effect does strong drink have on the brain?

7. Does alcohol help us think better?

8. What facts show that alcohol sends men to prison?

9. What shows that alcohol makes the mind sick?

10. Why is it dangerous for the young to take strong drink?

11. What shows that tobacco makes the brain work slower?

12. Why should you not use opium or morphine?

13. What do pain killers contain?

CHAPTER XXII

THE SENSES, OR DOORS OF KNOWLEDGE

=The Organs of Sense.=--In order that our body may keep out of the way
of other persons and find food and drink and do its work, the brain
must have some way of receiving news about what is near us, how it
looks, and of what it is made. Special organs for receiving knowledge
of people and things about us are scattered over the surface of the
body. They are called _sense organs_. The chief ones are the two eyes,
the two ears, the nose, and many organs of taste in the mouth, and the
thousands of tiny organs of feeling in the skin.

=The Eye.=--The eye consists of a globe called the _eyeball_ and parts
which move this and protect it from injury. Each eyeball is attached
at its back part to the large nerve of sight (Fig. 90). This carries
messages to the brain, telling it what the eye sees.

The eyeball is held in a socket in the front of the skull. A layer of
fat lines the socket and keeps the eye from being injured by jars. The
_eyebrows_ at the lower edge of the forehead prevent the sweat from
running into the eyeball.

[Illustration: FIG. 90.--Side of the face cut away to show the eyeball
in its socket. _n_ is the nerve of sight; the other letters show the
muscles which move the eyeball.]

The _eyelids_ can close over the front of the eyeball to shut out dirt
or anything else likely to hurt it. The lids have learned to do their
work so well that we do not need to think to close them when anything
flies toward the eye, for they are shut before we can think.

A salty fluid called _tears_ flows from the tear gland at the upper
and outer side of the eyeball. The tears keep the front of the eyeball
clean.

=Parts of the Eyeball.=--The outside of the eyeball is a tough white
coat except in front, where it is as clear as glass. Within the outer
coat is a very thin black lining to keep the light from scattering. In
front the lining is not against the outer coat, but hangs loose and
has in it a round hole called the _pupil_ to let the light p