reflex action, which in time becomes in a way a 
 part of our organization, and is carried on without will power 
 or even consciousness. 
 
 So, while the hands are busily doing 
 one thing, the brain can be intently 
 thinking of another. In fact, any at- 
 tempt to control reflex action is more 
 apt to hinder than to help. In coming 
 rapidly down stairs, the descent will be 
 made with ease and safety if the spinal 
 cord is allowed entire charge of the FIG. 120. -Dr. Waller's Dia- 
 act, but the chances of Stumbling or grammatic Illustration of the 
 
 f , . , Reflex Process, 
 
 of tripping are very much increased 
 
 From the sentient surface (1) an 
 
 if each step be taken as the result of affe rent impulse passes along 
 the will power. The reflex action of < 2) to the posterior root of the 
 
 spinal cord, the nerve fibers of 
 
 the cord may be diminished, or in- the posterior root ending in 
 hibited as it is called, but this power minute "laments among the 
 
 . . . , small cells of this part of the 
 
 is limited. Thus, we can by an effort cord (3) . In some unknow n 
 of the will stop breathing for a certain wa ? this impulse passes across 
 
 the gray part of the cord to the 
 
 time, but beyond that the renex mech- 
 
 large cells of the anterior root 
 (5), the cells of this part being 
 connected by their axis-cylinder 
 with the efferent fibers (6). 
 These convey the stimulus to 
 the fibers of the muscle (7), 
 which accordingly contract. 
 Where the brain is concerned 
 in the action the circuit is longer 
 through S and M. 
 
 Experiment 131. To illustrate reflex action by what is called knee-jerk. 
 Sit on a chair, and cross the right leg over the left one. With the tips of 
 the ringers or the back of a book, strike the right ligamentum patellae. 
 The right leg will be raised and thrown forward with a jerk, owing to the 
 contraction of the quadriceps muscles. An appreciable time elapses be- 
 tween the striking of the tendon and the jerk. The presence or absence 
 of the knee-jerk may be a most significant symptom to the physician. 
 
 anism overcomes our will and we could 
 not, if we would, commit suicide by 
 holding our breath. When we are 
 asleep, if the palm of the hand be 
 tickled, it closes ; when we are awake 
 we can prevent it. 
 
286 PRACTICAL PHYSIOLOGY. 
 
 282. The Sympathetic System. Running along each side 
 of the spine, from the base of the skull to the coccyx, is a 
 chain of nerve knots, or ganglia. These ganglia, twenty-four 
 on each side, and their branches form the sympathetic system, 
 as distinguished from the cerebro-spinal system consisting of 
 the brain and spinal cord and the nerves springing from them. 
 The ganglia of the sympathetic system are connected with each 
 other and with the sensory roots of the spinal nerves by a net- 
 work of gray nerve fibers. 
 
 At the upper end the chain of each side passes up into the 
 cranium and is closely connected with the cranial nerves. In 
 the neck, branches pass to the lungs and the heart. From the 
 ganglia in the chest three nerves form a complicated network 
 of fibers, from which branches pass to the stomach, the liver, 
 the intestines, the kidneys, and other abdominal organs. A 
 similar network of fibers is situated lower down in the pelvis, 
 from which branches are distributed to the pelvic organs. At 
 the coccyx the two chains unite into a single ganglion. 
 
 Thus, in general, the sympathetic system, while intimately 
 connected with the cerebro-spinal, forms a close network of 
 nerves which specially accompany the minute blood-vessels, 
 and are distributed to the muscles of the heart, the lungs, the 
 stomach, the liver, the intestines, and the kidneys that is, 
 the hollow organs of the body. 
 
 283. The Functions of the Sympathetic System. This 
 system exercises a superintending influence over the greater 
 part of the internal organs of the body, controlling to a certain 
 extent the functions of digestion, nutrition, circulation, and 
 respiration. The influence thus especially connected with the 
 processes of organic life is generally different from, or even 
 opposed to, that conveyed to the same organs by fibers running 
 in the spinal or cranial nerves. These impulses are beyond 
 the control of the will. 
 
THE NERVOUS SYSTEM. 
 
 28 7 
 
 FIG. 121. The Cervical and Thoracic Portion of the Sympathetic Nerve 
 and its Main Branches. 
 
 A, right pneumogastric ; B, spinal accessory ; C, glosso-pharyngeal ; D, right bronchus ; 
 E, right branch of pulmonary artery; F, one of the intercostal nerves; H, great 
 splanchnic nerve ; K, solar plexus ; L, left pneumogastric ; M, stomach branches of 
 right pneumogastric; N, right ventricle; O, right auricle; P, trunk of pulmonary 
 artery; R, aorta; S, cardiac nerves; T, recurrent laryngeal nerve; U, superior 
 laryngeal nerve ; V, submaxillary ganglion ; W, lingual branch of the sth nerve ; 
 X, ophthalmic ganglion ; Y, motor oculi externus. 
 
288 PRACTICAL PHYSIOLOGY. 
 
 Hence, all these actions of the internal organs just mentioned 
 that are necessary to the maintenance of the animal life, and of 
 the harmony which must exist between them, are controlled by 
 the sympathetic system. But for this control, the heart would 
 stop beating during sleep, digestion would cease, and breathing 
 would be suspended. Gentle irritation of these nerves, in- 
 duced by contact of food in the stomach, causes that organ 
 to begin the churning motion needed for digestion. Various 
 mental emotions also have a reflex action upon the sympathetic 
 system. Thus, terror dilates the pupils, fear acts upon the 
 nerves of the small blood-vessels of the face to produce pallor, 
 and the sight of an accident, or even the emotions produced by 
 hearing of one, may excite nausea and vomiting. 
 
 The control of the blood- vessels, as has been stated (sec. 
 195), is one of the special functions of the sympathetic system. 
 Through the nerves distributed to the muscular coats of the 
 arteries, the caliber of these vessels can be varied, so that at 
 one moment they permit a large quantity of blood to pass, and 
 at another will contract so as to diminish the supply. This, 
 too, is beyond the control of the will, and is brought about by 
 the vaso-motor nerves of the sympathetic system through a re- 
 flex arrangement, the center for which is the medulla oblongata. 
 
 284. Need of Rest. The life of the body, as has been em- 
 phasized in the preceding chapters, is subject to constant waste 
 going on every moment, from the first breath of infancy to the 
 last hour of old age. We should speedily exhaust our life from 
 this continual loss, but for its constant renewal with fresh 
 material. This exhaustion of life is increased by exertion, 
 and the process of repair is vastly promoted by rest. Thus, 
 while exercise is a duty, rest is equally imperative. 
 
 The eye, when exactingly used in fine work, should have 
 frequent intervals of rest in a few moments of darkness by 
 closing the lids. The brain, when urged by strenuous study, 
 
THE NERVOUS SYSTEM. 289 
 
 should have occasional seasons of rest by a dash of cold water 
 upon the forehead, and a brief walk with slow and deep inspi- 
 rations of fresh air. The muscles, long cramped in a painful 
 attitude, should be rested as often as may be, by change of 
 posture or by a few steps around the room. 
 
 It is not entirely the amount of work done, but the continuity 
 of strain that wears upon the body. Even a brief rest inter- 
 rupts this strain ; it unclogs the wheels of action. Our bodies 
 are not designed for continuous toil. An alternation of labor 
 and rest diminishes the waste of life. The benign process of 
 repair cannot go on, to any extent, during strenuous labor, but 
 by interposing frequent though brief periods of rest, we lessen 
 the amount of exhaustion, refresh the jaded nerves, and the 
 remaining labor is more easily endured. 
 
 285. Benefits of Rest. There is too little repose in our 
 American nature and in our modes of life. A sense of fatigue 
 is the mute appeal of the body for a brief respite from labor, 
 and the appeal should, if possible, be heeded. If this appeal 
 be not met, the future exertion exhausts far more than if the 
 body had been even slightly refreshed. If the appeal be met, 
 the brief mid-labor rest eases the friction of toil, and the 
 remaining labor is more easily borne. The feeling that a five- 
 minute rest is so much time lost is quite an error. It is a 
 gain of physical strength, of mental vigor, and of the total 
 amount of work done. 
 
 The merchant burdened with the cares of business life, the 
 soldier on the long march, the ambitious student over-anxious 
 to win success in his studies, the housewife wearied with her 
 many hours of exacting toil, each would make the task 
 lighter, and would get through it with less loss of vital force, 
 by occasionally devoting a few minutes to absolute rest in 
 entire relaxation of the strained muscles and overtaxed 
 nerves. 
 
2QO PRACTICAL PHYSIOLOGY. 
 
 286. The Sabbath as a Day of Physiological Rest. The 
 divine institution of a Sabbath of rest, one day in seven, is 
 based upon the highest needs of our nature. Rest, to be most 
 effective, should alternate in brief periods with labor. 
 
 It is sound physiology, as well as good morals and manners, 
 to cease from the usual routine of six days of mental or physi- 
 cal work, and rest both the mind and the body on the seventh. 
 Those who have succeeded best in what they have undertaken, 
 and who have enjoyed sound health during a long and useful 
 life, have studiously lived up to the mandates of this great 
 physiological law. It is by no means certain that the tendency 
 nowadays to devote the Sabbath to long trips on the bicycle, 
 tiresome excursions by land and sea, and sight-seeing gen- 
 erally, affords that real rest from a physiological point of 
 view which nature demands after six days of well-directed 
 manual or mental labor. 
 
 287. The Significance of Sleep as a Periodical Rest. Of 
 
 the chief characteristics of all living beings none is so signifi- 
 cant as their periodicity. Plants as well as animals exhibit 
 this periodic character. Thus plants have their annual as well 
 as daily periods of activity and inactivity. Hibernating ani- 
 mals pass the winter in a condition of unconsciousness only to 
 have their functions of activity restored in early spring. Human 
 beings also present many instances of a periodic character, 
 many of which have been mentioned in the preceding pages. 
 Thus we have learned that the heart has its regular alternating 
 periods of work and rest. After every expiration from the 
 lungs there is a pause before the next inspiration begins. 
 
 Now sleep is just another manifestation of this periodic and 
 physiological rest by which Nature refreshes us. It is during 
 the periods of sleep that the energy expended in the activities 
 of the waking hours is mainly renewed. In our waking moments 
 the mind is kept incessantly active by the demands made on it 
 
THE NERVOUS SYSTEM. 2QI 
 
 through the senses. There is a never-ceasing expenditure of 
 energy and a consequent waste which must be repaired. A 
 time soon comes when the brain cells fail to respond to the 
 demand, and sleep must supervene. However resolutely we 
 may resist this demand, Nature, in her relentless way, puts us to 
 sleep, no matter what objects are brought before the mind with 
 a view to retain its attention. 1 
 
 288. Effect of Sleep upon the Bodily Functions. In all 
 
 the higher animals, the central nervous system enters once at 
 least in the twenty-four hours into the condition of rest which 
 we call sleep. Inasmuch as the most important modifications 
 of this function are observed in connection with the cerebro- 
 spinal system, a brief consideration of the subject is properly 
 studied in this chapter. In Chapter IV. we learned that repose 
 was as necessary as exercise to maintain muscular vigor. So 
 after prolonged mental exertion, or in fact any effort which 
 involves an expenditure of what is often called nerve-force, 
 sleep becomes a necessity. The need of such a rest is self- 
 evident, and the loss of it is a common cause of the impairment 
 of health. While we are awake and active, the waste of the 
 body exceeds the repair ; but when asleep, the waste is dimin- 
 ished, and the cells are more actively rebuilding the structure 
 for to-morrow's labor. The organic functions, such as are under 
 the direct control of the sympathetic nervous system, circula- 
 tion, respiration, and digestion, are diminished in activity 
 during sleep. The pulsations of the heart and the respiratory 
 
 1 Remarkable instances are cited to illustrate the imperative demand .for sleep. 
 Gunner boys have been known to fall asleep during the height of a naval battle, 
 owing to the fatigue occasioned by the arduous labor in carrying ammunition for 
 the gunner. A case is reported of a captain of a British frigate who fell asleep 
 and remained so for two hours beside one of the largest guns of his vessel, the gun 
 being served vigorously all the time. Whole companies of men have been known to 
 sleep while on the march during an arduous campaign. Cavalrymen and frontiers- 
 men have slept soundly in the saddle during the exhausting campaigns against the 
 Indians. 
 
2Q2 PRACTICAL PHYSIOLOGY. 
 
 movements are less frequent, and the circulation is slower. 
 The bodily temperature is reduced, and the cerebral circulation 
 is diminished. The eyes are turned upward and inward, and 
 the pupils are contracted. 
 
 The senses do not all fall to sleep at once, but drop off suc- 
 cessively : first the sight, then the smell, the taste, the hearing, 
 and lastly the touch. The sleep ended, they awake in an in- 
 verse order, touch, hearing, taste, smell, and sight. 
 
 289. The Amount of Sleep Required. No precise rule can 
 be laid down concerning the amount of sleep required. It 
 varies with age, occupation, temperament, and climate to a 
 certain extent. An infant whose main business it is to grow 
 spends the greater part of its time in sound sleep. Adults 
 of average age who work hard with their hands or brain, 
 under perfectly normal physiological conditions, usually require 
 at least eight hours of sleep. Some need less, but few require 
 more. Personal peculiarities, and perhaps habit to a great 
 extent, exert a marked influence. Some of the greatest men, 
 as Napoleon I., have been very sparing sleepers. Throughout 
 his long and active life, Frederick the Great never slept more 
 than five or six hours in the twenty-four. On the other hand, 
 some of the busiest brain-workers who lived to old age, as 
 William Cullen Bryant and Henry Ward Beecher, required and 
 took care to secure at least eight or nine hours of sound sleep 
 every night. 
 
 In old age, less sleep is usually required than in adult life, 
 while the aged may pass much of their time in sleep. In fact, 
 each person learns by experience how much sleep is necessary. 
 There is no one thing which more unfits one for prolonged 
 mental or physical effort than the loss of natural rest. 
 
 290. Practical Rules about Sleep. Children should not be 
 played with boisterously just before the bedtime hour, nor their 
 
THE NERVOUS SYSTEM. 
 
 293 
 
 minds excited with weird goblin stories, or a long time may pass 
 before the wide-open eyes and agitated nerves become com- 
 posed to slumber. Disturbed or insufficient sleep is a potent 
 factor towards producing a fretful, irritable child. 
 
 At all ages the last hour before sleep should, if possible, be 
 spent quietly, to smooth the way towards sound and refreshing 
 rest. The sleep in- 
 duced by medicine is 
 very often troubled 
 and unsatisfactory. 
 Medicines of this sort 
 should not be taken 
 except on the advice 
 of a physician. 
 
 While a hearty meal 
 should not usually be 
 taken just before bed- 
 time, it is not well to 
 go to bed with a sense 
 of positive faintness 
 and hunger. Rather, 
 one should take a very 
 light lunch of quite 
 simple food as a sup- 
 port for the next eight 
 hours. 
 
 It is better, as a 
 
 rule, not to engage in FlG - 122. Trunk of the Left Pneumogastric. 
 Severe Study during (Showing its distribution by its branches and ganglia 
 . , , to the larynx, pharynx, heart, lungs, and other parts.) 
 
 the hours just before 
 
 bedtime. Neither body nor mind being at its best after the 
 fatigues of the day, study at that time wears upon the system 
 more, and the progress is less than at earlier hours. One hour 
 of morning or day study is worth a much longer time late at 
 
294 PRACTICAL PHYSIOLOGY. 
 
 night. It is, therefore, an economy both of time and of nerve 
 force to use the day hours and the early evening for study. 
 
 The so-called " cat naps " should never be made to serve as 
 a substitute for a full night's sleep. They are largely a matter 
 of habit, and are detrimental to some as well as beneficial to 
 others. Late hours are usually associated with exposure, 
 excitement, and various other drains upon the nerve force, and 
 hence are injurious. 
 
 It is better to sleep on one or other side than on the back. 
 The head should be somewhat raised, and a mattress is better 
 than a feather bed. The bedclothes should be sufficient, but 
 riot too heavy. Light tends to prevent sleep, as do loud or 
 abrupt sounds, but monotonous sounds aid it. 
 
 291. Alcohol and the Brain. The unfortunate effects which 
 alcoholic drinks produce upon the brain and nervous system 
 differ from the destructive results upon other parts of the body 
 in this respect, that elsewhere the consequences are usually 
 both less speedy and less obvious. The stomach, the liver, 
 and even the heart may endure for a while the trespass of the 
 narcotic poison, and not betray the invasion. But the nervous 
 system cannot, like them, suffer in silence. 
 
 In the other parts of the body the victim may (to a certain 
 extent) conceal from others the suffering of which he himself 
 is painfully conscious. But the tortured brain instantly reveals 
 the calamity and the shame, while the only one who may not 
 fully realize it is the victim himself. Besides this, the injuries 
 inflicted upon other organs affect only the body, but here they 
 drag down the mind, ruin the morals, and destroy the character. 
 
 The brain is indeed the most important organ of the body, 
 as it presides over all the others. It is the lofty seat of power 
 and authority. Here the king is on his throne. But if, by 
 this malignant adversary, the - king himself be dethroned, his 
 whole empire falls to ruins. 
 
THE NERVOUS SYSTEM. 2Q5 
 
 292. How Alcohol Injures the Brain. The brain, the nerve 
 centers, and the nerves are all made up of nerve pulp, the soft- 
 est and most delicate tissue in the whole bodily structure. 
 Wherever this fragile material occurs in our bodies, in the 
 skull, the spine, the trunk, or the limbs, the all-wise Architect 
 has carefully protected it from violence, for a rough touch would 
 injure it, or even tender pressure would disturb its function. 
 
 It is a further indication of the supreme importance of the 
 brain, that about one-fifth of the entire blood of the body is 
 furnished to it. Manifestly, then, this vital organ must be 
 tenderly cared for. It must indeed be well nourished, and 
 therefore the blood sent to it must be highly nutrient, capable 
 of supplying oxygen freely. This condition is essential to suc- 
 cessful brain action. But intoxicants bring to it blood sur- 
 charged with a poisonous liquid, and bearing only a limited 
 supply of oxygen. 
 
 Another condition of a healthy brain is that the supply of 
 blood to it -shall be equable and uniform. But under the 
 influence of strong drink, the blood pours into the paralyzed 
 arteries a surging tide that floods the head, and hinders and 
 may destroy the use of the brain and the senses. Still another 
 requirement is that whatever is introduced into the cerebral tis- 
 sues, having first passed through the stomach walls and thence 
 into the blood, shall be bland, not irritating. But in the 
 brain of the inebriate are found not only the distinct odor but 
 the actual presence of alcohol. Thus we plainly see how all 
 these three vital conditions of a healthy brain are grossly vio- 
 lated by the use of intoxicants. 
 
 " I think there is a great deal of injury being done by the use of alcohol in what 
 is supposed by the consumer to be a most moderate quantity, to persons who are not 
 in the least intemperate, and to people supposed to be fairly well. It leads to degen- 
 eration of the tissues; it damages the health; it injures the intellect. Short of 
 drunkenness, that is, in those effects of it which stop short of drunkenness, I should 
 say from my experience that alcohol is the most destructive agent we are aware of in 
 this country." SIR WILLIAM GULL, the most eminent English physician of our time. 
 
296 PRACTICAL PHYSIOLOGY. 
 
 293. Why the Brain Suffers from the Alcoholic Habit. 
 We do not find that the alcoholic habit has produced in the 
 brain the same coarse injuries that we see in other organs, as 
 in the stomach, the liver, or the heart. Nor should we expect 
 to find them ; for so delicate and so sensitive is the structure 
 of this organ, that a very slight injury here goes a great way, 
 
 a disturbance may be overwhelming to the brain that would 
 be only a trifle to some of the less delicate organs. 
 
 Alcohol has different degrees of affinity for different organs 
 of the body, but much the strongest for the cerebral tissues. 
 Therefore the brain feels more keenly the presence of alcohol 
 than does any other organ. Almost the moment that the 
 poison is brought into the stomach, the nerves send up the 
 alarm that an invading foe has come. At once there follows 
 a shock to the brain, and very soon its paralyzed blood- 
 vessels are distended with the rush of blood. This first effect 
 is, in a certain sense, exhilarating, and from this arousing 
 influence alcohol has been erroneously considered a stimulant; 
 but the falsity of this view is pointed out elsewhere in this 
 book. 
 
 294. Alcohol, the Enemy of Brain Work. The healthy 
 brain contains a larger proportion of water than does any other 
 organ. Now alcohol, with its intense affinity for water, absorbs 
 it from the brain, and thus condenses and hardens its struc- 
 ture. One of the important elements of the brain is its albu- 
 men ; this also is contracted by alcohol. The nerve cells and 
 fibers gradually become shriveled and their activity is lowered, 
 the elasticity of the arteries is diminished, the membranes 
 enveloping the brain are thickened, and thus all proper brain 
 nutrition is impaired. The entire organ is slowly hardened, 
 and becomes unfitted for the proper performance of its delicate 
 duties. In brief, alcohol in any and every form is the enemy 
 of successful and long-continued brain work. 
 
THE NERVOUS SYSTEM. 
 
 297 
 
 295. Other Physical Results of 
 Intoxicants. What are some of the 
 physical results observed ? First, 
 we note the failure of the vaso- 
 motor nerves to maintain the proper 
 tone of the blood-vessels, as in the 
 turgid face and the congested cornea 
 of the eye. Again, we observe the 
 loss of muscular control, as is shown 
 by the drop of the lower lip, the 
 thickened speech, and the wander- 
 ing eye. The spinal cord, too, is 
 often affected and becomes unable 
 to respond to the demand for reflex 
 action, as appears from the trem- 
 bling hands, the staggering legs, the 
 swaying body, and the general mus- 
 cular uncertainty. All these are 
 varied results of the temporary pa- 
 ralysis of the great nerve centers. 
 
 Besides, the sensibility of the 
 nerves is deadened. The inebriate 
 may seize a hot iron and hardly 
 know it, or wound his hand pain- 
 fully and never feel the injury. The 
 numbness is not of the skin, but 
 of the brain, for the drunken man 
 may be frozen or burned to death 
 without pain. The senses, too, 
 are invaded and dulled. Double 
 vision is produced, the eyes not 
 being so controlled as to bring the 
 image upon corresponding points 
 of the retina. 
 
 FIG. 123. Nerve Trunks of the 
 Right Arm. 
 
298 PRACTICAL PHYSIOLOGY. 
 
 296. Diseases Produced by Alcohol. The diseases that 
 follow in the train of the alcoholic habit are numerous and 
 fatal. It lays its paralyzing hand upon the brain itself, and 
 soon permanently destroys the integrity of its functions. In 
 some the paralysis is local only, perhaps in one of the limbs, or 
 on one side of the body ; in others there is a general muscular 
 failure. The vitality of the nerve centers is so thoroughly 
 impaired that general paralysis often ensues. A condition of 
 insomnia, or sleeplessness, often follows, or when sleep does 
 come, it is in fragments, and is far from refreshing to the 
 jaded body. 
 
 In time follows another and a terrible disease known as 
 delirium tremens; and this may occur in those who claim to be 
 only moderate drinkers, rarely if ever intoxicated. It accom- 
 panies an utter breakdown of the nervous system. Here 
 reason is for the time dethroned, while at some times wild and 
 frantic, or at others a low, mumbling delirium occurs, with a 
 marked trembling from terror and exhaustion. 
 
 There is still another depth of ruin in this downward course, 
 and that is insanity. In fact, every instance of complete intox- 
 ication is a case of temporary insanity, that is, of mental un- 
 soundness with loss of self-control. Permanent insanity may 
 be one of the last results of intemperance. Alcoholism sends 
 to our insane asylums a large proportion of their inmates, as 
 ample records testify. 
 
 297. Mental and Moral Ruin Caused by Alcoholism. 
 
 Alcoholism, the evil prince of destroyers, also hastens to lay 
 waste man's mental and moral nature. Just as the inebriate's 
 senses, sight, hearing, and touch, fail to report correctly of the 
 outer world, so the mind fails to preside properly over the 
 inner realm. Mental perceptions are dulled. The stupefied 
 faculties can hardly be aroused by any appeal. Memory fails. 
 Thus the man is disqualified for any responsible labor. No 
 
THE NERVOUS SYSTEM. 299 
 
 railroad company, no mercantile house, will employ any one 
 addicted to drinking. The mind of the drunkard is unable to 
 retain a single chain of thought, but gropes about with idle 
 questionings. The intellect is debased. Judgment is impossi- 
 ble, for the unstable mind cannot think, compare, or decide. 
 
 The once active power of the will is prostrate, and the victim 
 can no longer resist the feeblest impulse of temptation. The 
 grand faculty of self-control is lost ; and as a result, the baser 
 instincts of our lower nature are now uppermost ; greed and 
 appetite rule unrestrained. 
 
 But the moral power is also dragged down to the lowest 
 depths. All the finer sensibilities of character are deadened ; 
 all pride of personal appearance, all nice self-respect and 
 proper regard for the good opinion of others, every sense of 
 decorum, and at last every pretence of decency. Dignity of 
 behavior yields to clownish silliness, and the person lately re- 
 spected is now an object of pity and loathing. The great 
 central convictions of right and wrong now find no place in 
 his nature ; conscience is quenched, dishonesty prevails. This 
 is true both as to the solemn promises, which prove mere 
 idle tales, and also as to property, for he resorts to any form 
 of fraud or theft to feed the consuming craving for more 
 drink. 
 
 298. Evil Results of Alcoholism Inherited. But the calam- 
 ity does not end with the offender. It may follow down the 
 family line, and fasten itself upon the unoffending children. 
 These often inherit the craving for drink, with the enfeebled 
 nature that cannot resist the craving, and so are almost inev- 
 itably doomed to follow the appalling career of their parents 
 before them. 
 
 Nor does this cruel taint stop with the children. Even their 
 descendants are often prone to become perverse. As one 
 example, careful statistics of a large number of families, more 
 
3OO PRACTICAL PHYSIOLOGY. 
 
 than two hundred descended from drunkards, show that a. very 
 large portion of them gave undoubted proof of well-marked 
 degeneration. This was plain in the unusual prevalence of 
 infant mortality, convulsions, epilepsy, hysteria, fatal brain 
 diseases, and actual imbecility. 1 
 
 It is found that the long-continued habitual user of alcoholic 
 drinks, the man who is never intoxicated, but who will tell you 
 that he has drunk whiskey all his life without being harmed by 
 it, is more likely to transmit the evil effects to his children than 
 the man who has occasional drunken outbreaks with intervals 
 of perfect sobriety between. By his frequently repeated small 
 drams he keeps his tissues constantly " alcoholized " to such an 
 extent that they are seldom free from some of the more or less 
 serious consequences. His children are born with organisms 
 which have received a certain bias from which they cannot 
 escape ; they are freighted with some heredity, or predispo- 
 sition to particular forms of degeneration, to some morbid 
 tendency, to an enfeebled constitution, to various defective 
 conditions of mind and body. Let the children of such a man 
 attempt to imitate the drinking habits of the father and they 
 quickly show the effects. Moderate drinking brings them 
 down. 
 
 Among other consequences of an alcoholic inheritance which 
 have been traced by careful observers are : Morbid changes in 
 
 1 According to the Annual Report of New York State Reformatory, for 1896, 
 drunkenness among the inmates can be clearly traced to no less than 38 per cent of 
 the fathers and mothers only. 
 
 Drunkenness among the parents of 38 per cent of the prisoners in a reformatory 
 of this kind is a high and a serious percentage. It shows that the demoralizing 
 influence of drink is apt to destroy the future of the child as well as the character of 
 the parent. 
 
 " There is a marked tendency in nature to transmit all diseased conditions. Thus 
 the children of consumptive parents are apt to be consumptive. But, of all agents, 
 alcohol is the most potent in establishing a heredity that exhibits itself in the 
 destruction of mind and body. There is not only a propensity transmitted, but an 
 actual disease of the nervous system." DR. WILLA.RD PARKER. 
 
THE NERVOUS SYSTEM. 3<DI 
 
 the nerve centers, consisting of inflammatory lesions, which 
 vary according to the age in which they occur; alcoholic 
 insanity ; congenital malformations ; and a much higher infant 
 death rate, owing to lack of vitality, than among the children 
 of normal parents. 
 
 Where the alcoholic inheritance does not manifest itself in 
 some definite disease or disorder, it can still be traced in the 
 limitations to be found in the drinking man's, descendants. 
 They seem to reach a level from which they cannot ascend, 
 and where from slight causes they deteriorate. The parents, 
 by alcoholic poisoning, have lowered the race stock of vitality 
 beyond the power of ascent or possibility to rise above or over- 
 come the downward tendency. 
 
 Of course these effects of alcoholics differ widely according 
 to the degree of intoxication. Yet, we must not forget that 
 the real nature of inebriety is always the same. The end dif- 
 fers from the beginning only in degree. He who would avoid 
 a life of sorrow, disgrace, and shame must carefully shun the 
 very first glass of intoxicants. 
 
 299. Opium. Opium is a gum-like substance, the dried 
 juice of the unripe capsule of the poppy. The head of the 
 plant is slit with fine incisions, and the exuding white juice is 
 collected. When it thickens and is moulded in mass, it be- 
 comes dark with exposure. Morphine, a white powder, is a 
 very condensed form of opiate ; laudanum, an alcoholic solu- 
 tion of marked strength; and paregoric, a diluted and flavored 
 form of alcoholic tincture. 
 
 300. Poisonous Effects of Opium. Some persons are drawn 
 into the use of opium, solely for its narcotic and intoxicating 
 influence. Every early consent to its use involves a lurking 
 pledge to repeat the poison, till soon strong cords of the intox- 
 icant appetite bind the now yielding victim. 
 
3O2 PRACTICAL PHYSIOLOGY. 
 
 Opium thus used lays its benumbing hand upon the brain, 
 the mind is befogged, thought and reasoning are impossible. 
 The secretions of the stomach are suspended, digestion is 
 notably impaired, and the gastric nerves are so deadened that 
 the body is rendered unconscious of its needs. 
 
 The moral sense is extinguished, persons once honest resort 
 to fraud and theft, if need be, to obtain the drug, till at last 
 health, character, and life itself all become a pitiful wreck. 
 
 301. The Use of Opium in Patent Medicines. Some forms 
 of this drug are found in nearly all the various patent medi- 
 cines so freely sold as a cure-all for every mortal disease. 
 Opiates are an ingredient in different forms and proportions 
 in almost all the soothing-syrups, cough medicines, cholera 
 mixtures, pain cures, and consumption remedies, so widely 
 and unwisely used. Many deaths occur from the use of these 
 opiates, which at first seem indeed to bring relief, but really 
 only smother the prominent symptoms, while the disease goes 
 on unchecked, and at last proves fatal. 
 
 These patent medicines may appear to help one person and 
 be fraught with danger to the next, so widely different are 
 the effects of opiates upon different ages and temperaments. 
 But it is upon children that these fatal results oftenest fall. 
 Beyond doubt, thousands of children have been soothed and 
 soothed out of existence. 1 
 
 302. The Victim of the Opium Habit. Occasionally per- 
 sons convalescing from serious sickness where anodynes were 
 taken, unwisely cling to them long after recovery. Other 
 persons, jaded with business or with worry, and unable to 
 sleep, unwisely resort to some narcotic mixture to procure rest. 
 In these and other similar cases, the use of opiates is always 
 
 1 " It is very certain that many infants annually perish from this single cause." 
 REESE'S Manual of Toxicology. 
 
THE NERVOUS SYSTEM. 303 
 
 most pernicious. The amount must be steadily increased to 
 obtain the elusive repose, and at best the phantom too often 
 escapes. 
 
 Even if the desired sleep is procured, it is hardly the coveted 
 rest, but a troubled and dreamy slumber, leaving in the morn- 
 ing the body quite unrefreshed, the head aching, the mouth 
 dry, and the stomach utterly devoid of appetite. But far 
 worse than even this condition is the slavish yielding to the 
 habit, which soon becomes a bondage in which life is shorn of 
 its wholesome pleasures, and existence becomes a burden. 
 
 303. Chloral. There are other preparations which have 
 become instruments of direful and often fatal injury. Chloral 
 is a powerful drug that has been much resorted to by unthink- 
 ing persons to produce sleep. Others, yielding to a morbid 
 reluctance to face the problems of life, have timidly sought 
 shelter in artificial forgetfulness. To all such it is a false 
 friend. Its promises are treason. It degrades the mind, 
 tramples upon the morals, overpowers the will, and destroys 
 life itself. 
 
 304. Cocaine, Ether, Chloroform, and Other Powerful 
 Drugs. Another dangerous drug is Cocaine. Ether and 
 chloroform, those priceless blessings to the human race if 
 properly controlled, become instruments of death when care- 
 lessly trifled with. Persons who have been accustomed to 
 inhale the vapor in slight whiffs for neuralgia or similar trou- 
 bles do so at imminent hazard, especially if lying down. They 
 are liable to become sfowly unconscious, and so to continue 
 the inhalation till life is ended. 
 
 There is still another class of drugs often carelessly used, 
 whose effect, while less directly serious than those mentioned, 
 is yet far from harmless. These drugs, which have sprung 
 into popular use since the disease la grippe began its dreaded 
 career, include phenacetine, antipyrine, antifebrine, and other 
 
304 PRACTICAL PHYSIOLOGY. 
 
 similar preparations. These drugs have been seized by the 
 public and taken freely and carelessly for all sorts and condi- 
 tions of trouble. The random arrow may yet do serious harm. 
 These drugs, products of coal-oil distillation, are powerful 
 depressants. They lower the action of the heart and the tone 
 of the nervous centers. Thus the effect of their continued use 
 is to so diminish the vigor of the system as to aggravate the 
 very disorder they are taken to relieve. 
 
 305. Effect of Tobacco on the Nervous System. That the 
 use of tobacco produces a pernicious effect upon the nervous 
 system is obvious from the indignant protest of the entire body 
 against it when it is first used. Its poisonous character is 
 amply shown by the distressing prostration and pallor, the 
 dizziness and faintness, with extreme nausea and vomiting, 
 which follow its employment by a novice. 
 
 The morbid effects of tobacco upon the nervous system of 
 those who habitually use it are shown in the irregular and 
 enfeebled action of the heart, with dizziness and muscular 
 tremor. The character of the pulse shows plainly the un- 
 steady heart action, caused by partial paralysis of the nerves 
 controlling this organ. Old, habitual smokers often show an 
 irritable and nervous condition, with sleeplessness, due doubt- 
 less to lack of proper brain nutrition. 
 
 All these results tend to prove that tobacco is really a nerve 
 poison, and there is reason to suspect that the nervous break- 
 down of many men in mature life is often due to the continued 
 use of this depressing agent. This is shown more especially 
 in men of sedentary life and habits, as men of active habits 
 and out-door life, experience less of the ill effects of tobacco. 
 
 Few, if any, habitual users of tobacco ever themselves approve 
 of it. They all regret the habit, and many lament they are so 
 enslaved to it that they cannot throw it off. They very rarely 
 advise any one to follow their example. 
 
THE NERVOUS SYSTEM. 305 
 
 306. Effects of Tobacco on the Mind. With this continu- 
 ously depressing effect of tobacco upon the brain, it is little 
 wonder that the mind may become enfeebled and lose its 
 capacity for study or successful effort. This is especially true 
 of the young. The growth and development of the brain 
 having been once retarded, the youthful user of tobacco (espe- 
 cially the foolish cigarette-smoker) has established a permanent 
 drawback which may hamper him all his life. 
 
 The young man addicted to the use of tobacco is often 
 through its use retarded in his career by mental languor or 
 weakening will power, and by mental incapacity. The keen- 
 ness of mental perception is dulled, and the ability to seize 
 and hold an abstract thought is impaired. True, these effects 
 are not sharply obvious, as it would be impossible to contrast 
 the present condition of any one person with what it might 
 have been. But the comparison of large numbers conveys an 
 instructive lesson. Scholars who start well and give promise 
 of a good future fail by the way. The honors of the great 
 schools, academies, and colleges are very largely taken by the 
 tobacco abstainers. This is proved by the result of repeated 
 and extensive comparisons of the advanced classes in a great 
 number of institutions in this country and in Europe. So true 
 is this that any young man who aspires to a noble career should 
 bid farewell either to his honorable ambition or to his tobacco, 
 for the two very rarely travel together. Consequently our mili- 
 tary and naval academies and very many seminaries and col- 
 leges prohibit the use of tobacco by their students. For the 
 same reasons the laws of many states very properly forbid the 
 sale to boys of tobacco, and especially of cigarettes. 
 
 307. Effect of Tobacco upon Character. Nor does tobacco 
 spare the morals. The tobacc9~user is apt to manifest a self- 
 ish disregard of the courtesies due to others. He brings to 
 the presence of others a repulsive breath, and clothing tainted 
 
3O6 PRACTICAL PHYSIOLOGY. 
 
 with offensive odors. He poisons the atmosphere that others 
 must inhale, and disputes their rights to breathe a pure, untainted 
 air. The free use of tobacco by young people dulls the acute- 
 ness of the moral senses, often leads to prevarication and 
 deceit in the indulgence, and is apt to draw one downward to 
 bad associates. It is not the speed but the direction that tells 
 on the future character and destiny of young men. 
 
 ADDITIONAL EXPERIMENTS. 
 
 Experiment 132. To illustrate the cooperation of certain parts of the 
 body. Tickle the inside of the nose with a feather. This does not inter- 
 fere with the muscles of breathing, but they come to the help of the 
 irritated part, and provoke sneezing to clear and protect the nose. 
 
 Experiment 133. Pretend to aim a blow at a person's eye. Even if he 
 is warned beforehand, the lids will close in spite of his effort to prevent 
 them. 
 
 Experiment 134. To illustrate how sensations are referred to the ends of 
 the nerves. Strike the elbow end of the ulna against anything hard (com- 
 monly called " hitting the crazy bone ") where the ulna nerve is exposed, 
 and the little finger and the ring finger will tingle and become numb. 
 
 Experiment 135. To show that every nerve is independent of any other. 
 Press two fingers closely together. Let the point of the finest needle be 
 carried ever so lightly across from one finger to another, and we can easily 
 tell just when the needle leaves one finger and touches the other. 
 
 Experiment 136. To paralyze a nerve temporarily. Throw one arm 
 over the sharp edge of a chair-back, bringing the inner edge of the biceps 
 directly over the edge of the chair. Press deep and hard for a few min- 
 utes. The deep pressure on the nerve of the arm will put the arm 
 " asleep," causing numbness and tingling. The leg and foot often " get 
 asleep " by deep pressure on the nerves of the thigh. 
 
 Experiment 137. Press the ulnar nerve at the elbow, the prickling sen- 
 sation is referred to the skin on the ulnar side of the hand. 
 
 Experiment 138. Dip the elbow in ice-cold water; at first one feels the 
 sensation of cold, owing to the effect on the cutaneous nerve-endings. 
 Afterwards, when the trunk of the ulnar nerve is affected, pain is felt in 
 the skin of the ulnar side of the hand, where the nerve terminates. 
 
CHAPTER XI. 
 THE SPECIAL SENSES. 
 
 308. The Special Senses. In man certain special organs 
 are set apart the particular duty of which is to give information 
 of the nature of the relations which he sustains to the great 
 world of things, and of which he is but a mere speck. The 
 special senses are the avenues by which we obtain this in- 
 formation as to our bodily condition, the world around us, and 
 the manner in which it affects us. 
 
 Animals high in the scale are affected in so many different 
 ways, and by so many agencies, that a subdivision of labor 
 becomes necessary that the sense avenues may be rigidly 
 guarded. One person alone may be a sufficient watch on the 
 deck of a sloop, but an ocean steamer needs a score or more 
 on guard, each with his special duty and at his own post. Or 
 the senses are like a series of disciplined picket-guards, along 
 the outposts of the mind, to take note of events, and to report 
 to headquarters any information which may be within the 
 range of their duty. 
 
