CHAPTER XI.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 page45.
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.
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 theimportance 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.
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 supplyof 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.
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.