As you study your own bodies to-day, you will find that you each have better joints than any dolls that can be bought at a toy shop.

HINGE-JOINTS.

Some of your joints work like the hinges of a door, and these are called hinge-joints.

You can find them in your elbows, knees, fingers, and toes.

How many hinge-joints can you find?

Think how many hinges must be used by the boy who takes off his hat and makes a polite bow to his teacher, when she meets him on the street.

How many hinges do you use in running up-stairs, opening the door, buttoning your coat or your boots, playing ball or digging in your garden?

You see that we use these hinges nearly all the time. We could not do without them.

BALL AND SOCKET JOINTS.

All our joints are not hinge-joints.

Your shoulder has a joint that lets your arm swing round and round, as well as move up and down.

Your hip has another that lets your leg move in much the same way.

This kind of joint is the round end or ball of a long bone, which moves in a hole, called a socket.

Your joints do not creak or get out of order, as those of doors and gates sometimes do. A soft, smooth fluid, much like the white of an egg, keeps them moist and makes them work easily.

BONES.

What parts of our bodies are jointed together so nicely? Our bones.

How many bones have we?

If you should count all your bones, you would find that each of you has about two hundred.

Some are large; and some, very small.

There are long-hones in your legs and arms, and many short ones in your fingers and toes. The backbone is called the spine.

If you look at the backbone of a fish, you can see that it is made up-of many little bones. Your own spine is formed in much the same way, of twenty-four small bones. An elastic cushion of gristle (gris’l) fits nicely in between each little bone and the next.

When you bend, these cushions are pressed together on one side and stretched on the other. They settle back into their first shape, as soon as you stand straight again.

If you ever rode in a wheelbarrow, or a cart without springs, you know what a jolting it gave you. These little spring cushions keep you from being shaken even more severely every time you move.

Twenty-four ribs, twelve on each side, curve around from the spine to the front, or breast, bone.

They are so covered with flesh that perhaps you can not feel and count them; but they are there.

Then you have two flat shoulder-blades, and two collar-bones that almost meet in front, just where your collar fastens.

Of what are the bones made?

Take two little bones, such as those from the legs or wings of a chicken, put one of them into the fire, when it is not very hot, and leave it there two or three hours. Soak the other bone in some weak muriatic (mu ri atik) acid. This acid can be bought of any druggist.

You will have to be careful in taking the bone out of the fire, for it is all ready to break. If you strike it a quick blow, it will crumble to dust. This dust we call lime, and it is very much like the lime from which the mason makes mortar.

The acid has taken the lime from the other bone, so only the part which is not lime is left. You will be surprised to see how easily it will bend. You can twist it and tie it into a knot; but it will not easily break.

You have seen gristle in meat. This soft part of the bone is gristle.

Children’s bones have more gristle than those of older people; so children’s bones bend easily.

I know a lady who has one leg shorter than the other. This makes her lame, and she has to wear a boot with iron supports three or four inches high, in order to walk at all.

One day she told me how she became lame.

“I remember,” she said, “when I was between three and four years old, sitting one day in my high chair at the table, and twisting one foot under the little step of the chair. The next morning I felt lame; but nobody could tell what was the matter. At last, the doctors found out that the trouble all came from that twist. It had gone too far to be cured. Before I had this boot, I could only walk with a crutch.”

CARE OF THE SPINE.

Because the spine is made of little bones with cushions between them, it bends easily, and children sometimes bend it more than they ought.

If you lean over your book or your writing or any other work, the elastic cushions may get so pressed on the inner edge that they do not easily spring back into shape. In this way, you may grow round-shouldered or hump-backed.

This bending over, also cramps the lungs, so that they do not have all the room they need for breathing. While you are young, your bones are easily bent. One shoulder or one hip gets higher than the other, if you stand unevenly. This is more serious, because you are growing, and you may grow crooked before you know it.

Now that you know how soft your bones are, and how easily they bend, you will surely be careful to sit and stand erect. Do not twist your legs, or arms, or shoulders; for you want to grow into straight and graceful men and women, instead of being round-shouldered, or hump-backed, or lame, all your lives.

When people are old, their bones contain more lime, and, therefore, break more easily.

You should be kindly helpful to old people, so that they may not fall, and possibly break their bones.

CARE OF THE FEET.

Healthy children are always out-growing their shoes, and sometimes faster than they wear them out. Tight shoes cause corns and in-growing nails and other sore places on the feet. All of these are very hard to get rid of. No one should wear a shoe that pinches or hurts the foot.

OUGHT A BOY TO USE TOBACCO?

Perhaps some boy will say: “Grown people are always telling us, ’this will do for men, but it is not good for boys.’”

Tobacco is not good for men; but there is a very good reason why it is worse for boys.

If you were going to build a house, would it be wise for you to put into the stone-work of the cellar something that would make it less strong?

Something into the brick-work or the mortar, the wood-work or the nails, the walls or the chimneys, that would make them weak and tottering, instead of strong and steady?

It would he had enough if you should repair your house with poor materials; but surely it must be built in the first place with the best you can get.

You will soon learn that boys and girls are building their bodies, day after day, until at last they reach full size.

Afterward, they must be repaired as fast as they wear out.

It would be foolish to build any part in a way to make it weaker than need be.

Wise doctors have said that the boy who uses tobacco while he is growing, makes every part of his body less strong than it otherwise would be. Even his bones will not grow so well.

Boys who smoke can not become such large, fine-looking men as they would if they did not smoke.

Cigarettes are small, but they are very poisonous. Chewing tobacco is a worse and more filthy habit even than smoking. The frequent spitting it causes is disgusting to others and hurts the health of the chewer. Tobacco in any form is a great enemy to youth. It stunts the growth, hurts the mind, and cripples in every way the boy or girl who uses it.

Not that it does all this to every youth who smokes, but it is always true that no boy of seven to fourteen can begin to smoke or chew and have so fine a body and mind when he is twenty-one years old as he would have had if he had never used tobacco. If you want to be strong and well men and women, do not use tobacco in any form.

REVIEW QUESTIONS.

1. What two kinds of joints have you?

2. Describe each kind.

3. Find as many of each kind as you can.

4. How are the joints kept moist?

5. How many bones are there in your whole body?

6. Count the bones in your hand.

7. Of how many bones is your spine made?

8. Why could you not use it so well if it were all in one piece?

9. What is the use of the little cushions between the bones of the spine?

10. How many ribs have you?

11. Where are they?

12. Where are the shoulder-blades?

13. Where are the collar-bones?

14. What are bones made of?

15. How can we show this?

16. What is the difference between the bones of children and the bones of old people?

17. Why do children’s bones bend easily?

18. Tell the story of the lame lady.

19. What does this story teach you?

20. What happens if you lean over your desk or work?

21. How will this position injure your lungs?

22. What other bones may be injured by wrong positions?

23. Why do old people’s bones break easily?

24. How should the feet be cared for?

25. How does tobacco affect the bones?

26. What do doctors say of its use?

27. What is said about cigarettes?

28. What about chewing tobacco?

29. To whom is tobacco a great enemy? Why?

30. What is always true of its use by youth?