94 INTRODUCTION. 



raised further, they diminished, and finally disappeared : with still 

 further increase of current strength they reappeared, at first small, 

 but sooner or later attaining- to a constant magnitude. 



I explained the phenomenon as follows. If currents were passed 

 in a direction opposite to that of the nerve-current, evidently three 

 cases were possible. The counter-current was either smaller than, 

 equal to, or greater than the nerve-current, and therefore either 

 weakened it, reduced it to zero, or reversed it. The effect of 

 opening this counter-current was that the nerve-current suddenly 

 regained its original strength, in the first case from a diminished 

 positive strength, in the second case from zero, and in the third 

 case from a negative strength. In the first case, there was an 

 excitation of the nerve; in the second, that is when the rise of 

 current strength was from zero or near zero, no excitation 1 this 

 was the period of the hiatus ; in the third case, again an excitation. 



All these excitations observed at break, whether before or after 

 the hiatus, were, however, in reality make-excitations, the excita- 

 tion being always due to the rise of the nerve-current, either from a 

 definite positive strength, an increase of current, or from a negative 

 strength, a reversal of current. All these excitations I shall call 

 neuro-electric or nerve-current excitations. Since they occur at 

 break, and a new current is added to a previously existent current 

 of the same or of opposite direction, I shall also refer to them as 

 * additive ' in the same, or in the opposite direction. The break- 

 excitations before the hiatus are therefore additive in the same 

 direction, those after the hiatus are additive in the opposite 

 direction ; all being of course neuro-electric, and in reality break- 

 excitations. 



I may mention that about the same time as I made the investi- 

 gations referred to above, Biedermann 2 and Hering 3 came to similar 

 conclusions, they also finding that the excitation at break of an 

 exciting current is, under certain circumstances, simply a make- 

 excitation of the nerve-current. Hering has thus the credit of 

 having first appreciated, in the case of muscle, the exciting effect of 

 the nerve-current. 



In speaking of compensation of the nerve-current by counter- 

 currents, I do not, as mentioned in my previous paper, p. 7 70, refer 

 to compensation of the nerve-current in the ordinary sense : not, 

 that is to say, to currents which, as first employed by du Bois- 



1 [These observations are more fully referred to at p. 71.] 



2 Wiener Sitzungsberichte, Ixxxv. Part 3, p. 144. 8 Ibid. p. 237. 



