Questions.—By what is all motion in the body made? What do the muscles move? Explain how the muscles move things. Tell about the two muscles of the arm in the figure. What is said about the swelling out of the muscles as they shorten? What is the meat of animals? What is said about the color of muscles in different animals? What is said of the muscles in the arm below the elbow? What is said of the wrist? What of the muscles in the hand? Why are most of the muscles that move the fingers put up in the arm? What is said about the drum-stick of a fowl? What is said about the muscles of the toes? What about the ligaments of the tendons at the wrist and ankle? What is said of the shapes of muscles? What of their sizes? What are the smallest muscles in the body? What is said about the muscles of birds used in flying and those used in singing?
CHAPTER XVIII.
MORE ABOUT THE MUSCLES.
Number of muscles in the body.
There is a great number of muscles in the whole body to produce all its motions. There are about fifty in each arm and hand. In the whole body there are about four hundred and fifty, and each muscle is made up of a great number of fibres or threads, every fibre having its own work to do.
All connected with the brain by nerves.
Now all these muscles have nerves that connect them with the brain, and the mind tells them by these nerves just what to do. Each muscle has a great many little nervous ends scattered through it every where. The message from the mind that tells the muscle to act does not go to the whole muscle as one thing, as a message is sent to a person. It goes to each fibre of it, telling that fibre what to do. Every fibre of the muscle has its little nervous tube connecting it with the brain, for the nerves are bundles of tubes, just as the muscles are bundles of fibres. And each fibre gets its messages from the mind separate from all the other fibres by its own tube, so that each fibre is a workman by itself. How well these workmen pull together when they all get a message from your mind by their telegraphic tubes!
The endless variety of messages sent from the brain to the muscles.
Commonly it takes several muscles to make any motion, and sometimes many muscles act together. When this is so, messages are sent to a great multitude of fibres in these many muscles. Think of this. Raise your hand. It is not one muscle that does this, but many. Your mind has sent a message to all the fibres of these muscles, and they have all done their part in raising your hand. But now raise it again a little differently. A different message for this has been sent to all the fibres; and so for all the different motions there are different messages. It does not seem possible that so many different messages should be sent through the nerves to the fibres of all the muscles, and that these fibres should obey them so perfectly.
This is wonderful even in so simple a motion as raising the hand; but how much more wonderful when a great variety of rapid motions are made by the muscles, as in playing on a piano! How busy is the mind of the player in sending its messages, one after the other, to the multitudes of muscular fibres that work the arms and the fingers! And if he sings at the same time that he plays, his mind is sending messages also to the muscles of the chest, and throat, and mouth. And what adds greatly to the wonder is, that all this time that the mind is sending out so many messages, it is receiving messages from the senses. Messages are going from the sounds of the piano and the voice along the nerves of the ear to the mind. They go also from the tips of the busy fingers as they press the keys. How wonderful that all these messages are going back and forth so rapidly, and the mind in the brain manages them without any confusion!