Signs of Consumption. The signs that ought to make us suspicious of a possible beginning of tuberculosis are first, loss of weight without apparent cause; fever, or flushing of the cheeks, with or without headache, every afternoon or evening; and a tendency to become easily tired and exhausted without unusual exertion. Whenever these three signs are present, without some clear cause, such as a cold, or unusual overwork or strain, especially if they be accompanied by a rapid pulse and a tendency to get out of breath readily in running upstairs, they should make us suspect tuberculosis; and if they keep up, it is advisable to go at once and have the lungs thoroughly examined. Nine cases out of ten, seen at this stage, are curable—many of them in a few months.

Even if we should not have the disease, if we have these symptoms we need to have our health improved; and a course of life in the open air, good feeding, and rest, which would cure us if we had tuberculosis, will build us up and prevent us from developing it.



PNEUMONIA

Its Cause and Prevention. The other great disease of the lungs is pneumonia, formerly known as inflammation of the lungs. This is rapid and sudden, instead of slow and chronic like tuberculosis, but kills almost as many people; and unfortunately, unlike tuberculosis, is not decreasing. In fact in some of our large cities, it is rapidly increasing. Although we know it is due to a germ, we don't yet know exactly how that germ is conveyed from one victim to another. One thing, however, of great practical importance we do know, and that is that pneumonia is a disease of overcrowding and foul air, like tuberculosis; that it occurs most frequently at that time of the year—late winter and early spring—when people have been longest crowded together in houses and tenements; and that it falls most severely upon those who are weakened by overcrowding, under-feeding, or the excessive use of alcohol. How strikingly this is true may be seen from the fact that, while the death-rate of the disease among the rich and those in comfortable circumstances, who are well-fed and live in good houses, is only about five per cent,—that is, one in twenty,—among the poor, especially in the crowded districts of our large cities, the death-rate rises to twenty per cent, or one in five; while among the tramp and roustabout classes, who have used alcohol freely, and among chronic alcoholics, it reaches forty per cent. The same steps should be taken to prevent its spread as in tuberculosis—destroying the sputum, keeping the patient by himself, and thoroughly ventilating and airing all rooms. As the disease runs a very rapid course, usually lasting only from one to three weeks, this is a comparatively easy thing to do.

Though pneumonia is commonly believed to be due to exposure to cold or wet, like colds, it has very little to do with these. You will not catch pneumonia after breaking through the ice or getting lost in the snow, unless you already have the germs of the disease in your mouth and throat, and your constitution has already been run down by bad air, under-feeding, overwork, or dissipation. Arctic explorers, for instance, never catch pneumonia in the Frozen North.



CHAPTER XV

THE SKIN

OUR WONDERFUL COAT

What the Skin Is. The skin is the most wonderful and one of the most important structures in the body. We are prone to think lightly of it because it lies on the surface, and to speak of it as a mere coating, or covering—a sort of body husk; but it is very much more than this. Not only is it waterproof against wet, a fur overcoat against cold, and a water jacket against heat, all in one, but it is also a very important member of the "look-out department," being the principal organ of one of our senses, that of touch.

The eyes in the beginning were simply little colored patches of the skin, sunk into the head for the purpose of specializing on the light-rays. The smelling areas of the nose also were pieces of the skin, as were also the ears. Not only so, but—although it is a little hard for you to understand how this could have happened—the whole brain and nervous system is made up of folds of the skin tucked in from the surface of the back; so that we can say that the skin, with the organs that belong to it and have grown from it—the eyes, nose, ears, brain, and nerves—forms the most wonderful part of the body. Everything that we know of the world outside of us is told us by the skin and the look-out organs that have grown out of it. The skin is not only the surface part and coating of the body, far superior to any six different kinds of clothing which have yet been invented, but it is related to, and assists in, the work of nearly half the organs in the body. Not only all that we learn by touch and pressure, but everything that we know of heat and cold, of moisture and dryness, and most of pain, comes to us through our skin, through the little bulbs on the ends of the nerve twigs in it. It also helps the lungs to breathe, the kidneys to purify the blood, and the heart to control the flow of blood through the body.

A healthy skin is of very great importance; and part of this health we can secure directly, by washing and bathing, scrubbing and kneading and rubbing, because the skin lies right on the surface, where we can readily get at it. But, on the other hand, no amount of attention from the outside alone will keep it healthy. All the organs inside the body must be kept healthy if the skin is to be kept in good condition. Although the external washing and cleaning are very important, the greater part of the work of developing a healthy skin and a good complexion must be done from the inside.

The Two Layers which Make Up the Skin. Like our "internal skin," the mucous membrane, which lines our stomach and bowels, the skin is made up of two layers—a deeper, or basement, sheet, woven out of tough strands of fibrous stuff (derma); and a surface layer (epidermis) composed of cells lying side by side like the bricks in a pavement, or the tiles on a floor, and hence called "pavement" (epithelial) cells. These pavement cells are fastened on the basement membrane much as the kernels of corn grow on a cob; only, instead of there being but one layer, as on a cob of corn, there are a dozen or fifteen of them, one above the other, each one dovetailing into the row below it, as the corn kernels do into the surface of the cob. As they grow up toward the surface from the bottom, they become flatter and flatter, and drier, until the outer surface layer becomes thin, fine, dry, slightly greasy scales, like fish-scales, of about the thickness of the very finest and driest bran.

We are continually Shedding our Skin. One way in which the skin keeps itself so wonderfully clean and fresh is by continually shedding from its surface showers of these fine, dry, scaly cells, which drop, or are rubbed off, as they dry. This is the reason why no mark, not even a stain or dye, upon the skin, will stay there long; for no matter how deeply it may have soaked into the layers of the pavement-cells, every cell touched by it will ultimately grow up to the surface, dry up, and fall off, carrying the stain with it.

If you want to make a mark on the skin that will be permanent, you have to prick the colors into it so deeply that they will go through the basement layer and reach cells which will not grow toward the surface. This "pricking-in" operation is known as tattooing; and it is as foolish as it is painful, for blood-poisoning and other diseases may be carried into the system in the process.



Perhaps you will wonder why, if you are shedding these scales from all over your surface every day, you don't see them. This is simply because they are so exceedingly small, thin, and delicate, that you cannot see them unless you get a large number of them together; and when you are changing your clothing, bathing, etc., they are rubbed off and float away. If a part of the body has been shut in—as when a broken arm, for instance, is in a cast, which cannot be changed for several weeks—when finally you take off the bandage, you will find inside it spoonfuls—I had almost said handfuls—of fine scales, which have been shed from the skin and held in by the wrappings.

THE GLANDS IN THE SKIN

Sweat Glands. Like all the pavement (epithelial) surfaces of the body, inside and out, the skin has the power of making glands by dipping down little pouches or pockets into the layers below. In the skin, these little gland-pockets are of two kinds, the sweat glands and the hair glands.

The sweat glands are tiny tubes which go twisting down through the different pavement layers, through the basement layer, and right into the coat of fat, which lies just under the skin. The tube of the sweat gland soaks, or picks, out of the blood some of the waste-stuff—just as the kidney tube does in the kidney,—together with a good deal of water and a small amount of delicate oil, and pours them out on the surface of the body in the form of the "sweat," or perspiration.

As you will remember, when the muscles work hard and pour more waste into the blood, then the heart pumps larger amounts of blood out into the skin; and this causes it to redden. The sweat glands work harder to purify this extra blood, and they pour out the waste and oil and water on the surface. As soon as this water gets upon our hot skin, it begins to evaporate and cool us off, as well as to carry off some of the waste in the form of gas. The trace of oil in the perspiration helps to lubricate the skin and keep it soft; but when too much of it is poured out we have that greasy feeling, which we have all felt after perspiring freely.

From all this cooling and breathing and blood-purifying work going on upon the surface of our skin, you can easily see why it is so important that all our clothing should be loose and porous and that next the skin easily washed; else it will very soon become clogged up and greasy, and shut off the breathing and blood-purifying work of the skin and make it dirty and unhealthy. This continual mist of water, rising and bubbling up through our skin like springs out of a hillside, is another of nature's wonderful ways of cleansing the skin and of preventing any kind of dirt from permanently sticking to or lodging in it. Remember, you do not need to dig below the surface when you wash.

