756 HUMAN ANATOMY. 



Practical Considerations. — The subclavian artery may require ligation, on 

 account of stab wounds, as a preliminary to the removal of growths — axillary or 

 scapular — or to an interscapulo-thoracic amputation, or in cases of axillary or sub- 

 clavian aneurism, or, together with the common carotid artery, in aortic or 

 innominate aneurism. 



On the surface of the neck the subclavian artery is represented by a cur\'e, 

 convex upward, beginning at the sterno-clavicular articulation and ending beneath 

 the middle of the clavicle, its highest point being on an average about five-eighths 

 of an inch above that bone. The vein is lower, is in fropt of the artery (separated 

 from it by the scalenus anticus muscle), and is usually nearly or quite under cover 

 of the clavicle. 



Aneurism of the subclavian is more frequent on the right side, probably because 

 of the greater use and consequent greater exposure to strain of the right upper 

 extremity. It may affect any portion of the vessel, but the third portion — external 

 to the scaleni, where it is least supported by surrounding muscles — is most com- 

 monly involved either primarily or by extension of an aneurismal dilatation upward 

 from the axillary or downward from the arch of the subclavian. The thoracic 

 portion of the left subclavian is never the primary seat of aneurism. 



The symptoms are : i^a) pain or numbness and loss of power in the arm and 

 hand from pressure on the brachial plexus ; (<5) swelling and cedema of the arm and 

 hand from pressure on the subclavian vein ; (<:) hiccough or irregular, jerky res- 

 piration from pressure on the phrenic nerve ; (fl^) vertigo, somnolence, defective 

 vision, from compression of the internal jugular ; (^) tu?nor, usually appearing in 

 the posterior inferior cervical triangle, with its long diameter approximately parallel 

 with the clavicle, and extending upward and outward ; exceptionally it grows down- 

 ward, but this is rare on account of the resistance offered by the clavicle, the first 

 rib, and the structures filling the costo-clavicular space. 



Digital co9npression of the first and second portions of the artery is practically 

 impossible. The third portion may be imperfectly occluded by making strong 

 pressure directly backward just above the clavicle, a little external to its middle, so 

 that the artery may be flattened out or narrowed against the scalenus medius muscle 

 and the seventh cervical transverse process. Much more effectual pressure may be 

 made at the same point, especially if the tip of the shoulder can be lowered so as to 

 carry the clavicle downward and make the upper surface of the first rib more 

 accessible, in a direction downward, backward, and inward, — i..e., in a line nearly or 

 quite perpendicular to the plane of that surface. The vessel is thus compressed 

 against it, and is not pushed off of it. It will be useful to recall that the outer border 

 of the scalenus anticus and the posterior border of the sterno-mastoid — the latter 

 palpable and often visible — are approximately on the same line, immediately outside 

 of which is the third portion of the vessel. The scalene tubercle — the elevation or 

 roughening on the upper surface of the first rib between the shallow depression for 

 the subclavian vein and the deeper groove for the subclavian artery — gives attach- 

 ment to the scalenus anticus and, when recognized, serves as a valuable guide to the 

 vessel.  



Ligation. — The first portion — between the origin of the vessel and the inner side 

 of the scalenus anticus — has been ligated with uniformly fatal results. On the left 

 side it is so situated as to depth, origin of branches — the vertebral, internal mammary, 

 thyroid axis, and superior intercostal — and contiguity of important structures — the 

 heart, the aorta, the pleura, the innominate vein, the thoracic duct, the pneumogastric, 

 cardiac, recurrent laryngeal and phrenic nerves — that its ligation has only once 

 been accomplished (Rodgers). On the right side the operative procedure is some- 

 what less difficult, but many of the relations are identical {vide supra), and the 

 procedure is still so formidable that its description is included in some works on 

 operative surgery only because the ligation ' ' affords good practice on the dead 

 subject" (Jacobson). 



The steps of the operation are the same as those in ligation of the innominate 

 (page 729) until the carotid sheath is reached and opened. The internal jugular 

 vein and pneumogastric nerve should be drawn aside (inward, Agnew ; outward, 

 Barwell) and the subclavian recognized, springing from the bifurcation of the innom^ 



