OF THE MUSCLES. 223 



crum, is to the distance between the power and ful- 

 crum. In the present case, therefore, the power of the 

 muscle is to the effect produced by it, as a b is to c b ; 

 and supposing c b to be one twentieth of the length of 

 a b 9 then one twentieth only of the power of the muscle 

 is exerted in raising the weight, the rest being expended 

 in acting against the disadvantage of the position."* 



We shall, however, find that it is a general fact, or 

 law of the animal economy, that muscular power is 

 always sacrificed to convenience. Had the object been 

 to raise the weight with the least possible power, the 

 muscle would have been placed on the fore arm, and the 

 tendon inserted into the lower part of the arm bone, but 

 in this case the awkwardness of the limb would have 

 much more than counterbalanced the supposed advan- 

 tage of saving the muscular power. This remark ap- 

 plies with still greater force to the fingers, which are 

 now moved by the contraction of muscles placed on the 

 fore arm, and from which small delicate tendons pro- 

 ceed along both sides of the hand, to be inserted into 

 the several ranks of bones. Now had this order been 

 reversed, and the muscles placed on the fingers, by 

 which the greatest mechanical advantage would have 

 been gained, the consequences would have been, a hand 

 so clumsy as to have been nearly useless, and not only 

 so, it would have been, when compared with its present 

 delicate and beautiful form, an absolute deformity. 



Motions of the Radius and Ulna. Besides the lever- 

 age motions^ of the fore arm above described, the two 

 bones composing it, called the radius and ulna, have 

 movements peculiar to themselves. 



In Fig. 123, a is the radius, and b the ulna, both of 

 which are articulated to the humerus, as formerly shown 

 in Fig. 65. 



Suppose the muscle of the hand had been so placed as to have given 

 that organ the greatest mechanical power what would have been the result 

 in its form and usefulness ? 



* Bostock's Physiology, vol. i. p. 186. 