Hair Glands. The other kind of skin glands, the hair glands, are also pouches growing out from the deepest part of the stem of the hair, known as the root, or hair bulb.



From the root of the hairs, two or three little bundles of muscle run up toward the surface of the skin. When these contract, they pull the root of the hair up toward the surface, causing the hair to stand erect, or "bristle," as we say. This is what makes the hair on a dog's or a cat's back stand up when he is angry; but the commonest use of the movement is, when animals are cold, to make their coats stand out so as to hold more air and retain the body-heat better. We have lost most of our hairy coating, but whenever we get chilly, whether from cold or from fright, these little muscles of our hair bulbs contract and pull the hair glands of our skin up toward the surface, so that it looks all "pimply" or "goose-skinned."

Each hair pouch has sprouted out from its sides a pair of tiny pouches, which form oil glands to lubricate the hair and keep it sleek and flexible. It is hard to beat nature at her own game, and her method of oiling the hair is far superior to any hair oil that can be put on from the outside. Keep your hair well brushed and washed, and nature will oil it for you much better than any hair oil or scalp reviver ever invented.[19]

THE NAILS

How the Nails are Made. Another "trade," which our wonderful skin has literally "at its fingers' ends," is that of making nails. Indeed, every kind of scale, armor, fur, feather, and leather coating possessed by bird, beast, or fish was made by, and out of, the skin. Nail-making, however, is one of its simplest feats, as it is carried out merely by turning a little patch, or area, of itself into a horn-like substance. This, the skin of insects, of fishes, of crocodiles, etc., does all over the surface of their bodies; but in animals and birds only a number of little patches at the tips of the toes harden up in this way, to form the claws or nails; and in birds, the beak; and in some animals, the horns. So it is quite correct to call the substance of our nails "horn-like."

In some animals and birds, these little horny patches at the ends of the toes grow out into long, curved hooks, or broad, digging chisels and scoops; but on our own fingers, they simply make a little mould over the finger-tip. If, however, they are protected from being broken off, they will grow four or five inches long; in fact, they are carefully trained to do this by some of the upper classes in China, merely for the purpose of showing that they have never been obliged to degrade themselves, as they foolishly regard it, by working with their hands.

You can easily prove that the nails do grow constantly from the root or base, out toward the tip, by watching, some time when you have pounded one of your nails, how the black or discolored patch in it will grow steadily outward toward the tip, where it will be broken off and shed.

You cannot see the softest and youngest row, or layer, of the nail cells at the base, because a fold of skin, the nail fold, has been doubled, or folded, over them to protect them while they are young and soft. It is not best to push this fold of skin back too much, as, by so doing, you may uncover the young nail cells while they are soft and tender, and expose them to injury. The reason why there is a little whitish crescent at the base of the nail is that the cells of the nail do not grow hard and horn-like and transparent until they have grown out a quarter of an inch or so from under the fold, but at first look whitish, or opaque, like the rest of the skin.

Health Shown by the Color of the Nails. Your nails and your lips are not really any redder, or pinker, than the rest of your skin; but the cells forming them are clear and transparent and allow the red blood to show through. This is why we often look at the nails and lips to see what the color of the blood is like, and how well or badly it is circulating. If the blood is anemic, or thin, then both lips and nails are pale and dull. If the blood is healthy and the circulation good, then the nails are pink, and the lips clear red. If, on the other hand, the circulation is bad, as in some forms of lung disease and heart disease, so that the blood is loaded with carbonic acid until it is blue and dark, then the lips may become purplish or dark blue, and the finger nails nearly the same color.

THE BLOOD-MESH OF THE SKIN

The Blood Vessels under the Skin. Not merely the nails and the lips, but the whole surface of the skin is underlaid with a thick mat, or network, of blood vessels. These vessels are all quite small, so that a cut has to go down completely through the skin, and generally well down into the muscles, before it will reach any blood vessel which will bleed at a dangerous rate. But there are so many of them, and they cover such a wide surface throughout the body, that they are actually capable of holding, at one time, nearly one-tenth of all the blood in the body.

This "water-jacket" coat of tiny blood vessels all over our body has some very important uses: It allows the heart to pump large amounts of blood out to the surface to be purified by the sweat glands, and to breathe out a little of its carbon dioxid and other gas-poisons.

The Skin as a Heat Regulator. Heat, as well as waste, is given off by the blood when it is poured out to the surface; so another most important use of the skin is as a heat regulator. As we have already seen, every movement which we make with our muscles, whether of arms and limbs, heart, or food tube, causes heat to be given off. We very well know, when we work hard at anything, we are likely to "get warmed up." Although a certain amount of this heat is necessary to our bodily health, too much of it is very dangerous.

Just as it is best for the temperature, or heat, of a room to be at about a certain level, somewhere from 60 deg. to 70 deg. F., so it is best for the interior of our bodies to be kept at about a certain heat. This, as we can show by putting a little glass thermometer under the tongue, or in the armpit, and holding it there for a few minutes, is a little over 98 deg. F. (98.4 deg. to be exact); and this we call "body heat," or "blood heat," or "normal temperature." Our body cells are, in one way, a very delicate and sensitive sort of hot-house plants, though tough enough in other respects. Whenever our body heat goes down more than five or six degrees, or up more than two or three degrees, then trouble at once begins. If our temperature goes down, as from cold or starvation, we begin to be drowsy and weak, and finally die. If, on the other hand, our temperature climbs up two, three, or four degrees, then we begin to be dizzy and suffer from headache and say we have "a fever."

A fever, or rise of temperature, that can be noted with a thermometer, is usually due to disease germs of some sort in the body; and most of the discomfort that we suffer is really due more to the poisons (toxins) of the germs than to the mere increase of heat, though this alone will finally work serious damage. However, as we well know from repeated experience, we need only to run or work hard in the sun for a comparatively short time to make ourselves quite hot enough to be very uncomfortable; and if we had no way to relieve ourselves by getting rid of some of this heat, we should either have to stop work at once, or become seriously ill. This relief, however, is just what nature has provided for in this thick coat of blood vessels in our skin; it enables us to throw great quantities of blood out to the surface where it can get rid of, or, as the scientists say, "radiate," its heat. This cooling process is hastened by the evaporation of the perspiration poured out at the same time, as we have seen.

One of the chief things in training for athletics is teaching our skin and heart together to get rid of the heat made by our muscles, as fast, or nearly as fast, as we make it, thus enabling us to keep on running, or working, without discomfort. As soon as we stop running, or working, the heart begins to slow down, the blood vessels in the skin contract and diminish in size, the flush fades, and we begin to cool off. We are not making either as much heat or as much waste as we were, and hence do not need to get rid of so much through our skins.

When we feel cold, just the opposite kinds of change occur in the skin. The blood vessels in the skin contract so as to keep as much of our warm blood as possible in the deeper parts of our body, and prevent its losing heat. As blood showing through the pavement-layer of the skin is what gives us our color, or complexion, our skin becomes pale and pasty-looking; and if all the blood is driven in from the surface, our lips and finger nails will become blue with cold. Here again, by changes in the skin, nature is simply trying to protect herself from the loss of too much heat.

If we exercise briskly, or eat a good warm meal, and thus make more heat inside of our body, then there is no longer any need to save its surface loss in this way; and the blood vessels in our skin fill up, the heart pumps harder, and the warm, rich color comes back to our faces and lips and finger nails.

So perfectly and wonderfully does this skin mesh of ours work, by increasing or preventing the loss of heat, that it is almost impossible to put a healthy man under conditions that will raise or lower his temperature more than about a degree, that is to say, about one per cent above, or below, its healthful level. Men studying this power of the skin have shut themselves into chambers, or little rooms, built like ovens, with a fire in the wall or under the floor, and found that if they had plenty of water to drink and perspired freely, they could stand a temperature of over 150 deg. F. without great discomfort and without raising the temperature of their own bodies more than about one degree. If, however, the air in the chamber was moistened with the vapor of water, or steam, so that the perspiration could no longer evaporate freely from the surface of their bodies, then they could not stand a temperature much above 108 deg. or 110 deg. without discomfort.

Other men, who were trained athletes, have been put to work in a closed chamber, at very vigorous muscular exercise, so as to make them perspire freely. But while a thermometer placed in that chamber showed that the men were giving off enormous amounts of heat to the air around them, another thermometer placed under their tongues showed that they were raising the temperature of their own bodies only about half a degree. One man, however, happened to try this test one morning when he was not feeling very well, and didn't perspire properly, and the thermometer under his tongue went up nearly four degrees.

