104 ANATOMY OP UPPER EXTREMITY, ETC, 



The axillary artery gives off seven branches which van 

 extremely, however, as to their precise points of origin. 

 In one case in ten, it gives off a larger branch than usual, 

 and this may be either the radial, the ulnar, the interosse- 

 ous, or a trunk from which arise the sub-scapular, the cir- 

 cumflex, and profunda arteries. The regular axillary 

 branches are 



Thoracica Acromialis, 

 Superior Thoracic, 

 Inferior Thoracic, 



Thoracica Axillaris, 

 Sub-scapular, 



Anterior and Posterior Cir- 

 cumflex. 



The thoracica acromialis emerges in the space above the border of 

 the pectoralis minor muscle and divides' into branches, which are 

 directed inward to the two pectoral muscles and outward to the 

 deltoid ; from-the deltoid set a small twig, called the inferior acromial, 

 passes down beside the cephalic vein in the interspace between the 

 pectoralis major and deltoid muscles. 



The superior thoracic (sometimes given off by the preceding artery), 

 passes along the upper border of the pectoralis minor, distributing 

 branches to the pectoralis major and mammary gland, and inosculates 

 with the branches of, the internal mammary, emerging between the 

 costal cartilages near the sternum. 



The inferior thoracic or external mammary (sometimes given off from 

 the thoracica acromialis or the sub-scapular), passes along the lower 

 border of the pectoralis minor and is distributed to the pectoralis 

 major, the mammary gland, and the serratus magnus, anastomosing 

 with the superior thoracic and with external branches of the inter- 

 costal arteries. 



The thoracica axillaris is a small artery (arising frequently from 

 one of the other branches) distributed to the nerves and arteries of 

 the axilla. 



The sub-scapular is the largest branch of the axillary artery ; it 

 passes along the lower border of the sub-scapularis muscle, supplying 

 that muscle as well as those of the lower border of the scapula, and 

 gives off a dorsal branch which, passing under its edge, is distributed 

 to the posterior surface of that bone ; this artery and its branches 

 inosculate with the posterior and supra-scapular arteries, branches of 

 the subclavian. 



To obtain a view of the two remaining branches, the deltoid muscle 

 must be divided and its two ends reflected ; in so doing a few small 

 branches of the posterior circumflex artery will be cut across. 



The anterior circumflex is a small artery, passing beneath the coraco- 

 brachialis muscle and the short head of the biceps, to wind around 

 in front of the head of the humerus : it sends a small branch along 

 the bicipital groove to the shoulder-joint. 



The posterior circumflex, much larger than the anterior, passes back- 

 ward beneath the head of the humerus, giving branches to th( 

 shoulder-joint, and also, after emerging on the other side of the bout 



