They are made of a kind of bone covered with a hard smooth enamel (ĕn ăm´el). If the enamel is broken, the teeth soon decay and ache, for each tooth is furnished with a nerve that very quickly feels pain.
CARE OF THE TEETH.
Cracking nuts with the teeth, or even biting thread, is apt to break the enamel; and when once broken, you will wish in vain to have it mended. The dentist can fill a hole in the tooth; but he can not cover the tooth with new enamel.
Bits of food should be carefully picked from between the teeth with a tooth-pick of quill or wood, never with a pin or other hard and sharp thing which might break the enamel.
The teeth must also be well brushed. Nothing but perfect cleanliness will keep them in good order. Always brush them before breakfast. Your breakfast will taste all the better for it. Brush them at night before you go to bed, lest some food should be decaying in your mouth during the night.
Take care of these cutters and grinders, that they may not decay, and so be unable to do their work well.
THE CHEST AND ABDOMEN.
You have learned about the twenty-four little bones in the spine, and the ribs that curve around from the spine to the front, or breast-bone.
These bones, with the shoulder-blades and the collar-bones, form a bony case or box.
In it are some of the most useful organs of the body.