THE SUBCLA VIAN ARTER Y 629 



lower border of the clavicle. The curve is to be drawn with such an amount of convexity that 

 its mid-point reaches half an inch above the upper border of the clavicle. The left subclavian 

 artery is more deeply placed than the right in the 'irst part of its course, and, as a rule, does not 

 reach quite as high a level in the neck. It should be borne in mind that the posterior border of 

 the Sternomastoid muscle corresponds to the outer border of the Scalenus anticus muscle, so 

 that the third portion of the artery, that part most accessible for operation, lies immediately 

 external to the posterior border of the Sternomastoid muscle. 



Applied Anatomy. The relations of the subclavian arteries of the two sides having been 

 examined, the student should direct his attention to a consideration of the best position in which 

 compression of the vessel may be effected, or in what situation a ligature may be best applied in 

 cases of aneurism or wound. 



Compression of the subclavian artery is required in cases of operation about the shoulder, 

 in the axilla, or at the upper part of the arm; and the student will observe that there is only 

 one situation in which it can be effectually applied viz., where the artery passes across the 

 upper surface of the first rib. In order to compress the vessel in this situation, the shoulder 

 should be depressed, and the surgeon, grasping the side of the neck, should press with his thumb 

 in the angle formed by the posterior border of the Sternomastoid with the upper border of the 

 clavicle, downward, backward, and inward against the rib; if from any cause the shoulder 

 cannot be sufficiently depressed, pressure may be made from before backward, so as to compress 

 the artery against the Scalenus medius muscle and the transverse process of the seventh cervical 

 vertebra. In appropriate cases a preliminary incision may be made through the cervical fascia, 

 and the finger may be pressed down directly upon the artery. 



Ligation of the subclavian artery may be required in cases of wounds or of aneurism in the 

 axilla, or in cases of aneurism on the cardiac side of the point of ligation; and the third part of 

 the artery is that which is most favorable for an operation, on account of its being compara- 

 tively superficial and most remote from the origin of the large branches. In those cases where 

 the clavicle is not displaced, this operation may be performed with comparative facility; but 

 where the clavicle is pushed up by a large aneurismal tumor in the axilla the artery is placed at 

 a great depth from the surface, which materially increases the difficulty of the operation. Under 

 these circumstances it becomes a matter of importance to consider the height to which this 

 vessel reaches above the bone. In ordinary cases its arch is about half an inch above the clavicle, 

 occasionally it is as high as an inch and a half, and sometimes so low as to be on a level with 

 the upper border of the clavicle. If the clavicle is displaced, these variations will necessarily 

 make the operation more or less difficult, according as the vessel is more or less accessible. 



The procedure in the operation of tying the third portion of the subclavian artery is as fol- 

 lows: The patient being placed on a table in the supine position, with the head drawn over to 

 the opposite side and the shoulder depressed as much as possible, the integument should be 

 drawn downward over the clavicle, and an incision made through it, upon that bone, from the 

 anterior border of the Trapezius to the posterior border of the Sternomastoid, to which may be 

 added a short vertical incision meeting the inner end of the preceding. The object in drawing 

 the skin downward is to avoid any risk of wounding the external jugular vein, for as it perforates 

 the deep fascia above the clavicle, it cannot be drawn downward with the skin. The soft parts 

 should now be allowed to glide up, and the cervical fascia should be divided upon a director, 

 and if the interval between the Trapezius and Sternomastoid muscles be insufficient for the per- 

 formance of the operation, a portion of one or both may be divided. The external jugular vein 

 will now be seen toward the inner side of the wound; this and the suprascapular and transverse 

 cervical veins, which terminate in it, should be held aside. If the external jugular vein is at all 

 in the way and exposed to injury, it should be tied in two places and divided. The suprascapular 

 arterv should be avoided, and the Omohyoid muscle held aside if necessary. In the space 

 beneath this muscle careful search must be made for the vessel ; a layer of deep fascia and some 

 connective tissue having been divided carefully, the outer margin of the Scalenus anticus muscle 

 must be felt for, and, the finger being guided by it to the first rib, the pulsation of the subclavian 

 artery will be felt as it passes over the rib. The sheath of the vessels having been opened, 

 the aneurism needle may then be passed around the arterv from above downward and inward, so 

 as to avoid including any of the branches of the brachial plexus. If the clavicle is so raised by 

 the tumor that the application of the ligature cannot be effected in this situation, the artery may 

 be tied above the first rib, or even behind the Scalenus anticus muscle; the difficulties of the 

 operation in such a case will be materially increased, on account of the greater depth of the artery 

 and the alteration in position of the surrounding parts. 



The second part of the subclavian arterv, from being that portion which rises highest in the 

 neck, has been considered favorable for the application of the ligature when it is difficult to tie 

 the arterv in the third part of its course. There are, however, many objections to the oper- 

 ation in this situation. It is necessary to divide the Scalenus anticus muscle, upon which lies 

 the phrenic nerve, and at the inner side of which is situated the internal jugular vein; and a 

 wound of either of these structures might lead to the most dangerous consequences. Again, 

 the artery is ir contact, below, with the pleura, which mu-*t also be avoided; and, lastly, the 



