ne, or tobacco may hinder the body from using food
for growth, or they may poison the body so that it will never be large
and strong. The body should grow about a hundred pounds in weight
during the first thirteen years of life. Whether children grow little
or much generally depends on the food they give their bodies.

PRACTICAL QUESTIONS

1. Point out and name four parts of the body.

2. Name the two parts of the trunk.

3. What does the chest contain?

4. What is muscle?

5. How is the body fed?

6. Give three parts taking waste out of the body.

7. Of what use are the brain and nerves?

8. Name two organs.

9. How long does the body continue to grow?

10. Why are some children weak and of slow growth?

CHAPTER III

FEEDING THE BODY

[Illustration: FIG. 6.--Photograph of the outer dead skin pushed off
from a black snake crawling through the brush.]

=Why the Body needs Food.=--Every living thing, whether a plant or an
animal, needs food. While the whole body lives, a part of it is
constantly dying. The entire outer layer of a snake's skin dies three
or four times during a year and is cast off, sometimes in a single
piece. We can scrape dead bits of skin from the surface of our body at
any time. Tiny particles are dying in all regions of the body, and we
should soon waste away if food were not taken to make up the loss for
the worn-out parts.

The body also needs food to help it do its work and keep warm. The body
has the strange power of using food eaten to make the legs and arms move
and the brain to think. In doing this the body is said to burn the food.

=How the Body burns itself and also Food.=--If a boy is weighed just
before playing a game of ball and again afterward, he will find that
part of his body has been used up and given off in the breath and
sweat. He has burned part of his body, and the breath and sweat are
like the smoke given off when a match is burned.

One fifth of the air is made of a gas called _oxygen_. When anything
becomes very hot, this oxygen makes it burst into a flame and burn. We
breathe in oxygen with the air and the living action of the body
causes such a slow union of the oxygen and the tissues that there is
no blaze although there is a little heat.

=Kinds of Food.=--There are four general classes of foods. These are
the _building foods_, the _sugars_ and _starches_, the _fats_, and the
_mineral foods