How The Parts Of Our Body Move
( Originally Published 1920 )
The Muscles and How They Do Their Work.—You have learned in Chapter II that the organs which move the different parts of the body are called muscles. You have learned, too, that a muscle is joined to two bones or other hard parts of the body, and that when the muscle shortens, it brings nearer together the two parts to which it is fastened.
Suppose that you have a short but very wide and strong rubber band, and that you fasten it at one end to a shutter and at the other end to the wall of the house. The band would shorten and pull the shutter in toward the wall. This is an illustration of the general way in which a muscle acts. The rubber band, how-ever, would pull on the shutter all the time, while our muscles shorten and pull only when it is necessary that some movement should take place.
The way in which the muscle bends the arm at the elbow is shown in Fig. 20. , This big muscle, which is called the biceps muscle, runs from the shoulder down the length of the upper arm and is fastened to the upper part of the forearm just below the elbow. The muscle is shaped like a spindle, and when the arm is straight, it is stretched out and loose. When you bend your arm, it becomes short and thick, as an elastic band does when it shortens or contracts. Since the ends of the muscle are fixed to the shoulder and the forearm, this shortening tends to pull the bone in the fore-arm toward the shoulder. Press your left hand tightly on the upper part of your right arm. Bend your right arm slowly up, and if you have well-developed muscles, you can feel the biceps muscle thicken and swell up.
The muscles are in many cases fastened to the bones, or other parts which they move, by strong bands called tendons.— In the drumstick of a chicken you can see the tough whitish tendons which connect the muscle with the bone at its lower end; and the meat of the drumstick above, like all other kinds of lean meat that we eat, is the muscle itself.
Different Kinds of Muscles.—There are hundreds of different muscles in the body, and all together they make up about half its weight. They differ very much among themselves in shape and size, according to the special work they have to do. The legs and the arms are almost solid masses of muscle, except for the bones inside, while the trunk is enclosed back and front in great sheets of muscle.
The muscles in the legs by which we make the movements of running and walking are large and powerful, but the biggest muscles of all are the ones in the back which men use when they lift heavy weights. One of these back muscles weighs several pounds.
Every flickering of an eyelid and every change in the expression of the face is brought about by the contraction of tiny muscles in the skin.
Our Unseen Servants.—Once upon a time there was a little girl who had an illness which lasted for years and kept her in bed so that she could not go out and play with other children. Her parents were wealthy, and she had everything that money could buy; but she never left her room and she rarely saw any one but her mother and her father and her nurse.
At last the doctor who was caring for this little girl succeeded in curing 'her so that she could walk about and was gaining strength every day. When she was allowed to come downstairs, you can imagine how interesting and exciting it was, after she had spent all those years in one room. You can imagine, too, how many surprising things she saw, things that would seem very natural to you, but to her were new and strange. One of these surprises came when she passed through a door into a room containing a big black stove, with steam coming out of some pots which a tall, cheerful woman was stirring.
"Excuse me," said the child, "but what is this room and who are you?"
"This is the kitchen," replied the woman with a smile, "and I am the cook who prepares all your meals."
Just then a man with a big shovel walked through the kitchen. "Who is that?" 'whispered the child.
"That is the choreman who is going to attend to the furnace so that you may be all snug and warm upstairs."
There was a ring at the doorbell and a boy handed in some meat from the butcher's for dinner; and another left some tea and sugar; and another, some of the little girl's clothes from the laundry, all smooth and white.
She went upstairs to her mother, with her eyes shining with excitement, and cried out, "Oh, Mother, I never thought where all the things came from that I had in my little room upstairs. All the time the cook and the choreman and the butcher's boy and the grocer's boy were working for me, so that I might have all the things I needed."
Are not the muscles and other organs of the body somewhat like the cook and the choreman in this little girl's house, faithful servants working for us all the time without our realizing how much their service means? You can feel your biceps muscle as it bends the elbow. You can think of the movements of many other parts of the body which the muscles bring about, and which they accomplish for you when you wish it. There are a great many other muscles, however, which work for you without any effort of your will at all; muscles whose action you could not stop even if you tried. The muscles used in breathing, for instance, contract about twenty times a minute, day and night, sleeping or waking, day after day, week after week, year after year. There are muscles in the walls of the blood vessels, muscles in the walls of the stomach, and in many other organs of the body. They are all necessary for the working of our body-machine, and, like the little girl who had been ill, we should be very grateful that we have such faithful servants to do all that is necessary for our good.
Strong Men of Old Times and of To-day.--In old times the Greeks used to tell many beautiful stories about great men with much more wisdom and power than real people have to-day. One of these great men, who was said to have done mighty deeds upon the earth, was named Hercules. According to the story, he was so strong that he could kill a lion with his hands. His most famous feat, however, was the securing of some wonderful apples made of gold. He traveled into far-off countries in search of these golden apples and at last found that the one person who could get them for him was the mighty giant Atlas. The Greek legend says that Atlas stood at the end of the earth with his feet in a forest and his head in the clouds, holding up the sky on his shoulders. Atlas was quite willing to get the apples, but what was to be done about the sky?
