Fig. 5 —On the left are shown the branching tubes which carry blood to all parts of the body; on the right are the brain, spinal cord, and nerves which direct the work of the organs.
The entire body is composed of several hundred organs. Each of them is formed of several kinds of materials named tissue. A skinlike tissue makes up the lining of the stomach, while its outside is made of muscular tissue. The smallest parts of a tissue are little bodies named cells, and very fine threads called fibers.
Growth of the Body.—The body grows rapidly in childhood and more slowly after the sixteenth year, but it continues to get larger until about the twenty-fifth year of age. Some children always grow slowly, have weak bones, and frail bodies. This is generally so because they have poor food or do not chew it well, and get too little fresh air, sunshine, and sleep.
The use of beer, wine, or tobacco may hinder the body from using food for growth, or they may poison the body so that it will never be large and strong. The body should grow about a hundred pounds in weight during the first thirteen years of life. Whether children grow little or much generally depends on the food they give their bodies.
PRACTICAL QUESTIONS
1. Point out and name four parts of the body.
2. Name the two parts of the trunk.
3. What does the chest contain?
4. What is muscle?
5. How is the body fed?
6. Give three parts taking waste out of the body.
7. Of what use are the brain and nerves?
8. Name two organs.
9. How long does the body continue to grow?
10. Why are some children weak and of slow growth?