COLUMBIA LIBRARIES OFFSITF. HEALTH SCIENCES STANDARD HX64089584 QP34 .T67 The essentials of an A ; >.av OOLOGY ANB'HYGIEN COLUMBIA UNIVERSITY DEPARTMENT OF PHYSIOLOGY THE JOHN" G. CURTIS LIBRARY Digitized by the Internet Archive in 2010 with funding from Columbia University Libraries http://www.archive.org/details/essentialsofanatOOtrac APPLETONS' SCIENCE TEXT-BOOKS. ANATOMY, PHYSIOLOGY, AND HYGIENE. General Plan of the Circulation. ^pplctons' Srimtt Ctti-Jtoohs. THE ESSENTIALS OF ANATOMY, PHYSIOLOGY, AND HYGIENE. A TEXT-BOOK FOR SCHOOLS AND ACADEMIES. BY ROGER S. TRACY, M. D., SANITARY INSPECTOR OF THE NEW YORK CITY HEALTH DEPARTMENT J AUTHOR OF "HAND-BOOK OF SANITARY INFORMATION FOR HOUSEHOLDERS." NEW YORK: D. APPLETON AND COMPANY, I, 3, AND 5 BOND STREET. 1884. I Copyright, 1884, By D. APPLETON AND COMPANY. PREFACE. It has been my aim in preparing this volume to compress within the narrowest space such a clear and intelligible account of the structures, activities, and care of the human system as is essential for the purposes of general education. I have also sought to present the facts and principles of the subject in such a natural order as will best subserve the true ends of scientific education. Useful books of in- formation upon physiology are already numerous, but they are too generally deficient in making the science valuable as a means of mental training. Of course, the great object of physiology is to teach how to preserve health, but this is not best done by merely memorizing rules. The rules must be sup- ported by reasons, and if there is not some thorough understanding of the mechanism and powers of the human body, such as will task the efforts of the student, the real fruits of knowledge will not be gained. I have accordingly given prominence to the anatomical and physiological facts which are necessary preliminaries to instruction in hygiene, and in the reasonings upon these facts I have aimed to attract and interest the pupil, to teach him some- thing of the scientific methods of approaching the vi PREFACE. subject, and to connect new acquisitions logically with those already gained, so that the knowledge of the subject may become, as it were, organized into faculty in the minds of the students. So im- portant has it seemed to me to impress deeply upon the pupil's mind the laws of connection and depend- ence among the various parts of the living system that I have thought it best to present this view, in outline, at the very outset. I have, therefore, pre- fixed to the volume a General Analysis, which, while it serves as a table of contents, is interspersed with running comments explaining the general re- lations of the different organs and processes, and I recommend that this analysis be carefully read by the pupil, so that he may become familiar with its argument before proceeding to the detailed study of the text. One of the greatest modern reforms in scientific study is undoubtedly that which makes it more and more objective, so that the student shall con- stantly confirm the knowledge he gets from the book by reference, as far as possible, to the objects themselves, making his acquaintance with them direct, and his information real. The various sci- ences lend themselves to this mode of study in different degrees ; chemistry and physics favoring experiment, and botany offering systematic obser- vation more than any other scientific subjects. Physiology is less favorable to the objective method. For the purpose of ordinary education, it must be chiefly taught from the book, with such accompani- ments of lectures and illustrations by charts as the circumstances will allow. But even here much may be done to give the pupil more correct ideas of the PREFACE. vii elements of the subject than can be obtained from the book alone. A good manikin is an invaluable help to the popular study of anatomy and physiol- ogy. Human dissection being out of the question, the manikin, which can be taken to pieces so as to show all the organs in their situations, connections, and relative dimensions, will afford the pupil a vivid and exact conception of the dependent parts of the living body, and make his physiological knowledge truthful and actual. A manikin for school pur- poses costs about S 2 5o, and may be imported from Paris,* where they are made, free of duty for educa- tional institutions. A great deal is also to be learned from such rough dissections of organic tissue and structures as may be made anywhere. Every butcher's shop is full of specimens of all parts of animals, that can be cheaply obtained for examination, and parents and teachers should encourage pupils to make such rude dissections as are practicable, and will help to give correct ideas of the relations and functions of the different organs. The study of the minuter parts of organized beings with the microscope, histology as it is called, has come into great prominence in modern times, and may be said to have revolutionized the science of life. No class in physiology should be without a microscope for the direct study of cell-structures and the finer tissues of both plants and animals. A suitable instrument, with a magnifying power of three hundred and fifty diameters, will show the circulation in the web of a frog's foot, and open a new world of fascinating and wonderful observation, *Auzoux is the principal manufacturer of these models. vni PREFACE. while it may be bought for sixteen dollars. Micro- scopic preparations of blood-corpuscles, muscular and nervous tissues, and sections of organs may be got for about twenty cents apiece, but it is desirable that the pupil should not rely upon these, but should learn the method of preparing and mounting objects himself. The microscope is not to be recommended as a mere toy to amuse idle curiosity ; there is work connected with it which is in a high degree educa- tional. It cultivates critical observation and careful manipulation, and is invaluable as a means of self- education. The little hand-book of Phin* will be found useful in guiding beginners with this instru- ment . The illustrations are largely copied from Gray's " Anatomy," though I am also indebted to Dalton's " Physiology," to Flint's " Physiology," to Ranney's "Applied Anatomy of the Nervous System," to Riidinger's " Topographisch-Chirurgische Anato- mie," and to Neumann's " Hand-Book of Skin Dis- eases." Many of the figures I have altered to suit my purpose, and the necessary descriptions are so inscribed upon or near them as to do away with the inconvenience of lettered references. A few of the cuts are original. For the use of material other than the illustra- tions, I have to acknowledge my indebtedness to Flint, Beaumont, Strieker, Neumann, Riidinger, Paget, Maudsley, Reynolds, Aitken, Huxley, Soel- berg Wells, Uhle and Wagner, Foster, and espe- cially to Dalton. R. S. T. March I, 1884. * "A Book for Beginners with the Microscope," 30 cents. GENERAL ANALYSIS. Part I.— Introduction. Gives certain necessary definitions, and describes the cell and its properties as being the real basis of all more fully developed living organisms. CHAPTER PAGE I. Definitions i II. Minute Structure of the Body 3 Part II.— Organs of Motion. A large body entirely composed of cells would be a soft, jelly-like mass, incapable of locomotion or of self-protection. But to obtain food it must be able to move from place to place, and also to move its different parts with reference to one an- other. For these purposes there must be points of resistance and points of support. These points are furnished by the bones, which act as levers, the joints being the fulcra. I. Bones in General 9 II. Particular Bones. — Joints 15 III. Injuries of Bones and Joints 25 But levers alone are of no use. The bones form a strong framework for the body, but they can not move themselves. To produce motion, organs are required, which can become longer or shorter, under varying circumstances. Such organs are the muscles. IV. Muscles 29 GENERAL ANALYSIS. Part III. — Organs of Repair. Energy is never lost or created. If the body loses energy in one way, it must gain it in another, or it will soon be worn out. Every muscular contraction wastes a certain amount of material, and an equal amount must be again supplied. This is done in the form of food. CHAPTER PAGE I. Food. — Supply and Waste ...... 42 But food, as it exists outside of the body, can not be appropriated by the wasting tissues. It must first be prepared. The process of preparation is called digestion. II. Mastication. — Swallowing 50 III. Stomach-Digestion 57 IV. Intestinal Digestion 79 After the food has been so far prepared, it must in some way be carried through the body to all its different parts, that each may take what it requires for its sustenance. This is accomplished by means of a fluid which passes continually and rapidly through all parts of the body, carrying the nutri- tious material. This fluid is the blood. V. The Blood 93 But the blood, besides carrying nutriment, must also remove the waste and used-up matters, which injure the health if they remain in the body. There is also a gas, called oxygen, which is found to be necessary to the processes of nutrition. This gas exists in the air, and is taken from the air into the blood. The process, by which the blood gets rid of impurities and takes in oxygen, is called respiration. VI. Respiration 99 VII. Asphyxia 120 The blood can not visit the different parts of the body of its own accord. It is a fluid, and must be propelled. There are organs for this purpose, which keep up what is called the circulation of the blood. VIII. The Heart 125 IX. The Blood-Vessels . . . . . . . . 136 X. Disorders of Circulation. — Hemorrhage . . 150 GENERAL ANALYSIS. XI Part IV.— Organs of Co-ordination. The motions of the body, the continual waste and supply, and the processes of digestion and circulation, form a very complicated series of phenomena. Certain parts of the body require more blood at certain times than at others. Processes taking place at the same time in different parts of the body might conflict and interfere with each other. We find, there- fore, a system of organs whose function it is to harmonize or co-ordinate all these processes, to produce a sympathy between them, and make them all work together for the com- mon interest. This is the nervous system. CHAPTER I. Nerve-Substance II. The Sympathetic System III. The Spinal Cord . IV. The Brain V. Special Nerves. — Hygiene Part V.— Organs of Protection. All the organs previously described form a very delicate structure, which is continually exposed to external injurious influences. It is exposed to heat and cold, to blows and scratches, and all manner of violence, and so we find it en- wrapped in a strong covering, which protects it from these influences, partly by its own strength and toughness, and partly by certain organs which are imbedded in it, and form a part of it. This organ is the skin, with the various glands and other structures found therein. PAGE I6 4 174 183 194 208 I. The Skin 217 II. Functions and Care of the Skin .... 223 Part VI.— Organs of Perception. The body being now complete, so far as its movements, nutrition, co-ordination of parts, and protection are concerned, we see that, as its food must come from outside, there must be organs to bring it into relation with the external world, to aid it in its search for food, and to protect it during the search. These organs are the organs of the senses, which bring us into relation with what is outside of us. and in this way are the sources of our ideas. The elementary one of these senses is touch, the others being only modifications of it. xii GENERAL ANALYSIS. CHATTER PAGE I. Touch, Taste, Smell 237 II. Hearing 246 III. Sight 254 Part VII. — Organ of Communication . . . .272 The body being now practically complete, we find still another organ, whose function it is to enable us to communi- cate our ideas to others. This organ is the larynx, the organ of speech, that wonderful faculty which has had so much to do with creating the tremendous gap that exists between man and the lower animals. Questions 277 Index 291 PART I. IN TR OD UC TION. CHAPTER I. DEFINITIONS. 1. Definitions. — The science which tells us about the different parts of the body, what they are, where they are, and how they look, is called anatomy. The science which tells us about the purpose of these parts, what they do and how they do it, is called pliysiology. The science which tells us what will interfere with the working of these parts, what will injure and what will help them, and how to avoid what is hurtful, is called hygiene. A part of the body, which is so small that when it has been separated from other parts it can not be further subdivided without the destruction of its organization, is called an anatomical element, as a cell or a fiber. Two or more anatomical elements, united or in- terwoven so as to form one substance, make what is called tissue ; e. g., fatty tissue, connective tissue, etc. A part of the body, which is made up of ana- tomical elements and tissues, together forming one 2 INTRODUCTION. whole, which can be separated from the rest of the body as an entire mass, and which performs a par- ticular function, is called an organ; as, the liver, the heart, a bone, or a muscle. A number of organs, similar in structure, but differing in size and shape, and spread throughout the body, are called a system ; as, the nervous sys- tem, the arterial system, etc. Several organs, Avhich differ in structure but are so connected as to work together for a particu- lar end, are called an apparatus ; thus, the stomach, liver, etc., constitute together the digestive appa- ratus. The work that is done by a healthy organ in the body is called its function ; e. g., the secretion of bile is a function of the liver. CHAPTER II. MINUTE STRUCTURE OF THE BODY. 2. Minute Structure of the Body. — The body, when its parts are examined with the microscope, is found to be made up mainly of cells, fibers, and fluids. The cell is considered to be the original element out of which every other element in the body is formed ; fibers, fluids, etc., being derived from or generated by previously existing cells. The different consistency of different organs is due to the varying proportions of these elements. If the fibers are in the largest proportion, the tissue or organ will be hard, tough, and elastic ; if the cells form the greatest part, it will be soft, inelas- tic, and yielding. 3. The Fiber. — The fiber proper (Fig. 1) is a slender thread, composed of a hard whitish or yel- lowish substance, some- times elastic and some- times not, but very tough and strong. Fibers are found in almost all parts of the body, binding the parts of organs together, and Fig. i. — Fibrous tissue. 4 INTRODUCTION. constituting almost the entire mass of some parts, as the tendons or sinews, for instance. The word " fiber " is also used of certain portions of muscular and nervous tissue, in a different sense from the one given above. These differences will be explained hereafter. 4. The Cell. — The cell is the most important structure in the living body, whether animal or vegetable. Life resides in the cell ; and every plant or animal may really be looked upon as a mass composed of billions of cells, each of which is alive, and each of which has its own part to play in the nourishment of itself and the rest of the body. A single cell * (Figs. 2 and 3) is a portion of al- Fig. 2. — Epithelium from the mouth. Fig. 3. — Liver-cells. buminous matter, which has by some been called protoplasm,f sometimes surrounded by a thin mem- * Scrape gently the surface of the tongue, and put the fluid thus obtained under the microscope. Plenty of cells will then be seen, similar in appearance to those shown in Fig. 2. f Pro loplasm, from two Greek words, signifying the first (or primi- tive) formed matter, because, so far as we know at present, it is the MINUTE STRUCTURE OF THE BODY. 5 brane and sometimes not, and usually having in its interior what looks like a smaller cell. This small body is called the nu'cleus of the larger one. In- side of the nucleus is often found another exceed- ingly minute body, or sometimes a mere shining point, called the nucle'olus (see Fig. 52). 5. Protoplasm. — The protoplasm, or matter which forms the mass of a cell, is of a semi-fluid consistency, somewhat like jelly, and can not be dis- tinguished by chemical tests from albumen. Hence it is said to be albuminous in its nature, resembling to some extent the white of a raw egg, which is almost pure albumen. All cells are so exceedingly small, being rarely more than 10 1 00 of an inch in diameter, that we really know very little of their minute structure, on account of the difficulty of in- vestigating them with such imperfect instruments as we have. 6. Granular Matter. — The points just mentioned are the most characteristic of the cell. Besides the cells, fibers, and fluids, there is a great deal of mat- ter in different parts of the body, which has been formed or deposited by the cells at different periods of their growth. This matter, under the micro- scope, sometimes appears granular, or as if made up of very minute specks, and sometimes almost transparent. Some of it is found to be fat in a finely-divided state, but some of it is albuminous, and some of it contains mineral matter in consider- able amount. 7. Difference between Living and Dead Cells. — A living and a dead cell look precisely alike, except- simplest form of living matter, and makes up the only part of all ani- mal and vegetable bodies which shows signs of life. INTRODUCTION. ing that the dead one is motionless. A living cell, minute as it is, frequently possesses the power of independent motion, or at least is able to change its form (Fig. 4). It also can take up nourishment into its mass, and can propagate itself. The move- ments of the cell can be beautifully seen in the white cells of the blood, which will be described hereafter. 8. Growth of Cells. — A cell propagates itself in several ways ; one of the most common is by divid- ing into two parts. This operation has been often watched under the micro- scope by skilled observers. The change is seen to begin in the nucleus, and, as that divides by a line through its center, the protoplasm of the cell ar- ranges itself in halves around each part of the nu- cleus, its surface dipping in toward the center, until finally the approaching surfaces meet and the Fig. 4. — White cells in motion. Fig. 5. — Cell dividing and forming two new cells. cell is divided into two new cells, each with its nu- cleus, and in every way complete (Fig. 5). This division goes on with great rapidity. The secre- tion from the throat and nose in nasal catarrh is composed mainly of cells, which are thrown off by millions during an inflammation. MINUTE STRUCTURE OF THE BODY. 7 9. Other Properties of Cells. — Cells also possess other powers which enable them to perform their important offices in the body. They are able to select certain substances out of a general mixture, and reject others. This is done by the liver-cells, for example, which secrete the bile, and by the cells of those glands which secrete the saliva. The cells of the brain act, in some unexplained way, as the instruments of thought. The cells in the kidneys separate matters from the blood which are very poisonous, and have to be expelled from the sys- tem. The power of division and of numerical increase of cells is not unlimited. If a portion of the body is wounded, it is healed again by the active efforts of the uninjured cells in the borders of the wound. The action of these cells ceases, however (if the part is healthy), to reproduce substance, when the part made vacant by the injury has been filled up. Why does this action of the cells, once started, not con- tinue until the body dies ? Why does the replace- ment of tissue cease as soon as the former surface is reached ? This question can not at present be answered.* Thus we see that the cell, minute as it is and simple as it is, performs its office in the body with * When the cells in the borders of a wound or sore are not in a healthy condition, they sometimes increase in number very rapidly, but the new cells, instead of being like the older ones, are larger, chiefly ow- ing to the greater amount of fluid in their interior. This makes them soft and spongy, and seems to interfere with their functions. They do not nourish themselves properly, and they increase and grow beyond the limit where they should stop, and where, if they were healthy, they would stop. This unhealthy growth is what is known as proud flesh, and it has to be repressed by proper surgical treatment. 8 INTRODUCTION. care and evidence of forethought and intention. It does what is necessary and no more. It does not act blindly. It does all it does with a purpose. Where and what is the intelligence that directs the active living cell to repair so far and no farther, to eat this and reject that, to multiply up to a certain point and then stop, and, most wonderful of all, to take upon itself the duties of other cells when they are sick and unable to act,* and stop performing these extra duties, when the other cells recover ? * When the kidneys, for instance, are diseased, so that the excretion of urine is interfered with, it is found that some of the poisonous mat- ters which usually pass out through them are ejected from the body through the lungs and skin. In such cases, physicians try to assist this process by inducing active perspiration, so as to relieve the kidneys from work as much as possible, and allow them to rest until they get well. PART II. ORGANS OF MOTION. CHAPTER I. BOXES. — GENERAL STRUCTURE. io. Uses of the Bones. — If the body were com- posed merely of cells, such as have been described, with fibers and fluids, it would be a shapeless, jelly- like mass, incapable of locomotion, and of self-pro- tection. There is a necessity, in such a large mass, of points of support and resistance, and the organs or tissues which furnish such points must be tough, hard, and elastic. Such organs are the bones, which form the framework of the body and determine its shape and size. Their most important offices are two in number, viz., to act as levers and points of support and action for the muscular parts, and to protect the soft and delicate organs from external injury. ii. Living and Dead Bone. — A bone, as we usually see it outside the body, is as different from a living bone as the skin of a corpse is from the liv- ing skin. We usually see it deprived of blood, while in the living body it is full of it, and is of a pinkish-white color externally, and deep red within. 12. Composition of Bone. — To accomplish the 10 ORGANS OF MOTION. two purposes above mentioned, bones must be hard and tough, in order to maintain their stiffness when the muscles pull upon them, and also to be able to resist external blows. They must also be in some degree elastic, or they would be too brittle for use, and would snap in two under great pressure. Ac- cordingly, we find all bones composed of two kinds of material, so thoroughly mingled and united that, when either kind is removed, the bone still retains its peculiar shape and size, although of course it does not weigh as much as before. About two thirds of the weight of every bone in the adult con- sists of earthy substances, mostly lime phosphate and lime carbonate, and the remaining third of ani- mal matter, part of which can be separated from the rest of the bone by long boiling, and is known as gelatine. If a bone be burned in a hot fire, all of the ani- mal matter will be destroyed, and the earthy mat- ters left. These will still retain the shape of the bone, but will be white in color, and will easily break and crumble in the fingers. If a bone, on the other hand, be soaked for a time in dilute hy- drochloric acid, all the earthy matter will be dis- solved out, and the animal portion left. This, as in the other case, will retain the shape of the bone, but will be flexible and tough, and may even be tied in a knot. By the combination of these two kinds of mat- ter, then, the bone is made hard, tough, and elastic, and admirably adapted to its uses in the body. 13. The Composition of Bone varies with Age. — In infants and children, the amount of animal mat- ter in the bones is proportionately greater than in BONES.