134 ELEMENTS OF PHYSIOLOGY 



226. Coordination of Several Muscles. Would you like 

 to see two persons try to thread a needle, one holding the 

 thread and the other the needle ? Would they succeed 

 well ? Or in so simple a matter as the use of the knife and 

 fork in eating, could it be easily done if one holds the piece 

 of meat with the fork while the other tries to cut it ? Why 

 is it that the right hands of two persons cannot work so 

 well together as the right and left hands of one person ? 

 It is because of the nervous connection between the hands 

 of the same person, so that one hand knows just what the 

 other is doing. Let us think of what takes place in our 

 bodies when we throw a stone at a mark. At the same time 

 we see the mark, hold the stone in the hand and throw it. 

 In throwing a stone, at least a dozen muscles are used. 

 Each one of these must contract at the right time and 

 in the right way, or the stone will miss the mark. Each 

 muscle shortens under the influence of a nerve impulse 

 brought from the brain by a motor nerve. If one muscle 

 shortens an instant too soon, or a little too much, the stone 

 goes to one side. This working together of the muscles by 

 the aid of the nerves is called coordination. Coordination 

 is necessary, even in standing erect. 



227. Nerve Expenditure. It is found that the use of 

 many small muscles is much more exhausting than the use 

 of a few larger ones. This is on account of the nerve 

 energy consumed. A drummer beating a big bass drum 

 may do more muscular work than one who plays a tune 

 softly on the piano, but the piano playing exhausts the 

 performer much sooner. This is because the movements 

 of the wrist and fingers employ thirty muscles and a great 

 number of nerves. The striking of the keys with the ends 

 of the fingers where some of the most sensitive nerves of 

 the body terminate, may have some effect also, and may 

 help to explain why so many persons, especially young 

 ladies, who take little other exercise, have become nervous 