Why, Hercules could hold it on his own great shoulders, to be sure, while the giant strode over land and sea to the Garden of the Hesperides, where the apples were to be found. So it was arranged; and although Hercules tottered a little and shook down a few stars, he held up the sky safely till Atlas came back. How Atlas was inclined to take a little vacation and leave Hercules in his place, and how Hercules got the sky off his own shoulders and on the giant's again, you must read some day in a charming book by Nathaniel Hawthorne called Tanglewood Tales.
It is not only the Greeks who were fond of tales of strong men like Hercules. The peoples of Northern Europe had a god called Thor (from whom our Thursday or Thor's day is named), who did great deeds, killing evil beasts and bad giants with a mighty hammer. All nations have had their old-time heroes, men of strength and courage; and they were right in admiring them and telling about their doings so as to make other people want to be like them.
There are no giants and not many lions to be killed in our world to-day. There is, however, plenty of work to be done, which needs strength almost like that of Hercules and which is more useful to the world than the finding of golden apples. In war time men must still be ready to defend their country; and in peace there is work to do that is scarcely less important. The coal that is burned to keep us warm in winter, and to run locomotives and drive the machinery in factories, must be dug out of the mines by human muscle. In other mines men are getting out the iron from the earth. In the factories the iron is made into steel—the steel that builds our tall city buildings and our railroads and the great guns for our army. The tall buildings themselves must be built, and the rail-roads must be laid, and when they have been finished, the snorting locomotives must be driven over them, pulling their long trains of cars behind. The men who do these things must be strong in muscle, and they must be brave as well as strong. It is no uncommon thing for the miner or the' railroad engineer or the man who places the steel in a tall building to lose his life from a fall or an accident of some other kind.
How to Grow Strong: Strength of body is a fine thing if it is used, not to bully and take things by force, but to help and defend the weak and to do the heavy work of the world.
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Every boy and girl owes it to our country to be as strong as he or she can, to develop all the muscles so as to be ready to do any work that may come, and ready to help the old and the ill who cannot do for themselves. Some people are naturally stronger than others, but we can all strengthen our muscles by exercise. - When a muscle is unused, it becomes soft and flabby. When it is used, it grows more and more powerful. So by exercising, each one of us can grow stronger and more fit for useful service every day.
Many of us may not be called upon to do work that needs muscular strength and endurance; but we all have some work to do in the world, and success in any kind of work depends on being well. Exercising the muscles not only strengthens the muscles themselves but helps all the other parts of the body. When you run a -race or take some other active exercise, you breathe more deeply, your heart beats faster, the blood flows more swiftly through the different organs, and after exercise your appetite is better and your sleep is sounder. Exercise is essential, then, not only for strength but also for the health of the body as a whole.
Good Kinds of Exercise.—Roller skating, bicycle riding, ice skating and coasting in winter, baseball, prisoners' base, and all sorts of running games, swimming, climbing trees, and long walks—these are the things that make the muscles grow strong and the cheeks rosy, and that keep the heart and the lungs in good condition.
Above all, games that children can play together are good. Such games, in which one team challenges an-other team, not only develop physical strength but also teach you how to do your best, not for yourself but for the team, and to work side by side with others for a common end. Some one once said that the victory of Waterloo, the great battle in which the English defeated Napoleon, was won on the playing fields of Eton (a famous school where most of the English officers had studied when they were boys).
Keeping in Training.—If we want to be strong and well, we must not only do all we can to develop our bodies by exercise, but we must also avoid anything that will directly harm them. There are many bad habits which may injure the health. Sitting up too late at night, eating too much or too little, and nibbling at candy between meals are examples of habits formed by children which have injurious effects upon the health and strength. As you grow- older, you will learn that among grown people there is one habit of this kind that is more harmful than perhaps any other—the use of what are known as alcoholic drinks, such as whiskey, brandy, wine, ale, and beer. These drinks all contain a poison called alcohol, some of them having only a little of it, and others a great deal.
People who use alcoholic drinks are sure to be poisoned by them. It is important for every one to remember that the use of even a slight amount of alcohol makes people less able to do physical and mental work. Studies made by scientific men in recent years have proved this. Therefore, men who played football or rowed at college were never allowed to use alcoholic drinks even before the days of prohibition. As soon as our country entered the World War in 1917, it was made illegal to serve drinks to any soldier or sailor in the uniform of the United States.
We can be sure that what is bad for the athlete is bad for everyone else, and the safest rule for those who would keep strong and well is to use no drinks of this kind at any time.