294 THE CIRCULATORY SYSTEM. 



e. A. axillaris (Fig. 122, g). The axillary artery is the 

 continuation of the subclavian laterad of the first rib. It lies 

 caudad of the brachial plexus and parallel to it. It sends off 

 the following branches : ' 



1. A. thoracica anterior (Fig. 122, //). The anterior 

 thoracic is a slender artery which leaves the ventral side of the 

 axillary opposite the first rib and passes caudomediad, to supply 

 the medial ends of the pectoral muscles (g). 



2. A. thoracica longa (/). The long thoracic artery is 

 larger than the preceding, leaves the axillary a short distance 

 laterad of it, and passes caudad to the middle portions of the 

 pectoral muscles (s) and continues to the inner surface of the 

 latissimus dorsi. 



A short distance beyond the long thoracic the axillary 

 divides into two. The more cranial one of these is the sub- 

 scapular (/); the other is the brachial (g'}. 



3. A. subscapularis (/). The subscapular artery passes 

 laterad and gives off a short distance from its origin the 

 A. thoracicodorsalis (/) and A. circumflexa humeri posterior 

 (see below) ; it may also give rise to the circumflexa anterior 

 humeri (/'), and to the profunda brachii (); these two 

 branches, however, rise more frequently from the brachial 

 artery (g") and are described in connection with it. The sub- 

 scapular artery then passes through the triangular interval 

 between the scapular end of the long head of the triceps, the 

 latissimus dorsi, and the glenoid border of the scapula. Within 

 this interval it sends muscular branches to the long head of the 

 triceps, the subscapularis, and the latissimus dorsi. That to 

 the latter muscle is very large. At the border of the scapula, 

 opposite the tuberosity of the spine, it turns craniad, passes 

 over the lateral surface of the infraspinatus muscle, supplying 

 it ; crosses the spine, and sends branches into the supraspinatus 

 fossa in both directions parallel to the scapular spine. These 

 supply the supraspinatus, acromiotrapezius, and spinotrapezius, 

 and anastomose with the branches of the transversa scapulse. 

 As the subscapularis turns craniad onto the surface of the infra- 

 spinatus it sends dorsad a small branch, the circumflexa 

 scapulae, which passes in the infraspinatus fossa close to its 



