Some way is needed to send the gray fluid that is made from the food we eat and drink, to every part of the body.

To send the food with the blood is a sure way of making it reach every part.

So, when the stomach has prepared the food, the blood takes it up and carries it to every part of the body. It then leaves with each part, just what it needs.

THE BLOOD AND THE BRAIN.

As the brain has so much work to attend to, it must have very pure, good blood sent to it, to keep it strong. Good blood is made from good food.

It can not be good if it has been poisoned with alcohol or tobacco.

We must also remember that the brain needs a great deal of blood. If we take alcohol into our blood, much of it goes to the brain. There it affects the nerves, and makes a man lose control over his actions.

EXERCISE.

When you run, you can feel your heart beating. It gets an instant of rest between the beats.

Good exercise in the fresh air makes the heart work well and warms the body better than a fire could do.

DOES ALCOHOL DO ANY HARM TO THE HEART?

Your heart is made of muscle. You know what harm alcohol does to the muscles.

Could a fatty heart work as well as a muscular heart? No more than a fatty arm could do the work of a muscular arm. Besides, alcohol makes the heart beat too fast, and so it gets too tired.

REVIEW QUESTIONS.

1. Where is the heart placed?

2. Of what is it made?

3. What work does it do?

4. What are arteries and veins?

5. What does the pulse tell us?

6. How does the food we eat reach all parts of the body?

7. How does alcohol in the blood affect the brain?

8. When does the heart rest?

9. How does exercise in the fresh air help the heart?

10. What harm does alcohol do to the heart?

CHAPTER XV.

THE LUNGS.

[Ill.u.s.tration: T]HE blood flows all through the body, carrying good food to every part. It also gathers up from every part the worn-out matter that can no longer be used. By the time it is ready to be sent back by the veins, the blood is no longer pure and red. It is dull and bluish in color, because it is full of impurities.

If you look at the veins in your wrist, you will see that they look blue.

If all this bad blood goes back to the heart, will the heart have to pump out bad blood next time? No, for the heart has neighbors very near at hand, ready to change the bad blood to pure, red blood again.

THE LUNGS.

These neighbors are the lungs. They are in the chest on each side of the heart. When you breathe, their little air-cells swell out, or expand, to take in the air. Then they contract again, and the air pa.s.ses out through your mouth or nose. The lungs must have plenty of fresh air, and plenty of room to work in.

[Ill.u.s.tration: _The lungs, heart, and air-pa.s.sages._]

If your clothes are too tight and the lungs do not have room to expand, they can not take in so much air as they should. Then the blood can not be made pure, and the whole body will suffer.

For every good breath of fresh air, the lungs take in, they send out one of impure air.

In this way, by taking out what is bad, they prepare the blood to go back to the heart pure and red, and to be pumped out through the body again.

How the lungs can use the fresh air for doing this good work, you can not yet understand. By and by, when you are older, you will learn more about it.

CARE OF THE LUNGS.

Do the lungs ever rest?

You never stop breathing, not even in the night. But if you watch your own breathing you will notice a little pause between the breaths. Each pause is a rest. But the lungs are very steady workers, both by night and by day. The least we can do for them, is to give them fresh air and plenty of room to work in.

You may say: "We can't give them more room than they have. They are shut up in our chests."

I have seen people who wore such tight clothes that their lungs did not have room to take a full breath. If any part of the lungs can not expand, it will become useless. If your lungs can not take in air enough to purify the blood, you can not be so well and strong as G.o.d intended, and your life will be shortened.

If some one was sewing for you, you would not think of shutting her up in a little place where she could not move her hands freely. The lungs are breathing for you, and need room enough to do their work.

THE AIR.

The lungs breathe out the waste matter that they have taken from the blood. This waste matter poisons the air. If we should close all the doors and windows, and the fireplace or opening into the chimney, and leave not even a crack by which the fresh air could come in, we would die simply from staying in such a room. The lungs could not do their work for the blood, and the blood could not do its work for the body.

Impure air-will poison you. You should not breathe it. If your head aches, and you feel dull and sleepy from being in a close room, a run in the fresh air will make you feel better.