THE NERVES IN THE SKIN

How We Tell Things from Touch, and Feel Heat and Cold and Pain. Last of all, the skin is the principal organ of the sense of touch, and also of the "temperature sense"—the sense of heat and cold—and of the sense that feels pain. All these feelings are attended to by little bulbs lying in the deeper part of the skin and forming the tips of tiny nerve twigs,[20] which run inward to join larger nerve branches and finally reach the spinal cord. There are millions of these little bulbs scattered all over the surface of the skin, but they are very much thicker and more numerous in some parts than in others; and that is why, as you have often noticed, certain parts of the skin are more sensitive than others. They are thickest, for instance, on the tips of our fingers and on our lips, and fewest over the back of the neck and shoulders, and across the lower part of the hips.[21]

For a long time, it was supposed that all these little nerve-bulbs in the skin did the same kind of work, because they looked, under the microscope, exactly alike; but it was found that they divide the work up among them, so that some of them give their entire attention to heat, and others to cold, others to touch, and others again to pain. So carefully has the work been mapped out among them that they report to different centres in the brain and spinal cord, so that we now understand why, in diseases which happen to attack one or other of these centres, we may lose our sense of heat and cold, as in that terrible disease, leprosy; or our sense of touch, as in paralysis; or we may even, in some very rare cases, lose our sense of pain, and yet have all our other senses perfect.

FOOTNOTES:

[19] Hairs are of value chiefly as protection against cold and wet, although we have got rid of them and substituted clothing for this purpose, except on the top of our heads; but their roots also are very richly supplied with nerves so that they form almost a sort of feelers, or organs of sense. Many animals that move about much in the dark, like cats and bats, for instance, have their lips or faces studded with long, delicate, stiff hairs called whiskers, which act in this way and prevent their bumping into objects in the dark. And it is probable that the bristling of the hair on a dog's back, when he is angry or frightened, is in part for this purpose—to enable him to slip aside and dodge a blow, even after it has touched the ends of the hairs. This great sensitiveness of the hair roots is what makes it hurt so when any one pulls your hair.

[20] See the diagram of the skin on page 171.

[21] You can easily test this by a very simple experiment. Take a pair of dividers; or, if you haven't these, a couple of long pins or needles will do. Set them with their points a quarter of an inch apart. Then touch these points, first closing your eyes, so that you will not be able to see them, to the tip of one of your fingers, and you will readily feel that two points touch the skin. Turn your hand over and touch the back of it with the two points, and they will feel like one point. Carry the test further, over other parts of the body, and you will find that they are much less sensitive; thus you will find that at the back of the neck, or over the shoulder-blades, you will have to put the points nearly an inch apart before you can tell that there are two of them. This simply means that you have to touch two separate touch bulbs before you can get the idea of "two-ness." As these bulbs are an inch or more apart in the skin of the back, you have to spread the points of the dividers that distance. You can also prove that the touching of two nerve-buds gives the idea of "two-ness" by crossing two of your fingers and placing a pea, or small round piece of chalk, between their crossed tips. If you close your eyes and roll the pea on the table, or desk, you will think you have two peas between your fingers.



CHAPTER XVI

HOW TO KEEP THE SKIN HEALTHY

CLOTHING

Clothes should be Loose and Comfortable. Man is the only animal that has no natural suit of clothing. Birds have feathers, and animals have fur, or hair, which they shed in summer and thicken up in winter without even thinking about it, so that they do not have to bother with either overcoats or flannels. The wise men say that man originally had a full suit of hair like other animals, and that he gradually got rid of it, as he became human. Whether this be true or not, the fact remains that he has none now; and consequently he must invent and manufacture something to take its place.

Originally, in the time of our savage ancestors, clothing was worn chiefly as protection from cold at night, so that all the earlier forms of clothing were of a more or less blanket-or cloak-like form, and wrapped, or swathed, the whole body without fitting closely to the limbs. It is interesting to remember this fact, because even our most highly civilized forms of clothing still show this same tendency. The skirt, for instance, is simply a survival of the lower end of the blanket, which has never been cut down to fit the limbs.

The principles upon which garments should be built are two: First, they should fit closely enough to the body and limbs to protect them from either injury or cold, even while free activity of every sort is allowed—you could not wrestle in a blanket or run very far in a sack. Second, they should be thick enough to protect us from cold, and yet at the same time porous enough not to interfere with the natural breathing and ventilating of the skin. A garment should be as loose as possible without interfering with our movements, and as free and as light as can be worn with reasonable warmth and protection. The less clothing you can wear and be comfortable, the better.

We should particularly avoid binding or cramping the chest and the hips and waist. If clothing is too tight about the chest, it interferes both with free movement of the arms and, what is even more important, with the breathing movements of the chest. If too tight about the waist and hips, it badly cripples the lower limbs and interferes with the proper movements of the diaphragm in breathing, and with the passage of the food and the blood through the bowels.

Your instincts are perfectly right that make you dislike to be squeezed or pinched or cramped in any way, or at any point, by your clothing; and if you will only follow these instincts all through your lives, you will be far healthier and happier.

The Texture of Clothing. Just as for ages we have experimented with different kinds of food, so we have with different kinds of material for clothing. We have used the skins of animals; mats woven out of leaves and grasses; the feathers of birds; the skins of fishes; cloths made of wool and of cotton; and even the cocoon spun by certain caterpillars, which we call silk. But of all these materials, practically only two have stood the test of the ages and proved themselves the most suitable and best all-round clothing materials—wool and cotton.

Woolen cloth, woven from the fleece of sheep or goats or camels or llamas or alpacas, has three great advantages, which make it the outside clothing of the human species. First, it is sufficiently tough and lasting to withstand rips and tugs and ordinary wear and tear; second, it is warm—that is, it retains well the body heat; and third, it is porous, so that it will allow gases and perspiration from the surface of the body to pass through it in one direction, and air for the skin to breathe, in the other.



No clothing, of course,—not even fur,—has any warmth in itself; it simply has the power of retaining, or keeping in, the warmth of the body that it covers. The best and most effective way of retaining the body warmth is to surround the body with a layer of dead, or still, air, which is the best non-conductor of heat known. Hence, porous garments, like loosely-woven flannels, blankets, and other woolen cloths, are warm because they contain or hold large amounts of air in their spongy mesh.

The reason why furs are so warm is that their soft, furry under-hairs, or "pelt" as the furriers call it, entangle and hold an enormous amount of air. The fur of ordinary sealskin, for instance, is about half an inch deep; and ninety per cent of this half-inch is air. If you wet it, its fur "slicks down" to almost nothing, although the most drenching wetting will not wash all the air out of it, but still leaves a dry layer next to the skin. The fur of mink skin, coon skin, or wolf skin, is an inch thick; and nearly eighty per cent of this thickness is air.

The great advantage for clothing purposes of wool over fur is that the wool is porous through and through, while the fur is borne upon, and backed by, a layer of leather—the skin of the animal upon which it grew—which layer, after tanning and curing, becomes almost absolutely air-tight.

As a matter of fact, furs are worn mostly for display and are most unwholesome and undesirable garments. The only real excuse for their use, save for ornament in small pieces or narrow strips, is on long, cold rides in the winter, and among lumbermen, frontiersmen, and explorers. They hold in every particle of perspiration and poisonous gas thrown off by the skin, and if worn constantly, make it pale, weak, and flabby; and the moment we take them off, we take cold.

For outer garments and general wear, nothing yet has been discovered equal to wool, particularly at the cooler times of the year. But for under wear, in the hotter seasons and climates, wool has certain disadvantages. It is likely to be rough and tickling to most skins, which makes it uncomfortable, especially in warm weather. It is also difficult and troublesome to wash woolens without shrinking them; and, as soon as they do shrink, not only do they become uncomfortably tight, but the natural pores in them which make them so valuable close up, and they become almost air-tight. Finally, when loaded with perspiration, woolens easily become offensive, so that they must be frequently changed and washed; and as they are also high in price, it is easily seen that there are practical drawbacks to their use.

