THE MUSCLES. 219 



crum, is to the distance between the power and fulcrum. 

 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 sup- 

 posing c 6, to be one twentieth of the length of a b, then 

 one twentieth only of the power of the muscle is exerted 

 in raising the weight, the rest being expanded in acting 

 against the disadvantage of the position."* 



684. 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 advantage of 

 saving the muscular power. This remark applies 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 proceed 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 con- 

 sequences 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. 



685. Motions of the Radius and Ulna. Beside the 

 leverage motions of the fore-arm above described, the two 

 bones composing it, called the radius and ulna, have 

 movements peculiar to themselves. 



686. In Fig. 123, a is the radius, and 6 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. 



