ticulation to the
greater cornu of the os hyoides. For the greater part of this extent it
is covered by the sterno-mastoid muscle; but as this latter takes an
oblique course backwards to its insertion into the mastoid process,
while the main blood-vessel dividing into branches still ascends in its
original direction, so is it that the artery becomes uncovered by the
muscle. Even the root of the internal carotid, E, may be readily reached
at this place, where it lies on the same plane as the external carotid,
but concealed in great part by the internal jugular vein. It would be
possible, while relaxing the sterno-mastoid muscle, to compress either
the common carotid artery or its main branches against the cervical
vertebral column, if pressure were made in a direction backwards and
inwards. The facial artery V, which springs from the external carotid,
D, may be compressed against the horizontal ramus of the lower jaw-bone
at the anterior border of the masseter muscle. The temporal artery, as
it ascends over the root of the zygoma, may be compressed effectually
against this bony point.

The external jugular vein, H, Plate 4, as it descends the neck from the
angle of the jaw obliquely backwards over the sterno-mastoid muscle, may
be easily compressed and opened in any part of its course. This vein
courses downwards upon the neck in relation to that branch of the
superficial cervical plexus, named auricularis magnus nerve, Q, Plate 4,
G, Plate 3. The nerve is generally situated behind the vein, to which it
lies sometimes in close proximity, and is liable, therefore, to be
accidentally injured in the performance of phlebotomy upon the external
jugular vein. The coats of the external jugular vein, E, Plate 3, are
said to hold connexion with some of the fibres of the platysma-myoides
muscle, A A, Plate 3, and that therefore, if the vessel be divided
transversely, the two orifices will remain patent for a time.

The position of the carotid artery protects the vessel, in some degree,
against the suicidal act, as generally attempted. The depth of the
incision necessary to reach the main blood-vessels from the fore part of
the neck is so considerable that the wound seldom effects more than the
opening of some part of the larynx. The ossified condition of the
thyroid and cricoid parts of the laryngeal apparatus affords a
protection to the vessels. The more oblique the incision happens to be,
the greater probability is there that t