158 SPECIAL ANATOMY. 



VII. Muscles of the Upper Extremity. 

 A. On the Scapula. 



285. 1 . Deltoideus, Jlttollens humeri. 



Pos. : envelopes like a cap the head of the upper arm and its 

 superior third ; beneath the skin ; anterior, external to and behind 

 the shoulder joint, separated from it by a tendinous layer ; covers 

 the tendons of pectoral, major and minor, coraco-brachialis, 

 biceps, infraspinatus, teres minor, triceps brachii, Vasa et Nn. 

 circumflexi humeri. The anterior border is separated from the 

 external border of pectoral, major by Vena cephalica. Or. : 

 Spina scapulas, Jlcromion, Pars acromialis claviculse (as M. 

 cucullaris). Ins. : with three tendons to the extremity of Spina 

 tuberc. majoris oss. humeri, almost in its centre. Use: 1. the 

 central fibres raise the arm directly outwards and upwards ; 2. 

 the anterior forwards; 3. the posterior backwards. The arms 

 being fixed (as in climbing), it draws the scapulae towards them. 

 Antagonist: m. cucullaris. 



Nerves : axillaris [circumflexus]. 



286. 2. Supraspinatus. 



Pos. : in the/<ma supraspinata, below lig. coraco-acromiale, 

 over the roof of the shoulder joint, covered by M. trapezius ; 

 above Vasa and Nn. supra scapular es. Or. : fossa supraspinata 

 (the two internal thirds). Ins. : tuberculum majus (at the highest 

 point). The tendon is connected with the articular capsule, sepa- 

 rated from that of m. subscapularis by cap. long, bicipitis. Use. : 

 assists in elevation of the arm and rotation outwards. 



Nerves: suprascapularis. 



287. 3. Infraspinatus . 



Pos. : below the spine on the posterior surface of the scapula, 

 covered by latissimus dor si, cucullaris, and deltoid., and a strong 

 fascia. Or. : fossa infraspinata (the entire surface). Ins. : tu- 

 berculum majus (the central fossa) ; connected with supraspin. 

 and teres minor. Use : to rotate the arm outwards. 



Nerves: suprascapular. 



288. 4. Teres Minor. 



Pos. : on the external border of the scapula, behind the Cap. 

 long. m. tricipitis, before Vasa and Nn. scapular, super, above 

 upon the capsule of the shoulder, covered by deltoid. Or. : mar go 



