60 THE UPPER EXTREMITY 



taking care not to injure the subjacent vessels. Pull the muscle cautiously 

 backwards, and its nerve of supply with the terminations of the transverse 

 artery of the scapula and the circumflex artery of the scapula will be 

 exposed. Treat the supraspinatus muscle in a similar manner (Fig. 37, 

 p. 86). 



Arteria Transversa Scapulae (O.T. Suprascapular Artery). 

 This vessel enters the supraspinous fossa by passing over the 

 ligament which bridges across the incisura scapularis. It 

 divides, under cover of the supraspinatus muscle, into a supra- 

 spinous and an infraspinous branch. The former supplies the 

 supraspinatus muscle, and gives off the chief nutrient artery 

 to the scapula ; the latter proceeds downwards in the great 

 scapular notch, and under cover of the inferior transverse 

 scapular ligament, to reach the deep surface of the infra- 

 spinatus muscle to which it is distributed. 



At the superior border of the scapula the transverse artery 

 of the scapula gives off a branch (ramus subscapularis] which 

 enters the subscapular fossa under cover of the subscapularis 

 muscle. 



Nervus Suprascapularis (Suprascapular Nerve). This 

 nerve accompanies the transverse artery of the scapula, but 

 it enters the supraspinous fossa by passing through the incisura 

 scapulae, under cover of the upper transverse ligament of the 

 scapula. It supplies the supraspinatus, and ends in the infra- 

 spinatus muscle. It usually sends two articular twigs to the 

 posterior aspect of the shoulder-joint, viz. one while in the 

 supraspinous fossa, and the second as it lies in the infra- 

 spinous fossa. 



Arteria Circumflexa Scapulae (O.T. Dorsalis Scapulas 

 Artery). This vessel has already been observed to arise from 

 the subscapular branch of the axillary and enter the triangular 

 space. While there it supplies one or two ventral branches, 

 which pass under cover of the subscapular muscle to the 

 subscapular fossa, and a larger infrascapular branch which 

 runs downwards in the interval between the teres major and 

 teres minor to the inferior angle of the scapula (Fig. 21, 

 p. 51). After these branches are given off, the circumflex 

 scapular artery leaves the triangular space by turning round 

 the axillary border of the scapula, under cover of the teres 

 minor. It now enters the infraspinous fossa, where it ramifies 

 and supplies branches to the infraspinatus muscle. 



Anastomosis around the Scapula. An important and free 

 anastomosis takes place around the scapula. Three main 



