y 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 vertebrae 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.

*School Furniture.*--It has long been observed that school children are
more subject to curvature of the spine and other deformities of the
skeleton than the children who do not attend school. While this is due
largely to faulty positions assumed by the pupils at their work, it has
been suggested that the school