 Thus it is that we are provided with a number of Special 
 senses, by means of which information is supplied regarding 
 outward forces and objects. These are touch, taste, smell, 
 seeing, and hearing, to which may be added the muscular 
 sense and a sense of temperature. 
 
 309. General Sensations. The body, as we have learned, 
 is made up of a great number of complicated organs, each 
 doing its own part of the general work required for the life 
 and vigor of the human organism. These organs should all 
 
308 PRACTICAL PHYSIOLOGY. 
 
 work in harmony for the good of the whole. We must have 
 some means of knowing whether this harmony is maintained, 
 and of receiving timely warning if any organ fails to do its 
 particular duty. 
 
 Such information is supplied by the common or general 
 sensations. Thus we have a feeling of hunger or thirst indi- 
 cating the need of food, and a feeling of discomfort when 
 imperfectly clad, informing us of the need of more clothing. 
 
 To these may be added the sensation of pain, tickling, itch- 
 ing, and so on, the needs of which arise from the complicated 
 structure of the human body. The great majority of sensations 
 result from some stimulus or outward agency ; and yet some 
 sensations, such as those of faintness, restlessness, and fatigue 
 seem to spring up within us in some mysterious way, without 
 any obvious cause. 
 
 310. Essentials of a Sense Organ. Certain essentials are 
 necessary for a sensation. First, there is a special structure 
 adapted to a particular kind of influence. Thus the ear is 
 formed specially for being stimulated by the waves of sound, 
 while the eye is not influenced by sound, but responds to the 
 action of light. These special structures are called terminal 
 organs. 
 
 Again, a nerve proceeds from the special structure, which 
 is in direct communication with nerve cells in the brain in 
 the region of consciousness. This last point is important to 
 remember, for if. on some account the impression is arrested in 
 the connecting nerve, no sensation will result. Thus a man 
 whose spine has been injured may not feel a severe pinch on 
 either leg. The impression may be quite sufficient to stimu- 
 late a nerve center in a healthy cord, so as to produce a 
 marked reflex act, but he has no sensation, because the injury 
 has prevented the impression from being carried up the cord 
 to the higher centers in the brain. 
 
THE SPECIAL SENSES. 3OQ 
 
 311. The Condition of Sensation. It is thus evident that 
 while an impression may be made upon a terminal organ, it 
 cannot strictly be called a sensation until the person becomes 
 conscious of it. The consciousness of an impression is, there- 
 fore, the essential element of a sensation. 
 
 It follows that sensation may be prevented in various ways. 
 In the sense of sight, for example, one person may be blind 
 because the terminal organ, or eye, is defective or diseased. 
 Another may have perfect eyes and yet have no sight, because 
 a tumor presses on the nerve between the eye and the brain. 
 In this case, the impression fails because of the break in the 
 communication. Once more, the eye may be perfect and the 
 nerve connection unbroken, and yet the person cannot see, 
 because the center in the brain itself is injured from disease 
 or accident, and cannot receive the impression. 
 
 312. The Functions of the Brain Center in the Perception 
 of an Impression. Sensation is really the result of a change 
 which occurs in a nerve center in the brain, and yet we refer 
 impressions to the various terminal organs. Thus, when the 
 skin is pinched, the sensation is referred to the skin, although 
 the perception is in the brain. We may think it is the eyes 
 that see objects ; in reality, it is only the brain that takes note 
 of them. 
 
 This is largely the result of education and habit. From a 
 blow on the head one sees flashes of light as vividly as if 
 torches actually dance before the eyes. Impressions have 
 reached the seeing-center in the brain from irritation of the 
 optic nerve, producing the same effect as real lights would 
 cause. In this case, however, knowing the cause of the colors, 
 the person is able to correct the erroneous conclusion. 
 
 As a res-alt of a depraved condition of blood, the seeing- 
 center itself may be unduly stimulated, and a person may see 
 objects which appear real. Thus in an attack of delirium 
 
3io 
 
 PRACTICAL PHYSIOLOGY. 
 
 tremens, the victim of alcoholic poisoning sees horrible and 
 fantastic creatures. The diseased brain refers them as usual 
 to the external world ; hence they appear real. As the suffer- 
 er's judgment is warped by the alcoholic liquor, he cannot 
 correct the impressions, and is therefore deceived by them. 
 
 313. Organs of Special Sense. The organs of special 
 sense, the means by which we are brought into relation with 
 surrounding objects, are usually classed as 
 five in number. They are sometimes fanci- 
 fully called " the five gateways of knowledge " 
 the skin, the organ of touch ; the tongue, 
 of taste ; the nose, of smell ; the eye, of 
 sight; and the ear, of hearing. 
 
 314. The Organ of Touch. The organ of 
 touch, or tactile sensibility, is the most widely 
 extended of all the special senses, and perhaps 
 the simplest. It is certainly the most precise 
 and certain in its results. It is this sense to 
 which we instinctively appeal to escape from 
 the illusions into which the other senses may 
 mislead us. It has its seat in the skin all 
 over the body, and in the mucous membrane of the nostrils. 
 All parts of the body, however, do not have this sense in an 
 equal degree. 
 
 In Chapter IX. we learned that the superficial layers of the 
 skin covers and dips in between the papillae. We also learned 
 that these papillae are richly provided with blood-vessels and 
 sensory nerve fibers (sec. 234). Now these nerve fibers termi- 
 nate in a peculiar way in those parts of the body which are 
 endowed with a very delicate sense of touch. In every papilla 
 are oval-shaped bodies about ^ J T of an inch long, around which 
 the nerve fibers wind, and which they finally enter. These are 
 called touch-bodies, or tactile corpuscles, and are found in 
 
 FIG. 124. Magni- 
 fied View of a Pa- 
 pilla of the Skin, 
 with a Touch Cor- 
 puscle. 
 
THE SPECIAL SENSES. 311 
 
 great numbers on the feet and toes, and more scantily in other 
 places, as on the edges of the eyelids. 
 
 Again, many of the nerve fibers terminate in corpuscles, the 
 largest about ^ of an inch long, called Pacinian corpuscles. 
 These are most numerous in the palm of the hand and the sole 
 of the foot. In the papillae of the red border of the lips the 
 nerves end in capsules which enclose one or more fibers, and 
 are called end-bulbs. 
 
 The great majority of the nerve fibers which supply the 
 skin do not end in such well-defined organs. They oftener 
 divide into exceedingly delicate filaments, the terminations of 
 which are traced with the greatest difficulty. 
 
 315. The Sense of Touch. Touch is a sensation of contact 
 referred to the surface of the body. It includes three things, 
 the sense of contact, the sense of pressure, and the sense 
 of heat and cold. 
 
 The sense of contact is the most important element in touch. 
 By it we learn of the form, size, and other properties of objects, 
 as their smoothness and hardness. As we all know, the sense 
 of touch varies in different parts of the skin. It is most acute 
 where the outer skin is thinnest. The tips of the fingers, the 
 edges of the lips, and the tip of the tongue are the most sensi- 
 tive parts. 
 
 Even the nails, the teeth, and the hair have the sense of 
 touch in a slight degree. When the scarf skin is removed, the 
 part is not more sensitive to sense of contact. In fact, direct 
 contact with the unprotected true skin occasions pain, which 
 effectually masks the feeling of touch. The sense of touch is 
 capable of education, and is generally developed to an extra- 
 ordinary degree in persons who are deprived of some other 
 special sense, as sight or hearing. We read of the famous 
 blind sculptor who was said to model excellent likenesses, 
 guided entirely by the sense of touch. An eminent authority 
 
312 PRACTICAL PHYSIOLOGY. 
 
 on botany was a blind man, able to distinguish rare plants by 
 the fingers, and by the tip of the tongue. The blind learn to 
 read with facility by passing their fingers over raised letters of 
 a coarse type. It is impossible to contemplate, even for a 
 moment, the prominence assigned to the sense of touch in the 
 physical organism, without being impressed with the manifes- 
 tations of design the work of an all-wise Creator. 
 
 316. Muscular Sense ; Sense of Temperature ; Pain. 
 
 When a heavy object is laid upon certain parts of the body, 
 it produces a sensation of pressure. By it we are enabled to 
 estimate differences of weight. If an attempt be made to raise 
 this object, it offers resistance which the muscles must over- 
 come. This is known as the muscular sense. It depends on 
 sensory nerves originating in the muscles and carrying impres- 
 sions from them to the nerve centers. 
 
 The skin also judges, to a certain extent, of heat and cold. 
 These sensations can be felt only by the skin. Direct irrita- 
 tion of a nerve does not give rise to them. Thus, the exposed 
 pulp of a diseased tooth, when irritated by cold fluids, gives 
 rise to pain, and not to a sensation of temperature. Various 
 portions of the body have different degrees of sensibility in 
 this respect. The hand will bear a degree of heat which would 
 
 Experiment 139. To illustrate how the sense of touch is a matter of habit 
 or education. Shut both eyes, and let a friend run the tips of your fingers 
 first lightly over a hard plane surface ; then press hard, then lightly again, 
 and the surface will seem to be concave. 
 
 Experiment 140. Cross the middle over the index finger, roll a small 
 marble between the fingers ; one has a distinct impression of two marbles. 
 Cross the fingers in the same way, and rub them against the point of the 
 nose. A similar illusion is experienced. 
 
 Experiment 141. To test the sense of locality. Ask a person to shut 
 his eyes, touch some part of his body lightly with the point of a pin, and 
 ask him to indicate the part touched. 
 
THE SPECIAL SENSES. 313 
 
 cause pain to some other parts of the body. Then, again, 
 the sensibility of the outer skin seems to affect the sensibility 
 to heat, for parts with a thin skin can bear less heat than 
 portions with a thick cuticle. 
 
 As to the general temperature, this sense is relative and is 
 much modified by habit, for what is cold to an. inhabitant of 
 the torrid zone would be warm to one accustomed to a very 
 cold climate. 
 
 Pain is an excessive stimulation of the sensory nerves, and 
 in it all finer sensations are lost. Thus, when a piece of hot 
 iron burns the hand, the sensation is the same as when the 
 iron is very cold, and extreme cold feels like intense heat. 
 
 317. The Organ of Taste. The sense of taste is located 
 chiefly in the tongue, but may also be referred even to the 
 regions of the fauces. Taste, like touch, consists in a particular 
 mode of nerve termination. 
 
 The tongue is a muscular organ covered with mucous mem- 
 brane, and is richly supplied with blood-vessels and nerves. By 
 its complicated movements it is an important factor in chewing, 
 in swallowing, and in articulate speech. The surface of the 
 tongue is covered with irregular projections, called papillae, 
 fine hair-like processes, about T T ^ of an inch high. Interspersed 
 with these are the fungiform papillae. These are shaped some- 
 thing like a mushroom, and may often be detected by their 
 bright red points when the rest of the tongue is coated. 
 
 Towards the root of the tongue is another kind of papillae, 
 the circumvallate, eight to fifteen in number, arranged in the 
 form of the letter V, with the apex directed backwards. These 
 are so called because they consist of a fungiform papilla sur- 
 rounded by a fold of mucous membrane, presenting the appear- 
 ance of being walled around. 
 
 In many of the fungiform and most of the circumvallate 
 papillae are peculiar structures called taste buds or taste 
 
PRACTICAL PHYSIOLOGY. 
 
 goblets. These exist in great numbers, and are believed to 
 be connected with nerve fibers. These taste buds are readily 
 
 excited by savory 
 substances, and 
 transmit the im- 
 pression along the 
 connected nerve. 
 VKn^m The tongue is 
 supplied with sen- 
 sory fibers by 
 branches from the 
 fifth and eighth 
 pairs of cranial 
 nerves. The for- 
 mer confers taste 
 on the front part 
 of the tongue, and 
 the latter on the 
 back part. Branch- 
 es of the latter 
 also pass to the soft 
 palate and neigh- 
 boring .parts and 
 confer taste on 
 them. The motor 
 nerve of the tongue 
 is the ninth pair, 
 the hypoglossal. 
 
 FIG. 125. The Tongue. 
 
 A, epiglottis; B, glands at the base of tongue; C, tonsil; D, 
 median circumvallate papilla ; E, circumvallate papillae ; 
 F, filiform papillae; H, furrows on border of the tongue; 
 K, fungiform papillae. 
 
 318. The Sense of Taste. The sense of taste is excited 
 by stimulation of the mucous membrane of the tongue and of 
 the palate, affecting the ends of the nerve fibers. Taste is 
 most acute in or near the circumvallate papillae. The middle 
 of the tongue is scarcely sensitive to taste, while the edges and 
 the tip are, as a rule, highly sensitive. 
 
THE SPECIAL SENSES. 315 
 
 Certain conditions are necessary that the sense of taste may 
 be exercised. First, the substance to be tasted must be in 
 solution, or be soluble in the fluids of the mouth. Insoluble 
 substances are tasteless. If we touch our tongue to a piece of 
 rock crystal, there is a sensation of contact or cold, but no 
 sense of taste. On the other hand, when we bring the tongue 
 in contact with a piece of rock salt, we experience the sensa- 
 tions of contact, coolness, and saline taste. 
 
 Again, the mucous membrane of the mouth must be moist. 
 When the mouth is dry, and receives substances not already 
 in solution, there is no saliva ready to dissolve them ; hence, 
 they are tasteless. This absence of taste is common with 
 the parched mouth during a fever. 
 
 The tongue assists in bringing the food in contact with the 
 nerves, by pressing it against the roof of the mouth and the 
 soft palate, and thus is produced the fullest sense of taste. 
 
 319. Physiological Conditions of Taste. The tongue is 
 the seat of sensations which are quite unlike each other. 
 Thus, besides the sense of taste, there is the sensation of 
 touch, pressure, heat and cold, burning or acrid feelings, and 
 those produced by the application of the tongue to an inter- 
 rupted electric current. These are distinct sensations, due 
 to some chemical action excited probably in the touch cells, 
 although the true tastes may be excited by causes not strictly 
 chemical. Thus a smart tap on the tongue may excite the 
 sensation of taste. 
 
 In the majority of persons the back of the tongue is most 
 sensitive to bitters, and the tip to sweets. Saline matters are 
 perceived most distinctly at the tip, and acid substances at the 
 sides. The nerves of taste are sensitive in an extraordinary 
 degree to some articles of food and certain drugs. For exam- 
 ple, the taste of the various preparations of quinine, pepper- 
 mint, and wild cherry is got rid of with difficulty. 
 
3l6 PRACTICAL PHYSIOLOGY. 
 
 Like the other special senses, that of taste may become 
 fatigued. The repeated tasting of one substance rapidly dead- 
 ens the sensibility, probably by over-stimulation. Some savors 
 so impress the nerves of taste that others fail to make any 
 impression. This principle is used to make disagreeable medi- 
 cine somewhat tasteless. Thus a few cloves, or grains of coffee, 
 or a bit of pepper, eaten before a dose of castor oil, renders it 
 less nauseous. 
 
 Flavor is something more than taste. It is in reality a mixed 
 sensation, in which smell and taste are both concerned, as is 
 shown by the common observation that one suffering from a 
 cold in the head, which blunts his sense of smell, loses the 
 proper flavor of his food. So if a person be blindfolded, and 
 the nose pinched, he will be unable to distinguish between an 
 apple and an onion, if one be rubbed on the tongue after the 
 other. As soon as the nostrils are opened the difference is at 
 once perceived. 
 
 Experiment 142. Put a drop of vinegar on a friend's tongue, or on 
 your own. Notice how the papillae of the tongue start up. 
 
 Experiment 143. Rub different parts of the tongue with the pointed 
 end of a piece of salt or gum-aloes, to show that the back of the tongue is 
 most sensitive to salt and bitter substances. 
 
 Experiment 144. Repeat the same with some sweet or sour substances, 
 to show that the edges of the tongue are the most sensitive to these sub- 
 stances. 
 
 Experiment 145. We often fail to distinguish between the sense of 
 taste and that of smell. Chew some pure, roasted coffee, and it seems to 
 have a distinct taste. "Pinch the nose hard, and there is little taste. Coffee 
 has a powerful odor, but only a feeble taste. The same is true of garlic, 
 onions, and various spices. 
 
 Experiment 146. Light helps the sense of taste. Shut the eyes, and 
 palatable foods taste insipid. Pinch the nose, close the eyes, and see how 
 palatable one half of a teaspoonful of cod-liver oil becomes. 
 
 Experiment 147. Close the nostrils, shut the eyes, and attempt to dis- 
 tinguish by taste alone between a slice of an apple and one of a potato. 
 
THE SPECIAL SENSES. 317 
 
 320. Modifications of the Sense of Taste. Taste is modi- 
 fied to a great extent by habit, education, and other circumstances. 
 Articles of food that are unpleasant in early life often become 
 agreeable in later years. There is occasionally a craving, espe- 
 cially with people of a peculiar nervous organization, for certain 
 unnatural articles (as chalk and laundry starch) which are eaten 
 without the least repugnance. Again, the most savory dishes may 
 excite disgust, while the simplest articles may have a delicious 
 flavor to one long deprived of them. The taste for certain 
 articles is certainly acquired. This is often true of raw toma- 
 toes, olives, and especially of tobacco. 
 
 The organs of taste and smell may be regarded as necessary 
 accessories of the general apparatus of nutrition, and are, 
 therefore, more or less essential to the maintenance of animal 
 life. While taste and smell are generally maintained until the 
 close of life, sight and hearing are often impaired by time, and 
 may be altogether destroyed, the other vital functions remaining 
 unimpaired. 
 
 321. Effect of Tobacco and Alcohol upon Taste. It would 
 be remarkable if tobacco should fail to injure the sense of 
 taste. The effect produced upon the tender papillae of the 
 tongue by the nicotine-loaded juices and the acrid smoke 
 tends to impair the delicate sensibility of the entire surface. 
 The keen appreciation of fine flavors is destroyed. The once 
 clear and enjoyable tastes of simple objects become dull and 
 vapid ; thus highly spiced and seasoned articles of food are in 
 demand, and then follows continued indigestion, with all its 
 suffering. 
 
 Again, the burning, almost caustic effect of the stronger 
 alcoholic drinks, and the acrid pungency of tobacco smoke, are 
 disastrous to the finer perceptions of both taste and odors. 
 
 322. Smell. The sense of smell is lodged in the delicate 
 membrane which lines the nasal cavities. The floor, sides, 
 
PRACTICAL PHYSIOLOGY. 
 
 I J 
 
 and roof of these cavities are formed by certain bones of the 
 cranium and the face. Man, in common with all air-breathing 
 animals, has two nasal cavities. They communicate with the 
 outer air by two nostrils opening in front, while two other 
 passages open into the pharynx behind. 
 
 To increase the area of the air passages, the two light, 
 spongy turbinated bones, one on each side, form narrow, wind- 
 ing channels. The mucous 
 membrane, with the branches 
 of the olfactory nerve, lines 
 the dividing wall and the 
 inner surfaces of these wind- 
 ing passages. Below all these 
 bones the lower turbinated 
 bones may be said to divide 
 the olfactory chamber above 
 from the ordinary air 
 passages. 
 
 The nerves which supply 
 the nasal mucous membrane 
 are derived from the branch- 
 
 riG. 120. Distribution of Nerves over the 
 
 Interior of the Nostrils. (Outer wall.) es of the fifth and the first 
 
 A, branches of the nerves of smell - olfactory Pair of Cranial nerVCS, - 
 
 nerve, or ganglion ; B, nerves of common sen- t h e O lf actory. The latter 
 
 sation to the nostril ; E, F, G, nerves to the 
 
 palate springing from a ganglion at C ; H, however, are the nerVCS of 
 
 vidian nerve, from which branches D, I, and J sm ell proper, and are Spread 
 
 spring to be distributed to the nostrils. 
 
 out in a kind of thick brush 
 
 of minute nerve filaments. It is in the mucous membrane of 
 the uppermost part of the cavity of the nostril that the nerve 
 endings of smell proper reside. The other nerves which supply 
 the nostrils are those of common sensation (sec. 271). 
 
 323. The Sense of Smell. The sense of smell is excited 
 by the contact of odorous particles contained in the air, with the 
 
THE SPECIAL SENSES. 319 
 
 fibers of the olfactory nerves, which are distributed over the 
 delicate surface of the upper parts of the nasal cavities. In 
 the lower parts are the endings of nerves of ordinary sensa- 
 tion. These latter nerves may be irritated by some substance 
 like ammonia, resulting in a powerfully pungent sensation. 
 This is not a true sensation of smell, but merely an irritation 
 of a nerve of general sensation. 
 
 In ordinary quiet breathing, the air simply flows along the 
 lower nasal passages into the pharynx, scarcely entering the 
 olfactory chamber at all. This is the reason why, when we 
 wish to perceive a faint odor, we sniff up the air sharply. By 
 so doing, the air which is forcibly drawn into the nostrils passes 
 up even into the higher olfactory chamber, where some of the 
 floating particles of the odorous material come into contact 
 with the nerves of smell. 
 
 One of the most essential conditions of the sense of smell is 
 that the nasal passages be kept well bathed in the fluid secreted 
 by the lining membrane. At the beginning of a cold in the head, 
 this membrane becomes dry and swollen, thus preventing the en- 
 trance of air into the upper chamber, deadening the sensibility 
 of the nerves, and thus the sense of smell is greatly diminished. 
 
 The delicacy of the sense of smell varies greatly in different 
 individuals and in different animals. It is generally more acute 
 in savage races. It is highly developed in both the carnivora 
 and the herbivora. Many animals are more highly endowed 
 with this sense than is man. The dog, for example, appears 
 to depend on the sense of smell almost as much as on sight. 
 It is well known, also, that fishes have a sense of smell. Frag- 
 ments of bait thrown into the water soon attract them to a 
 fishing ground, and at depths which little or no light can pene- 
 trate. Deer, wild horses, and antelopes probably surpass all 
 other animals in having a vivid sense of smell. 
 
 Smell has been defined as " taste at a distance," and it is 
 obvious that these two senses not only form a natural group, 
 
32O PRACTICAL PHYSIOLOGY. 
 
 but are clearly associated in their physical action, especially in 
 connection with the perception of the flavor of food. The 
 sense of odor gives us information as to the quality of food 
 and drink, and more especially as to the quality of the air we 
 breathe. Taste is at the gateway of the alimentary canal, while 
 smell acts as the sentinel of the respiratory tract. Just as 
 taste and flavor influence nutrition by affecting the digestive 
 process, so the agreeable odors about us, even those of the 
 perfumes, play an important part in the economy of life. 
 
 324. The Sense of Sight. The sight is well regarded as 
 the highest and the most perfect of all our senses. It plays 
 so common and so beneficent a part in the animal economy 
 that we scarcely appreciate this marvelous gift. Sight is 
 essential not only to the simplest matters of daily comfort and 
 necessity, but is also of prime importance in the culture of 
 the mind and in the higher forms of pleasure. It opens to us 
 the widest and the most varied range of observation and enjoy- 
 ment. The pleasures and advantages it affords, directly and 
 indirectly, have neither cessation nor bounds. 
 
 Apart from its uses, the eye itself is an interesting and in- 
 structive object of study. It presents beyond comparison the 
 most beautiful example of design and artistic workmanship to 
 be found in the bodily structure. It is the watchful sentinel 
 and investigator of the external world. Unlike the senses of 
 taste and smell we seem, by the sense of vision, to become 
 
 NOTE. " The higher intelligence of man is intimately associated with the per- 
 fection of the eye. Crystalline in its transparency, sensitive in receptivity, delicate 
 in its adjustments, quick in its motions, the eye is a fitting servant for the eager 
 soul, and, at times, the truest interpreter between man and man of the spirit's 
 inmost workings. The rainbow's vivid hues and the pallor of the lily, the fair crea- 
 tions of art and the glance of mutual affection, all are pictured in its translucent 
 depths, and transformed and glorified by the mind within. Banish vision, and the 
 material universe shrinks for us to that which we may touch ; sight alone sets us 
 free to pierce the limitless abyss of space." M'KENDRICK and SNODGRASS'S 
 Physiology of the Senses. 
 
THE SPECIAL SENSES. 321 
 
 aware of the existence of objects which are entirely apart from 
 us, and which have no direct or material link connecting them 
 with our bodies. And yet we are told that in vision the eye is 
 affected by something which is as material as any substance we 
 taste or smell. 
 
 Physicists tell us that this material, known as the luminifer- 
 ous ether, permeates the universe, and by its vibrations trans- 
 mits movements which affect the eye, giving rise to -the 
 sensation of light, and the perception of even the most distant 
 objects. Our eyes are so constructed as to respond to the 
 vibrations of this medium for the transmission of light. 
 
 325. The Eye. The eye, the outer instrument of vision, is 
 a most beautiful and ingenious machine. All its parts are 
 arranged with such a delicate adjustment to one another, and 
 such an exquisite adaptation of every part to the great object 
 of the whole, that the eye is properly regarded as one of the 
 wonders of nature. 
 
 The eyeball is nearly spherical in shape, but is slightly 
 elongated from before backwards. The front part is clear and 
 transparent, and bulges somewhat prominently to allow the 
 entrance of the rays of light. The eye rests in a bowl-shaped 
 socket, called the orbit, formed by parts of various bones of 
 the head and face. The margins of this cavity are formed of 
 strong bone which can withstand heavy blows. The socket is 
 padded with loose, fatty tissue, and certain membranes, which 
 serve as a soft and yielding bed in which the eyeball can rest 
 and move without injury. In a severe sickness this fatty tissue 
 is absorbed, and this fact explains the sunken appearance of 
 the eyes. 
 
 The orbit is pierced through its posterior surface by an 
 opening through which the nerve of sight, the optic, passes to 
 the eyeball. We may think of the optic nerve holding the 
 eyeball much as the stem holds the apple. It is the function of 
 
322 
 
 PRACTICAL PHYSIOLOGY. 
 
 this most important nerve to transmit retinal impressions to the 
 seat of consciousness in the brain, where they are interpreted. 
 
 The eye is bathed with a watery fluid, and protected by the 
 eyelids and the eyebrows ; it is moved in various directions, 
 by muscles, all of which will soon be described. 
 
 - SUPER (OR REGTUS 
 
 -CILIARY PROCESSES 
 -SUSPENSORY LIGAMENT 
 
 --SUSPENSORY LIGAMENT 
 CILIARY PROCESSES 
 
 CHOROID 
 
 OPTIC NERVE 
 
 CHOROID 
 
 -INFERIOR RECTHS 
 FIG. 127. Section of the Human Eye. 
 
 326. The Coats of the Eyeball. The eyeball proper is 
 elastic but firm, and is composed of three coats, or layers, each 
 of which performs important functions. These coats are the 
 sclerotic, the choroid, and the retina. 
 
 The sclerotic coat is the outside layer and enclosing mem- 
 brane of the eyeball. It is a tough, fibrous coat for the pro- 
 tection and maintenance of the shape of the eye. It is white 
 
THE SPECIAL SENSES. 323 
 
 and glistening in appearance, and is in part visible, to which 
 the phrase, " the white of the eye," is applied. To this coat, 
 which serves as a kind of framework for the eye, are attached 
 the muscles which move the eyeball. In front of the globe, 
 the sclerotic passes into a transparent circular portion forming 
 a window through which one can see into the interior. This is 
 the cornea. 
 
 The cornea, a clear, transparent, circular disk, fits into the 
 sclerotic, somewhat as the crystal fits into the metallic case of 
 a watch, forming a covering for its dial. It projects from the 
 general contour of the eyeball, not unlike a rounded bay- 
 window, and is often spoken of as the " window of the eye." 
 
 Lining the inner surface of the sclerotic is the second coat, 
 the choroid. It is dark in color and fragile in structure, and 
 is made up almost entirely of blood-vessels and nerves. As 
 the choroid approaches the front part of the eyeball, its parts 
 become folded upon themselves into a series of ridges, called 
 ciliary processes. These folds gradually become larger, and 
 at last merge into the ciliary or accommodation muscle of the 
 eye. The circular space thus left in front by the termination 
 of the choroid is occupied by the iris, a thin, circular curtain, 
 suspended in the aqueous humor behind the cornea and in 
 front of the crystalline lens. In its center is a round opening 
 for the admission of light. 
 
 This is the pupil, which appears as if it were a black spot. 
 The back of the iris is lined with dark pigment, and as the 
 coloring matter is more or less abundant, we may have a 
 variety of colors. This pigment layer and that of the choroid 
 and retina absorb the light entering the eye, so that little is 
 reflected. 
 
 The pupil appears black, just as the open doorway to a dark 
 closet seems black. The margin of the iris is firmly connected 
 with the eyeball all round, at the junction of the sclerotic and 
 the cornea. 
 
324 PRACTICAL PHYSIOLOGY. 
 
 327. The Retina. The third and innermost coat of the 
 eyeball is the retina. This is the perceptive coat, without 
 which it would be impossible to see, and upon which the 
 images of external objects are received. It lines nearly the 
 whole of the inner surface of the posterior chamber, resting on 
 the inner surface of the choroid. It is with the retina, there- 
 fore, that the vitreous humor is in contact. 
 
 The retina is a very thin, delicate membrane. Although 
 very thin, it is made up of ten distinct layers, and is so com- 
 plicated in structure that not even a general description will be 
 attempted in this book. It does not extend quite to the front 
 limits of the posterior chamber, but stops short in a scalloped 
 border, a little behind the ciliary processes. This is the nerve 
 coat of the eye, and forms the terminal organ of vision. It is 
 really an expansion of the ultimate fibers of the optic nerve, 
 by means of which impressions are sent to the brain. 
 
 The retina contains curious structures which can be seen 
 only with the aid of the microscope. For instance, a layer 
 near the choroid is made up of nerve cells arranged in innum- 
 erable cylinders called " rods and cones," and packed together 
 not unlike the seeds of a sunflower. These rods and cones 
 are to be regarded as the peculiar modes of termination of the 
 
 Experiment 148. Close one eye and look steadily at the small a in 
 the figure below. The other letters will also be -visible at the same 
 time. If now the page be brought slowly nearer to the eye while the eye 
 is kept steadily looking at the small a, the large A will disappear at a cer- 
 tain point, reappearing when the book is brought still nearer. 
 
 a o Ax 
 
 On the reappearance of the A it will be noted that it comes into view from 
 the inner side, the x being seen before it. If now w r e move the book back 
 towards its original place, the A will again disappear, coming again into 
 view from the outer side when the o is seen before it. 
 
THE SPECIAL SENSES. 32$ 
 
 nerve filaments of the eye, just as the taste buds are the modes 
 of termination of the nerve of taste in the tongue, and just as the 
 touch corpuscles are the terminations of the nerves in the skin. 
 
 328. Inner Structure of the Eye. Let us imagine an eye- 
 ball divided through the middle from above downwards. Let 
 us now start in front and observe its parts (Fig. 127). We 
 
 OBJECT 
 
 EYE 
 
 FIG. 128. Diagram illustrating the Manner in which the Image of an 
 Object is brought to a Focus on the Retina. 
 
 come first to the cornea, which has just been described. The 
 iris forms a sort of vertical partition, dividing the cavity of the 
 eyeball into two chambers. 
 
 The anterior chamber occupies the space between the cornea 
 and the iris, and is filled with a thin, watery fluid called the 
 aqueous humor. 
 
 The portion behind the iris forms the posterior chamber, 
 and contains the crystalline lens and a transparent, jelly-like 
 fluid, the vitreous humor. This fluid is never renewed, and 
 its loss is popularly described by the phrase, ' when the eye 
 runs out." 
 
 Experiment 149. The retina is not sensitive where the optic nerve 
 enters the eyeball. This is called the " blind spot." Put two ink-bottles 
 about two feet apart, on a table covered with white paper. Close the 
 left eye, and fix the right steadily on the left-hand inkstand, gradually 
 varying the distance from the eye to the ink-bottle. At a certain distance 
 the right-hand bottle will disappear; but nearer or farther than that, it 
 will be plainly seen. 
 
326 
 
 PRACTICAL PHYSIOLOGY. 
 
 The vitreous humor fills about four-fifths of the eyeball and 
 prevents it from falling into a shapeless mass. It also serves 
 to hold the choroid and the retina in position, and to maintain 
 the proper relations of the inner structures of the eye. 
 
 The iris consists of a framework of connective tissue, the 
 surface of which is lined by cells containing pigment, which 
 gives color to the eye. 
 
 Bundles of involuntary muscular fibers are found in the sub- 
 stance of the iris. Some are arranged in a ring round the 
 margin of the pupil ; others radiate from it like the spokes of 
 a wheel. When the circular fibers contract, the pupil is made 
 smaller, but if these fibers relax, the radiating fibers cause the 
 pupil to dilate more or less widely. 
 
 329. The Crystalline Lens. Just behind the pupil and 
 close to the iris is a semi-solid, double-convex body, called the 
 crystalline lens. It is shaped like a magnifying glass, convex 
 
 FIG. 129. Diagram showing the Change in the Lens during Accommodation. 
 
 On the right the lens is arranged for distant vision, the ciliary muscle is relaxed and the 
 ligament D is tense, so flattening by its compression the front of the lens C; on the 
 left the muscle A is acting, and this relaxes the ligament and allows the lens B to 
 become more convex, and so fitted for the vision of near objects. 
 
 on each side, but with the posterior surface more convex than 
 the anterior. In health it is perfectly clear and transparent, 
 and highly elastic. When the lens becomes opaque, from 
 change in old age, or from ulcers or wounds, we have the dis- 
 ease known as cataract. 
 
THE SPECIAL SENSES. 
 
 The lens is not placed loosely in the eyeball, but is enclosed 
 in a transparent and elastic capsule suspended throughout its 
 circumference by a ligament called the suspensory ligament. 
 This ligament not only retains the lens in place, but is capable 
 of altering its shape. In ordinary conditions of the eye, this 
 ligament is kept tense so that the front part of the lens is 
 flattened somewhat by the pressure on it. 
 
 All around the edge, where the cornea, sclerotic, and choroid 
 meet, is a ring of involuntary muscular fibers, forming the 
 ciliary muscle. When these fibers contract, they draw for- 
 wards the attachment of the suspensory ligament of the lens, 
 the pressure of which on the lens is consequently diminished. 
 The elasticity of the lens causes it at once to bulge forwards, 
 and it becomes more convex. 
 
 The ciliary muscle is thus known as the muscle of accom- 
 modation, because it has the power to accommodate the eye 
 to near and distant objects. In this respect it corresponds 
 in its use to the adjusting screw in the opera-glass and the 
 microscope. 
 
 330. The Eye Compared to the Photographic Camera. As an 
 
 optical instrument, the eye may be aptly compared, in many particu- 
 lars, to the photographic camera. The latter, of course, is much 
 simpler in structure. The eyelid forms the cap, which being re- 
 moved, the light from the object streams through the eye and passes 
 across the dark chamber to the retina behind, which corresponds to 
 the sensitive plate of the camera. The transparent structures through 
 which the rays of light pass represent the lenses. To prevent any 
 reflected light from striking the plate and interfering with the sharp- 
 ness of the picture, the interior of the photographic camera box is 
 darkened. The pigmented layer of the choroid coat represents this 
 blackened lining. 
 
 In the camera, the artist uses a thumb-screw to bring to a focus 
 on the sensitive plate the rays of light coming from objects at differ- 
 ent distances. Thus the lens of the camera may be moved nearer to 
 or farther from the object. In order to obtain clear images, the 
 
328 PRACTICAL PHYSIOLOGY. 
 
 same result must be accomplished by the eye. When the eye is 
 focused for near objects, those at a distance are blurred, and when 
 focused for distant objects, those near at hand are indistinct. Now, 
 in the eye there is no arrangement to alter the position of the lenses, 
 as in the camera, but the same result is obtained by what is called 
 " accommodation." 
 
 Again, every camera has an arrangement of diaphragms regulating 
 the amount of light. This is a rude contrivance compared with the 
 iris, which by means of its muscular fibers can in a moment alter the 
 size of the pupil, thus serving a similar purpose. 
 
 OBJECT 
 
 PHOTOGRAPHIC CAMERA 
 
 FIG. 130. Illustrating the manner in which the Image of an Object is 
 brought to a Focus in a Photographer's Camera. 
 
 331. The Refractive Media of the Eye. The eye is a 
 
 closed chamber into which no light can pass but through the 
 cornea. All the rays that enter the eye must also pass through 
 the crystalline lens, which brings them to a focus, as any ordi- 
 nary lens would do. 
 
 Now, if the media through which the light from an object 
 passes to reach the retina were all of the same density as the 
 air, and were also plane surfaces, an impression would be pro- 
 duced, but the image would not be distinct. The action of 
 the lens is aided by several refractive media in the eye. 
 These media are the cornea, the aqueous humor, and the vitre- 
 ous humor. By reason of their shape and density these media 
 refract the rays of light, and bring them to a focus upon the 
 retina, thus aiding in producing a sharp and distinct image of 
 the object. Each point of the image being the focus or meet 
 
THE SPECIAL SENSES. 329 
 
 ing-place of a vast number of rays coming from the correspond- 
 ing point of the object is sufficiently bright to stimulate the 
 retina to action. 1 
 
 Thus, the moment rays of light enter the eye they are bent 
 out of their course. By the action of the crystalline lens, 
 aided by the refractive media, the rays of light that are parallel 
 when they fall upon the normal eye are brought to a focus on 
 the retina. 
 
 If the entire optical apparatus of the eye were rigid and 
 immovable, one of three things would be necessary, in order to 
 obtain a clear image of an object ; for only parallel rays (that 
 is, rays coming from objects distant about thirty feet or more), 
 are brought to a focus in the 
 average normal eye, unless 
 some change is brought about 
 in the refractive media. First, FIG. 131. The Actual Size of the Test- 
 the posterior wall of the eye Ty P e ' which should te seen by the Normal 
 
 * Eye at a Distance of Twenty Feet, 
 
 must be moved further back, 
 
 or the lens would have to be capable of movement, or there 
 must be some way of increasing the focusing power of the 
 lens. In the eye it is the convexity of the lens that is altered so 
 that the eye is capable of adjusting itself to different distances. 2 
 
 332. The More Common Defects of Vision. The eye may 
 be free from disease and perfectly sound, and yet vision be 
 indistinct, because the rays of light are not accurately brought 
 
 1 If an eye removed from its socket be stripped posteriorly of the sclerotic coat, 
 an inverted image of the field of view will be seen on the retina ; but if the lens or 
 other part of the refractive media be removed, the image will become blurred or 
 disappear altogether. 
 
 2 This change in the convexity of the lens is only a slight one, as the difference in 
 the focal point between rays from an object twenty feet distant and one four inches 
 distant is only one-tenth of an inch. While this muscular action is taking place, 
 the pupil contracts and the eyeballs converge by the action of the internal rectus 
 muscles. These three acts are due to the third nerve (the motor oculi). This is 
 necessary in order that each part should be imprinted on the same portion of the 
 retina, otherwise there would be double vision. 
 
330 
 
 PRACTICAL PHYSIOLOGY. 
 
 pr i nt> and t i red eyeSj the 
 
 to a focus on the retina. " Old sight," known as presbyopia, 
 is a common defect of vision in advancing years. This is a 
 partial loss of the power to accommodate the eye to different 
 distances. This defect is caused by an increase in the density 
 of the crystalline lens, and an accompanying diminution in the 
 ability to change its form. The far point of vision is not 
 
 changed, but the near point 
 is removed so far from the 
 eye, that small objects are 
 p no longer visible. 
 
 Hence, when a person 
 about forty-five years of age 
 
 FIG. 132. Diagram illustrating the Hyper- complains of dim light, poor 
 metropic (far-sighted) Eye. 
 
 The image P' of a point P falls behind the retina 
 m the unaccommodated eye. By means or a 
 convex lens it may be focused on the retina advice of an Optician. A 
 without accommodation (dotted lines). (To save conyex lens may be needed 
 space P is placed much too near the eye.) J 
 
 to aid the failing power to 
 
 increase the convexity of the lens, and to assist it in bringing 
 the divergent rays of light to a focus. 
 
