2.  Bones of Children.—­Sometimes little children try to walk before the bones have become hard enough to support the weight of the body.  This causes the legs to become crooked.  In some countries young children work in factories and at various trades.  This is wrong, because it dwarfs their growth, and makes them puny and sickly.

3.  Improper Positions.—­The bones are so soft and flexible when we are young that they are very easily bent out of shape if we allow ourselves to take improper positions in sitting, lying, or standing.  This is the way in which flat and hollow chests, uneven shoulders, curved spines, and many other deformities are caused.

[Illustration:  IMPROPER POSITION.]

4. In sitting, standing, and walking, we should always take care to keep the shoulders well back and the chest well expanded, so that we may not grow misshapen and deformed.  Many boys and girls have ugly curves in their backbones which have been caused by sitting at high desks with one elbow on the desk, thus raising the shoulder of that side so high that the spine becomes crooked.  The illustrations on this and the following page show good and bad positions and also the effects of bad positions.

[Illustration:  PROPER POSITION.]

5.  Seats and Desks.—­The seats and desks of school-children should be of proper height.  The seats should be low enough to allow the feet to rest easily upon the floor, but not too low.  The desk should be of such a height that, in writing, one shoulder will not be raised above the other.  If a young person bends the body forward, he will, after a time, become round-shouldered and his chest will become so flattened that the lungs cannot be well expanded.

[Illustration:  DESK TOO HIGH.]

6. Standing on one foot, sitting bent forward when reading or at work, sleeping with the head raised high upon a thick pillow or bolster, are ways in which young persons often grow out of shape.

[Illustration:  SEAT TOO HIGH.]

7.  The Clothing.—­Wearing the clothing tight about the waist often produces serious deformities of the bones of the trunk, and makes the chest so small that the lungs have not room to act properly.  Tight or high-heeled shoes also often deform and injure the feet and make the gait stiff and awkward.

8.  Broken Bones.—­By rough play or by accident the bones may be broken in two just as you might break a stick.  If the broken parts are placed right, Nature will cement them together and make the bone strong again; but sometimes the bones do not unite, and sometimes they grow together out of proper shape, so that permanent injury is done.

9.  Sprains.—­In a similar manner the ligaments which hold the bones together, in a joint, are sometimes torn or over-stretched.  Such an accident is called a sprain.  A sprain is a very painful accident, and a joint injured in this way needs to rest quite a long time so that the torn ligaments may grow together.