color of the blood changes from purple to bright red.

12. Plants purify the air by removing the carbonic-acid gas.

13. Alcohol and tobacco injure the blood corpuscles so that they cannot
take up the oxygen from the air which the lungs receive.




CHAPTER XIV.

HOW TO KEEP THE LUNGS HEALTHY.


~1. Pure Air Necessary.~--A person may go without eating for a month, or
without drinking for several days, and still live; but a strong man will
die in a few moments if deprived of air. It is very important that we
breathe plenty of pure air. There are many ways in which the air becomes
impure.

~2. Bad Odors.~--Anything which rots or decays will in so doing produce
an unpleasant odor. Bad odors produced in this way are very harmful and
likely to make us sick. Many people have rotting potatoes and other
vegetables in their cellars, and swill barrels, and heaps of refuse in
their back yards. These are all dangerous to health, and often give rise
to very serious disease. We should always remember that bad odors caused
by decaying substances are signs of danger to health and life, and that
these substances should be removed from us, or we should get away from
them, as soon as possible.