 In "long sight," or hypermetropia, both the near and far 
 point of vision are concerned, and there is no distinct vision 
 at any distance without a strain. It is a defect in the focus, 
 dependent upon the form of the eyes, and exists in childhood. 
 The axis of the eyeball is too short, and the focus falls beyond 
 the retina, which is too near the cornea. In childhood this 
 strain may pass unnoticed, but sooner or later it manifests 
 itself by a sense of fatigue, dizziness, and a blurred and indis- 
 tinct vision. The remedy is in the use of convex glasses to 
 converge parallel rays of light before they enter the eye. The 
 muscles of accommodation are thus relieved of their extra work. 
 
 " Short sight," known as myopia, is one of the commonest 
 defects of vision. In this defect the axis of the eye, or the 
 distance between the cornea and the retina, is too long and 
 
THE SPECIAL SENSES. 331 
 
 the rays of light are brought to a focus in front of the retina. 
 The tendency to short-sightedness exists in many cases at 
 birth, and is largely hereditary. It is alarmingly common with 
 those who make a severe demand upon the eyes. During 
 childhood there is a marked increase of near-sightedness. The 
 results of imprudence and abuse, in matters of eyesight, are so 
 disastrous, especially during school life, that the question of 
 short sight becomes one of paramount importance. 
 
 Experiment 150. With a hand-mirror reflect the sunlight on a white 
 wall. Look steadily at the spot for a full minute, and then let the mirror 
 suddenly be removed. The " complementary " color a dark spot will 
 appear. 
 
 Experiment 151. To show that impressions made upon the retina do not 
 disappear at once. Look steadily at a bright light for a moment or two, 
 and then turn away suddenly, or shut the eyes. A gleam of light will be 
 seen for a second or two. 
 
 Look steadily at a well-lighted window for a few seconds, and then turn 
 the eyes suddenly to a darkened wall. The window frame may be plainly 
 seen for a moment. 
 
 Glance at the sun for a moment, close the eyes and the image of the 
 sun may be seen for a few seconds. 
 
 Experiment 152. Take a round piece of white cardboard the size of a 
 saucer, and paint it in alternate rings of red and yellow, two primary 
 colors. Thrust a pin through the center and rotate it rapidly. The eye 
 perceives neither color, but orange, the secondary color. 
 
 Experiment 153. To note the shadows cast upon the retina by opaque 
 matters in the vitreous humor (popularly known as floating specks, or gos- 
 samer threads), look through a small pinhole in a card at a bright light 
 covered by a ground-glass shade. 
 
 Experiment 154. To illustrate accommodation. Standing near a source 
 of light, close one eye, hold up both forefingers not quite in a line, keeping 
 one finger about six or seven inches from the other eye, and the other 
 forefinger about sixteen to eighteen inches from the eye. Look at the near 
 finger ; a distinct image is obtained of it, while the far one is blurred or 
 indistinct. Look at the far image ; it becomes distinct, while the near one 
 becomes blurred. Observe that in accommodating for the near object, 
 one is conscious of a distinct effort. 
 
332 PRACTICAL PHYSIOLOGY. 
 
 In many cases near-sightedness becomes a serious matter 
 and demands skillful advice and careful treatment. To remedy 
 this defect, something must be done to throw farther back the 
 rays proceeding from an object so that they will come to a 
 focus exactly on the retina. This is done by means of con- 
 cave glasses, properly adjusted to meet the conditions of the 
 
 eyes. The selection of suit- 
 able glasses calls for great 
 care, as much harm may be 
 done by using glasses not 
 properly fitted to the eye. 
 There is an optical con- 
 
 FIG. 133- Diagram illustrating the Myopic diti n f J he ^ knOWn SS 
 
 (near-sighted) Eye. astigmatism, in which the 
 
 The image P' of a distant point P falls in front of COmea is USUally at fault. 
 
 iTt.Zi^SnS:^? I" *is defect of vision the 
 
 made to fall on the retina (dotted lines). (To curvature of the COmea is 
 save space Pis placed much too near the eye) greater in Qne meri dian 
 
 than in another. As a result the rays from an object are not 
 all brought to the same focus. Objects appear distorted or are 
 seen with unequal clearness. Glasses of a peculiar shape are 
 required to counteract this defect. 
 
 333. The Movements of the Eyes. In order that our eyes 
 may be efficient instruments of vision, it is necessary that they 
 have the power of moving independently of the head. The 
 mechanical arrangement by which the eyeballs are moved in 
 different directions is quite simple. It is done by six little 
 muscles, arranged in three pairs, which, with one exception, 
 originate in the back of the cavity in which the eye rests. 
 Four of these muscles run a straight course and are called the 
 recti. The remaining two muscles bend in their course and are 
 called oblique. The coordination of these tiny muscles is mar- 
 vellous in its delicacy, accuracy, and rapidity of action. 
 
THE SPECIAL SENSES. 
 
 333 
 
 When, for any cause, the coordination is faulty, "cross eye," 
 technically called strabismus, is produced. Thus, if the in- 
 ternal rectus is shortened, the eye turns in ; if the external 
 rectus, the eye turns out, producing what is known as " wall eye." 
 It is thus evident that the beauty of the internal mechanism of 
 the eye has its fitting complement in the precision, delicacy, 
 and range of movement conferred upon it by its muscles. 
 
 334. The Eyelids and Eyebrows. The eye is adorned and 
 protected by the eyelids, eyelashes, and eyebrows. 
 
 The eyelids, two in number, move over the front of the 
 eyeball and protect it from injury. They consist of folds of 
 
 FIG. 134. Muscles of the Eyeball. 
 
 A, attachment of tendon connected with the three recti muscles ; B, external rectus, 
 divided and turned downward, to expose the internus rectus ; C, inferior rectus ; 
 D, internal rectus; E, superior rectus; F, superior oblique; H, pulley and reflected 
 portion of the superior oblique; K, inferior oblique; L, levator palpebri superioris; 
 M, middle portion of the same muscle (L); N, optic nerve. 
 
 skin lined with mucous membrane, kept in shape by a layer of 
 fibrous material. Near the inner surface of the lids is a row 
 of twenty or thirty glands, known as the Meibomian glands, 
 which open on the free edges of each lid. When one of these 
 
334 PRACTICAL PHYSIOLOGY. 
 
 glands is blocked by its own secretion, the inflammation which 
 results is called a "sty." 
 
 The inner lining membrane of the eyelids is known as the 
 conjunctiva ; it is richly supplied with blood-vessels and nerves. 
 After lining the lids it is reflected on to the eyeballs. It is 
 this membrane which is occasionally inflamed from taking 
 cold. 
 
 The free edges of the lids are bordered with two or more 
 rows of hairs called the eyelashes, which serve both for orna- 
 ment and for use. They help to protect the eyes from dust, 
 and to a certain extent to shade them. Their loss gives a 
 peculiar, unsightly look to the face. 
 
 The upper border of the orbit is provided with a fringe of 
 short, stiff hairs, the eyebrows. They help to shade the eyes 
 from excessive light, and to protect the eyelids from perspira- 
 tion, which would otherwise cause serious discomfort. 
 
 335. The Lacrymal Apparatus. Nature provides a special 
 secretion, the tears, to moisten and protect the eye. The 
 apparatus producing this secretion consists of the lacrymal or 
 tear gland and lacrymal canals or tear passages (Fig. 136). 
 
 Outside of the eyeball, in the loose, fatty tissue of the orbit, 
 in the upper and outer corner is the lacrymal or tear gland. 
 It is about the size of a small almond and from it lead several 
 little canals which open on the inner surface of the upper lid. 
 The fluid from the gland flows out by these openings over the 
 eyeball, and is collected at the inner or nasal corner. Here in 
 each lid is a little reddish elevation, or lacrymal caruncle, in 
 which is an opening, communicating with a small canal in the 
 lid which joins the lacrymal sac, lodged between the orbit and 
 the bridge of the nose (Fig. 137). 
 
 From this sac there passes a channel, the nasal duct, about 
 one-half of an inch long, leading into the lower portion of the 
 nostril. The fluid which has flowed over the eye is drained 
 
THE SPECIAL SENSES. 
 
 335 
 
 off by these canals into the nose. During sleep this secretion 
 is much diminished. When the eyes are open the quantity is 
 sufficient to moisten the eyeball, the excess being carried into 
 the nose so gradually that the attention is not attracted to it. 
 
 The lacrymal canals are at times blocked by inflammation of 
 the nasal duct, and the fluid collects in the corners of the eyelids 
 and overflows down the cheeks, producing much inconvenience. 
 The lining membrane of the eyelids through these canals is 
 continuous with that of the nostrils. Hence, when the lining 
 membrane of the eye is red and swollen, as during a cold, the 
 nasal passages are also irri- 
 tated, and when the nasal 
 membrane is inflamed, the 
 irritation is apt to pass up- 
 wards and affect the eyelids. 
 
 336. The Tears. The 
 
 lacrymal or tear gland is 
 under the control of the 
 nervous system. Thus, if 
 anything irritates the eyelids, 
 the sensory nerves are stimu- 
 lated and the impression is 
 carried to the brain. Thence FlG - T 35- Lacrymal Gland and Ducts. 
 
 the nerve impulses travel tO A, lachrymal gland, the size of a small almond, 
 
 1 lodged in a shallow depression in the bones of 
 
 the lacrymal glands, leading the orbit; B, lachrymal ducts (usually seven), 
 
 to an increased flow of their which f rm , a row of openings into the con - 
 
 junctival fold. 
 
 secretion. The irritation of 
 
 the sensory nerves in the nasal passages by smelling such 
 substances as onions, or pungent salts, often causes a copious 
 flow of tears. 
 
 Various mental emotions, as joy and grief, may produce 
 similar results. In these cases the glands secrete the fluid in 
 such quantities that it cannot escape by the lacrymal canals, 
 
PRACTICAL PHYSIOLOGY. 
 
 and the excess rolls over the cheeks as tears. Excessive grief 
 sometimes acts on the nerve centers in exactly the opposite 
 manner, so that the activity of the glands is arrested and less 
 fluid is secreted. This explains why some people do not shed 
 tears in times of deep grief. 
 
 Experiment 155. Gently turn the inner part of your lower eyelid down. 
 Look in a mirror, and the small lacrymal point, or opening into the nasal 
 duct, may be observed. 
 
 337. Color-blindness. There is an abnormal condition of 
 vision called color-blindness, in which the power of discrimina- 
 tion between different colors is impaired. Experiment shows 
 that ninety-six out of every one hundred men agree as to the 
 identity or the difference of color, while the remaining four 
 show a defective perception of color. 
 
 The first may be said to have normal vision ; the second are 
 called color-blind. It is a curious fact that ten times more men 
 than women are color-blind. 
 
 In its true sense, color-blindness is always congenital, often 
 hereditary. This condition of abnormal vision is totally incur- 
 able. A person may be color-blind and not know it until the 
 defect is accidentally revealed. The common form of defective 
 color-vision is the inability to distinguish between red and 
 green. As green lights mean safety, and red lights danger, on 
 railroads, on shipboard, and elsewhere, it becomes of paramount 
 importance that no one who is color-blind should be employed 
 in such service. Various tests are now required by statute law 
 in many states to be used for the detection of such defects of 
 vision among employees in certain occupations. 
 
 338. School Life and the Eyesight. The eyes of children need 
 more care than those of adults, because their eyes are still in the 
 course of development. The eyes, like any other organ which is yet 
 to attain its full growth, require more care in their use than one 
 which has already reached its full size. They are peculiarly liable to 
 
THE SPECIAL SENSES. 337 
 
 be affected by improper or defective light. Hence the care of the 
 eyes during school life is a matter of the most practical importance. 
 
 In no matter of health can the teacher do a more distinct service 
 than in looking after the eyesight of the pupils. Children suffering 
 from defective vision are sometimes punished by teachers for supposed 
 stupidity. Such pupils, as well as the deaf, are peculiarly sensitive 
 to their defects. Every schoolroom should have plenty of light ; it 
 should come from either side or the rear, and should be regulated 
 with suitable shades and curtains. 
 
 Pupils should not be allowed to form the bad habit of reading with 
 the book held close to the eyes. The long search on maps for 
 obscure names printed in letters of bad and trying type should be 
 discouraged. Straining the eyes in trying to read from slates and 
 blackboards, in the last hour of the afternoon session, or in cloudy 
 weather, may do a lifelong injury to the eyesight. Avoid the use, so 
 far as possible, especially in a defective light, of text-books which 
 are printed on battered type and worn plates. 
 
 The seat and desk of each scholar should be carefully arranged 
 to suit the eyesight, as well as the bones and muscles. Special pains 
 should be taken with the near-sighted pupils, and those who return to 
 school after an attack of scarlet fever, measles, or diphtheria. 
 
 Experiment 156. To test color-blindness. On no account is the person 
 being tested to be asked to name a color. In a large class of students one 
 is pretty sure to find some who are more or less color-blind. The common 
 defects are for red and green. 
 
 Place worsteds on a white background in a good light. Select, as a 
 test color, a skein of light green color, such as would be obtained by mix- 
 ing a pure green with white. Ask the examinee to select and pick out 
 from the heap all those skeins which appear to him to be of the same 
 color, whether of lighter or darker shades. A color-blind person will 
 select amongst others some of the confusion-colors, e.g., pink, yellow. A 
 colored plate showing these should be hung up in the room. Any 
 one who selects all the greens and no confusion-colors has normal color 
 vision. If, however, one or more confusion-colors be selected, proceed as 
 follows : select as a test color a skein of pale rose. If the person be red- 
 blind, he will choose blue and violet ; if green-blind, gray and green. 
 
 Select a bright red skein. The red-blind will select green and brown ; 
 the green-blind picks out reds or lighter brown. 
 
338 
 
 PRACTICAL PHYSIOLOGY. 
 
 339. Practical Hints on the Care of the Eyes. The eye 
 
 is an exceedingly delicate and sensitive organ. While it is long- 
 suffering, its endurance has a limit. Like all the other organs 
 of the body, the eyes are better for moderate and rational use. 
 More than any other organ they require attention to the gen- 
 eral health, as the condition of the skin, exercise in the open 
 air, good food, and proper habits of daily living. 
 
 The tissues of the eyes are peculiarly sensitive to any general 
 influence. Certain constitutional diseases, like rheumatism, 
 lead-poisoning, diphtheria, and measles often affect the eyes. 
 
 Special care should be 
 taken with children's 
 eyes during and after 
 an attack of measles 
 and scarlet fever. The 
 eyes of young infants 
 should not be exposed 
 to glaring lights or to 
 the direct rays of the 
 sun, as when taken out 
 FIG. 136. Showing the Relative Position of in baby carriages. 
 
 the Lacrymal Apparatus, the Eyeball, and the 
 Eyelids. 
 
 be 
 
 Glasses should 
 worn when they are 
 A failure to 
 
 A, lacrymal canals, with the minute orifices represented 
 as two black dots (puncta lacrymalia) to the right; 
 B, tendon of the orbicularis palpebrarum muscle ; do this USUally CaUSCS 
 apparently under B is seen the lacrymal sac. The 
 minute openings of the Meibomian glands are seen on 
 the free margins of the eyelids. Below A is seen a fering. 
 small conical elevation, with black dots (the lacrymal 
 papilla or caruncle). 
 
 unnecessary suf- 
 It is far from 
 wise to postpone as 
 long as possible the 
 The selection and proper fitting of 
 glasses call for the combined skill of both the physician 
 and the optician. Obstinate headaches are often caused by 
 defective vision, and may disappear after discontinuing im- 
 proper glasses. 
 
 first use of glasses. 
 
THE SPECIAL SENSES. 339 
 
 The habit of reading, in the cars or elsewhere, the daily paper 
 and poorly printed books, with their blurred and indistinct 
 type, is a severe strain on the accommodation apparatus of the 
 eyes. It is a dangerous practice to read in bed at night, or 
 while lying down in a darkened or shaded room. This is 
 especially true during recovery from illness. The muscles of 
 the eyes undergo excessive strain in accommodating them- 
 selves to the unnatural position. The battered type, wood-pulp 
 paper, and poor presswork, now so commonly used in the cheap 
 editions of books and periodicals, are often injurious to the 
 eyesight. 
 
 Reading-matter should not be held nearer to the eyes than 
 is necessary to make the print appear perfectly sharp and dis- 
 tinct. No print should be read continuously that cannot be 
 seen clearly at about eighteen inches. Those who read music 
 are especially liable to strain the eyes, because exact vision is 
 required to follow the notes. Persons who wear glasses for 
 reading should be careful to use them while reading music, and 
 good light is necessary to avoid any undue strain. 
 
 After reading steadily for some time, the eyes should be rested 
 by closing them a short period or by looking at some distant 
 object, even if only for a few moments. The book, the sewing, 
 and work generally, should be held as far from the eyes as is 
 compatible with good vision. The natural tendency is to re- 
 verse this rule. We should never read, write, sew, stitch, or 
 otherwise use the eyes when they smart or tingle, or when the 
 sight is dim or blurred. The eyes are then tired and need a 
 rest. Much injury may be done by reading in twilight, or by 
 artificial light in the early morning, and by reading and work- 
 ing in badly lighted and ill-ventilated rooms. 
 
 Good artificial light is much to be preferred to insufficient 
 sunlight. The artificial light should be sufficiently bright and 
 steady ; a flickering light is always bad. Riding against a 
 strong wind, especially on a bicycle, may prove hurtful, at least 
 
34O PRACTICAL PHYSIOLOGY. 
 
 for eyes that are inclined to any kind of inflammation. The 
 light reflected from snow is a common source of injury to the 
 eyes. It is a wise caution in passing from a dark room to 
 avoid looking immediately at the sun, an incandescent light, 
 the glistening snow, or other bright objects. 
 
 The eyes should never be rubbed, or the fingers thrust into 
 them, 1 and much less when they are irritated by any foreign 
 substance. The sooner the offending substance is removed 
 the better. 
 
 340. Effect of Alcohol upon the Eye. The earlier and 
 slighter forms of injury done to the eye by the use of intoxi- 
 cants are quite familiar : the watery condition of the eye and of 
 the lids, and the red and bleared aspect of 
 the organ. Both are the result of chronic 
 inflammation, which crowds the blood into 
 the vessels of the cornea, making them 
 bloodshot and visible. The nerves con- 
 trolling the circulation of the eye are 
 partially paralyzed, and thus the relaxed 
 
 r vessels become distended. 
 
 But more serious results ensue. Long 
 use of intoxicants produces diseases of 
 the retina, involving in many cases marked 
 FIG. 137. Lacrymal Can- diminution of acuteness as well as quick- 
 
 als, Lacrymal Sac, and ness Q f v i s i orij an d at times distorted 
 Nasal Duct, opened by . //-, 
 
 their Anterior Portion, -images upon the surface of the retina. In 
 other instances, the congestion of the 
 
 optic nerve is so serious as to involve a progressive wasting 
 of that organ, producing at first a hazy dimness of vision 
 which gradually becomes worse and worse, till total blindness 
 may ensue. 
 
 1 The Germans have a quaint proverb that one should never rub his eye. except 
 with his elbows ! 
 
THE SPECIAL SENSES. 341 
 
 It is beyond question that a wide comparison of cases by 
 careful observers proves that a large fraction of those who 
 indulge in strong drink suffer from some form of disease of the 
 eye. 
 
 341. Effect of Tobacco upon Vision. Tobacco, in its dis- 
 tribution of evil effects, does not neglect the senses and 
 especially the eye. A variety of vicious results is produced. 
 The pungent smoke inflames the lids. The narcotic dilates 
 the pupil, causing dimness and confusion of vision. A dis- 
 eased condition occurs with severe pain in the eye followed by 
 impaired vision. 
 
 Oculists speak impressively of the ill effects of tobacco, and 
 especially of cigarettes, upon the eyes of the young. They 
 mention a well-known disease, tobacco blindness, usually be- 
 ginning with color-blindness, and progressing occasionally with 
 increasing dimness of vision to entire loss of sight. 1 
 
 342. The Sense of Hearing. The structure of the human 
 ear is much more complicated than is generally supposed. It 
 is an apparatus constructed to respond to the waves of sound. 
 As a whole, it may be considered a peculiar form of nerve- 
 ending. 
 
 1 " The deleterious effect of tobacco upon eyesight is an acknowledged fact. 
 The Belgian government instituted an investigation into the cause of the prevalence 
 of color-blindness. The unanimous verdict of the experts making the examination 
 was that the use of tobacco was one of the principal causes of this defect of vision. 
 
 " The dimness of sight caused by alcohol or tobacco has long been clinically 
 recognized, although not until recently accurately understood. The main facts can 
 now be stated with much assurance, since the publication of an article by Uhthoff 
 which leaves little more to be said. He examined one thousand patients who were 
 detained in hospital because of alcoholic excess, and out of these found a total of eye 
 diseases of about thirty per cent. 
 
 " Commonly both eyes are affected, and the progress of the disease is slow, both 
 in culmination and in recovery. . . . Treatment demands entire abstinence." 
 HENRY D. NOYES, Professor of Otology in the Bellevue Hospital Medical College, 
 New York. 
 
342 
 
 PRACTICAL PHYSIOLOGY. 
 
 The external ear forms only a part of a most elaborate appa- 
 ratus whereby sound waves may be transmitted inwards to the 
 real organ of hearing. The really sensitive part of the ear, 
 in which the auditory nerve ends, is buried for protection deep 
 out of sight in the bones of the head ; so deep that sounds 
 cannot directly affect it. Some arrangement, therefore, is 
 required for conducting the sounds inwards to this true organ. 
 
 In studying the structure 
 of the ear, and how it is 
 fitted to respond to sonorous 
 vibrations, we may divide it 
 into three parts : the sound- 
 conducting part, known as 
 the external ear, the middle 
 ear, and the deeply placed 
 nerve portion, the inner ear. 
 
 343. The External Ear. 
 The external ear consists of 
 an expanded portion known 
 as the pinna or auricle, and 
 of a passage, the auditory 
 canal or meatus, leading in- 
 wards from it. The surface 
 of the auricle is convoluted to collect and transmit the 
 vibrations of air by which sound is produced : the auditory 
 canal conducts these vibrations to the tympanic membrane. 
 Many animals move the auricle in the direction of the sound. 
 Thus the horse pricks up its ears when it hears a noise, the 
 better to judge of the direction of sounds. 1 
 
 1 " The student who will take a little trouble in noticing the ears of the persons 
 whom he meets from day to day will be greatly interested and surprised to see how 
 much the auricle varies. It may be a thick and clumsy ear or a beautifully delicate 
 one ; long and narrow or short and broad ; may have a neatly formed and distinct 
 lobule, or one that is heavy, ungainly, and united to the cheek so as hardly to form a 
 
 FIG. 138. The Pinna, or Auricle. 
 
THE SPECIAL SENSES. 343 
 
 The external auditory meatus, the passage to the middle ear, 
 is curved and is about an inch and a quarter long. Near its 
 outer portion are a number of fine hairs slanting outwards to 
 prevent the entrance of insects. Embedded in the deeper 
 parts of the canal are glands which secrete the cerumen, or ear- 
 wax, which keeps the canal moist, and helps to protect it against 
 foreign bodies and insects. As the result of a cold, this wax 
 may collect in sufficient quantities to block the passage, and 
 to diminish to a considerable extent the power of hearing. 
 
 344. The Middle Ear. At the inner end of the outer ear 
 passage is the tympanum, known as "the drum of the ear." 
 It is a thin, oval membrane, stretched at an angle across the 
 deep end of the passage, which it completely closes. The 
 tympanum is thus a partition between the passage of the outer 
 ear and the cavity of the middle ear. On its inner side is a 
 small air chamber in the petrous portion of the temporal bone, 
 called the cavity of the tympanum. Its bony walls are lined 
 with mucous membrane similar to that lining the nose, mouth, 
 and throat. On the inner wall of the tympanum are two open- 
 ings, the round window, or foramen rotundum, and the oval 
 window, or foramen ovale. 
 
 The tympanic cavity communicates with the back part of 
 the throat, by the Eustachian tube. This tube is about one 
 and a half inches long and lined with mucous membrane 
 similar to that of the tympanic chamber and the throat. This 
 passage is usually closed, but is opened in the act of swallowing. 
 In health there is no communication between the chamber of the 
 middle ear and the outside, except by the Eustachian tube. Thus 
 a throat cold, with redness and swelling of the mucous mem- 
 brane, is usually accompanied with some degree of deafness, 
 
 separate part of the auricle ; may hug the head closely or flare outward so as to form 
 almost two wings to the head. In art, and especially in medallion portraits, in which 
 the ear is a marked (because central) feature, the auricle is of great importance." 
 WILLIAM W. KEEN, M.D., editor of Gray's Anatomy. 
 
344 
 
 PRACTICAL PHYSIOLOGY. 
 
 because the swelling may block the lumen of the tube, and 
 thus prevent the free passage of air to and fro. 
 
 A most curious feature of the ear is the chain of tiny movable 
 bones which stretch across the cavity of the middle ear. They 
 connect the tympanic membrane with the labyrinth, and serve 
 to convey the vibrations communicated to the membrane across 
 the cavity of the tympanum to the internal ear. These bones 
 
 FIG. 139. General View of the Organ of Hearing. 
 
 A, pinna; B, cavity of the concha, showing the orifices of a great number of sebaceous 
 glands ; C, external auditory meatus ; D, membrana tympani ; F, incus ; H, malleus ; 
 K, handle of malleus applied to the internal surface of the membrana tympani ; L, 
 tensor tympani muscle; between M and K is the tympanic cavity ; N, Eustachian 
 tube ; O, P, semicircular canals ; R, internal auditory canal ; S, large nerve given 
 off from the facial ganglion ; T, facial and auditory nerves. 
 
 are three in number, and from their shape are called the 
 malleus, or hammer ; incus, or anvil ; and stapes, or stirrup. 
 The hammer is attached by its long handle to the inner sur- 
 face of the drum of the ear. The round head is connected 
 with the anvil by a movable joint, while the long projection of 
 the anvil is similarly connected with the stirrup bone. The 
 plate of the stirrup is fixed by a membrane into the oval window 
 of the inner wall of the tympanic chamber. 
 
THE SPECIAL SENSES. 
 
 345 
 
 1, malleus, or hammer; 
 2, incus, or anvil ; 3, 
 tapes, or stirrup. 
 
 These little bones are connected with each other and the 
 tympanum by ligaments and moved by three tiny muscles. 
 Two are attached to the hammer, and tighten and relax the 
 drum ; the other is attached to the stirrup, and prevents it 
 from being pushed too deeply into the 
 oval window. 
 
 345. The Internal Ear. This forms one 
 of the most delicate and complex pieces of 
 mechanism in the whole body. It is that 
 portion of the organ which receives the im- 
 
 -.-... .. . FIG. 140. Ear-Bones. 
 
 pression of sound, and carries it directly to (Anterior view.) 
 the seat of consciousness in the brain. We 
 are then able to say that we hear. 
 
 The internal ear, or bony labyrinth, 
 consists of three distinct parts, or variously shaped chambers, 
 hollowed out in the temporal bone, the vestibule, the semi- 
 circular canals, and the cochlea, or snail's shell. 
 
 The vestibule is the 
 common cavity with 
 which all the other 
 portions of the labyrinth 
 connect. It is an oval- 
 shaped chamber, about 
 of an inch in diameter, 
 occupying the middle part 
 of the internal ear. It is 
 on the inner side of the 
 oval window, which was 
 closed, as we have seen, 
 
 FIG. 141.- A Cast of the External Auditory fe the ^ bone From 
 
 Canal. (Posterior view.) ' r 
 
 one side of this vestibule, 
 
 or central hall, the three semicircular canals pass off, and 
 from the other side, the cochlea. 
 
34-6 PRACTICAL PHYSIOLOGY. 
 
 The three semicircular canals, so called from their shape, 
 are simply bony tubes about ^ G of an inch in width, making 
 a curve of about J of an inch in diameter. They pass out 
 from the vestibule, and after bending around somewhat like a 
 hoop, they return again to the vestibule. Each bony canal 
 contains within it a membranous canal, at the end of which it 
 is dilated to form an ampulla, 
 
 Experiment 157. To vibrate the tympanic membrane and the little ear- 
 bones. Shut the mouth, and pinch the nose tightly. Try to force air through 
 the nose. The air dilates the Eustachian tube, and is forced into the ear- 
 drum. The distinct crackle, or clicking sound, is due to the movement of 
 the ear-bones and the tympanic membrane. 
 
 The cochlea, or snail's shell, is another chamber hollowed 
 out in the solid bone. It is coiled on itself somewhat like a 
 snail's shell. There is a central pillar, around which winds a 
 long spiral canal. One passage from the cochlea opens directly 
 into the vestibule ; the other leads to the chamber of the mid- 
 dle ear, and is separated from it by the little round window 
 already described. 
 
 The cochlea contains thousands of the most minute cords, 
 known as the fibers or organ of Corti. 1 Under the microscope 
 they present the appearance of the keyboard of a piano. 
 These fibers appear to vibrate in sympathy with the countless 
 shades of sounds which daily penetrate the ear. From the 
 hair-like processes on these tightly stretched fibers, auditory 
 impulses appear to be transmitted to the brain. 
 
 1 The organ of Corti is a very complicated structure which it is needless to 
 describe in this connection. It consists essentially of modified ephithelial cells 
 floated upon the auditory epithelium, or basilar membrane, of the cochlea. There 
 is a series of fibers, each made of two parts sloped against each other like the rafters 
 of a roof. It is estimated that there are no less than 3000 of these arches in the 
 human ear, placed side by side in a continuous series along the whole length of the 
 basilar membrane. Resting on these arches are numbers of conical epithelial cells, 
 from the free surface of which bundles of stiff hairs (cilia) project. The fact that 
 these hair-cells are connected with the fibers of the cochlear division of the auditory 
 nerve suggests that they must play an important part in auditory sensation. 
 
THE SPECIAL SENSES. 
 
 347 
 
 The tubes and chambers of the inner ear enclose and pro- 
 tect a delicate membranous sac of exactly the same shape as 
 themselves. Between the bony walls of the passages and the 
 membranous bag inside is a thin, clear fluid, the perilymph. 
 The membranous bag itself contains a similar fluid, the endo- 
 lymph. In this fluid are found some minute crystals of lime 
 like tiny particles of sand, called otoliths, or ear-stones. Every 
 
 movement of the fluid itself 
 throws these grains from side 
 to side. 
 
 The auditory nerve, or 
 nerve of hearing, passes to 
 the inner ear, through a pas- 
 sage in the solid bone of the 
 skull. Its minute filaments 
 spread at last over the inner 
 walls of the membranous laby- 
 FIG. 142. Bony internal Ear of the rinth in two branches, one 
 
 Right Side. (Magnified; the upper tQ the vestibule and the 
 
 figure of the natural size.) 
 
 . . , ., , . Q _ _ . ampullae at the ends of the 
 
 A, oval window (foramen ovale) ; B, C, D, semi- 
 circular canals; * represents the bulging semicircular canals, the other 
 
 part (ampulla) of each canal; E, F, G coch- leadi t ^ cochlea. 
 lea; H, round window (foramen rotundum). 
 
 346. Mechanism of Hearing. Waves of sound reach the 
 ear, and are directed by the concha to the external passage, 
 at the end of which they reach the tympanic membrane. 
 When the sound-waves beat upon this thin membrane, it is 
 thrown into vibration, reproducing in its movements the char- 
 acter of the air-vibrations that have fallen upon it. 
 
 Now the vibrations of the tympanic membrane are passed 
 along the chain of bones attached to its inner surface and 
 reach the stirrup bone. The stirrup now performs a to-and- 
 fro movement at the oval window, passing the auditory impulse 
 inwards to the internal ear. 
 
34-8 PRACTICAL PHYSIOLOGY. 
 
 Every time the stirrup bone is pushed in and drawn out of 
 the oval window, the watery fluid (the perilymph) in the vesti- 
 bule and inner ear is set in motion more or less violently, 
 according to the intensity of the sound. The membranous 
 labyrinth occupies the central portion of the vestibule and the 
 passages leading from it. When, therefore, the perilymph is 
 shaken it communicates the impulse to the fluid (endolymph) 
 contained in the inner membranous bag. The endolymph and 
 the tiny grains of ear-sand now perform their part in this 
 marvelous and complex mechanism. They are driven against 
 the sides of the membranous bag, and so strike the ends of 
 the nerves of hearing, which transmit the auditory impulses 
 to the seat of sensation in the brain. 
 
 It is in the seat of sensation in the brain called the sensorium 
 that the various auditory impulses received from different parts 
 of the inner ear are fused into one, and interpreted as sounds. 
 It is the extent of the vibrations that determines the loudness 
 of the sound ; the number of them that determines the pitch. 
 
 Experiment 158. Hold a ticking watch between the teeth, or touch 
 the upper incisors with a vibrating tuning-fork ; close both ears, and observe 
 that the ticking or vibration is heard louder. Unstop one ear, and ob- 
 serve that the ticking or vibration is heard loudest in the stopped ear. 
 
 Experiment 159. Hold a'vibrating tuning-fork on the incisor teeth until 
 you cannot hear it sounding. Close one or both ears, and you will hear it. 
 
 Experiment 160. Listen to a ticking watch or a tuning-fork kept vibrat- 
 ing electrically. Close the mouth and nostrils, and take either a deep 
 inspiration or deep expiration, so as to alter the tension of the air in the 
 tympanum ; in both cases the sound is diminished. 
 
 Experiment 161. With a blindfolded person test his sense of the direc- 
 tion of sound, e.g., by clicking two coins together. It is very imperfect. 
 Let a person press both auricles against the side of the head, and hold both 
 hands vertically in front of each meatus. On a person making a sound in 
 front, the observed person will refer it to a position behind him. 
 
THE SPECIAL SENSES. 349 
 
 347. Practical Hints on the Care of the Ear. This very 
 delicate and complicated organ is often neglected when skilled 
 treatment is urgently needed, and it is often ignorantly and 
 carelessly tampered with when it should be let alone. 
 
 Never insert into the ear canal the corners of towels, ear 
 spoons, the ends of toothpicks, hairpins, or any other pointed 
 instruments. It is a needless and dangerous practice, usually 
 
 VESTIBULE WITH OPENINGS 
 ,'OF SEMICIRCULAR CANALS 
 
 SCALA VESTIBULI 
 
 ^V /- INCUS 
 /_./- MALLEUS 
 
 -STAPES 
 
 EXT. AUD. MEATUS. 
 MEMBRANA TYMPANI 
 
 SCALA TVMPANI 
 
 EUSTACHIAN TUBE 
 
 FIG. 143. Diagram of the Middle and Internal Ear. 
 
 causing, in time, some form of inflammation. The abrasion of 
 the skin in the canal thus produced affords a favorable soil 
 for the growth of vegetable parasites. 
 
 This, in turn, may lead to a chronic inflammation of the 
 canal and of the tympanic membrane. Again, there is always 
 risk that the elbow may be jogged and the instrument pushed 
 through the drum-head. There is, of course, a natural impulse 
 to relieve the itching of the ear. This should be done with the 
 tips of the fingers or not at all. 
 
 The popular notion that something should be put into the 
 ear to cure toothache is erroneous. This treatment does not 
 cure a toothache, and may lead to an injury to the delicate 
 parts of the ear. A piece of absorbent cotton, carefully inserted 
 into the ear, may be worn out of doors, when the cold air 
 causes pain, but should be removed on coming into the house. 
 
3 SO PRACTICAL PHYSIOLOGY. 
 
 Frequent bathing in the cold water of ponds and rivers is liable 
 to injure both the ears and the general health. In salt-water 
 bathing, the force of the waves striking against the ears often 
 leads to earache, long-continued inflammation, or defective 
 hearing ; to diminish this risk, insert into the ears a small 
 plug of absorbent cotton. 
 
 The ears are often carelessly exposed to cold water and 
 inclement weather. Very cold water should never be used to 
 bathe the ears and nostrils. Bathe moderately and gently in 
 lukewarm water, using a wash-rag in preference to a sponge ; 
 dry gently and thoroughly. Children's ears are often rudely 
 washed, especially in the auditory canal. This is not at all 
 necessary to cleanliness, and may result in a local inflammation. 
 
 Never shout suddenly in a per- 
 son's ear. The ear is not prepared 
 for the shock, and deafness has 
 occasionally resulted. A sudden 
 explosion, the noise of a cannon, 
 may burst the drum-head, especially 
 FIG. 144. Section of Cochlea. if the Eustachian tube be closed 
 From A straight downwards is the direo at the time. During heavy can- 
 tion of the central column, to which nonading, soldiers are taught to 
 
 E points. B points to the projecting 
 
 ridge, almost dividing the canal of keep the mouth open to allow an 
 
 the tube into an upper compartment equal tension of air. 
 (D), and a lower (C). 
 
 Insects may gam entrance to 
 
 the ears and occasion annoyance, pain, and fright, perhaps 
 leading to vomiting, even to convulsions, with nervous children. 
 A lighted lamp held at the entrance of the ear will often induce 
 the offending insect to crawl out towards the light. A few 
 drops of warm water, sweet oil, or molasses, dropped into the 
 ear, will help remove the intruder. 
 
 When a discharge occurs from the ears, it is not best to 
 plug them with cotton wads. It only keeps in what should be 
 got rid of. Do not go to sleep with the head on a window 
 
THE SPECIAL SENSES. 35 1 
 
 sill or in any position, with the ears exposed to draughts of 
 cold or damp air. 
 
 No effort should be made to remove the ear wax unless it 
 accumulates unduly. The skin of the canal grows outward, 
 and the extra wax and dust will be naturally carried out, if let 
 alone. Never employ any of the many articles or " drops," 
 advertised to cure deafness. Neuralgic pain in the canal, 
 usually classed as earache, may be due to decayed or improp- 
 erly filled teeth. 
 
 Quinine, so generally used in its many preparations for 
 malaria, causes a peculiar ringing or buzzing in the ears. 
 This is a warning that it should be taken in smaller doses, or 
 perhaps stopped for a time. In some cases quinine may pro- 
 duce temporary deafness. 
 
 The practice of snuffing up cold water into the nostrils is 
 occasionally followed by an acute inflammation of the middle 
 ear, some of the water finding its way through the Eustachian 
 tube into this part of the organ of hearing. The nasal douche, 
 so often advised as a home remedy for nasal catarrh, should 
 be used only with great caution, and always in accordance with 
 detailed directions from a physician. 
 
 348. Effect of Tobacco upon the Hearing. The sense of 
 hearing is often injured by the use of tobacco. The irritating 
 smoke filling all the inner cavity of the mouth and throat, 
 readily finds its way up the Eustachian tube, dries the mem- 
 brane, and irritates or inflames the delicate mechanism of the 
 inner ear. Thus may be produced a variety of serious aural 
 disturbances, such as unnatural noises, whistling, and roaring, 
 followed oftentimes by a partial loss of hearing. 
 
 Hearing may be impaired by the use of alcoholic beverages. 
 Alcohol inflames the mucous membrane of the throat, then by 
 its nearness the lining of the Eustachian tube, and finally may 
 injure the delicate apparatus of the internal ear. 
 
352 PRACTICAL PHYSIOLOGY. 
 
 ADDITIONAL EXPERIMENTS. 
 
 Experiment 162. Use a small pair of wooden compasses, or an ordi- 
 nary pair of dividers with their points guarded by a small piece of cork. 
 Apply the points of the compasses lightly and simultaneously to different 
 parts of the body, and ascertain at what distance apart the points are felt 
 as two. The following is the order of sensibility : tip of tongue, tip of the 
 middle finger, palm, forehead, and back of hand. 
 
 Experiment 163. Test as in preceding experiment the skin of the arm, 
 beginning at the shoulder and passing downwards. Observe that the sensi- 
 bility is greater as one tests towards the fingers, and also in the transverse 
 than in the long axis of the limb. In all cases compare the results obtained 
 on both sides of the body. 
 
 Experiment 164. By means of a spray-producer, spray the back of the 
 hand with ether, and observe how the sensibility is abolished. 
 
