Peculiarities as to Origin.-The right common carotid may arise above the level of the upper border of the sterna clavicle articulation; this variation occurs in about 12 percent. of cases. In other cases the artery may arise as a separate branch from the arch of the aorta, or in conjunction with the left carotid. The left common carotid varies in its origin more than the right. In the majority of abnormal cases it arises with the in nominate artery; if that artery is absent, the two carotids arise usually by a single trunk. It is rarely joined with the left subclavian, except in cases of transposition of the aortic arch. Peculiarities as to Point of Division. In the majority of abnormal cases this occurs higher than usual, the artery dividing opposite or even above the hyoid bone; more rarely, it occurs below, opposite the middle of the larynx, or the lower border of the cricoids cartilage; one case is related by Morgan, where the artery was only 4 cm. in length and divided at the root of the neck. Very rarely.