528 



THE BLOOD-VASCULAR SYSTEM. 



and the clavicle, through which the axillary vessels and nerves pass. The base, 

 directed downward, is formed by the integument and a thick layer of fascia, the 

 axillary fascia, extending between the lower border of the Pectoralis major in front 

 and the lower border of the Latissimus dorsi behind ; it is broad internally at the 

 chest, but narrow and pointed externally at the arm. The anterior boundary is 

 formed by the Pectoralis major and minor muscles, the former covering the whole 

 of the anterior wall of the axilla, the latter covering only its central part. The 

 space between the inner border of the Pectoralis minor and the clavicle is occupied 

 by the costo-coracoid membrane. The posterior boundary, which extends some- 

 what lower than the anterior, is formed by the Subscapularis above, the Teres 

 major and Latissimus dorsi below. On the inner side are the first four ribs with 

 their corresponding Intercostal muscles, and part of the Serratus magnus. On the 

 outer side, where the anterior and posterior boundaries converge, the space is nar- 

 row, and bounded by the humerus, the Coraco-brachialis and Biceps muscles. 



Contents. This space contains the axillary vessels and brachial plexus of 

 nerves, with their branches, some branches of the intercostal nerves, and a large 

 number of lymphatic glands, all connected together by a quantity of fat and loose 

 areolar tissue. 



Their Position. The axillary artery and vein, with the brachial plexus of 

 nerves, extend obliquely along the outer boundary of the axillary space, from its 

 apex to its base, and are placed much nearer the anterior than the posterior wall, 

 the vein lying to the inner or thoracic side of the artery and partially concealing 

 it. At the fore part of the axillary space, in contact with the Pectoral muscles, 

 are the thoracic branches of the axillary artery, and along the anterior margin 



Anterior 

 circumflex. 



FIG. 302. The axillary artery and its branches. 



are the thoracic branches of the axillary artery, and along the lower margin of the 

 Pectoralis minor the long thoracic artery extends to the side of the chest. At the 

 back part, in contact with the lower margin of the Subscapularis muscle, are the 

 subscapular vessels and nerves ; winding around the outer border of this muscle is 