Cotton is much softer and pleasanter to the skin than wool, is cooler in hot weather, is much cheaper, and is very easily washed without losing either its shape or its porousness. It can be so woven as to be almost as porous as wool, and to retain that porousness even when saturated with perspiration. It does not soak up and retain the oils and odors of perspiration in the way that wool does; and on the whole, for under wear, and for general wear at the warm seasons of the year, it is not only more comfortable, but far more healthful, than wool. Persons of fair health and reasonably vigorous outdoor habits, whose skins are well bathed and ventilated, can wear properly woven cotton or linen undergarments the whole year round with perfect safety.



Linen and silk both make admirable and healthful under wear, if woven with a properly porous mesh. Linen has the advantage of remaining more porous than cotton, when moist with perspiration. But for healthy people they have no advantages over cotton that are not offset by their higher prices.

BATHS AND BATHING

Bathing as a Means of Cleanliness. It has been said that one of the reasons why man lost his hairy coat was that he might be able to wash himself better and keep cleaner. However this may be, he has to wash a great deal oftener than other animals, most of whom get along very well with currying, licking, and other forms of dry washes, and an occasional swim in a river or lake.

You can readily see how necessary for us washing is, when you remember the quarts of watery perspiration, which are poured out upon our skins every day, and the oily and other waste matters, some of them poisons, which the perspiration leaves upon our skins. Especially is some means of washing necessary when the free evaporation of perspiration and the free breathing of the skin has been interfered with by clothing which is water-tight or too thick.

Bathing as a Tonic. But bathing is of much greater value than simply as a means of cleansing. Splashing the body with water is the most valuable means that we have of toning up and hardening the skin, and protecting us against the effects of cold. The huge and wonderfully elaborate network of blood vessels that lies in and just under our skins all over our bodies is, from the point of view of circulation, second only in importance to our hearts, and from the point of view of taking cold, and of resisting the attack of disease, one of the most important structures in our entire body. If, by means of daily baths, you keep this mesh of blood vessels in your skin toned up, vigorous, and elastic, and full of red blood, it will do more to keep you in perfect health and vigor than almost any other one thing, except an abundance of food, and plenty of fresh air and exercise. A healthy skin is the best undergarment ever invented.

Right and Wrong Bathing. The best form of bath is either the tub or the shower bath; and the cooler the water, provided that you warm up to it quickly and pleasantly, the greater the tonic effect, the more exhilaration and pleasure you will get out of it, and the more it will harden your skin against cold. But it should never under any circumstances be any cooler than you can readily and pleasantly react, or warm up to, during the bath and afterward. The habit of plunging into a great tub of ice-cold water all winter long, except for people of vigorous constitutions and active habits, may often do quite as much harm as good. Have your bath water just cool enough to give you a slight, pleasant shock, as you plunge into it, or turn it on, so that you will enjoy the glow and sense of exhilaration that follows; and you will get all the good there is out of the cold bath, and none of the harm. By beginning with moderately cool water you will find that you come to enjoy it cooler and cooler. If a bath-room is not at hand, a large wash-bowl of cool, or cold, water into which you can dip your hands and splash well over the upper half of your body every morning, and once or twice a week all over your body, will keep your skin clean and vigorous. If you cannot warm up properly after a cool bath, there is something wrong about your habits of life; and you had better change them, and keep changing them, until you find you can enjoy it. For some delicate children, a quick plunge into, or splash with, very hot water in the morning will give somewhat the same tonic effect as stronger ones can get from cold water.



Warm baths are best taken at night, just before going to bed, though the danger of catching cold after them on account of their "opening up the pores of the skin," has been very greatly exaggerated. They have, however, a relaxing effect upon the skin, and take out an undue amount of the natural oil which nature provides for its oiling and softening, so that, except for special reasons, it is best not to take them oftener than once, or twice, a week.

Soaps and Scrubbing Brushes. As part of the perspiration deposited upon our skins is in the form of a delicate oil, and as this oil may become mixed with dirt, or dust, and form a mixture not readily soluble in water, it is at times advisable to add to the water something that will dissolve oil. The commonest thing used for this purpose is soap, which is a combination of an alkali—most commonly soda, though occasionally potash (lye) is used in the soft soaps—with a fat or an oil. The combination of the two, which we call soap, has been invented for two reasons; one, that it makes a convenient, solid form in which the alkali, needed to dissolve the body oil, can be used in such strength as not to burn or injure the skin; the other, that the fat in the soap will, to some extent, take the place of the natural oil, or fat, which it washes off.

Necessary as soap is, it should be used very moderately. You should never lather and scrub your skin as if it were a kitchen floor, for the reason that, with the dirt, the alkali also washes and dissolves out a considerable amount of the natural oil of the skin, and leaves it harsh and dry. On this account, it is best not to use soap upon the covered portions of the body, and in the full bath, oftener than once or twice a week; and upon the face, oftener than once or twice a day. But the hands may be washed with soap more frequently.

It is also best to avoid the too frequent use of hot water, even upon the hands and face, for the same reason; it takes out too much of the natural oil of the skin, along with the dirt. Unless the dirt be of some infectious, or offensive, character, it is often best to content yourself with washing off just the "big dirt," and wait for the bubbling up of the perspiration through your skin to bring the deeper dirt up to the surface, and wash that off later, in the course of two or three hours.

Soaps to be Avoided. Soaps that lather too quickly and easily should always be avoided, for this shows that they contain an excessive amount of soda or other alkali. It is also best to avoid, or at least be very wary of, any soaps which are dark-colored or heavily perfumed, as these disguises may indicate the presence of decaying, offensive fats, and even of grease extracted from garbage. This is what strong perfumes in soaps are chiefly used for. Beware of all such, and especially of tar soaps, for the black color and the strong odor of tar can cover up any amount of bad quality.

Medicated soaps (soaps containing medicines) are also best let alone. They are only fit to be used on the advice of a doctor. Most of them are out and out humbugs, and make up for their richness in drugs by their poorness in good, pure fat and alkali. Moreover, what may suit one particular diseased condition of the skin is quite as likely to be injurious as helpful to another. Any drug which has the power of curing disease is almost certain to be irritating to a healthy skin; and nothing can be put into a soap beyond pure, sweet fat, or oil, and good soda, which will make it any better, or more wholesome, for a healthy skin. If your skin be red, or itchy, or scaly, or out of condition in any way, go to a doctor and get the appropriate treatment for that particular disease, instead of smearing on the surface of your body some drug of which you know nothing, in the hope of its being the proper thing for the little patch of diseased skin.

Avoid Using Skin Brushes. Scrubbing brushes and skin brushes of all sorts should be used even more sparingly than soap or hot water, for the same reason. Nature did not coat us over with either boards or rubber, but with delicate, velvety, sensitive, living skin worth ten times as much as any sort of leather, bark, rubber, or cloth, for resisting cold, heat, and injuries. It is most important for the health of the skin that we keep that velvety coating unscratched and unbroken. The use of brushes and bristles of all sorts, therefore, should be chiefly restricted to the hair and the finger nails, as for every ounce of dirt that they take out of the skin, they do a pound of damage to it. They scrub off the delicate epidermis, as well as the natural oil in it, and leave it dry and irritated and ready to crack open. Then more dirt gets into the cracks just formed, and more scrubbing with bristles and hot water and soap is indulged in to get it out. This opens the cracks still further, and the next layer of dirt is worked in still deeper. Wash frequently with cold or cool water, occasionally with hot water, and sparingly with soap; and limit the use of brushes to the nails and the hair.

CARE OF THE NAILS

Importance of Clean Nails. On account of their constant use, your hands are brought in contact with dusty or dirty substances in your work and in your play; and it is very easy for some of this dirt, and such germs as it may contain, to lodge in the little chink under the free edge of the nail, between it and the rounded end of the finger. It is of great importance that this nail chink should be kept clean, not only because it looks both ugly and untidy to have the ends of your fingers "in mourning," with black bands across them, but also because the germs lodged under your nails may get onto your food the next time that you eat, and set up irritation and fermentation in your stomach. They may also cause other trouble; for instance, if your collar chafes the back of your neck, and to relieve the itching you rub it a little too hard with your finger, your nail may scratch the skin; and if it be blackened with infectious dirt, this may get into the little scratch and give rise to a boil, or a festering sore.