— GENERAL STRUCTURE. u the adult, and so the bones of very young people will often bend when injured, instead of breaking. Surgeons call this the " green-stick " fracture, be- cause the bone is bent like a green twig, only a small portion of it on the outside of the bend being broken or torn apart. As a person grows older, the amount of earthy matter increases, until in old people the bones become very brittle, and break with very slight blows. 14. Varieties of Bone and their Structure. — Bones are divided, according to their shape, into long bones, short bones, flat bones, and a fourth kind, called irregular, which combine qualities belonging to the other classes. The long bones are found only in the limbs, and are the most important to the sur- geon, as it is in them that most fractures and other injuries occur. They are divided into a shaft and extremities. The shaft of every long bone consists of hard, compact, closely-grained tissue, somewhat like ivory. This is the only part used in the man- ufacture of ornaments, buttons, knife-handles, etc. The extremities of these bones form the joints, and, in order to give greater security and a greater purchase to the muscles as well as a greater surface for their attachment, the ends are much larger than the shaft. The tissue of which they are composed is also not so hard and close in texture, as, if it were so, the bone would be too heavy. There is no finer example of economy of material and the combina- tion of strength with lightness than the structure of the long bones (Fig. 6). The ends are made of fine threads of bone interlaced and crossing and supporting each other, so as to make a sort of spongy tissue, full of little cavities, and yet very strong and 12 ORGANS OF MOTION. tough. And even the shaft of the bone is not solid, but, as every one knows, is hollow in the middle. This hollow space and the little cavities of the ends of the bone are filled with what is called marrow, a substance composed chiefly of blood-vessels and fat, which has important duties to perform in the growth and nour- ishment of the bone. The other varieties of bone are composed entirely of the spongy (or cancel- lous) tissue, with a thin layer of hard, compact tissue on the sur- face. 15. The Periosteum and the Minute Structure of Bone. — All the bones are covered with a very tough, strong, fibrous mem- brane, called the periosteum, ex- cepting at the parts which enter into the formation of the joints, where they are covered with cartilage. This membrane ad- heres so closely to the bone as to require considerable force for its separation. It seems to form a part of the bone. Now, the periosteum and the marrow of the bones are necessary to their growth and nourishment. The blood-vessels and nerves spread and divide in these tissues before entering the actual substance of the bone. The bone itself is full of minute channels and Fig. 6.— The right femur, or thigh-bone, sawn in two lengthwise. Notice the arrangement of the bony fibers at the upper end, its peculiarity be- ing somewhat exagger- ated so as to make it more plain. BONES.— GENERAL STRUCTURE. 13 tubes varying in size from -^-J-g- to the So ^ 00 of an inch in diameter, through which the blood cir- culates, and the smallest of these tubes are con- nected at one end with exceedingly minute cavi- ties in the bone, in each of which lies a little cell, which does the work of nourishing, repairing, and enlarging the bone (Fig. 7). Thus we see that, even in so hard and firm a tis- sue as bone, what has been said about cells holds true. They are the real life of the bone ; they separate from the blood the neces- sary material and deposit it around themselves, some- what as a crab re- news his shell eve- ry year after get- ting rid of the old one. 16. Uses of the Periosteum. — It has long been known that, when the periosteum is severely bruised and separated from the bone by violence, the por- tion of bone deprived of the periosteum dies and has to be removed from the body. It is also found that a portion of bone, or even an entire bone, may be removed from the body, and if it be carefully done, so as to leave the periosteum in its place, the bone will grow again. A remarkable example of 2 Fig. 7. — Cross-section of bone, magnified. The small black spots are the cavities in which the bone-cells live. The fine lines are canals through which the plasma (sec- tion 122) of the blood passes. The large holes are for blood-vessels. 14 ORGANS OF MOTION. this was a case operated upon by the late Dr. James R. Wood, of New York. In a young woman, whose lower jawbone had become dead and caused her great suffering, this distinguished surgeon removed the whole jaw, leaving the periosteum and even the teeth, held in their places by an apparatus made for the purpose. The entire bone grew again, and the teeth became fixed in it as it grew. The person died several years afterward, and her skull, show- ing the result of this wonderful operation, is in the museum at Bellevue Hospital.* * Other experiments have even shown that, if a piece of fresh living periosteum be transplanted from a bone to a muscle, it will produce bone in its new situation. These remarkable qualities of the perios- teum have been explained by some, by supposing that, in each case of operation or experiment, some of the minute bone-cells have adhered to the periosteum when the mass of the bone was removed, and that they were the chief agents in forming the new bone. CHAPTER II. NUMBER OF BONES. — PARTICULAR BONES. — JOINTS. 17. The number of bones in the human body is two hundred (Fig - . 8). At one period of life they are all cartilaginous, but the cartilage gradually be- comes changed into bone. This process of change, ossification, as it is called, is not complete before the twenty-fifth year of life, and therefore no person can be called really grown up until that time. 18. The Vertebrae. — The foundation, so to speak, of the body — that portion of the skeleton to which the remainder is attached, and from which it is built up — is the spine, or backbone (Fig. 9). This is composed of many small bones, all of the same general pattern, called vcr'tebrce. The principal part of the vertebra (Fig. 10), called the body, is shaped very much like a wooden pill-box slightly hollowed out on the top and bottom. The bodies of the ver- tebrae form the front of the spinal column. From the rear of each of these bodies are offshoots of bone, which unite in such a way as to leave a hole about half an inch in diameter running up and down. These vertebrae are placed one above an- other, with elastic pads of cartilage between their bodies. These pads are so thick that, taken all to- gether, they make up about one fourth of the whole i6 ORGANS OF MOTION. Fig. 8.— The skeleton. THE SPINE. 17 length of the backbone. The vertebrae being ap- plied to each other in this way, it is evident that the holes just mentioned, which are surrounded by bone, will form a continuous canal (the spinal ca- nal) running from the skull down the back. This canal contains the spinal cord, which, next to the brain, is the most important part of the nervous system. At the sides of the spine, throughout its whole length, are holes, out of which pass nerves supplying the muscles and other organs of the body, and into which pass the blood-vessels that nourish the spinal cord. 19. The Spine. — The back- bone, being composed of so many pieces, is very movable. The power of motion varies, however, in different parts. It is greatest in the neck, and least in that por- tion of the back to which the ribs are attached. In the human be- ing, the neck is not so flexible as in many animals. Birds, in particular, can look directly back- ward. great fig. 9 .-The spine, sawn Notwithstanding the in two lengthwise, r . , showing the spinal power of motion in the spine, the canal and the holes different bones are very strongly between the verte- united and protected by power- biood-vesseis pass out. ful ligaments and muscles, which brae, where nerves and 1 8 ORGANS OF MOTION. render it difficult for a vertebra to slip out of place, and such an accident is one of the rarest which a surgeon is ever called upon to treat. Fig. io. — A vertebra. The elastic pads between the vertebrae deaden all shocks of the body and prevent them from injuring the brain. These pads become compressed during the day, especially when a person is much on his feet, so that at night-time the body is from one quarter to one half an inch shorter than it is in the morning. During sleep or rest the elasticity of the pads causes them to resume their original shape and thickness. 20. The Skull. — The skull is the only portion of the skeleton whose principal office is the protec- tion of soft parts within it. Accordingly, we find SUTURES OF THE SKULL. 19 that its bones are differently composed and dif- ferently put together from the other bones in the body. Those forming the outside of the skull, im- mediately surrounding the brain, and most exposed to blows, are composed of three layers. The out- side layer is the thickest, and is tough and some- what elastic. The innermost layer is very thin, but hard and brittle, so that it is called the vit'reous (glassy) table of the skull. Between these layers is spongy tissue, like what has been before described. This deadens every blow upon the head, and the safety of the brain is still further provided for by the arched shape of the skull, which tends to dif- fuse the force of a blow. The protection afforded by the shape and structure of the outside por- tion of the skull is very great, and it is a well- known fact in surgery that a blow upon the top of the head, without breaking the bone on which it falls, may break the bones at the base of the skull, immediately opposite the spot of the blow, by the mere force of the shock, although the latter bones are much thicker and more massive than the others. There is only one movable bone in the skull and that is the lower jaw. If the upper jaw be made to move in eating or speaking, it is only by moving the whole head where it joins the neck. 21. Sutures of the Skull. — The bones of the skull are joined together by what are called sutures — i. e., their edges are jagged and irregular, and fit together like dovetailed boards (Fig. 11). This renders the arch of the skull more compact, and, as far as resistance to pressure is concerned, the bones might be considered as one piece, while the 20 ORGANS OF MOTION. Fig. ii.- -General outlines of the skull, show- ing the sutures. interruptions at the sutures tend to deaden the shock of a blow. 22. The Frontal Sinuses. — In the front of the skull there are two cavities in the sub- stance of the bone itself. These are situated just above the eye-brows, and are called the fron- tal si'nuses (Fig. 1 2). The layer of bone which forms their front wall causes the prominences just over the eye- brows, and, as the cavities increase in size with age, this portion of the forehead becomes more prominent. The cavities are lined with mucous membrane, and are connected with the in- side of the nose by a canal or small passage, so that, when a person has a severe cold in the head, the inflam- mationsometimes runs up this passage into the frontal sinuses. When this is the case, the person has a dull, stuffy headache in that locality, due to the swelling of the mucous membrane. 23. The Ribs. — The bony part of the walls of Fig. 12. — Frontal sinus. NATURAL SHAPE OF THE CHEST. 2 \ the chest is made up of twenty-four ribs and the breast-bone, together with part of the spine behind. There are twelve ribs on each side, the first, nearest the neck, being usually the shortest. They increase in length from the first to the seventh, and then di- minish, so that the twelfth is also quite short. They are flat and narrow, and are attached at one end to the spine, in such a manner that they move easily up and down, while the other end is attached to the breastbone, or sternum, by means of a piece of car- tilage, varying in length with the length of the rib. The eleventh and twelfth ribs are not attached to anything at their forward end, and hence are called floating ribs. The ribs are attached to the spine in such a way that all of them move together up and down. In front, the stiff but elastic cartilage allows motion in every direction. Now the shape of the ribs is so peculiar, being a sort of double curve, that when they are raised at the sides, the ends which join the breastbone are pushed forward, and of course carry the breastbone with them. So it is evident that at every inspiration the diameter of the chest increases from front to rear as well as from side to side. 24. Natural Shape of the Chest. — In young peo- ple the cartilages are soft, but they grow harder as age advances, and become partially turned into bone. In youth they yield to pressure to such an extent that by tight lacing the shape of the chest is sometimes made exactly the reverse of what it ought to be (Fig. 1 3). The ribs naturally form a cone, with the smaller end uppermost, but it is not uncom- mon to see the smaller end at the waist. Na- ture will endure a great deal of meddling, but it 22 ORGANS OF MOTION. is not always safe to trifle with her, and all persons who carry tight lacing too far will inevitably suffer. 25. The Limbs. — More than one half of the bones in the body are found in the limbs. Out of two hundred bones, they contain one hundred and twen- ty-six, and these are so constructed and so arranged as to afford a great variety of movement. The up- THE JOINTS. 23 per and lower limbs are what is called homol'ogous in their parts — i. e., each bone in the arm has its counterpart in the leg, with only slight apparent exceptions. Thus, the shoulder - blade corresponds to the body of the hip-bone, the collar-bone to the front of the hip, the arms to the thigh, the two bones of the fore-arm to the two of the leg, the wrist to the ankle, and the hand and fingers to the foot and toes. The similarity and correspondence of these parts are quite clear in the skeleton. 26. The Joints. — To render move- ments possible, the skeleton is broken up in its whole extent by numerous joints. The surfaces of the joint are not covered by periosteum, but by a firm, bluish- white, smooth, and very elastic sub- stance called carti- lage. The two cartilage-covered surfaces in every 1 Fig. 14. — The right knee-joint, showing how strongly it is bound about by ligaments. 24 ORGANS OF MOTION. joint are in contact with each other. The joint is closed entirely by the syno' vial membrane, which passes over from one bone to the other, all round the outside. This membrane is exceedingly smooth and delicate, and its inner surface exudes a fluid very much like the white of an egg f which moistens the surface of the joint and renders every movement easy and frictionless. Outside of these structures are ligaments (Fig. 14), which hold the bones firmly in their places. Ligaments are composed of white, fibrous tissue (Fig. 1) — i. e., of tough, inelastic fibers or threads running parallel with each other, of a shining, silvery-white color. They are flexible, so as to allow of considerable lateral movement, but are tough and exceedingly strong, so that they hold the ends of the bones close together. Thus, the construction of the joints is such that they are strong, flexible, elastic, and supple. CHAPTER III. INJURIES OF BONES AND JOINTS. 27. Injuries in General. — The injuries to which the bones are most liable are fractures and disloca- tions. If the bone be fractured, the jagged ends of the broken bone irritate the parts about them, and the muscles contracting pull the broken ends out of their proper relation to each other (Fig. 15). In the dislocation, the end of the bone is out of its proper place. But the limb is movable at the point of fract- ure, while it is always stiff and fixed at the point of dislocation. In a fracture, also, the ends of the bone, if gently moved against each other, produce a peculiar grating feeling, which always tells the surgeon with certainty that the limb is broken. 28. Fractures. — Bones are rarely broken straight across, excepting in very young persons. The fract- ure is usually oblique, and so the broken ends slide past each other, and the limb is shorter than it was before the accident. In a broken thigh, the bone is surrounded by such a thick mass of muscles that, even if the broken ends are pulled by force into their proper places, it is impossible to keep them there. They will always slide past each other to a slight extent, and a person never recovers from such an accident, without having the injured limb from 26 ORGANS OF MOTION. half an inch to an inch shorter than the sound one. This has been shown and proved by thousands of careful measurements, DEL- TOID and should always be borne in mind when there is a temptation to blame a surgeon for fan- cied neglect. When a fracture oc- curs near a joint it is a much more serious ac- cident, for 'the inflam- mation which follows the injury involves the parts about the joint, and sometimes the joint itself, which maybe left stiff and almost useless Fig. 15.— Fractured humerus, showing f or a \ on g time after- how the muscles pull the ends of the -, rpi • .• " . , /, , ward. This is particu- broken bone out of place. r larly the case with frac- tures near the wrist, for the slow recovery of which the surgeon is so often blamed. 29. Dislocations. — When a bone is dislocated there is always a certain amount of injury to the parts about the joint. The ends of the bone are so carefully and strongly guarded and fastened by lig- aments and muscles, that these must necessarily be considerably torn and bruised, in order to let the bone out of its place. Thus it happens that a dis- location often gives rise to more pain and suffering immediately after the accident than a fracture * * Sometimes the violence resulting from a fall is not sufficient either to break or dislocate a bone, and yet the parts about a joint are so se- INJURIES OF BONES AND JOINTS. 2 J The vast majority of dislocations occur in the shoulder and hip joints, and are usually caused by a blow on the end of the bone when the limb is firmly extended, as when a person is falling and tries to save himself by stretching out his hand. The lower jaw is sometimes dislocated, and then the mouth remains wide open until the dislocation is reduced, rendering the sufferer a somewhat ludi- crous as well as pitiable sight. This accident has been known to occur during a prolonged yawn. 30. Healing of Injured Bones. — A fractured bone takes from three to six weeks, and sometimes longer, to become healed. A dislocated bone, after it is re- duced, requires to be kept quiet until all pain and swelling have subsided. In either case, there always remains more or less stiffness, which sometimes does not disappear for months after the accident. 31. Care of Injured Persons. — It frequently hap- pens that a bone is broken when the person is at a distance from his home, or from any place where he can be attended by a surgeon. In fractures of the lower limbs, he must be carried often for a long distance, and every one should know how to make him comfortable during transit. It must be remem- bered that the only object of any person who is not a surgeon, should be to keep the broken limb in such a position that there will be no motion of the fractured ends, so that the patient may suffer as little as possible, and the surgeon may find him as nearly as may be in the condition in which the in- verely strained that some of the ligaments are torn apart. Very often only a few fibers are ruptured, but such injuries always cause great suf- fering, and recovery is very slow. This form of injury is called a sprain, and is most likely to occur in the wrist, ankle, or knee. 28 ORGANS OF MOTION. jury left him.* Therefore, he should be carried on a litter, the broken limb being packed about with soft materials in such a way as to keep it from roll- ing or jarring. The weight of the foot will often make the lower part of the leg swing from side to side, and in the case of a fractured thigh, the leg should be protected on each side from the hip down. Dislocations require the same care, except- ing that a splint is not necessary. * It is a very good plan to bind the lower limbs together in such a case, above and below the injured part, so that the sound leg may serve as a splint to the broken one. A broken arm may be bound to an im- provised splint (a cane, a stick of wood, a shingle), a folded handker- chief or other padding being used to fill up the hollows between the splint and the skin, and the broken limb being supported by a sling around the neck. CHAPTER IV. MUSCLES. 32. The Muscles. — The bony framework of the body is set in motion by a system of organs called muscles, which cover the skeleton almost entirely (Fig. A), and cause the different bones to move upon each other by means of their peculiar prop- erty of contractility, or the power of becoming longer or shorter under varying circumstances. There are two kinds of muscles in the body, called voluntary and involuntary, which differ very much in their structure and functions. The volun- tary muscles, as the name implies, are under the con- trol of the will ; while the involuntary muscles are not only beyond our control, but act as a rule with- out our knowledge or consciousness. 33. The Voluntary Muscles. — A voluntary muscle is a mass of reddish fibers, somewhat loosely joined together by connective tissue, and easily separated lengthwise.* The flesh of animals is composed of muscular tissue. Every voluntary muscle is united * If the fibers of a piece of lean meat are carefully separated and closely scrutinized, it will be seen that they are connected with each other by a delicate tissue of fine white threads, interwoven like the fibers of a cobweb or of the most delicate lace-work. This is called connective tissue, and is found in almost all parts of the body, uniting the different elements that make up the various organs. 30 ORGANS OF MOTION. Fig. A. — The muscular system. THE MUSCLES. 31 at each end to some fixed point in the body, and there is always a joint or point of flexure between its points of attachment. When the muscle con- tracts, therefore, the two ends are brought nearer together, and motion is produced in the organ or limb to which it is attached. Every voluntary muscle can be divided into small fibers, lying side by side, and these again into fibrils still more minute. Each fibril under the microscope presents an appearance of delicate lines running at right angles to its length (Fig. 16). Fig. 16. — Voluntary muscular tissue. These lines are called stria, and the appearance is called striation. 