It covers the body, like a very tight suit of clothes. It has two layers, an outer layer of scarf skin, and an inner layer of true skin. When you have a blister on your hand, the outer scarf skin is puffed up by a liquid (the lymph)
which collects between it and the true skin. The scarf skin, as you know from this experience, is very thin. The inner skin is thicker; leather is made from the inner skin of an animal, hardened by a special treatment called tanning.
The skin is growing all the time in its deeper layers and shedding off scales of dead tissue at the top. These scales are usually rubbed off in washing or by the friction of clothing, so that we do not notice them.
When the skin is subject to special pressure or friction at any one place, it grows thicker and forms a hardening, called a callosity. Rowers or baseball players often get callous places on their hands, and people who walk a great deal are likely to have them on their feet. Corns are formed by such thickenings of the skin.
The Functions of the Skin.The skin does several kinds of work. It keeps out disease germs and protects the soft, moist inside parts of the body from being injured and from losing water too fast by evaporation. It is by means of the blood vessels in the skin that the body gives off the heat which is constantly being produced inside; and by means of the sweat glands, the skin helps to get rid of the body wastes. The evaporation of the sweat which collects on the skin, as we have seen, cools the body and thus helps in the regulation of the body temperature.
Still another important work is accomplished by the little sense organs and nerves in the skin, by which we touch and feel, and learn a great deal about the world around us. It is through these organs of touch that we find out whether a thing is wet or dry, hot or cold, soft or hard.
Clothing and Shelter.In cold weather the unclothed body would lose heat too fast, even if all the blood vessels of the skin contracted so as to become as small as possible. Birds have feathers and many animals have thick coats of hair to keep their heat in, but we must wear clothing to protect ourselves from cold. We must also have our houses specially warmed in cold weather. Next to food, clothing and shelter are the chief needs of the savage, and they demand a large proportion of the earnings of members of civilized society to-day. Men and women who support themselves and their families are called “bread-winners.” They must be house-winners and clothes-winners as well.
Kinds of Clothing.In choosing our clothing, we should remember that some materials are particularly effective in keeping heat in, while others allow it to escape more rapidly to the outside air. Most of our clothing is made of animal hairs (woolen cloth and furs), of plant tissue (cotton or linen), or of silk, which is a fine web spun by a caterpillar. Woolen clothes are warm because they are very porous and hold a great deal of air; the air serves to retain the warmth or, as we sometimes say, it is a poor conductor of heat. Wool also takes up moisture readily, so that if it is moistened with perspiration it does not feel so wet and does not chill the body so much as other materials. Cotton is cooler and softer and is better fitted for warm-weather clothing.
It is well to remember that several layers of comparatively thin clothing are often warmer than one layer of thick clothing. The reason for this is that the air between the thicknesses of cloth helps to keep the heat of the body from escaping. A newspaper folded under the clothing will prove a considerable protection against sudden cold, because of the layers of air between its folds.
Hygiene of the Clothing.It is important to regulate the amount of the clothing with some care. If clothes are so thin that the body becomes chilled, colds and rheumatism and other diseases may result. We should be careful to be warmly wrapped while sitting still or lying down in the cold air. When we are active and are using the muscles a great deal, more heat is formed in the body and less clothing is neededwhile the exercise is going on. People often, however, become heated by exercise and afterward sit down or stand in cold drafts. This is one of the easiest methods of getting a cold. After exercise, the blood vessels in the skin are expanded, the body is wet with perspiration, and heat is being rapidly drawn off by its evaporation. If the body in this condition is exposed to a cold draft of air, it becomes cool too rapidly and a chill is likely to result. Even at the risk of being a little too warm for a few minutes, one should put on an extra wrap until the body has regained its normal temperature.
Wet clothes and shoes are likely to cause chills, because water conducts heat away from the body very rapidly. We should be careful, therefore, to change damp clothing for dry things as soon as possible.
On the other hand, it is just as undesirable to wear clothes that are too warm as to expose the body to undue chill. As we have seen in the chapter on “Air and Health,” if the skin cannot get rid of its heat fast enough, we feel dull and sleepy. People who have the habit of wearing too many clothes weaken the power of their systems to respond quickly to changes in temperature, and so are especially susceptible to colds. The way to keep the skin and its blood vessels in good condition is to wear light clothing indoors and to put on outer wraps when one goes out into the cold.
Hygiene of Bathing.The first object of bathing is, of course, to keep clean. Not only should the dirt and soot which soil the body be washed off, but the waste materials deposited on the skin by perspiration must also be removed. If a daily bath is not taken, the body and the clothing soon acquire an unpleasant odor.
