594 



THE ARTERIES. 



and the sides of which are bounded, externally, by the Supinator longus ; inter- 

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



Supinator brevis. This space, culltnl 

 fossa, 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 neck of the radius into the 

 radial and ulnar arteries ; it is covered, 

 in front, by the integument, the super- 

 ficial 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, close to 

 it above, but separated from it below 

 by the coronoid head of the Pronator 

 radii teres. The tendon of the Biceps 

 lies to the outer side of the space, and 

 the musculo-spiral nerve still more ex- 

 ternally, lying upon the Supinator 

 brevis and partly concealed by the 

 Supinator longus. 



Peculiarities of the Brachial Artery as 

 regards its Course. The brachial artery, ac- 

 companied by the median nerve, may leave the 

 inner border of the Biceps, and descend toward 

 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 outward, beneath or through the sub- 

 stance of the Pronator radii teres muscle, to 

 the bend of the elbow. The variation bears 

 considerable analogy with the normal condition 

 of the artery in some of the carnivora : it has 

 been referred to above in the description of 

 the humerus (page 250). 



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 the usual point, the former condition being by far the more frequent. Out of 481 exam- 

 inations 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 ot division 

 lower than usual, being two or three inches below the elbow-joint. " In 94 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 tor 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. That artery 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 perforate 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 ves- 

 sel at the lower part of the arm, and descends toward the inner condyle. In the forearm it gen- 



FIG. 363. The surgical anatomy of the brachial artery. 



