92 THE PRINCIPLES (3F MYODYNAMICS. 



may have displacing components acting on the 

 humerus. 



(2.) The infraspinatus, the subscapularis, and 

 the teres minor may have downward displacing 

 components acting on the humerus. 



(3.) The coraco-brachialis and the short head 

 of the biceps brachii and the long head of the 

 triceps brachii may have small inward displacing 

 components acting on the humerus. 



86. Some of the muscles that span the 

 shoulder-joint have large displacing components 

 acting on the humerus. These are the pec- 

 toralis major, the teres major, and the latissimus 

 dorsi, and the deltoid : 



(i.) The lower part of the pectoralis major 

 deserves special attention : (i) It has a large 

 myodynamic angle giving a large displacing 

 component acting downward. (ii) It pulls 

 almost directly inward and forward, in the 

 direction of the conjugate diameter of the glenoid 

 cavity, (iii) Hence, the lower part of the pec- 

 toralis major has a predominant displacing com- 

 ponent acting on the humerus, forward, inward, 

 and downward. 



