CHAPTER XXI.
HOW TO KEEP THE MUSCLES HEALTHY.
~1.

How to Make the Muscles Strong.~--With which hand can you lift the more?
with the right hand or with the left?
Why do you think you can lift more with the right hand than with the left?
A blacksmith swings a heavy hammer with his right arm, and that arm becomes very large and strong.

If we wish our muscles to grow large and strong, so that our bodies will be healthy and vigorous, we must take plenty of exercise.
~2.

Effects of Idleness.~--If a boy should carry one hand in his pocket all the time, and use only the other hand and arm, the idle arm would become small and weak, while the other would grow large and strong.

Any part of the body which is not used will after a time become weak.