SURGICAL ANATOMY OF THE AXILLA. 133 



almost a plexus, supplying the skin of the base of the 

 axilla; together with some branches of the axillary 

 artery, the long thoracic and its veins passing downwards 

 and forwards towards the anterior inferior aspect of the 

 space, besides a considerable number of branches to the 

 glands (alar thoracic). On removing this cellular tissue 

 the walls of the axillary space can be made out. 



The internal wall, slightly convex, is formed by the 

 first four ribs and their intercostal muscles, and the first 

 five serrations of the serratus magnus, upon which lie 

 the posterior thoracic nerve, the superior thoracic, and 

 long thoracic branches of the axillary artery, with their 

 corresponding veins. The external wall, formed by the 

 scapulo-humeral region, is the most important, as on it 

 lie the great vessels and nerves in their fascial envelope ; 

 and the fact of the close adherence of these structures to 

 this wall of the axilla is of great value to the surgeon 

 in the extirpation of tumors or the opening of abscesses, 

 which fortunately as a rule lie along the inner wall. On 

 either side of the bicipital groove are inserted the ten- 

 dons of the pectoralis major and teres major, the latter 

 being internal, and a little anterior and external is the 

 tendon of the latissimus dorsi. Lying in this groove 

 and inclosed in a prolongation of the synovial mem- 

 brane of the joint is the long head of the biceps itself; 

 and most internally are seen the conjoined fibres of the 

 coraco-brachialis and short head of biceps, the inner 

 border of the former being the guide to the vessel; the 

 insertion of the tendon of the subscapularis, and origin 

 of the long head of the triceps. Above the tendon of 

 the teres major the lower portion of the capsule of the 

 joint is visible. 



The anterior wall is formed by the pectoralis major 

 12 



