SHOULDER SCAPULAR REGION 85 



joint, facilitates the movements of the proximal end of the 

 humerus on the inferior surface of the arch ; it has already 

 been noted (p. 78). 



Dissection. Clear away the subacromial bursa and clean 

 the supraspinatus, following it below the coraco-acromial arch 

 to its insertion into the greater tubercle of the humerus. Then 

 clean the fascia from the surface of the subscapularis ; it is a 

 fairly strong fascia and, near the vertebral border of the scapula, 

 some of the fibres of the serratus anterior are usually inserted 

 into it. Now turn the limb on its anterior aspect and remove 

 the strong fascia which covers the posterior surfaces of the 

 infraspinatus, the teres minor and the teres major. Divide 

 first the fascia over the infraspinatus. Incise it from the 

 vertebral border of the scapula to the greater tubercle of the 

 humerus. Reflect the upper part to its attachment to the spine 

 of the scapula and the lower part to the septum which separates 

 the infraspinatus from the teres minor and major muscles. 

 Then clear the fascia from the teres minor and major muscles. 

 As the septum between the teres minor and the infraspinatus 

 is being investigated be careful to avoid injury to the circumflex 

 scapular artery. The scapular muscles may now be examined. 



M. Supraspinatus. The supraspinatus muscle arises from 

 the medial two- thirds of the supraspinous fossa, and also, 

 to a slight degree, from the supraspinous fascia, which covers 

 it. From this origin the fibres converge, as they pass laterally, 

 and, proceeding under the acromion, they end in a short, 

 stout tendon, which is inserted into the uppermost of the three 

 impressions on the greater tubercle of the humerus (Fig. 45, 

 p. 107). The tendon is closely adherent to the capsule of the 

 shoulder-joint. A portion of the supraspinatus is covered by 

 the trapezius, and in the loose fat which intervenes between 

 that muscle and the supraspinous fascia some twigs of the 

 ascending branch of the transverse cervical artery ramify. 

 The supraspinatus is supplied by the suprascapular nerve ; and 

 it is an abductor of the arm. 



M. Infraspinatus. The infraspinatus 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 derives 

 fibres also 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. 48, p. 113). It is supplied by the 

 suprascapular nerve ; and it is an adductor and lateral rotator 

 of the arm. 



M. Teres Minor. The teres minor is the small muscle 

 I 6 a 



