THE AXILLARY ARTERY 263 



ribs, the portions of the intercostal muscles corresponding, and 

 a part of the serratus magnus. The outer wall is narrow, be- 

 cause of the convergence of the anterior and posterior walls. 

 It is formed by the humerus, coracobrachialis, and coracoid 

 head of the biceps. 



This space contains the axillary vessels and brachial plexus, 

 with their branches, some branches of the intercostal nerve, and 

 a large number of the lymph nodes and vessels and much fat. 



The Axillary Artery 



The axillary artery is the continuation of the subclavian. It 

 extends from the lower border of the first rib, where it is deeply 

 placed, to the lower border of the teres major tendon, where it 

 is superficial, and there becomes the brachial. It is described 

 in three parts the first, above the pectoralis minor; the second, 

 behind it; and the third, below it. 



First Part. Relations. In front, pectoralis major, subclavius, 

 costocoracoid membrane, acromiothoracic and cephalic veins, 

 external anterior thoracic nerve; behind, first intercostal muscle, 

 first digitation of the serratus magnus, posterior thoracic nerve; 

 externally, brachial plexus; internally, axillary vein, internal 

 anterior thoracic and posterior thoracic nerves. 



Second Part. Relations. I/i/roTi^, pectoralis major and minor; 

 behind, subscapularis and posterior cord of the brachial plexus; 

 internally, vein and inner cord; externally, the outer cord. 



The posterior cord of the plexus is behind it, the outer cord 

 outside, and the inner cord to its inner side. The plexus thus 

 surrounds the second portion of the artery. 



Third Part. Relations. In front, integument, fasciae, pectoralis 

 major, median nerve, its inner head, internal cutaneous nerve; 

 behind, subscapularis, tendons of the latissimus dorsi and teres 

 major, musculospiral and circumflex nerves; externally, coraco- 

 brachialis, musculocutaneous, and median nerves ; internally, the 

 vein, brachial vense comites, ulnar and lesser internal cutaneous 

 nerves. 



Branches. First part, superior and acromial thoracic : second 

 part, long and alar thoracic; third part, subscapular and cir- 

 cumflex, posterior and anterior. 



The subscapular runs along the lower border of the subscapu- 

 laris, joining branches with the intercostal and posterior scapular 



