OF MOVEMENT IN ANIMALS. 



37 



a clip ; at eacli of its dilatations the muscle will force open 

 the clip, and this movement may be registered. This method 

 enables us to study the phenomenon of the muscular wave, 

 and the speed with which it travels throughout the whole 

 length of the muscle. 



Fig. 7 exhibits a bundle of muscle held at two points 

 of its length between the myographical clips, 1 and 2. 

 Those instruments are so constructed that when their ends 

 are pushed apart by the dilatation of the muscle, the move- 



G. 7. Disposition of a bundle of muscle between two pairs of myo- 

 graphical clips. Clip No. 1 holds the electric excitators of the mnscl'-. A 

 wave is represented at the moment when it has just crossed each ot the 

 clips. 



ment compresses a sort of little drum which sends a portion 

 of the air which it contained through an india-rubber tube 

 into a similar little drum. Fig 1 . 7 shows two of these instru- 

 ments fixed upon a foot. The expansion of the membrane 

 lifts a registering lever, and thus gives notice of the dilatation 

 of the muscle at the point where it is compressed by clip 

 No. 1. The movement is shown upon the tracing- by a curve 

 analogous to those which we have already seen. 



