74 TOPOGRAPHIC AND APPLIED ANATOMY. 



FIG. 29. The axilla and the lateral thoracic wall. 



Axilla. At the lower border of the subclavius muscle the vessels and nerves for the upper 

 extremity pass into the space known as the axillary cavity. This cavity is situated above the 

 axillary fossa, formed by the skin, and is a pyramidal space containing vessels, nerves, fat, and 

 lymphatic glands. We differentiate an apex, situated at the coracoid process [in most English 

 text-books the apex is said to be between the first rib, clavicle, and upper border of the 

 scapula, thus opening into the neck and permitting the passage of certain structures from the 

 neck to axilla. ED.], a base, formed by the skin of the axillary fossa, and four walls. The anterior 

 wall is formed by the pectoralis major and minor muscles. The inner wall corresponds to the 

 upper portion of the lateral wall of the thorax with the overlying serratus magnus muscle. This 

 muscle arises from the outer surfaces of the upper eight or nine ribs and is inserted into the 

 vertebral border of the scapula. Eight or ten lymphatic glands are more or less closely related 

 with this wall in the neighborhood of the three upper intercostal spaces (see Fig. 29) ; they are 

 connected with the lymphatic vessels of the breast and of the arm. Great care must be exercised 

 in removing these glands, as they are closely related to the vessels and are particularly apt to be 

 adherent to these structures when degenerated. The surgeon has to deal with these glands par- 

 ticularly in carcinoma of the female breast (see page 95). The posterior wall is formed by the 

 subscapularis and the teres major muscles which overlie the anterior surface of the scapula. The 

 subscapularis arises from the subscapular fossa and is inserted into the lesser tuberosity of the 

 humerus; the teres major arises from the axillary border of the scapula and the infraspinous 

 fascia and is inserted, together with the tendon of the latissimus dorsi, into the posterior bicipital 

 ridge. The outer wall is formed by the shoulder-joint and by the surgical neck of the humerus; 

 these structures are covered by the short head of the biceps and by the coracobrachialis. 



The axillary artery is in relation first with the posterior and then with the outer wall of the 

 axillary cavity. The pulsations of the vessel may be distinctly felt to the inner side of the promi- 

 nence caused by the coracobrachialis muscle; this is the situation in which the artery may be most 

 safely ligated by elevating the arm and keeping close to the border of the muscle. The vessel is 

 comparatively close to the shoulder-joint and is sometimes torn across in dislocations or in attempts 

 at their forcible reduction. The branches of the axillary artery are: 



1. The acromiothoracic (see page 95). 



2. The subscapular, which arises from about the middle of the axillary and consequently at 

 the mid-point between the clavicle and the lower border of the pectoralis major muscle, in which 

 latter situation the axillary becomes the brachial. The subscapular artery divides into two chief 

 branches, the dorsalis scapulae and the thoracicodorsalis [the continuation of the subscapular]. 

 The dorsalis scapula runs over the external border of the scapula to the dorsal surface of this bone, 

 supplies the surrounding muscles, and anastomoses freely with the suprascapular branch of the 

 subclavian. This is the main path for the collateral circulation when the blood-current in the 

 axillary artery is interfered with or when this vessel is ligated. The thoracicodorsalis is the largest 

 vessel of the lateral thoracic wall (see page 96). It runs down the axillary border of the scapula, 

 under cover of the edge of the latissimus dorsi, and particularly supplies the teres major, the 

 latissimus dorsi, and the serratus magnus muscles. 