 Experiment 165. Touch your forehead with your forefinger; the finger 
 appears to feel the contact, but on rubbing the forefinger rapidly over the 
 forehead, it is the latter which is interpreted as " feeling " the finger. 
 
 Experiment 166. Generally speaking, the sensation of touch is referred 
 to the cutaneous surfaces. In certain cases, however, it is referred even 
 beyond this. Holding firmly in one hand a cane or a pencil, touch an 
 object therewith ; the sensation is referred to the extremity of the cane or 
 pencil. 
 
 If, however, the cane or pencil be held loosely in one's hand, one experi- 
 ences two sensations: one corresponding to the object touched, and the 
 other due to the contact of the rod with the skin. The process of mastica- 
 tion affords a good example of the reference of sensations to and beyond 
 the periphery of the body. 
 
 Experiment 167. Prepare a strong solution of sulphate of quinine 
 with the aid of a little sulphuric acid to dissolve it (bitter), a five-per-cent 
 solution of sugar (sweet}, a ten-per-cent solution of common salt (saline], 
 and a one-per-cent solution of acetic acid (acid). Wipe the tongue dry, 
 and lay on its tip a crystal of sugar. It is not tasted until it is dissolved. 
 
 Experiment 168. Apply a crystal of sugar to the tip, and another to the 
 back of the tongue. The sweet taste is more pronounced at the tip. 
 
THE SPECIAL SENSES. 353 
 
 Experiment 169. Repeat the process with sulphate of quinine in solu- 
 tion. It is scarcely tasted on the tip, but is tasted immediately on the back 
 part of the tongue. Test where salines and acids are tasted most acutely. 
 
 Experiment 170. To illustrate the muscular sense. Take two equal 
 iron or lead weights ; heat one and leave the other cold. The cold weight 
 will feel the heavier. 
 
 Experiment 171. Place a thin disk of cold lead, the size of a silver 
 dollar, on the forehead of a person whose eyes are closed ; remove the disk, 
 and on the same spot place two warm disks of equal size. The person will 
 judge the latter to be about the same weight, or lighter, than the single 
 cold disk. 
 
 Experiment 172. Compare two similar wooden disks, and let the di- 
 ameter of one be slightly greater than that of the other. Heat the smaller 
 one to over 120 F., and it will be judged heavier than the larger cold one. 
 
 Experiment 173. To illustrate the influence of excitation of one sense 
 organ on the other sense organs. Small colored patches the shape and color 
 of which are not distinctly visible may become so when a tuning-fork is 
 kept vibrating near the ears. In other individuals the visual impressions 
 are diminished by the same process. 
 
 On listening to the ticking of a watch, the ticking^sounds feebler or 
 louder on looking at a source of light through glasses of different colors. 
 
 If the finger be placed in cold or warm water the temperature appears 
 to rise when a red glass is held in front of the eyes. 
 
 Experiment 174. Formation of an in-verted image on the retina. Take 
 a freshly removed ox-eye ; dissect the sclerotic from that part of its poste- 
 rior segment near the optic nerve. Roll up a piece of blackened paper in 
 the form of a tube, black surface innermost, and place the eye in it with 
 the cornea directed forward. Look at an object e.g., a candle-flame 
 and observe the inverted image of the flame shining through the retina and 
 choroid, and notice how the image moves when the candle is moved. 
 
 Experiment 175. Focus a candle-flame or other object on the ground- 
 glass plate of an ordinary photographic camera, and observe the small 
 inverted image. 
 
 Experiment 176. To illustrate spherical aberration. Make a pin-hole 
 in a blackened piece of cardboard ; look at a light placed at a greater dis- 
 tance than the normal distance of accommodation. One will see a radiate 
 figure with four to eight radii. The figures obtained from opposite eyes 
 will probably differ in shape. 
 
354 PRACTICAL PHYSIOLOGY. 
 
 Experiment 177. Hold a thin wooden rod or pencil about a foot from 
 the eyes and look at a distant object. Note that the object appears double. 
 Close the right eye; the left image disappears, and vice versa. 
 
 Experiment 178. To show the movements of the iris. It is an extremely 
 beautiful experiment, and one that can easily be made. Look through a 
 pin-hole in a card at a uniform white surface as the white shade of an 
 ordinary reading-lamp. With the right eye look through the pin-hole, 
 the left eye being closed. Note the size of the (slightly dull) circular visual 
 field. Open the left eye, the field becomes brighter and smaller (con- 
 traction of pupil) ; close the left eye, after an appreciable time, the field 
 (now slightly dull) is seen gradually to expand. One can thus see and 
 observe the rate of movements of his own iris. 
 
 Experiment 179. To show the blind spot. The left eye being shut, let 
 the right eye be fixed upon the cross as in Fig. 145. When the book is 
 
 FIG. 145. 
 
 held at arm's length, both cross and round spot will be visible ; but if the 
 book be brought to about 8 inches from the eye, the gaze being kept 
 steadily upon the cross, the round spot will at first disappear, but as the 
 book is brought still nearer both cross and round spot will again be seen. 
 
 Experiment 180. To illustrate the duration of retinal impressions. On a 
 circular white disk, about halfway between the center and circumference, 
 
 fix a small, black, oblong disk, and rapidly 
 rotate it by means of a rotating wheel. 
 There appears a ring of gray on the black, 
 showing that the impression on the retina 
 lasts a certain time. 
 
 A B Experiment x8x. Mark off a round 
 
 FIG. 146. Optic Disks. piece of cardboard into black and white 
 
 sectors as in A (Fig. 146). Attach it so as 
 The disk A, having black and white 
 
 sectors, when rotated rapidly gives to rotate * rapidly, as on a sewing machine, 
 an even gray tint as in B. An even gray tint will be produced as in B. 
 
 Experiment 182. To illustrate imperfect visual judgments. Make three 
 round black dots, A, B, C, of the same size, in the same line, and let A and 
 
THE SPECIAL SENSES. 
 
 355 
 
 C be equidistant from B. Between A and B make several more dots of the 
 same size. A and B will then appear to be farther apart than B and C. 
 
 For the same reason, of two squares absolutely identical in size, one 
 marked with alternately clear and dark cross-bands, and the other with 
 alternately clear and dark upright markings, the former will appear broader 
 and the latter higher than the other. 
 
 Experiment 183. Make on a white card two squares of equal size. 
 Across the one draw horizontal lines at equal distances, and in the other 
 make similar vertical lines. Hold them at some distance. The one with 
 horizontal lines appears higher than it really is, while the one with vertical 
 lines appears broader, i.e., both appear oblong. 
 
 Experiment 184. Look at the row of letters (S) and figures (8). To 
 SSSSSSSS 88888888 
 
 some the upper halves of the letters and figures may appear to be of the 
 same size as the lower halves, to others the lower halves may appear larger. 
 Hold the figure upside down, and observe 
 that there is a considerable difference be- 
 tween the two, the lower halves being consider- 
 ably larger. 
 
 B 
 
 Experiment 185. To illustrate imperfect 
 visual judgment. The length of a line appears 
 to vary according to the angle and direction 
 of certain other lines in relation to it (Fig. 
 147). The length of the two vertical lines is 
 the same, yet B appears much longer than A. 
 
 Experiment 186. In indirect vision the 
 appreciation of direction is still more imperfect. 
 While leaning on a large table, fix a point on 
 the table, and then try to arrange three small pieces of colored paper in a 
 straight line. Invariably, the papers, being at a distance from the fixation- 
 point, and being seen by indirect vision, are arranged, not in a straight line, 
 but in the arc of a circle with a long radius. 
 
 FIG. 147. To show False 
 Estimate of Size. 
 
CHAPTER XII. 
 THE THROAT AND THE VOICE. 
 
 349. The Throat. The throat is a double highway, as it 
 were, through which the air we breathe traverses the larynx on 
 its way to the lungs, and through which the food we swallow 
 reaches the oesophagus on its passage to the stomach. It is, 
 therefore, a very important region of the body, being con- 
 cerned in the great acts of respiration and digestion. 
 
 The throat is enclosed and protected by various muscles 
 and bony structures, along which run the great blood-vessels 
 that supply the head, and the great nerve trunks that pass 
 from the brain to the parts below. 
 
 We have already described the food passages (Chapter VI.) 
 and the air passages (Chapter VIII.). 
 
 To get a correct idea of the throat we should look into the 
 wide-open mouth of some friend. Depressing the tongue 
 we can readily see the back wall of the pharynx, which is 
 common to the two main avenues leading to the lungs and the 
 stomach. Above, we notice the air passages, which lead to 
 the posterior cavities of the nose. We have already described 
 the hard palate, the soft palate, the uvula, and the tonsils 
 (Fig. 46). 
 
 On looking directly beyond these organs, we see the begin- 
 ning of the downward passage, the pharynx. If now the 
 tongue be forcibly drawn forward, a curved ridge may be seen 
 behind it. This is the epiglottis, which, as we have already 
 learned shuts down, like the lid of a box, over the top of the 
 larynx (sees. 137 and 203). 
 
 The throat is lined with mucous membrane covered with ciliated 
 epithelium, which secretes a lubricating fluid which keeps the 
 
THE THROAT AND THE VOICE. 
 
 357 
 
 parts moist and pliable. An excess of this secretion forms a 
 thick, tenacious mass of mucus, which irritates the passages and 
 gives rise to efforts of hawking and coughing to get rid of it. 
 
 350. The Larynx. The larynx, the essential organ of 
 voice, forms the box-like top of the windpipe. It is built of 
 variously shaped cartilages, connected 
 by ligaments. It is clothed on the 
 outside with muscles ; on the inside 
 it is lined with mucous membrane, 
 continuous with that of the other air 
 passages. 
 
 The larynx has for a framework 
 two cartilages, the thyroid and the 
 cricoid, one above the other. The 
 larger of these, called the thyroid, 
 from a supposed resemblance to a 
 shield, consists of two extended wings 
 which join in front, but are separated 
 by a wide interval behind. The united 
 edges in front project and form the 
 " Adam's apple," plainly seen and 
 
 easily felt On mOSt people, especially A,hyoidbone; B, thyro-hyoid mem- 
 brane; C, thyroid cartilage; D, 
 crico-thyroid membrane ; E, cri- 
 coid cartilage, lateral ligaments 
 ... 1111 seen on each side ; F, upper ring 
 
 horns which are connected by bands 
 to the hyoid bone, from which the 
 larynx is suspended. This bone is 
 attached by muscles and ligaments to the skull. It lies at 
 the base of the tongue, and can be readily felt by the finger 
 behind the chin at the angle of the jaw and the neck (sec. 41 
 and Fig. 46). From the under side of the thyroid two horns 
 project downwards to become jointed to the cricoid. The 
 thyroid thus rests upon, and is movable on, the cricoid cartilage. 
 
 on very lean men. 
 
 Above and from the sides rise two 
 
 FIG. 148. View of the Carti- 
 lages and Ligaments of the 
 Larynx. (Anterior view.) 
 
 of the trachea. ("Adam's apple " 
 is in the V-shaped groove on a 
 line with B and C.) 
 
358 
 
 PRACTICAL PHYSIOLOGY. 
 
 The cricoid cartilage, so called from its fancied resemblance 
 to a signet-ring, is smaller but thicker and stronger than the 
 thyroid, and forms the lower and back part of the cavity of 
 the larynx. This cartilage is quite sensitive to pressure from 
 the fingers, and is the cause of the sharp pain felt when we 
 
 try to swallow a large and hard piece 
 of food not properly chewed. 
 
 On the upper edge of the cricoid 
 cartilage are perched a pair of very 
 singular cartilages, pyramidal in 
 shape, called the arytenoid, which 
 are of great importance in the pro- 
 duction of the voice. These carti- 
 lages are capped with little horn-like 
 projections, and give attachment at 
 their anterior angles to the true 
 vocal cords, and at their posterior 
 angles to the muscles which open 
 and close the glottis, or upper open- 
 ing of the windpipe. When in their 
 natural position the arytenoid carti- 
 FIG. 149.- Diagram of a Sectional lages rese mble somewhat the mouth 
 
 View of Nasal and Throat Pas- r & . . 
 
 of a pitcher, hence their name. 
 
 sages. 
 
 C, nasal cavities; T, tongue ; L, lower 
 jaw; M, mouth; U, uvula; E, epi- 
 glottis ; G, larynx; O, resophagus. 
 
 351. The Vocal Cords. The 
 
 mucous membrane which lines the 
 various cartilages of the larynx is thrown into several folds. 
 Thus, one fold, the free edge of which is formed of a band of 
 elastic fibers, passes horizontally outwards from each side 
 towards the middle line, at the level of the base of the aryte- 
 noid cartilages. These folds are called the true vocal cords, 
 by the movements of which the voice is produced. 
 
 Above them are other folds of mucous membrane called the 
 false vocal cords, which take no part in the production of the 
 
THE THROAT AND THE VOICE. 
 
 359 
 
 voice. The arrangement of the true vocal cords, projecting as 
 they do towards the middle line, reduces to a mere chink the 
 space between the part of the larynx above them and the part 
 below them. This constriction of the larynx is called the glottis. 
 
 352. The Mechanism of the Voice. The mechanism of 
 the voice may be more easily understood by a study of Fig. 150. 
 We have here the larynx, .viewed from behind, with all the soft 
 parts in connection with it. On looking down, the folds form- 
 ing the true vocal cords are seen 
 enclosing a V-shaped aperture (the 
 glottis), the narrow part being in front. 
 
 The form of this aperture may be 
 changed by the delicately coordinate 
 activities of the muscles of the larynx. 
 For instance, the vocal cords may be 
 brought so closely together that the 
 space becomes a mere slit. Air forced 
 through the slit will throw the edges 
 of the folds into vibration and a sound 
 will be produced. 
 
 The variations in the form of the 
 opening will determine the variations 
 in the sound. Now, if the various 
 muscles of the larynx be relaxed, the 
 opening of the glottis is wider. Thus 
 the air enters and leaves the larynx 
 during breathing, without throwing 
 the cords into vibration enough to 
 produce any sound. 
 
 We may say that the production of the voice is effected by 
 an arrangement like that of some musical instruments, the 
 sounds produced by the vibrations of the vocal cords being 
 modified by the tubes above and below. All musical sounds 
 
 FIG. 150. View of the Carti- 
 lages and Ligaments of the 
 Larynx. (Posterior view.) 
 
 A, epiglottis ; B, thyroid cartilage: 
 C, arytenoid cartilage; D, liga- 
 ment connecting lower cornu of 
 the thyroid with the back of the 
 cricoid cartilage ; E, cricoid carti- 
 lage ; F, upper ring of the trachea. 
 
360 
 
 PRACTICAL PHYSIOLOGY. 
 
 are due to movements or vibrations occurring with a certain 
 regularity, and they differ in loudness, pitch, and quality. 
 Loudness of the sound depends upon the extent of the vibra- 
 tions, pitch on the rapidity of the vibrations, and quality on 
 the admixture of tones produced by 
 vibrations of varying rates of rapidity, 
 related to one another. 
 
 353. Factors in the Production of 
 the Voice. Muscles which pass from 
 the cricoid cartilage to the outer angle 
 of the arytenoids act to bring the vocal 
 cords close together, and parallel to one 
 another, so that the space between them 
 is narrowed to a slit. A strong expira- 
 tion now drives the air from the lungs 
 through the slit, between the cords, and 
 throws them into vibration. The vibra- 
 tion is small in amount, but very rapid. 
 Other muscles are connected with the 
 arytenoid cartilages which serve to sep- 
 
 FIG. 151. Longitudinal .. . 
 
 Section of the Larynx. arate the VOCal Cords and to P en Wldel y 
 
 (Showing the vocal cords.) the glottis. The force of the outgoing 
 
 A, epiglottis ; B, section of hyoid current of air determines the extent of 
 
 bone; c, superior vocal cord ; the move m e nt of the cords, and thus the 
 
 D, ventricle of the larynx ; E, 
 
 inferior vocal cord; F, section loudttCSS of the SOUnd will increase with 
 
 of the thyroid cartilage; H, g reater f orce Q f expiration. 
 
 section of anterior portion of 
 
 the cricoid cartilage ; K, tra- We have just learned that the pitch 
 chea; L, section of the poste- of sound depends on the rapidity of 
 
 nor portion of the cncoid , . . . 
 
 cartilage; M, arytenoid carti- the Vibrations. This depends Upon the 
 
 lage; N , section of the aryte- J en th Q f the CQrds and their tightness, 
 noid muscle. 
 
 for the shorter and tighter a string is, 
 
 the higher is the note which its vibration produces. The 
 vocal cords of women are about one-third shorter than those 
 
THE THROAT AND THE VOICE. 361 
 
 of men, hence the higher pitch of the notes they produce. 
 In children the vocal cords are shorter than in adults. 1 The 
 cords of tenor singers are also shorter than those of basses and 
 baritones. The muscles within the larynx, of course, play a 
 very important part in altering the tension of the vocal cords. 
 Those qualities of the voice which we speak of as sweet, harsh, 
 and sympathetic depend to a great extent upon the peculiar 
 structure of the vocal cords of the individual. 
 
 Besides the physical condition of the vocal cords, as their 
 degree of smoothness, elasticity, thickness, and so on, other 
 factors determine the quality of an individual's voice. Thus, 
 the general shape and structure of the trachea, the larynx, the 
 throat, and mouth all influence the quality of voice. In fact, 
 the air passages, both below and above the vibrating cords, 
 act as resonators, or resounding chambers, and intensify and 
 modify the sounds produced by the cords. It is this fact that 
 prompts skillful teachers of music and elocution to urge upon 
 their pupils the necessity of the mouth being properly opened 
 during speech, and especially during singing. 
 
 Experiment 187. To show the anatomy of the throat. Study the general 
 construction of the throat by the help of a hand mirror. Repeat the same 
 on the throat of some friend. 
 
 Experiment 188. To show the construction of the vocal organs. Get a 
 butcher to furnish two windpipes from a sheep or a calf. They differ 
 somewhat from the vocal organs of the human body, but will enable us to 
 recognize the different parts which have been described, and thus to get a 
 good idea of the gross anatomy. 
 
 One specimen should be cut open lengthwise in the middle line in front, 
 and the other cut in the same way from behind. 
 
 354. Speech. Speech is to be distinguished from voice. 
 It may exist without voice, as in a whisper. Speech consists 
 
 1 The voices of boys " break," or " change," because of the sudden growth or 
 enlargement of the larynx, and consequent increase in length of the vocal cords, at 
 from fourteen to sixteen years of age. No such enlargement takes place in the 
 larynxes of girls : therefore their voices undergo no such sudden change. 
 
362 PRACTICAL PHYSIOLOGY. 
 
 of articulated sounds, produced by the action of various parts 
 of the mouth, throat, and nose. Voice is common to most 
 animals, but speech is the peculiar privilege of man. 
 
 The organ of speech is perhaps the most delicate and perfect 
 motor apparatus in the whole body. It has been calculated 
 that upwards of 900 movements per minute 
 can be made by the movable organs of 
 speech during reading, speaking, and sing- 
 ing. It is said that no less than a hundred 
 different muscles are called into action in 
 talking. Each part of this delicate apparatus 
 is so admirably adjusted to every other that 
 FIG. 152. Diagram- all parts of this most complex machinery 
 matic Horizontal act in perfect harmony. 
 
 Section of Larynx to There ^ & ^^ articulate sounds called 
 show the Direction 
 
 of Pull of the Pos- vowel or vocal, from the fact that they are 
 terior Crico-Aryte- produced by the vocal cords, and are but 
 
 SSJSETvtS sli s htl y modified as the y p ass out of the 
 
 Cords. (Dotted lines mouth. The true vowels, a, <?, i, o j u, can 
 
 show position in ab- a n be sounded alone, and may be prolonged 
 
 in expiration. These are the sounds chiefly 
 
 used in singing. The differences in their characters are 
 
 produced by changes in the position of the tongue, mouth, 
 
 and lips. 
 
 Consonants are sounds produced by interruptions of the out- 
 going current of air, but in some cases have no sound in them- 
 selves, and serve merely to modify vowel sounds. Thus, when 
 the interruption to the outgoing current takes place by move- 
 ments of the lips, we have the labial consonants, /, b, f, and v. 
 When the tongue, in relation with the teeth or hard palate, 
 obstructs the air, the dental consonants, d, t, /, and s are pro- 
 duced. Gutturals, such as k, g, ch, gh, and r, are due to the 
 movements of the root of the tongue in connection with the 
 soft palate or pharynx. 
 
THE THROAT AND THE VOICE. 363 
 
 To secure an easy and proper production of articulate sounds, 
 the mouth, teeth, lips, tongue, and palate should be in perfect 
 order. The modifications in articulation occasioned by a de- 
 fect in the palate, or in the uvula, by the loss of teeth, from 
 disease, and from congenital defects, are sufficiently familiar. 
 We have seen that speech consists essentially in a modification 
 of the vocal sounds by the accessory organs, or by parts above 
 the larynx, the latter being the essential vocal instrument. 
 
 Many animals have the power of making articulated sounds ; 
 a few have risen, like man, to the dignity of sentences, but 
 these are only by imitation of the human voice. Both vowels 
 and consonants can be distinguished in the notes of birds, the 
 vocal powers of which are generally higher than those of mam- 
 mals. The latter, as a rule, produce only 
 vowels, though some are also able to form 
 consonants. 
 
 Persons idiotic from birth are incapable 
 of producing any other vocal sounds than 
 inarticulate cries, although supplied with all 
 the internal means of articulation. Persons 
 deaf and dumb are in the same situation, FIG. 153. Direction 
 though from a different cause; the one being of Pull of the Lateral 
 
 , . .'* i ^i i i Crico-Arytenoids, 
 
 incapable of imitating, and the other being which adduct the 
 deprived of hearing the sounds to be imitated. Vocal Cords. (Dot- 
 In whispering, the larynx takes scarcely ted lines show P OS1 " 
 
 , , f , tion in adduction.) 
 
 any part in the production or the sounds ; 
 the vocal cords remain apart and comparatively slack, and the 
 expiratory blast rushes through without setting them in vibration. 
 In stammering, spasmodic contraction of the diaphragm 
 interrupts the effort of expiration. The stammerer has full 
 control of the mechanism of articulation, but not of the expi- 
 ratory blast. His larynx and his lips are at his command, but 
 not his diaphragm. To conquer this defect he must train his 
 muscles of respiration to calm and steady action during speech. 
 
364 PRACTICAL PHYSIOLOGY. 
 
 The stutterer, on the other hand, has full control of the muscles 
 of expiration. His diaphragm is well drilled, but his lips and 
 tongue are insubordinate. 
 
 355. The Care of the Throat and Voice. The throat, 
 exposed as it is to unwholesome and overheated air, irritating 
 dust of the street, factories, and workshops, is often inflamed, 
 resulting in that common ailment, sore throat. The parts are 
 red, swollen, and quite painful on swallowing. Speech is often 
 indistinct, but there is no hoarseness or cough unless the uvula 
 is lengthened and tickles the back part of the tongue. Slight 
 sore throat rarely requires any special treatment, aside from 
 simple nursing. 
 
 The most frequent cause of throat trouble is the action of 
 cold upon the heated body, especially during active perspira- 
 tion. For this reason a cold bath should not be taken while a 
 person is perspiring freely. The muscles of the throat are 
 frequently overstrained by loud talking, screaming, shouting, 
 or by reading aloud too much. People who strain or misuse 
 the voice often suffer from what is called " clergyman's sore 
 throat." Attacks of sore throat due to improper methods of 
 breathing and of using the voice should be treated by judicious 
 elocutionary exercises and a system of vocal gymnastics, under 
 the direction of proper teachers. 
 
 Persons subject to throat disease should take special care to 
 wear suitable underclothing, adapted to the changes of the 
 seasons. Frequent baths are excellent tonics to the skin, and 
 serve indirectly to protect one liable to throat ailments from 
 changes in the weather. It is not prudent to muffle the neck 
 in scarfs, furs, and wraps, unless perhaps during an unusual 
 exposure to cold. Such a dress for the neck only makes the 
 parts tender, and increases the liability to a sore throat. 
 
 Every teacher of elocution or of vocal music, entrusted with 
 the training of a voice of some value to its possessor, should 
 
THE THROAT AND THE VOICE. 365 
 
 have a good, practical knowledge of the mechanism of the 
 voice. Good voices are often injured by injudicious manage- 
 ment on the part of some incompetent instructor. It is always 
 prudent to cease speaking or singing in public the moment 
 there is any hoarseness or sore throat. 
 
 , The voice should not be exercised just after a full meal, for 
 a full stomach interferes with the free play of the diaphragm. 
 A sip of water taken at convenient intervals, and held in the 
 mouth for a moment or two, will relieve the dryness of the 
 throat during the use of the voice. 
 
 356. Effect of Alcohol upon the Throat and Voice. Alco- 
 holic beverages seriously injure the throat, and consequently 
 the voice, by causing a chronic inflammation of the membrane 
 lining the larynx and the vocal cords. The color is changed 
 from the healthful pink to red, and the natural smooth surface 
 becomes roughened and swollen, and secretes a tough phlegm. 
 
 The vocal cords usually suffer from this condition. They 
 are thickened, roughened, and enfeebled, the delicate vibration 
 of the cords is impaired, the clearness and purity of the vocal 
 tones are gone, and instead the voice has become rough and 
 husky. So well known is this result that vocalists, whose 
 fortune is the purity and compass of their tones, are scrupu- 
 lously careful not to impair these fine qualities by convivial 
 indulgences. 
 
 357. Effect of Tobacco upon the Throat and Voice. The 
 
 effect of tobacco is often specially serious upon the throat, pro- 
 ducing a disease well known to physicians as " the smoker's 
 sore throat." Still further, it produces inflammation of the 
 larynx, and thus entails disorders of the vocal cords, involving 
 rough voice and harsh tones. For this reason vocalists rarely 
 allow themselves to come under the narcotic influence of 
 tobacco smoke. It is stated that habitual smokers rarely have 
 a normal condition of the throat. 
 
366 PRACTICAL PHYSIOLOGY. 
 
 ADDITIONAL EXPERIMENTS. 
 
 Experiment 189. To illustrate the importance of the resonating cavity 
 of the nose in articulation. Pinch the nostrils, and try to pronounce slowly 
 the words " Lincoln," " something," or any other words which require the 
 sound of m, In, or ng. 
 
 Experiment 190. To illustrate the passage of air through the glottis. 
 Take two strips of India rubber, and stretch them over the open end of a 
 boy's "bean-blower," or any kind of a tube. Tie them tightly 
 with thread, so that a chink will be left between them, as shown 
 in Fig. 1 54. 
 
 Force the air through such a tube by blowing hard, and if 
 the strips are not too far apart a sound will be produced. The 
 sound will vary in character, just as the bands are made tight 
 or loose. 
 
 Experiment 191. "A very good illustration of the action of 
 the vocal bands in the production of the voice may be given by 
 FIG i<u means f a piece of bamboo or any hollow wooden tube, and a 
 strip of rubber, about an inch or an inch and a half wide, cut 
 from the pure sheet rubber used by dentists. 
 
 " One end of the tube is to be cut sloping in two directions, and the strip 
 of sheet rubber is then to be wrapped round the tube, so as to leave a nar- 
 row slit terminating at the upper corners of the tube. 
 
 " By blowing into the other end of the tube the edges of the rubber 
 bands will be set in vibration, and by touching the vibrating membrane at 
 different points so as to check its movements it may be shown that the 
 pitch of the note emitted depends upon the length and breadth of the 
 vibrating portion of the vocal bands. " * DR. H. P. BOWDITCH. 
 
 1 This experiment and several others in this book, are taken from Professor 
 Bowditch's little book called Hints for Teachers of Physiology, a work which 
 should be mastered by every teacher of physiology in higher schools. 
 
 NOTE. The limitations of a text-book on physiology for schools do not permit 
 so full a description of the voice as the subject deserves. For additional details, the 
 student is referred to Cohen's The Throat and the Voice, a volume in the " Ameri. 
 can Health Primer Series." Price 40 cents. 
 
CHAPTER XIII. 
 
 ACCIDENTS AND EMERGENCIES. 
 
 358. Prompt Aid to the Injured. A large proportion of 
 the accidents, emergencies, and sudden sicknesses that happen 
 do not call for medical or surgical attention. For those that do 
 require the services of a physician or surgeon, much can be 
 often done before the arrival of professional help. Many a 
 life has been saved and much suffering and anxiety prevented 
 by the prompt and efficient help of some person with a cool 
 head, a steady hand, and a practical knowledge of what to do 
 first. Many of us can recall with mingled admiration and grati- 
 tude the prompt services rendered our families by some neigh- 
 bor or friend in the presence of an emergency or sudden illness. 
 
 In fact, what we have studied in the preceding chapters 
 becomes tenfold more interesting, instructive, and of value to 
 us, if we are able to supplement such study with its practical 
 application to the treatment of the more common and less seri- 
 ous accidents and emergencies. 
 
 While no book can teach one to have presence of mind, a 
 cool head, or to restrain a more or less excitable temperament 
 in the midst of sudden danger, yet assuredly with proper knowl- 
 edge for a foundation, a certain self-confidence may be acquired 
 which will do much to prevent hasty action, and to maintain a 
 useful amount of self-control. 
 
 Space allows us to describe briefly in this chapter only a few 
 of the simplest helps in the more common accidents and emer- 
 gencies which are met with in everyday life. 1 
 
 1 The teacher or student who is disposed to study the subject more thor- 
 oughly and in more detail than is possible in a class text-book, will find all that is 
 needed in the following excellent books, which are readily obtained by purchase, or 
 
368 
 
 PRACTICAL PHYSIOLOGY. 
 
 359. Hints as to what to Do First. Retain so far as pos- 
 sible your presence of mind, or, in other words, keep cool. 
 This is an all-important direction. Act promptly and quietly, 
 but not with haste. Whatever you do, do in earnest; and 
 never act in a half-hearted manner in the presence of danger. 
 Of course, a knowledge of what to do and how to do it will 
 contribute much towards that self-control and confidence that 
 command success. Be sure and send for a doctor at once if 
 
 the emergency calls for skilled 
 service. All that is expected of 
 you under such circumstances is to 
 tide over matters until the doctor 
 comes. 
 
 Do not presume upon any smat- 
 tering of knowledge you have, to 
 assume any risk that might lead to 
 serious results. Make the sufferer 
 comfortable by giving him an abun- 
 dance of fresh air and placing him 
 in a restful position. Do all that is 
 possible to keep back the crowd of 
 FIG. 155- -Showing how Digital curious l oo kers-on, whom a morbid 
 
 Compression should be applied 
 
 to the Brachial Artery. curiosity has gathered about the 
 
 injured person. Loosen all tight 
 
 articles of clothing, as belts, collars, corsets, and elastics. 
 Avoid the use of alcoholic liquors. They are rarely of any 
 real service, and in many instances, as in bleeding, may do 
 much harm. 
 
 360. Incised and Lacerated Wounds. An incised or cut 
 wound is one made by a sharp instrument, as when the finger 
 
 may be found in the public libraries of larger towns : Dulles' Accidents and Emer- 
 gencies ; Pilcher's First Aid in Illness and Injury ; Doty's Prompt Aid to the 
 Injured ; and Johnston's " Surgical Injuries and Surgical Diseases," a special article 
 in Roosevelt's In Sickness and in Health. 
 
ACCIDENTS AND EMERGENCIES. 369 
 
 is cut with a knife. Such a wound bleeds freely because the 
 clean-cut edges do not favor the clotting of blood. In slight 
 cuts the bleeding readily ceases, and the wound heals by pri- 
 mary union, or by " first intention," as surgeons call it. 
 
 Lacerated and contused wounds are made by a tearing or 
 bruising instrument, for example, catching the finger on a nail. 
 Such wounds bleed but little, and the edges and surfaces are 
 rough and ragged. 
 
 If the incised wound is deep or extensive, a physician is 
 necessary to bring the cut edges together by stitches in order 
 to get primary union. Oftentimes, in severe cuts, and generally 
 in lacerations, there is a loss of tissue, so that the wound heals 
 by " second intention " ; that is, the wound heals from the 
 bottom by a deposit of new cells called granulations, which 
 gradually fill it up. The skin begins to grow from the edges 
 to the center, covering the new tissue and leaving a cicatrix 
 or scar with which every one is familiar. 
 
 361. Contusion and Bruises. An injury to the soft tissues, 
 caused by a blow from some blunt instrument, or a fall, is a 
 contusion, or bruise. It is more or less painful, followed by 
 discoloration due to the escape of blood under the skin, which 
 often may not be torn through. A black eye, a knee injured 
 by a fall from a bicycle, and a finger hurt by a baseball, are 
 familiar examples of this sort of injury. Such injuries ordi- 
 narily require very simple treatment. 
 
 The blood which has escaped from the capillaries is slowly 
 absorbed, changing color in the process, from blue black to 
 green, and fading into a light yellow. Wring out old towels or 
 pieces of flannel in hot water, and apply to the parts, changing 
 as they become cool. For cold applications, cloths wet with 
 equal parts of water and alcohol, vinegar, and witch-hazel may 
 be used. Even if the injury is apparently slight it is always 
 safe to rest the parts for a few days. 
 
370 
 
 PRACTICAL PHYSIOLOGY. 
 
 When wounds are made with ragged edges, such as those 
 made by broken glass and splinters, more skill is called for. 
 Remove every bit of foreign substance. Wash the parts 
 clean with one of the many antiseptic solutions, bring the torn 
 edges together, and hold them in place with strips of plaster. 
 Do not cover such an injury all over with plaster, but leave 
 room for the escape of the wound discharges. For an outside 
 ^^^ dressing, use compresses made of 
 
 J^\ clean cheese-cloth or strips of any 
 
 clean linen cloth. The antiseptic 
 corrosive-sublimate gauze on sale at 
 any drug store should be used if it 
 can be had. 
 
 Wounds made by toy pistols, per- 
 cussion-caps, and rusty nails and 
 tools, if neglected, often lead to 
 serious results from blood-poisoning. 
 A hot flaxseed poultice may be needed 
 for several days. Keep such wounds 
 clean by washing or syringing them 
 twice a day with hot antiseptics, which 
 are poisons to bacteria and kill them 
 
 Bacteria 
 
 are widely distributed, and hence the 
 utmost care should be taken to have 
 everything which is to come in contact with a wounded surface 
 free from the germs of inflammation. In brief, such injuries 
 must be. kept scrupulously neat and surgically clean. 
 
 The injured parts should be kept at rest. Movement and 
 disturbance hinder the healing process. 
 
 362. Bites of Mad Dogs. Remove the clothing at once, if 
 only from the bitten part, and apply a temporary ligature above 
 the wound. This interrupts the activity of the circulation of 
 
 FIG. 1 56. Dotted Line showing O r prevent their growth. 
 
 the Course of the Brachial 
 Artery. 
 
ACCIDENTS AND EMERGENCIES. 
 
 the part, and to that extent delays the absorption of the poison- 
 ous saliva by the blood-vessels of the wound. A dog bite is 
 really a lacerated and contused wound, and lying in the little 
 roughnesses, and between the shreds, is the poisonous saliva. 
 If by any means these projections and depressions affordingthe 
 lodgment can be removed, the poison cannot do much harm. If 
 done with a knife, the wound would be converted, practically, 
 into an incised wound, and would require treatment for such. 
 
 If a surgeon is at hand he would probably cut out the injured 
 portion, or cauterize it thoroughly. Professional aid is not 
 always at our command, and in such a case it would be well 
 to take a poker, or other suitable piece of iron, heat it red hot 
 in the fire, wipe off and destroy the entire surface of the wound. 
 As fast as destroyed, the tissue becomes white. An iron, even 
 at a white heat, gives less pain and at once destroys the vitality 
 of the part with which it comes in contact. 
 
 If the wound is at once well wiped out, and a stick of solid 
 nitrate of silver (lunar caustic) rapidly applied to the entire 
 surface of the wound, little danger is to be apprehended. 
 Poultices and warm fomentations should be applied to the 
 injury to hasten the sloughing away of the part whose vitality 
 has been intentionally destroyed. 
 
 Any dog, after having bitten a person, is apt, under a mis- 
 taken belief, to be at once killed. This should not be done. 
 There is no more danger from a dog-bite, unless the dog is 
 suffering from the disease called rabies or is "mad," than from 
 any other lacerated wound. The suspected animal should be 
 at once placed in confinement and watched, under proper 
 safeguards, for the appearance of any symptoms that indicate 
 rabies. 
 
 Should no pronounced symptoms indicate this disease in the 
 dog, a great deal of unnecessary mental distress and worry 
 can be saved both on the part of the person bitten and his 
 friends. 
 
372 
 
 PRACTICAL PHYSIOLOGY. 
 
 363. Injuries to the Blood-vessels. It is very important to 
 know the difference between the bleeding from an artery and 
 that from a vein. 
 
 If an artery bleeds, the blood leaps in spurts, and is of a 
 bright scarlet color. 
 
 If a vein bleeds, the blood flows in a steady stream, and is 
 of a dark purple color. 
 
 If the capillaries are injured the blood merely oozes. 
 Bleeding from an artery is a dangerous matter in proportion 
 to the size of the vessel, and life itself may be speedily lost. 
 
 Hemorrhage from a vein or 
 from the capillaries is rarely 
 troublesome, and is ordinarily 
 easily checked, aided, if need 
 be, by hot water, deep pres- 
 sure, the application of some 
 form of iron styptic, or even 
 powdered alum. When an 
 artery is bleeding, always re- 
 member to make deep pres- 
 sure between the wound and 
 the heart. In all such cases 
 send at once for the doctor. 
 
 Do not be afraiol to act at 
 once. A resolute grip in the 
 right place with firm fingers 
 will do well enough, until a twisted handkerchief, stout cord, 
 shoestring, suspender, or an improvised tourniquet 1 is ready 
 
 1 " A tourniquet is a.bandage, handkerchief, or strap of webbing, into the middle 
 of which a stone, a potato, a small block of wood, or any hard, smooth body is tied. 
 The band is tied loosely about the limb, the hard body is held over the artery to be 
 constricted, and a stick is inserted beneath the band on the opposite side of the limb 
 and used to twist the band in such a way that the limb is tightly constricted thereby, 
 and the hard body thus made to compress the artery (Fig. 160). 
 
 " The entire circumference of the limb may be constricted by any sort of elastic 
 
 FIG. 157. Showing how Digital Com- 
 pression should be applied to the Fem- 
 oral Artery. 
 
ACCIDENTS AND EMERGENCIES. 373 
 
 to take its place. If the flow of blood does not stop, change 
 the pressure until the right spot is found. 
 
 Sometimes it will do to seize a handful of dry earth and crowd 
 it down into the bleeding wound, with a firm pressure. Strips 
 of an old handkerchief, underclothing, or cotton wadding may 
 also be used as a compress, provided pressure is not neglected. 
 
 In the after-treatment it is of great importance that the 
 wound and the dressing should be kept free from bacteria by 
 keeping everything surgically clean. 
 
 364. Where and how to Apply Pressure. The principal 
 places in which to apply pressure when arteries are injured and 
 bleeding should always be kept in mind. 
 
 Experiment 192. How to tie a square knot. If the student would render 
 efficient help in accidents and emergencies, to say nothing of service on 
 scores of other occasions, he must learn how to 
 tie a square or " reef " knot. This knot is secure 
 and does not slip as does the " granny " knot. 
 The square knot is the one used by surgeons in 
 ligating vessels and securing bandages. Unless 
 one knew the difference, the insecure " granny " 
 knot might be substituted. 
 
 A square knot is tied by holding an end of a 
 bandage or cord in each hand, and then passing FlG 158> _ showing how ~ a 
 the end in the right hand over the one in the Square Knot may be tied 
 left and tying ; the end now in the left hand is w ith a Cord and a Hand- 
 passed over the one in the right and again tied. kerchief. 
 