34. The Involuntary Muscles. — Involuntary mus- cles are made up of flattish bands of long, narrow fibers, tapering at each end, somewhat of the shape of an oat, but more slender. Each fiber has a nu- cleus in its middle, and they are all connected 32 ORGANS OF MOTION. together lengthwise, as the voluntary muscular fibers are (Fig. 17). 35. Differences between the Voluntary and In- voluntary Muscles. — The voluntary muscles are all composed of the striated muscular fiber which allows of very rapid contraction, while the involuntary muscular fibers contract in a very peculiar manner. They do not be- gin to contract immediately, as soon as they are stimulated, but there is a short interval between the irritation and the response of the muscle. Then the contraction begins, and proceeds slowly and continuously up to a certain de- gree, when the fibers slowly relax, very much like the slow, crawling motion along the body of a worm or snake, when a wave seems to travel from one end to the other. Now there are some organs in the body, whose action must be rapid, from the nature of the office they perform, and still it would not do to have their motions depend upon the will. Such an organ is the heart. It must contract often and quickly in order to supply sufficient blood to the body, and yet, if its action depended upon our will, it would require all of our attention, to the exclu- sion of everything else. Accordingly, we find it composed of muscular fibers that are intermediate in structure between the voluntary and involuntary kinds. The involuntary muscular fiber is found, among other places, in the stomach and intestines, Fig. 17. — Involuntary- muscular tissue. THE MUSCLES. 33 in the iris of the eye, and in the walls of the ar- teries. 36. Difference in Size of Muscles. — The largest muscle of the back, the latissimus dorsi, weighs sev- eral pounds ; and one of the muscles of the leg, the sartorius, is two feet long ; while the stapedius, one of the little muscles inside the ear, is only the sixth of an inch long, and weighs about a grain.* Between these extremes are many variations in size and shape. 37. The Tendons. — Muscles are connected with the bones by means of tendons. A tendon is made up of fibrous tissue, and is a white, glistening cord, of exceeding strength and toughness. At the ends, they gradually change their appearance, becoming muscle at one extremity and bone or periosteum at the other. There is no sharp line, where the muscle or bone can be distinguished from the ten- don. Wherever the tendons would be likely to rise and form a line like the string of a bow during the contraction of a muscle, as at the wrist and the * Latissimus dorsi — i. e., the broadest of the back. This muscle is attached to the spine in the lumbar region and also to the lower ribs. The fibers come together so that the muscle has a triangular shape, and its small end is attached to the humerus. It is the chief muscle that comes in play when the body is raised from the ground by means of the arms. The sartdiius means the tailor's muscle. It is a long, ribbon-like muscle, which begins on the outside of the hip-bone and ends on the inside of the knee, crossing the thigh on the inner side. When it con- tracts, it raises the lower part of the leg, and turns it inward, thus crossing the legs, tailor-fashion — hence its name. It comes in play when one foot is placed on the opposite knee. Stapedius means the stirrup-muscle, so-called because it is attached to a small bone in the ear, which is shaped like a stirrup, and hence called stapes (Latin for stirrup). 34 ORGANS OF MOTION. ankle, for example, they are bound down by stout ligaments, through or under which they slide to and fro, the channels in which they move being lined with synovial membrane like the joints. 38. Force of Muscular Contraction. — When a muscle contracts (whether voluntary or involuntary), it becomes not only shorter and thicker, but harder, than before, and the force with which it contracts is enormous. To attain the compactness which we see in the body, the muscles of the limbs, for ex- ample, have to lie parallel with the length of the limb. Besides this, many of them are attached be- tween the fulcrum and the weight, and very near the fulcrum. The biceps, for instance, which (with the brachialis anticus) bends the forearm upon the arm, is attached at one extremity to the shoulder- blade, and at the other to the forearm, just below the elbow, where its tendon can be felt. Thus there are two disadvantages under which it acts. In the first place, its point of action is only about one eighth as far from the joint or fulcrum as the hand is, and in the second place, when it begins to contract, it acts at a very acute angle — in fact, almost parallel with the bone (Fig. 18). As the arm becomes flexed, Fig. 18. — Disadvantageous action of the biceps muscle, illustrated. the angle of action approaches more and more to a right angle, and the necessary effort becomes less THE MUSCLES. 35 and less. And yet we not only flex the arm easily enough at the elbow, but we do it with a consider- able weight in the hand. It has been estimated that the muscles of the arm, in flexing it at the elbow, with a ten-pound weight in the hand, contract with a force of at least two hundred pounds. And yet this is a feat which a delicate woman or a child can perform, and the force required is not to be com- pared with the power of an athlete. 39. Muscular Irritability. — Muscular tissue will contract under any kind of irritation. In the living body, the stimulus always comes from the nerves, but the muscle itself has a form of irritability, which lasts for a considerable time after death. When an ox is killed, and has been prepared for the market, the muscles may often be seen twitching and quiver- ing in the beef for half an hour, and the muscles of an amputated arm may also be seen to contract for some minutes merely under the irritation of the cold air. In cold-blooded animals, this irritability persists for a long time. If the heart of a frog be entirely removed from the body, it will continue to beat for several minutes, and, when it has finally ceased, it will start again on being pricked with a needle. This experiment may be repeated several times be- fore the muscular irritability finally vanishes.* 40. The Muscular Sense. — When a muscle con- tracts, the degree of contraction is perceived or felt * There are reasons for believing that the continued beating of the heart of a cold-blooded animal for hours after it has been removed from the body may be due to the presence of microscopic nervous ganglia in the substance of the muscle. This supposition, however, does not affect the usefulness of the frog's heart as an illustration of the fact that parts of animals continue to live after separation from the main body. 36 ORGANS OF MOTION. by the brain. For example, any one is conscious whether his thumb is bent inward toward the hand, or outward toward the wrist, entirely apart from the use of the sight. The precise manner in which this sensation is conveyed to the brain is still a sub- ject of conjecture. Although apparently so simple, it brings up questions of great intricacy and dif- ficulty, which can not be considered here. But this sense, whatever its manner of operation, is called the muscular sense. It is one of the chief means we have of determining the w T eight or the hardness and soft- ness of bodies, as we judge of these qualities mainly by the resistance our muscles meet with when hand- ling the bodies. But, more than all, the muscular sense is necessary in keeping the body upright. The size of the feet is so small, compared with the height of the body, that early in life it is a matter of ex- treme difficulty for us to keep our balance. To stand and walk is one of the first and one of the hardest things Ave have to learn. It requires a con- stant contraction of the muscles, now one set and now another, in order to keep from falling. 41. Use of the Muscular Sense in Standing. — Ordinarily we are assisted in standing upright by our sight. This fact, together with the muscular effort required to stand still, may both be made very evi- dent in the following manner: if a person stands with the feet close together, he will perhaps feel a slight swaying of the body, which has to be counter- acted by muscular contraction. Perhaps no such swaying will be perceptible to him. But now, still keeping the feet close together, let him shut the eyes, when the swaying of the body will become much greater than before, and the constant muscular THE MUSCLES. 37 contractions, now here, now there, will be so plainly- felt as to be disagreeable. In certain diseases, this muscular sense in the legs is lost, and then the per- son can stand with the eyes open, but if the eyes be closed he instantly totters and falls, for he then has nothing to guide him as to his vertical position. 42. Waste during Muscular Contraction. — The cause of muscular contraction is an unsolved prob- lem. There is nothing in the chemical composition or the physical structure of the muscle which would lead us to expect to see it contract when irritated, if we knew nothing more about it. All we can say is, that it depends upon the composition of the mus- cular substance, and we know, also, that every con- traction is accompanied by a loss of or change of material. In this way, our muscles are being con- tinually used up, and if they were not constantly sup- plied with fresh nourishment by the blood, they would soon wear out and die. But the minute mus- cular fibers (or the cells composing them) not only perform their special function of contraction, but are able to choose and take up out of the blood their own proper food and appropriate it. 43. Muscular Overwork. — If a muscle is hard pressed and exercised too much, so that the waste of material is greater than the supply, and it wears away faster than it is repaired, it falls into the con- dition which we call fatigue, and it is only with great effort that we can make it work. If it be still further imposed on, without opportunity to recu- perate, it soon gives out entirely, and can not be made to contract with vigor under any stimulus our brain can send to it. Such extreme fatigue is dan- gerous, because there is always the chance that the 3 38 ORGANS OF MOTION. muscular fibers may become so completely wasted that even their power of nourishing themselves may be impaired, and the recovery of their natural con- dition may be very slow and imperfect, or, in rare cases, impossible. 44. Muscular Inactivity. — On the other hand, if a muscle is not exercised at all, its power of nourish- ing itself is interfered with almost as much as if it is exercised too much. It is found that unused mus- cles gradually waste away, growing smaller and smaller, and becoming soft and flabby, and finally, if they are not used for a very long time, it can be seen by the microscope that the muscular fibers disappear altogether, or are filled with little particles of fat, which take the place of some of the muscular sub- stance, and so make it very weak and useless. Such inactivity of the muscles may occur in cases of paral- ysis, and the physician is then careful to stimulate them with electricity, in order to keep them, as nearly as possible, in a sound condition. The elec- trical current, in such cases, takes the place of the nervous stimulus, which naturally causes muscular contraction. The muscles of a broken limb, also, which have necessarily been idle while the bone was mending, are always very feeble for some time after the limb comes in use again.* * Curvature of the spine, which is more frequent among girls than among boys, is often directly attributable to lack of exercise. The muscles of the back become weak, and, as some exercise of the muscles of the right side can not be avoided, so long as the girl performs any duties whatever, the difference in strength between the muscles of the right side and those of the left side becomes greater than is natural. The result of this is that the stronger muscles overpower the others and pull the spine over toward the right side, greatly distorting the figure. In left-handed persons the curvature is toward the left side. EXERCISE. 39 45. Exercise. — It is necessary, therefore, that the muscles should be sufficiently exercised, and not too much. The kind of exercise is not of so much im- portance. No better form of exercise can be de- vised than the various out-door sports that boys are so fond of. It is much better that exercise should be a pleasure than a duty. For this reason, the or- dinary exercises of the gymnasium do not compare in value, as health-giving ones, with rowing, skating, running, riding, wrestling, swimming, and the va- rious out-door games.* It is really of no advantage, in our ordinary modern life, that the upper arm should, by judiciously and ingeniously planned ex- ercise, grow to be an inch larger than it was a year before, and to the ordinary youth the duties of a gymnasium are irksome to the last degree. f There is no evidence that athletes, whose bodies are knobbed with unsightly bunches of muscle, are any healthier or any happier, or live any longer, or do any more good in the world, than the less muscular * These remarks apply to girls as well as to boys. Out-door exer- cise of an agreeable kind is as necessary for the health of one as of the other. The hot-house plant is never strong, and the tom-boy grows to be the most healthy and vigorous woman, both mentally and physically. f It is not to be understood that the gymnasium is here altogether condemned. It is of great use in its proper sphere. But the boy's idea of a gymnasium is that it is a place to get strong, rather than healthy. The surroundings and examples are such as to encourage straining for effect, lifting heavy weights in emulation, and the like acts, which may injure a boy permanently. When gymnastic exercises are performed under a competent instructor, with proper ends in view, and an intelli- gent use of means to those ends, the matter is altogether different. But, as mentioned in the text, gymnastic exercises, excepting for the purpose of remedying particular defects, training special muscles for a particular purpose, or treating actual disease, can not be compared in efficiency with out-door sports. 40 ORGANS OF MOTION. person who confines himself to simple food, who in- sists upon pure air, and exercises moderately and for his own pleasure in the way that suits him best.* 46. Danger of Exhaustion. — But, while muscular exercise is necessary to continued good health, it should never be carried to the point of exhaustion. This is dangerous, not only, as previously indicated, because the nutrition of the muscle may thus be in- terfered with, but because, when the point of simple fatigue is passed, and exhaustion supervenes, the nervous system has become implicated and is getting worn out. This danger will be better understood when that part of our bodies is described hereafter. It is enough, for the present, to remember that a person is not harmed by being tired, but that it ahvays Jiarms one to be exhausted. 47. Rest. — When a muscle is fatigued, it recov- ers very fast if allowed to rest. For this reason it is much less fatiguing to walk an hour than to * The muscular strength which is developed by gymnastic training vanishes when the training ceases. It is often noticed by those who practice much in gymnasiums that constant practice is necessary to re- tain what increase of muscular power they have acquired. There seems to be a normal condition of the muscular system in each individual, to which he reverts when special training is abandoned. The strong men are not made so by training ; they are born with a tendency to a pre- ponderance of the muscular organs. Marvelous stories are told of men of this class. It is said of Frederick Augustus of Saxony, King of Poland (1670-1733), commonly called Augustus the Strong, that on one occasion, wishing to present a bouquet to a lady, and seeing nothing to wrap it in, he took a silver plate from the table and folded it around the stems with the greatest ease. In Dresden is exhibited a horseshoe, or the halves of it, which he is said to have broken with one hand. Similar stories are told of Baron Trenck (1711-1747) ; and of Milo, of Crotona, a famous athlete (520 B. c), it is said that he once carried a live ox on his shoulders around the stadium, then killed it with a blow of his fist, and afterward ate the whole of it in a single day. EXERCISE. 41 stand still an hour. In the former case the muscles constantly have short intervals of rest, while in the latter they are not able to rest at all, but are con- tinually in a state of contraction. If we are obliged to stand for a long time, therefore, we almost instinct- ively change our position frequently, stand on one leg and then on the other, or find some place to lean against, in order to give the muscles the rest they need. Out-door sports, then, are more healthful than gym- nastic exercises. Exercise may be pushed to tlic point of fatigue with- out injury, but never to the point of exhaustion. PART III. ORGANS OF REPAIR. CHAPTER I. FOOD. 48. Necessity of Food. — We all know that, as long as we are living beings, we tend constantly to lose weight. In our excretions, our breath, the per- spiration, the tears, the saliva, we lose altogether several pounds a day. All of this matter is so much gone, and if it be not replaced the body dies. It can not be too clearly impressed upon the mind that this waste or loss of material is continuous and inevitable. The processes of muscular contrac- tion, of secretion, even of thought, produce sub- stances which are taken up by the blood to be put out of the body. These substances are, many of them, very poisonous, and if they can not be ex- pelled from the body they kill it.* They are not the result of disease ; they are the constant product of living processes in a healthy body. So we see * Thus a substance called urea is excreted from the body through the kidneys. This substance is very poisonous, and, when the kidneys are diseased and are no longer able to discharge all of it from the body, it accumulates in the blood and finally causes death. So it is with the bile and with certain matters which pass away in the breath at every respiration. FOOD. 43 that there must be a continuous expulsion of such matters, and, of course, what each part of the body has lost by such a process must be replaced with fresh material. 49. Living without Food impossible. — If this fact be clearly understood, it will be easy to see that the numerous stories about persons who live without eating are false. If such persons live, their hearts must beat, their brains must think, their lungs must move in breathing, and all of these things cause in- evitably a waste of material. How absurd, then, to gravely talk of a person who has not taken any food or drink for six months, and still has not lost weight, but remains plump and healthy ! It is just as absurd as it would be to say that such or such a person had a limb amputated day after day, and yet after each operation weighed as much as before. These cases are all cheats, for if there is waste going on, which is not made good, the body must decrease in weight. If there is no waste, there is no life, no thought, no heart-beats, no respiration, no move- ment of any kind. These facts of the generation of force by food and of constant loss and gain are the chief foundation-stones of all correct knowledge of physiology, and can not be too firmly fixed in the mind. 50. Classification of Food. — In order to supply the waste in our bodies we need a great variety of food ; and, indeed, the procuring and preparing of food occupy a large portion of the lives of most peo- ple. The food we use is usually classified as nitroge- nous and non-nitrogcnoiis, or carbonaceous. But, besides these two great divisions, which include all our ani- mal and vegetable food, there are some substances 44 ORGAA T S OF REPAIR. which are neither animal nor vegetable, and yet are quite as necessary to our health as any other por- tion of what we eat. The most important of these are water and salt. 51. Water. — Water is present in a greater or less quantity in every part of the body, and, as it is rap- idly expelled, it has to be frequently supplied. It constitutes between three fourths and two thirds of the entire weight of the body, and the amount re- quired for an adult man daily is about three pints, in addition to that which forms a part of the solid food. The quantity used varies enormously, accord- ing to the waste. In a hot day in summer we need much more than in cold weather, and in damp days much less than on dry ones. 52. Salt. — Salt, also, is not only an agreeable con- diment, but has important offices to perform in the body. It has been shown by experiments on ani- mals that, if they are entirely deprived of salt, they decline very much in vigor, and every farmer knows how necessary it is to the health of his cattle and sheep.* 53. Other Inorganic Matters. — There are other * Boussingault, a French chemist (born in 1802), reported in 1854 some experiments he had made in regard to the importance of salt to cattle. He took six bullocks, of about the same age and vigor, and fed them alike, excepting that to three of them he gave 500 grains of salt every day and to the others none. At the end of six months the hides of those that had had no salt were rough and dull in color, while those of the others were shining and smooth. At the end of a year the salt- fed bullocks were in perfect health, while the others were dull and stupid, and the hair upon their hides was rough and tangled, with bare patches here and there. Wild animals, especially of the grazing kind, like deer and cattle, will travel long distances in search of salt, and seem to be as fond of it as children are of sugar. FOOD. 45 inorganic matters which are essential to the growth and nutrition of the body, but which are naturally found in articles of food and are not taken sepa- rately. Such are the salts of lime, soda, potash, and magnesia, all of which form a part of our common fruits and vegetables. The most important of these is probably the lime phosphate which forms so great a part of the bones. The husk of grain contains a certain proportion of this salt, and in growing chil- dren, in Avhom the cartilaginous portions of the bones are becoming ossified, wheaten grits or Gra- ham bread is a very welcome and advantageous ar- ticle of diet. It has been affirmed that the large size of the inhabitants of Kentucky is due to the fact that they live in a limestone region, and the water they use is strongly impregnated with lime. So large a proportion of lime taken into the body, at a time when the bones are forming and growing and hard- ening, is said to make them longer and stronger than they would be otherwise. 54. Non-nitrogenous Foods. — The non-nitroge- nous, or, as they are sometimes called, the carbonaceous foods, are sugar, starch, and fat. These substances are all composed of carbon, hydrogen, and oxygen, in varying proportions, the sugar and starch taken in our food being mostly of vegetable origin, while the fat may be either animal or vegetable. 