e?

3. Where is the blood made pure and red again?

4. Where is it sent, from the lungs?

5. What must the lungs have in order to do this
work?

6. When do the lungs rest?

7. Why should we not wear tight clothes?

8. How does the air in a room become spoiled?

9. How can we keep it fresh and pure?

10. How should we breathe?

11. Why is it better to breathe through the nose
than through the mouth?

12. Why is alcohol not good for the lungs?

CHAPTER XVI.

THE SKIN.

[Illustration: T]HERE is another part of your body carrying away waste
matter all the time--it is the skin.

The body is covered with skin. It is also lined with a more delicate
kind of skin. You can see where the outside skin and the lining skin
meet at your lips.

There is a thin outside layer of skin which we can pull off without
hurting ourselves; but I advise you not to do so. Because under the
outside skin is the true skin, which is so full of little nerves that it
will feel the least touch as pain. When the outer skin, which protects
it, is torn away, we must cover the true skin to keep it from harm.

In hot weather, or when any one has been working or playing hard, the
face, and sometimes the whole body, is covered with little drops of
water. We call these drops perspiration (p[~e]r sp[)i] r[=a]'sh[)u]n).

[Illustration: _Perspiratory tube._]

Where does it come from? It comes through many tiny holes in the skin,
called pores (p[=o]rz). Every pore is the mouth of a tiny tube which is
carrying off waste matter and water from your body. If you could piece
together all these little perspiration tubes that are in the skin of one
person, they would make a line more than three miles long.

Sometimes, you can not see the perspiration, because there is not enough
of it to form drops. But it is always coming out through your skin, both
in winter and summer. Your body is kept healthy by having its worn-out
matter carried off in this way, as well as in other ways.

THE NAILS.

The nails grow from the skin.

The finger nails are little shields to protect the ends of your fingers
from getting hurt. These finger ends are full of tiny nerves, and would
be badly off without such shields. No one likes to see nails that have
been bitten.

CARE OF THE SKIN.

Waste matter is all the time passing out through