of the skeleton is the proper _adjustment_
of its parts. The efficiency of any of the body machines is impaired by
lack of proper adjustment. Not only this, but because of the fact that the
skeleton forms the groundwork of the whole body--muscles, blood vessels,
nerves, everything in fact, being arranged with reference to it--any lack
of proper adjustment of the bones interferes generally with the
arrangement and work of tissues and organs. The displaced bones may even
compress blood vessels and nerves and interfere, in this way, with the
nourishment and control of organs remote from the places where the
displacements occur. For these reasons the proper adjustment of the
different parts of the skeleton supplies one of the essential conditions
for preserving the health.

*Hygienic Importance of the Spinal Column.*--What has been said about the
adjustment of the skeleton in general applies with particular force to the
spinal column. The spinal column serves both as the central axis of the
body and as the container of the spinal cord. Thirty-one pairs of nerves
pass between the vertebrae to connect the spinal cord with different parts
of the body, and two important arteries (the vertebral) pass through a
series of small openings in the bones of the neck to reach the brain.
Unnatural curves of the spine throw different parts of the body out of
their natural positions, diminish the thoracic and abdominal cavities,
and, according to the belief of certain physicians, compress the nerves
that pass from the cord to other parts of the body. Slightly misplaced
vertebrae in the neck, by compressing the vertebral arteries, may also
interfere with the supply of blood

[Fig. 104]

Fig. 104--A tendency toward spinal curvature (after Mosher)

[Fig. 105]

Fig. 105--Effect on spinal column of improper position in writing. (From
Pyle's _Personal Hygiene._)

*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 graduall