55. Starch. — Starch forms a part of all grains and most vegetables, sago, tapioca, arrowroot, etc., be- ing almost pure starch, which has been extracted from the plants in which it is found. Rice contains about 85 per cent of starch, wheat about 70 per cent, and the potato about 15 per cent. This latter amount seems very small, but most of the remainder 46 ORGANS OF REPAIR. of the ioo parts of the potato consist of water, and starch really forms the bulk of the solid matter. It is a peculiarity of starch that it is very easily converted into sugar. This is actually accomplished in the human body, during the processes of masti- cation and digestion, as will be shown hereafter. 56. Sugar. — Sugar is taken in our food in various forms, for it has not always the same chemical com- position. It is always sweet, and is always easy to recognize as sugar, but varies in its proportions of carbon, hydrogen, and oxygen. Thus we find that cane-sugar, milk-sugar, and grape- or honey-sugar (often called glucose *), all differ from each other. Sugar is taken partly as an addition to the food for the sake of improving its flavor, and partly as a nat- ural constituent of vegetables and particularly of fruits, some of which contain an enormous propor- tion of it. Figs, for example, are more than half sugar, and hardly any fruit contains less than 10 per cent. 57. Fat. — Fat is found in almost all parts of the body, and particularly just underneath the skin, where it serves to give rounded outlines to the form, and also undoubtedly acts as an elastic cushion to protect the parts beneath from injury. During life, owing to the warmth of the body, the fat is fluid and transparent ; f but after death, as the body cools, it * Glucose is now produced artificially in enormous quantities by the use of sulphuric acid and corn. When anything containing starch is boiled with this acid, the starch is converted into glucose, which is the kind of sugar found in fruits. Cane-sugar can be changed into glucose in the same way, and as a matter of fact it is changed into glucose in the act of digestion, so that glucose must be looked upon as that form of sugar that it is natural for us to take in our food. f If the fingers be held close together in front of a bright light, the FOOD. 47 becomes solid. The fat which is found in the body is not all taken in with the food, but a certain amount of it is formed in the body itself, in a manner which is not yet understood. Certain articles of diet tend to increase the amount of fat in the body. This is notably the case with starch and sugar. In sugar- growing" countries, as the Southern States, it is a matter of common observation that the negroes grow fat and sleek during the sugar-season, and lose their superabundant flesh when the season is over. Arti- cles of food which contain much starch also increase the amount of fat The famous Banting system of treating corpulence is based on this fact, and con- sists mainly in depriving the patient of starchy vege- tables, grains, and sugar.* 58. Nitrogenous Foods. — The nitrogenous portion of our food is also both animal and vegetable, but chiefly animal. The principal substances of this class are fibrin, albu'mcn, and caJsc'in, They all contain a considerable amount of nitrogen, in addition to carbon, hydrogen, and oxygen, and are generally called by plrysiologists prd'teid substances, or the proteids. Casein is found in large proportion in milk, from which it is extracted to form cheese, and the two rosy tinge of their borders shows that they are to a certain extent trans- lucent. The ringers of a corpse, under similar conditions, are opaque. * Mr. Banting, the court undertaker, was put under treatment for corpulence by Mr. William Harvey, a London surgeon. He was al- lowed to eat any meat except pork, any kind of fish except salmon or eels, any vegetables except potatoes or rice, any kind of poultry or game, dry toast, fresh fruit, tea without milk or sugar, and to drink claret, sherry, or madeira wine, or gin, whisky, or brandy without sugar. When he began this diet in August, 1862, he weighed two hundred and two pounds, and a year after, he had lost forty-six pounds, and reduced his girth twelve and a quarter inches. 4 8 ORGANS OF REPAIR. others arc found mostly in the animal fluids, and in muscular fiber. There are also substances very much like the animal albumen and casein which are found in vege- tables, but they present slight chemical differences, although they probably answer nearly the same purpose in nutrition. Peas and beans contain a con- siderable quantity of the vegetable casein. 59. Necessity of Variety of Food. — It is neces- sary, for the preservation of health, that our food should contain a sufficient amount of these different kinds of matter. We must have water ; we must have salt and the lime compounds mentioned above ; we must have starchy substances (much the same to the body as sugar) and fats,* and we must have a certain amount of nitrogenous food. If one of these be lacking, the body soon feels it, and, although the person may not know precisely why he feels bad, he will often recover from his temporary disorder by a mere change of diet. The lack of any particu- lar ingredient in our food is often indicated to us by a longing for it. We feel a strong desire to eat par- ticular things and no others, and such a desire may generally be taken as a safe indication that the body needs them. 60. Paramount Necessity of Water. — Of all arti- cles used for food or drink, water, in some form or other, is the most indispensable. Men can live much longer on water without food than on food without water. The celebrated French physiolo- gist, Magendie, found that dogs lived eight or ten * This is said of a healthy person. Excessive production of fat, as in Mr. Banting's case, is to be regarded as a diseased condition, and so requires special diet. FOOD. 49 days longer, when supplied with water alone, than when they were deprived of both food and water. The pangs of thirst have been felt in a slight de- gree by almost every one, and it is the experience of those who have suffered from deprivation of food and water, in deserts and shipwrecks, that the tortures of thirst are much harder to bear than those of hunger. 61. Daily Amount of Food. — It has been found by Dr. Dalton, by experiments upon himself, that an adult requires food in about the following pro- portions : Meat 16 ounces. Bread 19 " Butter, or fat i\ " Water 52 " or about two pounds and a half of solid food and about three pints of liquid food daily. This is about the least amount which will keep him in good health. 62. Cooking. — Man does not take his food in the natural state, like other animals, but prepares it by cooking. This process is of advantage in two ways : it softens the hard parts of the food, such as beans, potatoes, and the various grains, and the fibrous tissue of meat ; and it also develops a pleas- ant flavor by the action of heat, which excites the flow of the fluids of the mouth and stomach, and thus aids digestion. CHAPTER II. MASTICATION. — SWALLOWING. 63. The Digestive Apparatus. — The food we eat is mostly insoluble, and in an unfit condition to be used for the nourishment of the body. Even so nutritious a substance as albumen can not be used without undergoing some change, and if pure fluid albumen be injected directly into the blood, it will be thrown out of the body by the kidneys un- altered. To prepare the various foods for use in the body, we are provided with a complicated series of organs, called the digestive apparatus, in which the food is ground fine and mingled with various juices until it is reduced to a fluid mass, which can be taken up by the blood and carried to all parts of the body in a condition fit for their nutrition. 64. Processes to which Food is subjected in the Body. — The process of preparing food for our nourishment may be conveniently divided into five stages. The first of these is mastication, which takes place in the mouth, and is a voluntary act. The second is siv allowing, or the act of passing food on from the mouth to the stomach, the beginning of this act being voluntary, and the greater part of it involuntary. The third is stomach digestion, which is involuntary ; the fourth, intestinal digestion, which MASTIC A TION.—S WALLO WING. 51 , sE tmes A/re ft* \ giooo vessels °Ss 4u Fig. 19. — Front view of the organs in their natural relations. The heart is partly covered by the lungs, but its true outline is indicated by a dotted line. Only ten ribs are shown on each side, the eleventh and twelfth (the floating ribs) being too short to be included in the section. 5 2 ORGANS OF REPAIR. is involuntary ; and the fifth is the process of ab- sorption, which is also a process of selection, by which certain portions of the prepared mass are taken up into the circulation for food, and the rest left in the intestines as waste material ; this whole process is also beyond the control of our will ; all waste matters are then expelled from the body. 65. Only One Voluntary Process. — All of these processes must be properly conducted, in order to maintain the body in a healthy condition. They are all important, and, if one be neglected or carried on in a disordered and unnatural manner, the others will all be affected, by reason of their close connec- tion with and dependence on each other. Only one of them is directly under the control of the will, and every one can do more toward preventing dyspep- sia and other disorders of the digestive organs, by paying some attention to the proper and complete mastication of his food than in almost any other way. If we examine the montJi, with reference to its uses in mastication, we find it prepared to per- form three great and important functions. 66. Use of the Taste and Smell. — In the first place, it is provided with an organ of taste, to assist us in selecting our food. In this it is aided by the proximity of the nose, so that we have the addi- tional advantage of the sense of smell. And the nose is not only so situated as to aid us in judging of food before it enters the mouth, but it is con- nected with the throat behind, so that odors are detected from substances already in the mouth. 67. The Teeth. — In the second place, the mouth is provided with organs for grinding and crushing the hard parts of the food, and reducing them to a MASTIC A TION.—S WALLO WING. 53 Fig. 20. — Section of a tooth. The black portion is the cav- ity occupied by the nerve and blood- vessels. soft mass, fit to be acted upon by the fluids in the stomach and intestines. The organs directly of use in this operation are the teeth (Fig. 20), but essential aid is afforded by the mus- cles of the checks and the tongue. The rows of teeth are narrow, and, except for the action of these mus- cles, the food could not be kept be- tween them. Indeed, it has been found that in cases of paralysis, when the muscles of the cheek are unable to contract, while the tongue still retains its power, the food gets pushed out between the cheek and the teeth, and accumulates there. The lower jaw is moved by some of the most powerfully acting mus- cles in the body. The chief one of all is the mas'- scter, which is attached above to the ridge of bone running backward from the lower border of the eye toward the ear, and below to the horizontal portion of the jaw. The muscle is nearly square in shape, and, as is easily seen, acts at a great mechan- ical advantage. As a matter of interest connected with this muscle, it may be stated that it is the mus- cle generally referred to for proof that muscular contraction is accompanied by a sound. If the lower jaw be firmly closed, and the teeth powerfully pressed together so that the muscles of mastication are strongly contracted, a low, rumbling sound will be heard, which can not be explained in any other way than as caused by the muscular contraction. 68. The Saliva. — In the third place, the food, while undergoing mastication, is mixed with cer- 54 ORGANS OF REPAIR. tain fluids, called collectively the saliva. They are the product of three sets of glands, each of which is double — i. e., there are three glands on each side of the mouth (Fig. 21), and the secretion of each Fig. 21. — The salivary glands of the right side. pair is peculiar to itself. The largest of these are the par vt 'id glands, which are situated just in front of the lower border of the ears, and are the glands which become swollen and cause the distortion of the face in the disease known as the mumps. The fluid secreted by these glands is very thin and watery, and constitutes the greater part of the sa- MASTIC A TION.—S WALLO WING. 55 liva. The other glands are situated just inside the lower border of the jaw and beneath the tongue. Their secretion is much thicker and more glutinous than that of the parotid glands. Besides these fluids, there is a small amount secreted by the mucous membrane lining the mouth, and all these mingled fluids constitute the saliva. The saliva is secreted to some extent at all times, and keeps the lining membrane of the mouth moist and soft, but it is a familiar fact that its amount is greatly increased at certain times. Thus, we say, at the sight, or even sometimes at the sug- gestion, of an appetizing meal, the " mouth waters." * The fact of its excessive secretion at such times shows that it has a part to perform in the process of mastication and digestion. 69. Properties and Use of the Saliva. — Experi- ments have shown that saliva possesses the property of converting starch into sugar ; but, as this is also done by the digestive fluids, it is not considered to be a very important function, and the chief use of the saliva undoubtedly is, to make the processes of mastication and swallowing of food easier. If food were taken dry, and there were no means at hand of moistening it, mastication would be very difficult and tiresome, and swallowing almost impossible. Bernard f found, by experiments upon a horse, that * In physiological lectures before medical students, it is not uncom- mon to illustrate this fact in a curious way. A slender tube is intro- duced into the opening by which the parotid saliva is discharged into the mouth, and, according to the condition of the person operated on, there will either be no flow of saliva or it will come out drop by drop. But now let food be brought in, and the moment it is seen the saliva begins to run from the tube in a plentiful stream. f Claude Bernard, a famous French physiologist (1813-1S7S). He 5 6 ORGANS OF REPAIR. when an operation had been performed, which pre- vented the parotid saliva from entering the mouth, the animal could masticate and swallow (the latter process being accomplished with great difficulty) only three quarters as much oats in twenty-five minutes as he had previously eaten in nine. It is probable that the parotid saliva, which is almost like water, assists mainly in the mastication of the food ; while the other secretions, which are thicker and more slippery, coat the outside of the mass, and render it easier to swallow. The total amount of saliva secreted by a healthy adult in twenty-four hours has been calculated, after numerous experiments, to be nearly three pounds. Note. — It is important for the health of the individual that the teeth should be kept in good condition, in order that mastication may be thorough and complete. Particles of food which stick between the teeth, if they are allowed to remain, putrefy and impart an offensive odor to the breath. The acids which are developed during the putre- factiqn of such matters are also injurious to the teeth and tend to hasten their decay. There are also certain substances deposited from the saliva around the necks of the teeth, called "tartar." If this is not removed, the gums are bruised against it, and finally recede from the teeth, leaving a part of the fang bare, and thus exposing to all sorts of injurious influences a part of the tooth which was never intended to be so exposed. The teeth should therefore be frequently cleaned, at least twice a day, with water and a soft brush (a stiff brush injures the gums), tooth- picks being used when necessary. Avoid fancy tooth-powders and washes, for they often contain injurious acids or gritty substances. To polish the teeth, use powdered orris-root and chalk, which can be bought of any druggist. Never crack nuts with the teeth, and, on the slightest appearance of decay, consult a good dentist. was Professor of Physiology in the College of France from 1855 until his death. Especially distinguished for his discovery of the formation of sugar in the liver, and for his researches on the functions of the sym- pathetic nervous system. (See later.) CHAPTER III. STOMACH-DIGESTION. 70. The Alimentary Canal. — The food, which is now ready to be operated upon by the digestive fluids, passes beyond the control of the person who swallows, and begins its travels in the long tube, called the aliment' ary canal (Fig. 22). This canal begins at the mouth and ends with the large intes- tine, and is nearly thirty feet in length. It does not properly assume the form of a tube until the beginning of the cesopli'agns, or gullet, and at one point, namely, at the lower extremity of the oesoph- agus, there is a considerable enlargement, which has the appearance of a bag or pouch, and is called the stomach. To understand the working of the alimentary canal, it is necessary to know something of its anatomy. The two most important tissues in its structure are the mucous membrane which lines it through- out, and the muscles which surround it, and are im- bedded in its walls. 71. Mucous Membrane. — Mucous membrane (Fig. 23) is the skin which lines the interior canals of the body. While the outside of the body is covered by a smooth, white, tough skin, we see that, at the openings leading to its interior, such as the mouth, 58 ORGANS OF REPAIR. nose, etc., the character of this covering" suddenly changes, and it becomes a reddish or pinkish mem- OESOPHAGUS- Fig. 22. — The alimentary canal. brane very soft and delicate in texture, and con- tinually moistened by its secretions. This is called mucous membrane, and in one form or another it lines all those internal parts of the body, which communicate with the external air. It is made up mainly of fibrous tissue, consisting of fine threads, interlacing with each other in every direction and densely woven. Its surface is cov- STOMACH-DIGESTION. 59 Fig. 23. — Structure of mucous membrane illustrated. At one side is a detached portion of a tube, or follicle, enlarged so as to show the epithelium more clearly. ered with minute cells, called epithe'lial cells* At various points on the membrane are minute tubes or cavities, less than y^-q of an inch in diam- eter,of different shapes in different places, and in some situations so numerous that they lie almost in contact with each other. These mi- nute tubes are closed at the bottom, but open on the surface of the membrane. Small as they are, they are lined from top to bottom with epithelial cells, which really carry on the work of secretion. All around, among, and underneath these tubes are small blood-vessels, which nourish the membrane, and from which the little epithelial cells separate the materials which form the mucus. 72. Muscles of the Alimentary Canal. — The mus- cles which form a considerable part of the walls of the alimentary canal are of the involuntary or non- striated kind. The fibers run in various directions, some of them surrounding the oesophagus and the * All free surfaces of the body, whether inside or outside, are cov- ered with cells. In the interior of the body, the alimentary canal, the lungs etc., these cells are soft, and, so to speak, plump, and are called epithelial cells, or a mass of them taken together is called epithelium. On the external surface of the body they are dry, flat, hard, and horny, and are called epider mal cells, or, in a mass, the epidermis. In both situations they are being constantly shed and renewed. The fresh ones are continually forming underneath, and, as they grow, take the place of the old ones on the surface, which are being constantly rubbed off in one way or another. All the secretions of mucous membranes contain these epithelial cells, and the slightest scraping of the skin dis- lodges epidermal cells. 60 ORGANS OF REPAIR. intestines in a circle, so that when they contract they make the canal smaller ; while others run lengthwise, and their contraction shortens the ca- nal. When these two kinds of fibers, the circular and the longitudinal, contract together, they propel forward anything that comes within their grasp. 73. Serous Membrane. — Besides these parts of their structure, the stomach and intestines are cov- ered on the outside by what is called a serous mem- brane, which is found lining all cavities inside the body that do not communicate with the air, ex- cepting the joints. This kind of membrane is trans- parent, exceedingly fine and soft, and smooth like satin, and is constantly moistened with a slight amount of fluid. The use of serous membrane is to allow organs to move freely upon each other without friction. If it were not for some provision of this sort, the movements of the stomach and in- testines during digestion would be painful, or at least disagreeable, while, as things now are, we are entirely unconscious of any movement at all. 74. Swallowing. — After mastication is completed the tongue passes the mass of food backward into the phar'ynx (or throat), whence it goes on into the oesophagus. The oesophagus (Fig. 24) is about nine inches long, and extends from the throat to the stomach, not just behind the breastbone, as many suppose, but just in front of the spine. The mus- cles of the upper portion are of the striated variety, but, nevertheless, their contraction is not voluntary. When anything has once passed to the back of the throat, it will be swallowed and sent into the stom- ach, in spite of our will. 75. The Stomach. — The stomach varies in size STOMACH-DIGESTION. 61 in different persons, but on the average will con- tain about three pints of fluid in the adult. Its Fig. 24. — Vertical section of the head and neck. At the base of the tongue is seen the epiglottis, and below this the larynx. Between the larynx and the bodies of the vertebrae lies the cesophagus. shape has often been compared to that of the air- bag of a bag-pipe, which it much resembles (Fig. 25). It has two openings, one at the lower extrem- ity of the cesophagus, where food enters, and the other at the point where food passes out and the small intestine begins. These openings are both in 4 62 ORGANS OF REPAIR. the upper border of the organ, and only a short dis- tance apart, the pylo'rus, or exit, being at the right Fig. 25. — Outside of the stomach, front view, showing the muscular coat. extremity, and the car'diac opening near the mid- dle."* The stomach extends toward the left for about three inches beyond the cardiac orifice, and is larger in this part than in any other. This por- tion is called the great pouch of the organ (Fig. 26). Each orifice is guarded by a powerful muscle, surrounding it in a circular form, which can con- tract so tightly as to prevent the passage even of a fluid. As a rule, these muscles prevent the passage of any substance backward through them, in oppo- sition to the natural course of the food. * Pylorus, a. Greek word meaning the gate-keeper ; cardiac, from a Greek word meaning the heart, because it is very near that organ. STOMACH-DIGESTION. 63 76. Stomach-Digestion. — It was formerly sup- posed that the whole process of digestion was Fig. 26. — Inside of the stomach, front view, showing the folds (or rugae) of the mucous membrane. performed in the stomach, but this is now known not to be the case. The nitrogenous portions of the food are the only ones that are digested in the stomach. The oily and fatty, as well as the starchy, portions are digested in the small intestines. Fluids are very rapidly absorbed by the stomach. 