THE BRACHIAL OB AXILLARY ARTHBIES. r^ 649 



The inferior branch (thoracica acromialis of Man) descends in the interspace 

 comprised between the mastoido-humeralis and the anterior deep pectoral muscles, 

 accompanying the cephalic vein ; it is distributed to these two muscles, and super- 

 ficial and anterior superficial pectorals. 



7. SuPEA-scAPULAE OE Peescapulae Aeteey (Fig. 375, 13). 



This is a small and slightly tortuous vessel, which arises from the axillary 

 artery, a little before it reaches the tendon of the subscapularis muscle. It is 

 directed upwards, and enters the space included between that muscle and the 

 supra-spinatus, after sending off some divisions to the anterior superficial pectoral 

 muscle. Its terminal branches are expended in the inferior extremity of the 

 supra- and infra-spinati muscles, the tendon of the biceps, and in the articulation 

 of the shoulder. 



8. Infea-scapulae oe Subscapulae Aetery (Fig. 376, 2). 



This artery is remarkable for its considerable volume ; it arises at a right 

 angle from the axillary artery, at the space separating the subscapularis from the 

 teres major muscles. Its origin indicates the limit artificially fixed between the 

 brachial trunk and the humeral artery. It is seen to proceed upwards and back- 

 wards in this interspace, within the caput magnima, until near the dorsal angle 

 of the scapula, where it terminates. 



It gives off on its track : 



1. An artery which, following the inferior border of the latissimus dorsi 

 muscle, ascends to its inner face, throwing off twigs into the substance of the 

 muscle, as well as into the panniculus carnosus. 



2. The scapulo-humeral, or posterior circumflex artery of the shoulder, which 

 passes from within that articulation, beneath the caput magnum, to reach its 

 external face. After giving off some collateral branches, it arrives, with the 

 circumflex nerves, underneath the abductors of the arm, where it breaks up, like 

 its sateUite nerve, into several divergent branches destined to the three muscles 

 above named, the oblique flexor and short extensor of the forearm, and to the 

 mastoido-humeralis and panniculus carnosus. 



3. Muscular hranches, which escape at intervals during the course of the 

 vessel, and are sent forwards and backwards. The anterior pass either to the 

 internal or external side of the scapula, or to both sides of that bone, the posterior 

 border of which they embrace in their bifurcation. The internal divisions creep 

 in the fissures on the deep face of the bone, throwing their ramuscules into the 

 subscapularis muscle, and even reaching the supra-spinatus, as well as the inser- 

 tion of the angularis scapulte and serratus muscles. The external divisions 

 traverse the caput magnum, to be distributed to the supra- and infra-spinati and the 

 abductor muscles of the arm — one furnishing the nutrient arteiy of the scapula. 

 Y\xQ posterior branches supply the abductor of the arm, and the caput magnum. 



Humeral Artery, or Terminal Artery of the Brachial Trunk (Fig. 376). 



Course. — This vessel is a continuation of the axillary artery, which changes 

 its name after giving off the subscapular branch. At first it describes a slight curve 

 forwards to descend almost vertically to the inside of the thoracic Umb, by 

 crossing obliquely the direction of the humerus, and terminates above the 



