AXILLARY BRACHIAL. 405 



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 thoracica knga 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 mam- 

 mary 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 scapular, a branch of the subclavian. It distributes branches to 

 the Subscapularis, Serratus magnus, Teres major, and Latissimus dorsi muscles, 

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

 scapulsa. This vessel 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 ; and divides into three branches, a sub- 

 scapular, which enters the subscapular fossa beneath the Subscapularis which it 

 supplies, anastomosing with the subscapular and suprascapular arteries ; an infra- 

 spinous branch (dorsalis scapulas), which turns round the axillary border of the 

 scapula, between the Teres minor and the bone, enters the infra-spinous fossa, 

 supplies the Infra-spinatus muscle, and anastomoses with the suprascapular and 

 posterior scapular arteries ; and a median branch, which is continued along the 

 axillary border of the scapula, between the Teres major and minor, and, at the 

 dorsal surface of the inferior angle of the bone, anastomoses with the supra- 

 scapular. 



The circumflex arteries wind round the neck of the humerus. 



The posterior circumflex, 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, is distributed to the Deltoid muscle 

 and shoulder-joint, anastomosing with the anterior circumflex, suprascapular, and 

 acromial thoracic arteries. 



The anterior circumflex, 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 fore part of the neck of the humerus, and, on reaching the bicipital groove, 

 gives off an ascending branch, which passes upwards along it, 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. 



BRACHIAL ARTERY (fig. 218). 



The brachial artery commences at the lower margin of the tendon of the Teres 

 major, and, passing down the inner and anterior aspect of the arm, terminates 

 about half an inch below the bend of the elbow, where it divides into the radial 

 and ulnar arteries. 



The direction of this vessel is marked by a line drawn from the outer side of 

 the axillary space between the folds of the axilla, to a point midway between the 