How to Clean the Nails. This cleaning of the nails, however, must be done carefully and gently; for, if too harsh methods are used, the delicate skin on the under surface of the nail will be torn, the nail will be roughened or split, the dirt will work in just that much deeper next time, and the germs in it may set up inflammations under the nail. For this reason it is best not to use a sharp-pointed knife in cleaning the nails, but a blunt-pointed nail cleaner, such as can be bought for a few cents at any drug store, or such as many pocket-knives are now provided with. It is also best to trim the nails with a file or with scissors, instead of a knife, as the latter may split or tear the nail, or cut down to the quick. Before any of these are used, the nails should be thoroughly softened in warm water, and scrubbed with a moderately stiff nailbrush, such as should be kept on every washstand.

It is also best not to push back the fold of skin at the base of the nails, with instruments of any sort; or indeed, with anything harder than the ball of the thumb or finger. This fold protects the delicate growing part, or root, of the nail; and if it is shoved back too vigorously, the root may become exposed, or even inflamed and infected, and cause one of those extremely irritating little sores known as a "hangnail."

DISEASES AND DISTURBANCES OF THE SKIN

Their Chief Causes. Skin troubles are of two main kinds according to their cause: internal, due to the irritation of waste-poisons, or toxins, in the blood; and external, from direct injury or irritation of the skin from without.

The latter are often due to the wearing of too tight or too heavy clothing, or the failure properly to wash, cleanse, and ventilate the skin. Some of the lesser disturbances come from the chafing of collars, wristlets, and belts, and are, of course, relieved by loosening the clothing or substituting soft, comfortable cotton for rasping flannels. Others come from the use of too strong soaps, or the too frequent use of hot water, or too vigorous scrubbing of the skin, and these can be relieved by the avoidance of their cause.

Sunburn and Freckles and how to Cure Them. Upon the hands and face, sunburn and freckles may occur from exposure to the weather. They are not caused necessarily by exposure to direct sunlight; as the bright light and the cold air out of doors, also, will produce this irritating effect upon the skin.

The best way to cure sunburn is to bathe in cool water, take a night's rest, then go out the next day, and the day after, and take another dose of exposure, keeping this up until your face is hardened to stand a reasonable amount of sun. If you are in proper condition, neither your face nor your hands will sunburn uncomfortably. If they do, except under extreme exposure, it is a sign that you have not been living out of doors enough.

The various face-washes and creams and dusting powders which are used for the relief of sunburn, while they may, if mild enough, make the face feel somewhat more comfortable for a little time, owe most of their virtues to the fact that they are generally used at bedtime and then get the credit for the cure which nature works while you are asleep. If you should buy them, and keep them on your dressing-table unopened, where you could see them before you went to bed, you would in nine cases out of ten be just as much better in the morning as if you had used them.

The only harm done by freckles is to your vanity. They and sunburn both, in fact, are protective actions on nature's part, filling the skin with coloring matter, or pigment, so as to protect it, and the tissues below, from the irritating effects of the strong rays of light.

A like deposit of pigment, in greater amounts, in the skins of races who live in or near the tropics, gives rise to the characteristic coloring of the black, brown, and yellow races. The pigment, or coloring matter, is of exactly the same kind in all, from the negro to the white. The brown race having a little less of it than the negro, the yellow race a little less yet, and the white least of all, though there is some of it in even the whitest of skins.

Real Skin Diseases. Most of the serious and lasting diseases of the skin are caused by the attack of germs. Perfect cleanliness and ventilation are the best protection against them all; but if you should be unfortunate enough to catch one of these diseases, your doctor will be able to give you the mild germicide or antiseptic that will kill the particular germ that may have lodged upon your skin.

The commonest form of inflammation of the skin is called eczema, and eight-tenths of all eczemas are due to some mild germ, and can be cured by the appropriate poison for it.

Other diseases, particularly of the scalp, such as ringworm and dandruff, are due to other forms of vegetable germs, and may be cured by their proper poisons; while others, such as the so-called "prairie itch" (scabies), and lice in the hair, are due to the presence of tiny animal parasites.

The Hookworm. Another disease which enters through the skin is the now famous hookworm, or blood-sucking parasite, which has been found to be so common in tropical regions and in our Southern States. This parasite has the curious habit of attaching itself by hooks surrounding its mouth (which gave it its name), to the lining of the human intestine, particularly its upper third. There it swings, and lives by sucking the blood of its victim. When the worm has once attached itself in the intestine, it may live for from five to fifteen years. All this time it is constantly laying eggs; and these eggs, which are so tiny that they have to be put under a microscope to be seen, pass out in the feces; and if they are not deposited in a proper water closet, or deep vault, but scattered about upon the surface of the soil, the eggs quickly hatch into tiny, little wriggling worms called larvae, which are still scarcely large enough to be seen with the naked eye.

These larvae live in the soil; and, when it is wet and muddy, they get up between the toes of boys and girls who are going barefoot, burrow their way in through the skin, and produce a severe itching inflammation of the skin of the feet, known as "ground-itch," "toe-itch" or "dew-itch." When they have worked their way through the skin, they bore on into a blood vessel, are carried to the heart, pumped by the heart into the lungs, and there again work their way out of the blood vessels into the bronchial, or air tubes, crawl up these through the windpipe and voice organ into the throat, are swallowed into the stomach, and from there pass on into the upper intestine to attach themselves for their blood-sucking life. If they are sufficiently numerous, their victim becomes thin, weak, and bloodless, with pale, puffy skin, and shortness of breath; he is easily tired on the least exertion, and ready to fall a victim to any disease, like tuberculosis, pneumonia, or typhoid, that may happen to attack him.

Their spread can be absolutely prevented either by the strict use of toilets or deep vaults, thus preventing the deposit of feces anywhere upon the surface of the ground; or by the constant wearing of shoes or sandals, thus preventing the larvae from attacking the feet and working their way through the skin and body into the intestine.

Fortunately, the disease is as curable as it is common, and two doses of a proper germicide, with a day in bed, and a laxative, will promptly cure it except in the worst cases.

The Rashes of Measles, Scarlet Fever, etc. Many of the infectious fevers, such as measles, scarlet fever, chicken-pox, and smallpox, are attended by rashes, or eruptions, upon the surface of the skin, due to a special gathering or accumulation of the particular germs causing each disease, just under the skin. When the skin sheds, or flakes off, after the illness, the germs are shed in the scales and float, or are carried about, and thus spread the disease to others.

These rashes or eruptions are not dangerous in themselves, though often very uncomfortable, but help us to recognize the disease; they probably show us the sort of thing that is going on in the deeper parts of the body. If you imagine that your throat and bronchial tubes and lungs are peppered as full of the disease spots as your skin is, in measles and in scarlet fever, you will readily understand why your throat is so sore and why you have so much tickling and coughing.

The Health of the Scalp and Hair. The scalp, being covered by hair, does not perspire so freely as the rest of the skin of the body; but a considerable amount of oily waste matter is poured out on it, and the surface of its skin scales off in exactly the same way as does the rest of the body. If this accumulation of tiny scales and grease is not properly brushed out, it forms an excellent seed-bed for some of the milder kinds of germs that attack the skin; and a scurfy, itchy condition of the scalp is set up, known as dandruff.

The best way to keep the scalp clean of these accumulations of greasy scales is by vigorous and regular brushing with a moderately stiff, but flexible, bristle brush. Wire brushes should not be used, as the wires scratch and irritate the delicate scalp and do more harm than good. If you watch a groom brushing and currying the coat of a thoroughbred horse, you will get a fair idea of hew you ought to treat your own scalp at least twice a day, night and morning.

If this currying of the hair be thoroughly done, and the head washed with soap and hot water about once a week for short hair and twice a month for long hair, most of the dangers of dandruff and of other infections of the scalp will be avoided. One thing to be remembered is, don't brush too hard or too deep. There is an old saying and a good one, "You can't brush the scalp too little, or the hair too much."

Wetting the hair for the purpose of "slicking" it or combing it, is about as bad a thing as could be done; for the moisture sets up a sort of rancid fermentation in the natural oil of the scalp, giving the well-known sour smell to hair that is combed instead of brushed, and furnishing a splendid soil for germs and bugs of all sorts to breed in. There is no objection to boys' and men's wetting their hair in cold water as often as they wish, provided that they rub it thoroughly dry afterward and give it a brisk currying with the brush.

