LIVING TORPEDOS IN BERLIN. 461 



slowly decline in strength with a regularity which perfectly cor- 

 responds to the nature of the shock and the functional activity 

 of the preparation, and finally fade away, affords no countenance 

 to the impression that we have here to do with a process of dis- 

 charge allied to muscle twitch. 



This is the place to mention a point not yet expressly dealt 

 with, and which, although of great importance, has not been by 

 any means sufficiently explained in strict relation to facts, namely, 

 the dependence of absolutely positive polarisation on current den- 

 sity. Although I had long believed that the threshold of current 

 density for the generation of this polarisation must be high, I only 

 discovered too late with the preparations from the last fish sacri- 

 ficed, that under certain circumstances even the currents from one 

 Grove generated absolutely positive polarisation, with the pecu- 

 liarity, however, that this effect speedily came to an end, a fact 

 which had probably deceived me before. If now the number of 

 elements was suitably increased, the ordinary effects reappeared 

 (Series i). The variable phenomena which pressed upon me were 

 so numerous that I was unable to come to a certain conclusion. A 

 very curious movement of the mirror recurred from time to time with- 

 out my being able to penetrate into its meaning, still less to produce 

 it at will, namely, that the image of the scale instead of retreating 

 from the maximum deflection as usual was thrown back with a jerk. 



A method of experiment suggested itself to me too late, by the 

 aid of which, when I have again Torpedos at my disposal, a 

 successful discrimination between the two conceptions of absolutely 

 positive polarisation which have been contrasted with each other, 

 ought to be possible. The experiment consists in tetanising the 

 organ preparation by alternate currents instead of subjecting it to a 

 single current impulse. I began at once to set this going by 

 closing the secondary circuit 1 of the inductorium with the 

 ' Wippe ' instead of the battery circuit. If the absolutely positive 

 polarisation is nothing more than the after-effect of the shock, it 

 ought to appear with the greatest possible strength after tetanising 

 for a short time. This was, however, not the case. Even when 

 the induction was extremely strong, with the ordinary arrange- 

 ment of the inductorium only weak polarisation followed, the direc- 

 tion of which was such as would have resulted from exclusively 

 opening shocks ; that is to say, the polarisation was absolutely and 

 relatively positive when the opening shocks were homodromous, 



1 See p. 489, note. 



