BRACHIAL. 407 



BEXD OF THE ELBOW. 



At the bend of the elbow, the brachial artery sinks deeply into a triangular 

 interval, the base of which is directed upwards towards the humerus, and the sides 

 of which are bounded, externally, by the Supinator longus ; internally, by the 

 Pronator radii teres ; its floor is formed by the Brachialis anticus and Supinator 

 brevis. This space contains the brachial artery, with its accompanying veins ; the 

 radial and ulnar arteries; the median and musculo-spiral nerves; and the tendon 

 of the Biceps. The brachial artery occupies the middle line of this space, and 

 divides opposite the coronoid process of the ulna into the radial and ulnar arteries ; 

 it is covered, in front, by the integument, the superficial fascia, and the median 

 basilic vein, the vein being separated from direct contact with the artery by the 

 bicipital fascia. Behind, it lies on the Brachialis anticus, which separates it from 

 the elbow-joint. The median nerve lies on the inner side of the artery, but is 

 separated from it below by an interval of half an inch. The tendon of the Biceps 

 lies to the outer side of the space, and the musculo-spiral nerve still more 

 externally, lying upon the Supinator brevis, and partly concealed by the Supinator 

 longus. 



Peculiarities of the Artery as regards its Course. The brachial artery, accompanied by the 

 median nerve, may leave the inner border of the Biceps, and descend towards the inner condyle 

 of the humerus, where it usually curves round a prominence of bone, to which it is connected by 

 a fibrous band ; it then inclines outwards, beneath or through the substance of the Pronator teres 

 muscle, to the bend of the elbow. This variation bears considerable analogy with the normal 

 condition of the artery in some of the carnivora (see p. 131). 



Peculiarities as regards its Division. Occasionally, the artery is divided for a short distance 

 at its upper part into two trunks, which are united above and below. A similar peculiarity occurs 

 in the main vessel of the lower limb. 



The point of bifurcation may be above or below th usual point, the former condition being 

 by far the most frequent. Out of 481 examinations recorded by Mr. Quain, some made on the 

 right, and some on the left side of the body, in 386 the artery bifurcated in its normal position. 

 In one case only was the place of division lower than usual, being two or three inches below the 

 elbow-joint. In 90 cases out of 481, or about 1 in 5, there were two arteries instead of one in 

 some part, or in the whole of the arm. 



There appears, however, to be no correspondence between the arteries of the two arms, with 

 respect to their irregular division ; for in 61 bodies it occurred on one side only in 43 ; on 

 both sides, in different positions, in 13 ; on both sides, in the same position, in 5. 



The point of bifurcation takes place at different parts of the arm, being most frequent in the 

 upper part, less so in the lower part, and least so in the middle, the most usual point for the 

 application of a ligature ; under any of these circumstances, two large arteries would be found 

 in the arm instead of one. The most frequent (in three out of four) of these peculiarities is the 

 high division of the radial. It often arises from the inner side of the brachial, and runs parallel 

 with the main trunk to the elbow, where it crosses it, lying beneath the fascia ; or it may perfo- 

 rate the fascia, and pass over the artery, immediately beneath the integument. 



The ulnar sometimes arises from the brachial high up, and then occasionally leaves that vessel 

 at the lower part of the arm, and descends towards the inner condyle. In the forearm, it gene- 

 rally lies beneath the deep fascia, superficial to the Flexor muscles ; occasionally between the 

 integument and deep fascia, and very rarely beneath the Flexor muscles. 



The interosseous artery sometimes arises from the upper part of the brachial or axillary : as 

 it descends the arm, it lies behind the main trunk, and at the bend of the elbow regains its usual 

 position. 



In some cases of high division of the radial, the remaining trunk (ulnar interosseous) occasion- 

 ally passes, together with the median nerve, along the inner margin of the arm to the inner con- 

 dyle, and then passing from within outwards, beneath or through the Pronator teres, regains its 

 usual position at the end of the elbow. 



Occasionally, the two arteries representing the brachial are connected at the bend of the elbow 

 by a short transverse branch, and arc even sometimes reunited. 



Sometimes, long slender vessels, rasa abcrrantia, connect the brachial or axillary arteries 

 with one of the arteries of the forearm, or a branch from them. These vessels usually join the 

 radial. 



