38 



ANIMAL MECHANISM. 



Let us suppose that the muscle is electrically excited at 

 the level of the first clip ; notice is given of the formation of 

 the wave at that part of the muscle, but clip No. 2 does 

 not yet give its signal. In order that it may act, the wave, 

 as it passes along the muscle, must reach it. As this occurs, 

 clip No. 2 gives the signal in its turn, and it is shown by 

 the tracing, that this second movement is later than the first 

 by a certain space whose duration may be estimated according 

 to the speed of the rotation of the cylinder. 



The influences which modify the intensity and the duration 

 of the muscular shock have appeared to us to modify the 

 intensity and the speed of the propagation of the wave. Thus 

 the two lower curves represented in Fig. 8 show that the 

 transference of the wave is retarded by cold. 



Fig. 8.— Two determinations of the speed of the muscular wave. 



The experiment has been made upon the muscles of the 

 thigh of a rabbit. The clips were placed as far as pos- 

 sible apart, about seven centimetres. Electricity was applied 

 to the lower extremity of the muscle, and the two upper curves 

 of Fig. 8 were obtained. The interval which divides those 

 curves marks the duration of the transference of the muscular 

 wave. After the muscle had been chilled with ice the curves 

 at the bottom of the figure were obtained. We see that the 

 transference of the wave is slackened, for there is a longer 

 interval between these curves than between the first. 



Production of mechanical force in the muscle. — We have seen 

 that chemical action is the source of muscular. force ; through 



