THE MUSCLES.
You are provided by nature with about four hundred muscles. Every one
has its special use. They are fastened to the bones, which can only be
moved by them. The principal muscles are shown in the figure on page 45.
The muscles are generally found in pairs, so that when motion is
produced in one direction, another muscle or group of muscles causes
motion in the opposite direction.
VOLUNTARY AND INVOLUNTARY MUSCLES.
A voluntary muscle is one which you can control; an involuntary muscle
is not subject to your will. Thus, when you move your hand or foot, it
is done by a voluntary muscle. Your heart beats without any will of your
own, and is therefore, controlled by involuntary muscles.
STRENGTH OF MUSCLES.
A well-developed man can drag a little less than his own weight over a
level surface, while a draught-horse can draw only two-thirds. The
horse, therefore, is relatively weaker than man. There are some insects,
however, which are able to move nearly fifty times their own weight.
From what you have learned about the importance of exercise, you will
understand how necessary it is that every muscle should be trained. In
no other way can you preserve sound, rugged health.
HYGIENE OF THE MUSCLES.
When the muscles are properly used, they become large, firm, and dark
red in color. Such use of them causes the skin to act freely, while the
brain is made vigorous and the digestion improved. It is the best
medicine in the world. You must be careful not to strain or overwork
your muscles, as it is very hurtful. Your strength must be built up by
moderate, careful, and regular exercise.
The muscles need not only exercise to make them strong, but a constant
supply of good, pure blood. You must eat wholesome food, in proper
quantities, at regular intervals.
You must take plenty of exercise in the sunlight. The blood and the
muscles demand the light and the heat of the sun to make them strong.
EFFECTS OF EXERCISE.
The effect of exercise upon the muscles may be clearly seen in the arm
of the blacksmith; in the foot and leg of the walker; in the fingers of
the pianist; and in the hand and fore-arm of the skillful penman.
* * * * *
How many muscles have you? How are the bones moved?
How are the muscles generally found? In what manner do they work?
What is a voluntary muscle? An involuntary one? Illustrate the
difference.
Compare the strength of a well-developed man with that of a horse.
What is said of some insects?
Why should the muscles he trained? What is the result?
What kind of medicine is such exercise? How must your strength be
built up?
What do the muscles need beside exercise?
Where should the exercise be taken?
Show some of the effects.