strong; I must sleep, or
change my kind of work or play, to give them rest, when they are tired; I
must breathe pure air, take wholesome food and drink, and live in the
sunlight, to supply them with good blood; I must not weaken them by using
alcohol or tobacco.

* * * * *

QUESTIONS FOR THE FORMULA.

1. Tell about the muscles.

2. How many muscles have you in your body?

3. Of what use are the muscles?

4. How may the muscles be named?

5. Tell about the muscles of the head, trunk, and limbs.

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

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

* * * * *

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
eyelids, the tongue, the heart, the lungs."

What color are the muscles?--"Red."

How do the muscles move the bones?--"By shortening or lengthening
themselves according to the way the bones are to be moved."

Tell how the muscles move your arm at the elbow.--"The muscles in the front
part of the arm shorten themselves, to draw my fore-arm toward the
shoulder; when I wish to stretch out the fore-arm these muscles lengthen,
while another set of muscles shorten, to draw the fore-arm away from the
upper arm."

What do you say about the muscles because they have the power to shorten
and lengthen themselves?--"They are elastic."

About how many muscles are there in your whole body?--"About four hundred
and fifty."

How may these be divided as you study about them?--"