[Illustration: Fig. 12.
A vertebra of the neck. _1_. The
body of the vertebra. _2_. The spinal
canal. _4_. The spinous process
cleft at its extremity. _5_. The
transverse process. _7_. The interior
articular process. _8_. The
superior articular process.]

THE TRUNK has fifty-four bones, which are as follows: The _Os Hyoides_,
the _Sternum_, twenty-four Ribs, twenty-four _vertebræ_ or bones of the
Spinal Column, the _Sacrum_, the _Coccyx_, and two _Ossa Innominata_.
The _Os Hyoides_, situated at the base of the tongue, is the most
isolated bone of the skeleton, and serves for the attachment of muscles.
The _Sternum_, or breast-bone, in a child is composed of six pieces, in
the adult of three, which in old age are consolidated into one bone. The
_Ribs_ are thin, curved bones, being convex externally. There are twelve
on each side, and all are attached to the spinal column. The seven upper
ribs, which are united in front of the sternum, are termed _true_ ribs;
the next three, which are not attached to the sternum, but to one
another are called _false_ ribs; and the last two, which are joined only
to the vertebræ, are designated as _floating_ ribs. The first rib is the
shortest, and they increase in length as far as the eighth, after which
this order is reversed.

[Illustration: Fig. 13.
_1_. The cartilaginous substance
which connects the bodies of
the vertebræ. _2_. The body of the
vertebra. _3_. The spinous process.