ARTERIES OF THE THORAX AND ARM. 353 



is distributed principally to the ental surface of the M. latissi- 

 mus ( 635). 



941. A. circumflexa (Fig. 102, 105, A. crcm). After the A. 

 thoracica longa has been traced, cut through the pectoral mass and 

 the M. epUrocTilearis ( 681) along the caudal edge of the M. biceps, 

 that is, nearly parallel with the humerus. Turn the muscles aside, 

 and there will be exposed the vessels and nerves of the brachium. 

 About opposite the trochiu (Fig. 45, B) the axillary artery will be 

 found to divide into two slightly unequal parts (Fig. 102, 105). The 

 largei- of these, the bracTiial artery, continues along the arm ; the 

 other, the common trunk of the circumflex and subscapular arteries, 

 proceeds toward the surgical neck of the humerus for about 1 cm., 

 when it divides into the branches just named. 



The circumflex passes between the subscapularis and teres mus- 

 cles in company with the circumflex nerve (Fig. 105) ; it winds dor- 

 sally around the surgical neck of the humerus and is distributed to 

 the triceps muscles, and its terminal branches pass to the eutal 

 aspect of the M. clavo-deltoideus. Demonstrate these by separating 

 the acromio- and clavo-deltoid muscles and raising the cephalic bor- 

 der of the latter. Branches of the circumflex artery and nerve will 

 be seen ramifying on its ental aspect. 



942. A. subscapularis (Fig. 102, 105, A. sbscp.). This arises 

 in common with the circumflex, as stated above ( 941); it passes 

 somewhat laterad and is distributed principally to the structures in 

 the subscapular fossa (Fig. 44). Several branches are furnished, 

 however, to other structures, viz., MM. latissimus, meditriceps and 

 dermo-Jiumeralis. This artery and its branches are best followed 

 after section of the axillary vessels and nerves. 



943. A. brachialis (Fig. 102, 105, A. br.). This is the artery 

 of the brachium. It is a direct continuation of the A. axillaris per- 

 ipherad of the origin of the common trunk of the circumflex and 

 subscapular ( 941-2). Isolate it with the tracer by tearing away 

 connective tissue. The median nerve and brackial vein lie ectad 

 of it and should be removed or turned aside. In its course along 

 the caudal side of the arm, the brachial gives rise to several un- 

 named muscular branches and the following named branches : 



(A) A. circumflexa anterior (Fig. 105. It is the small vessel passing between s and p 

 of " N. m. spiralis "). It passes to the caudal margin of the M. biceps, and then sends a 

 branch proximad to the head of the humerus. 

 23 



