60 DISSECTION OF THE VASCULAR SYSTEM. 
20. Near the point where the axillary artery enters 
the arm it gives off a large branch from its posterior 
border which divides into three arteries : 
a. THE Lone THoracic ARTERY, a small branch 
passing along the side of the thorax and distributed 
chiefly to the pectoral and latissimus dorsi muscles. 
b. THE SuB-SCAPULAR ARTERY, a large branch dis- 
tributed to the sub-scapular muscles. 
c. The CriRcCUMFLEX ARTERY, passing obliquely 
round the humerus and distributed chiefly to the 
triceps extensor muscle of the arm. 
21. The Brachial Artery. After reaching the arm 
the axillary artery is known as the brachiai.. It gives 
off muscular branches in the arm, and at the elbow 
divides into two branches for the fore-arm. 
