icker, as may be felt by placing
the fingers on it. Although it shortens only two inches it is fastened
to the bone so near the elbow that it draws the hand up two feet.

PRACTICAL QUESTIONS

1. Of what use are the bones?

2. What animals have bony skeletons?

3. What can you say of the form of bones?

4. How many bones in the body?

5. Name six bones.

6. What part of the arm has two bones side by side?

7. How many ribs have you?

8. Explain how a broken bone should be cared for.

9. Point out and name two kinds of joints.

10. What are ligaments?

11. Of what is a muscle made?

12. How many muscles in the body?

13. How many tendons can you feel in your wrist?

CHAPTER XIX

THE MUSCLES AND HEALTH

=Making the Muscles Strong.=--No persons use all of the five hundred
muscles in the body every day. In slow walking only about twenty
muscles are used, while in running more than four times that number
are called into action. Muscles which are not used get lazy and weak.

Every time a muscle is made to act the blood vessels enlarge and bring
to it more blood to supply food. The more food the muscle has the
stronger it grows. The right arm is used more than the left in most
persons. This makes it so much stronger that some boys can lift
twenty-five pounds more with the right arm than they can with the left.

=Using the Muscles keeps the Body Well.=--All muscles must have more
blood when they are used so that the heart is made to beat faster and
stronger by exercise. In this way its valves and walls become able to
do more work. Such a heart not only does its work better in a well
person, but is able to keep pumping when the body is weakened by
disease. Many persons die because the heart gets too weak to push the
blood through the body.

In all the little spaces between the muscles and parts of other organs
is some watery part of the blood containing much waste given off from
the tissues. Moving the muscles presses on this watery waste in such a
way as to move it along into the blood channels. It then can be cast out
of the body by the lungs and other organs. One reason why we feel so
good after exercise is because the poisonous waste has been taken away.

No one can remain well very long without taking exercise. Children as
well as older persons should enjoy one or two hours of outdoor play
every day.

[Illustration: FIG. 85.--