 If in the finger, grasp it with the thumb and forefinger, and 
 pinch it firmly on each side ; if in the hand, press on the 
 bleeding spot, or press with the thumb just above and in front 
 of the wrist. 
 
 band or rubber tube, or any other strong elastic material passed around the limb 
 several times on a stretch, drawn tight and tied in a knot. In this way, bleeding may 
 be stopped at once from the largest arteries. The longer and softer the tube the 
 better. It requires no skill and but little knowledge of anatomy to apply it effi- 
 ciently," ALEXANDER B.JOHNSON, Surgeon to Roosevelt Hospital, New York City 
 
374 PRACTICAL PHYSIOLOGY. 
 
 For injuries below the elbow, grasp the upper part of the 
 arm with the hands, and squeeze hard. The main artery runs 
 in the middle line of the bend of the elbow. Tie the knotted cord 
 here, and bend the forearm so as to press hard against the knot. 
 
 For the upper arm, press with the fingers against the bone 
 on the inner side, and just on the edge of the swell of the 
 biceps muscle. Now we are ready for the knotted cord. Take 
 a stout stick of wood, about a foot long, and twist the cord hard 
 with it, bringing the knot firmly over the artery. 
 
 For the foot or leg, pressure as before, in the hollow behind 
 the knee, just above the calf of the leg. Bend the thigh towards 
 the abdomen and bring the leg up against the thigh, with the 
 knot in the bend of the knee. 
 
 365. Bleeding from the Stomach and Lungs. Blood that 
 comes from the lungs is bright red, frothy, or "soapy." There 
 is rarely much ; it usually follows coughing, feels warm, and 
 has a salty taste. This is a grave symptom. Perfect rest on 
 the back in bed and quiet must be insisted upon. Bits of ice 
 should be eaten freely. Loosen the clothing, keep the shoulders 
 well raised, and the body in a reclining position and absolutely 
 at rest. Do not give alcoholic drinks. 
 
 Blood from the stomach is not frothy, has a sour taste, and 
 is usually dark colored, looking somewhat like coffee grounds. 
 It is more in quantity than from the lungs, and is apt to be 
 mixed with food. Employ the same treatment, except that the 
 person should be kept flat on the back. 
 
 366. Bleeding from the Nose. This is the most frequent 
 and the least dangerous of the various forms of bleeding. Let 
 the patient sit upright ; leaning forward with the head low only 
 increases the hemorrhage. Raise the arm on the bleeding 
 side ; do not blow the nose. Wring two towels out of cold 
 water ; wrap one around the neck and the other properly folded 
 over the forehead and upper part of the nose. 
 
ACCIDENTS AND EMERGENCIES. 
 
 375 
 
 Add a teaspoonful of powdered alum to a cup of water, and 
 snuff it up from the hand. If necessary, soak in alum water a 
 piece of absorbent cotton, which has been wound around the 
 pointed end of a pencil or penholder ; plug the nostril by 
 pushing it up with a twisting motion until firmly lodged. 
 
 367. Burns or Scalds. Burns or scalds are dangerous in 
 proportion to their extent and depth. A child may have one 
 of his fingers burned off with less 
 danger to life than an extensive scald 
 of his back and legs. A deep or ex- 
 tensive burn or scald should always 
 have prompt medical attendance. 
 
 In burns by acids, bathe the parts 
 with an alkaline fluid, as diluted am- 
 monia, or strong soda in solution, and 
 afterwards dress the burn. 
 
 In burns caused by lime, caustic 
 potash, and other alkalies, soak the 
 parts with vinegar diluted with water; 
 lemon juice, or any other diluted acid. 
 
 Remove the clothing with the great- 
 est care. Do not pull, but carefully 
 cut and coax the clothes away from 
 the burned places. Save the skin un- 
 broken if possible, taking care not to 
 break the blisters. The secret of 
 treatment is to prevent friction, and to keep out the air. If 
 the burn is slight, put on strips of soft linen soaked in a 
 strong solution of baking-soda and water, one heaping table- 
 spoonful to a cupful of water. This is especially good for scalds. 
 
 Carron oil is one of the best applications. It is simply half 
 linseed-oil and half lime-water shaken together. A few table- 
 spoonfuls of carbolic acid solution to one pint may be added 
 
 FIG. 159. Dotted Line show- 
 ing the Course of the Fem- 
 oral Artery. 
 
376 
 
 PRACTICAL PHYSIOLOGY. 
 
 to this mixture to help deaden the pain. Soak strips of old 
 linen or absorbent cotton in this time-honored remedy, and 
 gently apply. 
 
 If carbolized or even plain vaseline is at hand, spread it 
 freely on strips of old linen, and cover well the burnt parts, 
 keeping out the air with other strips carefully laid on. Simple 
 
 cold water is better than 
 flour, starch, toilet pow- 
 der, cotton batting, and 
 other things which are 
 apt to stick, and make 
 an after-examination 
 very painful. 
 
 368. Frost Bites. 
 
 The ears, toes, nose, and 
 fingers are occasionally 
 frozen, or frost-bitten. 
 No warm air, warm 
 water, or fire should be 
 allowed near the frozen 
 parts until the natural 
 temperature is nearly re- 
 stored. Rub the frozen 
 part vigorously with snow 
 or snow-water in a cold 
 room. Continue this until a burning, tingling pain is felt, 
 when all active treatment should cease. 
 
 Pain shows that warmth and circulation are beginning to 
 return. The after effects of a frost bite are precisely like those 
 of a burn, and require similar treatment. Poultices made from 
 scraped raw potatoes afford much comfort for an after treatment. 
 
 369. Catching the Clothing on Fire. When the clothing 
 catches fire, throw the person down on the ground or floor, as 
 
 FIG. 160. Showing how Hemorrhage from the 
 Femoral Artery may be arrested by the Use of 
 an Improvised Apparatus (technically called a 
 Tourniquet}. 
 
ACCIDENTS AND EMERGENCIES. 3/7 
 
 the flames will tend less to rise toward the mouth and nostrils. 
 Then without a moment's delay, roll the person in a carpet 
 or hearth-rug, so as to stifle the flames, leaving only the head 
 out for breathing. 
 
 If no carpet or rug can be had, then take off your coat, shawl, 
 or cloak and use it instead. Keep the flame as much as possi- 
 ble from the face, so as to prevent the entrance of the hot air 
 into the lungs. This can be done by beginning at the neck 
 and shoulders with the wrapping. 
 
 370. Foreign Bodies in the Throat. Bits of food or other 
 small objects sometimes get lodged in the throat, and are easily 
 extracted by the forefinger, by sharp slaps on the back, or 
 expelled by vomiting. If it is a sliver from a toothpick, match, 
 or fishbone, it is no easy matter to remove it ; for it generally 
 sticks into the lining of the passage. If the object has actually 
 passed into the windpipe, and is followed by sudden fits of 
 spasmodic coughing, with a dusky hue to the face and fingers, 
 surgical help must be called without delay. 
 
 If a foreign body, like coins, pencils, keys, fruit-stones, etc., 
 is swallowed, it is not wise to give a physic. Give plenty of 
 hard-boiled eggs, cheese, and crackers, so that the intruding 
 substance may be enfolded in a mass of solid food and allowed 
 to pass off in the natural way. 
 
 371. Foreign Bodies in the Nose. Children are apt to 
 push beans, peas, fruit-stones, buttons, and other small objects, 
 into the nose. Sometimes we can get the child to help by 
 blowing the nose hard. At other times, a sharp blow between 
 the shoulders will cause the substance to fall out. If it is a 
 pea or bean, which is apt to swell with the warmth and mois- 
 ture, call in medical help at once. 
 
 372. Foreign Bodies in the Ear. It is a much more diffi- 
 cult matter to get foreign bodies out of the ear than from the 
 
PRACTICAL PHYSIOLOGY. 
 
 nose. Syringe in a little warm water, which will often wash 
 out the substance. If live insects get into the ear, drop in a 
 little sweet oil, melted vaseline, salt and water, or even warm 
 molasses. 
 
 If the tip of the ear is pulled up gently, the liquid will flow 
 in more readily. If a light is held close to the outside ear, the 
 insect may be coaxed to crawl out towards the outer opening 
 of the ear, being attracted by the bright flame. 
 
 373. Foreign Bodies in the Eye. Cinders, particles of 
 dust, and other small substances, often get into the eye, and 
 cause much pain. It will only make bad matters worse to rub 
 
 FIG. 161. Showing how the Upper Eyelid may be everted with a 
 Pencil or Penholder. 
 
 the eye. Often the copious flow of tears will wash the sub- 
 stance away. It is sometimes seen, and removed simply by 
 the twisted corner of a handkerchief carefully used. If it is 
 not removed, or even found, in this way, the upper lid must be 
 turned back. 
 
 This is done usually as follows : Seize the lashes between 
 the thumb and forefinger, and draw the edge of the lid away 
 from the eyeball. Now, telling the patient to look down, press 
 a slender lead-pencil or penholder against the lid, parallel to 
 and above the edge, and then pull the edge up, and turn it over 
 the pencil by means of the lashes. 
 
ACCIDENTS AND EMERGENCIES. 
 
 379 
 
 The eye is now readily examined, and usually the foreign 
 body is easily seen and removed. Do not increase the trouble 
 by rubbing the eye after you 
 fail, but get at once skilled 
 help. After the substance has 
 been removed, bathe the eye 
 for a time with hot water. 
 
 If lime gets into the eye, it may do a 
 great amount of mischief, and generally 
 requires medical advice, or permanent 
 injury will result. Until such advice 
 can be had, bathe the injured parts 
 freely with a weak solution of vinegar 
 and hot water. 
 
 374. Broken Bones. Loss of power, 
 pain, and swelling are symptoms of a 
 broken bone that may be easily recog- 
 nized. Broken limbs should always be 
 handled with great care and tenderness. 
 If the accident happens in the woods, 
 the limb should be bound with hand- 
 kerchiefs, suspenders, or strips of cloth- 
 ing, to a piece of board, pasteboard, or 
 bark, padded with moss or grass, which 
 will do well enough for a temporary 
 splint. Always put a broken arm into 
 a sling after the splints are on. 
 
 Never move the injured person until 
 the limb is made safe from further in- 
 juries by putting on temporary splints. 
 If you do not need to move the person, FlG> ^L- Showing how 
 
 an Umbrella may be used 
 
 keep the limb in a natural, easy position, as a Temporary Splint in 
 
 Until the doctor COmeS. Fracture of the Leg. 
 
3 So 
 
 PRACTICAL PHYSIOLOGY. 
 
 Remember that this treatment for broken bones is only to 
 enable the patient to be moved without further injury. A 
 surgeon is needed at once to set the broken bone. 
 
 375. Fainting. A fainting person should be laid flat at once. 
 Give plenty of fresh air, and dash cold water, if necessary, on 
 the head and neck. Loosen all tight 
 clothing. Smelling-salts may be held to 
 the nose, to excite the nerves of sensation. 
 
 376. Epileptic and Hysterical Fits, 
 Convulsions of Children. Sufferers 
 from " fits " are more or less common. 
 In epilepsy, the sufferer falls with a 
 peculiar cry ; a loss of consciousness, a 
 moment of rigidity, and violent convul- 
 sions follow. There is foaming at the 
 mouth, the eyes are rolled up, and the 
 tongue or lips are often bitten. When 
 the fit is over the patient remains in a 
 dazed, stupid state for some time. It is 
 a mistake to struggle with such patients, 
 
 FIG. 162. Showing how a or to hold tnem down and kee P them 
 
 quiet. It does more harm than good. 
 See that the person does not injure 
 
 himself ; crowd a pad made from a folded 
 handkerchief or towel between the teeth, to prevent biting of 
 the lips or tongue. Do not try to make the sufferer swallow 
 any drink. Unfasten the clothes, especially about the neck 
 and chest. Persons who are subject to such fits should rarely 
 go out alone, and never into crowded or excited gatherings of 
 any kind. 
 
 Hysterical fits almost always occur in young women. Such 
 patients never bite their tongue nor hurt themselves. Placing 
 a towel wrung out in cold water across the face, or dashing a 
 
 Pillow may be used as 
 a Temporary Splint in 
 Fracture of the Leg. 
 
ACCIDENTS AND EMERGENCIES. 381 
 
 little cold water on the face or neck, will usually cut short the 
 fit, speaking firmly to the patient at the same time. Never 
 sympathize too much with such patients ; it will only make 
 them a great deal worse. 
 
 377. Asphyxia. Asphyxia is from the Greek, and means 
 an " absence of pulse." This states a fact, but not the cause. 
 The word is now commonly used to mean suspended anima- 
 tion. When for any reason the proper supply of oxygen is 
 cut off, the tissues rapidly load up with carbon dioxid. The 
 blood turns dark, and does not circulate. The healthy red or 
 pink look of the lips and finger-nails becomes a dusky purple. 
 The person is suffering from a lack of oxygen ; that is, from 
 asphyxia, or suffocation. It is evident there can be several 
 varieties of asphyxia, as in apparent drowning, strangulation 
 and hanging, inhalation of gases, etc. 
 
 The first and essential thing to do is to give fresh air. 
 Remove the person to the open air and place him on his back. 
 Remove tight clothing about the throat and waist, dash on cold 
 water, give a few drops of ammonia in hot water or hot ginger 
 tea. Friction applied to the limbs should be kept up. If 
 necessary, use artificial respiration by the Sylvester method 
 (sec. 380). 
 
 The chief dangers from poisoning by noxious gases come 
 from the fumes of burning coal in the furnace, stove, or range ; 
 from " blowing out " gas, turning it down, and having it blown 
 out by a draught ; from the foul air often found in old wells ; 
 from the fumes of charcoal and the foul air of mines. 
 
 378. Apparent Drowning. Remove all tight clothing from 
 the neck, chest, and waist. Sweep the forefinger, covered with 
 a handkerchief or towel, round the mouth, to free it from froth 
 and mucus. Turn the body on the face, raising it a little, with 
 the hands under the hips, to allow any water to run out from 
 the air passages. Take only a moment for this. 
 
32 PRACTICAL PHYSIOLOGY. 
 
 Lay the person flat upon the back, with a folded coat, or pad 
 of any kind, to keep the shoulders raised a little. Remove all 
 the wet, clinging clothing that is convenient. If in a room or 
 sheltered place, strip the body, and wrap it in blankets, over- 
 coats, etc. If at hand, use bottles of hot water, hot flats, or 
 bags of hot sand round the limbs and feet. Watch the tongue : 
 it generally tends to slip back, and to shut off the air from the 
 glottis. Wrap a coarse towel round the tip of the tongue, and 
 keep it well pulled forward. 
 
 The main thing to do is to keep up artificial respiration until 
 the natural breathing comes, or all hope is lost. This is the 
 simplest way to do it : The person lies on the back ; let some 
 one kneel behind the head. Grasp both arms near the elbows, 
 and sweep them upward above the head until they nearly touch. 
 Make a firm pull for a moment. This tends to fill the lungs 
 with air by drawing the ribs up, and making the chest cavity 
 larger. Now return the arms to the sides of the body until 
 they press hard against the ribs. This tends to force out the 
 
 FIG. 163. The Sylvester Method. (First movement inspiration.) 
 
 air. This makes artificially a complete act of respiration. 
 Repeat this act about fifteen times every minute. 
 
 All this may be kept up for several hours. The first sign of 
 recovery is often seen in the slight pinkish tinge of the lips 
 or finger-nails. That the pulse cannot be felt at the wrist 
 is of little value in itself as a sign of death. Life may be 
 
ACCIDENTS AND EMERGENCIES. 383 
 
 present when only the most experienced ear can detect the 
 faintest heart-beat. 
 
 When a person can breathe, even a little, he can swallow. 
 Hold smelling-salts or hartshorn to the nose. Put one tea- 
 spoonful of the aromatic spirits of ammonia, or even of am- 
 monia water, into a half-glass of hot water, and give a few 
 teaspoonfuls of this mixture every few minutes. Meanwhile 
 do not fail to keep up artificial warmth in the most vigorous 
 manner. 
 
 379. Methods of Artificial Respiration. There are several well- 
 established methods of artificial respiration. The two known as the 
 Sylvester and the Marshall Hall methods are generally accepted as 
 efficient and practical. 
 
 FIG. 164. The Sylvester Method. (Second movement expiration.) 
 
 380. The Sylvester Method. The water and mucus are sup- 
 posed to have been removed from the interior of the body by the 
 means above described (sec. 378). 
 
 The patient is to be placed on his back, with a roll made of a coat 
 or a shawl under the shoulders ; the tongue should then be drawn 
 forward and retained by a handkerchief which is placed across the 
 extended organ and carried under the chin, then crossed and tied at 
 the back of the neck. An elastic band or small rubber tube or a 
 suspender may be used for the same purpose. 
 
384 PRACTICAL PHYSIOLOGY. 
 
 The attendant should kneel at the head and grasp the elbows of 
 the patient and draw them upward until the hands are carried above 
 the head and kept in this position until one, two, three, can be slowly 
 counted. This movement elevates the ribs, expands the chest, and 
 creates a vacuum in the lungs into which the air rushes, or in other 
 words, the movement produces inspiration. The elbows are then 
 slowly carried downward, placed by the side, and pressed inward 
 against the chest, thereby diminishing the size of the latter and pro- 
 ducing expiration. 
 
 These movements should be repeated about fifteen times each 
 minute for at least two hours, provided no signs of animation show 
 themselves. 
 
 381. The Marshall Hall Method. The patient should be placed 
 face downwards, the head resting on the forearm with a roll or pillow 
 placed under the chest ; he should then be turned on his side, an 
 
 FIG. 165. The Marshall Hall Method. (First position.) 
 
 assistant supporting the head and keeping the mouth open ; after an 
 interval of two or three seconds, the patient should again be placed 
 face downward and allowed to remain in this position the same length 
 of time. This operation should be repeated fifteen or sixteen times 
 each minute, and continued (unless the patient recovers) for at least 
 two hours. 
 
 If, after using one of the above methods, evidence of recovery 
 appears, such as an occasional gasp or muscular movement, the efforts 
 to produce artificial respiration must not be discontinued, but kept up 
 until respiration is fully established. All wet clothing should then be 
 removed, the patient rubbed dry, and if possible placed in bed, where 
 
ACCIDENTS AND EMERGENCIES. 385 
 
 warmth .and warm drinks can be properly administered. A small 
 amount of nourishment, in the form of hot milk or beef tea, should 
 be given, and the patient kept quiet for two or three days. 
 
 FIG. 166. The Marshall Hall Method. (Second position.) 
 
 382. Sunstroke or Heatstroke. This serious accident, so 
 far-reaching oftentimes in its result, is due to an unnatural 
 elevation of the bodily temperature by exposure to the direct 
 rays of the sun, or from the extreme heat of close and confined 
 rooms, as in the cook-rooms and laundries of hotel basements, 
 from overheated workshops, etc. 
 
 There is sudden loss of consciousness, with deep, labored 
 breathing, an intense burning heat of the skin, and a marked 
 absence of sweat. The main thing is to lower the temperature. 
 Strip off the clothing ; apply chopped ice, wrapped in flannel to 
 the head. Rub ice over the chest, and place pieces under the 
 armpits and at the sides. If there is no ice, use sheets or 
 cloths wet with cold water. The body may be stripped, and 
 sprinkled with ice-water from a common watering-pot. 
 
 If the skin is cold, moist, or clammy, the trouble is due to 
 heat exhaustion. Give plenty of fresh air, but apply no cold 
 to the body. Apply heat, and give hot drinks, like hot ginger 
 tea. Sunstroke or heatstroke is a dangerous affliction. It is 
 often followed by serious and permanent results. Persons who 
 have once suffered in this way should carefully avoid any risk 
 in the future. 
 
CHAPTER XIV. 
 IN SICKNESS AND IN HEALTH. 
 
 383. Arrangement of the Sick-room. This room, if pos- 
 sible, should be on the quiet and sunny side of the house. 
 Pure, fresh air, sunshine, and freedom from noise and odor are 
 almost indispensable. A fireplace as a means of ventilation is 
 invaluable. The bed should be so placed that the air may get 
 to it on all sides and the nurse move easily around it. Screens 
 should be placed, if necessary, so as to exclude superfluous 
 light and draughts. 
 
 The sick-room should be kept free from all odors which affect 
 the sick unpleasantly, as perfumery, highly scented soaps, and 
 certain flowers. Remove all useless ornaments and articles 
 likely to collect dust, as unnecessary pieces of furniture and 
 heavy draperies. A clean floor, with a few rugs to deaden the 
 footsteps, is much better than a woolen carpet. Rocking-chairs 
 should be banished from the sick-room, as they are almost sure 
 to disturb the sick. 
 
 A daily supply of fresh flowers tends to brighten the room. 
 Keep the medicines close at hand, but all poisonous drugs 
 should be kept carefully by themselves and ordinarily under 
 lock and key. A small table should be placed at the bedside, 
 and on it the bell, food tray, flowers and other small things 
 which promote the comfort of the patient. 
 
 The nurse should not sleep with the patient. Sofas and 
 couches are not commonly comfortable enough to secure needed 
 rest. A cot bed is at once convenient and inexpensive, and can 
 be readily folded and put out of sight in the daytime. It can 
 also be used by the patient occasionally, especially during con- 
 valescence. 
 
IN SICKNESS AND IN HEALTH. 387 
 
 384. Ventilation of the Sick-room. Proper ventilation is 
 most essential to the sick-room, but little provision is ordinarily 
 made for so important a matter. It is seldom that one of the 
 windows cannot be let down an inch or more at the top, a 
 screen being arranged to avoid any draught on the patient. 
 Remove all odors by ventilation and not by spraying perfumery, 
 or burning pastilles, which merely conceal offensive odors with- 
 out purifying the air. During cold weather and in certain 
 diseases, the patient may be covered entirely with blankets and 
 the windows opened wide for a few minutes. 
 
 Avoid ventilation by means of doors, for the stale air of the 
 house, kitchen smells, and noises made by the occupants of 
 the house, are apt to reach the sick-room. The entire air 
 of the room should be changed at least two or three times a 
 day, in addition to the introduction of a constant supply of 
 fresh air in small quantities. 
 
 385. Hints for the Sick-room. Always strive to look 
 cheerful and pleasant before the patient. Whatever may hap- 
 pen, do not appear to be annoyed, discouraged, or despondent. 
 Do your best to keep up the courage of sick persons under all 
 circumstances. In all things keep in constant mind the comfort 
 and ease of the patient. 
 
 Do not worry the sick with unnecessary questions, idle talk, 
 or silly gossip. It is cruel to whisper in the sick-room, for 
 patients are always annoyed by it. They are usually suspi- 
 cious that something is wrong and generally imagine that their 
 condition has changed for the worse. 
 
 Symptoms of the disease should never be discussed before 
 the patient, especially if he is thought to be asleep. He may 
 be only dozing, and any such talk would then be gross cruelty. 
 Loud talking must, of course, be avoided. The directions of 
 the physician must be rigidly carried out in regard to visitors 
 in the sick-room. This is always a matter of foremost impor- 
 
388 PRACTICAL PHYSIOLOGY. 
 
 tance, for an hour or even a night of needed sleep and rest 
 may be lost from the untimely call of some thoughtless visitor. 
 A competent nurse, who has good sense and tact, should be 
 able to relieve the family of any embarrassment under such 
 circumstances. 
 
 Do not ever allow a kerosene light with the flame turned 
 down to remain in the sick-room. Use the lamp with the flame 
 carefully shaded, or in an adjoining room, or better still, use a 
 sperm candle for a night light. 
 
 Keep, so far as possible, the various bottles of medicine, 
 spoons, glasses, and so on in an adjoining room, rather than 
 to make a formidable array of them on a bureau or table near 
 the sick-bed. A few simple things, as an orange, a tiny 
 bouquet, one or two playthings, or even a pretty book, may 
 well take their place. 
 
 The ideal bed is single, made of iron or brass, and provided 
 with woven wire springs and a hair mattress. Feather-beds are 
 always objectionable in the sick-room for many and obvious 
 reasons. The proper making of a sick-bed, with the forethought 
 and skill demanded in certain diseases, is of great importance 
 and an art learned only after long experience. The same 
 principle obtains in all that concerns the lifting and the moving 
 of the sick. 
 
 Sick people take great comfort in the use of fresh linen and 
 fresh pillows. Two sets should be used, letting one be aired 
 while the other is in use. In making changes the fresh linen 
 should be thoroughly aired and warmed and everything in 
 readiness before the patient is disturbed. 
 
 386. Rules for Sick-room. Do not deceive sick people. 
 Tell what is proper or safe to be told, promptly and plainly. 
 If a physician is employed, carry out his orders to the very 
 letter, as long as he visits you. Make on a slip of paper a note 
 of his directions. Make a brief record of exactly what to do. 
 
IN SICKNESS AND IN HEALTH. 389 
 
 the precise time of giving medicines, etc. This should always 
 be done in serious cases, and by night watchers. Then there 
 is no guesswork. You have the record before you for easy 
 reference. All such things are valuable helps to the doctor. 
 
 Whatever must be said in the sick-room, say it openly and 
 aloud. How often a sudden turn in bed, or a quick glance of 
 inquiry, shows that whispering is doing harm ! If the patient 
 is in his right mind, answer his questions plainly and squarely. 
 It may not be best to tell all the truth, but nothing is gained 
 in trying to avoid a straightforward reply. 
 
 Noises that are liable to disturb the patient, in other parts of 
 the house than the sick-room, should be avoided. Sounds of a 
 startling character, especially those not easily explained, as the 
 rattling or slamming of distant blinds and doors, are always 
 irritating to the sick. 
 
 Always attract the attention of a patient before addressing 
 him, otherwise he may be startled and a nervous spell be 
 induced. The same hint applies equally to leaning or sitting 
 upon the sick-bed, or running against furniture in moving 
 about the sick-room. 
 
 387. Rest of Mind and Body. The great importance of 
 rest for the sick is not so generally recognized as its value 
 warrants. If it is worry and not work that breaks down the 
 mental and physical health of the well, how much more impor- 
 tant is it that the minds and bodies of the sick should be kept at 
 rest, free from worry and excitement ! Hence the skilled nurse 
 does her best to aid in restoring the sick to a condition of health 
 by securing for her patient complete rest both of mind and body. 
 To this end, she skillfully removes all minor causes of alarm, 
 irritation, or worry. There are numberless ways in which this 
 may be done of which space does not allow even mention. De- 
 tails apparently trifling, as noiseless shoes, quietness, wearing 
 garments that do not rustle, use of small pillows of different sizes, 
 
39 PRACTICAL PHYSIOLOGY. 
 
 and countless other small things that make up the refinement 
 of modern nursing, play an important part in building up the 
 impaired tissues of the sick. 
 
 388. Care of Infectious and Contagious Diseases. . There 
 are certain diseases which are known to be infectious and can 
 be communicated from one person to another, either by direct 
 contact, through the medium of the atmosphere, or otherwise. 
 
 Of the more prevalent infectious and contagious diseases 
 are scarlet fever, diphtheria, erysipelas, measles, and typhoid fever. 
 
 Considerations of health demand that a person suffering from 
 any one of these diseases should be thoroughly isolated from 
 all other members of the family. All that has been stated in 
 regard to general nursing in previous sections of this chapter, 
 applies, of course, to nursing infectious and contagious diseases. 
 In addition to these certain special directions must be always 
 kept in mind. 
 
 Upon the nurse, or the person having the immediate charge 
 of the patient, rests the responsibility of preventing the spread 
 of infectious diseases. The importance must be fully under- 
 stood of carrying out in every detail the measures calculated 
 to check the spread or compass the destruction of the germs 
 of disease. 
 
 389. Hints on Nursing Infectious and Contagious Diseases. 
 
 Strip the room of superfluous rugs, carpets, furniture, etc. Iso- 
 late two rooms, if possible, and have these, if convenient, at the 
 top of the house. Tack sheets, wet in some proper disinfectant, 
 to the outer frame of the sick-room door. Boil these sheets 
 every third day. In case of diseases to which young folks are 
 very susceptible, send the children away, if possible, to other 
 houses where there are no children. 
 
 Most scrupulous care should be taken in regard to cleanli- 
 ness and neatness in every detail. Old pieces of linen, cheese- 
 cloth, paper napkins, should be used wherever convenient or 
 
IN SICKNESS AND IN HEALTH. 39 1 
 
 necessary and then at once burnt. All soiled clothing that can- 
 not well be burnt should be put to soak at once in disinfectants, 
 and afterward boiled apart from the family wash. Dishes and 
 all utensils should be kept scrupulously clean by frequent 
 boiling. For the bed and person old and worn articles of 
 clothing that can be destroyed should be worn so far as 
 possible. 
 
 During convalescence, or when ready to leave isolation, the 
 patient should be thoroughly bathed in water properly disin- 
 fected, the hair and nails especially being carefully treated. 
 
 Many details of the after treatment depend upon the special 
 disease, as the rubbing of the body with carbolized vaseline 
 after scarlet fever, the care of the eyes after measles, and 
 other particulars of which space does not admit mention here. 
 
 POISONS AND THEIR ANTIDOTES. 
 
 390. Poisons. A poison is a substance which, if taken into 
 the system in sufficient amounts, will cause serious trouble or 
 death. For convenience poisons may be divided into two 
 classes, irritants and narcotics. 
 
 The effects of irritant poisons are evident immediately 
 after being taken. They burn and corrode the skin or mem- 
 brane or other parts with which they come in contact. There 
 are burning pains in the mouth, throat, stomach, and abdomen, 
 with nausea and vomiting. A certain amount of faintness and 
 shock is also present. 
 
 With narcotic poisoning, the symptoms come on more slowly. 
 After a time there is drowsiness, which gradually increases until 
 there is a profound sleep or stupor, from which the patient can 
 be aroused only with great difficulty. There are some sub- 
 stances which possess both the irritant and narcotic properties 
 and in which the symptoms are of a mixed character. 
 
39 2 PRACTICAL PHYSIOLOGY. 
 
 391. Treatment of Poisoning. An antidote is a substance 
 which will either combine with a poison to render it harmless, 
 or which will have a directly opposite effect upon the body, 
 thus neutralizing the effect of the poison. Hence in treatment 
 of poisoning the first thing to do, if you know the special poison, 
 is to give its antidote at once. 
 
 If the poison is unknown, and there is any delay in obtaining 
 the antidote, the first thing to do is to remove the poison from 
 the stomach. Therefore cause vomiting as quickly as possible. 
 This may be done by an emetic given as follows : Stir a table- 
 spoonful of mustard or of common salt in a glass of warm 
 water and make the patient swallow the whole. It will usually 
 be vomited in a few moments. If mustard or salt is not at 
 hand, compel the patient to drink lukewarm water very freely 
 until vomiting occurs. 
 
 Vomiting may be hastened, by thrusting the forefinger down 
 the throat. Two teaspoonfuls of the syrup of ipecac, or a 
 heaping teaspoonful of powdered ipecac taken in a cup of 
 warm water, make an efficient emetic, especially if followed 
 with large amounts of warm water. 
 
 It is to be remembered that in some poisons, as certain acids 
 and alkalies, no emetic should be given. Again, for certain 
 poisons (except in case of arsenic) causing local irritation, but 
 which also affect the system at large, no emetic should be given. 
 
 392. Reference Table of Common Poisons ; Prominent 
 Symptoms ; Antidotes and Treatment. The common poisons 
 with their leading symptoms, treatment, and antidotes, may be 
 conveniently arranged for easy reference in the form of a table. 
 
 It is to be remembered, of course, that a complete mastery 
 of the table of poisons, as set forth on the two following pages, 
 is really a physician's business. At the same time, no one of 
 fair education should neglect to learn a few of the essential 
 things to do in accidental or intentional poisoning. 
 
IN SICKNESS AND IN HEALTH. 
 
 393 
 
 A TABLE OF THE MORE COMMON POISONS, 
 
 With their prominent symptoms, antidotes, and treatment. 
 
 POISON. 
 
 Strong Acids : 
 Muriatic, 
 Nitric, 
 
 Sulphuric (vitriol), 
 Oxalic. 
 
 Alkalies : 
 
 Caustic potash and 
 
 soda, 
 
 Ammonia, 
 Lye, 
 
 Pearlash, 
 Saltpeter. 
 
 Arsenic : 
 Paris green, 
 Rough on rats, 
 White arsenic, 
 Fowler's solution, 
 Scheele's green. 
 
 Other Metallic Poi- 
 sons : 
 
 Blue vitriol, 
 Copperas, 
 Green vitriol, 
 Sugar of lead, 
 Corrosive sublimate, 
 Bedbug poison. 
 
 Phosphorus from 
 Matches, rat poisons, 
 etc. 
 
 PROMINENT SYMPTOMS. 
 
 Burning sensation in 
 mouth, throat, and stom- 
 ach ; blisters about mouth ; 
 vomiting ; great weakness. 
 
 Burning sensation in the 
 parts; severe pain in stom- 
 ach; vomiting; difficulty 
 in swallowing; cold skin; 
 weak pulse. 
 
 Intense pains in stom- 
 ach and bowels ; thirst ; 
 vomiting, perhaps with 
 blood ; cold and clammy 
 skin. 
 
 Symptoms in general, 
 same as in arsenical poi- 
 soning. With lead and 
 mercury there may be a 
 metallic taste in the mouth. 
 
 Pain in the stomach ; 
 vomiting ; purging ; gen- 
 eral collapse. 
 
 ANTIDOTES AND TREAT- 
 MENT. 
 
 No emetic. Saleratus ; 
 chalk ; soap ; plaster from 
 the wall ; lime ; magnesia ; 
 baking soda (3 or 4 tea- 
 spoonfuls in a glass of 
 water). 
 
 No emetic. Olive oil 
 freely ; lemon juice ; vine- 
 gar ; melted butter and 
 vaseline ; thick cream. 
 
 Vomit patient repeat 
 edly ; give hydrated oxid 
 of iron with magnesia, usu- 
 ally kept by druggists for 
 emergencies ; follow with 
 strong solution of common 
 salt and water. 
 
 Emetic with lead ; none 
 with copper and iron ; white 
 of eggs in abundance with 
 copper ; with iron and lead 
 give epsom salts freely ; 
 afterwards, oils, flour, and 
 water. 
 
 No emetic -with mercury ; 
 raw eggs; milk, or flour 
 and water. 
 
 Cause vomiting. Strong 
 soapsuds ; magnesia in wa- 
 ter. Never give oils. 
 
394 
 
 PRACTICAL PHYSIOLOGY. 
 
 POISON. 
 Opium : 
 Morphine, 
 Laudanum, 
 Paregoric, 
 Dover's powder, 
 Soothing syrups, 
 Cholera and diar- 
 rhoea mixtures. 
 
 Carbolic Acid: 
 Creasote. 
 
 PROMINENT SYMPTOMS. 
 
 Sleepiness ; dullness ; 
 stupor ; " pinhole " pupils ; 
 slow breathing ; profuse 
 sweat. 
 
 Severe pain in abdomen ; 
 odor of carbolic acid, mu- 
 cous membrane in and 
 around mouth white and 
 benumbed ; cold, clammy 
 skin. 
 
 ANTIDOTES AND TREAT- 
 MENT. 
 
 Cause vomiting. Keep 
 patient awake by any 
 means, especially by vig- 
 orous walking ; give strong 
 coffee freely ; dash cold 
 water on face and chest. 
 
 No emetic. Milk, or flour 
 and water ; white of eggs. 
 
 Numbness everywhere ; 
 great weakness ; cold sweat. 
 
 Eyes bright, with pupil 
 enlarged ; dry mouth and 
 throat. 
 
 Vomit patient freely. 
 Stimulating drinks. 
 
 Vomit patient freely. 
 
 Aconite : 
 Wolfsbane, 
 Monkshood. 
 
 Belladonna : 
 
 Deadly nightshade, 
 Atropia. 
 
 Various Vegetable Poi- 
 sons : 
 
 Wild parsley, 
 Indian tobacco, 
 Toadstools, 
 Tobacco plant, 
 Hemlock, 
 
 Berries of the moun- 
 tain ash, 
 Bitter sweet, etc. 
 
 393. Practical Points about Poisons. Poisons should never 
 be kept in the same place with medicines or other prepara- 
 tions used in the household. They should always be put 
 in some secure place under lock and key. Never use inter- 
 nally or externally any part of the contents of any package or 
 
 Stupor, nausea, great Cause brisk vomiting. 
 
 weakness, and other symp- Stimulating drinks. 
 
 toms according to the poi- 
 
IN SICKNESS AND IN HEALTH. 395 
 
 bottle unless its exact nature is known. If there is the least 
 doubt about the substance, do not assume the least risk, but 
 destroy it at once. Many times the unknown contents of some 
 bottle or package has been carelessly taken and found to be 
 poison. 
 
 Careless and stupid people often take, by mistake, with seri- 
 ous, and often fatal, results, poisonous doses of carbolic acid, 
 bed-bug poison, horse-liniment, oxalic acid, and other poisons. 
 A safe rule is to keep all bottles and boxes containing poisonous 
 substances securely bottled or packed, and carefully labeled 
 with the word POISON plainly written in large letters across 
 the label. Fasten the cork of a bottle containing poison to the 
 bottle itself with copper or iron wire twisted into a knot at the 
 top. This is an effective means of preventing any mistakes, 
 especially in the night. 
 
 This subject of poisons assumes nowadays great importance, 
 as it is a common custom to keep about stables, workshops, 
 bathrooms, and living rooms generally a more or less formid- 
 able array of germicides, disinfectants, horse-liniments, insect- 
 poisons, and other preparations of a similar character. For 
 the most part they contain poisonous ingredients. 
 
 BACTERIA. 
 
 394. Nature of Bacteria. The word bacteria is the name 
 applied to very low forms of plant life of microscopic size. 
 Thus, if hay be soaked in water for some time, and a few 
 drops of the liquid are examined under a high power of the 
 microscope, the water is found to be swarming with various 
 forms of living vegetable organisms, or bacteria. These micro- 
 scopic plants belong to the great fungus division, and consist 
 of many varieties, which may be roughly divided into groups, 
 according as they are spherical, rod-like, spiral, or otherwise in 
 shape. 
 
39^ PRACTICAL PHYSIOLOGY. 
 
 Each plant consists of a mass of protoplasm surrounded by 
 an ill-defined cell wall. The bacteria vary considerably in 
 size. Some of the rod-shaped varieties are from ^5 to ^ of 
 an inch in length, and average about ^5 of an inch in diame- 
 ter. It has been calculated that a space of one cubic milli- 
 meter would contain 
 2 so, 000,000 of these 
 minute organisms, 
 and that they would 
 not weigh more than 
 a milligram. 
 
 Bacteria are pro- 
 pagated in a very 
 
 J riG. 160. Examples of Micro-Orgamsms called 
 simple manner. The Bacteria. (Drawn from photographs.) 
 
 parent Cell divides A> spheroidal bacteria (called cocci) in pairs ; B, same kind 
 
 into tWO ' these tWO of bacteria in chains; C, bacteria found in pus (grouped in 
 
 masses like a bunch of grapes). [Bacteria in A, B, and C 
 
 mtO tWO Others, and magnified about 1000 diameters]. D, bacteria found in pus 
 SO On. The rapidity (tendency to grow in the form of chains). [Magnified 
 . . about 500 diameters.] 
 
 with which these or- 
 ganisms multiply under favorable conditions, makes them, in 
 some cases, most dangerous enemies. It has been calculated 
 that if all of the organisms survived, one bacterium would 
 lead to the production of several billions of others in twenty- 
 four hours. 
 
 395. The Struggle of Bacteria for Existence. Like all 
 kinds of living things, many species of bacteria are destroyed 
 if exposed to boiling water or steam, but seem able to endure 
 prolonged cold, far below the freezing-point. Thus ice from 
 ponds and rivers may contain numerous germs which resume 
 their activity when the ice is melted. Typhoid fever germs 
 have been known to take an active and vigorous growth after 
 they have been kept for weeks exposed in ice to a temperature 
 below zero. 
 
IN SICKNESS AND IN HEALTH. 397 
 
 The bacteria of consumption (bacillus tuberculosis) may 
 retain their vitality for months, and then the dried expectora- 
 tion of the invalids may become a source of danger to those 
 who inhale air laden with such impurities (sec. 220 and Fig. 94). 
 
