III. Sternum.

IV. Two Hip Bones.

V. Hyoid Bone.

37. The Spinal Column. The spinal column, or backbone, is a
marvelous piece of mechanism, combining offices which nothing short of
perfection in adaptation and arrangement could enable it to perform. It is
the central structure to which all the other parts of the skeleton are
adapted. It consists of numerous separate bones, called vertebræ. The
seven upper ones belong to the neck, and are called cervical
vertebræ. The next twelve are the dorsal vertebræ; these belong to
the back and support the ribs. The remaining five belong to the loins, and
are called lumbar vertebræ. On looking at the diagram of the backbone
(Fig. 9) it will be seen that the vertebræ increase in size and strength
downward, because of the greater burden they have to bear, thus clearly
indicating that an erect position is the one natural to man.

[Illustration: Fig. 16.--The Spinal Column.]

This column supports the head, encloses and protects the spinal cord, and
forms the basis for the attachment of many muscles, especially those which
maintain the body in an erect position. Each vertebra has an opening
through its center, and the separate bones so rest, one upon another, that
these openings form a continuous canal from the head to the lower part of
the spine. The great nerve, known as the spinal cord, extends from
the cranium through the entire length of this canal. All along the spinal
column, and between each two adjoining bones, are openings on each side,
through which nerves pass out to be distributed to various parts of the