iOi ARTERIES OF THE TITER LLMB. 



the radial artery ; sometimes the ulnar is the branch given off ; tliat is to 

 )?ay, a branch con-esponding- to the uhiar in its distribution below the middle 

 of the fore-ann separates from a trunk which afterwards divides into the normal 

 radial artery and the interosseous of the fore-arm, which last is normally derived 

 from the ulnar artery. Rarely the interosseous of the fore-ann, or a va.f abcrrans, 

 is the branch given ofF. In one instance found in the dissecting room of Glasgow 

 University, the posterior interosseous artery of the fore-arm was thus given off. 



In all cases of the high origin of one or other of the arteries of the fore-ann, 

 the extent in which the two vessels thus formed run separatclj^ must vary accord- 

 ing to the height at which the main artery divides. The point of division in the 

 entire number of cases, without reference to the particular branch given off, is most 

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

 the arm. But the early division of the main artery of the upper limb may. as 

 mentioned in connection with the varieties of the axillary 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 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 cp-ses, is also of much surgical interest. 

 Usually they are close together, and occupy the ordinary position of the brachial 

 artery ; but it has been noticed that 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, some- 

 times suddenly, opposite the bend of the elbow, still covered by the fascia. It 

 has also been found, in a considerable number of instances, to perforate the 

 fascia, and run immediately under the skin, near the bend of the elbow. 



WTien the iilnar is the branch given off high from the brachial, it often inclines 

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

 inner condyle of the humems. This vessel generally lies beneath the fascia as it 

 <les inds, and superficial to the flexor muscles. It is occasionally placed between 

 thecanteguments and the fascia ; and in a single instance was found beneath the 

 muscles. In one instance occurring in the dissecting-room of the Glasgow 

 University, the ulnar artery given off from the humeral at the middle of the arm 

 was observed to descend superficially behind the inner condyle. 



The interosseous, after arising from the axillary or brachial artery, is commonly 

 situated behind the main artery, and, on reaching the bend of the elbow, 

 passes deeply between the muscles, to assume its usual position in the fore- 

 arm. 



Lastly, when the radial has arisen high in the arm, the residuary portion of the 

 brachial (ulnar- interosseous) has occasionally been observed descending, accom- 

 panied by the median nerve, along the intennuscular septum towai'ds the inner 

 condyle of the humerus, as far as the origin of the pronator teres (wliich in the 

 case recorded was found broader than iisual), whence it turned forwards under 

 cover of the muscle, to gain the usual position at the middle of the bend of the 

 €lbow. 



The two arteries taking the place of the brachial are in some instances con- 

 nected near the bend of the arm by an intervening trunk, which proceeds from 

 the larger (or ulnar-interosseous) artery to the radial or the radial recurrent, and 

 vanes somewhat in its size, form, and coui-se. More rarely the two unusual 

 ai'terics are actually re-united. 



The aberrant arteries, " vasa abenantia," alluded to above, are long slender 

 vessels, which arise either from the brachial or the axillary artery, and end by 

 joining one of the arteries of the fore-ai-m, or one of then- branches. In eight 

 i'ases out of nine, observed by Quain, this unusual vessel joined the radial ; in 

 the remaining case it joined the radial recun-ent. which arose irregularly from 

 tlie ulnar artery. Very rarely the aberrant vessel joins the ulnar. This peculiarity 

 may be regarded, perhaps, as an approach to that condition in which there is 

 <livision of the brachial artery and subsequent connection of its two parts by an 

 intervening branch. 



In most cases of the high division of the brachial arteries the condition of the 



