ry much as a man uses the telephone or
telegraph wires.

17. With the large brain we remember, think, and reason.

18. The little brain does the simple kind of thinking, by means of which
the heart, lungs, and other vital organs are kept at work even when we
are asleep.

19. The spinal cord does a still more simple kind of work. It enables us
to walk and to do other familiar acts without using the large brain to
think every moment just what we are doing.

CHAPTER XXIII.

HOW TO KEEP THE BRAIN AND NERVES HEALTHY.

~1. Uses of the Brain.~--What do you think a boy or girl would be good
for without any brain or nerves? Such a boy or girl could not see, hear,
feel, talk, run about, or play, and would not know any more than a
cabbage or a potato knows. If the brain or nerves are sick, they cannot
work well, and so are not worth as much as when they are healthy.

~2. The Brain Sympathizes with Other Organs.~--Did you ever have a
headache? Did you feel happy and good-natured when your head ached hard,
and could you study and play as well as when you are well? It is very
important that we should keep our brain and nerves healthy, and to do
this we must take good care of the stomach and all other organs, because
the brain sympathizes with them when they are sick.

~3. We must have Pure Air.~--How do you feel when the school-room is too
warm and close? Do you not feel dull and sleepy and so stupid that you
can hardly study? This is because the brain needs good, pure blood to
enable it to work well. So we must always be careful to have plenty of
pure air to breathe.

~4. We should Exercise the Brain.~--What do we do when we want to
strengthen our muscles? We make them work hard every day, do we not? The
exercise makes them grow large and strong. It is just the same with our
brains. If we study hard and learn our lessons well, then our brains
grow strong, and study becomes easy. But if we only half study, and do
not learn our lessons perfectly, then the study does not do our brains
very much good.

~5. We should Take Muscular Exercise.~--When you get tired of study, an
hour's play, or exercise of some sort, rests you and makes you feel
brighter, so that you can learn more easily. This is because exercise is
necessary to make the blood circulate well. It will then carry out the
worn-out particles and supply the brain and nerves with fresh, pure
blood. So the same exercise which makes our muscles strong makes our