36 THE SUPERIOR EXTREMITY 



Alar Thoracic. This small artery supplies the fat and lymph glands 

 in the axilla, but it is rarely present as a separate branch, and its place is 

 usually taken by twigs from the subscapular and lateral thoracic arteries. 



Arteria Subscapularis. The subscapular branch of the 

 axillary is a relatively large and comparatively short branch 

 which springs from the parent trunk at the lower border of 

 the subscapularis muscle. It descends, for about one inch, 

 along the lower border of the subscapularis, and then divides 

 into two terminal branches, the a. circumflexa scapulae, and 

 the a. thoraco-dorsalis. The circumflex scapular branch turns 

 round the axillary border of the scapula on its way to the 

 infraspinous fossa of that bone, where it anastomoses with 

 branches of the transverse cervical and transverse scapular 

 arteries. It gives numerous branches to the adjacent 

 muscles. The thoraco-dorsal branch descends along the lower 

 border of the subscapularis to the inferior angle of the 

 scapula. It gives branches to the adjacent muscles and 

 anastomoses with the lateral thoracic artery and with 

 branches from the intercostal arteries. It sends branches 

 also into the subscapular fossa which anastomose with twigs 

 of the transverse and circumflex scapular arteries, and 

 with branches of the descending branch of the transverse 

 cervical artery. 



Aa. Circumflexae Humeri, Anterior et Posterior (O.T. 

 Anterior and Posterior Circumflex Arteries). The anterior 

 and the posterior humeral circumflex arteries both arise from 

 the axillary at the same level, a short distance distal to the 

 origin of the subscapular artery. The posterior humeral cir- 

 cumflex artery is much the larger of the two. Only a small 

 portion of it can be seen at the present stage. It springs 

 from the posterior aspect of the axillary artery, and at once 

 passes backwards, with the axillary nerve, in the interval 

 between the subscapularis and teres major muscles on the 

 medial side of the surgical neck of the humerus. The 

 smaller anterior humeral circumflex artery takes origin from the 

 lateral aspect of the axillary artery, and runs laterally, in front 

 of the surgical neck of the humerus, under cover of the 

 coraco - brachialis and short head of the biceps brachii. 

 Reaching the intertubercular sulcus, it divides into two 

 branches. One of the two is directed proximally, along the 

 long head of the biceps brachii, to the shoulder-joint ; the 

 other passes laterally, to the deep surface of the deltoid, and 



