The length of the subclavian artery between its point of branching from the innominate and that where it gives off its first branches varies in different bodies, but is seldom so extensive as to assure the operator of the ultimate success of the process of ligaturing the vessel. Above and below D, Plate 6, the thyroid axis, come off the vertebral and internal mammary arteries internal and anterior to the scalenus muscle. External and posterior to the scalenus, a large vessel, the post scapular, G, Plate 6, R, Plate 5, arises. If an aneurism attack any part of this subclavian arch, it must be in close connexion with some one of these branches. If a ligature is to be applied to any part of the arch, it will seldom happen that it can be placed farther than half an inch from some of these principal collateral branches. When the shoulder is depressed, the clavicle follows it, and the subclavian artery will be more exposed and more easily reached than if the shoulder be elevated, as this latter movement raises the clavicle over the locality of the vessel. Dupuytren alludes practically to the different depths of the subclavian artery in subjects with short necks and high shoulders, and those with long necks and pendent shoulders. When the clavicle is depressed to the fullest extent, if then the sterno-cleido-mastoid and scalenus muscles be relaxed by inclining the head and neck towards the artery, I believe it may be possible to arrest the flow of blood through the artery by compressing it against the first rib, and this position will also facilitate the operation of ligaturing the vessel. The subclavian vein, W, Plate 5, is removed to some distance from the artery, Q, Plate 5. The width of the scalenus muscle, X, separates the vein from the artery. An instance is recorded by Blandin in which the vein passed in company with the artery under the scalenus muscle. DESCRIPTION OF PLATES 5 & 6. PLATE 5. A. Innominate artery at its point of bifurcation. B. Subclavian artery crossed by the vagus nerve. C. Common carotid artery with the vagus nerve at its outer side, and the descendens noni nerve lying on it. D. External carotid artery. E. Internal carotid artery with the descendens noni nerve lying on it. F. Lingual artery passing under the fibres of the hyo-glossus muscle. G. Tortuous facial artery. H. Temporo-maxillary artery. I. Occipital artery crossing the internal carotid artery and jugular vein. K. Internal jugular vein crossed by some branches of the cervical plexus, which join the descendens noni nerve. L. Spinal accessory nerve, which pierces the sterno-mastoid muscle, to be distributed to it and the trapezius. M. Cervical plexus of nerves giving off the phrenic nerve to descend the neck on the outer side of the internal jugular vein and over the scalenus muscle. N. Vagus nerve between the carotid artery and internal jugular vein.