Chapter 11

THE SKIN AND KIDNEYS

=122. Waste matters.=--The food is burned in the cells. As this burning goes on, the _smoke_ goes off by the lungs and the unburned substances, the _ashes_, go off by the skin and kidneys. The ashes are mostly the minerals of the cells, but there are also some from the burned albumin. All these go back to the blood and are carried to the skin and kidneys.

=123. The skin.=--The skin covers the whole body. It is strong and keeps the body from being hurt.

=124. The epithelium.=--The skin is covered with a thin layer of cells like fine scales. These scales are called _epithelium_, or _epidermis_. They have no blood tubes or nerves and so have no feeling. You can run a pin under them without feeling pain. They are always growing on their under side and wearing off on their upper side. They keep the nerves and blood tubes of the skin from being hurt.

=125. The nails.=--The top scales of epithelium at the ends of the fingers become matted together to make the nails. The nails keep the ends of the fingers from being hurt. They can also be used to hold or cut small things. The new parts of the nails form under the skin and push down the older parts. So the nail grows farther than the end of the finger and needs to be cut off. Biting the nails leaves their ends rough. Then they may catch in the clothes and tear into the tender flesh. We ought to keep the nails cut even with the ends of the fingers.

The nails are not poisonous, but the dirt under them may be. We ought to keep them clean. Clean nails are one mark of a careful boy or girl.

=126. Hair.=--Some of the scales of epithelium over some parts of the body dip into tiny holes in the skin. In each hole they become matted together to form a _hair_. Fine short hair grows on almost every part of the body. On the top of the head it grows long and thick. When boys become men, it also grows long upon their faces. The skin pours out a kind of oil to keep the hair soft and glossy.

=127. Care of the hair.=--The hair may become dirty like any other part of the body. Brushing it takes out a great deal of dirt, but you should also wash it once a week.

The oil in the skin ought to be enough for the hair. Hair oils do not do the hair any good. If you wet the hair too often, you may make it stiff and take away its gloss. It is best to comb the hair dry. Brush it so as to spread the oil of the skin. Hair dyes are poisonous, and ought not to be used.

=128. The sweat or perspiration.=--The scales of epithelium dip into the skin and there line tiny tubes. The tubes form the _sweat_, or _perspiration_, out of the blood. The tubes are too fine to be seen, but they are upon almost every part of the body. They take the ashes or other waste matter or poisons from the blood and wash them out of the tubes with the perspiration. So the perspiration has two uses. First, it takes heat away from the body (see § 108). Second, it gets rid of the waste matters or ashes of the body. It has very little of these at any one time, but in a day it gets rid of a great deal.

=129. The kidneys.=--The kidneys are close to the backbone, below the heart. They are made of tiny tubes much like the sweat tubes in the skin. The tubes take ashes and other waste matters from the blood, also a great deal of water. They also take away poisons and disease germs when we are sick. The kidneys take away about as much water as the skin, but they get rid of very much more poisons and waste matters than the skin does. If our kidneys should stop their work, we should soon die.

=130. Need of bathing.=--When the perspiration dries from the skin, it leaves the waste and poisons behind. We cannot always see the dried matters, but they always have an unpleasant odor. We should bathe often enough to keep our body from having an unpleasant smell. We should wash the whole body with soap and hot water at least once a week in winter and more often than that in summer.

Another reason for bathing is to wash disease germs from the body. Most dirt has disease germs in it. Disease germs also float in the dust of the air and stick to our skin when we go into a dusty room. If our skin is dirty, some of the germs may be carried into our flesh when our skin is pricked, or scratched, or cut. We sometimes catch boils, or erysipelas, or lockjaw, from very little wounds in a dirty skin. Cleanliness of our skin helps to keep us from catching diseases.

=131. Cold baths.=--Sometimes we bathe when we are clean so as to get refreshed. If we bathe in cold water, we feel cold at first. In a little while we feel warm again. Then we feel stronger, and refreshed for work. If we stay in the bath too long, we become cold again and feel weak. When boys go in swimming, they ought to come out before they begin to feel cold.

It is a good plan to take a cold bath every morning when you get up, even if you use only a wash-bowl with a little water. It will take only a few minutes, but will keep you clean and make you feel more like doing your day's work.

=132. A fair skin.=--We must wash often, to make the skin fair and smooth. Use enough good soap to keep the skin clean.

If you eat as you should, and digest the food well, your skin will have the least amount of waste to give off. Then it will look well. A bad looking skin is due to bad food and to bad digestion. If you do not digest your food well, you cannot have a fair skin.

Face paint and powder make the skin look worse, for they hinder perspiration. Nothing of that sort will do the skin any good. You must eat as you should, and you must keep clean. Then your skin will be clear.

=133. Washing clothes.=--Our clothes rub off a great deal of the perspiration and waste. They become soiled. A great deal of dirt also gets upon the sheets of our beds. Our clothes need to be washed as well as our bodies when they are soiled. Air and the sun as well as water destroy the waste of the body. Our clothes need to be aired at night, and the bed and bedroom should be aired through the day.

=134. Slops.=--After water has been used to wash our body or our clothes it is dirty and is not fit to be used again. It must not be thrown where it can run into a well. If a person has typhoid fever or cholera or other catching disease, the water may carry germs of the disease to the well, and so other persons may get it. Slops from the house should not be poured out at the back door, but they should be carried away from the house. In cities the slops are poured into large pipes and tunnels underground. These pipes are called _sewers_. They empty outside the city.

=135. Alcohol and the skin.=--Alcohol interferes with digestion and causes biliousness. This makes the skin rough and pimply. A drinker seldom has a clear skin.

Alcohol causes the arteries of the face to become enlarged. Then the face is red. A red nose is one of the signs of drinking. When a person uses strong drink he is often uncleanly. He does not care for the bad looks of his clothes and skin, and so he lets them stay dirty. This harms the skin and makes it look bad. The dirt also poisons the skin and may itself be a cause of sickness.

Because alcohol poisons the whole body and often produces kidney diseases, the drinker is apt to catch other diseases. Drinkers are the first to catch such diseases as smallpox and yellow fever. Where there are great numbers of cases, the drinkers are the first and often the only persons to die. This is because their skin and kidneys have been harmed by the alcohol and cannot throw off the poisons of the disease. Any kind of sickness will be worse in a drinker. Surgeons do not like to operate on drinkers, for their wounds do not heal so quickly as in other people.

When there is too little air, a fire burns slower, and makes a blacker smoke and more ashes. Alcohol takes some air from the cells of the body. So they burn with smoke and ashes of the wrong kind. The skin has to work harder to get rid of these, and sometimes it cannot do it well. Then the body is poisoned. The alcohol is burned and cannot poison the body any more. But it causes the body to make poisons, and so it is to blame. The poisons do great harm to the skin and kidneys. Alcohol causes more kidney disease than all other things put together.

WHAT WE HAVE LEARNED

1. Little tubes in the skin are always giving off ashes and waste matters in the perspiration.

2. Perspiration dries on the skin. So the skin must be washed often.

3. The kidneys get rid of more water and waste matter than the skin does.

4. Perspiration also gets upon the clothes and bed sheets. These must be washed too.

5. Dirty water from washing should be thrown out where it cannot run into a well.

6. The skin is thick and strong and keeps the body from being hurt.

7. The skin is covered with a layer of scales. The scales have no feeling.

8. The scales form the nails on the ends of the fingers.

9. The scales also form the hair.