 Like other living organisms, bacteria need warmth, mois- 
 ture, and some chemical compound which answers for food, in 
 order to maintain the phenomena of life. Some species grow 
 only in contact with air, others need no more oxygen than they 
 can obtain in the fluid or semi-fluid which they inhabit. 
 
 396. Importance of Bacteria in Nature. We might well 
 ask why the myriads of bacteria do not devastate the earth 
 with their marvelous rapidity of propagation. So indeed 
 they might, were it not for the winds, rains, melting snow 
 and ice which scatter them far and wide, and destroy them. 
 
 Again, as in countless other species of living organisms, 
 bacteria are subject to the relentless law which allows only 
 the fittest to survive. The bacteria of higher and more 
 complex types devour those of a lower type. Myriads per- 
 ish in the digestive tract of man and other animals. The 
 excreta of some species of bacteria act as poison to destroy 
 other species. 
 
 It is true from the strictest scientific point of view that all 
 living things literally return to the dust whence they came. While 
 living they borrow a few elementary substances and arrange 
 them in new combinations, by aid of the energy given them by 
 the sun, and after a time die and leave behind all they had 
 borrowed both of energy and matter. 
 
 Countless myriads of bacteria are silently at work changing 
 dead animal and vegetable matter into useful substances. In 
 brief, bacteria prepare food for all the rest of the world. 
 Were they all destroyed, life upon the earth would be impos- 
 sible, for the elements necessary to maintain it would be 
 embalmed in the bodies of the dead. 
 
39$ PRACTICAL PHYSIOLOGY. 
 
 397. Action of Bacteria. In certain well-known processes 
 bacteria have the power of bringing about decomposition of 
 various kinds. Thus a highly organized fungus, like the yeast 
 plant, growing in the presence of sugar, has the power of 
 breaking down this complex body into simpler ones, viz., 
 alcohol and carbon dioxid. 
 
 In the same way, various forms of bacteria have the power 
 of breaking down complex bodies in their immediate neighbor- 
 hood, the products depending upon the substance, the kind of 
 bacteria, and the conditions under which they act. Thus the 
 bacteria lactis act 
 upon the milk sugar 
 present in milk, and j 
 convert it into lactic 
 acid, thus bringing V Vi 
 about the souring of 
 
 FIG. 169. Examples of Pathogenic Bacteria. 
 m (Drawn from photographs.) 
 
 NOW, While mOSt A, spiral form of bacteria found in cholera. (Magnified about 
 
 SDecieS Of bacteria roo diameters.) B, rod-shaped bacteria (called bacilli) 
 
 from a culture obtained in anthrax or malignant fustule 
 
 are harmless, SOme O f tne face. Diseased hides carry this micro-organism, and 
 are the Cause Of Sick- *^ us ma y occas i n disease among those who handle hides 
 and wool. (Magnified about 1000 diameters.) 
 
 ness and death when 
 
 they gain admittance to the body under certain conditions. 
 These disease-producing bacteria (known as pathogenic), when 
 established in the blood and tissues of the body, bring about 
 important chemical changes, depending upon the species of 
 bacteria, and also produce a particular form of disease. The 
 production of certain diseases by the agency of bacteria has 
 now been proved beyond all doubt. In yellow fever, ery- 
 sipelas, diphtheria, typhoid fever, consumption and other dis- 
 eases, the connection has been definitely established. 
 
 The evil results these germs of disease produce vary greatly 
 in kind and severity. Thus the bacteria of Asiatic cholera and 
 diphtheria may destroy life in a few hours, while those of con- 
 
IN SICKNESS AND IN HEALTH. 399 
 
 sumption may take years to produce a fatal result. Again, the 
 bacteria may attack some particular organ, or group of organs, 
 and produce mostly local symptoms. Thus in a boil there is 
 painful swelling due to the local effect of the bacteria, with 
 slight general disturbance. 
 
 398. The Battle against Bacteria. When we reflect upon 
 the terrible ravages made by infectious diseases, and all their 
 attendant evils for these many years, we can the better appre- 
 ciate the work done of late years by tireless scientists in their 
 efforts to modify the activity of disease-producing bacteria. It 
 is now possible to cultivate certain pathogenic bacteria, and 
 by modifying the conditions under which they are grown, to 
 destroy their violence. 
 
 In brief, science has taught us, within certain limitations, 
 how to change the virulent germs of a few diseases into 
 harmless microbes. 
 
 399. Alcoholic Fermentation and Bacteria. Men of the 
 
 lowest, as well as of the highest, type of civilization have always 
 known that when the sugary juice of any fruit is left to itself 
 for a time, at a moderately warm temperature, a change takes 
 place under certain conditions, and the result is a liquid which, 
 when drank, produces a pronounced effect upon the body. In 
 brief, man has long known how to make for himself alcoholic 
 beverages, by means of which he may become intoxicated with 
 their poisonous ingredients. 
 
 Whether it is a degraded South Sea Islander making a crude 
 intoxicant from a sugary plant, a Japanese preparing his 
 favorite alcoholic beverage from the fermentation of rice by 
 means of a fungus plant grown for the purpose, a farmer of 
 this country making cider from fermenting apple juice, or a 
 French expert manufacturing costly champagne by a compli- 
 cated process, the outcome and the intent are one and the 
 
4OO PRACTICAL PHYSIOLOGY. 
 
 same. The essential thing is to produce an alcoholic bev- 
 erage which will have a marked physiological effect. This 
 effect is poisonous, and is due solely to the alcoholic ingre- 
 dient, without which man would have little or no use for the 
 otherwise harmless liquid. 
 
 While the practical process of making some form of alcoholic 
 beverage has been understood for these many centuries, the 
 real reason of this remarkable change in a wholesome fruit 
 juice was not known until revealed by recent progress in 
 chemistry, and by the use of the microscope. We know now 
 that the change is due to fermentation, brought about from the 
 influence, and by the action, of bacteria (sec. 125). 
 
 In other words, fermentation is the result of the growth of a 
 low form of vegetable life known as an organised ferment. This 
 ferment, whether it be the commonly used brewer's yeast, or 
 any other species of alcoholic ferment, has the power to decom- 
 pose or break down a large part of the sugar present in the 
 liquid into alcohol, which remains as a poison, and carbon 
 dioxid, which escapes more or less completely. 
 
 Thus man, ever prone to do evil, was once obliged, in his 
 ignorance, to make his alcoholic drinks in the crudest manner ; 
 but now he has forced into his service the latest discoveries in 
 science, more especially in bacteriology, that he may manu- 
 facture more scientifically and more economically alcoholic 
 beverages of all sorts and kinds, and distribute them broadcast 
 all over God's earth for the physical and moral ruin of the 
 people. 
 
 DISINFECTANTS. 
 
 400. Disinfectants, Antiseptics, and Deodorants. The word 
 disinfectant is synonymous with the term bacteridde or germi- 
 cide. A disinfectant is a substance which destroys infectious 
 material. An antiseptic is an agent which may hinder the 
 
IN SICKNESS AND IN HEALTH. 4OI 
 
 growth, but does not destroy the vitality, of bacteria. A deo- 
 dorant is not necessarily a disinfectant, or even an antiseptic, 
 but refers to a substance that destroys or masks offensive 
 odors. 
 
 401. Air and Water as Disinfectants. Nature has pro- 
 vided for our protection two most efficient means of disinfec- 
 tion, pure air (sec. 218) and pure water (sec. 119). The 
 air of crowded rooms contains large quantities of bacteria, 
 whereas in pure air there are comparatively few, especially 
 after rain, which carries them to the earth. Living micro- 
 organisms have never been detected in breezes coming from 
 the sea, but in those blowing out from the shore large numbers 
 may be found. 
 
 In water tainted with organic matter putrefactive bacteria will 
 flourish, whereas pure water is fatal to their existence. Sur- 
 face water, because it comes from that part of the soil where 
 bacteria are most active, and where there is most organic mat- 
 ter, generally contains great quantities of these organisms. In 
 the deeper strata of the soil there is practically no decomposi- 
 tion of organic matter going on, hence, water taken from deep 
 sources is comparatively free from bacteria. For this reason, 
 deep well water is greatly to be preferred for drinking purposes 
 to that from surface wells. 
 
 402. Disinfectants. It is evident that air and water are 
 not always sufficient to secure disinfection, and this must be 
 accomplished by other means. The destruction of infected 
 material by fire is, of course, a sure but costly means of disin- 
 fection. Dry heat, steam, and boiling water are valuable 
 disinfectants and do not injure most fabrics. These agents 
 are generally used in combination with various chemical dis- 
 infectants. 
 
 Certain chemical agents that are capable of destroying 
 
4O2 PRACTICAL PHYSIOLOGY. 
 
 micro-organisms and their spores have come, of late years, 
 into general use. A form of mercury, called corrosive subli- 
 mate, is a most efficacious and powerful germicide, but is 
 exceedingly poisonous and can be bought only under restric- 
 tions. 1 Carbolic acid, chloride of lime, permanganate of potash, 
 and various other preparations made from zinc, iron, and 
 petroleum, are the chemical disinfectants most commonly and 
 successfully used at the present time. There are also numerous 
 varieties of commercial disinfectants now in popular use, such 
 as Platt's chlorides, bromo-chloral, sanitas, etc., which have 
 proved efficient germicides. 
 
 INSTRUCTIONS FOR THE MANAGEMENT OF CONTAGIOUS 
 
 DISEASES. 
 
 The following instructions for the management .of contagious 
 diseases were prepared for the National Board of Health by 
 an able corps of scientists and experienced physicians. 
 
 403. Instructions for Disinfection. Disinfection is the de- 
 struction of the poisons of infectious and contagious diseases. 
 
 Deodorizers, or substances which destroy smells, are not 
 necessarily disinfectants, and disinfectants do not necessarily 
 have an odor. Disinfection cannot compensate for want of 
 cleanliness nor of ventilation. 
 
 404. Disinfectants to be Employed, i. Roll sulphur (brim- 
 stone); for fumigation. 
 
 2. Sulphate of iron (copperas) dissolved in water in the pro- 
 portion of one and a half pounds to the gallon ; for soil, 
 sewers, etc. 
 
 1 Corrosive sublimate is probably the most powerful disinfectant known. A solu- 
 tion of one part in 2000 will destroy microscopic organisms. Two teaspoonfuls of 
 this substance will make a solution strong enough to kill all disease germs. 
 
 NOTE. A most useful little manual to consult in connection with this chapter is 
 the Hand-Book of Sanitary Information, written by Roger S. Tracy, Sanitary 
 Inspector of the New York City Health Department. Price, 50 cents. 
 
IN SICKNESS AND IN HEALTH. 403 
 
 3. Sulphate of zinc and common salt, dissolved together in 
 water in the proportion of four ounces sulphate and two ounces 
 salt to the gallon ; for clothing, bed-linen, etc. 
 
 405 How to Use Disinfectants. i. In the sick-room. 
 The most available agents are fresh air and cleanliness. The 
 clothing, towels, bed-linen, etc., should, on removal from the 
 patient, and before they are taken from the room, be placed in 
 a pail or tub of the zinc solution, boiling-hot, if possible. 
 
 All discharges should either be received in vessels contain- 
 ing copperas solution, or, when this is impracticable, should be 
 immediately covered with copperas solution. All vessels used 
 about the patient should be cleansed with the same solution. 
 
 Unnecessary furniture, especially that which is stuffed, car- 
 pets, and hangings, should, when possible, be removed from 
 the room at the outset ; otherwise they should remain for sub- 
 sequent fumigation and treatment. 
 
 2. Fumigation. Fumigation with sulphur is the only prac- 
 ticable method for disinfecting the house. For this purpose, 
 the rooms to be disinfected must be vacated. Heavy clothing, 
 blankets, bedding, and other articles which cannot be treated 
 with zinc solution, should be opened and exposed during fumi- 
 gation, as directed below. Close the rooms as tightly as 
 possible, place the sulphur in iron pans supported upon bricks 
 placed in washtubs containing a little water, set it on fire by hot 
 coals or with the aid of a spoonful of alcohol, and allow the 
 room to remain closed for twenty-four hours. For a room 
 about ten feet square, at least two pounds of sulphur should 
 be used ; for larger rooms, proportionally increased quantities. 1 
 
 1 The burning of sulphur produces sulphurous acid, which is an irrespirable gas. 
 The person who lights the sulphur must, therefore, immediately leave the room, and 
 after the lapse of the proper time, must hold his breath as he enters the room to open 
 the windows and let out the gas. After fumigation, plastered walls should be white- 
 washed, the woodwork well scrubbed with carbolic soap, and painted portions re- 
 painted. 
 
404 PRACTICAL PHYSIOLOGY. 
 
 3. Premises. Cellars, yards, stables, gutters, privies, cess- 
 pools, water-closets, drains, sewers, etc., should be frequently 
 and liberally treated with copperas solution. The copperas 
 solution is easily prepared by hanging a basket containing 
 about sixty pounds of copperas in a barrel of water. 1 
 
 4. Body and bed clothing, etc. It is best to burn all arti- 
 cles which have been in contact with persons sick with con- 
 tagious or infectious diseases. Articles too valuable to be 
 destroyed should be treated as follows : 
 
 (a) Cotton, linen, flannels, blankets, etc., should be treated 
 with the boiling-hot zinc solution ; introduce piece by piece, 
 secure thorough wetting, and boil for at least half an hour. 
 
 (b) Heavy woolen clothing, silks, furs, stuffed bed-covers, 
 beds, and other articles which cannot be treated with the zinc 
 solution, should be hung in the room during fumigation, their 
 surfaces thoroughly exposed and pockets turned inside out. 
 Afterward they should be hung in the open air, beaten, and 
 shaken. Pillows, beds, stuffed mattresses, upholstered furni- 
 ture, etc., should be cut open, the contents spread out and 
 thoroughly fumigated. Carpets are best fumigated on the 
 floor, but should afterward be removed to the open air and 
 thoroughly beaten. 
 
 l Put copperas in a pail of water, in such quantity that some may constantly re- 
 main undissolved at the bottom. This makes a saturated solution. To every privy 
 or water-closet, allow one pint of the solution for every four persons when cholera is 
 about. To keep privies from being offensive, pour one pint into each seat, night and 
 morning. 
 
 Books for Collateral Study. Among the many works which may be consulted 
 with profit, the following are recommended as among those most useful : Parkes' 
 Elements of Health ; Canfield's Hygiene of the Sick-Room ; Coplin & Bevan's Prac- 
 tical Hygiene ; Lincoln's School Hygiene; Edward Smith's Health; McSherry's 
 Health; American Health Primers (12 little volumes, edited by Dr. Keen of Phila- 
 delphia) ; Reynold's Primer of Health ; Corfield's Health ; Appleton's Health 
 Primers; Clara S. Weeks' Nursing; Church's Food; Yeo's Food in Health and 
 Disease ; Hampton's Nursing, its Principles and Practice ; Price's Nurses and 
 Nursing; Cullinworth's Manual of Nursing; Wise's Text-Book of Nursing 
 (2 vols.) ; and Humphrey's Manual of Nursing. 
 
CHAPTER XV. 
 EXPERIMENTAL WORK IN PHYSIOLOGY. 
 
 406. The Limitations of Experimental Work in Physiology in 
 Schools. Unlike other branches of science taught in the schools 
 from the experimental point of view, the study of physiology has its 
 limitations. The scope and range of such experiments is necessarily 
 extremely limited compared with what may be done with the costly 
 and elaborate apparatus of the medical laboratory. Again, the foun- 
 dation of physiology rests upon systematic and painstaking dissec- 
 tion of the dead human body and the lower animals, which mode of 
 study very properly is not permitted in ordinary school work. Experi- 
 ments upon the living human body and the lower animals, now so 
 generally depended upon in our medical and more advanced scientific 
 schools, for obvious reasons can be performed only in a crude and 
 quite superficial manner in secondary schools. 
 
 Hence in the study of physiology in schools many things must be 
 taken for granted. The observation and experience of medical men, 
 and the experiments of the physiologist in his laboratory must be 
 depended upon for data which cannot be well obtained at first hand 
 by young students. 
 
 407. Value of Experiments in Physiology in Secondary Schools. 
 
 While circumstances and regard for certain proprieties of social life 
 forbid the use of a range of experiments, in anatomy and physiology, 
 such as are permitted in other branches of science in secondary 
 schools, it by no means follows that we are shut out altogether from 
 this most important and interesting part of the study. However 
 simple and crude the apparatus, the skillful and enthusiastic teacher 
 
 NOTE. For additional suggestions and practical helps on the subject of experi- 
 mental work in physiology the reader is referred to Blaisdell's Hoiv to Teach 
 Physiology, a handbook for teachers. A copy of this pamphlet will be sent postpaid 
 to any address by the publishers of this book on receipt of ten cents. 
 
4O6 PRACTICAL PHYSIOLOGY. 
 
 has at his command a wide series of materials which can be profit- 
 ably utilized for experimental instruction. As every experienced 
 teacher knows, pupils gain a far better knowledge, and keep up a 
 livelier interest in any branch of science, if they see with their own 
 eyes and do with their own hands that which serves to illuminate and 
 illustrate the subject-matter. 
 
 The experimental method of instruction rivets the attention and 
 arouses and keeps alive the interest of the young student ; in fact, it is 
 the only true method of cultivating a scientific habit of study. 1 The 
 subject-matter as set forth on the printed pages of this book should 
 be mastered, of course, but at the same time the topics discussed 
 should be illuminated and made more interesting and practical by a 
 well-arranged series of experiments, a goodly show of specimens, and 
 a certain amount of microscopical work. 
 
 408. The Question of Apparatus. The author well understands 
 from personal experience the many practical difficulties in the way of 
 providing a suitable amount of apparatus for class-room use. If there 
 are ample funds for this purpose, there need be no excuse or delay in 
 providing all that is necessary from dealers in apparatus in the larger 
 towns, from the drug store, markets, and elsewhere. In schools 
 where both the funds and the time for such purposes are limited, 
 the zeal and ingenuity of teachers and students are often put to a 
 severe test. Fortunately a very little money and a great deal of 
 ingenuity and patience will do apparent wonders towards providing a 
 working supply of apparatus. 
 
 l " While physiology is one of the biological sciences, it should be clearly recog- 
 nized that it is not, like botany or zoology, a science of observation and descrip- 
 tion; but rather, like physics or chemistry, a science of experiment. While the 
 amount of experimental instruction (not involving vivisection or experiment other- 
 wise unsuitable) that may with propriety be given in the high school is neither small 
 nor unimportant, the limitations to such experimental teaching, both as to kind and 
 as to amount, are plainly indicated. 
 
 " The obvious limitations to experimental work in physiology in the high school, 
 already referred to, make it necessary for the student to acquire much of the desired 
 knowledge from the text-book only. Nevertheless, much may be done by a thought- 
 ful and ingenious teacher to make such knowledge real, by the aid of suitable practi- 
 cal exercises and demonstrations." Report of the Committee of Ten on Secondary 
 School Studies. 
 
EXPERIMENTAL WORK IN PHYSIOLOGY. 
 
 407 
 
 It will be noticed that many of the experiments in the preceding 
 chapters of this book can be performed with very simple, and often 
 a crude and home-made sort of apparatus. This plan has been rigidly 
 followed by the author, first, because he fully realizes the limitations 
 and restrictions of the subject ; and secondly, because he wishes to 
 emphasize the fact that expensive and complicated apparatus is by 
 no means necessary to illustrate the great principles of anatomy and 
 physiology. 
 
 409. Use of the Microscope. To do thorough and satisfactory 
 work in physiology in our higher schools a compound microscope is 
 almost indispensable. Inasmuch as many 
 of our best secondary schools are equipped 
 with one or more microscopes for use in 
 other studies, notably botany, it is much 
 less difficult than it was a few years ago to 
 obtain this important help for the classes 
 in physiology. 
 
 For elementary class work a moderate- 
 priced, but well-made and strong, instrument 
 should be provided. If the school does not 
 own a microscope, the loan of an instrument 
 should be obtained for at least a few weeks 
 from some person in the neighborhood. 
 
 The appearance of the various structures 
 and tissues of the human body as revealed 
 by the microscope possesses a curious fas- 
 cination for every observer, especially for 
 young people. No one ever forgets the 
 first look at a drop of blood, or the circulation of blood in a frog's 
 foot as shown by the microscope. 
 
 NOTE. For detailed suggestions in regard to the manipulation and use of the 
 microscope the student is referred to any of the standard works on the subject. The 
 catalogues of scientific-instrument makers of our larger cities generally furnish a list 
 of the requisite materials or handbooks which describe the use of the various micro- 
 scopes of standard make. 
 
 The author is indebted to Bergen's Elements of Botany for the following informa- 
 tion concerning the different firms which deal in microscopes. "Several of the 
 
 FIG. 170. A Compound 
 Microscope. 
 
4O8 PRACTICAL PHYSIOLOGY. 
 
 German makers furnish excellent instruments for use in such a course as that here 
 outlined. The author is most familar with the Leitz microscopes, which are furnished 
 by Wm. Krafft, 411 West 5gth St., New York city, or by the Franklin Educational 
 Co., 15 and 17 Harcourt St., Boston. The Leitz Stand, No. IV., can be furnished 
 duty free (for schools only), with objectives i, 3, and 5, eye-pieces I. and III., for 
 $24.50. If several instruments are being provided, it would be well to have part of 
 them equipped with objectives 3 and 7, and eye-pieces I. and III. 
 
 " The American manufacturers, Bausch & Lomb Optical Company, Rochester, 
 N. Y., and No. 130 Fulton St., New York city, have this year produced a micro- 
 scope of the Continental type which is especially designed to meet the requirements 
 of the secondary schools for an instrument with rack and pinion coarse adjustment 
 and serviceable fine adjustment, at a low price. They furnish this new stand, 
 ' AAB/ to schools and teachers at ' duty-free' rates, the prices being for the stand 
 with two eye-pieces (any desired power), -inch and $-inch objectives, $25.60. or with 
 2-inch, -inch, and j-inch objectives, and two eye-pieces, $29.20. Stand ' A,' the 
 same stand as the ' AAB,' without joint and with sliding tube coarse adjustment 
 (as in the Leitz Stand IV.), and with three eye-pieces and -inch and }-mch objectives, 
 is furnished for $20.40. Stand ' A,' with two eye-pieces, -inch and -inch objectives, 
 $20.40." 
 
 410. The Use of the Skeleton and Manikin. The study of the 
 bones by the help of a skeleton is almost a necessity. To this 
 intent, schools of a higher grade should be provided both with a 
 skeleton and a manikin. If the former is not owned by the school, 
 oftentimes a loan of one can be secured of some medical man in the 
 vicinity. Separate bones will also prove useful. In fact, there is 
 no other way to study properly the structure and use of the bones 
 and joints than by the bones themselves. A good manikin is also 
 equally serviceable, although not so commonly provided for schools 
 on account of its cost. 
 
 411. The Question of Vivisection and Dissection. There should 
 be no question at all concerning vivisection. In no shape or form 
 should it be allowed in any grade of our schools. Nor is there any 
 need of much dissection in the grammar-school grades. A few sim- 
 ple dissections to be performed with fresh beef-joints, tendons of 
 turkey legs, and so on, will never engender cruel or brutal feelings 
 toward living things. In the lower grades a discreet teacher will 
 rarely advise his pupils to dissect a dead cat, dog, frog, or any other 
 animal. Instead of actual dissection, the pupils should examine 
 specimens efr certain parts previously dissected by the teacher, as 
 
EXPERIMENTAL WORK IN PHYSIOLOGY. 409 
 
 the muscles and tendons of a sheep, the heart of an ox, the eye of a 
 cod-fish, and so on. Even under these restrictions the teacher should 
 not use the knife or scissors before the class to open up any part of 
 the specimen. In brief, avoid everything that can possibly arouse 
 any cruel or brutal feeling on the part of young students. 
 
 In the higher schools, in normal and other training schools, differ- 
 ent conditions prevail. Never allow vivisection in any form what- 
 ever, either in school or at home. Under the most exact restrictions 
 students in these schools may be taught to make a few simple 
 dissections. 
 
 Most teachers will find, however, even in schools of a higher 
 grade, that the whole subject is fraught with many difficulties. It 
 will not require much oftentimes to provoke in a community a deal 
 of unjust criticism. A teacher's good sense and discretion are often 
 put to a severe test. 
 
 ADDITIONAL EXPERIMENTS. 
 
 To the somewhat extended list of experiments as described in the pre- 
 ceding chapters a few more are herewith presented which may be used as 
 opportunity allows to supplement those already given. 
 
 Experiment 193. To examine "white fibrous tissue. Snip off a very minute 
 portion from the muscle of a rabbit, or any small animal recently dead. 
 Tease the specimen with needles, mount in salt solution and examine under 
 a high power. Note the course and characters of the fibers. 
 
 Experiment 194. To examine elastic tissue. Tease out a small piece of 
 ligament from a rabbit's leg in salt solution ; mount in the same, and exam- 
 ine as before. Note the curled elastic fibers. 
 
 Experiment 195. To examine areolar tissue. Gerftly tease apart some 
 muscular fibers, noting that they^are attached to each other by connective 
 tissue. Remove a little of this tissue to a slide and examine as before. 
 Examine the matrix with curled elastic fiber mixed with straight white 
 fibers. 
 
 Experiment 196. To examine adipose tissue. Take a bit of fat from the 
 mesentery of a rabbit. Tease the specimen in salt solution and mount in 
 the same. Note the fat cells lying in a vascular meshwork. 
 
41 PRACTICAL PHYSIOLOGY. 
 
 Experiment 197. To examine connective tissues. Take a very small por- 
 tion from one of the tendons of a rabbit, or any animal recently dead ; 
 place upon a glass slide with a drop of salt solution . tease it apart with 
 needles, cover with thin glass and examine with microscope. The fine 
 wavy filaments will be seen. Allow a drop of dilute acetic acid to run under 
 the cover glass; the filaments will swell and become transparent. 
 
 Experiment 198. Tease out a small piece of ligament from the rabbit's 
 leg in salt solution ; mount in the same, and examine under a high power. 
 Note the curled elastic fibers. 
 
 Experiment 199. A crude experiment to represent the way in -which a 
 person's neck is broken. Bring the ends of the left thumb and the left 
 second finger together in the form of a ring. Place a piece of a wooden 
 toothpick across it from the middle of the finger to the middle of the 
 thumb. Put the right forefinger of the other hand up through the front 
 part to represent the odontoid process of the axis, and place some absorb- 
 ent cotton through the other part to represent the spinal cord. Push back- 
 wards with the forefinger with just enough force to break the toothpick 
 and drive its fragrnents on to the cotton. 
 
 Experiment 200. To illustrate how the pulse-wave is transmitted along 
 an artery. Use the same apparatus as in Experiment 106, p. 201. Take 
 several thin, narrow strips of pine wood. Make little flags by fastening a 
 small piece of tissue paper on one end of a wooden toothpick. Wedge 
 the other end of the toothpick into one end of the strips of pine wood. 
 Use these strips like levers by placing them across the long rubber tube at 
 different points. Let each lever compress the tube a little by weighting 
 one end of it with a blackboard eraser or book of convenient size. 
 
 As the pulse-wave passes along under the levers they will be successively 
 raised, causing a slight movement of the tissue-paper flags. 
 
 Experiment 201. The dissection of a sheep 's heart. Get a sheep's 
 heart with the lungs -attached, as the position of the heart will be better 
 understood. Let the lungs be laid upon a dish so that the heart is upper- 
 most, with its apex turned toward the observer. 
 
 The line of fat which extends from the upper and left side of the heart 
 downwards and across towards the right side, indicates the division be- 
 tween the right and left ventricles. 
 
 Examine the large vessels, and, by reference to the text and illustrations, 
 make quite certain which are the aorta, the pulmonary artery, the superior 
 and inferior vena cavce, and the pulmonary veins. 
 
EXPERIMENTAL WORK IN PHYSIOLOGY. 411 
 
 Tie variously colored yarns to the vessels, so that they may be distin- 
 guished when separated from the surrounding parts. 
 
 Having separated the heart from the lungs, cut out a portion of the wall 
 of the right ventricle towards its lower part, so as to lay the cavity open. 
 Gradually enlarge the opening until the chorda; tendinece and the flaps of 
 the tricuspid valve are seen. Continue to lay open the ventricle towards the 
 pulmonary artery until the semilunar valves come into view. 
 
 The pulmonary artery may now be opened from above so as to display 
 the upper surfaces of the semilunar valves. Remove part of the wall of 
 the right auricle, and examine the right auriculo-ventricular opening. 
 
 The heart may now be turned over, and the left ventricle laid open in a 
 similar manner. Notice that the mitral valve has only two flaps. The 
 form of the valves is better seen if they are placed under water, and 
 allowed to float out. Observe that the walls of the left ventricle are much 
 thicker than those of the right. 
 
 Open the left auricle, and notice the entrance of the pulmonary veins, 
 and the passage into the ventricle. 
 
 The ventricular cavity should now be opened up as far as the aorta, and 
 the semilunar valves examined. Cut open the aorta, and notice the form 
 of the semilunar valves. 
 
 Experiment 202. To show the circulation in a frog's foot (see Fig. 78, 
 p. 192). In order to see the blood circulating in the membrane of a 
 frog's foot it is necessary to firmly hold the frog. For this purpose obtain 
 a piece of soft wood, about six inches long and three wide, and half an inch 
 thick. At about two inches from one end of this, cut a hole three-quarters 
 of an inch in diameter and cover it with a piece of glass, which should be 
 let into the wood, so as to be level with the surface. Then tie up the frog 
 in a wet cloth, leaving one of the hind legs outside. Next, fasten a piece 
 of cotton to each of the two longest toes, but not too tightly, or the circu- 
 fation will be stopped and you may hurt the frog. 
 
 Tie the frog upon the board in such a way that the foot will just come 
 over the glass in the aperture. Pull carefully the pieces of cotton tied to 
 the toes, so as to spread out the membrane between them over the glass. 
 Fasten the threads by drawing them into notches cut in the sides of the 
 board. The board should now be fixed by elastic bands, or by any other 
 convenient means, upon the stage of the microscope, so as to bring the 
 membrane of the foot under the object glass. 
 
 The flow of blood thus shown is indeed a wonderful sight, and never to 
 be forgotten. The membrane should be occasionally moistened with water. 
 
 Care should be taken not to occasion any pain to the frog. 
 
412 
 
 PRACTICAL PHYSIOLOGY. 
 
 Experiment 203. To illustrate the mechanics of respiration 1 (see Experi- 
 ment 122, p. 234). " In a large lamp-chimney, the top of which is closed by 
 a tightly fitting perforated cork (A), is arranged a pair of rubber bags (C) 
 which are attached to a Y connecting tube (B), to be had of any dealer in 
 chemical apparatus or which can be made by a teacher having a bunsen 
 burner and a little practice in the manipulation of glass (Fig. 171). From 
 the center of the cork is attached a rubber band 
 by means of a staple driven through the cork, the 
 other end of which (D) is attached to the center 
 of a disk of rubber (E) such as dentists use. This 
 disk is held to the edge of the chimney by a wide 
 elastic band (F). There is a string (G) also at- 
 tached to the center of the rubber disk by means 
 of which the diaphragm may be lowered. 
 
 Such is a description of the essentials of the 
 model. The difficulties encountered in its con- 
 struction are few and easily overcome. In the first 
 place, the cork must be air-tight, and it is best 
 made so by pouring a little melted paraffin over it, 
 care being taken not to close the tube. The rubber 
 bags were taken from toy balloon-whistles. 
 
 In the construction of the diaphragm, it is to be 
 remembered that it also must be air-tight, and in 
 order to resemble the human diaphragm, it must 
 
 have a conical appearance when at rest. In order to avoid making any 
 holes in the rubber, the two attachments (one of the rubber band, and the 
 other of the string) were made in this wise : the rubber was stretched over 
 a button having an eye, then under the button was placed a smaller ring 
 from an old umbrella ; to this ring was attached the rubber band, and to 
 the eye of the button was fastened the operating string. When not in 
 use the diaphragm should be taken off to relieve the strain on the rubber 
 band." 
 
 Experiment 204. To illustrate the action of the intercostal muscles (see 
 sec. 210). The action of the intercostal muscles is not at first easy to 
 understand ; but it will be readily comprehended by reference to a model 
 such as that represented in Fig. 172. This maybe easily made by the stu- 
 dent himself with four laths of wood, fastened together at the corners, 
 
 1 This ingenious and excellent experiment is taken from the New York School 
 Journal for May, 1897, for which paper it was prepared by Charles D. Nason, of 
 Philadelphia. 
 
 FIG. 171. 
 
EXPERIMENTAL WORK IN PHYSIOLOGY. 
 
 413 
 
 A, B, C, D, with pins or small screws, so as to be movable. At the points 
 E, F, G, H, pins are placed, to which elastic bands may be attached (A). 
 B D represents the vertebral column ; A C, the sternum ; and A B and 
 C D, the ribs. The elastic band F G represents the external intercostal 
 muscles, and E H, the internal intercostals. 
 
 If now the elastic band E H be removed, the remaining band, F G, 
 will tend to bring the two points to which it is attached, nearer together, 
 
 FIG. 172. 
 
 and the result will be that the bars A B and C D will be drawn upwards 
 (B), that is, in the same direction as the ribs in the act of inspiration. 
 When the elastic band E H is allowed to exert its force, the opposite 
 effect will be produced (C) ; in this case representing the position of the 
 ribs in an act of expiration. 
 
 Experiment 205. Pin a round piece of bright red paper (large as a din- 
 ner-plate) to a white wall, with a single pin. Fasten a long piece of thread 
 to it, so it can be pulled down in a moment. Gaze steadily at the red paper. 
 Have it removed while looking at it intently, and a greenish spot takes its 
 place. 
 
 Experiment 206. Lay on different parts of the skin a small, square 
 piece of paper with a small central hole in it. Let the person close his 
 eyes, while another person gently touches the uncovered piece of skin with 
 cotton wool, or brings near it a hot body. In each case ask the observed 
 person to distinguish between them. He will always succeed on the volar 
 side of the hand, but occasionally fail on the dorsal surface of the hand, 
 the extensor surface of the arm, and very frequently on the skin of the back. 
 
 Experiment 207. Wheatstone* s fluttering hearts. Make a drawing of a 
 red heart on a bright blue ground. In a dark room lighted by a candle 
 hold the picture below the level of the eyes and give it a gentle to-and-fro 
 motion. On continuing to look at the heart it will appear to move or flutter 
 over the blue background. 
 
414 PRACTICAL PHYSIOLOGY. 
 
 Experiment 208. At a distance of six inches from the eyes hold a veil 
 or thin gauze in front of some printed matter placed at a distance of about 
 two feet. Close one eye, and with the other we soon see either the letters 
 distinctly or the fine threads of the veil, but we cannot see both equally 
 distinct at the same time. The eye, therefore, can form a distinct image 
 of a near or distant object, but not of both at the same time ; hence the 
 necessity for accommodation. 
 
 Experiment 209. Place a person in front of a bright light opposite a 
 window, and let him look at the light ; or place one's self opposite a well- 
 illuminated mirror. Close one eye with the hand and observe the diameter 
 of the other pupil. Then suddenly remove the hand from the closed eye : 
 light falls upon it ; at the same time the pupil of the other eye contracts. 
 
 Experiment 210. To illustrate the blind spot. Marriott's experiment. 
 On a white card make a cross and a large dot, either black or colored. 
 Hold the card vertically about ten inches from the right eye, the left being 
 closed. Look steadily at the cross with the right eye, when both the cross 
 and the circle will be seen. Gradually approach the card tow r ard the eye, 
 keeping the axis of vision fixed on the cross. At a certain distance the 
 circle will disappear, i.e., when its image falls on the entrance of the optic 
 nerve. On bringing the card nearer, the circle reappears, the cross, of 
 course, being visible all the time (see Experiment 180, p. 355). 
 
 Experiment 211. To map out the field of -vision. A crude method is to 
 place the person with his back to a window, ask him to close one eye, 
 stand in front of him about two feet distant, hold up the forefingers of both 
 hands in front of and in the plane of your own face. Ask the person to 
 look steadily at your nose, and as he does so observe to what extent the 
 fingers can be separated horizontally, vertically, and in oblique directions 
 before they disappear from his field of vision. 
 
 Experiment 212. To illustrate imperfect judgment of distance. Close 
 one eye and hold the left forefinger vertically in front of the other eye, at 
 arm's length, and try to strike it with the right forefinger. 
 
 On the first trial one will probably fall short of the mark, and fail to 
 touch it. Close one eye, and rapidly try to dip a pen into an inkstand, or 
 put a finger into the mouth of a bottle placed at a convenient distance. In 
 both cases one will not succeed at first. 
 
 In these cases one loses the impressions produced by the convergence of 
 the optic axes, which are important factors in judging of distance. 
 
 Experiment 213. Hold a pencil vertically about twelve inches from 
 the nose, fix it with both eyes, close the left eye, and then hold the right 
 
EXPERIMENTAL WORK IN PHYSIOLOGY. 415 
 
 index finger vertically, so as to cover the lower part of the pencil. With a 
 sudden move, try to strike the pencil with the finger. In every case one 
 misses the pencil and sweeps to the right of it. 
 
 Experiment 214. To illustrate imperfect judgment of direction. As the 
 retina is spherical, a line beyond a certain length when looked at always 
 shows an appreciable curvature. 
 
 Hold a straight edge just below the level of the eyes. Its upper margin 
 shows a slight concavity. 
 
 SURFACE ANATOMY AND LANDMARKS. 
 
 In all of our leading medical colleges the students are carefully 
 and thoroughly drilled on a study of certain persons selected as 
 models. The object is to master by observation and manipulation the 
 details of what is known as surface anatomy and landmarks. Now 
 while detailed work of this kind is not necessary in secondary schools, 
 yet a limited amount of study along these lines is deeply interesting 
 and profitable. The habit of looking at the living body with anatom- 
 ical eyes and with eyes at our fingers' ends, during the course in 
 physiology, cannot be too highly estimated. 
 
 In elementary work it is only fair to state that many points of sur- 
 face anatomy and many of the landmarks cannot always be defined 
 or located with precision. A great deal in this direction can, how- 
 ever, be done in higher schools with ingenuity, patience, and a due 
 regard for the feelings of all concerned. Students should be taught 
 to examine their own bodies for this purpose. Two friends may thus 
 work together, each serving as a " model " to the other. 
 
 To the following syllabus may be added such other similar exer- 
 cises as ingenuity may suggest or time permit. 
 
 SYLLABUS. 
 
 I. BONY LANDMARKS. 
 
 i. The occipital protuberance can be distinctly felt at the back 
 of the head. This is always the thickest part (often three-quarters 
 of an inch or more) of the skull-cap, and is more prominent in some 
 than in others. The thinnest part is over the temples, where it may 
 be almost as thin as parchment. 
 
41 6 PRACTICAL PHYSIOLOGY. 
 
 2. The working of the condyle of the lower jaw vertically and 
 from side to side can be distinctly felt and seen in front of the ear. 
 When the mouth is opened wide, the condyle advances out of the 
 glenoid cavity, and returns to its socket when the mouth is shut. In 
 front of the ear, lies the zygoma, one of the most marked and impor- 
 tant landmarks to the touch, and in lean persons to the eye. 
 
 3. The sliding movement of the scapula on the chest can be 
 properly understood only on the living subject. It can move not 
 only upwards and downwards, as in shrugging the shoulders, back- 
 wards and forwards, as in throwing back the shoulders, but it has a 
 rotary movement round a movable center. This rotation is seen 
 while the arm is being raised from the horizontal to the vertical posi- 
 tion, and is effected by the cooperation of the trapezius with the 
 serratus magnus muscles. 
 
 4. The patella, or knee-pan, the two condyles of the tibia, the 
 tubercle on the tibia for the attachment of the ligament of the patella, 
 and the head of the fibula are the chief bony landmarks of the knee. 
 The head of the fibula lies at the outer and back part of the tibia. 
 In extension of the knee, the patella is nearly all above the condyles. 
 The inner border of the patella is thicker and more prominent than 
 the outer, which slopes down toward its condyle. 
 
