86 THE PRINXIPLE.-- OF MYOD VXAAIICS. 



77. In a given case, it was found that, 



( I.) During flexion of the fore-arm, the inser- 

 tion ot the biceps brachii approached its origin 

 about three inches. 



(2.) During flexion of the fore-arm, the inser- 

 tion of the supinator longus approached its origin 

 about seven inches. 



13.) This shows that the supinator longus has 

 more intrinsic motion than the biceps brachii : 

 It can contract more. 



78. In an}' case, when the biceps bracliii mo\"es 

 a weight in the hand, the weight moves as much 

 further than the bicipital tubercle of the radius as 

 the weight-arm of the bony lever is longer than 

 the power-arm. See Fig. 21. The proportion 

 is as follows : W-F : P-F : : D : d : In which 

 D = the dir^tance which W moves, and d = 

 the distance which P movts. 



(I.) \Miile the weight is movincr, it can do 

 more work at any one moment than the power 

 of the biceps ; because the energy of the weight 

 is proportional to the square of its velocit}- ; while 

 the energy of the power is proportional to the 

 square of its velocity ; and because the excess 



