Questions. 1. Why should you chew your food thoroughly? 2. Why is it necessary to have baby teeth? 3. How are teeth easily broken? 4. Why do teeth decay? 5. What must you avoid in order to protect your teeth? 6. How should your teeth be brushed? 7. Why should you have your teeth examined twice each year by a dentist?
Remember. 1. Take care of your teeth and they will last you as long as you live. 2. Do not pick them with pins, or toothpicks of any kind. 3. Do not use them for nutcrackers or wire-cutters. 4. Do not use them for tack pullers. 5. Keep them clean at all times. 6. Brush them up and down as well as crosswise.
[CHAPTER XI]
NECESSITY FOR PURE AIR AND HOW TO SECURE IT
We have learned how the cells of the body are killed by starvation. Now let us learn how they are choked to death, or killed by lack of air.
How air is changed in the body
The cells of the body need oxygen, and the only way we can give it to them is by means of air. Every time we take air into our lungs we are giving oxygen to the red corpuscles or cells in the blood, which distribute it to the other cells in the body. The air that goes into our lungs, if it is fresh and pure, contains a great deal of oxygen and a very little of another gas called carbon dioxid. The air that comes out of the lungs contains a very little oxygen and a great deal of carbon dioxid. The blood not only takes the oxygen out of the air, but gives carbon dioxid to the air. This carbon dioxid is very poisonous, and would kill the cells if it remained in the blood; hence we should never breathe the same air twice. There is no lack of fresh air in the world, and no excuse for anyone's ever breathing air that is not pure.
Effects of impure air