77. Dr. Beaumont and St. Martin. — There are so many difficulties connected with the investigation of 64 ORGANS OF REPAIR. the subject of digestion, that very little was really known about it until the year 1833, when a small book was published by Dr. Beaumont, of the United States Army, giving physiologists their first precise knowledge of what takes place in the human stom- ach. His observations were so well taken, that very little has been added since to what he dis- covered upon the particular subject of stomach digestion. In the year 1822, Alexis St. Martin, a stout young French Canadian, in the employ of a fur-trading company, and about eighteen years of age, received a severe wound in the left side from the accidental discharge of a shot-gun at a distance of about three feet. He was attended by Dr. Beaumont, and, although his recovery was slow, his health was finally completely re-established, and he was still living in Vermont, the father of a numerous family, at a very recent date. In the situation of the wound, however, was left an opening into the stomach, about four fifths of an inch in diameter, closed by a flap or valve of mucous membrane on the inside. This valve could be pushed inward, but not outward ; and thus, although the operation of digestion was not at all interfered with, the interior of the stomach could be thoroughly examined, and experiments performed with the greatest facility and accuracy. Dr. Beaumont kept the young man in his employ for several years, and made hundreds of observations upon him. These were published in his little book, and made both him and St. Martin immediately famous. As Dr. Beaumont was the first, and for many years the only, person who ever saw the interior of S TO MA CH-DIGES TION. 65 the stomach in a living man, much of the following description will be taken from his volume. 78. Interior of the Stomach. — " The interior coat of the stomach," he says, " in its natural and healthy state, is of a light or pale-pink color, varying in its hues according to its full or empty state. It is of a soft or velvet-like appearance, and is constantly covered with a very thin, transparent, viscid mucus, lining the whole interior of the organ." 79. The Gastric Juice. — The changes which the food undergoes in the stomach are due to the action of the gastric juice, the appearance of which, with the manner of its secretion, is thus described : " By applying aliments or other irritants to the internal coat of the stomach, and observing the effect through a magnifying-glass, innumerable mi- nute lucid points can be seen arising from the mucous membrane, and protruding through the mucous coat ; from which distils a pure, limpid, colorless, slightly viscid fluid. This fluid is inva- riably distinctly acid." " The fluid so discharged is absorbed by the aliment in contact, or collects in small drops and trickles down the sides of the stomach to the more depending parts, and there mingles with the food or whatever else may be contained in the gastric cavity." " The gastric juice never appears to be accumu- lated in the cavity of the stomach while fasting. When aliment is received, the juice is given out in exact proportion to its requirements for solution, except when more food has been taken than is necessary for the wants of the system." 80. Composition and Amount of Gastric Juice. — 66 ORGANS OF REPAIR. The gastric juice contains two important constitu- ents, viz., hydrochloric acid and pepsin. If it be deprived of these, it will no longer exhibit its pe- culiar properties ; while, if it retains them, as Dr. Beaumont first showed, it will digest food in a glass tube, outside the body, provided the tube and its contents be kept at a temperature of ioo° Fahr., which is about the ordinary temperature inside the stomach. The average amount of gastric juice secreted daily by an adult human being has been estimated at a little less than fourteen pounds, or about a gallon and a half. 81. Movements of the Stomach. — But, besides the action of the gastric juice in stomach-digestion, a very important office is performed by the muscles which form a large part of the walls of the organ. During digestion, these muscles are continually contracting in a slow, regular order, producing movements of the contents of the stomach in a very peculiar manner, which, in health, never varies. Dr. Beaumont says that the ordinary course and direction of the revolutions of the food are first, after passing out of the oesophagus into the stom- ach, from right to left, thence down along the great curvature, from left to right, to the pylorus, whence it returns again along the upper border of the or- gan to the left extremity of it. Each of these jour- neys of the food around the organ occupies from one to three minutes, and they serve to mingle the gastric juice more thoroughly with the food. As soon as the process of digestion is gone so far as to bring portions of the food into a condition for ab- sorption, it is found that every time the contents of S TO MA CH-DIGES TION. 6 7 the stomach pass the pylorus the mass becomes di- minished in amount, showing that a portion has been squeezed or pressed through the opening into the intestine. " These peculiar motions and contractions con- tinue until the stomach is perfectly empty, and not a particle of food remains. Then all becomes quiet again." Thus that part of the digestion of food which is carried on in the stomach is accomplished by the action of the gastric juice, and the changes pro- duced by it are assisted, and the prepared food is passed out of the stomach, by the constant contrac- tions and churning motions of the organ just de- scribed. This, then, is the ordinary healthy process of stomach-digestion, when not in any way hindered or interfered with. Let us see what changes take place in the appearance of the stomach and in its functions when it is injuriously affected. 82. Appearance of the Stomach during Indiges- tion. — " In a feverish condition, from whatever cause — obstructed perspiration, undue excitement by stimulating liquors, overloading the stomach with food — fear, anger, or whatever depresses or disturbs the nervous system," the lining of the stom- ach " becomes somewhat red and dry, at other times pale and moist, and loses its smooth and healthy appearance ; the secretions become vitiated, greatly diminished, or entirely suppressed." 11 There are sometimes found, on the internal coat of the stomach, eruptions or deep-red pimples. These are at first sharp-pointed and red, but fre- quently become filled with white purulent matter; 68 ORGANS OF REPAIR. at other times, red patches, from half an inch to an inch and a half in circumference, are found on the internal coat. These appear to be the result of con- gestion in the minute blood-vessels of the stomach." " These diseased appearances, when very slight, do not always affect essentially the gastric appa- ratus. When considerable, and particularly when there are corresponding symptoms of disease, as dryness of the mouth, thirst, furred tongue, etc., no gastric juice can be extracted. Drinks received are immediately absorbed or otherwise disposed of ; none remaining in the stomach ten minutes after being swallowed. Food, taken in this condition of the stomach, remains undigested for twenty-four or forty- eight hours or more." " Whenever this morbid condition of the stom- ach occurs, with the usual accompanying symptoms of disease, there is generally a corresponding ap- pearance of the tongue. When a healthy state of the stomach is restored, the tongue invariably be- comes clean." These are the observations of one who saw what he describes, and took careful notes of what he saw. 83. Time required for Stomach-Digestion. — The time required for digestion in the stomach varies very much according to the character of the food. Dr. Beaumont found that the time of stomach-di- gestion in St. Martin varied from one hour to about five and a half. Among meats, the soonest digested was boiled pig's feet, which took an hour, and the longest time was taken for roast pork, viz., five hours and a quarter ; among vegetables, rice is di- gested in an hour, while boiled cabbage requires STOMACH-DIGESTION. 69 four. The average time required for an ordinary- meal is probably about three hours. 84. Advantage of Thorough Mastication. — Dr. Beaumont found that, when a piece of meat or other food is attacked by the gastric juice, it is slowlv dissolved from the outside. The juice is not soaked up and does not penetrate the interior of the mass, but gradually softens the exterior of it ; and, as the outside portion becomes friable and dissolves, the piece grows smaller and smaller, the gastric juice in this way advancing little by little, until the whole mass is liquefied. From this it is evident that it will take longer to digest a large piece of meat than to digest the same amount after it has been divided into small pieces ; for this reason it is important to masticate the food thoroughly before sending it into the stomach. 85. Eating too little. — It is evident that it will not do to take too little food. Enough must be eaten to supply the needs of the system, and it must be of such a quality that it can be readily di- gested and appropriated. 86. Eating too much. — But, on the other hand, we must not teike too mucli food. There seems to be some subtile relation between the amount of food required by the system and the amount of gastric juice furnished by the stomach. What is likely to be the result, then, if more food is taken into the stomach than can be acted on by the gastric juice? Let us consider. The temperature of the interior of the stomach is about ioo° Fahr. This is just about the temperature at which fermentation and putrefaction (which is a sort of fermentation) are most active. Heat and moisture favor these pro- 7o ORGANS OF REPAIR. cesses. Both of these conditions exist in the stom- ach, but, under ordinary circumstances, the gastric juice prevents any other changes than those due to its own action. But, if more food is introduced than the gastric juice can dissolve, fermentation occurs, and offensive gases and irritating acids are produced. Then the symptoms of indigestion come on, there is constant belching of wind from the mouth, an uneasy sensation in the stomach, and, as soon as the undigested and fermenting mass passes out into the intestine, rumblings and colic set in, followed probably by a diarrhoea, which continues until the offending matters have been ejected from the body. 87. Eating between Meals. — Similar symptoms may be produced by eating between meals. When a sufficient meal has already been eaten, we should wait until it has been digested and the stomach has had a short period of rest before we give it any more work to do. This organ can not work inces- santly any more than other parts of the body, and when it is ready for more food the sensation of hunger apprises us of the fact. If we load it with fresh food before the previous supply has been dis- posed of, there may not be enough gastric juice secreted to digest it. Then it ferments, or putre- fies, and causes a fit of indigestion, as just described. 88. Hunger. — It is sometimes said that a person should rise from the table, after every meal, still hungry. This is not correct, and the reason is plain. Hunger is the natural indication that the body is beginning to be worn out, and needs fresh material to repair its losses. And although the appropriation of the food is finally made by the STOMACH-DIGESTION. yi cells that compose the body, and so must be after it has been already digested and carried to them, nevertheless the sympathy of the different parts of the body with each other is such that hunger is satisfied by the mere act of supplying food to the stomach. Not only that, but the digestibility of the food has a great deal to do with it. Certain kinds of food, which we call rich, generally contain- ing a great deal of fat and sugar, satisfy the hunger and produce a sense of satiety, when we have not really eaten enough to supply the bodily needs. This is because such food is digested very slowly, being so permeated with fat that the gastric juice, which does not digest fat, penetrates to the albumi- nous portions of the food with great difficulty. In such cases also fermentation frequently occurs, and persons who eat much so-called rich food may satis- fy their hunger with it day after day, and still suffer from indigestion, and not get enough nourishment to repair the waste of the body. For these reasons, plain food is the best, especially for the young. 89. How much to eat. — The true way, there- fore, is not to rise hungry from the table, but to stop eating when the hunger has been satisfied, and before any feeling of repletion comes on. It should be borne in mind that the process of digestion ought to go on without our consciousness. After a proper meal, the only sensation caused by the food Ave have taken should be that of complete satisfaction and contentment. If the stomach feels stuffed and full, we have eaten too much. It may be properly disposed of if the eater is in vigorous health, and able to rest for a time until the uneasy feeling of repletion wears away. But the whole 72 ORGANS OF REPAIR. process ought to go on without causing us a mo- ment's thought. If we are healthy, and if we treat our digestive organs properly, we ought never to feel that we have a stomach, or liver, or bowels. They will never trouble us, if we do not trouble them. Our meals, therefore, should be sufficiently far apart to allow an hour or two at least to intervene between the digestion of one meal and the begin- ning of another. As digestion in the human being ordinarily occupies from three to four hours, our meals should be at least five hours apart, and this is about the time usually allowed. 90. What to eat. — The matter of what to eat, amid the great variety of foods, may safely be left, in a healthy person, to the appetite. It is a familiar proverb that " one man's meat is another man's poison." Each individual must learn for himself what food is the best for him. If any article is found to disagree, it should thereafter be let alone ; no attempt should be made to overcome a natural repugnance, and acquire an appetite for what is distasteful. This is to fly in the face of Nature ; it is much the same as saying that one is competent to direct the secret processes of nutrition and to regulate the functions of organs, about which he knows almost nothing, and which he can not con- trol. Such action is intermeddling, not judicious care. 91. Condiments. — Something should here be said, however, about the use of certain substances which are not foods, and yet are in common use throughout the world, to make food more accepta- ble to the palate. Such substances are pepper and S TO MA CH-DIGES TION. 7 3 mustard. These condiments have two qualities that have caused them to be used in the prepara- tion of food, viz., a peculiar flavor, which makes articles of food to which they have been added more savory, and a quality called pungency — i. e., they irritate any part of the body with which they are brought in contact. When either is placed upon the tongue, smarting is produced, sometimes to a painful degree, and tears start in the eyes. The effect can therefore be imagined when these substances are rubbed over the delicate mucous lining of the stomach during the movements of digestion. They can not but be extremely irritat- ing, and therefore injurious. As a matter of fact, the excessive use of such things, whether alone or in highly-seasoned sauces (Worcestershire, etc.), results in extreme debility of the digestive appara- tus and confirmed dyspepsia. The golden rule in the treatment of the stomach is, to put nothing into it that can be felt after entrance. As before stated, the operations of the stomach ought to go on with- out our consciousness of them. If enough spice is taken to produce a feeling of warmth in that organ, it is too much, and the mucous membrane has been irritated. We are all, or nearly all, born into the world with sound digestive organs, which need no spurring to make them do their, duty. If the)' get out of order, it is our own fault, and rest will do more than anything else to set them right. If you whip a good horse, when he is doing his best, you will spoil him. 92. The Natural Drink. — The natural drink of all animals is water, for milk is to be looked upon as a food. Many people, however, are not satisfied 74 ORGANS OF REPAIR. with water alone, but prefer it flavored with some- thing else, and a great variety of drinks have been invented, of which we shall only consider tea, cof- fee, and those which contain alcohol, as malt and spirituous liquors and wines. 93. Effects of Alcohol ; Intoxication. — Alcohol is a poison, and the proof of this assertion is clear when the ordinary effects of liquors containing it are considered. When a person takes so much of an alcoholic drink that he feels the effects of it, he is somewhat exhilarated, the pulse is quicker and stronger, the face is flushed, his ideas seem to flow more freely, he is more cheerful and happy, and he seems brighter than before. And yet, even in this very first stage of intoxication, a close observer can see that a poisonous effect has been produced upon his nervous system. His judgment is weakened, his control over his thoughts is slightly lessened, and things, which when strictly sober he conceals, often come to the light in his conversation. In brief, he is beginning to lose the mastery of him- self. If more alcohol is taken, the brain becomes more and more oppressed, he loses control of his muscular movements, he mumbles in his speech, talks nonsense, and finally becomes unconscious. The poison, however, if enough has not been taken to kill, is gradually ejected from the body, through the lungs, skin, and kidnevs, and the paralyzed organs begin to recover. When consciousness re- turns, the person is dreadfully sick with a throbbing headache and nauseated stomach, which only recover their normal condition after a more or less pro- longed period of rest. Surely such effects are not those of a food, but of a rank poison. STOMACH-DIGESTION. 75 94. Narcotic Poisons. — But the more remote effects of alcohol are even more striking and of greater importance. It is not only a poison but a narcotic poison. It belongs to the same class with opium, chloroform, ether, hydrate of chloral, etc. ; the great peculiarity of which is, that they never leave the body, through which they have once passed, in quite the same condition in which they found it. The person who has once taken them is apt to feel a desire to take them again. And this desire is not like the ordinary appetite for food : it is not that their taste or smell is agreeable, for as a rule the reverse is the case. It is the after-effect that is sought. The oftener this desire is gratified, the stronger it becomes, until finally the man is no longer master of himself, neglects his daily affairs, and takes no interest in anybody or anything but plans for obtaining a fresh supply of the poison. 95. First Symptoms of Narcotism. — This evil effect of the narcotic poisons does not follow unless enough has been taken to produce the first symp- toms of narcotism, which is really the only agree- able stage, and is characterized by a curious sort of tingling all over the body, somewhat as if the run- ning of the blood could be felt in the blood-vessels. Indeed, it is probably caused by the contact of the alcohol with the millions of cells that compose the body, and is the symptom of commencing paralysis.* When this sensation is felt, too much alcohol has al- ready been taken, and poisoning has begun. 06. Effect of Alcohol on Growing Persons. — Be- * The flushing of the face and the more rapid action of the heart are due to the paralyzing effect of the alcohol on the vaso-motor nerves, which will be described hereafter. j6 ORGANS OF REPAIR. sides this danger connected with the use of alco- holic drinks, which is common 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, as heretofore shown, and, {he 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 forms, is particularly injurious to young persons, as it retards their growth, and stunts both body and mind. 97. Effect of Habitual Excess in the Use of Al- cohol. — When alcohol is used habitually in quanti- ties sufficient to produce symptoms of poisoning, it causes serious changes in many parts of the body, especially in the stomach, liver, kidneys, and blood- vessels. The habitual drinker is therefore never in good health, and never lives to be old.* 98. Alcohol diminishes the Power of Endurance. — It has been amply shown by Arctic explorations and by military campaigns in India and Africa, that those who use no alcohol endure privation, fatiguing labor, and extremes of temperature much better than those who take daily rations of grog. The common opinion that alcoholic liquors ward off the cold and temper the heat arises from the fact that the bodily sensations are dulled by the narcotic ; * It is not to be inferred, from what has been said, that every person who uses alcoholic stimulants will become a drunkard, but it can not be denied that every such person runs a risk of becoming one. Not every one who goes into battle is killed or even wounded, but every one in- curs danger. Alcoholic drinks are not necessary to healthy persons, and the habitual use of them is like playing with fire near a keg of gunpowder. No harm may result, but it is a foolish thing to do. STOMACH-DIGESTION. yy the drinker, in other words, is partially anaesthe- tized, so that, although he feels cold and heat in a less degree, he is really less able to resist them. It is found, also, that even moderate drinkers are more likely to be attacked by epidemic dis- eases, that they do not bear surgical operations so well, that they suffer more from exposure of any kind, and that they are apt to succumb to diseases from which the abstinent generally recover. 99. Tea and Coffee. — Tea and coffee are found to stimulate the nervous system, producing slight exhilaration and relieving exhaustion without the subsequent depression that follows the use of alco- hol. In excess, however, they produce nervous disorders, and, although the moderate use of them is not harmful to adults, their influence upon the nerves, the most impressionable part of a growing person, renders them unsuitable articles of diet for the young.* 100. Confectionery. — Confectionery is not injuri- ous, when pure, unless taken in excess. Unfortu- nately, it is frequently adulterated, and, instead of containing simply sugar, flour, gum-arabic, and such harmless substances, is mixed with terra alba (gypsum), because it is heavy and cheap. Poison- * Of tobacco, it may be said that, although it is a poisonous weed, and, when first used, produces alarming symptoms of nervous prostra- tion, it is soon tolerated by the system, and becomes a source of great comfort and satisfaction to those who use it habitually. The excessive secretion of saliva, however, in those who chew it, produces extreme thirst, and may thus lead to the habitual use of alcoholic stimulants ; while tobacco-smoke, constantly irritating the mucous membrane of the throat and nose, produces chronic catarrh of those parts. It is said that no habitual smoker has a healthy throat. It has been abundantly shown that the habitual use of tobacco stunts the growth, and it should therefore be shunned by the young. 