Hair oils and greases of all sorts are sanitary nuisances, and mere half-civilized and lazy substitutes for proper brushing and washing. There is no drug known to medicine which will cause hair to grow, or make it thicker or curlier. All "hair tonics" claiming to do this are frauds.

Corns, Calluses, and Warts. Our skin not only made our hair, teeth, and nails, but still retains in every part a trace of its nail-making powers, so that under pressure or irritation, it can thicken up into a heavy leather-like substance which we call callus. This is naturally and healthfully present in the soles of the feet and the palms of the hands. Savage, or barbarous, races who wear no shoes get the skin of their soles thickened into a regular human leather, almost half an inch thick, and as tough as rawhide. A somewhat similar condition develops in the palms of the hands of those who work hard with spades, axes, or other tools.

Any good process carried to excess becomes bad, and this is true of this power of callus formation in the skin; for parts of it which are under constant pressure, like the surface of the toes inside the shoe, and particularly of the outside toes, the little and the big toe, develop under that pressure patches of thickened, horny skin, which we call corns. These patches start to grow into cone-shaped projections or buttons; but being prevented from growing outward by the pressure of the shoe, they turn upon themselves and burrow into the skin itself, and we get the well-known ingrowing corn.

If there is anything in the human body which we ought to be thoroughly ashamed of, it is corns; for they are caused by our own vanity, and nothing else, in cramping our feet into shoes one or two sizes too small for them. There are a number of things that can be done to relieve the discomfort of the corn, but the only sure way is to remove its cause, namely, the tight shoe.

Under other kinds of irritation, the skin has the power of growing curious little button-like buds, or projections, which we call warts. These are commonest in childhood, and generally disappear at about twelve or fifteen years of age, when we no longer delight in dirt, and glory in mud pies.

They can be produced upon the hands of grown men and women by irritating fluids and substances, such as wet sugar in the case of bakers and confectioners, and various color-stains in dye works. They seldom last for more than a few months, and usually narrow at their base and drop off, when the particular irritation that caused them ceases. On this account it is seldom worth while to try to remove them by burning with acids or cutting them off; and it is best not to pick at, or irritate, or scratch them too much.



CHAPTER XVII

THE PLUMBING AND SEWERING OF THE BODY

The Wastes of the Body. Almost everything that the body does in the process of living means the breaking down, or burning, of food; and produces, like every other kind of burning, two kinds of waste—"smoke" and "ashes."

The carbon dioxid "smoke," as we have already learned, is carried in the blood to the lungs, where it passes off in the breath. The solid part of our body waste, or the "ashes," is of two kinds—that which can be melted in water, or is, as we say, soluble; and that which cannot be melted in water, or is insoluble. The insoluble part of our solid body waste goes into the feces and is thus disposed of.

The soluble part of the body waste goes by a somewhat more roundabout route. With the carbon dioxid it is poured by the body cells into the veins, carried to the heart, and pumped through the lungs, where the carbon dioxid is thrown off. Going back to the heart it is pumped all over the body, part of it going through a very large artery to the liver, part through two large arteries to the kidneys, part to the skin, and the rest all over the remainder of the body.

The blood goes completely round the body-circuit from the heart to the fingers and toes, and back again to the heart, in less than forty-five seconds. Practically every drop of blood in the body will be pumped through the liver, the kidneys, and the skin, about once every half minute, so that they get plenty of chance to purify it thoroughly when they are working properly.

This sounds rather complicated; but is interesting, because it shows how much of a "mind of their own" the different organs and stuffs in our bodies have, or what, in scientific language, we call "power of selection." The skin glands pick out of the blood those waste substances which they are able to get rid of. The kidneys pick out another class of waste substances, which they are best able to deal with; while the liver which is the most important of all, attacks almost every kind of waste brought to it by the blood, and prepares it for disposal by the intestines, skin, and kidneys.

The Liver. The liver has a size to match its importance. It is the largest and heaviest gland, or organ, in the body, and weighs about three pounds, a little more than the brain. It buds off from the food tube just below the stomach, so that its waste tube, the bile duct—about the size of a goose quill—opens into the upper part of the intestine.

The main work of the liver is to receive the blood from all over the body and to act upon its waste substances, burning them up so that they can be taken up, and got rid of, by the glands of the skin and the kidneys. In the process it very frequently changes these waste substances from poisonous into harmless forms; and even when disease germs get into the body and infect it, the poisons, or toxins, which they pour into the blood are carried to the liver and there usually burned up, or turned into harmless substances.

The liver is, therefore, to be regarded as a great poison filter for the entire body. So long as it can deal with the poisons as fast as they are formed, either by the body itself, or in the food, or by disease germs, the body is safe and will remain healthy. But if the poisons come faster than the liver can deal with them, as, for instance, when we have eaten tainted meat or spoiled fruit, or have drunk alcohol, they begin to poison our nerves and muscles, and we become, as we say, "bilious." Our head aches, our tongue becomes coated, we have a bad taste in the mouth, we lose our appetite and feel stupid, dull, and feverish.

Such waste materials as the liver cannot burn down so that the kidneys and skin can handle them, it pours out through its duct into the intestine as the bile. The bile is a yellowish-brown fluid, which assists the pancreatic juice in the digestion of the food, and helps to dissolve the fats eaten, but is chiefly a waste product. It turns green when it has been acted upon by acids, or exposed to the air. So that the bile which you throw up when you are very sick at your stomach, is green because it has been acted upon by your gastric juice.

As you will remember, the blood which comes from the stomach and bowels is carried by the portal vein to the liver first and, through that, to the heart, instead of going directly to the heart, as all the other impure blood in the body does. This is owing, in part, to the fact that this blood, being full of substances freshly taken or made from the food, is very likely to contain poisons; indeed, as a matter of fact, blood taken from these veins on its way to the liver, and injected directly into the blood vessels of an animal, acts like a mild poison.

In part, however, this blood goes first to the liver, because the liver, besides being a great blood purifier, is a "blood-maker" in the sense that it changes raw food-stuffs in the blood from the intestines into forms which are more suitable for use by the brain, the muscles, and the other tissues of the body. Some of the sugars, for instance, the liver turns into a kind of animal starch (glycogen), which it stores away in its own cells. It also turns both sugars and proteins in the portal blood into fat, part of which it pours into the blood, and part of which it stores away also in its own cells. Thus the liver owes its great size partly to the large amount of blood-purifying, filtering, and poison-destroying work which it has to do, and partly to its acting as a storehouse of starch and fat, which the body can readily draw upon as it needs them.



As all poisons formed in, or entering, the body are brought to the liver for destruction, it is in an extremely exposed position, and very liable to break down under the attack of these poisons, whether of infectious diseases, or chloroform, or alcohol, or those formed by putrefaction in the stomach and intestines. This is why those who have lived long in the tropics and suffered from malaria, dysentery, and other infectious diseases, and those who drink too much alcohol, or have chronic indigestion, or dyspepsia, are likely to have swollen and inflamed livers.

The Gall Bladder. The liver has on its under side a little pear-shaped pouch called the gall bladder, in which the bile is stored before it is poured into the bowel. If this becomes inflamed by disease germs, or their poisons, in the blood, little hard masses will form inside it, usually about the size of a grain of corn, known as gall stones. So long as they stay in the gall bladder, they give little trouble, but if they start to pass out through the narrow bile duct into the intestine, they cause severe attacks of pain, known as "gall-stone colic," and, by blocking up the duct, may dam up the flow of the bile, force it back into the blood again, and stain all our tissues, including our skin and our eyes, yellow; and then we say we are jaundiced. Jaundice may also be caused by colds or other mild infections which attack the liver and bile ducts and clog the proper flow of the bile.

The Kidneys. The kidneys are another form of blood-filter, which deal chiefly with waste stuffs in the blood left from the proteins, or Meats, of our food—meat, fish, milk, cheese, bread, peas, beans, etc. These waste-stuffs, called urea and urates, are formed in the liver and brought in the blood to the kidneys. These lie on either side of the backbone, opposite the small of the back, their lower ends being level with the highest point of the hip-bones, nearly six inches higher than they are usually supposed to be. When you think you have a "pain across the kidneys," it is usually a pain in the muscles of the back much lower down, and has nothing to do with the kidneys at all.

