THE PRINCIPLES OF MYODYNAMICS. 73 



the ulna, and may be called the (iii) lateral r^e- 

 teiitive component. 



59. The resultant of e and d is marked 3 in 

 the figure : — and the resultant of 3 and b, or 

 of e, d, and b is marked 5 in the figure : Hence, 

 the force of P, that is, 5, is resolved into 3, and 

 4 : So that the lines 3 and 4 represent the two 

 general rectangular components. 



60. The lateral retentive components of the 

 inrotators of the fore -arm are greater than the 

 rotating components : Hence these muscles act 

 in a conservative manner in so far as the radio- 

 ulnar joint is concerned. 



61. A special group of muscles supinating the 

 radius comprises — the supinator brevis, the ex- 

 tensor ossis metacarpi pollicis, the extensor 

 primi internodii pollicis, and the extensor se- 

 cundi internodii pollicis. These muscles run 

 obHquely across the quadrangle of the fore-arm, 

 and have — 



(i.) Retentive components acting on the 

 radius in a proximal direction. 



(2.) Lateral components acting from without 

 inward. 



