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. 



(Sitbacromio-trochiterius.) 



(Fig, 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-hiovieralis 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 



