SHOULDER SCAPULAR REGION 59 



separated from the teres major by the long head of the 

 triceps brachii. The teres minor is supplied by a branch 

 from the axillary nerve. It is an adductor and lateral 

 rotator of the upper extremity. 



M. Infraspinatus. This muscle arises from the whole 

 of the infraspinous fossa, with the exception of a small part 

 of it near the neck of the scapula. It also derives fibres 

 from the fascia which covers it. Its tendon of insertion is 

 closely adherent to the capsule of the shoulder-joint, and is 

 attached to the middle impression on the greater tubercle 

 of the humerus (Fig. 36, p. 84). It is supplied by the 

 suprascapular nerve, and is an adductor and lateral rotator 

 of the upper extremity. 



M. Subscapularis. The subscapularis muscle arises from 

 the whole of the subscapular fossa, with the exception of 

 a small portion near the neck of the scapula ; it also takes 

 origin from the groove which is present on the costal aspect 

 of the axillary border of the bone (Fig. 33, p. 79). Its origin 

 is strengthened by tendinous intersections, which are attached 

 to the ridges which are present on the costal surface of the 

 scapula. The fleshy fibres thus derived converge upon a 

 stout tendon, which is inserted into the smaller tubercle of 

 the humerus ; a few of the lower fibres, however, gain 

 independent insertion into the body of the humerus below 

 the tubercle. 



As the muscle proceeds laterally to its insertion, it passes 

 under an arch formed by the coracoid process and the con- 

 joined origin of the short head of the biceps brachii and the 

 coraco-brachialis. By dissecting between the upper border of 

 the muscle and the root of the coracoid process, a bursa of 

 some size will be discovered. This bursa communicates with 

 the cavity of the shoulder-joint through an aperture in the 

 capsule : in other words, its walls are directly continuous 

 with the synovial membrane of the capsule. This can readily 

 be ascertained by making an incision into it. An instrument 

 can then be passed into the joint. The subscapularis is 

 supplied by the upper and lower subscapular nerves. It is an 

 adductor and medial rotator of the upper extremity. 



Dissection. The transverse scapular artery and suprascapular nerve 

 must now be followed to their distribution on the dorsum of the scapula. 

 They have already been traced to the superior border of the scapula. 

 Divide the infraspinatus muscle about an inch and a half from its insertion, 



