needed is a little knowledge and a firm purpose. Whoever allows himself to be shaped by undesirable habits of muscle and bone will have cause for keen regret in later years. But he who, in his youth, controls his habits and shapes his body with care, will never regret it. Four rules will help:

1. Do not sit day after day in the same twisted position. When you have been seated in one way for a while, then change and sit in some other way.

2. Do not carry a heavy weight of books on the same arm back and forth from school every day. Carry as few books as possible on either arm, and let each arm do its share of the work.

NOTICE HIS SHOULDERS

If this position becomes a habit, the boy will have a

crooked body when he is

a man

3. Do not carry a baby brother or sister on the same hip every day. The weight just there will tend to give a wrong twist both to your back and to his.

4. If you must stand for hours at a stretch, learn to rest one leg by using the other. Don't let one side sag down from habit. Change sides.

CHAPTER III

MUSCLES CONTRACTING AND STRETCHING

The coal heaver round the corner has a superb set of muscles over the working part of his back. They are so well developed that, as he stands bent over his work, it

BENT BY HIS WORK

is evident that these muscles give him a back of tremendous strength. By their help he shovels coal for hours at a time through the days and the weeks of the year. Moreover, when he has finished his day's work he does not seem overtired. He is still ready for his joke and his laugh with his children at home. He even jokes at the expense of his own back, for although it is so well developed and so tire

less, still the man himself frankly acknowledges that it is sadly bent, and that by no effort on his part can he stand straight or walk as would please him best. He says that that is the price he has had to pay for the

kind of work he has chosen as a life occupation. More people have round shoulders developed in some such way than are troubled with any kind of lateral curvature of the spine.

A bicycle rider whom I know has a back quite as bent, although from a different cause. It is muscular, strong and efficient, but it never looks well except when he is working his legs fast on his wheel. It is bent from the position it has been allowed to take, rather than from the work it has done in that position.

Something must be wrong, however, and we wonder what it is. Here are these men and multitudes of others whose backs are splendidly developed, but who are so bent as to look almost deformed. For years no one could entirely explain the cause of the combination-the strong but bent back. At last, however, close observation and logical reasoning have made the case clear. I give the explanation in the fewest words possible. The value of this explanation will be measured for us by the use we make of the law:

BENT BY BICYCLING

Muscles stay in the position in which they do their heaviest work.

A man of my acquaintance who travels a good deal, says that when, for a few weeks, he carries his suit case persistently with the same hand, that shoulder becomes an inch or an inch and a half lower than the other, while, at the same time it becomes stronger. This shows how a muscle can be lengthened even while it is being strengthened.

Stretch a muscle out and work it hard, as a coal heaver does when he curves his back over for the shoveling and the lifting of the coal, and those muscles, being obliged to work hard, even while they are stretched, will gain their strength in that position and will stay elongated even when they are not at work. Let their size and their strength increase while they are stretched and you have given them their permanent shape.

Two oarsmen illustrate this law in opposite ways. One does all his hardest rowing with a straight back, the other with a back that is curved. Their work continues day after day until each back is as strong and as muscular as the other. But see what the results are. One man walks as if he had spent his boyhood curved over a school desk without a thought about what might be happening to his spine. The other man looks as if he might have spent those same years at West Point with officers and fellow-students who compelled him to stand

straight whether he wished to or not. Yet the boyhood of the two men may have been the same. Indeed, the difference just now lies entirely with the two positions in which they did their rowing. Their muscles, when they walk, simply betray some facts about their recent history.

Look at the hand of a piano

player, it is open because he al

ways exercises it hard in that position; and the hand of the oarsman, - see how his fingers curl up as if they were ready to grasp his oar even when it is not in sight. An oarsman's hand tells the story about his occupation.

From the man who digs to earn his daily bread on the farm or in the coal mine, to the man who climbs a mast and risks his life in

BENT BY AGE

the tempest, through each occupation of life the muscles of the body are called upon to do their hardest work in special positions. And it sometimes seems as if numberless human beings would have to submit to their fate and accept muscles which their work has forced on them; for after a man has chosen his life work he cannot leave it simply because he objects to the shape which it is giving to his body.