6. Which muscles are the weakest, and which are the strongest?

7. What is necessary if you would have strong and healthy muscles?

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CLASSES AND WORK OF THE MUSCLES.

The muscles are divided into two great classes: those which we may move as
we choose, called _voluntary_ muscles, and those over which we have no
power, called _involuntary_ muscles.

Some muscles support and move the various parts of the body, others have
different work to do. The heart, the great involuntary muscle, acts like an
engine to drive the blood throughout the body; the lungs draw in and throw
out the air in breathing; the stomach helps to churn and change food into
blood; the tongue is used in speaking and eating.

* * * * *

QUESTIONS ON THE MUSCLES.

What are the muscles?--"The lean flesh of the body; bands and bundles of
fleshy threads which cover the body."

Of what use are the muscles to the body?--"They cover the bones; they
support and move the bones and different parts of the body."

Name some parts of the body which are made of muscles.--"The eyeballs, the