THE PRINCIPLES OF MYODYNAMICS. 85 



The triceps brachii, the flexors on the fore-arm, 

 the extensors on the fore-arm, the supinator 

 longus, and the pronator radii teres. It is evi- 

 dent that the supination of the radius aids in 

 causincr this dislocation. 



75. This dislocation is the more possible, be- 

 cause the shaft of the ulna is almost wholly, as 

 it were, back of the condyles of the humerus, 

 and because the coronoid process, at times, is 

 somewhat readily lifted from the trochlea by the 

 impact of violence and the force of displacing 

 components : — when the radius is carried with 

 the ulna, assisted by displacing muscular com- 

 ponents. 



76. In regard to the stability of the elbow- 

 joint, the following statements may be made : 



(i.) When the fore-arm is completely ex- 

 tended, the radio-humeral joint is in a condition 

 of maximum stability. 



(2.) When the fore-arm and the arm meet at 

 a right angle, the ulno-humeral joint is in a 

 condition of maximum stability. 



(3.) The elbow-joint has less stability than the 

 wrist-joint. 



