This section is from the book "Anatomy Of The Arteries Of The Human Body", by John Hatch Power. Also available from Amazon: Anatomy of the Arteries of the Human Body, with the Descriptive Anatomy of the Heart.
The first incision should commence a little beneath the angle of the lower jaw, and terminate on the side of the cricoid cartilage. This incision will divide the skin, platysma myoides, and cervical fascia, and expose the sheath of the vessels with the descendens noni nerve lying on its front. The nerve is to be drawn outwards, and the sheath opened in the cautious manner already described. The artery being now exposed, the needle is to be carried around it from without inwards, taking care (as in the inferior operations) not to wound the jugular vein nor include the pneumogastric nerve. It should also be remembered that the communicans noni, a branch of the cervical plexus, not unfrequently descends within the sheath of the vessels between the carotid artery and jugular vein.
Having arrived opposite the superior margin of the thyroid cartilage, and below the great cornu of the os hyoides, the common carotid artery of each side divides into the external and internal carotid arteries. At the point of bifurcation the artery generally presents a transverse dilatation, so that the vessel appears enlarged in this situation. This enlargement lies anterior to the longus colli and rectus capitis anticus major muscles, corresponding to about the third cervical vertebra, and in the adult to a point about one inch below the angle of the lower jaw. In old age, from the absence of the teeth, the angle of the jaw is removed still farther above the bifurcation of the common carotid; in infancy also, before the appearance of the teeth, the angle of the lower jaw is situated at a comparatively considerable distance above the division of the common carotid artery.