Ill 



ELECTRICAL EXCITATION OF MUSCLE 



283 



It is obvious from these tables that, as v. Bezold found, very 

 weak constant currents actually increase the excitatory effect of 

 single induction currents sent through the entire intrapolar area, 

 provided they are in the same direction. The numbers quoted 

 show, moreover, that the increase in height of twitch is much 

 more significant than was formerly observed by v. Bezold. This 

 is in great measure owing to the fact that the otherwise unavoid- 

 able and rapid decrease of intensity in the weak polarising current 

 is prevented by the use of unpolarisable electrodes. 



An essential difference, however, between these results and 

 those of v. Bezold appears when the effect of duration of current 

 upon the consequences of test excitation are taken into considera- 

 tion. While, i.e. v. Bezold found on application of a polarising 

 current that the height of the twitch discharged by an induction 

 shock increased perceptibly with the duration of the constant 

 current (notwithstanding the disadvantage of progressive polarisa- 

 tion from the metallic electrodes), we have never experienced 

 this. Eather, when the battery current was at first of very low in- 

 tensity, so that no visible sign of excitation appeared at the moment 

 of its entrance into the muscle, the height of the augmented 

 twitches discharged by a homodromous induction current, did not 

 alter perceptibly, provided the polarising current was not closed 

 for too long a period. On the other hand, a more or less pro- 