 5. The short, front edge of the tibia, called the " shin," and the 
 broad, flat, subcutaneous surface of the bone can be felt all the way 
 down. The inner edge can be felt, but not so plainly. 
 
 6. The head of the fibula is a good landmark on the outer side 
 of the leg, about one inch below the top of the tibia. Note that it 
 is placed well back, and that it forms no part of the knee joint, and 
 takes no share in supporting the weight. The shaft of the fibula 
 arches backwards and is buried deep among the muscles, except at 
 the lower fourth, which can be distinctly felt. 
 
 7. The malleoli form the great landmarks of the ankle. The 
 outer malleolus descends lower than the inner. The inner malleolus 
 advances more to the front and does not descend so low as the outer. 
 
 8. The line of the clavicle, or collar bone, and the projection of 
 the joint at either end of it can always be felt. Its direction is not 
 perfectly horizontal, but slightly inclined downwards. We can dis- 
 tinctly feel the spine of the scapula and its highest point, the acromion. 
 
EXPERIMENTAL WORK IN PHYSIOLOGY. 417 
 
 9. Projecting beyond the acromion (the arm hanging by the side), 
 we can feel, through the fibers of the deltoid, the upper part of the 
 humerus. It distinctly moves under the hand when the arm is 
 rotated. It is not the head of the bone which is felt, but its promi- 
 nences (the tuberosities). The greater, externally ; the lesser in front. 
 
 10. The tttberosities of the humerits form the convexity of the 
 shoulder. When the arm is raised, the convexity disappears, there 
 is a slight depression in its place. The head of the bone can be felt 
 by pressing the fingers high up in the axilla. 
 
 11. The humerus ends at the elbow in two bony prominences 
 (internal and external condyles). The internal is more prominent. 
 We can always feel the olecranon. Between this bony projection of 
 the ulna and the internal condyle is a deep depression along which runs 
 the ulna nerve (commonly called the " funny " or " crazy " bone). 
 
 12. Turn the hand over with the palm upwards, and the edge of 
 the ulna can be felt from the olecranon to the prominent knob 
 (styloid process) at the wrist. Turn the forearm over with the 
 palm down, and the head of the ulna can be plainly felt and seen 
 projecting at the back of the wrist. 
 
 13. The upper half of the radius cannot be felt because it is so 
 covered by muscles ; the lower half is more accessible to the touch. 
 
 14. The three rows of projections called the " knuckles " are 
 formed by the proximal bones of the several joints. Thus the first 
 row is formed by the ends of the metacarpals, the second by the 
 ends of the first phalanges, and the third by the ends of the second 
 phalanges. That is, in all cases the line of the joints is a little in 
 advance of the knuckles and nearer the ends of the fingers. 
 
 II. MUSCULAR LANDMARKS. 
 
 1. The position of the sterno-mastoid muscle as an important and 
 interesting landmark of the neck has already been described (p. 70). 
 
 2. If the left arm be raised to a vertical position and dropped to 
 a horizontal, somewhat vigorously, the tapering ends of the pectoralis 
 major and the tendons of the biceps and deltoid may be felt by 
 pressing the parts in the axilla between the fingers and thumb of the 
 right hand. 
 
41 8 PRACTICAL PHYSIOLOGY. 
 
 3. The appearance of the biceps as a landmark of the arm has 
 already been described (p. 70). The action of its antagonist, the 
 triceps, may be studied in the same manner. 
 
 4. The sartorius is one of the fleshy landmarks of the thigh, as 
 the biceps is of the arm, and the sterno-cleido-mastoid of the neck. 
 Its direction and borders may be easily traced by raising the leg, 
 a movement which puts the muscle in action. 
 
 5. If the model be directed to stand on tiptoe, both of the large 
 muscles of the calf, the gastrocnemius and soleus, can be distin- 
 guished. 
 
 6. Direct the model, while sitting upright, to cross one leg over 
 the other, using his utmost strength. The great muscles of the inner 
 thigh are fully contracted. Note the force required to pull the legs 
 to the ordinary position. 
 
 7. With the model lying in a horizontal position with both legs 
 firmly held together, note the force required to pull the feet apart 
 while the great muscles of the thigh are fully contracted. 
 
 8. In forcible and resisted flexion of the wrist two tendons come 
 up in relief. On the outer side of one we feel the pulse at the 
 wrist, the radial artery here lying close to the radius. 
 
 9. On the outer side of the wrist we can distinctly see and feel, 
 when in action, the three extensor tendons of the thumbs. Between 
 two of them is a deep depression at the base of the thumb, which the 
 French call the " anatomical tobacco box." 
 
 10. The relative position of the several extensor tendons on the 
 back of the wrist and fingers as they play in their grooves over the 
 back of the radius and ulna can be distinctly traced when the several 
 muscles are put in action. 
 
 11. There are several strong tendons to be seen and felt about 
 the ankle. Behind is the tendo Achillis. It forms a high relief with 
 a shallow depression on each side of it. Behind both the inner and 
 outer ankle several tendons can be felt. Over the front of the ankle, 
 when the muscles are in action, we can see and feel several tendons. 
 They start up like cords when the action is resisted. They are kept 
 in their proper relative position by strong pulleys formed by the 
 annular ligament. Most of these tendons can be best seen by stand- 
 a model on one foot, i.e. in unstable equilibrium. 
 
EXPERIMENTAL WORK IN PHYSIOLOGY. 419 
 
 III. LANDMARKS OF THE HEART. 
 
 To have a general idea of the form and position of the heart, map 
 its outline with colored pencils or crayon on the chest wall itself, or 
 on some piece of clean, white cloth, tightly pinned over the clothing 
 A pattern of the heart may be cut out of pasteboard, painted red, or 
 papered with red paper, and pinned in position outside the clothing. 
 The apex of the heart is at a point about two inches below the left 
 nipple and one inch to its sternal side. This point will be between 
 the fifth and sixth ribs, and can generally be determined by feeling 
 the apex beat. 
 
 IV. LANDMARKS OF A FEW ARTERIES. 
 
 The pulsation of the temporal artery can be felt in front of the 
 ear, between the zygoma and the ear. The facial artery can be dis- 
 tinctly felt as it passes over the upper jaw at the front edge of the 
 masseter muscle. The pulse of a sleeping child can often be counted 
 at the anterior fontanelle by the eye alone. 
 
 About one inch above the clavicle, near the outer border of the 
 sterno-mastoid, we can feel the pulsation of the great subclavian 
 artery. At the back of the knee the popliteal artery can be felt beat- 
 ing. The dorsal artery of the foot can be felt beating on a line from 
 the middle of the ankle to the interval between the first and second 
 metatarsal bones. 
 
 When the arm is raised to a right angle with the body, the axillary 
 artery can be plainly felt beating in the axilla. Extend the arm with 
 palm upwards and the brachial artery can be felt close to the inner 
 side of the biceps. The position of the radial artery is described in 
 Experiment 102. 
 
GLOSSARY. 
 
 Abdomen (Lat. abdo, abdere, to conceal). The largest cavity of the body, 
 
 containing the liver, stomach, intestines, and other organs. 
 Abductor (Lat. abduco, to draw from). A muscle which draws a limb from 
 
 the middle line of the body, or a ringer or toe from the middle line of 
 
 the foot or hand. 
 Absorbents (Lat. absorbere, to suck up). The vessels which take part in 
 
 the process of absorption. 
 Absorption. The process of sucking up nutritive or waste matters by the 
 
 blood-vessels or lymphatics. 
 Accommodation of the Eye. The alteration in the shape of the crystalline 
 
 lens, which accommodates, or adjusts, the eye for near or remote 
 
 vision. 
 Acetabulum (Lat. acetabulum, a small vinegar-cup). The cup-shaped 
 
 cavity of the innominate bone for receiving the head of the femur. 
 Acid (Lat. acidus, from acere, to be sour). A substance usually sour, 
 
 sharp, or biting to the taste. 
 Acromion (Gr. &Kpov, the tip, and a>/w>s, the shoulder). The part of the 
 
 scapula forming the tip of the shoulder. 
 Adam's Apple. An angular projection of cartilage in the front of the 
 
 neck. It may be particularly prominent in men. 
 Adductor (Lat. adduce, to draw to). A muscle which draws towards the 
 
 middle line of the body, or of the hand or foot. 
 Adenoid (Gr. dS-^v, a gland). Tissue resembling gland tissue. 
 Afferent (Lat. ad, to, andfero, to convey). Vessels or nerves carrying the 
 
 contents or impulses from the periphery to the center. 
 Albumen, or Albumin (Lat. albus, white). An animal substance resem- 
 bling the white of an egg. 
 Albuminuria. A combination of the words " albumin " and " urine." 
 
 Presence of albumen in the urine. 
 
 Aliment (Lat. alo, to nourish). That which affords nourishment ; food. 
 Alimentary (Lat. alimentum, food). Pertaining to aliment, or food. 
 
422 GLOSSARY. 
 
 Alimentary Canal (Lat. alimentum). The tube in which the food is 
 
 digested or prepared for reception into the blood. 
 
 Alkali (Arabic al kali, the soda plant). A name given to certain sub- 
 stances, such as soda, potash, and the like, which have the power of 
 
 combining with acids. 
 Alveolar (Lat. alveolus, a little hollow). Pertaining to the alveoli, the 
 
 cavities for the reception of the teeth. 
 Amoeba (Gr. d/xe//3w, to change). A single-celled, protoplasmic organism, 
 
 which is constantly changing its form by protrusions and withdrawals 
 
 of its substance. 
 Amoeboid. Like an amceba. 
 Ampulla (Lat. ampulla, a wine-flask). The dilated part of the semicircular 
 
 canals of the internal ear. 
 Anabolism (Gr. dva[3d\\<t), to throw or build up). The process by means 
 
 of which simpler elements are built up into more complex. 
 Anaesthetics (Gr. (Lv, without, and alff0v}ffla, feeling). Those medicinal 
 
 agents which prevent the feeling of pain, such as chloroform, ether, 
 
 laughing-gas, etc. 
 Anastomosis (Gr. dvd, by, and <rT6/j,a, a mouth). The intercommunication 
 
 of vessels. 
 Anatomy (Gr. dmrtyuw, to cut up). The science which describes the 
 
 structure of living things. The word literally means dissection. 
 Antiseptic (Lat. anti, against, and sepsis, poison). Opposing or counter- 
 acting putrefaction. 
 
 Antrum (Lat. antrum, a cave). The cavity in the upper jaw. 
 Aorta (Gr. do/ar^, from detpo, to raise up). The great artery that rises' up 
 
 from the left ventricle of the heart. 
 Aponeurosis (Gr. d-n-6, from, and vevpov, a nerve). A fibrous membranous 
 
 expansion of a tendon ; the nerves and tendons were formerly thought 
 
 to be identical structures, both appearing as white cords. 
 Apoplexy (Gr. diroir^&a, a sudden stroke). The escape of blood from a 
 
 ruptured blood-vessel into the substance of the brain. 
 Apparatus. A number of organs of various sizes and structures working 
 
 together for some special object. 
 Appendages (Lat. ad and pendeo, to hang from). Something connected 
 
 with a part. 
 Aqueous Humor (Lat. aqua, water). The watery fluid occupying the space 
 
 between the cornea and crystalline lens of the eye. 
 Arachnoid Membrane (Gr. dpdxvrj, a spider, and et'Sws, like). The thin 
 
 covering of the brain and spinal cord, between the dura mater and the 
 
 pia mater. 
 
GLOSSARY. 423 
 
 Arbor Vitae. Literally, " the tree of life " ; a name given to the peculiar 
 
 appearance presented by a section of the cerebellum. 
 Areolar (Lat. areola, a small space, dim. of area). A term applied to a 
 
 connective tissue containing small spaces. 
 Artery (Gr. ayp, air, and reptw, to contain). A vessel by which blood is 
 
 carried away from the heart. It was supposed by the ancients to con- 
 
 tain only air, hence the name. 
 Articulation (Lat. articulo, to form a joint). The more or less movable 
 
 union of bones, etc. ; a joint. 
 Arytenoid Cartilages (Gr. dpi/ream, a ladle). Two small cartilages of the 
 
 larynx, resembling the mouth of a pitcher. 
 Asphyxia (Gr. d, without, and cr0/is, the pulse). Literally, " without pulse." 
 
 Condition caused by non-oxygenation of the blood. 
 Assimilation (Lat. ad, to, and similis, like). The conversion of food into 
 
 living tissue. 
 Asthma (Gr. a<r8/j.a, a gasping). Spasmodic affection of the bronchial tubes 
 
 in which free respiration is interfered with, owing to their diminished 
 
 caliber. 
 Astigmatism (Gr. d, without, and ffriy/ju, a point). Irregular refraction of 
 
 the eye, producing a blurred image. 
 Atrophy (Gr. d, without, and rpoQ-f), nourishment). Wasting of a part 
 
 from lack of nutrition. 
 
 Auditory Nerve (Lat. audio, to hear). The special nerve of hearing. 
 Auricle (Lat. auricula, a little ear). A cavity of the heart. 
 Azygos (Gr. d, without, and vy6s, a yoke). Without fellow ; not paired. 
 
 Bacteria (paKTrfpiov, a staff). A microscopic, vegetable organism; certain 
 
 species are active agents in fermentation, while others appear to be the 
 
 cause of infectious diseases. 
 
 Bactericide (Bacterium and Lat. caedere, to kill). Same as germicide. 
 Bile. The gall, or peculiar secretion of the liver ; a viscid, yellowish fluid, 
 
 and very bitter to the taste. 
 Biology (Gr. filos, life, and \6yos, discourse). The science which treats of 
 
 living bodies. 
 Bladder (Saxon bleddra, a bladder, a goblet). A bag, or sac, serving as a 
 
 receptacle of some secreted fluid, as the gall bladder, etc. The recep- 
 
 tacle of the urine in man and other animals. 
 Bright's Disease. A group of diseases of the kidney, first described by 
 
 Dr. Bright, an English physician. 
 Bronchi (Gr. /3p67xos, windpipe). The first two divisions, or branches, of 
 
 the trachea ; one enters each lung. 
 
4 2 4 GLOSSARY. 
 
 Bronchial Tubes. The smaller branches of the trachea within the sub- 
 stance of the lungs terminating in the air cells. 
 
 Bronchitis. Inflammation of the larger bronchial tubes ; a " cold " affect- 
 ing the air passages. 
 
 Bunion. An enlargement and inflammation of the first joint of the great 
 toe. 
 
 Bursa. A pouch ; a membranous sac interposed between parts which are 
 subject to movement, one on the other, to allow them to glide smoothly. 
 
 Callus (Lat. calleo, to be thick-skinned). Any excessive hardness of the 
 skin caused by friction or pressure. 
 
 Canal (Lat. canalis, a canal). A tube or passage. 
 
 Capillary (Lat. capillus, hair). The smallest blood-vessels, so called 
 because they are so minute. 
 
 Capsule (Lat. capsula, a little chest). A membranous bag enclosing a part. 
 
 Carbon Dioxid, often called carbonic acid. The gas which is present in the 
 air breathed out from the lungs ; a waste product of the animal king- 
 dom and a food of the vegetable kingdom. 
 
 Cardiac (Gr. Kapdla, the heart). The cardiac orifice of the stomach is the 
 upper one, and is near the heart ; hence its name. 
 
 Carnivorous (Lat. caro, flesh, and voro, to devour). Subsisting upon flesh. 
 
 Carron Oil. A mixture of equal parts of linseed oil and lime-water, so 
 called because first used at the Carron Iron Works in Scotland. 
 
 Cartilage. A tough but flexible material forming a part of the joints, air 
 passages, nostrils, ear; gristle, etc. 
 
 Caruncle (Lat. caro, flesh). The small, red, conical-shaped body at the 
 inner angle of the eye, consisting of a cluster of follicles. 
 
 Casein '(Lat. caseus, cheese). The albuminoid substance of milk; it forms 
 the basis of cheese. 
 
 Catarrh. An inflammation of a mucous membrane, usually attended with 
 an increased secretion of mucus. The word is often limited to nasal 
 catarrh. 
 
 Cauda Equina (Lat., horse's tail). The collection of large nerves descend- 
 ing from the lower end of the spinal cord. 
 
 Cell (Lat. cella, a storeroom). The name of the tiny miscroscopic ele- 
 ments, which, with slender threads or fibers, make up most of the body; 
 they were once believed to be little hollow chambers ; hence the name. 
 
 Cement. The substance which forms the outer part of the fang of a tooth. 
 
 Cerebellum (dim. for cerebrum, the brain). The little brain, situated 
 beneath the posterior third of the cerebrum. 
 
 Cerebrum. The brain proper, occupying the upper portion of the skull. 
 
GLOSSARY. 425 
 
 Ceruminous (Lat. cerumen, ear wax). A term applied to the glands secret- 
 ing cerumen, or ear wax. 
 
 Chloral. A powerful drug and narcotic poison used to produce sleep. 
 
 Chloroform. A narcotic poison generally used by inhalation ; of exten- 
 sive use in surgical operations. It produces anaesthesia. 
 
 Chondrin (Gr. x oi/ fy>6s, cartilage). A kind of gelatine obtained by boiling 
 cartilage. 
 
 Chordae Tendineae. Tendinous cords. 
 
 Choroid (Gr. -^opLov, skin, and e?5os, form). The middle coat of the eyeball. 
 
 Chyle (Gr. %v\6s, juice). The milk-like fluid formed by the digestion of 
 fatty articles of food in the intestines. 
 
 Chyme (Gr. xu/i6s, juice). The pulpy liquid formed by digestion in the 
 stomach. 
 
 Cilia (pi. of cilium, an eyelash). Minute hair-like processes found upon 
 the cells of the air passages and other parts. 
 
 Ciliary Muscle. A small muscle of the eye which assists in accommodation. 
 
 Circumvallate (Lat. circum, around, and vallum, a rampart). Surrounded 
 by a rampart, as are certain papillae of the tongue. 
 
 Coagulation (Lat. coagulo, to curdle). Applied to the process by which 
 the blood clots or solidifies. 
 
 Cochlea (Lat. cochlea, a snail shell). The spiral cavity of the internal ear. 
 
 Columnar Carneae. Fleshy projections in the ventricles of the heart. 
 
 Commissure (Lat. con, together, and mitto, missum, to put). A joining or 
 uniting together. 
 
 Compress. A pad or bandage applied directly to an injury to compress it. 
 
 Concha (Gr. KoyxVi a mussel shell). The shell-shaped portion of the 
 external ear. 
 
 Congestion (Lat. con, together, and gero, to bring). Abnormal gathering 
 of blood in any part of the body. 
 
 Conjunctiva (Lat. con, together, and jungo, to join). A thin layer of 
 mucous membrane which lines the eyelids and covers the front of the 
 eyeball, thus joining the latter to the lids. 
 
 Connective Tissue. The network which connects the minute parts of 
 most of the structures of the body. 
 
 Constipation (Lat. con, together, and stipo, to crowd close). Costiveness. 
 
 Consumption (Lat. consumo, to consume). A disease of the lungs, attended 
 with fever and cough, and causing a decay of the bodily powers. The 
 medical name is phthisis. 
 
 Contagion (Lat. con, with, and tango or tago, to touch). The communica- 
 tion of disease by contact, or by the inhalation of the effluvia of a sick 
 person. 
 
426 GLOSSARY. 
 
 Contractility (Lat. con, together, and traho, to draw). The property of a 
 muscle which enables it to contract, or draw its extremities closer 
 together. 
 
 Convolutions (Lat. con, together, and volvo, to roll). The tortuous fold- 
 ings of the external surface of the brain. 
 
 Convulsion (Lat. convello, to pull together). A more or less violent agita- 
 tion of the limbs or body. 
 
 Coordination. The manner in which several different organs of the body 
 are brought into such relations with one another that their functions 
 are performed in harmony. 
 
 Coracoid (Gr. /c6/ra, a crow, eiSos, form). Shaped like a crow's beak. 
 
 Cornea (Lat. cornu, a horn). The transparent horn-like substance which 
 covers a part of the front of the eyeball. 
 
 Coronary (Lat. corona, a crown). A term applied to vessels and nerves 
 which encircle parts, as the coronary arteries of the heart. 
 
 Coronoid (Gr. Kop&vr), a crow). Like a crow's beak; thus the coronoid 
 process of the ulna. 
 
 Cricoid (Gr. /cphcos, a ring, and e?5os, form). A cartilage of the larynx 
 resembling a seal ring in shape. 
 
 Crystalline Lens (Lat. crystallum, a crystal). One of the humors of the 
 eye ; a double-convex body situated in the front part of the eyeball. 
 
 Cumulative. A term applied to the violent action from drugs which super- 
 venes after the taking of several doses with little or no effect. 
 
 Cuticle (Lat. dim. of cutis, the skin). Scarf skin ; the epidermis. 
 
 Cutis (Gr. 0-KUTos, a skin or hide). The true skin, also called the dcrmis. 
 
 Decussation (Lat. decusso, decussatum, to cross). The crossing or running 
 of one portion athwart another. 
 
 Degeneration (Lat. degenerare, to grow worse, to deteriorate). A change 
 in the structure of any organ which makes it less fit to perform its duty. 
 
 Deglutition (Lat. deglutire, to swallow). The process of swallowing. 
 
 Deltoid. Having a triangular shape ; resembling the Greek letter A 
 (delta). 
 
 Dentine (Lat. dens, dentis, a tooth). The hard substance which forms 
 the greater part of a tooth ; ivory. 
 
 Deodorizer. An agent which corrects any foul or unwholesome odor. 
 
 Dextrin. A soluble substance obtained from starch. 
 
 Diabetes Mellitus (Gr. Sid, through, pal, to go, and /uAt, honey). Exces- 
 sive flow of sugar-containing urine. 
 
 Diaphragm (Gr. diacfrpdcro-w, to divide by a partition). A large, thin muscle 
 which separates the cavity of the chest from the abdomen. 
 
GLOSSARY. 427 
 
 Diastole (Gr. Smo-reXXw, to dilate). The dilatation of the heart. 
 
 Dietetics. That part of medicine which relates to diet, or food. 
 
 Diffusion of Gases. The power of gases to become intimately mingled. 
 
 Diploe (Gr. 5nrX6w, to double, to fold). The osseous tissue between the 
 tables of the skull. 
 
 Dipsomania (Gr. 5tya, thirst, and f^avla, madness).. An insatiable desire 
 for intoxicants. 
 
 Disinfectants. Agents used to destroy the germs or particles of living 
 matter that are believed to be the causes of infection. 
 
 Dislocation (Lat. dislocare, to put out of place). An injury to a joint in 
 which the bones are displaced or forced out of their sockets. 
 
 Dissection (Lat. dis, apart, and seco, to cut). The cutting up of an animal 
 in order to learn its structure. 
 
 Distal (Lat. dis, apart, and sto, to stand). Away from the center. 
 
 Duct (Lat. duco, to lead). A narrow tube. 
 
 Duodenum (Lat. duodeni, twelve). The first division of the small intes- 
 tines, about twelve fingers' breadth long. 
 
 Dyspepsia (Gr. -5i/s, ill, and irt-n-Teiv, to digest). A condition of the ali- 
 mentary canal in which it digests imperfectly. Indigestion. 
 
 Dyspnoea (Gr. dfa, difficult, and irvtw, to breathe). Difficult breathing. 
 
 Efferent (Lat. effero, to carry out). Bearing or carrying outwards, as from 
 
 the center to the periphery. 
 Effluvia (Lat. effluo, to flow out). Exhalations or vapors coming from the 
 
 body, and from decaying animal or vegetable substances. 
 Element. One of the simplest parts of which anything consists. 
 Elimination (Lat. <?, out of, and limen, liminis, a threshold). The act of 
 
 expelling waste matters. Signifies, literally, " to throw out of doors." 
 Emetic (Gr. ^w, to vomit). A medicine which causes vomiting. 
 Emulsion (Lat. emulgere, to milk). Oil in a finely divided state, suspended 
 
 in water. 
 
 Enamel (Fr. Entail}. Dense material covering the crown of a tooth. 
 Endolymph (Gr. evdov, within, and Lat. lympha, water). The fluid in the 
 
 membranous labyrinth of the ear. 
 
 Endosmosis (Gr. evdov, within, and u)0e?w, to push). The current from with- 
 out inwards when diffusion of fluids takes place through a membrane. 
 Epidemic (Gr. lirl, upon, and S^uos, the people).' An extensively prevalent 
 
 disease. 
 Epiglottis (Gr. tirl, upon, and y\6rns, the entrance to the windpipe). A 
 
 leaf-shaped piece of cartilage which covers the top of the larynx during 
 
 the act of swallowing. 
 
428 GLOSSARY. 
 
 Epilepsy (Gr. ^TrtXtj^is, a seizure). A nervous disease accompanied by fits 
 
 in which consciousness is lost ; the falling sickness. 
 Ether (Gr. aid^p, the pure, upper air). A narcotic poison. Used as an 
 
 anaesthetic in surgical operations. 
 Eustachian (from an Italian anatomist named Eustachi). The tube which 
 
 leads from the throat to the middle ear, or tympanum. 
 Excretion (Lat. excerno, to separate). The separation from the blood of 
 
 the waste matters of the body ; also the materials excreted. 
 Exosmosis (Gr. ew, without, and wdtw, to push). The current from within 
 
 outwards when diffusion of fluids takes place through a membrane. 
 Expiration (Lat. expiro, to breathe out). The act of forcing air out of the 
 
 lungs. 
 
 Extension (Lat. ex, out, and tendo, to stretch). The act of restoring a limb, 
 etc., to its natural position after it has been flexed or bent ; the opposite 
 
 of flexion, 
 
 Fauces. The part of the mouth which opens into the pharynx. 
 Fenestra (Lat.). Literally, "a window." Fenestra ovalis and fenestra 
 
 rotunda, the oval and the round window ; two apertures in the bone 
 
 between the tympanic cavity and the labyrinth of the ear. 
 Ferment. That which causes fermentation, as yeast. 
 Fermentation ( Lat. ferme ntum, boiling). The process of undergoing an 
 
 effervescent change, as by the action of yeast ; in a wider sense, the 
 
 change of organized substances into new compounds by the action of a 
 
 ferment. It differs in kind according to the nature of the ferment. 
 Fiber (Lak.jibra, a filament). One of the tiny threads of which many parts of 
 
 the body are composed. 
 Fibrilla. A little fiber; one of the longitudinal threads into which a 
 
 striped muscular fiber can be divided. 
 Fibrin (Lat. fibra, a fiber). An albuminoid substance contained in the 
 
 flesh of animals, and also produced by the coagulation of blood. 
 Flexion (Lat. flecto, to bend). The act of bending a limb, etc. 
 Follicle (Lat. dim. oifollis, a moneybag). A little pouch or depression. 
 Fomentation (Ls&.foveo, to keep warm). The application of any warm, 
 
 medicinal substance to the body, by which the vessels are relaxed. 
 Foramen. A hole, or aperture. 
 Frontal Sinus. A blind or closed cavity in the bones of the skull just 
 
 over the eyebrows. 
 Fumigation (Lat. fumigo, to perfume a place). The use of certain fumes, 
 
 to counteract contagious effluvia. 
 Function (La.t. functio, a doing). The special duty of any organ. 
 
GLOSSARY. 429 
 
 Ganglion (Gr. 7077X101', a knot). A knot-like swelling in a nerve ; a 
 
 smaller nerve center. 
 
 Gastric (Gr. yacrnrip, stomach). Pertaining to the stomach. 
 Gelatine (Lat. gelo, to congeal). An animal substance which dissolves in 
 
 hot water and forms a jelly on cooling. 
 
 Germ (Lat. germen, a sprout, bud). Disease germ ; a name applied to cer- 
 tain tiny bacterial organisms which have been demonstrated to be the 
 
 cause of disease. 
 Germicide (Germ, and Lat. caedere, to kill). Any agent which has a 
 
 destructive action upon living germs, especially bacteria. 
 Gland (Lat. glans, an acorn). An organ consisting of follicles and ducts, 
 
 with numerous blood-vessels interwoven. 
 Glottis (Gr. 7\6TTd, the tongue). The narrow opening between the vocal 
 
 cords. 
 
 Glucose. A kind of sugar found in fruits, also known as grape sugar. 
 Gluten. The glutinous albuminoid ingredient of cereals. 
 Glycogen. Literally, " producing glucose." Animal starch found in liver, 
 
 which may be changed into glucose. 
 Gram. Unit of metric system, 1 5.43 grains troy. 
 Groin. The lower part of the abdomen, just above each thigh. 
 Gustatory (Lat. gusto, gustatum, to taste). Belonging to the sense of taste. 
 Gymnastics (Gr. yvfj.vdfa, to exercise). The practice of athletic exercises. 
 
 Haemoglobin (Gr. afyia, blood, and Lat. globus, a globe or globule). A 
 
 complex substance which forms the principal coloring constituent of 
 
 the red corpuscles of the blood. 
 Hemispheres (Gr. ^/u,/, half, and 0-0cupa, a sphere). Half a sphere, the 
 
 lateral halves of the cerebrum, or brain proper. 
 Hemorrhage (Gr. af/t, blood, and p-fiyvvfju, to burst). Bleeding, or the loss 
 
 of blood. 
 
 Hepatic (Gr. rfirap, the liver). Pertaining to the liver. 
 Herbivorous (Lat. herba, an herb, and voro, to devour). Applied to animals 
 
 that subsist upon vegetable food. 
 Heredity. The predisposition or tendency derived from one's ancestors 
 
 to definite physiological actions. 
 Hiccough. A convulsive motion of some of the muscles used in breathing, 
 
 accompanied by a shutting of the glottis. 
 Hilum, sometimes written Hilus. A small fissure, notch, or depression. 
 
 A term applied to the concave part of the kidney. 
 Homogeneous (Gr. 6^65, the same, and ytvos, kind). Of the same kind or 
 
 quality throughout ; uniform in nature, the reverse of heterogeneous. 
 
43 GLOSSARY. 
 
 Humor. The transparent contents of the eyeball. 
 
 Hyaline (Gr. u'aXos, glass). Glass-like, resembling glass in transparency. 
 
 Hydrogen. An elementary gaseous substance, which, in combination with 
 
 oxygen, produces water. 
 Hydrophobia (Gr. vdup, water, and 0oj3^o/icu, to fear). A disease caused by 
 
 the bite of a rabid dog or other animal. 
 Hygiene (Gr. vyleia, health). The art of preserving health and preventing 
 
 disease. 
 Hyoid (Gr. letter v, and eT5os, form, resemblance). The bone at the root 
 
 of the tongue, shaped like the Greek letter v. 
 Hypermetropia (Gr. irn-ty, over, beyond, ^rpov, measure, and u\f/, the eye). 
 
 Far-sightedness. 
 Hypertrophy (Gr. virtp, over, and rpofi-/), nourishment). Excessive growth ; 
 
 thickening or enlargement of any part or organ. 
 
 Incisor (Lat. incido, to cut). Applied to the four front teeth of both jaws, 
 
 which have sharp, cutting edges. 
 
 Incus. An anvil ; the name of one of the bones of the middle ear. 
 Indian Hemp. The common name of Cannabis Indica, an intoxicating 
 
 drug known as hasheesh and by other names in Eastern countries. 
 Inferior Vena Cava. The chief vein of the lower part of the body. 
 Inflammation (Lat. prefix in and flammo, to flame). A redness or swelling 
 
 of any part of the body with heat and pain. 
 Insalivation (Lat. in and saliva, the fluid of the mouth). The mingling of 
 
 the saliva with the food during the act of chewing. 
 Inspiration (Lat. inspire, spiratum, to breathe in). The act of drawing in 
 
 the breath. 
 Intestine (Lat. intus, within). The part of the alimentary canal which is 
 
 continuous with the lower end of the stomach; also called the bowels. 
 Iris (Lat. iris, the rainbow). The thin, muscular ring which lies between 
 
 the cornea and crystalline lens, giving the eye its special color. 
 
 Jaundice (Fr. jaunisse, yellow). A disorder in which the skin and eyes 
 assume a yellowish tint. 
 
 Katabolism (Gr. Karct/SdXXw, to throw down). The process by means of 
 which the more complex elements are rendered more simple and less 
 complex. The opposite of anabolism. 
 
 Labyrinth. The internal ear, so named from its many windings. 
 Lacrymal Apparatus (Lat. lacryma, a tear). The organs for forming and 
 carrying away the tears. 
 
GLOSSARY. 43 1 
 
 Lacteals (Lat. lac, lactis, milk). The absorbent vessels of the small 
 intestines. 
 
 Laryngoscope (Gr. \dpvy, larynx, and aKoirtu, to behold). An instrument 
 consisting of a mirror held in the throat, and a reflector to throw light 
 on it, by which the interior of the larynx is brought into view. 
 
 Larynx. The cartilaginous tube situated at the top of the windpipe. 
 
 Lens. Literally, a lentil ; a piece of transparent glass or other substance 
 so shaped as either to converge or disperse the rays of light. 
 
 Ligament (Lat. ligo y to bind). A strong, fibrous material binding bones or 
 other solid parts together. 
 
 Ligature (Lat. ligo, to bind). A thread of some material used in tying a 
 cut or injured artery. 
 
 Lobe. A round, projecting part of an organ, as of the liver, lungs, or brain. 
 
 Lymph (Lat. lympha, pure water). The watery fluid conveyed by the lym- 
 phatic vessels. 
 
 Lymphatic Vessels. A system of absorbent vessels. 
 
 Malleus. Literally, the mallet ; one of the small bones of the middle ear. 
 
 Marrow. The soft, fatty substance contained in the cavities of bones. 
 
 Mastication (Lat. mastico, to chew). The act of cutting and grinding the 
 food to pieces by means of the teeth. 
 
 Meatus (Lat. meo, meatum, to pass). A. passage or canal. 
 
 Medulla Oblongata. The " oblong marrow " ; that portion of the brain 
 which lies upon the basilar process of the occipital bone. 
 
 Meibomian. A term applied to the small glands between the conjunctiva 
 and tarsal cartilages, discovered by Meibomius. 
 
 Membrana Tympani. Literally, the membrane of the drum ; a delicate 
 partition separating the outer from the middle ear; it is sometimes 
 popularly called "the drum of the ear." 
 
 Membrane. A thin layer of tissue serving to cover some part of the body. 
 
 Mesentery (Gr. /u&ros, middle, and evrepov, the intestine). A duplicature of 
 the peritoneum covering the small intestine, which occupies the middle 
 or center of the abdominal cavity. 
 
 Metabolism (Gr. ^eTa/SoXiy, change). The changes taking place in cells, 
 whereby they become more complex and contain more force, or less com- 
 plex and contain less force. The former is constructive metabolism, 
 or anabolism ; the latter, destructive metabolism, or katabolism . 
 
 Microbe (Gr. /juKpbs, little, and filos, life). A microscopic organism, particu- 
 larly applied to bacteria. 
 
 Microscope (Gr. /MKp6s, small, and (T/COTT^W, to look at). An optical instru- 
 ment which assists in the examination of minute objects. 
 
43 2 GLOSSARY. 
 
 Molar (Lat. mola, a mill). The name applied to the three back teeth at 
 
 each side of the jaw ; the grinders, or mill-like teeth. 
 Molecule (dim. of Lat. moles, a mass). The smallest quantity into which 
 
 the mass of any substance can physically be divided. A molecule may 
 
 be chemically separated into two or more atoms. 
 Morphology (Gr. /u,6/>0?7, form, and \6-yos, discourse). The study of the laws 
 
 of form or structure in living beings. 
 
 Motor (Lat. moveo, motum, to move). The name of the nerves which con- 
 duct to the muscles the stimulus which causes them to contract. 
 Mucous Membrane. The thin layer of tissue which covers those internal 
 
 cavities or passages which communicate with the external air. 
 Mucus. The glairy fluid secreted by mucous membranes. 
 Myopia (Gr. /Atfw, to shut, and w^, the eye). A defect of vision dependent 
 
 upon an eyeball that is too long, rendering distant objects indistinct ; 
 
 near sight. 
 Myosin (Gr. /xus, muscle). Chief proteid substance of muscle. 
 
 Narcotic (Gr. rapccctw, to benumb). A medicine which, in poisonous doses, 
 produces stupor, convulsions, and sometimes death. 
 
 Nerve Cell. A minute round and ashen-gray cell found in the brain and 
 other nervous centers. 
 
 Nerve Fiber. An exceedingly slender thread of nervous tissue. 
 
 Nicotine. The poisonous and stupefying oil extracted from tobacco. 
 
 Nostril (Anglo-Saxon nosu, nose, and thyrl, a hole). One of the two outer 
 openings of the nose. 
 
 Nucleolus (dim. of nucleus). A little nucleus. 
 
 Nucleus (Lat. nux, a nut). A central part of any body, or that about which 
 matter is collected. In anatomy, a cell within a cell. 
 
 Nutrition (Lat. nutrio, to nourish). The processes by which the nourish- 
 ment of the body is accomplished. 
 
 Odontoid (Gr. 65ous, a tooth, eTSos, shape). The name of the bony peg of 
 
 the second vertebra, around which the first turns. 
 (Esophagus. Literally, that which carries food. The tube leading from 
 
 the throat to the stomach ; the gullet. 
 Olecranon (Gr. u\vq, the elbow, and Kpavlov, the top of the head). A 
 
 curved eminence at the upper and back part of the ulna. 
 Olfactory (Lat. olfacio, to smell). Pertaining to the sense of smell. 
 Optic (Gr. <57rretfo;, to see). Pertaining to the sense of sight. 
 Orbit (Lat. orbis, a circle). The bony socket or cavity in which the eyeball 
 
 is situated. 
 
GLOSSARY. 433 
 
 Organ (Lat. organum, an instrument or implement). A portion of the 
 body having some special function or duty. 
 
 Osmosis (Gr. oJ<r/>t6s, impulsion). Diffusion of liquids through membranes. 
 
 Ossa Innominata, pi. of Os Innominatum (Lat.). " Unnamed bones." 
 The irregular bones of the pelvis, unnamed on account of their non- 
 resemblance to any known object. 
 
 Otoconia (Gr. o5s, an ear, and Kovia, dust). Minute crystals of lime in the 
 vestibule of the ear ; also known as otoliths. 
 
 Palate (Lat. palatum, the palate). The roof of the mouth, consisting of the 
 
 hard and soft palate. 
 Palpitation (Lat. palpitatio, a frequent or throbbing motion). A violent 
 
 and irregular beating of the heart. 
 
 Papilla. The small elevations found on the skin and mucous membranes. 
 Paralysis (Gr. TrapaXtfw, to loosen ; also, to disable). Loss of function, 
 
 especially of motion or feeling. Palsy. 
 
 Parasite. A plant or animal that grows or lives on another. 
 Pelvis. Literally, a basin. The bony cavity at the lower part of the trunk. 
 Pepsin (Gr. TT^TTTW, to digest). The active principle of the gastric juice. 
 Pericardium (Gr. TTC/O/, about, and Kapdia, heart). The sac enclosing the 
 
 heart. 
 
 Periosteum (Gr. irepi, around, 6<TTtov, a bone). A delicate fibrous mem- 
 brane which invests the bones. 
 Peristaltic Movements (Gr. irept, round, and o-rAXa;, to send). The slow, 
 
 wave-like movements of the stomach and intestines. 
 Peritoneum (Gr. Tre/oire^w, to stretch around). The investing membrane 
 
 of the stomach, intestines, and other abdominal organs. 
 Perspiration (Lat. perspiro, to breathe through). The sweat. 
 Petrous (Gr. ir^rpa, a rock). The name of the hard portion of the temporal 
 
 bone, in which are situated the drum of the ear and labyrinth. 
 Phalanges (Gr. (f>d\ayj-, a body of soldiers closely arranged in ranks and 
 
 files). The bones of the fingers and toes. 
 Pharynx (Gr. (pdpvyZ, the throat). The cavity between the back of the 
 
 mouth and the gullet. 
 Physiology (Gr. 0&m, nature, and \6yos, a discourse). The science of the 
 
 functions of living, organized beings. 
 Pia Mater (Lat.). Literally, the tender mother ; the innermost of the three 
 
 coverings of the brain. It is thin and delicate ; hence the name. 
 Pinna (Lat. a feather or wing). External cartilaginous flap of the ear. 
 Plasma (Gr. 7rXd<ra-a>, to mould). Anything formed or moulded. The 
 
 liquid part of the blood. 
 
