What happens if the enamel is cracked?--"The teeth decay."

Then what must you do to preserve your teeth?--"I must try to keep the
enamel from being cracked or injured in any way."

* * * * *

PART V.

FORMULA FOR DESCRIPTION OF THE BONES.

1. My skull is formed of several bones united, like two saws with their
toothed edges hooked into each other.

2. My spine extends from the base of the skull behind, down the middle of
my back.

It is composed of twenty-four short bones, piled one upon the other, with
cartilage between them.

These bones are fastened together, forming an upright and flexible column,
which makes me erect and graceful.

3. My ribs are curved, strong, and light; there are twenty-four of them,
twelve on each side; they are fastened at the back to my spine, in front to
my breastbone, forming a hollow place for my heart, lungs, and stomach.

4. My shoulder blades are flat, thin, and like a triangle in shape; they
are for my arms to rest upon.