78 ORGANS OF REPAIR. ous coloring-matters are also used. All candy that has a gritty feeling in the mouth should be rejected, and bright-yellow, orange, and green candies are to be looked on with suspicion, for they are almost always colored with chromate of lead. 101. Danger of Parasites in Food. — A word of caution is necessary about the eating of pork. This meat occasionally contains millions of minute para- sitic worms, called the trichi'na spira'lis, and, if such meat is eaten without killing these worms, they are set free in the alimentary canal, bore their way into the blood-vessels, and are carried by the current of blood all over the body. When they come to ves- sels so small that they can not pass, they are stuck, dam up the blood-current, interfere with the circu- lation, and produce serious and often fatal disease. These parasites are killed by a temperature of 160 Fahr., and pork, therefore (including ham, of course), should never be eaten unless it is thoroughly cooked.* Briefly, then, to keep the stomach healthy, masti- cate the food thoroughly, eat when you are hungry, avoid overeating and eating between meals, eat plain food, do not spur the stomach with condiments or appe- tizers, and use alcoliolic drinks and tea and coffee, if at all, with the greatest moderation and caution. * The flesh of the pig occasionally contains another parasite, called the cysticer'cus celluld see, which, if taken alive into the stomach, devel- ops into the tape-worm. This parasite, like the trichina, is killed by thorough cooking. CHAPTER IV. INTESTINAL DIGESTION. 102. The Chyme. — After the partially digested food has passed out of the stomach into the intes- tine, it undergoes still further changes, and the difficulties of investigation in this part of the body are so enormous that very little progress has been made toward a clear explanation of what takes place there. Enough has been learned, however, to give us a general idea of how the process of di- gestion is completed. We have seen that the fats and the starches are not digested in the stomach. The gastric juice does not act upon them at all, and they pass into the intestine in very much the same condition in which they enter the stomach. The fibers and tis- sues which hold the fats and starches together, being nitrogenous in their nature, are acted upon in the stomach and dissolved, so that the fat is set free and floats in globules like those upon the sur- face of a kettle of soup. The food thus prepared to pass into the intestine forms a thick, turbid, gray- ish fluid, called the chyme. 103. The Intestines. — The small intestine, into which the food passes from the stomach, is a tube about twenty feet in length, and an inch in diame- 8o ORGANS OF REPAIR. ter. It is composed, like the stomach, of three layers, the innermost one being mucous membrane, the middle one muscular fibers, some of Avhich are circular and some longitudinal, and the outer layer serous membrane.* The small intestine is connected with the large one by a valve-like opening situated in the vicinity of the right groin. The large intestine passes from this point upward to the liver, thence across to the left side, and then downward, constituting the last five feet of the alimentary canal. f 104. Muscular Fibers of Intestine. — The muscular fibers of the intestine contract with a worm-like motion, which always begins near the stomach, and extends slowly along the whole length of the intes- tine, gradually emptying it of its contents. In this * The outer membrane of the in- testine of animals, when separated from the rest, is used for sausage-casings, and, when properly prepared, also makes what is called gold-beater's skin. \ The beginning of the large intes- tine is situated in the right groin, and forms a sort of bag or pouch, called the ccBcum. From one side of this pouch there projects a slender tube re- sembling the intestine in structure, and about six inches long. This is called the appendix vermiformis, i. e., the worm-like appendage (Fig. 27). In man it seems to be entirely useless, and is in fact a constant source of danger ; for occasionally small objects, like cherry-pits and grape-seeds, which are swallowed with the food and not di- gested, become lodged in it, and grad- ually produce an irritation which results in an abscess, and destroys life. Such cases are not uncommon in medical practice. Fig. 27. — Junction of the small and large intestines, and the appendix vermiformis. The large intestine (here called the ctzcum) is cut away so as to show the internal openings. INTESTINAL DIGESTION. 8l slow passage of the food from the stomach through the small intestine to the large one, it is mingled with various fluids which complete the process of digestion, and the nutritious portions of the mass are absorbed and carried away by the blood and other vessels. 105. The Duodenum. — The first eight or ten inches of the small intestine are somewhat larger than the remainder, and are called the duode' uum, because its length is about twelve fingers' breadth. Into this duodenum empty small canals from two very important organs, viz., the pan'crcas and the liver. 106. The Pancreas. — The pancreas (Fig. 28), Fig. 28. — The pancreas, partly cut away, so as to show the duct, which collects the pancreatic juice, and empties it into the duodenum. which we call the sweet-bread when we cook it for food,* is about six inches long, is shaped somewhat * There are three kinds of sweat-breads, viz. : the thyroid-gland, or throat sweet-bread, which is tough, almost like India-rubber ; the pancreas, or belly sweet-bread, which is more tender, and is quite com- monly used ; and the thymus-gland, or breast sweet-bread, which exists only in young animals, wasting away as they grow up. This gland is situated just behind the upper portion of the breastbone, at- tains its greatest size in human beings at the age of two years, and disappears before the sixteenth year. Its use is not known. This 82 ORGANS OF REPAIR. like a pistol, and is situated behind the stomach, with the large end, or the breech of the pistol, toward the right. It secretes a fluid, called the pancrcat'ic juice, which has been shown to be the chief agent in the digestion of the fatty portions of the food. If a quantity of oil be shaken up with pan- creatic juice, a white, opaque, creamy fluid is formed, in which the drops of oil or fat are not visible any more than they are in ordinary milk or cream. Mi- croscopic examination, however, shows that the oil is not in any way decomposed, but is divided into very minute particles, in which condition it can be absorbed by the proper channels. In this way fat is taken up into the circulating fluids in its own proper form, and does not undergo decomposition until it reaches other parts of the body, if at all. The pancreatic juice also liquefies the nitrogenous matters which may have passed the pylorus undi- gested, as well as the starches. In fact, it seems to be the chief agent in completing the act of diges- tion, which has begun in the stomach. 107. The Liver. — The liver (Fig. 29) is a very large organ, the largest and heaviest in the body, weighing in a healthy adult from three to four pounds, and situated on the right side, protected by the lower four or five ribs. It secretes the bile, and from its size, and the amount of its secretion, is evidently one of the most important organs in the body, and yet its precise use is still a matter of dis- pute and doubt. 108. Liver-Sugar. — It was long supposed that the only function of the liver was to secrete the bile ; but gland, taken from calves and lambs, is the most tender and palatable sweet-bread of all. INTESTINAL DIGESTION. 83 it has been found, in recent years, that it also forms a kind of sugar in large amount. The blood which enters the liver is found to contain a small amount Fig. 29. — Under surface of- the liver. of sugar, while that which flows away from it, after having circulated through it, always contains sugar in considerable quantity. Even this fact, well estab- lished as it seems to be, is still a subject of dispute among experimental physiologists. 109. The Bile. — The bile is a somewhat glutinous fluid, of a rich, golden-red color," which is dis- charged into the duodenum through the same open- * When vomiting takes place and lasts for a time, the intestines reverse their action, and bile is carried backward through the pylorus into the stomach. It is here out of place, and produces extreme nausea. Its color is changed by the gastric juice to a greenish yellow. 8 4 ORGANS OF REPAIR. ing with the pancreatic juice.* It must, therefore, become mingled with the food long before digestion is completed. The natural inference from this is that it has something to do with the process ; but the digestion of every portion of the food can be accounted for in other ways. Nitrogenous matters are digested in the stomach, while the fatty mat- ters and the starches are digested by the pancre- atic juice, assisted, perhaps, by the intestinal juices, to be hereafter spoken of. It would appear, then, that there is nothing left for the bile to do, and that it must be an excrementitious fluid — i. e., that it consists of matters which have been separated from the blood by the liver because they are hurt- ful to the organism, and must, therefore, be ex- pelled from the body. This was the ancient view, and it seemed to be supported by the fact that, if the liver be diseased so that this separation can not take place, and the constituents of the bile re- main in the blood, jaundice occurs, and, if there is no relief, the person dies with all the symptoms of poisoning. So far, it seems plain enough that the bile has no office to perform in the body, but is only secreted to be expelled. But operations have been performed on animals in such a way that the action of the liver should not be interfered with, and yet the bile should not enter the intestine, but should be discharged outside the body through an artificial opening. Under such circumstances, if * As soon as the partially digested food, containing a certain amount of gastric juice, passes the opening of the bile-duct, there is a great gush of bile into the intestine. It is found that any acid, applied to this opening, will produce the same effect. The bile, being alkaline, neu- tralizes the gastric juice, which is therefore of no further use, and so the digestive process has to be completed by other means. INTESTINAL DIGESTION. 85 the bile be simply an excrementitious fluid, its dis- charge from the body by one channel rather than by another ought not to make any difference in the health of the animal. But it is found, on the con- trary, that animals treated in this way die with every appearance of starvation. Their appetite re- mains good, their digestion is not interfered with ; but, nevertheless, although they eat ravenously, and are plentifully supplied with food, they become rapidly emaciated and die in about a month. These facts show conclusively that the bile has some important part to play in the nutrition of the body. It is found, moreover, by actual chemical exami- nation of the excretions, that the bile, although it is discharged into the intestine, does not all leave the body. It must, then, be reabsorbed into the circulation. But, if this be so, why does it not give rise to symptoms of poisoning, just as if it were prevented from leaving the blood in the first place ? The only possible answer to this is, that it is some- how changed in the intestine, so that when it is reabsorbed it is harmless. no. The Intestinal Juices. — Besides the bile and pancreatic juice, the food meets in the small intestine with the intestinal juices proper. Of these very little is known with certainty, owing to the great difficulty of obtaining them from the living animal unmixed with other fluids. The small in- testine is lined, however, with a mucous membrane containing millions of small tubules and glands, which secrete certain colorless alkaline fluids. Of these fluids it is both affirmed and denied that they possess the property of turning starch into sugar 5 86 ORGANS OF REPAIR. with great rapidity ; but, so far as is known, their part in the process of digestion is not important. in. Absorption of Food. — If animals are killed at different times after the eating of food, and dif- ferent portions of the intestine are examined, it is found that, while the upper portion of the small intestine contains a large amount of partially-di- gested food, the lower portion contains the shriv- eled remnants of muscular tissue, the husks of grains, the woody, indigestible fibers of vegetables, etc. ; in short, the unappropriated residue of the food which has been taken. The great mass of what has been eaten has disappeared, and after a certain time the whole intestine will be found empty. There are two systems of vessels by which this absorption of food is accomplished — they are the blood-vessels and the lacteals* 112. The Peritonaeum. — To understand the ar- rangement of these vessels, it is necessary to know something of the peritonce'iim. The serous mem- brane, which has been spoken of as covering the outside of the stomach and intestines, covers to a greater or less extent all of the organs contained in the abdomen, and also lines the abdominal walls. This smooth, satiny membrane is called the peri- tonaeum, and it renders the movements of the ab- dominal organs possible without discomfort to the rest of the organism. Now, the intestine being, as has been shown, a long, narrow circular tube, or canal, and the peritonaeum passing entirely around it, there is a line running the whole length of the * Lacteals, from a Latin word meaning milk, because when they are filled with the products of digestion they look as if they were filled with milk. INTESTINAL DIGESTION. 87 intestine, where the membrane becomes double, and this double fold is brought together like the gathers of a dress, and attached to the spinal col- umn. So the intestine is loose in the abdomen, and still has an attachment to the spinal column. Be- tween these two folds, or, in other words, within the double fold, between the two layers of mem- brane, the blood-vessels and lacteal vessels pass to the intestine (Fig. 30). Fig. 30. — Diagram representing across section of the small intestine, show- ing the three layers, and the way in which the blood-vessels pass be- tween the two folds of serous membrane (the peritonaeum). These vessels grow smaller and smaller and more and more numerous as they approach the intestine, and, when they at length enter its walls and penetrate to the mucous membrane, they di- vide into vessels so exceedingly minute as to be invisible to the naked eye, and fill the interior of the little projections of the mucous membrane, which are called villi. 113. The Intestinal Villi. — The villi are small projections on the surface of the mucous mem- brane, about a thirtieth of an inch long, and thickly 88 ORGANS OF REPAIR. covering the whole interior of the intestine, there being about ten thousand of them to the square inch, and about four million altogether (Fig. 31). Each villus is covered with epithelium, and in its interior is a compli- cated mass of blood-ves- sels, twisted and knotted like a bunch of earth- worms (Fig. 32). In the very center of the whole is an open space, which is the commencement of a lacteal. 114. The Lacteal Vessels. — The lacteals are only a part of a sys- FIG 31-Section of the mucous mem- tem Qf vessel caU d th brane of the small intestine, show- § ' # ing two villi, and several secreting fymphat' US, which extend tubes or follicles; also lacteals, every where throughout the body. The lym- phatics all begin in a way that is not clearly understood, and gradually unite to form larger and larger vessels, until their contents are finally discharged into the veins and mingled with the blood. The fluid found in the lymphatics, called lymph, is yellowish, transparent, and saltish, and is presumed to be derived in some way from the change constantly taking place in the tissues. At certain intervals in their course, the lymphatic vessels are interrupted by small bodies called glands* varying in size from a hemp-seed to blood-vessels, and, at the bottom, the muscular layer. * The lymphatic glands are the bodies that sometimes undergo INTESTINAL DIGESTION. 8 9 an almond, into which the vessels enter, and from which they emerge. Whether they actually pass through the gland, or whether one vessel ends in it and another begins, is still a subject of dis- cussion. But the lymphatic ves- sels all over the body have great absorbing power, taking up in- discriminately foods, poisons, or the waste of used-up tissues. The lactcals, then, are that portion of the lymphatic system which is connected with the small intestine, and all the lac- teals from the villi gradually unite to form a vessel called the tJwi-ac'ic duct, about as large as a goose-quill, which passes up close to the spine, and empties into a large vein very near the heart.* 115. The Portal Vein. — The blood-vessels which absorb the food from the intes- tines are veins, and they unite with the veins from the stomach, pancreas, and spleen, to form one large vein, called the portal vein, which enters the liver, so that all the blood from the digestive apparatus slow inflammation in persons of a scrofulous tendency, forming hard lumps or abscesses in the neck. * Many years ago, a man named Calvin Edson became extremely emaciated without any known cause. He was exhibited for a long time as " the living skeleton." After his death it was found that his thoracic duct was completely obstructed, so that none of the contents of the lacteals could pass into the blood. He died, therefore, of fat- starvation — i. e., a complete or almost complete deprivation of fat. Fig. 32. — Intestinal villus, showing the epithelial cells outside, the blood- vessels, and the begin- ning of a lacteal vessel. 9 o ORGANS OF REPAIR. passes through the liver before it enters the general circulation. 116. The Chyle. — The villi, then, projecting as they do into the interior of the small intestine through its entire length, are continually bathed, during digestion, in the nutritious fluid which other organs have prepared for absorption. They float and sway about in this fluid, and suck it up as the roots of a tree get their sustenance from the soil,* and the blood-vessels probably have quite as much to do in the process as the lacteals. The latter ab- sorb mostly the fatty matters in the cream-like form to which they have been reduced by the pancreatic juice. As the walls of the vessels are thin and transparent, the creamy contents, called the ckyle, show through, and hence arises the white appear- ance during digestion which has given them the name of lacteals. 117. Changes in the Blood during Digestion. — * The latest researches seem to show that the lacteal begins in the interior of the villus as a sort of hollow space, without any special wall of its own, and that around this space there are small fibers of in- voluntary muscular tissue. It is believed that, during the process of ab- sorption, these muscular fibers contract at regular intervals. The effect of the contraction would be to pull down the top of the villus toward the base, and thus diminish the size of the hollow space above referred to, and empty its contents into the lacteal vessel. When the fibers relax, and the hollow space expands to its original dimensions, the fluid which has been forced into the lacteal is prevented from being sucked back again by the valves, with which all lacteal vessels are provided. The space is therefore filled again by the fluids which surround the end of the villus in the intestinal canal. In this way, by the alternate and regular contraction and relaxation of these minute muscular fibers, the villus acts like a suction-pump, and the intestine may be looked upon as lined with millions of microscopic suction-pumps, which work away during digestion, pumping the contents of the intestine into the lacteals, by which they are discharged into the blood. INTESTINAL DIGESTION 91 As absorption goes on, the blood becomes more and more loaded with fatty matters, which can easily be recognized in it in the form of minute oily drops, but all of this blood passes through the lungs before it goes to the rest of the body. In its pas- sage through the lungs, the fatty matters disappear in some way, not exactly understood, and the blood which comes away from the lungs contains none. After a time, however, as digestion progresses, the blood is so heavily charged with these oily matters that they can not all be decomposed, and a portion remains and is sent in the general circulation all over the body. If blood be drawn from a man or other animal at this time and allowed to stand, there will be a yellowish, creamy layer on its top. Presently, however, the fat begins to disappear, as digestion approaches its close ; the amount in the blood gradually diminishes, until it is entirely gone, the lymph in the lacteals becomes once more a transparent fluid, and digestion is complete. 118. The Spleen. — At the left extremity of the stomach, just under the ninth, tenth, and eleventh ribs, is an organ which is to this day a great puzzle to physiologists. It is called the spleen, and is about five inches long, four wide, and an inch thick. It is reddish in color, soft and pulpy in texture, with a very tough and strong fibrous covering. It re- ceives its blood from a very large artery, and its vein, which carries away the blood from the organ, joins the portal vein, so that the blood from the spleen, like that from the other organs of digestion, passes through the liver, before it reaches the heart. The spleen is large in well-fed animals, and very small and shrunken in starved ones, while in some Q2 ORGANS OF REPAIR. cases of disease, such as fever and ague, it reaches the enormous weight of twenty pounds, and forms an immense hard tumor in the left side. The facts just stated would seem to imply that the spleen has some important office to perform in digestion, but what that office is no one has been able to discover.* It is a singular fact that the spleen may be entirely removed from animals with- out permanent injury to their health. This opera- tion has often been done to dogs, and the animal recovers from the wound very rapidly. He shows, however, an enormous increase of appetite, usually gains considerable flesh, and acquires an unnatural ferocity of disposition. These things, however, do not seem to indicate that any particular function has been lost to the body, and the uses of the spleen are still a subject of earnest investigation. * The most reasonable theory about the spleen at present seems to be that it has something to do with the destruction of old and worn- out blood-corpuscles and the formation of new ones. CHAPTER V. THE BLOOD. 119. The Blood. — After the nutritious portions of the food have been taken into the blood, they pass through the lungs before they go into the general circulation. Before we consider the respi- ration, however, it is necessary to know something of the circulating fluid. The blood is a thick, opaque fluid, varying in color in different parts of the body from a bright scarlet to a dark purple or even almost black. It has a somewhat viscid feel, a faint odor peculiar to itself, and a saltish taste. 