214 MYOLOGY. 



Relation. Externally with the scapular fascia; anteriorly 

 with the pectoralis parvus ; posteriorly with the scapular spine 

 and the anterior border of the postea-spinatus ; internally with 

 the bone ; antero-inferiorly with the levator humeri and the 

 tendon of the flexor brachii. 



Action. To extend the humerus on the scapula, and tense 

 the fascia covering the flexor brachii. It serves, like the other 

 scapular muscles, as an active ligament of the shoulder joint. 



POSTEA-SPINATUS. 

 (Subacromio-trochiterius.) 



(Fie. 78. 6.) 



Lodged in the postea-spinatus fossa, it is broad, flat, and 

 triangular, with the apex below, to which its fibres converge ; it 

 is fleshy, with strong tendinous intersections. 



Origin. From the posterior costa and fossa of the scapula, 

 the posterior border of its spine, and the cartilage of prolongation. 



Insertion. By two divisions, one of which goes to the inner 

 side of the convexity of the external humeral trochanter ; the 

 other, a strong tendon, passes over the trochanter, and is inserted 

 to a roughened ridge below. Between the tendon and convexity 

 is a synovial bursa. 



Relation. Externally with the aponeurosis of the teres ex- 

 ternus and with the scapular fascia; anteriorly with the antea- 

 spinatus and the scapular spine ; posteriorly with the teres 

 externus ; internally with the scapula, its cartilage, and the 

 postea-spinatus minor ; inferiorly it contacts the capsular ligament 

 of the shoulder joint. 



Action. To abduct the humerus, and rotate it outwards. 



POSTEA-SPINATUS MINOR. 



(Scapulo-humeralis Parvus.) 



(FiG. 80. a a.) 



Situated on the inside of the teres externus, below the postea- 

 spinatus, and along the posterior border of the scapula, it is long 

 and prismatic inferiorly, fleshy, and intersected by tendon, and 

 is easily divided into a large and small portion. 



Origin. From the posterior border of the scapula, and by 



