590 THE VASCULAR SYSTEMS 



below its usual position; if the artery be exposed at its point of bifurcation, both divisions of 

 the vessel should be tied near their origin, in preference to tying the trunk of the arterv near its 

 termination; and if, in consequence of the entire absence of the common carotid or from its 

 early division, two arteries, the external and internal carotids, are met with, the ligature should 

 be placed on that vessel which is found on compression to be connected with ihe diseased area 



Ligation of the Carotid at the Level of the Cricoid Cartilage (Ligation in the Triangle 

 of Election). 1 The triangle of election is bounded posteriorly by the anterior edge of the 

 Sternomastoid; is bounded above by the posterior belly of the Digastric; is bounded below 

 by the anterior belly of the Ornohyoid. In this operation the direction of the vessel and the 

 inner margin of the Sternomastoid are the chief guides to its performance. The patient should 

 be placed on his back with the head thrown back and turned slightly to the opposite side; an 

 incision is to be made, three inches long, in the direction of the anterior border of the Sterno- 

 mastoid, so that the centre corresponds to the level of the cricoid cartilage; after dividing the 

 integument, superficial fascia, and Platysma, the deep fascia must be cut through on a director, 

 so as to avoid wounding numerous small veins that are usually found beneath. The head may 

 now be brought forward so as to relax the parts somewhat, and the margins of the wound are 

 held asunder by retractors. The descendens hypoplossi nerve may now be exposed, and must 

 be avoided, and, the sheath of the vessel having been raised by forceps, is to be opened to a small 

 extent over the artery at its inner side. The internal jugular vein may present itself alternately 

 distended and relaxed; this should be compressed both above and below, and drawn outward, 

 in order to facilitate the operation. The aneurism needle is passed from the outside, care 

 being taken to keep the needle in close contact with the artery, and thus avoid the risk of injuring 

 the internal jugular vein or including the vagus nerve. Before the ligature is tied it should be 

 ascertained that nothing but the artery is included in it. 



Ligation of the Common Carotid at the Lower Part of the Neck (Ligation in the Triangle 

 of Necessity). 1 The triangle of necessity is bounded above by the anterior belly of the Omo- 

 hyoid; is bounded behind by the anterior margin of the Sternomastoid; is bounded in front 

 by the mid-line of the neck. This operation is sometimes required in cases of aneurism of the 

 upper part of the carotid, especially if the sac is of large size. It is best performed by dividing 

 the sternal origin of the Sternomastoid muscle, but may be done in some cases, if the aneurism 

 is not of very large size, by an incision along the anterior border of the Sternomastoid, extending 

 down to the sternoclavicular articulation, and by then retracting the muscle. The easiest and 

 best plan, however, is to make an incision two or three inches long down the lower part of the 

 anterior border of the Sternomastoid muscle to the sternoclavicular joint, and a second incision, 

 starting from the termination of the first, along the upper border of the clavicle for about two 

 inches. This incision is made through the superficial and deep fascia, and the sternal origin 

 of the muscle is exposed. This is to be divided on a director, and turned up, with the super- 

 ficial structures, as a triangular flap. Some loose connective tissue is to be divided or torn 

 through, and the outer border of the Sternohyoid muscle exposed. In doing this care must 

 be taken not to wound the anterior jugular vein, which crosses the muscle to reach the external 

 jugular or subclavian vein. The Sternohyoid, and with it the Sternothyroid, are to be drawn 

 inward by means of a retractor, and the sheath of the vessel is exposed. This must be opened 

 with great care on its inner or tracheal side, so as to avoid the internal jugular vein. This is 

 especially necessary on the left side, where the artery is commonly overlapped by the vein. 

 On the right side there is usually an interval between the artery and the vein, and not the same 

 risk of wounding the latter. 



The common carotid artery, being a long vessel without any branches, is particularly suitable 

 for the performance of Brasdor's operation for the cure of an aneurism of the lower part of the 

 vessel. Brasdor's procedure consists in ligating the artery on the distal side of the aneurism, 

 and in the case of the common carotid there are no branches given off from the vessel between 

 the aneurism and the site of the ligature; hence, the flow of blood through the sac of the aneurism 

 is diminished, and cure takes place in the usual way, by the deposit of laminated fibrin. 



Collateral Circulation. After ligation of the common carotid the collateral circulation can 

 he perfectly established by the free communication which exists between the carotid arteries 

 of opposite sides, both without and within the cranium, and by enlargement of the branches of 

 the subclavian artery on the side corresponding to that on which the vessel has been tied the 

 chief communication outside the skull taking place between the superior thyroid from the external 

 carotid and the inferior thyroid from the subclavian, the profunda cervicis from the subclavian 

 and the superior intercostal with the arteria princeps cervicis of the occipital; the vertebral 

 taking the place of the internal carotid within the cranium! 



1 For description of the triangles of the neck, see page 605. 



