The length of the common carotid artery varies, of course, according to the place where the innominate artery below divides, and also according to that place whereat the common carotid itself divides into internal and external carotids. In general, the length of the common carotid is considerable, and ranges between the sterno-clavicular articulation and the level of the os hyoides; throughout the whole of this length, it seldom or never happens that a large arterial branch is given off from the vessel, and the operation of ligaturing the common carotid is therefore much more likely to answer the results required of that proceeding than can be expected from the ligature of any part of the subclavian artery which gives off large arterial branches from every part of its course. The sympathetic nerve, R, Plate 6, is as close to the carotid artery behind, as the vagus nerve, N, Plate 5, and is as much endangered in ligaturing this vessel. The branch of the ninth nerve, E, Plate 5, (descendens noni,) lies upon the common carotid, itself or its sheath, and is likely to be included in the ligature oftener than we are aware of. The trunk of the external carotid, D, Plate 5, is in all cases very short, and in many bodies can scarcely be said to exist, in consequence of the thyroid, lingual, facial, temporal, and occipital branches, springing directly from almost the same point at which the common carotid gives off the internal carotid artery. The internal carotid is certainly the continuation of the common arterial trunk, while the vessel named external carotid is only a series of its branches. If the greater size of the internal carotid artery, compared to that of the external carotid, be not sufficient to prove that the former is the proper continuation of the common carotid, a fact may be drawn from comparative philosophy which will put the question beyond doubt, namely--that as the common carotid follows the line of the cervical vertebrae, just as the aorta follows that of the vertebrae of the trunk, so does the internal carotid follow the line of the cephalic vertebrae. I liken, therefore, those branches of the so-called external carotid to be, as it were, the visceral arteries of the face and neck. It would be quite possible to demonstrate this point of analogy, were this the place for analogical reasoning. The common carotid, or the internal, may be compressed against the rectus capitis anticus major muscle, 13, Plate 6, as it lies on the fore-part of the vertebral column. The internal maxillary artery, 16, Plate 6, and the facial artery, G, Plate 5, are those vessels which bleed when the lower maxilla is amputated. In this operation, the temporal artery, 15, Plate 6, will hardly escape being divided also, it lies in such close proximity to the neck and condyle of the jaw-bone.