120. The Red Blood-Corpuscles. — If a drop of blood be placed under the microscope,* immense numbers of small bodies will be seen, which are called the blood-corpuscles (Figs. 33 and 34). They are very minute, averaging only gg 1 ^ of an inch in diameter, and are flattened in their shape. They may be described as looking like a cylindrical ring, the center of which has been filled up, but not quite to the level of the border, so that there is a slight depression on each flattened side. Taken singly, * Prick the end of the finger with a pin. The most minute drop of blood is sufficient. Put it on a glass slide under a thin glass cover, and place it under a microscope. 94 ORGANS OF REPAIR. these bodies, called the red blood-corptiscles, are of a light amber color, but in a large mass they give the characteristic red col- or to the blood. They vary somewhat in size in differ- ent animals, those of the monkey approaching most nearly to those of the hu- man being. In birds, rep- tiles, and fish, they are very much larger, and in- stead of being circular are oval (Fig. 35).* They also have a distinct nucleus. It is mainly by these microscopical differences that the blood of different animals can be distinguished Fig. 33. — Human blood-corpuscles, including two white ones. Fig. 34. — Human blood-corpuscles (highly magnified). From a photograph. * The blood-corpuscles of the camel tribe are also oval, but smaller than those of birds. THE BLOOD. 95 *&■'■>. WHITE Yig. 35. — Blood-corpuscles of the frog. from that of man, as is sometimes necessary in trials for murder. 121. The White Blood-Corpuscles. — The blood also contains white corpus- cles in the proportion of one white corpuscle to three hundred red ones. They are larger than the red, are perfectly colorless, and glo- bular in their form. The white corpuscles, under proper conditions, are seen to be continually changing their form, almost like liv- ing animals. There have been many speculations as to their office in the body, but nothing definite has been ascertained. In certain diseases, however, they are found to increase enormously in number, and some of these diseases are among the most dangerous and difficult to treat of any the physi- cian meets with. Although the blood-corpuscles are so very mi- nute, they exist in such enormous numbers that they are estimated to compose half the mass of the blood. 122. The Plasma. — The fluid portion of the blood, in which these small bodies float, is called the plasma. It is almost colorless, quite transpar- ent, and is nine tenths water. Its two most im- portant ingredients are albumen and fibrin.* The * It is now believed that fibrin does not exist, as such, in fluid blood, but that there are certain substances (known as fibrino-plastin or paraglobtdin, fibrinogen, and fibrin-ferment) which, by their inter- 96 ORGANS OF REPAIR. former of these is chiefly concerned in nutrition, and the latter brings about the remarkable phe- nomenon known as coagulation. The plasma also contains various compounds of lime, soda, mag- nesia, etc., which have their own functions to per- form in the nourishment of the body. 123. Coagulation of the Blood. — If blood be drawn from the living body, it very soon under- goes coagulation. This is due to its fibrin (or fibrin- factors) ; but the cause of the change is very im- perfectly understood. After the blood has stood for a few minutes outside the blood-vessels, it at first becomes less fluid and assumes somewhat the appearance of jelly. Shortly the fibrin begins to contract and occupy a smaller space, gradually squeezing out the portion of the blood which still remains fluid. This mass which separates from the rest of the blood is called the clot, and the remainder, or still fluid portion, is called the scrum. The con- traction of the clot continues for several hours, until it forms quite a firm mass of a deep-red color, the remaining fluid being transparent and nearly colorless. The red color of the clot is due to the fact that the red corpuscles become entangled in the coagu- lated fibrin, and, being semi-solid in consistency, they remain there and are not pressed out with the serum. It will be noticed that the scrum is not the same as the plasma. The latter includes the fibrin (or fibrin-factors), while the former is without it. 124. Coagulation under Varying Conditions. — It is found that the blood coagulates more rapidly in action, produce fibrin, and so cause coagulation. The evidence for this view is of too abstruse a nature to be given here. THE BLOOD. 97 thin layers than in a large mass ; in a vessel or on a surface which is rough than in one which is smooth. For this reason the blood flows longer from a smooth cut in the body than from a wound with torn and ragged edges. In the latter case the blood coagulates very rapidly and stops the hemorrhage. But the coagulation of the blood takes place not only outside the body, but, under similar circum- stances, inside, though not always with equal ra- pidity. If a vessel bursts inside the body, and blood escapes into the tissues around it, coagula- tion takes place after a short time ; and this occurs even inside the blood-vessels, if there be any ob- struction to the circulation. If an artery or vein be compressed by a string or wire or finger, the blood will soon coagulate in the vicinity of the pressure. These facts have suggested the means used by surgeons to stop the flow from a bleeding wound, and will be referred to again. 125. Total Amount of Blood. — The total amount of blood in the human body is believed to be about one twelfth of the whole weight of the individual. Thus, in a man who weighs one hundred and fifty pounds there will be about thirteen pounds of blood, or somewhat more than a gallon and a half. 126. Oxygen in the Blood. — This rich, nutritious fluid is forced to all parts of the body in a way here- after to be described, carrying food to exhausted tissues and removing the used-up matters. A large part of the material necessary for the growth and nourishment of the body is taken in through the digestive, organs ; but there is a gas absorbed by the blood, in its passage through the lungs, which is even more necessary to life than food. This gas 9 8 ORGANS OF REPAIR. is oxygen, which constitutes about one fifth of the atmosphere, and is essential to the life of all animals, probably without exception. We can live for days without food, but we can not live ten minutes with- out oxygen. Even water-animals are not exempt from this law; for fish extract the air, which is in solution in the water, by passing it through their gills. If a dish of water containing a fish be placed under the receiver of an air-pump, and the air be exhausted from it, the fish will be as surely drowned as a man would be if held under water. This is the reason why fish which are kept as pets in aquaria need fresh water continually. If a jet of water be kept falling into the vessel in which they live, so as to drag down bubbles of air, the water need never be changed, except for cleanliness. 127. Varying Color of the Blood. — The blood which enters the lungs is very dark, and sometimes almost black. When it has passed through the lungs, and flows away, it is of a bright scarlet. It has lost certain substances and gained others during this passage, and this beautiful and surprising alter- ation is produced by what is called the process of respiration. CHAPTER VI. RESPIRATION. 128. Respiration a Complicated Process. — At first sight, the process of respiration is a very sim- ple one, consisting merely in the inspiration and expiration of air. In reality, however, it is compli- cated — certain very essential parts of it going on without our consciousness, like so many of the phe- nomena of digestion. The organs mainly concerned in the acts of respiration are the lungs ; but there are certain additional organs, whose functions, if not absolutely necessary, are certainly important. 129. The Nasal Passages. — The air, before reaching the lungs, goes through several passages, lined throughout with mucous membrane. The human being can breathe through either the nose or the mouth ; but in some animals (the horse, for instance) respiration only takes place through the nose, and, if this be closed, suffocation follows. The external openings of the nose are guarded by short, stiff hairs, which grow just inside the nostrils, and which serve to purify the air somewhat, as it passes through them, by catching and retaining particles of dust. The interior of the nose is so formed that it is not a large, open, free passage, but has a num- ber of projecting bones, running lengthwise along 100 ORGANS OF REPAIR. its walls, which are covered with moist membrane and present an extensive mucous surface to attract particles from the air. If we breathe through the mouth, on the other hand, the air goes directly to the throat, and the cavity of the mouth is so large that the purifying effect of the moist membrane is hardly perceived. This shows how much better it is to breathe always through the nose ; for the air, undoubtedly, in this way, is rid of many impurities ; and physicians habitually, and almost unconsciously to themselves, keep their mouths shut as much as possible when they are exposed to a contagious disease. From the nose the air arrives at the throat, and thence it passes into the windpipe, or trachea, through a small opening called the glottis. 130. The Trachea. — The tra'chca (Fig. 36) is a tube about four and a half inches long and an inch wide, which divides at its lower extremity into two smaller tubes called bronchi, one of which goes to each lung. It is mainly fibrous in its structure, and it is kept open to its full extent by a number of rings of cartilage, placed at a short distance apart through its whole length. The trachea is situated in the neck just in front of the oesophagus, and as these stiff rings might press backward on the oesophagus, and thus interfere with the process of swallowing, they do not pass completely around the trachea, but are lacking in the part next the oesophagus, comprising about one third of the whole circumference of the tube. At the upper extremity of the trachea is the lar'ynx, or the organ of voice, which is essentially a triangular-shaped box of cartilage, the lower end opening freely into RESPIRATION. 101 the trachea, and the upper being closed by muscles and membranous tissues, with the exception of the opening of the glottis. Fig. 36.— Larynx, trachea, and bronchi, showing the manner of division, and the rings of cartilage. 131. The Glottis. — The glottis is a slit-shaped opening, a little less than an inch long, extending from before backward and from above downward, 102 ORGANS OF REPAIR. not being, in other words, either perpendicular or horizontal in the throat, but shelving toward the rear. The front extremity is at the base and back of the tongue, and the opening itself is bounded at the sides by two firm, fibrous, strong, pearly-white membranes, called the vocal chords, by the vibration of which sound is produced. These vocal chords can be separated to the extent of half an inch, or brought together so as to touch, by the muscles which are attached to the back part of the larynx. The production and modulation of the voice will be treated of hereafter. At the base of the tongue, springing upward just above the forward end of the glottis, is a stiff piece of cartilage, shaped like a leaf with a rounded end. This is called the epiglottis, and probably performs two functions, viz., that of protecting the glottis from food or other substances during the act of swallowing, and that of directing the column of expired air up toward the roof of the mouth or throat, and so aiding in the modulation of the voice. 132. The Lungs. — The essential organs of res- piration are the kings, which are two in number and fill nearly the whole cavity of the chest, a portion, however, being occupied by the heart and large blood-vessels. The lungs are very light in propor- tion to their size, and in animals they are common- ly called " the lights." They weigh together only about two pounds and a half, and easily float in water. In small children they are of a beautiful pinkish color, but in older persons they become slate-colored, and have black spots scattered here and there over their surface. RESPIRA TION. 103 Fig. 37. — Section of a pulmonary lob- ule, showing- its division into pul- monary vesicles. 133. Minute Divisions of the Lungs. — After the trachea divides into two bronchial tubes, one of which goes to each lung, these bron- chial tubes continue to subdivide in- to smaller and smaller tubes, all the branches diverging widely from each other, until their diameter is diminished to about -fa of an inch. At about this point the cartilage rings disappear, but the tubes still divide until the smallest are only -fa of an inch in diameter. At the very ends of the smallest tubes, there is an enlargement about -fa of an inch in diameter, called a pulmonary lobule (Fig. 37). It constitutes a small cav- ity, into which dip little partitions, that do not meet each other, but create minute hollow spaces around the sides of the lobule, called pulmonary vesicles. These are about fa of an inch in diameter, and are the smallest divis- ions of the lung. 134. The Lining Membrane of the Lungs. — All these tubes and passages, down to the most minute, are lined with a delicate mucous membrane, which has this remarkable peculiarity. The little epithelial cells with which all mucous membranes are covered, have in this situation what are called cilia at their ends (Fig. 38). That is to say, each cell has at its tip a fine, hair-like lash, which keeps in constant motion, as the person lives, and for some time Fig. 38.— Cilia- ted epithelium from a small bronchial tube. The small round cells at the bottom are young ones. as long 104 ORGANS OF REPAIR. after he is dead. If a piece of the mucous mem- brane from a frog's throat be snipped off with a pair of scissors, and then doubled with the natu- rally outer side outward, and placed under the mi- croscope, this incessant motion of the cilia may be easily seen. It is an experiment well worth trying, for it is an astonishing and beautiful sight even to one who has often seen it. The cilia, although they are so delicate in their structure, are so in- numerable and act in such perfect concert, that they keep up a constant current toward the outside of the body. They probably aid in the expulsion of the foul gases which the blood leaves in the lungs. 135. Asthma. — The smaller bronchial tubes, which have no rings of cartilage, are nevertheless surrounded by involuntary muscular fibers. When, in consequence of disease, these fibers contract strongly, they diminish the caliber of the tubes, and render it very difficult sometimes for the sufferer to get air through them in either direction. This condition gives rise to great distress and a sense of suffocation, and is called astlima. 136. The Blood- Vessels of the Lungs. — Between the pulmonary vesicles run the small blood-vessels immediately under the delicate mucous membrane, so that the blood comes almost in contact with the air that we breathe. They surround the vesicles completely, and it is in this part of the lung that the great changes take place in the blood during respiration. 137. The Outer Covering of the Lungs. — The outside of the lung is covered by serous membrane, and so is the inside of the chest-wall. This renders RESPIRATION. 105 the movements of the lung painless and easy. This membrane is called the pleura, and when it becomes inflamed, in the disease known as pleurisy, respira- tion becomes excessively painful. 138. Inspiration. — As the cavity of the chest is enlarged, the air already in the lungs is rarefied, and the external atmospheric pressure forces air in to fill the organs. We have already stated that the ribs are so shaped, and so connected with the spine behind and the sternum in front, that when they are raised up toward the shoulders the sides move outward, and the sternum moves forward. This motion of the ribs is caused partly by power- ful muscles attached to their external surface all the way down the chest, and partly by short mus- cles which pass between the ribs from the lower edge of each one to the upper edge of the one just below it. But, in addition to its expansion toward the front and sides, the cav- ity of the chest is en- larged in a downward direction by the con- traction of the diaphragm (Fig. 39). This muscle has a strong, flat, ten- dinous center, from every side of which muscular fibers pass to the walls of the chest. It separates the chest from the abdomen, and while Fig. 39. — Diagram illustrating the vary- ing position of the diaphragm during respiration. strong I0 6 ORGANS OF REPAIR. the muscular portion of it is attached to the lower ribs, the spine and the very end of the breastbone, the center rises much higher in the chest, so that it has the shape of a vaulted roof, on top of which are the lungs and heart, and underneath the stom- ach and liver. Of course there are passages through it for the blood-vessels and nerves, but these open- ings are so guarded that the diaphragm forms a tight partition. Now, as the center of the diaphram rises so much higher than the sides, it is very evi- dent that a contraction of the muscular fibers will pull the center downward, and so increase the ca- pacity of the chest. And this is what actually occurs at every inspiration. When this contrac- tion takes place spasmodically, the air is drawn into the lungs with a sudden impulse, and we call it hiccough* 139. Expiration. — Inspiration then involves a contraction of many muscles, and they act with a great deal of force, for they have to lift the atmos- phere, which is pressing on the outside of the chest with a force of fifteen pounds to the square inch. By this simultaneous contraction, the ribs are drawn out of their natural position — i. e., they are drawn upward into a position which they never would assume if left to themselves. By the elastici- ty of their cartilages and other tissues attached to them, they tend to return to their former position as soon as the force which has drawn them out of * Hiccough, being due to a spasmodic action of the diaphragm, may be stopped by any means that tends to control the spasm. The easiest method is to put the diaphragm on the stretch, as follows : prolong the act of expiration as much as possible, and at the end make a forcible expiration ; then inspire slowly and take as full an inspiration as pos- sible. It is rare that a second trial will be necessary. RESPTRATIOX. 107 it ceases. The diaphragm, also, when contraction stops, tends to recover its former arched shape. The lungs also contain, in addition to the elements already mentioned, a large amount of elastic fibers, interlaced with the other tissues in every direction. These, too, as soon as the pressure which has stretched them ceases, tend to return to their for- mer condition. This elasticity of the different organs concerned in the act of respiration, then, brings the chest and lungs back to the condition in which they were before inspiration began. This is the ordinary act of expiration. 140. Relative Force of Inspiration and Expira- tion. — As we usually breathe, then, the act of inspi- ration is an active one, requiring effort and power- ful muscular contraction, while the act of expira- tion is passive, and is accomplished by the elasticity of the tissues." Under other conditions, however, the act of expiration may be more powerful than that of in- spiration. There are strong muscles connected with the chest in such a way as to act in opposition to the muscles of inspiration, and make the cavity of the chest smaller than it ordinarily is. It is by the active contraction of these muscles that we pro- duce what is called a forced expiration, which has been estimated by careful observers to be one third more powerful than a forced inspiration. 141. Amount of Air respired with Each Breath. * The outer surface of the lungs is kept in contact with the chest- walls by atmospheric pressure. If the chest-wall be punctured, so that the air-pressure is the same both outside and inside of the lung, the elasticity of the organ is such that it immediately collapses, driving out all the air from its interior. 108 ORG AX S OF REPAIR. — The amount of air taken into the lungs with each inspiration is about twenty cubic indies. Now, the entire capacity of the lungs varies in different per- sons from one hundred and fifty to two hundred and fifty cubic inches or even more. So that with each breath, a very small amount, generally not one tenth, of the air in the lungs is changed. It is even estimated that after the most forcible expira- tion possible, at least one hundred cubic inches of air will remain in the chest of a man of medium size, which can not be expelled. In ordinary breath- ing, therefore, only the air in the larger bronchial tubes can pass in and out of the lungs. But the changes in the blood must -be produced at the ex- treme end of the finest tubes in the pulmonary vesicles. So the question arises, How does the air get to the vesicles ? 142. How the Air in the Lungs is changed. — In the first place, the law of the diffusion of gases comes in play. When two gases come together, they tend to mingle with each other until they finally occupy equally the whole of the vessel or other confined space in which they may be. After the mixture, each gas will be found in the same proportion in every part of the vessel. Xow, the air in the pul- monary vesicles and smallest bronchial tubes is heavily loaded with carbon dioxide (carbonic acid), while that which is drawn in with inspiration is rich in oxygen. These two gases, then, carbon dioxide and oxygen, are constantly being diffused through- out the whole of the lungs. In the second place, the cilia, which have already been described, being in constant motion, keep up a current of the foul air from the pulmonary vesicles along toward the ~> RESPIRA TIOX. 1 09 larger bronchi and trachea, and fresher air keeps constantly pressing in to fill the place of what has been in this way removed. Thus, in the smallest bronchial tubes, there are always two currents of air passing each other in opposite directions : one, im- mediately next the mucous membrane, being a thin layer moving outward ; and the other, in the center of the tube, moving inward (Fig. 40). So that the air in the larger bronchi and trachea is changed periodically by the acts of inspiration and expiration, while the circulation of the air in the small bron- chial tubes and pulmonary Fig. 40.— Imaginary section of a Vesicles is COntinuOUS. smaU bronchial tube, showing . r a • *-ke influence of the cilia in pro- 143. Amount 01 Air re- ducing an outward current of air. spired daily. — The amount of air taken in with every inspiration is about twen- ty cubic inches. The average number of respira- tions per minute is eighteen. This is a matter which varies very much with the individual. Chil- dren and women breathe somewhat more rapid- lv than men ; but taking eighteen as the average, the quantity of air breathed per minute is three hun- dred and sixty cubic inches, or about one fifth of a cubic foot. In an hour, then, we use about twelve cubic feet of air, and in a day nearly three hun- dred cubic feet. This amount is increased by every muscular exertion, and also by the curious fact that the ordinary respiration does not seem to be alto- gether sufficient for the needs of the body, and every now and then we draw a deeper breath than the average. This occurs usually about once in every five or six acts of respiration. Considering the in- 6 HO ORGANS OF REPAIR. crease in the amount of air respired at each long* breath, and the increase of rapidity of respiration due to slight causes during the day, it is estimated that an adult really respires about three hundred and fifty cubic feet of air per day. 144. Changes produced in the Air by Respira- tion. — When the air enters the lungs it contains nearly 21 per cent of oxygen and 79 per cent of nv trogen, with about one twentieth of one per cent of carbon dioxide, a little zvatery vapor, and a trace of ammonia. If the air be collected at expiration, after having undergone the changes in the lungs, we find the following : 1. // has lost oxygen. 