368 A MANUAL OF ANA TOMY. 



The Infraspinatus. Fig. 76. 



Origin. From the under surface of the spine of the 

 scapula, from the inner two-thirds of the posterior surface 

 of the scapula reaching from the spine to the origin of the 

 teres muscles, and from the inner surface of the infraspinous 

 fascia. 



Insertion. Into the middle facet upon the greater tuber- 

 osity of the humerus, and into the capsular ligament of the 

 shoulder-joint. 



Nerve Supply. The same as the supraspinatus. See 

 above. 



Action. Primarily it is an external rotator of the arm ; 

 if the arm is extended and drawn forward the muscle will 

 adduct and extend it slightly. 



The Teres Minor. Figs. 76, 77. 



Origin. From the upper two-thirds of the posterior 

 surface of the axillary border of the scapula, and from the 

 septa between it, the teres major, and infraspinatus muscles. 



Insertion. Into the lowest facet upon the greater tuber- 

 osity, and into the shaft of the bone for an inch below. 



Nerve Supply. The circumflex. The filaments are fur- 

 nished by the fifth cervical nerve. 



Action. An external rotator and adductor of the arm. 



The Teres Major. Figs. 76, 77. 



Origin. From the lower third of the posterior surface of 

 the axillary border, and from the posterior surface of the 

 inferior angle of the scapula, and from the septa which in- 

 tervene between it and the teres minor and the infraspinatus 

 muscles. 



Insertion. By a tendon nearly two inches broad into the 

 inner bicipital ridge of the humerus. 



