254 DISSECTION OF THE ARM. 



AVhilst it is inside the humerus it is placed over the long head of the tri- 

 ceps F, for two inches, but separated partly by the musculo-spinil 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 turns to the front of the 

 bone, it lies on the insertion of the coraco-brachialis, c, and on the brachi- 

 alis anticus, H. To the outer side are laid the coraco-brachialis and 

 biceps muscles, c, and B, the latter overlapping it. 



Veins. Venae comites lie on the sides of the artery (fig. 78, c?), encir- 

 cling it with branches, and the median basilic vein crosses over it at the 

 elbow. The basilic vein is near, and inside the artery above, but is 

 superficial to the fascia in the lower half of the arm. 



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

 cutaneous ( 2 ) is in contact with the vessel until it perforates the fascia 

 about the middle of the arm. The ulnar nerve: (*) lies to the inner side 

 as far as the insertion of the coraco-brachialis muscle; and the musculo- 

 spiral (fig. 69, 4 ) is behind for a distance of two inches. The median 

 nerve ( l ) is close to the vessel throughout, but alters its position in this 

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

 outer side, but it then crosses obliquely either over or under the artery, 

 and becomes internal about two inches above the elbow joint. 



Peculiarities in position. The brachial trunk may leave the inner border of the 

 biceps in the lower half of the arm, and course along the interniuscular septum, 

 with or without the median nerve, to the inner condyle of the humerus. At this 

 spot the vessel is directed to its ordinary position in front of the elbow, either 

 through or beneath the fibres of the pronator teres, which has then a wide origin. 

 In this unusual course the artery lies behind a projecting bony point of the hu- 

 merus. 



Muscular covering. In some bodies the humeral artery is covered by an addi- 

 tional slip of origin of the biceps, or of the brachialis anticus muscle. And some- 

 times 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. 



Branches spring both externally and internally from the brachial artery 

 (fig. 77). Those on the outer side, muscular^ supply the coraco-brachi- 

 alis, biceps, and brachialis anticus ; those on the inner side are named 

 superior and inferior profunda, nutritious, and anastomotic. 



The superior profunda branch ( 5 ) is larger than the others, and leaves 

 the artery near the lower border of the teres major; it winds backwards 

 with the musculo-spiral nerve to the triceps muscle, and will be dissected 

 with the back of the arm. 



The inferior profunda branch ( 6 ) arises opposite the coraco-brachialis 

 muscle, and accompanies the ulnar nerve to the interval between the 

 olecranon and the inner condyle of the humerus. There it anastomoses 

 with the posterior ulnar recurrent and anastomotic branches, and sup- 

 plies the triceps. It arises often in common with the superior profunda 

 artery. 



A nutritious artery of the bone shaft begins near the preceding branch, 

 Mini enters the large aperture about the middle of the humerus; it is dis- 

 tributed to the osseous and the medullary substance. 



The anastomotic branch ( 7 ) arises one to two inches above the elbow, 

 and courses inwards through the internmscular septum to the hollow be- 

 tween the olecranon and the inner condyle of the humerus. Here the 

 artery inosculates with the inferior profunda and posterior ulnar recurrent 

 branches, and gives twigs to the triceps muscle : one of the offsets forms 



