POSTERIOR SCAPULAR REGION. 231 



Posterior Scapular Region. 



Supra- spinatus, Teres minor, 



Infra-spinatus, Teres major. 



The SUPRA-SPINATUS muscle (supra, above ; spina, the spine) 

 arises from the whole of the supra-spinous fossa, and is inserted into 

 the uppermost depression on the great tuberosity of the humerus. The 

 tendon of this muscle cannot be well seen until the acromion process is 

 removed. 



Relations. By its upper surface with the trapezius, the clavicle, 

 acromion, and coraco-acromion ligament. From the trapezius it is 

 separated by a strong fascia. By its lower surface with the supra- 

 spinous fossa, the supra- scapular vessels and nerve, and the upper part 

 of the shoulder-joint, forming part of the capsular ligament. 



The INFRA-SPINATUS (infra, beneath ; spina, the spine) is cover- 

 ed in by a layer of tendinous fascia, which must be removed before 

 the fibres of the muscle can be seen, the deltoid muscle having been 

 previously turned down from its scapular origin. It arises from the 

 whole of the infra-spinous fossa, and from the fascia above-mentioned, 

 and is inserted into the middle depression upon the greater tuberosity 

 of the humerus. 



Relations. By its posterior surface with the deltoid, latissimus 

 dorsi and integument. By its anterior surface with the infra-spinous 

 fossa, superior and dorsal scapular vessels, and shoulder-joint ; its 

 tendon being lined by a prolongation from the synovial membrane. 

 By its upper border it is in relation with the spine of the scapula, and 

 by the loiver with the teres minor, with which it is closely united. 



The TERES MINOR muscle (teres, round) arises from the middle third 

 of the inferior border of the scapula, and is inserted into the lower de- 

 pression on the great tuberosity of the humerus. The tendons of these 

 three muscles, with that of the subscapularis, are in immediate contact 

 with the shoulder-joint, and form part of its ligamentous capsule, 

 thereby preserving the solidity of the articulation. They are there- 

 fore the structures most frequently ruptured in dislocation of the head 

 of the humerus. 



Relations. By its posterior surface with the deltoid, latissimus 

 dorsi and integument. By its anterior surface with the inferior bor- 

 der, and part of the dorsum of the scapula, the dorsalis scapulae ves- 

 sels, scapular head of the triceps, and shoulder-joint. By its upper 

 border with the infra-spinatus ; and by the lower with the latissimus 

 dorsi, teres major, and long head of the triceps. 



The TERES MAJOR muscle arises from the lower third of the inferior 

 border of the scapula, encroaching a little upon its dorsal aspect, and 

 is inserted into the posterior bicipital ridge. Its tendon lies immedi- 

 ately behind that of the latissimus dorsi, from which it is separated by 

 a synovial membrane. 



Relations. By its posterior surface with the latissimus dorsi, sea- 



