THE AXILLARY ARTERY 



637 



fascia; its progress backward, by the Serratus magnus; forward, by the costocoracoid fascia; 

 inward, by the wall of the thorax; and outward, by the upper limb. The pus in these cases, 

 after extending into the neck, has been known to spread through the superior opening of the 

 thorax into the mediastinum. 



In opening an axillary abscess the knife should be entered in the floor of the axilla, midway 

 between the anterior and posterior margins and near th^ thoracic side of the space. It is well 

 to use a director and dressing forceps after an incision has been made through the skin and fascia 

 in the manner directed by the late Mr. Hilton. 



The relations of the vessels and nerves in the several parts of the axilla are important, for it is 

 the universal plan to remove the nodes from the axilla in operating for cancer of the breast. 



FIG. 460. The axillary artery and its branches. 



The Axillary Artery (A. Axillaris) (Fig. 460). 



The axillary artery, the continuation of the subclavian, commences at the 

 outer border of the first rib, and terminates at the lower border of the tendon 

 of the Teres major muscle, where it takes the name of brachial. Its direction 

 varies with the position of the limb; when the arm lies by the side of the thorax, 

 the vessel forms a gentle curve, the convexity being upward and outward; w r hen 

 the arm is directed at right angles with the trunk, the vessel is nearly straight; 

 and when the arm is elevated still higher, the arteries describe a curve the con- 

 cavity of which is directed upward. At its commencement the artery is very deeply 

 situated, but near its termination it is superficial, being covered only by the skin 

 and fascia. The description of the relations of this vessel is facilitated by its 

 division into three portions, the first portion being above, the second portion behind, 

 and the third below the Pectoralis minor. 



Relations. The first portion of the axillary artery is in relation, in front, with the clavicular 

 portion of the Pectoralis major, the costocoracoid membrane, the external anterior thoracic nerve, 