A very large artery carries the blood from the aorta to each side of the kidney, and a large vein carries the purified blood back to the vena cava and heart. Two smaller tubes about the size of a crow quill, the waste pipes of the kidneys (the ureters), carry the water containing urea and other waste substances strained out by the kidneys and called urine, down into a large pouch, the bladder, to be stored there until it can be got rid of.



The kidneys then are big filter-glands. They, like the lungs, are made up of a mesh, or network, of thousands of tiny tubes of two kinds, one set of tubes being blood vessels, and the other set the tiny branches of the kidney tubes which finally run together to form the ureters. The urine filters through from the spongy mesh of blood tubes (capillaries) into the kidney tubes and is poured out through the ureters. It is very important that the urine should be discharged as fast as it fills the bladder, that is, about once every three hours during the day. Nothing should be allowed to interfere with this; and whenever nature tells you that the bladder is full, it should be emptied promptly, or the poisons which nature is trying to get rid of in the urine may get back into the blood and cause serious trouble.

Diseases of the Kidneys. Naturally, the kidneys, working all the time and pouring out, as they do every day, from three to four pints of the liquid waste called urine, are subject to numerous diseases and disturbances. One of the common causes of these is failure to keep the skin thoroughly clean and healthy, as perspiration is of somewhat the same character as the urine; and if it be checked, it throws an extra amount of work upon the kidneys.

Another most important thing to keep the kidneys working well is to drink plenty of water, at least six or eight glasses a day, as well as to eat plenty of fresh green vegetables and fresh fruits, which, as we have seen, are eighty per cent water. Remember, we are a walking aquarium, and all our cells must be kept flooded with and soaked in water in order to be healthy. If the blood becomes overloaded with poisons, so much work may be thrown upon the kidneys that they will become inflamed and diseased and cannot form the urine properly; and then poisons accumulate in the system and finally produce serious illness and even death.

It was at one time believed that eating too much of certain kinds of foods, particularly those that leave much nitrogenous waste in the body, such as meat and fish, could produce a diseased condition of the kidneys, known as Bright's Disease; but we have found that the larger part of such cases are due to the attack of the germs of infectious diseases, particularly scarlet and typhoid fevers, tuberculosis, and colds. The popular impression that colds from wet feet or long drives in winter may "settle in the kidneys" is wrong, except in so far as those colds are caused by infectious germs.

Another cause of disturbance and permanent damage to the kidneys is the habitual use of alcohol. Even though this may be taken in only moderate amounts, the constant soaking of the tissues with even small amounts of alcohol may be most harmful to the kidneys, as well as to the liver.



CHAPTER XVIII

THE MUSCLES

Importance of the Muscles. It wouldn't be of much use to smell food, if we couldn't pick it up and bite it after we had reached it; or to see danger, if we were not able to move away from it. Every animal that lives, moves; and every movement, whether of the entire body from one place to another, or of parts of the body changing their relations to one another, or altering their shape, is carried out by an elastic, self-moving body-stuff, which we call muscle.

All the work that we do, whether in earning our living, or catching our food, or chewing it, or swallowing it and driving it through our food tube, or pumping the blood through our arteries, or drawing air into our lungs, is done by muscles. Hence, a very large part of the body has to be made of muscles. In fact, our muscles, put together, weigh almost as much as all the other stuffs in the body, making over forty per cent of our weight.

How the Muscles Act. The commonest form of muscle that we see is the red, lean meat of beef, mutton, or pork; and this will give us a good idea of how our own muscles look. All muscles, whatever their size or shape, are made up of little spindle-shaped or strap-shaped cells, or wriggling "body-cells" arranged in bands or strings. The size of a given muscle depends upon the number of cells that it contains.

The astonishing variety of movements which muscles can make is due to the fact that they have the power when stirred up, or stimulated, of changing their shape. As most of the muscle substance is arranged in bands, this change of shape on the part of the tiny cells that make up the band means that the band grows thicker and at the same time shorter,—just as a stretched rubber band does when it slackens,—so that it pulls nearer together the bones or other structures to which it is fastened at each end by fibrous cords called tendons, or sinews. This shortening of the muscle band is known as contraction.

When you wish, for instance, to lift your hand toward your face, you unconsciously send a message from your brain down the nerve cables in your spinal cord, out through the nerve-wires of your neck and shoulder, to the big biceps muscle on the front of your upper arm. This muscle then contracts, or shortens, and pulls up the forearm and hand, by bending the elbow joint. Just in proportion as the muscle becomes shorter, it becomes thicker in the middle; and this you can readily prove by grasping it lightly with your fingers when it contracts, and feeling it bulge.[22]

The food tube is surrounded with muscles, as you will remember, for moving the food along it, or churning it. These internal muscles, requiring only the presence of food to cause them to act, and not needing attention on the part of the brain or the will, are known as the involuntary ("without the will") muscles.

The great group of the voluntary, or bone-moving muscles, which move "with the will" and are under our direct control, may be divided roughly into two divisions—those that move the trunk, or body proper, and run, for the most part, lengthwise of it; and those that move the limbs.

On the body, they may be divided into two great sheets—one running up the front, and the other up the back. When those running up the front of the body contract, they naturally bend the back, and pull the head and shoulders forward and downward. Or, as when you spring up and catch the branch of a tree or a horizontal bar with your hands, these same muscles will pull the lower part of the body and legs upward, so that you can climb into the tree.

The largest and thickest bands of these front body muscles are found over the abdomen, or stomach, where you can feel them thicken and harden when you bend your body forward and pull with your arms, as in hauling on a rope. By their pressure upon the intestines, they give the bowels valuable support, assist in their movements, and help the circulation of the blood through them; so that it is of considerable importance to keep this entire group of muscles well toned up by exercises, such as swinging your arms back over your head, and then down between your legs; bending the head and shoulders backward and forward; swinging the legs up over the body, either when hanging from a bar or lying on your back. Proper exercising and toning up of these muscles will often cure constipation and dyspepsia, by their influence upon the bowels and stomach, and also keep one from taking on fat around the waist too rapidly.

On the back of the body, the muscle-sheet has grown into great, thick ropes of muscle on each side of the backbone, which you can feel hardening and softening in the small of the back, when you stoop down or lift weights. These are the muscles that hold the body erect, and keep the back straight when you stand, and are the largest and hardest working group of muscles in the body. Every minute that you sit, or stand, they are at work; and that is why they so often get tired out, and ache, and you say you have "a backache." They have to work harder to keep you erect or upright when you are standing perfectly still than when you walk or run, so that standing perfectly still is the hardest work you can do. Next to standing still, the hardest thing is to sit still, as you probably have found out. If it were not for these great muscles of the back and abdomen, we should double up like a jack-knife, either forward or backward, when we tried to stand up. It is not our skeleton that keeps us stiff or erect, but our muscles.



If you want to keep straight and erect, and thus have a good carriage, you must keep these great body muscles well trained and exercised by swinging movements, such as bending the back forward, standing with your feet apart and then swinging your head and shoulders down and between your legs; or, with your heels together, swinging your hands down till the fingers touch the ground; or by the different exercises that either bend your back, or hold it stiff and erect. Swinging from a bar, rowing, digging with a spade, chopping or sawing wood, dancing, rope-skipping, ball-playing, hop-scotch, and wrestling, all develop these muscles finely and are good for both boys and girls.

Other strands of these muscles branch out to fasten themselves to the shoulder blades and shoulders, where they help to draw the arm back as for a blow, pull the shoulders into position when you stand upright, or, when you have leaned forward and grasped something with the hand, help to pull up the arm and lift it from the ground. These muscles are quite important in holding the shoulders back and giving a good shape to the chest and good carriage of the upper part of the body and head. They are called into play in all exercises like striking, batting, tennis-playing, ball-throwing, swinging, shoveling, swimming, as well as in pulling, in lifting weights, in swinging an axe or handling a broom.



The muscles of the limbs are almost as numerous as those of the trunk of the body, and even more complex. Most of them, on both arms and legs, are in two great groups—one known as the "benders," or flexors, which, when they shorten, bend the limb; and the other, the "straighteners," or extensors, which straighten or extend it.

On the front of the arm, for instance, we have the large biceps ("two-headed") muscle, which runs from the shoulder to the bone of the forearm just below the elbow and, when it shortens, bends the elbow and lifts the arm toward the body.