2. It Jias gained carbon dioxide. 3. It contains more zvatery vapor. The watery vapor in the expired air is not or- dinarily visible, but in cold weather, when it be- comes condensed, it can be very plainly seen. The whole amount of water passed away daily in the breath of a man has been carefully estimated, and found to average about one and one sixth pound avoirdupois. 145. Former Theory about the Formation of Carbon Dioxide. — Out of the four cubic inches of oxygen taken into the lungs with each inspira- tion, one cubic inch disappears. The carbon dioxide which is exhaled from the lungs consists of carbon and oxygen united in certain proportions, and it used to be supposed that the carbon in the blood united with the oxygen of the air in the lungs themselves, forming carbon dioxide, and that in this way the carbon, released by the wear and tear RESPIRATION. Ill of the body, was got rid of. Now, the process of combustion in a flame of any kind consists in this same change, viz., the union of the carbon and- hy- drogen of the oil or other inflammable substance with the oxygen of the surrounding air, forming carbon dioxide and water, and giving out heat during the process. So it was for a long time thought that the lungs were a sort of furnace in the body, where the carbon and hydrogen of the blood were burned, so to speak, and the products of com- bustion exhaled, while the heat occasioned by the process kept up the warmth of the body. This was a beautiful theory, but it is found not to be warrant- ed by the facts. There is more oxyge?i absorbed in the lungs, with every respiration, than is exhaled in the carbon di- oxide and watery vapor taken together. This fact of itself disproves the above theory, for it shows that a portion of the oxygen disappears in the lungfs, or is carried away by the blood. 146. Organic Matter in the Breath. — Besides the carbon dioxide given off in the expired air, there is a certain amount of organic matter, con- taining nitrogen, which gives the breath a slight but peculiar odor. Where many persons are breathing in a badly ventilated room, this organic matter accumulates, and imparts to the atmosphere that odor which we all recognize as peculiarly op- pressive and close. 147. Changes in the Blood during Respiration. — The blood undergoes changes in its passage through the lungs which correspond to the changes in the air. In the first place, it is altered in its color. As it enters the lungs, it is of a deep bluish 112 ORGANS OF REPAIR. purple, almost black ; as it emerges, it is of a beau- tiful and most brilliant scarlet. On chemical ex- amination, to determine the cause of this remark- able change, it is found that the blood which comes away from the lungs contains more oxygen and less carbon dioxide than that which enters them. Additional proofs that the formation of carbon di- oxide does not take place by direct combination in the lungs are the facts that the venous blood, before it enters the lungs, is deeply charged with carbon dioxide already formed, and that the blood which comes away from the lungs contains oxygen in free solution. The brilliant color, which is the result of this change in the blood, has not yet been satisfactorily accounted for. It has been proved that the oxy- gen and carbon dioxide are carried by the blood- corpuscles, and not by the plasma, and the change of color in the blood is entirely due to the change in those minute bodies. They have been said to change their shape and become more globular in one case than in the other, but the attempts to ex- plain the difference of color have not yet been en- tirely successful.* 148. Where the Carbon Dioxide is formed. — If the carbon dioxide is not formed in the lungs, then where does it come from ? Experiments of the most ingenious kind have been performed to determine this question, and they are too long to * The coloring-matter of the red corpuscles is called hcemoglobin. It is found that this substance, when united with an excess of oxygen, forming oxyhemoglobin, has a bright scarlet color, and, when the amount of oxygen is greatly reduced, is of a dark purple. But this does not explain much. RESPIRA TION. "3 mention in detail. But it has been conclusively shown that most of the carbon dioxide is formed in the tissues in all parts of the body, during the processes of nutrition. And even here it is not produced by a direct combination of the oxygen with the carbon, for the exhalation of carbon di- oxide will continue for a considerable time in an atmosphere of hydrogen, where of course there is no oxygen furnished to the tissues. The carbon dioxide, then, is formed by decomposition of the tissues, and the oxygen is used by them to build themselves up again. * The amount of carbon di- oxide given off in the breath has been found to be somewhat less than one cubic inch, or about four- teen cubic feet per day, weighing about a pound and a half, and representing waste of the organism to about this amount. 149. Composition of Air. — Air being so essential to life, it is evidently important to have it as pure as possible. It must contain enough oxygen, so that with each respiration the temporary needs of the body may be satisfied, and should contain no substances which are injurious to life or health. Now, the air normally contains about four parts of nitrogen to one of oxygen. It always contains a small amount of carbon dioxide, and a variable quantity of watery vapor.f It is also never found * It will be understood that the place of the carbon which is lost to the body in the carbon dioxide which passes off by the lungs, is sup- plied by the fresh material taken in with the food. f This watery vapor is a very necessary constituent of the air. Out- of-doors the amount of it is regulated in ways beyond our control ; but in-doors, unless special care is taken, the air may be so dried by artificial heat, that when respired it will absorb more than the ordinary amount of moisture from the mucous lining of the lungs. Then the U4 ORGANS OF REPAIR. entirely free from impurities, such as other gases than those named, in small quantity, and minute floating particles of matter, which we group to- gether under the common name of dust. It has been shown, however, that the breathing of animals is continually removing oxygen from the air and increasing the amount of carbon dioxide. Now, carbon dioxide is a poison to animals, and if inhaled in large amount produces almost imme- diate unconsciousness and death. It is for this rea- son that it is being constantly rejected from the body. If this process of removing oxygen from the air and adding carbon dioxide to it were to go on indefinitely, it is evident that after a time the one would be so much reduced in amount, and the other so much increased, that animals would die of carbon-dioxide poisoning — i. e., of asphyxia. 150. Respiration of Plants. — This danger is guarded against in the outer atmosphere by the constant absorption of carbon dioxide by plants. All plants, through their leaves, decompose car- bon dioxide into its original parts, carbon and oxygen. The carbon they appropriate for their own nourishment, and the oxygen they return to the at- mosphere. Thus the respiration of plants is exactly the reverse of that of animals. The latter absorb oxygen and give out carbon dioxide, and the for- mer absorb carbon dioxide and give out oxygen. mucous membrane becomes dry, there is an increased flow of blood to the part, and, if the dryness of the air is not remedied, inflammation may result — i. e., a catarrh. For this reason a vessel of water should always be kept on the top of a heated stove or furnace, that its evapo- ration may insure sufficient moisture in the air to prevent injury to the lungs and throat. RESPIRATION. 115 By this never-ending interchange the proportions of oxygen and carbon dioxide in the atmosphere are kept about the same. 151. Contamination of the Air in Houses. — In- doors, however, there is no opportunity for this self-purification. Even if a few plants are kept in the house, the amount of carbon dioxide they con- sume is very little, and the effect they are able to produce toward purifying the room can not be com- pared with that of the immense stretches of forest and plain out-of-doors. Moreover, the amount of carbon dioxide in houses is increased by combus- tion. A five-foot gas-burner throws out as much carbon dioxide as five men. The unhealthiness of a closed room is also increased by the organic mat- ter of the breath, which is very poisonous.* The odor of this matter is perceptible in a room long before the accumulation of carbon dioxide reaches a point when it is likely to be injurious. It is, there- fore, to be looked upon as by far the most danger- ous impurity in the atmosphere of an occupied room. 152. Ventilation. — In order to forestall any evil result from such impurities, the air of a room should be changed frequently enough to prevent the odor of this organic matter from being perceptible. This usually requires some special attention, and is called ventilation. In warm weather, all that is necessary is to open the doors and windows and allow the air to circulate freely through the house. But in cold * The composition of this organic matter is not known. It is given off in such small quantity that the chemists have never been able to analyze it. It putrefies rapidly after it has left the body, and then be- comes very offensive. Il6 ORGANS OF REPAIR. weather more care is required. A fireplace, with an open fire, is an excellent means of drawing out the foul air — sending it up the chimney, and so out of the house. The fresh air, to supply the place of what has been thus removed, may come in through cracks in the windows and doors. But the fresh air admitted in this way in cold weather, being heavier than warm air, falls and sweeps along the floor. This is very dangerous, for few people can endure a cold draught on the feet and ankles, while the rest of the body is warm, without tak- ing cold. Moreover, the smallness of the apertures through which the air comes increases the ra- pidity of the current. It is better, therefore, to let in the fresh air through a special opening, so ar- ranged that the cold air shall not immediately fall to the floor. This can be done cheaply and effect- ively by raising the lower sash of the window about four inches, and putting underneath it a board, fit- ted to close the opening tightly between the sash and the sill. There will then be a long, narrow opening between the upper and lower sash, through which air will enter in a current directed upward toward the ceiling, and, before it descends, its mo- mentum will be so much diminished that it will not create a draught. In very cold places, where double windows are used, the same result may be obtained by raising the lower outer sash a little, and lowering the upper inner one. The best way, however, is to warm the fresh air before it enters the room ; but this is too large a subject for discussion here. This foul organic matter from the lungs of ani- mals, when it gets out into the open air, is im- mensely diluted, and, being acted upon by the oxy- RESPIRATION. 11/ gen of the atmosphere, is changed into other and less harmful substances, which, in their turn, are washed down by the rain and become a part of the soil. 153. Contagious Diseases. — The air is not only polluted by these products of the respiration of healthy animals, but it is made unfit for breathing, in a way involving still more danger to life, by the matters given off from the lungs and bodies of sick persons. There are certain diseases which are called contagious or infectious, because they can be communicated from one person to another. Such diseases are small-pox, measles, scarlet fever, typhus fever, diphtheria, and perhaps consumption.* It is known that the matters contained in the air expired from the lungs, or, in some cases, specks of matter cast off from the skins, of persons sick with these diseases, will produce similar diseases in persons who inhale them. Exactly what it is that repro- duces the disease is not known, but there is believed to be a microscopic organism, peculiar to each dis- ease, which, like a kind of seed, will always produce that disease by its own growth and multiplication whenever it meets with proper conditions. Whether these little organisms ever grow and multiply out- side of the body we do not know, but that they do so in the blood we have abundant evidence.f * Whooping-cough, mumps, and chicken-pox, are propagated in a similar manner, but are less dangerous. f It is thought by some that malarial fevers (fever-and-ague, etc.) are produced by microscopic organisms of this kind, but this is uncertain. It is well for those who live in districts where such diseases are preva- lent to remember that the poison, whatever it may be, is most active in the spring and fall, at night, and near the surface of the ground. In such a region, and at such a season, therefore, people should not go n8 ORGANS OF REPAIR. There are other diseases which are believed to be produced by similar organisms growing and mul- tiplying in the discharges from the stomach and bowels. Such organisms are believed to grow out- side the body as well as inside, and are supposed to be the cause of Asiatic cholera, typhoid fever, and yellow fever.* 154. Precautions against such Diseases. — It is probable that all of these microscopic organisms (called bacteria, bacilli, micrococci, etc.) which float about in the atmosphere, if they do not find a favor- able place in some animal body, where they can grow and propagate their kind, finally die. If it were not so, the human race would be exterminated by them. But men have two ways of dealing with them so as to prevent their spreading. One is to separate the sick person from well ones, as far as possible, and the other is to kill these little organ- isms as fast as they leave the body and before they can get out of the room. This is accomplished by the use of powerful drugs, called disinfectants. Nurses and doctors adopt special means of ward- ing off infection, or are willing to expose themselves out after sundown, should keep their bedroom-windows closed, and should sleep above the first story. * The discharges from the bowels and kidneys of healthy persons, even, are believed to become dangerous when they decompose, and to cause serious diseases. Microscopic organisms multiply in them with great rapidity, and are disseminated in the surrounding atmosphere. For this reason, it is desirable that such matters should be removed from the vicinity of dwellings as quickly as possible. When they are discharged into sewers, their decomposition produces various gases- some of them very offensive — which are popularly known as sewer-gas, but should more properly be called, collectively, sewer-air. The most dangerous thing about sewer-air, however, is not the offensive gases, but the little organisms that float out with it into the streets or houses. RESPIRATION. II 9 to the risk necessary for the proper care of the sick. If it becomes the duty of any other person to enter- a sick-room, he should have in mind the following- points : that the nose, on account of its narrow pas- sages and extensive moist surface of mucous mem- brane, acts as a sort of filter, so that many impurities of the air are detained there and never reach the lungs, whereas, through the mouth, there is a straight and almost unimpeded course to those organs ; that the body is less able to resist injurious influences of every kind when it is fatigued or in want of a fresh supply of food ; and that matters escaping from the bodies of the sick and floating in the air are likely to settle on articles standing in the room. Hence we deduce the following rules : Never enter a sick-room when you are hungry or tired. Always keep your mouth shut, except when talking. Never eat or drink anything that has been standing in the sick-room. CHAPTER VII. ASPHYXIA. 155. Asphyxia. — When the blood is deprived of its constant fresh supply of oxygen, the carbon dioxide produced in the tissues accumulates very rapidly, and in a short time the blood is brought into a condition in which it can not circulate, pro- ducing asphyxia or suffocation. The blood through- out the whole body then becomes venous. The arteries* as well as the veins are filled with black, sluggishly -moving blood. This black blood shows through the skin, particularly where it is very thin, as in the lips ; and parts of the body which are usu- ally of a healthy red or pink color become blue and livid. This blueness of the lips and of the flesh un- der the finger-nails is, therefore, a sure indication that the person is suffering from a lack of oxygen, and the only thing to do to save life, under such cir- cumstances, is to supply fresh air. In drowning, strangling, poisoning by coal-gas or illuminating gas, this is always the great thing to be aimed at, and, as long as the heart beats, life exists, and con- sciousness can usually be restored. * The arteries are those blood-vessels that carry the bright scarlet blood, which has received a fresh supply of oxygen, and the veins con- vey the dark blood, called venous, which is loaded with carbon di- oxide and other waste matters, as hereafter explained. ASPHYXIA. I2 i 156. Drowning. — The length of time during which a human being may remain under water and still recover, under proper treatment, is not yet act- ually determined. Young persons, it is known, live longer when submerged than older ones. As a rule, however, a person who has been entirely submerged for five minutes is dead beyond the possibility of resuscitation. And yet, even in such cases, attempts should be made, for any case may be an exceptional one.* 157. Resuscitation of the Drowned. — What, then, are the indications for the treatment of a person who is almost dead from drowning? In the first place, he has been for some time de- prived of oxygen. It is this which has made him unconscious. In the second place, he has, probably, in his fran- tic efforts to breathe, taken water into his lungs, where it stops up the bronchi and air-vesicles, and must be cleared out before any air can enter. In the third place, he is cold, and warmth, of itself, will do much toward bringing about his re- covery. In the fourth place, his circulation is at a very low ebb. The blood is so charged with carbon dioxide that it is sluggish, and, possibly, has almost ceased to flow. We must first, then, turn the person on his face, and raise the lower part of the body somewhat, so as to let what water there may be in the lungs run * Unconsciousness sometimes persists for a long time after a person has been removed into fresh air, when no special attempts at resusci- tation have been made. It is said that persons have been restored by artificial respiration after they have lain unconscious and apparently dead for five hours. 122 ORGANS OF REPAIR. out by the force of gravity. This action need oc- cupy only an instant, for, if there beany water there, it will immediately run out. The person should then be laid flat upon the back, without having the head raised, for we want the first fresh blood to run to the brain, and the heart is acting so feebly that it will be unable to send it there if it has to propel it up-hill. The shoulders should be raised a little by a pillow, a folded coat, or other padding. All the clothing should be loosened about the neck, chest, and waist, so as not to inter- fere at all with the movements of respiration. The wet, clinging clothing, if convenient, should be removed entirely, as it tends to keep up the chilliness of the body. In any event, some one should attend to the duty of warming the body, by rubbing it with warm flannels, by bottles of hot water to the feet, etc., etc. In addition to these things, and chief of all, arti- ficial respiration should be kept up until the patient breathes naturally, or until absolutely all hope is lost. 158. Artificial Respiration. — As the person lies upon the back, the arms are to be grasped above the elbows and brought upward above the head, so as to touch, or nearly so. The large muscles of the shoulder are attached to the Avails of the chest in such a manner that this movement of the arms raises the ribs, and expands the cavity of the chest in very much the same way that ordinary respiration does. The chest being thus expanded, of course air rushes in, and inspiration is effected. The arms should now be returned to the sides of the body and pressed against the ribs, when the chest-walls will recover ASPHYXIA. 123 their former position by virtue of their elasticity, and expel all the air which had been taken in. This, it will be observed, is exactly the process of natter al expiration. The rapidity of these movements should approach as nearly as possible to the rapidity of natural respiration — i. e., about sixteen or eighteen movements to the minute, and the drawing- up of the arms above the head should occupy the usual time of inspiration. This process should be continued for hours, if necessary, and the first sign of recov- ery will usually be a slight change in the color of the lips and finger-nails to red or pink, indicating that the circulation and oxygenation of the blood have begun to be more active. 159. Additional Precautions. — During the whole process of resuscitation of a drowned person, care should be taken to keep the mouth and tJiroat clear of mucus and froth by means of a finger covered with a towel. The tongue must also be watched. In persons who are almost dead and have lost their muscular power, this organ often slips backward into the throat, and covers the glottis so that no air can pass in or out. It is necessary, in such cases, for some person to take hold of the tip of the tongue with a towel to prevent its slipping from the grasp, and draw it forward so as to leave the pas- sage to the lungs clear.* As soon as the person begins to breathe he can swallow, and a tablespoonful of brandy should be given him in a quarter of a tumblerful of water, * In all cases of asphyxia, pure air is of the utmost importance. The sufferer should therefore be in a well-aired room, and whether in- doors or out should never be surrounded by a crowd of people, whose respiration will pollute the air before it reaches the one who needs it most. 124 ORGANS OF REPAIR. dry clothing should be placed upon him, and he should be put in a warm bed until his recovery is complete. The above directions apply to all cases of suffo- cation, where there is no other injury to complicate the results of the mere deprivation of air. CHAPTER VIII. THE HEART. 160. General Plan of the Circulation. — The cir- culation of the blood is brought about by a compli- ten