en and women who
work should have about eight hours of sleep daily to remain in good
health. Children of twelve years should sleep nine hours each day;
those of ten years, ten hours; those of seven years, eleven hours; and
those of four years, twelve hours.

=Getting the most out of Sleep.=--You should go to bed every night at
about the same hour. This will help you to fall asleep as soon as you
are in bed. Do not sleep in the clothes which you have worn during the
day, but hang them up to air, and put on a night robe.

Children should use a very low pillow, so that the body can lie
straight in the bed. This gives the lungs and heart freedom to act. Do
not lie on the back as this causes some of the organs to press on
certain nerves and makes you dream. The windows should be opened wide
because fresh air is the best aid to rest and health and keeps away
tuberculosis.

PRACTICAL QUESTIONS

1. What makes the parts of the body work together?

2. Describe the surface of the brain.

3. Name the three parts of the brain.

4. Of what is the outer layer of the brain made?

5. Where is the spinal cord?

6. What are nerve fibers?

7. What work does the brain do?

8. What makes the mind good or bad?

9. What is habit?

10. How long should children sleep?

11. How can you get the most good out of sleep?

CHAPTER XXI

HOW NARCOTICS AND STIMULANTS AFFECT THE BRAIN AND NERVES

=What Narcotics and Stimulants Are.=--A _narcotic_ is something which
when taken into the body makes the organs do their work more slowly
and tends to cause sleepiness. Alcoholic drinks, tobacco, opium,
soothing sirups, and pain killers are narcotics.

A _stimulant_ is a substance which makes the organs of the body do
more and quicker work and does not later make the organs work more
slowly. Coffee and tea are stimulants. Beer, wine, and whisky were
once thought to be stimulants, but experiments have shown them to be
narcotics. They urge the brain to faster work for a few minutes, but a
half hour later they make it act slower than usual.

=Alcohol hurts the Brain.=--Within five minutes after a drink of beer
or whisky has been swallowed, part of the alcohol has reached the
blood. Within fifteen minutes much of the alcohol has gone from the
stomach directly into the blood. In a minute after entering the blood
vessels it reaches the brain.

If much strong drink is taken, the ce