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. The person may then bleed to death. It is very unwise to overtax
the heart in any way, for it may be strained or otherwise injured, so
that it can never again do its work properly.

~3. Effects of Bad Air.~--Bad air is very harmful to the heart and to
the blood also. We should always remember that the blood of the body
while passing through the lungs is exposed to the air which we breathe.
If the air is impure, the blood will be poisoned. In churches and in
other places where the air becomes foul, people often faint from the