*How the Skeleton becomes Deformed*—We are accustomed to look upon the skeleton as a rigid framework which can get out of its natural form only through severe strain or by violence. This view is far from being correct. On account of their necessary freedom of motion, the bones, especially those of the spinal column, are easily slipped from their normal positions; and where improper attitudes are frequently assumed, or continued through long periods of time, the skeleton gradually becomes deformed (Fig. 104). For example, the habit of always sleeping on the same side with a high pillow may develop a bad crook in the neck; and the ugly curves, assumed so frequently in writing (80) (Fig. 105), and also in standing, when the weight is shifted too much on one foot, may become permanent. Then the habit of reclining in a chair with the hips resting on the front of the seat often deforms the back and causes a drooping of the shoulders. In fact, slight displacements of the vertebræ come about so easily _through incorrect positions_, that they may almost be said to "occur of themselves" where active measures are not taken to preserve the natural form of the body. The very few people who have perfectly formed bodies show to what an extent has been overlooked an essential law of hygiene. *Prevention of Skeletal Deformities.*—Those deformities of the skeleton that are acquired through improper positions are prevented by giving sufficient attention to the positions assumed in sitting, standing, and sleeping, and also to the posture in various kinds of work. In sitting the trunk should be erect and the hips should touch the back of the chair. One should not lounge in the ordinary chair. In standing the body should be erect, the shoulders back and down, the chest pushed slightly up and forward, and the chin slightly depressed, while the weight should, as a rule, rest about equally on the two feet. The habit of leaning against some object when standing (the pupil in reciting often leans on his desk) should be avoided. In sleeping the pillow should be of the right thickness to support the head on a level with the spinal column and should not be too soft. If one sleeps on his back, no pillow is required. It is best not to acquire the habit of sleeping always on the same side. Where one is compelled by his work to assume harmful positions, these should be corrected by proper exercises, and by cultivating opposing positions during the leisure hours. Much is to be accomplished through those forms of physical exercise which develop the muscles whose work it is to keep the body in an upright position.