434 GLOSSARY. 
 
 Pleura (Gr. -irXevpd, the side, also a rib). A membrane covering the lung, 
 and lining the chest. 
 
 Pleurisy. An inflammation affecting the pleura. 
 
 Pneumogastric (Gr. irvetuwv, the lungs, and yourr-rip, the stomach). The 
 chief nerve of respiration ; also called the vagus, or wandering nerve. 
 
 Pneumonia. An inflammation affecting the air cells of the lungs. 
 
 Poison (Fr. poison). Any substance, which, when applied externally, or 
 taken into the stomach or the blood, works such a change in the animal 
 economy as to produce disease or death. 
 
 Pons Varolii. Bridge of Varolius. The white fibers which form a bridge 
 connecting the different parts of the brain, first described by Varolius. 
 
 Popliteal (Lat. poples, poplitis, the ham, the back part of the knee). The 
 space behind the knee joint is called the popliteal space. 
 
 Portal Vein (Lat. porta, a gate). The venous trunk formed by the veins 
 coming from the intestines. It carries the blood to the liver. 
 
 Presbyopia (Gr. irpfopvs, old, and aty, the eye). A defect of the accommo- 
 dation of the eye, caused by the hardening of the crystalline lens ; the 
 " far sight " of adults and aged persons. 
 
 Process (Lat. procedo, processus, to proceed, to go forth). Any projection 
 from a surface ; also, a method of performance ; a procedure. 
 
 Pronation (Lat. pronus, inclined forwards). The turning of the hand with 
 the palm downwards. 
 
 Pronator. The group of muscles which turn the hand palm downwards. 
 
 Proteids (Gr. Trpwroj, first, and efSos, form). A general term for the albu- 
 minoid constitutents of the body. 
 
 Protoplasm (Gr. Trpwros first, and TrXtWco, to form). A first-formed organ- 
 ized substance ; primitive organic cell matter. 
 
 Pterygoid (Gr. irrtpwv, a wing, and e?5os, form, resemblance). Wing- 
 like. 
 
 Ptomaine (Gr. Trrw/xa, a dead body). One of a class of animal bases or 
 alkaloids formed in the putrefaction of various kinds of albuminous 
 matter. 
 
 Ptyalin (Gr. <rla\ov, saliva). A ferment principle in saliva, having power to 
 convert starch into sugar. 
 
 Pulse (Lat. pello, pulsum, to beat). The throbbing of an artery against the 
 finger, occasioned by the contraction of the heart. Commonly felt at 
 the wrist. 
 
 Pupil (Lat. pupilla}. The central, round opening in the iris, through which 
 light passes into the interior of the eye. 
 
 Pylorus (Gr. irv\ovp6s, a gate-keeper). The lower opening of the stomach, 
 at the beginning of the small intestine. 
 
GLOSSARY. 43 5 
 
 Reflex (Lat. reflexus, turned back). The name given to involuntary move- 
 ments produced by an excitation traveling along a sensory nerve to a 
 center, where it is turned back or reflected along motor nerves. 
 
 Renal (Lat. ren, rents, the kidney). Pertaining to the kidneys. 
 
 Respiration (Lat. respiro, to breathe frequently). The function of breath- 
 ing, comprising two acts, inspiration, or breathing in, and expiration, 
 or breathing out. 
 
 Retina (Lat. rete, a net). The innermost of the three tunics, or coats, of 
 the eyeball, being an expansion of the optic nerve; 
 
 Rima Glottidis (Lat. rima, a chink or cleft). The opening of the glottis. 
 
 Saccharine (Lat. saccharum, sugar). The group of food substances which 
 embraces the different varieties of sugar, starch, and gum. 
 
 Saliva. The moisture, or fluids, of the mouth, secreted by the salivary 
 glands ; the spittle. 
 
 Sarcolemma (Gr. <rdpt-, flesh, and Xfy^a, a husk). The membrane which 
 surrounds the contractile substance of a striped muscular fiber. 
 
 Sclerotic (Gr. tr/cX^s, hard). The tough, fibrous, outer coat of the eyeball. 
 
 Scurvy. Scorbutus, a disease of the general system, having prominent 
 skin symptoms. 
 
 Sebaceous (Lat. sebum, fat). Resembling fat ; the name of the oily secre- 
 tion by which the skin is kept flexible and soft. 
 
 Secretion (Lat. secerno, secretum, to separate). The process of separating 
 from the blood some essential, important fluid; which fluid is also 
 called a secretion. 
 
 Semicircular Canals. Three canals in the internal ear. 
 
 Sensation. The perception of an external impression by the nervous 
 system. 
 
 Serum. The clear, watery fluid which separates from the clot of the blood. 
 
 Spasm (Gr. o-7rao-/i6s, convulsion). A sudden, violent, and involuntary con- 
 traction of one or more muscles. 
 
 Special Sense. A sense by which we receive particular sensations, such 
 as those of sight, hearing, taste, and smell. 
 
 Sputum, pi. Sputa (Lat. spuo, sputum, to spit). The matter which is 
 coughed up from the air passages. 
 
 Stapes. Literally, a stirrup ; one of the small bones of the middle ear. 
 
 Stimulant (Lat. stimulo, to prick or goad on). An agent which causes an 
 increase of vital activity in the body or in any of its parts. 
 
 Striated (Lat. strio, to furnish with channels). Marked with fine lines. 
 
 Styptics (Gr. 0-TU7TTt/c6s, astringent). Substances used to produce a contrac- 
 tion or shrinking of living tissues. 
 
436 GLOSSARY. 
 
 Subclavian Vein (Lat. sub, under, and clavis, a key). The great vein 
 
 bringing back the blood from the arm and side of the head ; so called 
 
 because it is situated underneath the clavicle, or collar bone. 
 Superior Vena Cava (Lat., upper hollow vein). The great vein of the 
 
 upper part of the body. 
 Suture (Lat. sutura, a seam). The union of certain bones of the skull by 
 
 the interlocking of jagged edges. 
 Sympathetic System of Nerves. A double chain of nervous ganglia, 
 
 situated chiefly in front of, and on each side of, the spinal column. 
 Symptom (Gr. <r6v, with, and TT^TTTW, to fall). A sign or token of 
 
 disease. 
 Synovial (Gr. o-tfj/, with, and w6j>, an egg). The liquid which lubricates the 
 
 joints ; joint-oil. It resembles the white of a raw egg. 
 System. A number of different organs, of similar structures, distributed 
 
 throughout the body and performing similar functions. 
 Systemic. Belonging to the system, or body, as a whole. 
 Systole (Gr. o-uo-rAXw, to contract). The contraction of the heart, by which 
 
 the blood is expelled from that organ. 
 
 Tactile (Lat. tactus, touch). Relating to the sense of touch. 
 
 Tartar. A hard crust which forms on the teeth, and is composed of sali- 
 vary mucus, animal matter, and a compound of lime. 
 
 Temporal (Lat. tempus, time, and tempora, the temples). Pertaining to the 
 temples ; so called because the hair begins to turn white with age in 
 that portion of the scalp. 
 
 Tendon (Lat. tendo, to stretch). The white, fibrous cord, or band, by 
 which a muscle is attached to a bone ; a sinew. 
 
 Tetanus (Gr. relva, to stretch). A disease marked by persistent contrac- 
 tions of all or some of the voluntary muscles ; those of the jaw are 
 sometimes solely affected ; the disorder is then termed lockjaw. 
 
 Thorax (Gr. 0ct>pa, a breast-plate). The upper cavity of the trunk of the 
 body, containing the lungs, heart, etc. ; the chest. 
 
 Thyroid (Gr. %>>*, a shield, and eI5os, form). The largest of the carti- 
 lages of the larynx : its projection in front is called " Adam's Apple." 
 
 Tissue. Any substance or texture in the body formed of various elements, 
 such as cells, fibers, blood-vessels, etc., interwoven with each other. 
 
 Tobacco (Indian tabaco, the tube, or pipe, in which the Indians smoked the 
 plant). A plant used for smoking and chewing, and in snuff. 
 
 Trachea (Gr. Tpa-xjfe, rough). The windpipe. 
 
 Tragus (Gr. rpdyos, a goat). The eminence in front of the opening of the 
 ear ; sometimes hairy, like a goat's beard. 
 
GLOSSARY. 437 
 
 Transfusion (Lat. trans/undo, to pour from one vessel to another). The 
 operation of injecting blood taken from one person into the veins of 
 another. 
 
 Trichina Spiralis. (A twisted hair). A minute species of parasite, or 
 worm, which infests the flesh of the hog : may be introduced into the 
 human system by eating pork not thoroughly cooked. 
 
 Trochanter (Gr. rpoxdw, to turn, to revolve). Name given to two projec- 
 tions on the upper extremities of the femur, which give attachment to 
 the rotator muscles of the thigh. 
 
 Trypsin. The ferment principle in pancreatic juice, which converts proteid 
 material into peptones. 
 
 Tubercle (Lat. tuber, a bunch). A pimple, swelling, or tumor. A morbid 
 product occurring in certain lung diseases. 
 
 Tuberosity (Lat. tuber, tuberis, a swelling). A protuberance. 
 
 Turbinated (Lat. turbinatus, from turbo, turbinis, a top). Formed like a 
 top ; a name given to the bones in the outer wall of the nasal fossae. 
 
 Tympanum (Gr. Ttjuiravov, a drum). The cavity of the middle ear, resem- 
 bling a drum in being closed by two membranes. 
 
 Umbilicus (Lat., the navel.) A round cicatrix or scar in the median line of 
 
 the abdomen. 
 Urea (Lat. urina, urine). Chief solid constitutent of urine. Nitrogenous 
 
 product of tissue decomposition. 
 Ureter (Gr. oup^w, to pass urine). The tube through which the urine is 
 
 conveyed from the kidneys to the bladder. 
 Uvula (Lat. uva, a grape). The small, pendulous body attached to the 
 
 back part of the palate. 
 
 Vaccine Virus (Lat. vacca, a cow, and virus, poison). The material 
 derived from heifers for the purpose of vaccination, the great pre- 
 ventive of smallpox. 
 
 Valvulae Conniventes. A name given to transverse folds of the mucous 
 membrane in the small intestine. 
 
 Varicose (Lat. varix, a dilated vein). A distended or enlarged vein. 
 
 Vascular (Lat. vasculum, a little vessel). Pertaining to or possessing 
 blood or lymph vessels. 
 
 Vaso-motor (Lat. vas, a vessel, and moveo, motum, to move). Causing 
 motion to the vessels. Vaso-motor nerves cause contraction and relaxa- 
 tion of the blood-vessels. 
 
 Venae Cavae, pi. of Vena Cava. " Hollow veins." A name given to the 
 two great veins of the body which meet at the right auricle of the heart. 
 
43 8 GLOSSARY. 
 
 Venous (Lat. vena, a vein). Pertaining to, or contained within, a vein. 
 Ventilation. The introduction of fresh air into a room or building in such 
 
 a manner as to keep the air within it in a pure condition. 
 Ventral (Lat. venter, ventris, the belly). Belonging to the abdominal or 
 
 belly cavity. 
 
 Ventricles of the Heart. The two largest cavities of the heart. 
 Vermiform (Lat. vermis, a worm, and forma, form). Worm-shaped. 
 Vertebral Column (Lat. vertebra, a joint). The backbone ; also called the 
 
 spinal column and spine. 
 
 Vestibule. A portion of the internal ear, communicating with the semi- 
 circular canals and the cochlea ; so called from its fancied resemblance 
 
 to the vestibule, or porch, of a house. 
 Villi (Lat. villus, shaggy hair). Minute, thread-like projections upon the 
 
 internal surface of the small intestine, giving it a velvety appearance. 
 Virus (Lat., poison). Foul matter of an ulcer ; poison. 
 Vital Knot. A part of the medulla oblongata, the destruction of which 
 
 causes instant death. 
 Vitreous (Lat. vitrum, glass). Having the appearance of glass ; applied to 
 
 the humor occupying the largest part of the cavity of the eyeball. 
 Vivisection (Lat. vivus, alive, and seco, to cut). The practice of operating 
 
 upon living animals, for the purpose of studying some physiological 
 
 process. 
 Vocal Cords. Two elastic bands or ridges situated in the larynx ; the 
 
 essential parts of the organ of voice. 
 
 Zygoma (Gr. vyt>v, a yoke). The arch formed by the malar bone and 
 the zygomatic process of the temporal bone. 
 
INDEX. 
 
 Absorption . . . . 144 
 
 from mouth and stomach 145 
 
 by the intestines . .145 
 
 Accident and emergencies . 367 
 
 Achilles, Tendon of . 43, 65 
 
 Air, made impure by breathing 221 
 
 Foul, effect of, on health 222 
 
 Alcohol, Effect of, on bones 53 
 
 Effect of, on muscles . 72 
 
 Effect of, on muscular 
 
 tissue . . . . 73 
 Effect of, on physical cul- 
 ture . . . -95 
 Nature of . . .112 
 Effects of, on human sys- 
 tem . . . .114 
 and digestion . . . 159 
 Effect of, on the stomach 160 
 and the gastric juice . 161 
 Final results on digestion 162 
 Effects of, on the liver . 163 
 Fatty degeneration due to 164 
 Effect of, on the circula- 
 tion .... 193 
 Effect of, on the heart . 195 
 Effect of, on the blood- 
 vessels . . . .195 
 Effect of, on the lungs . 230 
 Other results of, on lungs 231 
 Effect of, on disease . 232 
 Effect of, on kidneys . 261 
 
 Alcohol, as cause of Blight's 
 
 disease . . . 262 
 
 and the brain . . . 294 
 
 How, injures the brain . 295 
 
 Why brain suffers from . 296 
 
 the enemy of brain work 296 
 Other physical results 
 
 of .... 297 
 
 Diseases produced by . 298 
 Mental and moral ruin 
 
 by .... 298 
 
 Evil results of, inherited . 299 
 Effect of, on taste . -317 
 
 Effect of, on the eye . 340 
 Effect of, on throat and 
 
 voice .... 365 
 
 Alcoholic beverages . . 1 1 1 
 Alcoholic fermentation and 
 
 Bacteria . . . 399 
 
 Anabolism denned . . . 13 
 
 Anatomy defined ... 4 
 
 Antidotes for poisons . . 393 
 
 Antiseptics .... 400 
 
 Apparatus, Question of . . 406 
 
 Arm, Upper .... 36 
 
 Arteries 180 
 
 Astigmatism .... 332 
 Asphyxia . . . .381 
 Atlas and axis ... 34 
 Atmosphere, how made im- 
 pure .... 220 
 
440 
 
 INDEX. 
 
 Bacteria, Nature of . . 395 
 Bacteria, Struggle for exist- 
 ence of ... 396 
 Importance of, in Nature 397 
 Action of ... 398 
 Battle against . . . 399 
 Baths and bathing . . . 248 
 Bathing, Rules and precautions 2 50 
 Bicycling . . . 91 
 
 Bile 138 
 
 Biology defined ... 4 
 
 Bladder 259 
 
 Bleeding, from stomach . -374 
 
 from lungs . , . 374 
 
 from nose . . -374 
 
 How to stop . . 373, 374 
 
 Blood, Circulation of . 169, 184 
 
 Physical properties of .170 
 
 corpuscles . . -171 
 
 Coagulation of . .172 
 
 Gene ral plan of circulati on 1 74 
 
 Blood-vessels, Nervous control 
 
 of .... 189 
 
 connected with heart . 179 
 
 Effect of alcohol on . 195 
 
 Injuries to . . -372 
 
 Bodies, living, Characters of 2 
 
 Body, General plan of . . 19 
 
 Bone, Chemical composition of 21 
 
 Physical properties of . 23 
 
 Microscopic structure of . 25 
 
 Bones, uses of, The . . 47 
 
 Kinds of . . . -47 
 
 in infancy and childhood 48 
 
 positions at school . . 49 
 
 in after life ... 50 
 
 Broken . . . 51, 379 
 
 broken, Treatment for, 52, 379 
 
 Effect of alcohol on . 53 
 
 Effect of tobacco on . 54 
 
 Breathing, Movements of . 211 
 
 Breathing, Mechanism of 
 Varieties of 
 Nervous control of . 
 change in the air 
 Air, made impure by 
 
 Brain, as a whole . 
 Membranes of 
 as a reflex center 
 
 211 
 
 212 
 2I 3 
 217 
 221 
 268 
 
 273 
 28 4 
 
 Effects of alcohol on 294-297 
 Brain center, Functions of, in 
 perception of impres- 
 sions .... 309 
 Bright's disease caused by al- 
 cohol .... 262 
 Bronchial tubes . . . 205 
 Burns or scalds . . -375 
 
 Capillaries 
 
 Carbohydrates 
 
 Carpus . 
 
 Cartilage 
 
 Hyaline . 
 White fibro- 
 Yellow fibro- 
 Thyroid . 
 Arytenoid 
 Cricoid . 
 
 Cells 
 
 183 
 8, 100 
 
 38 
 . 18 
 . 18 
 . 18 
 . 18 
 
 357 
 
 358 
 
 358 
 
 9 
 
 and the human organism 10 
 
 Kinds of . . . .n 
 
 Vital properties of . . 1 1 
 
 Epithelial . . . 14 
 
 Nerve .... 264 
 
 Cerebrum .... 270 
 
 Cerebellum . . . .271 
 
 Chemical compounds in the 
 
 body .... 6 
 
 Chloral 303 
 
 Chyle 143 
 
 Chyme 132 
 
 Cilia of air passages . . 206 
 
INDEX. 
 
 441 
 
 Circulation . . . .169 
 General plan of . .174 
 Portal . . . .186 
 Pulmonic . . -185 
 
 Systemic . . . .185 
 Effect of alcohol on . 193 
 
 Clavicle 37 
 
 Cleanliness, Necessity for . 247 
 Clothing, Use of . . .252 
 Material used for . . 253 
 Suggestions for use of . 254 
 Effects of tight-fitting . 255 
 Miscellaneous hints on 
 
 use of . . . . 256 
 
 Catching, on fire .' . 376 
 
 Coagulation of blood . .172 
 
 Cocaine, ether, and chloroform 303 
 
 Cochlea of ear ... 346 
 
 Cocoa in 
 
 Coffee -in 
 
 Colon 136 
 
 Color-blindness . . . 336 
 Complemental air . . .210 
 Compounds, Chemical . . 6 
 Organic .... 7 
 Condiments .... 109 
 Conjunctiva .... 334 
 Connective tissue . . 1 5 
 
 Consonants .... 362 
 Contagious diseases . . 390 
 Contraction, Object of . -63 
 Contusions and bruises . . 369 
 Convulsions .... 380 
 
 Cooking 115 
 
 Coughing . . .220 
 
 Cornea 323 
 
 Corpuscles, Blood . . -171 
 
 Red 171 
 
 Colorless. . . -171 
 Corti, Organ of ... 346 
 Cranial Nerves . . . 275 
 
 Cranium, Bones of 27 
 
 Crying . . . .219 
 
 Crystalline lens . . . 326 
 
 Cuticle 238 
 
 Cutis vera, or true skin . . 237 
 
 Degeneration, Fatty, due to . 
 
 alcohol . . .164 
 
 Deglutition, or swallowing . 128 
 
 Deodorants . . . .401 
 
 Diet, Important articles of . 103 
 
 Effect of occupation on 151 
 
 Too generous . . .151 
 
 Effect of climate on -152 
 
 Digestion, Purpose of . . 119 
 
 General plan of . .121 
 
 in small intestines . -143 
 
 in large intestines . -144 
 
 Effect of alcohol on 159-162 
 
 Disease, Effect of alcoholics 
 
 upon .... 232 
 Diseases, infectious and con- 
 tagious, Management of 402 
 Care of . . . . 390 
 Hints on nursing . . 390 
 Disinfectants . . . .401 
 Air and water as . .401 
 How to use . . . 403 
 Dislocations . . . -51 
 Dogs, mad,. Bites of . . 370 
 Drowning, Apparent . -381 
 Methods of treating . 383 
 Sylvester method . . 383 
 Marshall Hall method . 384 
 Duct, Hepatic . . -138 
 Cystic . . . . 139 
 Common bile . . . 139 
 Thoracic . . . .146 
 Nasal .... 334 
 Duodenum . . . -134 
 Dura mater .... 273 
 
442 
 
 INDEX. 
 
 Ear, External . 
 Middle . 
 Bones of the 
 Internal . 
 
 342 
 
 343 
 344 
 345 
 
 Practical hints on care of 349 
 
 Foreign bodies in . -377 
 
 Eating, Practical points about 154 
 
 Eggs as food . . . .104 
 
 Elements, Chemical, in the 
 
 body .... 5 
 
 Epidermis, or cuticle . . 238 
 
 Epiglottis . . . 204, 356 
 
 Epithelium . . . 13 
 
 Squamous . . 14 
 
 Columnar . . .14 
 
 Glandular . . . .14 
 
 Ciliated . . . .14 
 
 EpitheliaF tissues, Functions 
 
 of 15 
 
 Erect position ... 68 
 
 Ethmoid bone ... 28 
 
 Eustachian tube . . . 343 
 
 Excretion .... 235 
 
 Exercise, Physical ... 78 
 
 Importance of . . . 78 
 
 Effect of, on muscles . 80 
 
 Effect of, on important 
 
 organs .... 82 
 Effect of, on personal ap- 
 pearance ... 83 
 Effect of excessive . . 84 
 Amount of, required . 87 
 Time for . . . .89 
 Physical, in school . . 93 
 Practical points about . 94 
 Effect of alcohol and to- 
 bacco on . -95 
 Experiments, Limitations of . 405 
 Value of . . . . 405 
 
 Eye 321 
 
 Inner structure of . -325 
 
 Eye, compared to camera . 327 
 
 Refractive media of -328 
 
 Movements of . . 332 
 
 Foreign bodies in . . 378 
 
 Practical hints on care of 338 
 
 Effect of alcohol on . 340 
 
 Effect of tobacco on -341 
 
 Eyeball, Coats of . . .322 
 
 Eyelids and eyebrows . . 333 
 
 Eyesight in schools . . 336 
 
 Face 
 
 Bones of the . 
 Fainting . 
 Fats . ' . 
 
 and oils . 
 Femur . 
 Fibrin . 
 Fibula . 
 Fish as food . 
 Food and drink 
 Food, why we need it 
 
 29 
 2 9 
 
 380 
 8 
 
 101 
 
 42 
 
 104 
 
 97 
 
 97 
 
 Absorption of, by the 
 
 blood . . . .119 
 Quantity of, as affected 
 
 by age . . . . i 50 
 Kinds of, required . . 152 
 Foods, Classification of . . 99 
 Nitrogenous ... 99 
 Proteid .... 99 
 Saline or mineral . .102 
 Vegetable . . -105 
 Proteid vegetable . -105 
 Non-proteid vegetable . 106 
 Non-pro teid animal . .108 
 Table of . . . . 155 
 Food materials, Table of- . 107 
 Composition of . -103 
 
 Foot 42 
 
 Foul air, Effect of, on health 222 
 Frontal bone .... 27 
 
INDEX. 
 
 443 
 
 Frost bites 
 
 376 
 
 Hiccough .... 
 
 219 
 
 Fruits as food . . 
 
 1 08 
 
 Hip bones .... 
 
 35 
 
 
 
 Histology defined . 
 
 4 
 
 Gall bladder . . . '. 
 
 139 
 
 Humerus .... 
 
 37 
 
 Garden vegetables . 
 
 1 08 
 
 Hygiene defined 
 
 4 
 
 Gastric glands . . 
 
 I3 1 
 
 Hyoid bone . . .36, 
 
 357 
 
 Gastric juice, Effect of alcohol 
 
 
 Hypermetropia 
 
 330 
 
 on .... 
 
 161 
 
 
 
 Glands 
 
 121 
 
 Ileum 
 
 134 
 
 Mesenteric 
 
 146 
 
 Injured, Prompt aid to . 
 
 367 
 
 Lymphatic 
 
 147 
 
 Insalivation .... 
 
 126 
 
 Ductless .... 
 
 148 
 
 Intestine, Small 
 
 *34 
 
 Thyroid .... 
 
 148 
 
 Coats of small 
 
 '35 
 
 Thymus .... 
 
 148 
 
 Large .... 
 
 136 
 
 Suprarenal 
 
 I 49 
 
 Intoxicants, Physical results 
 
 
 Lacrymal 
 
 334 
 
 of .... 
 
 297 
 
 Glottis 
 
 358 
 
 Iris of the eye . - 
 
 326 
 
 Hair 
 
 239 
 
 Jejunum 
 
 134 
 
 Structure of 
 
 240 
 
 Joints . 
 
 44 
 
 Hair and nails, Care of . 
 
 252 
 
 Imperfect 
 
 46 
 
 Hall, Marshall, method for 
 
 
 Perfect .... 
 
 46 
 
 apparent drowning 
 
 384 
 
 Hinge .... 
 
 46 
 
 Hand 
 
 38 
 
 Ball-and-socket 
 
 46 
 
 Haversian canals . 
 
 25 
 
 Pivot .... 
 
 46 
 
 Head and spine, how joined . 
 
 34 
 
 
 
 Head, Bones of ... 
 
 26 
 
 Katabolism denned 
 
 13 
 
 Hearing, Sense of . 
 
 34i 
 
 Kidneys 
 
 257 
 
 Mechanism of . 
 
 347 
 
 Structure of ... 
 
 258 
 
 Effect of tobacco on 
 
 35i 
 
 Function of ... 
 
 258 
 
 Heart 
 
 176 
 
 Action of, how modified 
 
 259 
 
 Valves of . . 
 
 177 
 
 Effect of alcohol on 
 
 261 
 
 General plan of blood- 
 
 
 Kidneys and skin . 
 
 246 
 
 vessels connected with 
 
 179 
 
 
 
 Rhythmic action of . 
 
 187 
 
 Lacrymal apparatus , . 
 
 334 
 
 Impulse and sounds of . 
 
 187 
 
 gland .... 
 
 335 
 
 Nervous control of . 
 
 188 
 
 Lacteals . . . . ' . 
 
 145 
 
 Effect of alcohol on 
 
 r 95 
 
 Landmarks, Bony . 
 
 415 
 
 Effect of tobacco on 
 
 198 
 
 Muscular 
 
 4i7 
 
 Heat, Animal .... 
 
 225 
 
 heart .... 
 
 419 
 
 Sources of ... 
 
 226 
 
 arteries .... 
 
 419 
 
444 
 
 INDEX. 
 
 Larynx . 
 
 Laughing 
 
 Lens, Crystalline . 
 
 Levers in the body 
 
 Life, The process of 
 
 Ligaments 
 
 Limbs, Upper 
 Lower 
 
 Liver . 
 
 Minute structure of 
 Blood supply of 
 Functions of . 
 Effect of alcohol on 
 
 Lungs . 
 
 Minute structure of 
 Capacity of 
 Effect of alcohol on 
 Bleeding from . 
 
 Lymph . 
 
 Lymphatics 
 
 Mad dogs, Bites of 
 Malar bone . 
 Mastication 
 Maxillary, Superior 
 
 Inferior . 
 Meals, Hints about 
 Meats as food 
 Medulla oblongata . 
 Membrane, Synovial 
 
 Serous 
 
 Arachnoid 
 Membranes, Brain . 
 Mesentery 
 Metabolism defined 
 Metacarpal bones . 
 Metatarsal bones . 
 Microscope, Use of 
 Milk . 
 Mineral foods 
 Morphology defined 
 
 357 
 
 Motion in animals . 
 
 57 
 
 219 
 
 Mouth 
 
 122 
 
 326 
 
 Movement, Mechanism of 
 
 66 
 
 67 
 
 Muscles, Kinds of . 
 
 57 
 
 12 
 
 voluntary, Structure of . 
 
 58 
 
 45 
 
 involuntary, Structure of 
 
 59 
 
 36 
 
 Arrangement of 
 
 64 
 
 4i 
 
 Important 
 
 69 
 
 137 
 
 Effect of alcohol on 
 
 72 
 
 137 
 
 Effect of tobacco on 
 
 75 
 
 139 
 
 Review analysis of . 
 
 77 
 
 140 
 
 Rest for . 
 
 86 
 
 163 
 
 Muscular tissue, Effect of al- 
 
 
 206 
 
 cohol on ... 
 
 73 
 
 208 
 
 Changes in ... 
 
 79 
 
 210 
 
 Properties of . . 
 
 60 
 
 2 3 
 
 activity .... 
 
 79 
 
 374 
 
 contraction 
 
 63 
 
 H7 
 
 fatigue .... 
 
 85 
 
 H7 
 
 sense .... 
 
 312 
 
 
 Myopia . . . - . 
 
 330 
 
 370 
 
 
 
 29 
 
 Nails 
 
 241 
 
 122 
 
 Care of . 
 
 252 
 
 29 
 
 Nasal bones .... 
 
 29 
 
 30 
 
 Nerve cells .... 
 
 264 
 
 '53 
 
 fibers .... 
 
 265 
 
 104 
 
 cells and fibers, Function 
 
 
 273 
 
 of .... 
 
 266 
 
 45 
 
 Nerves, Cranial 
 
 275 
 
 176 
 
 Spinal .... 
 
 278 
 
 273 
 
 Motor . . .189, 
 
 279 
 
 273 
 
 Sensory .... 
 
 279 
 
 146 
 
 spinal, Functions of 
 
 279 
 
 '3 
 
 Nervous system, General view 
 
 
 40 
 
 of .... 
 
 263 
 
 43 
 
 compared to telegraph 
 
 
 407 
 
 system .... 
 
 267 
 
 103 
 
 Divisions of 
 
 268 
 
 102 
 
 Effect of alcohol on 
 
 294 
 
 4 
 
 Effect of tobacco on 
 
 35 
 
INDEX. 
 
 445 
 
 Nitrogenous foods . 
 
 99 
 
 Non-proteid vegetable foods . 
 
 1 06 
 
 animal foods . 
 
 108 
 
 Nose, Bleeding from 
 
 374 
 
 Foreign bodies in . 
 
 377 
 
 Occipital bone 
 
 27 
 
 CEsophagus .... 
 
 128 
 
 Opium 
 
 301 
 
 Poisonous effects of 
 
 301 
 
 In patent medicines 
 
 302 
 
 Victim of the, habit 
 
 302 
 
 Organic compounds 
 
 7 
 
 Outdoor games 
 
 9i 
 
 Oxidation ... 98, 
 
 226 
 
 Pain, Sense of ... 
 
 313 
 
 Palate bones .... 
 
 29 
 
 Pancreas .... 
 
 141 
 
 Pancreatic juice 
 
 142 
 
 Parietal bones 
 
 27 
 
 Patella . . . . 
 
 42 
 
 Pepsin 
 
 132 
 
 Pericardium .... 
 
 176 
 
 Periosteum .... 
 
 25 
 
 Peritoneum .... 
 
 '35 
 
 Phalanges . . . 40, 43 
 
 Pharynx and oesophagus 
 
 128 
 
 Physical exercise . 
 
 78 
 
 Physical education in school . 
 
 92 
 
 Physical exercises in school . 
 
 93 
 
 Physiology defined . 
 
 4 
 
 Study of . 
 
 i 
 
 what it should teach 
 
 2 
 
 Main problems of, briefly 
 
 
 stated .... 
 
 3 
 
 Physiological knowledge, 
 
 
 Value of ... 
 
 5 
 
 Pia mater .... 
 
 273 
 
 Pneumogastric nerve . 189, 
 
 276 
 
 Poisons 
 
 39 1 
 
 Poisons, Table of . . . 393 
 
 Antidotes for . . . 393 
 
 Practical points about . 394 
 
 Poisoning, Treatment of . 392 
 
 Portal circulation . . . 186 
 
 Portal vein . . . .138 
 
 Presbyopia .... 330 
 
 Pressure, Where to apply . 373 
 
 Proteids . . . . . 8, 99 
 
 Proteid vegetable foods . . 105 
 
 Protoplasm .... 8 
 
 Pulmonary artery . . . 179 
 
 veins .... 180 
 
 Pulmonary infection . . 222 
 
 Pulse 192 
 
 Pupil of the eye . . . 323 
 
 Radius 38 
 
 Receptaculum chyli . .146 
 
 Rectum 136 
 
 Reflex centers . . .282 
 in the brain . . . 284 
 Reflex action, Importance of . 284 
 Renal secretion . . .259 
 Residual air . . . .210 
 Respiration, Nature and object 
 
 of 202 
 
 Nervous control of . . 213 
 Effect of, on the blood . 215 
 Effect of, on the air .216 
 Modified movements of . 218 
 Effect of alcohol on -230 
 Effect of tobacco on . 232 
 artificial, Methods of . 383 
 Rest, for the muscles . . 86 
 Need of . . . .288 
 Benefits of ... 289 
 The Sabbath, a day of . 290 
 of mind and body . . 389 
 
 Retina 324 
 
 Ribs and sternum ... 34 
 
446 
 
 INDEX. 
 
 Saline or mineral foods . .102 
 Saliva . . . . .127 
 Salt as food . . . .109 
 Salts, Inorganic, in the body . 7 
 Scalds or burns . . -375 
 
 Scapula 36 
 
 School, Physical eduation in . 93 
 
 Positions at . -49 
 
 School and physical education 92 
 
 Secretion . . . .121 
 
 Semicircular canals . . 346 
 
 Sensations, General . . 307 
 
 Sensation, Conditions of . 309 
 
 Sense, Organs of . . -310 
 
 Sense organ, The essentials of 308 
 
 Serous membranes . . .176 
 
 Sick-room, Arrangement of . 386 
 
 Ventilation of . . -387 
 
 Hints for ... 387 
 
 Rules for . . .388 
 
 Sighing 219 
 
 Sight, Sense of ... 320 
 Skating, swimming, and row- 
 ing . . .90 
 Skeleton . . . .21 
 Review analysis of . 56 
 Skeleton and manikin, Use of 408 
 Skin, The . . . -236 
 regulating temperature . 244 
 Action of, how modified . 244 
 Absorbent powers of . 246 
 and the kidneys . . 246 
 
 Skull 26 
 
 Sutures of . -3 
 
 Sleep, a periodical rest . . 290 
 Effect of, on bodily func- 
 tions .... 291 
 Amount of, required . 292 
 Practical rules about . 292 
 
 Smell 317 
 
 Sense of . . . .318 
 
 Sneezing .... 220 
 
 Snoring 219 
 
 Sobbing 219 
 
 Special senses . . . 307 
 
 Speech 361 
 
 Sphenoid bone ... 27 
 
 Spinal column . . 31 
 
 Spinal cord . . .32, 277 
 
 Structure of . . 277 
 
 Functions of . . . 279 
 
 conductor of impulses . 280 
 
 as a reflex center . .282 
 
 Spinal nerves .... 278 
 
 Functions of . . . 279 
 
 Spleen 148 
 
 Sprains and dislocations . 51 
 Stammering .... 363 
 Starches and sugars . .100 
 
 Sternum 35 
 
 Stomach . . . .129 
 
 Coats of . . . . 131 
 
 Digestion in . -132 
 
 Effect of alcohol on .160 
 
 - Bleeding from . . 374 
 
 Strabismus . . . -333 
 
 Stuttering .... 364 
 
 Sunstroke . . . -385 
 
 Supplemental air . . .210 
 
 Suprarenal capsules . . 149 
 
 Sutures of skull ... 30 
 
 Sweat glands .... 242 
 
 Sweat, Nature of . . . 243 
 
 Sylvester method for apparent 
 
 drowning . . . 383 
 
 Sympathetic system . 189, 286 
 
 Functions of . . . 286 
 
 Synovial membrane . . 45 
 
 sheaths and sacs . ' . 66 
 
 Taste, Organ of 
 Sense of . 
 
 313- 
 3*4 
 
INDEX. 
 
 447 
 
 Taste, Physiological condi- 
 tions of . . . 315 
 Modifications of the sense 317 
 Effect of alcohol on -31? 
 Effect of tobacco on . 317 
 Tea . . . . .in 
 Tear gland and tear passages 334 
 
 Tears 335 
 
 Technical terms denned . 3 
 
 Teeth . . . . .123 
 
 Development of . .124 
 
 Structure of . .124 
 
 Proper care of . . 1 57 
 
 Hints about saving . -158 
 
 Temperature, Regulation of 
 
 bodily .... 227 
 
 Skin as a regulator of . 228 
 
 Voluntary regulation of . 229 
 
 Sense of . . . -312 
 
 Temporal bones ... 27 
 
 Tendon of Achilles . 43, 65 
 
 Tendons . . . , . 65 
 
 Thigh 41 
 
 Thoracic duct . . . .146 
 
 Throat 356 
 
 Care of . . . . 364 
 
 Effect of alcohol on . 365 
 
 Effect of tobacco on . 365 
 
 Foreign bodies in . -377 
 
 Thymus gland . . .148 
 
 Thyroid gland . . .148 
 
 Tibia 42 
 
 Tidal air .... 210 
 
 Tissue, White fibrous . . 16 
 
 Connective . . 15 
 
 Yellow elastic . . -17 
 
 Areolar . . . -17 
 
 Adipose . . . .18 
 
 Adenoid . . . .18 
 
 Muscular ... 60 
 
 Tissues, Epithelial . . 14 
 
 Tissues, epithelial, Varieties of 14 
 
 Functions of . . . 15 
 Connective . . .16 
 
 Tobacco, Effect of, on bones 54 
 
 Effect of, on muscles . 75 
 Effect of, on physical 
 
 culture . . -95 
 
 Effect of, on digestion . 165 
 
 Effect of, on the heart . 198 
 
 Effect of, on the lungs . 232 
 Effect of, on the nervous 
 
 system .... 305 
 
 Effect of, on the mind . 305 
 
 Effect of, on the character 305 
 
 Effect of, on taste . . 317 
 
 Effect of, on hearing . 351 
 Effect of, on throat and 
 
 voice .... 365 
 
 Touch, Organ of . . . 310 
 
 Sense of . . . . 311 
 
 Trachea 203 
 
 Trunk, Bones of . -30 
 
 Tympanum, Cavity of . . 343 
 
 Ulna .... 
 Urine .... 
 
 Valve, Mitral 
 Valves of the heart 
 Valves, Tricuspid . 
 
 Semilunar 
 Vegetable foods 
 Veins .... 
 Ventilation 
 
 Conditions of efficient 
 
 of sick-room . 
 Vestibule of ear 
 Vermiform appendix 
 Vision, Common defects of 
 
 Effect of tobacco on 
 Vivisection and dissection 
 
 259 
 
 178 
 177 
 178 
 179 
 
 *5 
 
 182 
 223 
 224 
 
 387 
 
 345 
 136 
 329 
 34i 
 408 
 
448 
 
 INDEX. 
 
 Vocal cords . . . . .358 
 
 Voice, Mechanism of . -359 
 
 Factors in the production 
 
 of .... 360 
 
 Care of . . . . 364 
 
 Effect of alcohol on -365 
 
 Effect of tobacco on . 365 
 
 Vowel sounds . . . 362 
 
 Walking, jumping, and run- 
 ning .... 89 
 
 Waste and repair ... 97 
 
 Waste material, Nature of . 98 
 Waste products, Elimination 
 
 of .... 235 
 Water as food . . 102,110 
 Whispering . . . . . 363 
 Wounds, Incised and lacera- 
 ted .... 368 
 
 Yawning 
 
 219 
 
n 
 
451.362 
 
 UNIVERSITY OF CALIFORNIA LIBRARY