BONES, MUSCLES, EXERCISE, AND REST. 275 



length. Consequently, the muscles act with a disadvantage 

 of twenty or twenty-four to one. 



633. Nature makes sacrifice of power to convenience 

 of motion, to grace of structure, and to beauty of limb. 

 The muscles are therefore made very powerful. When we 

 lift a pound in the hand, and bring the fore-arm to a hori- 

 zontal position, the muscle bending the arm exerts a force 

 which would lift twenty or twenty-four pounds, if it were 

 attached to the point where the weight rests. When a 

 strong man lifts fifty or a hundred pounds with his hands, 

 holding the fore-arm in a horizontal position, the muscle 

 that raises the arm exerts a force equal to twenty or twenty- 

 four times that which would be necessary to lift the same 

 weight if it were fixed directly to the weight. 



634. The muscles that straighten the ankle, and raise 

 the body upon the toes, act with the same disadvantage 

 upon the short end of the lever. The ankle is the fulcrum, 

 the whole foot the lever, the heel the short arm, and the foot 

 in front of the ankle is the long arm. It is plain that the 

 power required to move the foot by the heel must be as 

 much greater than that which could move it by the toes as 

 the anterior part of the foot is longer than the heel, which 

 is about twelve to one. 



635. Muscular contraction is effected with rapidity 

 in some cases, almost instantaneously. This is seen when 

 the musician executes rapid pieces of music on his flute; 

 for every note that is made includes two motions of the 

 muscles on the fore-arm one to lift, and the other to 

 carry down the fingers. It is an established fact, that some 

 persons can pronounce distinctly fifteen hundred letters in 

 a minute. The pronunciation of every one of these .tetters 

 must require a distinct and double action of the muscles 

 connected with the voice and enunciation, for each action 

 includes both the contraction and the relaxation. Here are, 

 therefore, three thousand actions in one minute. Insects 

 exceed all other animals in the rapidity of their muscular 

 motions. It is calculated that, with their wings, they strike 



