482 ARTERIES. 



it and the Pectoralis Major to the side of the chest. It supplies these muscles, 

 and the parietes of the thorax, anastomosing with the internal mammary and 

 intercostal arteries. 



The acromial thoracic is a short trunk, which arises from the fore part of the 

 axillary artery. Projecting forwards to the upper border of the Pectoralis 

 Minor, it divides into three sets of branches, thoracic, acromial, and descending. 

 The thoracic branches, two or three in number, are distributed to the Serratus 

 Magnus, and Pectoral muscles, anastomosing with the intercostal branches of 

 the internal mammary. The acromial branches are directed outwards towards 

 the acromion, supplying the Deltoid muscle, and anastomosing, on the surface 

 of the acromion, with the suprascapular and posterior circumflex arteries. The 

 descending branch passes in the interspace between the Pectoralis Major and 

 Deltoid, accompanying the cephalic vein, and supplying both muscles. 



The long thoracic passes downwards and inwards along the lower border of 

 the Pectoralis Minor to the side of the chest, supplying the Serratus Magnus, 

 the Pectoral muscles, and mammary gland, and sending branches across the 

 axilla to the axillary glands and Subscapularis, which anastomose with the 

 internal mammary and intercostal arteries. 



The thoracica alaris is a small branch, which supplies the glands and areolar 

 tissue of the axilla. Its place is frequently supplied by branches from some 

 of the other thoracic arteries. 



The subscapular, the largest branch of the axillary artery, arises opposite the 

 lower border of the Subscapularis muscle, and passes downwards and backwards 

 along its lower margin to the inferior angle of the scapula, where it anastomoses 

 with the posterior scapula, a branch of the subclavian. It distributes branches 

 to the Subscapularis, Serratus Magnus, Teres Major, and Latissimus Dorsi mus- 

 cles, and gives off, about an inch and a half from its origin, a large branch, the 

 dorsalis scapulae, which curves round the inferior border of the scapula, leaving 

 the axilla in the interspace between the Teres Minor above, the Teres Major 

 below, and the long head of the Triceps in front. Three branches, or sets of 

 branches, arise from the dorsalis scapula ; the first enters the subscapular fossa, 

 beneath the Subscapularis, which it supplies, anastomosing with the subscapular 

 and suprascapular arteries ; the second, the trunk of the artery (dorsalis scapulse) 

 turns round the axillary border of the scapula, and enters the infraspinous fossa, 

 where it anastomoses with the suprascapular and posterior scapular arteries ; 

 and a third, or median branch, is continued along the axillary border of the 

 scapula, between the Teres Major and Teres Minor, and, at the dorsal surface 

 of the inferior angle of the bone, anastomoses with the posterior scapular. 



The circumflex arteries wind round the neck of the humerus. The posterior 

 circumflex (Fig. 283), the larger of the two, arises from the back part of the 

 axillary, opposite the lower border of the Subscapularis muscle, and, passing 

 backwards with the circumflex veins and nerve, through the quadrangular space 

 bounded by the Teres Major and Teres Minor, the scapular head of the Triceps 

 and the humerus, winds round the neck of that bone, and is distributed to the 

 Deltoid muscle and shoulder-joint, anastomosing with the anterior circumflex, 

 suprascapular and acromial thoracic arteries. The anterior circumflex (Figs. 283, 

 284), considerably smaller than the preceding, arises just below that vessel, from 

 the outer side of the axillary artery. It passes horizontally outwards, beneath 

 the Coraco-brachialis and short head of the Biceps, lying upon the forepart of 

 the neck of the humerus, and, on reaching the bicipital groove, gives off an 

 ascending branch, which passes upwards along the groove, to supply the head 

 of the bone and the shoulder-joint. The trunk of the vessel is then continued 

 outwards beneath the Deltoid, which it supplies, and anastomoses with the 

 posterior circumflex, and acromial thoracic arteries. 



