LIVING TOBPEDOS IN BERLIN. 449 



contradicted my results with Malapterurus 1 . Now that I con- 

 stantly observed the same thing in the Torpedo that Sachs did in 

 the Gymnotus, and at the same time saw how the phenomenon 

 came into existence, scales fell from my eyes. Not only is there no 

 contradiction between our results and those formulated by Sachs in 

 the above words, but both can be deduced from one very simple 

 assumption ; and as my results with Malapterurus are also in accord- 

 ance with the same assumption, it may be asserted that in all three 

 electrical fish the secondary electromotive phenomena are essentially 

 the same, and in a certain sense are understood. 



We are further led to this assumption by the observation that in 

 all my experiments on Malapterurus and Torpedo the heterodromous 

 current never induced relatively positive polarisation. Even polari- 

 sation in two directions, first relatively negative and then positive, 

 is only seen in the homodromous currents. Let it be supposed 

 that both currents polarise relatively negatively in equal degree, 

 but that the strength of the homodromous current is so much 

 greater than that of the heterodromous that the relatively positive 

 heterodromous polarisation is constantly masked by the relatively 

 negative, and all becomes clear as may be seen in Fig. 17. 



The assumptions under which this figure is drawn, are similar to 

 those which illustrate Sachs' results in Table II of the book on 

 Gymnotus. The diagram represents shortly what happens in a 

 series of experiments in which, as in the series given in the Appen- 

 dix, the two currents are sent alternately through a portion of the 

 organ. The abscissal axis of course marks the time. The ordi- 

 nates in each section correspond to the moment of closure of the 

 galvanometer after the opening of the battery circuit. Above the 

 abscissal axis they express positive polarisation and below it 

 negative. The ascending arrow means that, the current being 

 homodromous, the course of the curve of polarisation above the 

 abscissal axis is absolutely and relatively positive, and below the 

 abscissa absolutely and relatively negative. The descending arrow 

 implies that, the current being heterodromous, the course of the 

 curve of polarisation if above the line is absolutely positive, rela- 

 tively negative, and if below it, absolutely negative, relatively 

 positive. The resulting polarisation current which acts upon the 

 galvanometer is represented in each section by the shaded space 

 which lies between the curve resulting from the algebraic sum- 

 mation of both polarisations and the axis. 



1 Sitzungsberichte, vol. i. p. 395. 

 Gg 



