SUBCLAVIAN. 471 



The origin of the right subclavian from the innominate takes place, in some cases, above the 

 iterno-clavicular articulation ; and occasionally, but less frequently, in the cavity of the thorax, 

 below that joint. Or the artery may arise us a separate trunk from the arch of the aorta. In 

 such cases it may be either the first, second, third, or even the last branch derived from that 

 vessel : in the majority of cases, it is the first or last, rarely the second or third. When it is the 

 first branch, it occupies the ordinary position of the innominate artery ; when the second or third, 

 it gains its usual position by passing behind the right carotid ; and when the hist branch, it arises 

 from the left extremity of the arch, at its upper or back part, and passes obliquely towards the 

 right side, usually behind the oesophagus and right carotid, sometimes between the oesophagus 

 and trachea, to the upper border of the first rib, whence it follows its ordinary course. In very 

 rare instances, this vessel arises from the thoracic aorta, as low down as the fourth dorsal verte- 

 bra. Occasionally it perforates the Anterior Scalenus ; more rarely it passes in front of that 

 muscle; sometimes the subclavian vein passes with the artery behind the Scalenus. The artery 

 sometimes ascends as high as an inch and a half above the clavicle, or to any intermediate point 

 between this and the upper border of the bone, the right subclavian usually ascending higher 

 than the left. 



The left subclavian is occasionally joined at its origin with the left carotid. 



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

 examined, the student should direct his attention to consider the best position in which com- 

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

 cases of aneurism or wounds. 



Compression of the subclavian artery is required in cases of operations 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 outer 

 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, may press with his thumb in the hollow 

 behind the clavicle downwards against the rib ; if from any cause the shoulder cannot be suffi- 

 ciently depressed, pressure may be made from before backwards, so as to compress the artery 

 against the Middle Scalenus and transverse process of the seventh cervical vertebra. In appro- 

 priate cases, a preliminary incision may be made through the cervical fascia, and the finger may 

 be pressed down directly upon the artery. 



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

 axilla ; and the third part of the artery is that which is most favorable for an operation, on 

 account of its being comparatively superficial, and most remote from the origin of the large 

 branches. In those cases where the clavicle is not displaced, this operation may be per- 

 formed 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 in- 

 creases 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 as high as an inch and a 

 half, and sometimes so low as to be on a level with its upper border. 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 chief points in the operation of tying the third portion of the subclavian artery are as 

 follows : the patient being placed on a table in the horizontal position, and the shoulder de- 

 pressed as much as possible, the integument should be drawn downwards upon the clavicle, and 

 an incision made through it upon that bone from the anterior border of the Trapezius to the 

 posterior border of the Sterno-mastoid, to which may be added a short vertical incision meeting 

 the centre of the preceding ; the Platysma and cervical fascia should be divided upon a director, 

 and if the interval between the Trapezius and Sterno-mastoid muscles be insufficient tor the per- 

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

 will now be seen towards the inner side of the wound : this and the suprascapular and trans- 

 verse cervical veins which terminate in it should be held aside, and if divided, both ends should 

 be tied : the suprascapular artery should be avoided, and the Omo-hyoid muscle must now be 

 looked for, and held aside if necessary. In the space beneath this muscle, careful search must 

 be made for the vessel ; the deep fascia having been divided with the finger-nail or silver scalpel, 

 the outer margin of the Scalenus 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 aneurism 

 needle may then be passed around the vessel from before backwards, by which means the vein 

 will be avoided, care being taken not to include a branch of the brachial plexus instead of the 

 artery in the ligature. If the clavicle is so raised by the tumor that the application of the liga- 

 ture cannot be effected in this situation, the artery may be tied above the first rib, or even behind 

 the Scalenus 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 artery, 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 artery in the third part of its course. There are, however, many objections to the operation 

 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 



