124 CHANGE IN FORM IN A MUSCLE WHEN IT CONTRACTS [CH. X. 



power of a lever, though a gain in the rapidity and extent of the 

 movement. 



Most muscular acts involve the action of several muscles, often 

 of many muscles. The acts of walking and running are examples of 

 very complicated muscular actions in which it is necessary not only 

 that many muscles should take part, but also must do so in their 

 proper order and in due relation to the action of auxiliary and 

 antagonistic muscles. This harmony in a complicated muscular 

 action is called co-ordination. 



By the device of taking instantaneous photographs at rapidly 

 repeated intervals during a muscular act, the details of different 

 modes of locomotion in man and other animals have been very 

 thoroughly worked out. With this branch of research the name 

 of Prof. Marey is intimately associated. 



