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.
[Illustration: =The skin (x100).=
_a_, _b_ and _c_ epidermis.
_d_ and _g_ tough and thick part of skin.
_e_ sweat gland.
_f_ blood tubes.
_h_ fat pockets.]
=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.
[Illustration: =A hair (x200).=
_a_ the surface of the skin.
_b_ a hair.
_c_ an oil gland.
_d_ a muscle to make the hair stand on end.
_e_ and _g_, the growing cells of the hair.
_f_ fat in the skin.]
=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 Sec. 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.