THE MECHANICAL CHANGES OF MUSCLE 229 



when the muscle was alive, but the dead muscle does not return to 

 its original length when the weight is removed. 

 A contracted muscle, on the other hand, is more extensible than a 



FIG. 64. 



Extensibility of india-rubber (a) compared with that of a frog's 

 gastrocnemius muscle (b). 



muscle at rest. A gram applied to a tetanised gastrocnemius will 

 cause greater lengthening than if it were applied to the same muscle 

 at rest. At the same time the elasticity is more perfect that is to 

 say, when the weight is removed the muscle returns more quickly to 

 its original length. 