On the back of the upper arm is the triceps ("three-headed") muscle, which is fastened at its lower end to a big spur of bone, the "point" of the elbow; when it shortens, acting lever fashion, it straightens or extends the arm. If this is done quickly, the fist is swung outward with force enough to strike quite a sharp blow, though, as you know, if you wish to hit really hard, you have to strike with the weight and muscles of the full arm and the body behind it, or, as we say, "from the shoulder."



In the lower limbs, the muscles are larger because they have heavier work to do, supporting and moving the whole weight of the body; but they are simpler in their arrangement since they have not such a variety of movements to carry out. The principal muscle in the thigh is the great muscle running down the front of the thigh, and fastening to the upper border of the patella, or knee cap. This muscle, when it shortens, straightens or extends the limb, or lifts the foot from the ground and swings it forward as in walking, or raises the knee up toward the body when we are sitting or lying down. You can easily tell how much it is used in walking by remembering how stiff and sore it gets when you have taken an unusually long tramp, particularly if there has been much hill-climbing in it. On the back of the thigh, runs another great group of muscles, which bend or flex the limb when they shorten. When the knee is bent, you can feel their tendons, or sinews, stand out as hard cords beneath the knee; hence, this group is called the ham-string muscles.[23]

How the Muscles are Fed. Our muscles are not only the largest, but the "livest" part of our bodies. Their contractions and movements are caused by their tiny "explosions" (like the chugging of an automobile, except that we can't hear them); and in this way they burn up the largest part of the food-fuel which we eat—mostly in the form of sugar. When they have burned up their surplus food-fuel, they call for more; and when this demand has been telegraphed to the brain, we say we are hungry, and that exercise has given us an appetite. While the muscles are at work, they demand that large supplies of fresh fuel shall be brought to them through the blood vessels; and this makes the heart beat harder and faster, and improves the circulation. As they burn up this fuel, they form smoke and ashes, or waste materials, which must be got rid of—the fluid part by perspiration from the surface of the skin, and through the kidneys, and the gas, or "smoke," through the lungs. This is the reason why, during exercise, we breathe faster and deeper than at other times, and why our skin begins first to glow and then to perspire.

If these waste-materials form in the muscles faster than the blood can wash them out, they poison the muscle-cells and we begin to feel tired, or fatigued. This is why our muscle-cells are often so stiff and sore next morning after a long tramp, or a hard day's work, or a football game. A hot bath or a good rub-down takes the soreness out of the muscles by helping them to get these poisonous wastes out of their cells.

Thus when we play or run or work, we are not only exercising our muscles and making them gain strength and skill, but we are stirring up, or stimulating, almost every part of our body to more vigorous and healthful action.

Indeed, as our muscles alone, of all our body stuffs, are under the control of the will, our only means of deliberately improving our appetites, or strengthening our hearts or circulation, or invigorating our lungs, or causing a large part of our brains and minds to grow and develop, is through muscular exercise. This is why nature has taken care to make us all so exceedingly fond of play, games, and sports of all sorts, in the open air, when we are young; and, as we grow older, to enjoy working hard and fighting and "hustling," as we say; and that is the reason, also, why we are now making muscular exercise such an important part of education.

FOOTNOTES:

[22] The muscle does not get any bigger when it contracts, as was at one time supposed; if you were to plunge it into a bath of water, and then cause it to contract, you would find that it did not raise the level of the water, showing that it was of exactly the same size as before, having lost as much in length as it gained in thickness.

[23] In the leg below the knee, and in the forearm, we have two groups of "benders" or flexors, and "straighteners" or extensors, as in the upper arm and leg, only slenderer and more numerous. They taper down into cord-like tendons at the wrist and ankle to fasten and to pull the hands and feet "open" and "shut," just as do the strings in the legs and arms of a puppet or mechanical doll, or the sinews in the foot of a chicken.



CHAPTER XIX

THE STIFFENING RODS OF THE BODY-MACHINE

What Bones Are. The bones are not the solid foundation and framework upon which the body is built, as they are usually described. They are simply a framework of rods and plates which "petrified," or turned into spongy limestone after the body was built, to make it firmer and stiffen it for movement. All the animals below the fishes, such as worms, sea-anemones, oysters, clams, and insects, get along very well without any bones at all; and when we are born, our bones, which haven't fully "set" yet, are still gristly and soft. The cores of the limbs, as they begin to stiffen, first turn into gristle, or cartilage, and later into bone; indeed, many of our bones remain gristle in parts until we are fifteen or sixteen years of age. This is why children's bones, being softer and more flexible than those of grown-up people, are not so liable to break or snap across when they fall or tumble about; and why, too, they are more easily warped or bent out of shape through lack of proper muscular exercise and proper food.

Bones are strips of soft body-stuff soaked with lime and hardened, like bricklayer's mortar, or concrete.[24] When you know the shape of the body, you know the bones; for they simply form a shell over the head and run like cores, or piths, down the centre of the back, and down each joint of the limbs.

In turning into spongy limestone, or animal concrete, they have become one of the deadest tissues in the body. They are tools of the muscles, the levers by which the muscles move the limbs and body about; they never do anything of their own accord. On account of their lifelessness and lack of vitality, they are rather easily attacked by disease, or broken by a blow or fall. There are such a large number of bones (two hundred and six, all told), and they resist decay and last so much longer after death than any other parts of the body, that they fill our museums and text-books of anatomy, form most of our fossils, and have thus given us rather an exaggerated idea of their importance during life.



The Frame-Work of the Body. Just look at any part of the body and imagine that it has a bony core of about the same general shape as itself, and you can reason out all the bones of the skeleton. To begin at the top, the skull is a box of strong, plate-like bones, which have hardened to protect the brain as it grew; and the shape of its upper, or brain, part is exactly that of the head, as you can easily feel by laying your hands upon it. Then come bony shells, or sockets, for the eyes and nose; and, below these, two heavy half-circles of bone, like the jaws of a steel trap, to carry the teeth.

The thickness of the lower jaw and the size and squareness of the angle where it bends upward to be hinged to the skull, below the ear, are what give the appearance of squareness and determination to the faces of strong, vigorous men or women. If we want to imply that a person has a feeble will, or weak character, we say he has a "weak jaw."

The skull rests upon the top of the backbone, or spinal column, which, instead of being one long solid bone, is made up of a number of pieces, or sections, known as vertebrae. Each one of these vertebrae has a ring, or arch, upon its back. These, running one after the other, form a jointed, bony tube to protect the spinal cord, or main nerve-cable of the body, which runs through it.



Although the backbone can bend forward or backward, or twist from side to side a little, by the little pieces of bone of which it is built up gliding and turning upon one another, it is really very stiff and rigid, so as to protect the spinal cord and prevent its being stretched or pinched. Most of the movements which we call bending the spine are really movements of other joints which connect the body or head with it. When we bend our necks, for instance, we hardly bend the backbone at all, as most of the movement is made in the joint at the top of it, between it and the skull. Similarly, when we bend our backs, we really bend our backbones very little; for most of the movement comes at the hip joints, between the thighs and the hip bones.

Each of the limbs has a single, long, rounded bone in the upper part, known in the arm as the humerus, and two bones in the lower part. These last are known as the radius and ulna (the "funny bone") in the forearm, and the tibia and fibula in the leg. The shoulder-joint is made by the rounded head of the humerus fitting into the shallow cup of the scapula, or shoulder-blade. It is shallower than the hip joint to allow it freer movement; but this makes it weaker and much more easily dislocated, or put out of joint,—the most so, in fact, of any joint in the body.



The hip joints are deep, strong, cup-shaped sockets upon each side of the hip bones, or pelvis, into which fit the heads of the femurs or thigh bones. When the hip joint does become dislocated, it is very hard to put back again, on account of its depth and the heavy muscles surrounding it. It is quite subject to the attack of tuberculosis, or "hip-joint disease."



The joints, or points at which the bones join one another, look rather complicated, but they are really as simple as the bones themselves. Each joint has practically made itself by the two bones' rubbing against each other, until finally their ends became moulded to each other, and formed the ball-and-socket, or the hinge, according to whichever the movements of the "bend" required. The ends, or heads, of the bones which form a joint are covered with a smooth, shining coating of cartilage, or gristle, so that they glide easily over each other.