214 ELECTRO-PHYSIOLOGY < HAP. 



the muscle perceptibly later. Let the make excitation be 

 maximal; if the twitch which it induces begins in the 

 muscle before the terminal excitation arrives there, summation 

 of the two twitches must ensue there is " supramaximal " 

 contraction. The time-relations of the two curves harmonise 

 with this conclusion. 



Fick found, in the course of an experiment on the latent 

 period of twitches with increasing intensity of current, that the 

 first (considerably reduced) contraction after the breach showed " an 

 enormous prolongation of latent excitation." This cannot be due 

 to diminished strength of stimulation immediately after the breach, 

 for, even when the twitches after considerably exceed those 

 antecedent to it, the latency in the former is measurably greater 

 than in the latter. This sharp distinction between the twitches 

 before and after the breach determines them not to be perfectly 

 homogeneous. It has been pointed out by Waller (56) that the 

 latency of break twitches with the constant current is much 

 greater than that of the make twitches, and Biedermann confirms 

 this fact. If the twitches after the breach, as well as those 

 which bridge it with falling strength of current, really correspond 

 with the break twitches of the constant current, we should a 

 priori expect them to exhibit the same characteristics in regard 

 to the latent period. 



Summing up the previous data, it may be stated with great 

 probability that " The twitches before the breach are discharged 

 by the impact of an induction current (shock) ; these have a brief 

 latent period ; the twitches after the breach, as well as the twitches 

 which bridge it with diminishing intensity of stimulus, are 

 caused by the disappearance of the brief current. These, like 

 all opening twitches, have a long latent period in comparison 

 with the closure contraction. When, with falling strength of 

 current, the point is reached at which the inhibition at the 

 positive pole can no longer hinder the transmission of the 

 excitation to the muscle, the short latency (suddenly) reasserts 

 itself" (Tigerstedt). 



If certain " supramaximal " twitches thus depend upon sum- 

 mation of the anodic and kathodic excitation, we may expect to 

 demonstrate the same by separating the two stimuli so far in time 

 that the interval should be at least as great as the latent period 

 of the contraction. This, according to Tick and Lamansky, could 



