The carotid arteries; from Carotideae Arterae 1729 the head, or sleep; since, when the current of blood is diminished through these vessels, stupor follows.

From the fore part of the curvature of the aorta, just before the trachea, the right subclavian and the carotid mostly arise in one common trunk, which runs upwards a little way, and then divides. The left carotid rises singly, and runs upwards on the side of the trachea. Both these carotids run up as high as the side of the larynx, even to the upper part of the thyroid cartilage, before they give off one branch, and there they divide into the external and internal: the latter goes to the inside of the cranium; the former, which is the largest, gives branches to all the external parts of the head.

The external carotid is anterior, the internal is posterior; the external situated more inward and nearer the larynx. It is the smallest, runs insensibly outward between the external angle of the lower jaw and the parotid gland, which it supplies as it passes; afterwards it ascends on the fore side of the ear, and ends in the temples. It sends off the gutturalis superior, sublingualis, maxillaria inferior, maxillaria externa, etc. The internal carotid leaving the general trunk is, at first, a little incurvated. It is situated a little more backward than the external, and generally runs up, without any ramification, as high as the lower orifice of the great canal of the apophysis petrosa of the os temporis: it enters this orifice, and the cranium, through an irregular aperture in the sphenoidal bone; and, except one branch, which goes to the eye, it is wholly spent upon the brain. See Winslow's Anatomy.