The superior carotid triangle lies with its base against
the upper part of the stemo-mastoid, and has the
omo-hyoid below, the posterior belly of the digastricus
above, and the sterno-mastoid behind. The digastric
triangle is bounded above by the jaw, below by the
two bellies of the digastric muscle. To enable the
student to mark in these triangles, it is necessary that
he should know the relation of the omo-hyoid and
digastricus to the sui*face. A chalk line made from
the middle line of the neck, a little above the pomum
Adami (the prominence of the thyroid cartilage), to
the middle of the clavicle, will indicate the anterior
belly of the omo-hyoid. It may be mentioned that
it will be found to cross the common carotid artery at
the level of the cricoid cartilage. A line drawn from
the mastoid process past the edge of the angle of
the jaw to the body of, the hyoid bone, and thence to
the symphysis of the jaw, will mark the position of
the digastricus. The body of the hyoid bone is not
easy to feel in a fat subject, but lies just above the
thyroid cartilage. Although many structures are
enumerated as being part of the contents of these
triangles, yet it will be found that they do not lie
actually within their boundaries, but beneath them.
The skin should now be removed from the whole
of the anterior triangle. An incision has already
been made from the mastoid process along the lower
jaw as far as the symphysis. Make another along
the middle line of the neck. The skin should now be
dissected in a thin layer backwards towards the
posterior border of the stemo-mastoid. A few



262 The Dissector's Manual, [Cbap. ix.