Warm or tepid water is most effective for cleansing the hands or body. Bathing in warm water increases the size of the blood vessels in the skin and draws the blood away from the brain, making one feel comfortably sleepy. This is the reason why a warm bath should usually be taken at bedtime.
A cold bath contracts the skin blood vessels and drives the blood to the internal organs and the brain, making one feel alert and keen. Cold bathing is a powerful tonic to the skin, since it trains these blood vessels to respond quickly to changes in temperature. People who take cold baths regularly are likely to be hardy and little subject to colds.
In the matter of bathing, however, we must again remember that the body should be stimulated by cold but not chilled too much. A cold bath should be followed by a reaction; that is, the surface blood vessels should enlarge again so that the skin becomes warm and glowing. Brisk rubbing with a rough towel helps to secure this reaction. If no reaction follows, or if one feels tired after bathing, the bath was too cold or too prolonged, or the body is not strong enough to endure the shock. In such cases, cold baths may do serious harm.
No bath of any kind should be taken within an hour after eating. The blood is needed in the intestines for the process of digestion, and it is harmful to disturb the circulation, as any bath must do, at such a time.
The Care of the Hair.The hair is a kind of outgrowth of the skin, as are the feathers of birds and the scales of fishes. Each hair grows out of a tiny cup called a hair follicle. Opening into the hair follicle are glands which discharge an oily secretion that keeps the hair soft and flexible. (See Fig. 6o.)
Vigorous brushing of the hair is necessary, not only to keep the hair free from snarls and neat in appearance, but also to keep the scalp healthy, by bringing the blood into it and working the natural oil out to the ends of the hairs. Washing the hair with warm water and good soap at least once a month is desirable, in order that the scalp may be kept clean of scales and dirt. After washing, the hair should be thoroughly rinsed to remove all the soap.
Microbes on the Skin.Germs of various kinds are al-ways present on the skin. These germs ordinarily do no harm, but when a person is “run down,” tired, and in poor condition, they may grow in a hair follicle and cause a little swelling or pimple. Boils or carbuncles are more extensive germ infections of this kind. Children may occasionally have pimples and even a boil without any serious cause, but if the pimples appear frequently a physician should be consulted.
The Care of the Nails.The nails are folds of the skin that have become hard and horny at the ends, but are alive and growing at the base. Finger nails are great dirt catchers, and special care is required to keep them clean. Black-bordered finger nails are an unpleasant sight, and there is always a possibility that dirty nails (which are germ-bearing nails) may introduce dangerous microbes into the skin by scratching or rubbing, or may carry pollution to one’s food. The nails should be kept fairly short so that they are not in danger of being broken. They should never be bitten or picked, as the result is always unsightly and these practices often lead to the tearing of the delicate flesh below the nail. Germs are likely to get into any such wounded place and may cause serious infections.
QUESTIONS FOR DISCUSSION AND REVIEW
1. What are the functions of the skin?
2. How does the skin grow? What color is it? What gives it this color?
3. How does the body get rid of the heat produced by the activities of its different organs?
4. How do we prevent the body from losing, heat too rapidly?
5. What are the three chief physical needs of mankind? Why?
6. What kinds of material can you name which are used for clothing? From what is each made?
7. Why is fur clothing warm? Is it warmer, worn with the fur side in or out? Why?
8. Up-to-date manufacturers are making underwear of thick loosely-woven cotton. How does this compare with woolen underwear?
9. Take pieces of wool, silk, and cotton, soak each thoroughly, and then see which will dry most quickly. What does this show you about the choice of material for clothing?
10. In bed clothing, which is better, one heavy blanket or two lighter ones?
11. Why do double doors and windows help to keep a house warm?
12. What is the danger when people try to “harden” them-selves quickly by wearing too little clothing?
13. Some boys were taking a long walk, and when they were five miles from home a heavy rain came up. Of course their feet became very wet. One of the boys feared that they would all take cold, but another said that it was all right provided they kept walking and changed their clothes as soon as they reached home. Which was right? Explain.
14. Why is it unsafe to come to school in the rain without rubbers or a change of shoes?
15. Is it safer to dress too heavily than to dress too lightly?
16. Why should material which is unwashable never be worn next to the skin?
17. For cleanliness, which is better, a warm or a cold bath? Which is better for “toning” the body? How can you get both effects?
18. What kind of bath is good at bedtime? What kind after hard exercise? Why?
19. In swimming, we often find that the water feels icy cold at the first plunge. Why does it seem warmer after we have been swimming for a while? If the swimmer does not succeed in warming up, what is probably the matter?
20. How are the skin and the hair kept soft and flexible?
21. Why does brushing the hair help to make it glossy?
22. What are pimples?
23. How should the nails be cared for?