234 DISSECTION OF THE UPPER LIMB. 



in contact behind, for the artery is placed across the top of the axilla, 

 particularly when the limb is in the position required by the dissection. 



The companion vein (g) lies to the inner side, but separated from the 

 arterial trunk by a bundle of nerves. 



In this position the cords of the brachial plexus lie around it, one 

 being outside, a second inside, and a third beneath the artery. 



Beyond the pectoralis minor the artery is concealed in part by the lower 

 border of the great pectoral muscle A, but thence to its termination it is 

 covered only by the integuments and the fascia. Beneath it are the sub- 

 scapularis muscle, F, and the tendons of the latissimus and teres, G and n. 

 To the outer side is the coraco-brachialis muscle, J. 



The axillary vein remains as above on the thoracic side of the artery. 



Here the artery lies in the midst of the large trunks of nerves into 

 which the brachial plexus has been resolved : On the outer side is the 

 median nerve, with the musculo-cutaneous for a short distance; and on 

 the inner side are the ulnar, and the nerve of Wrisberg. Superficial to 

 the vessel is the internal cutaneous; and behind are the muse ulo -spiral 

 and circumflex nerves, the latter extending only as far as the border of 

 the subscapular muscle. 



The branches of the axillary artery are furnished to the wall of the 

 thorax and the shoulder. The thoracic branches are four in number; two 

 (superior and acromial thoracic) arise from the artery above the pectoralis 

 minor; one (alar thoracic) beneath the muscle; and one (long thoracic) 

 at the lower border. Three branches are supplied to the shoulder, viz., 

 subscapular and two circumflex ; the first springs opposite the edge of the 

 muscle of the same name, and the others wind round the neck of the 

 humerus. The last offsets are the external mammary and some muscular 

 twigs. 



The superior thoracic branch is the highest and smallest offset, and 

 arises opposite the first intercostal space; it ramifies on the side of the 

 chest, anastomosing with the intercostal arteries. 



The acromial thoracic branch (fig. 70, a) is a short trunk on the front 

 of the artery, which appears at the upper border of the pectoralis minor, 

 and opposite the interval between the large pectoral and deltoid muscles. 

 Its branches are directed inwards, outwards, and upwards : 



a. The inner set supply the thoracic muscles, and give a few offsets to 

 the side of the chest to anastomose with the intercostal and other thoracic 

 arteries. 



b. The outer or acromial set end mostly in the deltoid; but one small 

 artery accompanies the cephalic vein for a short distance ; and another 

 (inferior acromial) perforates the deltoid muscle, and anastomoses on the 

 acromion with a branch of the suprascapular artery of the neck. 



c. One or two small twigs ascend to the subclavius and deltoid muscles. 

 The alar thoracic is very inconstant as a separate branch, and its place 



is taken by offsets of the subscapular and long thoracic arteries; it is dis- 

 tributed to the glands and fat of the axillary space. 



The long thoracic branch is directed along the border of the pectoralis 

 minor (fig. 70, b) to about the sixth intercostal space ; it supplies the pec- 

 toral and serratus muscles, and anastomoses, like the other branches, with 

 the intercostal and thoracic arteries. In the female it gives branches to 

 the mammary gland. 



An external mammary artery is commonly met with, especially in the 

 female; its position is near the middle of the axilla with a companion vein. 



