ood and not know it.

WHAT WE HAVE LEARNED

1. We can feel in every part of the body, but mostly in the ends
of the fingers.

2. Light makes a picture upon the nerves inside of the eye.

3. If the eyes ache, the light should be softened or the position
of the book or work changed, or else the eyes should be
rested.

4. Sound in the air goes into the ear and strikes against a drum.
Bones then carry the sound to the ear nerves.

5. Air snuffed up the nose gives the sense of smell. Smell tells
us if the air or food is fit for use.

6. Taste tells us whether food is fit for use. Men can learn to
like the taste of wrong things like tobacco or alcohol.

[Illustration: =The Human Skeleton, showing position of bones.=]

CHAPTER XIV

BONES AND JOINTS

=180.= Bones make the body stiff and strong, and give it shape. Long
bones reach through the arms and legs, and little bones reach down the
fingers and toes. Rounded plates of bone form the head, and a pile of
bony rings makes up the backbone. Each bone is built to fit exactly
into its own place and to do its own work. In all there are over two
hundred bones in the body. They form one seventh of its weight.

=181. Form of bones.=--A bone is not like a solid piece of timber, but
is hollow like the frame of a bicycle. This makes it strong and light.
At its ends a bone is like a hard sponge covered with a firm shell.
This makes it too strong to be easily crushed, and keeps it light.

A bone grows like any other part of the body. It is made of living cells
like woven threads. Lime is mixed among the cells, and makes them stiff
like starch among the threads of a linen collar. Blood tubes go through
every part of the bone so as to feed the cells. The living cells form
one third of the bone, while the lime forms two thirds.

=182. Broken bones.=--Bones are very hard, and yet they can bend a
little without breaking. Most of them are curved a little, and so they
will spring instead of breaking when they are pressed hard. But
sometimes they break. Then a person must wear a splint and bandage to
keep the bones in place until they grow together again. The living
cells will mend a bone in about a month.

An old person's bones are more tender than a child's, and will not
spring much without breaking. An old man is afraid of falling and
breaking his bones, while a child falls a do