78 ANIMAL MECHANICS 



Here A represents the muscle, B the lever, and 

 C the fulcrum. The power of the nruscle is not 

 represented by the distance of its insertion a, 



from the fulcrum 

 C. The hue which 

 truly represents 

 the lever must pass 



__M from the centre of 



FIG. 21. 



motion, perpendic- 

 ularly to the line of the tendon, viz., C 6. Here, 

 again, by the direction of the tendon, as well as 

 by its actual attachment to the bone, power is lost 

 and velocity gained. 



We may compare the muscular power to the 

 weight which impels a machine. In studying 

 machinery, it is manifest that weight and velocity 

 are equivalent. The handle of the winch in a crane 

 is a lever, and the space through which it moves, 

 in comparison with the slow motion of the weight, 

 is the measure of its power. If the weight, raised 

 by the crane, be permitted to go down, the wheels 

 revolve, and the handle moves with the velocity 

 of a cannon-ball, and will be as destructive if it 

 hit the workman. The weight here is the power, 

 but it operates with so much disadvantage, that 

 the hand upon the handle of the winch can stop 

 it : but give it way, let the accelerated motion 

 take place, and the hand would be shattered which 

 touched it. Just so the fly-wheel, moving at first 



