l these structures, except some of the lymphatic glands,
are concealed by the platysma myoides A, as seen in Plate 3, and beneath
this by the cervical fascia, which latter shall be hereafter more
clearly represented.

In somewhat the same mode as the posterior half of the omo-hyoid
subdivides the larger posterior triangle into two of lesser dimensions,
the anterior half of the same muscle divides the anterior triangle into
two of smaller capacity.

The great anterior triangle, which is marked as that space inclosed
within the points, 6, the top of the sternum, the mental symphysis and
the angle of the maxilla; and whose sides are marked by the median line
of the neck before, the sterno-mastoid behind, and the ramus of the jaw
above, contains C, the common carotid artery, becoming superficial from
beneath the sterno-mastoid muscle, and dividing into E, the internal
carotid, and D, the external carotid. The anterior jugular vein, 3, also
occupies this region below; while some venous branches, which join the
external and internal jugular veins, traverse it in all directions, and
present obstacles to the operator from their meshy plexiform arrangement
yielding, when divided, a profuse haemorrhage.

The precise locality at which the common carotid appears from under the
sterno-mastoid muscle is, in almost all instances, opposite to the
thyroid cartilage. At this place, if an incision, dividing the skin,
platysma and some superficial branches of nerves, be made along the
anterior border of the sterno-mastoid muscle, and this latter be turned
a little aside, a process of cervical fascia, and beneath it the sheath
of the carotid artery, will successionally disclose themselves. In many
bodies, however, some degree of careful search requires to be made prior
to the full exposure of the vessel in its sheath, in consequence of a
considerable quantity of adipose tissue, some lymphatic glands, and many
small veins lying in the immediate vicinity of the carotid artery and
internal jugular vein. This latter vessel, though usually lying
completely concealed by the sterno-mastoid muscle, is frequently to be
seen projecting from under its fore part. In emaciated bodies, where the
sterno-mastoid presents wasted proportions, it will, in consequence,
leave both the main blood-vessels uncovered at this locality in the
neck.

The common carotid artery ascends the cervical region almost
perpendicularly from opposite the sterno-clavicular ar