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.
The good, pure air makes your blood pure; and the blood then flows quickly through your whole body and refreshes every part.
We must be careful not to stay in close rooms in the day-time, nor sleep in close rooms at night. We must not keep out the fresh air that our bodies so much need.
It is better to breathe through the nose than through the mouth. You can soon learn to do so, if you try to keep your mouth shut when walking or running.
If you keep the mouth shut and breathe through the nose, the little hairs on the inside of the nose will catch the dust or other impurities that are floating in the air, and so save their going to the lungs. You will get out of breath less quickly when running if you keep your mouth shut.
DOES ALCOHOL DO ANY HARM TO THE LUNGS?
The little air-cells of the lungs have very delicate muscular (mŭs´ku lar) walls. Every time we breathe, these walls have to move. The muscles of the chest must also move, as you can all notice in yourselves, as you breathe.
All this muscular work, as well as that of the stomach and heart, is directed by the nerves.