CHAPTER XX.
THE MUSCLES AND HOW WE USE THEM.
1. The Muscles.—Where do people obtain the beefsteak and the mutton-chops which they eat for breakfast? From the butcher, you will say; and the butcher gets them from the sheep and cattle which he kills. If you will clasp your arm you will notice that the bones are covered by a soft substance, the flesh. When the skin of an animal has been taken off, we can see that some of the flesh is white or yellow and some of it is red. The white or yellow flesh is fat. The red flesh is lean meat, and it is composed of muscles.
2. The Number of Muscles.—We have about five hundred different muscles in the body. They are arranged in such a way as to cover the bones and make the body round and beautiful. They are of different forms and sizes.
3. With a very few exceptions the muscles are arranged in pairs; that is, we have two alike of each form and size, one for each side of the body.
4. How a Muscle is Formed.—If you will examine a piece of corned or salted beef which has been well boiled, you will notice that it seems to be made up of bundles of small fibres or threads of flesh. With a little care you can pick one of the small fibres into fine threads. Now, if you look at one of these under a microscope you find that it is made of still finer fibres, which are much smaller than the threads of a spider's web. One of these smallest threads is called a muscular fibre. Many thousands of muscular fibres are required to make a muscle.
MUSCULAR
FIBRES.