THE CHANGE IN FORM 331 



III 

 THE CHANGE IN FORM 



THE change in form or the contraction of muscle 

 is the most conspicuous of the several ways in 

 which its energy is set free. It has already been 

 shown that this change consists of a shortening 

 of the contractile mass followed by a return to 

 the original length. It is necessary now to de- 

 termine whether the muscle becomes smaller on 

 entering the active state or whether the altera- 

 tion in form is simply a shifting a transloca- 

 tion of the muscular units. 



VOLUME OF CONTRACTING MUSCLE 



Strip the skin from the hind limb of a frog. 

 Hang the limb from the hooked electrode in the 

 stopper of the volume tube (Fig. 58) and place 

 the stopper loosely in the tube. Hook the elec- 

 trode at the other end of the tube into the limb 

 near the foot. Pill the tube absolutely full of 

 boiled normal saline solution, slightly withdraw- 

 ing the stopper for the purpose. Eeplace the 

 stopper in the tube in such a way that all air 



