CHAPTER XII.
HOW TO KEEP THE HEART AND THE BLOOD HEALTHY.
~1.~ The heart is one of the most important of all the organs of the body.

If we take good care of it, it will do good service for us during a long life.

Let us notice some ways in which the heart is likely to be injured.
~2.

Violent Exercise.~--Did you ever run so hard that you were out of breath?
Do you know why you had to breathe so fast?
It was because the violent exercise made your heart beat so rapidly that the blood could not get out of the lungs as fast as the heart forced it in.

The lungs became so filled with blood that they could not do their work well.
Sometimes, when a person runs very fast or takes any kind of violent exercise, the lungs become so filled with blood that a blood-vessel is broken.