THE AXILLA. 



257 



with the costocoracoid membrane which goes up to the clavicle, where it splits to 

 enclose the subclavius muscle and to be attached to the anterior and posterior borders 

 of the clavicle. The upper portion of this costocoracoid membrane is thickened and 

 forms a firm band which runs from the coracoid process to the cartilage of the first 

 rib, and is called the costocoracoid ligament. 



Between this ligament above and the upper edge of the pectoralis minor below, 

 and piercing the costocoracoid membrane, are the acromiothoracic artery and vein, 

 the cephalic vein, the superior thoracic artery, external anterior thoracic nerve, and a 

 few lymphatics derived from the breast. The superior thoracic artery is often a 

 branch of the acromiothoracic and passes behind the vein to supply the serratus 

 anterior and intercostal muscles and side of the chest. 



The fascia on the under surface of the pectoralis minor unites with the layer on 

 its upper surface, and passes upward to the coracoid process and is reflected onto the 



Pectoralis major 



Axillary arch 



Intercostohumeral nerve 



Teres major and latissimus dorsi 



FIG. 269. Axillary fascia. At the apex of the axilla the fascia is almost lacking, forming a curved arch on 

 the side toward the chest, called the axillary arch or " Achselbogen." The curved edge toward the arm, less dis- 

 tinct than that toward the chest, is called the " Armbogen." 



vessels to aid in forming their sheath. It is continuous with the fascia on the under 

 surface of the subclavius muscle and the deep fascia of the neck. 



' This portion of the fascia is not sufficiently strong to form an absolute barrier 

 between the neck and axilla, consequently abscesses forming in the neck will break 

 through it and passing under the clavicle appear in the axilla, and abscesses starting 

 in the axilla may burrow under the clavicle and up beneath the deep fascia of the neck. 



THE AXILLARY VESSELS. 



The axillary artery and vein are both important. The avoidance of hemorrhage 

 in operations in this locality requires skill and knowledge, and venous bleeding is 

 more apt to be troublesome than arterial. Wounds of the vessels, whether artery 

 or vein, of those portions of the body like the axillae, groins, or base of the neck are 

 particularly dangerous; the blood current is both large and rapid. 



The axillary vein drains the whole upper extremity and part of the chest, while 

 the axillary artery carries all the blood going to those parts. The veins being so 

 much weaker and thinner walled than the arteries is the reason of their being more 

 frequently injured. Ligation of the artery, or vein, or both, may cause gangrene of 

 the extremity and require amputation. 



The Axillary Artery. The axillary artery begins at the lower border of the 

 first rib and ends opposite the lower border of the folds of the axilla (teres major). 

 If the arm is lying by the side of the body the artery describes a curve with its 



