BRACHIAL ARTERY. 47 



covered only by the integuments and the deep fascia ; but at the 

 bend of the elbow it oecomes deeper, and is crossed by the pro- 

 longation from the tendon of the biceps. Posteriorly the artery has 

 the following muscular connections (fig. 20, p. 49): While it is and 

 inside the humerus it is placed over the long head of the triceps (F) muscles - 

 for two inches, but separated partly by the musculo-spiral nerve 

 and profunda vessels, and over the inner head (G) of the same 

 muscle for about an inch and a half. But when the vessel passes 

 to the front of the bone it lies on the insertion of the coraco- 

 brachialis (c) and on the brachialis anticus (H). To the outer 

 side are the coraco-brachialis and biceps muscles (c and B), the latter 

 overlapping it. 



Veins. Venae comites lie along the sides of the artery (fig. 20, <Z), with veins, 

 encircling it with cross branches, and the median-basilic vein 

 crosses over it at the elbow. The basilic vein is near the artery, 

 on the inner side, above ; but it is superficial to the fascia in the 

 lower half of the arm. 



The nerves in relation with the artery are the following : and with 

 The internal cutaneous (fig. 20, 2 ) is in contact with the vessel 

 until it perforates the fascia about the middle of the arm. The 

 ulnar nerve ( 4 ) lies to the inner side as far as the insertion of 

 the coraco-brachialis muscle ; and the niusculo-spiral is behind 

 for a distance of two inches. The median nerve (fig. 20, T ) is close 

 to the vessel throughout, but alters its position in this way : 

 as low as the insertion of the coraco-brachialis it is placed on 

 the outer side, but it then crosses obliquely over, or occasionally 

 under, the artery, and becomes internal about two inches above 

 the elbow-joint. 



Unusual position. The brachial trunk occasionally leaves the inner Deviation 

 border of the biceps in the lower half of the arm, and courses along the in position ; 

 intermusciilar septum, with or without the median nerve, to near the 

 inner condyle of the humerus. At this spot the vessel is directed to its 

 ordinary position in front of the elbow, beneath the upper fibres of the 

 pronator teres, which has then a wide origin. In this unusual course the 

 artery lies behind a projection (supracoudylar process) of the humerus. 



Muscular covering. In some bodies the brachial artery is covered by an in muscular 

 additional slip of origin of the biceps, or of the brachialis anticus muscle. coverm g- 

 And sometimes a slip of the brachialis may conceal, in cases of high 

 origin of the radial, the remainder of the arterial trunk continuing to the 

 forearm. 



High division. Instead of a single trunk, there may be two vessels in 4 rt ? 1 7 

 the lower part, or even the whole length of the arm, owing to an un- 

 usually high origin of one of the arteries of the forearm, more frequently 

 the radial. 



Vasa aberrant ia-. Occasionally a long slender vessel passes from the Aberrant 

 brachial or the axillary trunk to the radial, rarely to the ulnar artery. vessels. 



Branches spring both externally and internally from the brachial its branches 

 artery (fig. 18). Those on the outer side, muscular, supply the muscular 

 coraco-brachialis, biceps, and brachialis anticus, as well as the lower 

 part of the deltoid ; those on the inner side are the superior 

 and inferior profunda, the medullary artery of the humerus, 



