THE BRACHIAL ARTERY. 533 



Pectoral muscles, and mammary gland, and sending brandies across the axilla to 

 the axillary glands and Subscapularis ; it anastomoses with the internal mammary 

 and intercostal arteries. 



The alar thoracic 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 downward and backward 

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

 with the long thoracic and intercostal arteries and with the posterior scapular, a 

 branch of the trans versa lis colli, from the thyroid axis of the subclavian. About 

 an inch and a half from its origin it gives off a large branch, the dorsalis scapulae, 

 and terminates by supplying branches to the muscles in the neighborhood. 



The dorsalis scapulae is given off from the subscapular abouc an inch and a half 

 from its origin, and is generally larger than the continuation of the vessel. It 

 curves round the axillary border of the scapula, leaving the axilla through the 

 space between the Teres minor above, the Teres major below, and the long head 

 of the Triceps externally (Fig. 300), and enters the infraspinous fossa by passing 

 under cover of the Teres minor, where it anastomoses with the posterior scapular 

 and suprascapular arteries. In its course it gives off two sets of branches : one 

 enters the subscapular fossa beneath the Subscapularis, which it supplies, anasto- 

 mosing with the posterior scapular and suprascapular arteries ; the other is con- 

 tinued 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 posterior scapular. In addition to these, small branches are distributed 

 to the back part of the Deltoid muscle and the long head of the Triceps, anasto- 

 mosing with an ascending branch of the superior profunda of the brachial. 



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

 circumflex (Fig. 300), the larger of the two, arises from the back part of the axillary 

 opposite the lower border of the Subscapularis muscle, and, passing backward with 

 the circumflex veins and nerve through the quadrangular space bounded by the 

 Teres major and 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 and acromial thoracic arteries, and 

 with the superior profunda branch of the brachial artery. The anterior circumflex 

 Figs. 300, 302), considerably smaller than the preceding, arises nearly opposite 

 that vessel from the outer side of the axillary artery. It passes horizontally out- 

 ward 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 upward along the groove to supply the head 

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

 ward beneath the Deltoid, which it supplies, and anastomoses with the posterior 

 circumflex artery. 



THE BRACHIAL ARTERY (Fig. 303). 



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 

 vl IK i r arteries. At first, the brachial artery lies internal to the humerus ; but as it 

 passes down the arm it gradually gets in front of the bone, and at the bend of the 

 elbow it lies midway between the two condyles. 



Relations. This artery is superficial throughout its entire extent, being covered, 

 in front, by the integument, the superficial and deep fasciae; the bicipital fascia 

 separates it opposite the elbow from the median basilic vein ; the median nerve 

 crosses it at its middle ; behind, it is separated from the long head of the Triceps 

 by the musculo-spiral nerve and superior profunda artery. It then lies upon the 



