THE SHOULDER MUSCLES. 



577 



It passes laterally along the lower border of the infraspinatus to be inserted into the 

 capsule of the shoulder-joint and into the lower facet of the greater tuberosity of the 

 humerus. 



Nerve-Supply. — By the circumflex nerve from the fifth and sixth cervical 

 nerves. 



Action. — When the arm is vertical, it rotates the humerus outward ; when it 

 is horizontal, it draws it backward. 



Supraspinatus 



Spine of 

 scapula 



Infraspinatus 



Subscapularis 1 



Fig. 561. 



Clavicle 



Teres major 



Sectional surface of 

 acromion 



Supraspinatus 



Greater tuberosity 



Teres minor 



Quadrilateral space 

 Tendon of latissimus dorsl 



Y Triangular space 



_ \ Long (middle) head of 



triceps 



Outer head of triceps 



Latissimus - 

 dorsi 



-Triceps 



h 



\ v.--' 



Posterior scapular muscles and part of triceps ; outer part of acromion has been removed. 



4, Teres Major (Figs. 561, 572). 



Attachments.— The teres major arises from the dorsal surface of the scapula, 

 along the lower third of its axillary border, and passes laterally to be inserted into the 

 crest of the lesser tuberosity of the humerus immediately dorsal to the insertion of 

 the latissimus dorsi. 



Nerve-Supply. — By the lower subscapular nerve from the fifth and sixth cervi- 

 cal nerves. 



Action.— To draw the arm backward and medially, at the same time rotating it 

 inward. 



Relations.— The teres major is in relation below with the latissimus dorsi, which 

 bends around its under surface so as to lie ventral to it at its insertion. Above it is 

 in relation with the teres minor at its origin, but separates from it as it passes later- 



37 



