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 God 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.