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 brains healthier also.

6.  We should be Careful of our Diet.—­We ought to eat plenty of good, simple food, such as milk, fruits, grains, and vegetables.  It is not well for children to eat freely of meat, as it is very stimulating and likely to excite the brain and make the nerves irritable.  Mustard, pepper, and all hot sauces and spices have a tendency to injure the brain and nerves.

7.  We should Allow the Brain to Rest at the Proper Time.—­When we are tired and sleepy we cannot think well, and cannot remember what we learn if we try to study.  If we have plenty of sleep, free from bad or exciting dreams, we awake in the morning rested and refreshed, because while we have been asleep Nature has put the brain and nerves in good repair for us.  We ought not to stay up late at night.  We should not eat late or hearty suppers, as this will prevent our sleeping well.