THE BRACHIAL ARTERY. 441 



high division, since it is obvious that the latter condition would result if the normal origin of 

 one of the forearm arteries at the elbow were obliterated, and the detached vessel were 

 continued from an enlarged aberrant artery. The bicipital branch of the brachial artery 

 passing in front of the median nerve appears to be the remains of such an aberrant vessel. It 

 is probable that that form of variety in which the radial artery arises in the arm, while the 

 continuation of the brachial trunk passes behind a supracondylar process, represents a more 

 primitive condition. (G-. Ruge, " Beitrage zur G-efasslehre des Menschen," Morph. Jahrb., ix, 

 1884.) 



In most cases of high division of the brachial artery the condition of the vessels is not 

 the same in the right and left arms. In 61 bodies in which the high division existed, it 

 occurred on one side only in 43 ; on both sides, in different positions, in 13 ; and on both 

 sides, in the same position, in the remaining 5. 



A median artery of large size (pp. 443, 446) has also been seen arising from the brachial, 

 and in one or two cases this vessel passed downwards over the muscles of the forearm to reach 

 the palm of the hand. 



In a very few cases the three arteries of the forearm, radial, ulnar, and interosseous, have 

 arisen together from the end of the brachial trunk, at the usual distance below the elbow. 



Relations. The brachial artery is occasionally covered in some part of the arm by a fleshy 

 slip connected with the coraco-brachialis, biceps, brachialis anticus, or pronator teres muscle. 



The median nerve sometimes passes behind, instead of in front of, the brachial artery, and 

 in these cases it will be generally found that the axillary artery presents the variety referred 

 to on p. 435, in which several of the large branches are arising by a common trunk. 



Brandies. It has been already mentioned that the superior profunda may give origin to 

 the posterior circumflex artery, and that its own origin is sometimes transferred to a branch 

 arising from the axillary artery. 



The inferior profunda is occasionally absent. It is frequently united at its origin with 

 the superior profunda. 



The anastomotic artery is sometimes much reduced in size, and in that case the inferior 

 profunda takes its place behind the humerus. 



SURGICAL ANATOMY OF THE BRACHIAL ARTERY. 



The brachial artery may be easily reached for the application of a ligature in any part of 

 its course. In the middle third of the arm the inner edge of the biceps muscle, where its 

 pulsation may commonly be felt, is the guide for the incision. From the thinness of 

 the parts covering the artery, however, and the proximity of superficial veins, especially the 

 basilic, the integuments and fascia must be divided with caution. The inner border of the 

 biceps having been exposed, the muscle is to be drawn outwards ; and the median nerve, which 

 now comes into view, is to be carefully isolated and drawn to one side, when the arbery is seen 

 lying between its two companion veins. The aneurism-needle should be passed from the 

 nerve. Occasionally it is found necessary to divide some muscular fibres before the artery is 

 reached. 



In the lower third of the arm, the median nerve being placed to the inner side, the artery is 

 more fully exposed after division of the fascia, but here care is necessary in passing the 

 ligature round the artery, to avoid the venae comites or their communicating cross branches, 

 which cling very closely to the artery. 



From the very frequent occurrence of varieties in the mode of division of the brachial 

 artery into the vessels derived from it, the surgeon must be prepared for many deviations 

 from the usual condition of the parts, and especially for the presence of two arteries in place 

 of one in the lower third of the brachial region. In such cases the two arteries are most 

 frequently close together and nearly parallel, and it will be easy to tie both vessels, should 

 this be rendered necessary by the nature of the injury for which the operation is performed. 

 But, as will be seen from what has previously been said of the abnormal forms of the brachial 

 artery, the position of one or both the vessels may be subject to very considerable variation 

 in different instances ; and in some of these, while one of the vessels is near the usual position, 

 the other may be at some distance, as for example, when it passes beneath a supracondylar 

 process of the humerus. 



At the bend of the elbow, the brachial artery is exposed to the risk of injury during the 

 operation of venesection, for which the median-basilic vein is commonly selected. This vein 

 lies here in front of the artery, the semilunar fascia being stretched between them. Instances 

 are known in which the artery has been wounded by the lancet transfixing the vein and 

 fascia, and a communication has thus been established between the vein and artery. On this 

 account the incision into the vein must be made with due care, and indeed the median- 

 cephalic, if of sufficient size, may be selected for the operation. 



Collateral circulation. When the brachial artery has been tied in the middle of the arm, 



