440 



THE ARTERIES OF THE UPPER LIMB. 



radial artery (fig. 360) ; sometimes the ulnar is the branch given off (fig 1 . 364), that is to say, 

 a branch corresponding to the ulnar in its distribution below the middle of the forearm 

 separates from a trunk which afterwards divides into the normal radial artery and the inter- 

 osseous of the forearm, which last is normally derived from the ulnar artery. More rarely 

 the branch given off is a ras aberrans ; or the proper trunk is continued into the interosseous 

 artery of the forearm, while the radial artery and the superficial part of the ulnar are derived 

 from the accessory vessel. In one instance the posterior interosseous artery was thus given 

 off in the arm (Allen Thomson). 



The point at which the division took place in cases of high origin of one or other of the 

 arteries of the forearm, without reference to the particular branch given off, was found to be 

 most frequently in the upper, less so in the lower, and least so in the middle third of the arm. 



Fig. 361. LARGE ACCESSORY VESSEL LEAVING THE BRACHIAL ARTERY 



IN THE MIDDLE OF THE ARM, AND FURNISHING THE RADIAL AND 

 THE GREATER PART OF THK ULNAR ARTERIES : THE BRACHIAL 

 TRUNK MUCH REDUCED IN SIZE PASSING BEHIND A SUPRACONDYLAR 

 PROCESS INTO THE ULNAR ARTERY. (R. Qviain. ) ^ 



a, biceps muscle ; b, triceps ; c, c, divided pronator teres ; d, 

 median nerve ; e, ulnar nerve ; 1, brachial artery, continued mainly 

 into the aberrant vessel ; 2, radial artery ; 3, proper continuation of 

 the brachial trunk, with the median nerve crossing it, passing at 3', 

 behind a supracondylar process ; 3", the same farther down, and open- 

 ing at 4', into the first part of the ulnar artery. 



But the early division of the main artery of the upper limb 

 may, as mentioned in connection with the varieties of the axil- 

 lary artery, take place within the axilla, in which case it follows 

 that the brachial portion of the vessel is replaced, throughout 

 its whole extent, by two separate trunks. In 94 cases out of 

 the 481 observed by R. Quain, or about one in five, there were 

 two arteries instead of one in some part of the arm. 



The position of the two arteries in these cases is also of 

 surgical interest. Usually they are close together, occupying 

 the ordinary position of the brachial artery, and the abnormal 

 vessel is generally the more superficial, being separated from the 

 normal trunk by the median nerve ; but the radial artery, when 

 thus given off in the arm , often arises from the inner side of the 

 brachial, then runs parallel with the larger vessel (the brachial 

 or ulnar-interosseous), and crosses over it, occasionally under it, 

 opposite the elbow, still covered by the fascia. The radial artery 

 has also been found, in a few instances, to perforate the fascia 

 near the bend of the elbow, and run immediately under the 

 skin for some distance. As a rare occurrence it passes behind 

 the tendon of the biceps to its usual place in the forearm. 



When the ulnar is the branch arising high, it often inclines 

 from the position of the brachial, at the lower part of the arm, 

 towards the inner condyle of the humerus (fig. 364). This vessel 

 generally lies beneath the fascia as it descends, and superficial to 

 the flexor muscles of the forearm, sometimes however crossing 



beneath the palmaris longus. It is occasionally placed between the integument and the fascia ; 

 and in one case only was it found by R. Quain beneath the muscles. In two instances the 

 ulnar artery given off from the brachial at the middle of the arm has been observed to descend 

 superficially behind the inner condyle. 



Lastly, when the radial arises high in the arm, or when the radial and a part of the ulnar 

 are derived from an accessory vessel thus given off, the prolongation of the normal trunk may 

 descend, accompanied by the median nerve, along the intermuscular septum towards the inner 

 condyle of the humerus. and turn forwards round a supracondylar process to the front of the 

 elbow (fig. 361). 



The two arteries occupying the place of the brachial are in some instances connected near 

 the bend of the arm by an intervening trunk, which varies in its size, form, and course. 



The aberrant arteries, " vasa aberrantia," alluded to above, are long slender vessels, which 

 arise from either the brachial or the axillary artery, and end by joining one of the arteries of 

 the forearm, or one of their branches. In eight cases out of nine, observed by R. Quain, this 

 unusual vessel joined the radial ; in the remaining case it joined the radial recurrent, which 

 arose irregularly from the ulnar artery. Very rarely the aberrant vessel joins the ulnar. 

 The existence of these aberrant vessels affords in some measure an explanation of the cases of 



