492 LIVING TORPEDOS IN BERLIN. 



series of alternating- homodromous and heterodromous currents. It 

 is a matter of indifference for the preparation, whether the homo- 

 dromous currents are produced with a position of the armature in 

 azimuth 90, and the heterodromous with that in azimuth 270, or 

 vice versa. According to our hypotheses, the homodromous and 

 heterodromous currents produce equally strong relatively negative 

 polarisation, and these polarisations, which moreover on account of 

 the brief duration of the shocks attain no great extent, cancel each 

 other. But besides the relatively negative polarisation, the homo- 

 dromous currents produce absolutely and relatively positive polarisa- 

 tion, while according to our hypotheses the heterodromous produce 

 no relatively positive, absolutely negative polarisation or only 

 a trace, so that under favourable circumstances, the absolutely 

 positive polarisation due to the homodromous currents makes its 

 appearance in great force almost or entirely unmixed. The only 

 point which remains obscure, is on what the more rapid falling of the 

 homodromous polarisation after longer tetanising with congruent 

 alternating currents depends. 



4. An attempt is made to compare the negative polarisation 

 due to the closing shocks of an inductorium by themselves, 

 with that due to the opening shocks by themselves. 

 In order to judge of the secondary electromotive phenomena 

 in the electrical organ produced by incongruent alternating 

 currents, it is expedient to answer first the question, which of the 

 currents, due to the same amount of electricity equalizing itself, 

 give the strongest negative polarisation, whether the longer feebler 

 closing shocks, or the shorter stronger opening shocks? This 

 question must permit of a decided answer, by exposing an organ 

 preparation in heterodromous direction to a series of closing shocks 

 of the inductorium and to one of opening shocks alternately. In 

 connexion with this subject, I remarked that in my experiments on 

 internal polarisation of moist, porous conductors in general, I had 

 neglected to perform this experiment, apparently so simple and yet 

 so instructive; and I therefore determined to fill up this gap 

 immediately. This seemed easy of accomplishment with the aid of 

 Dove's disjunctor. 



This apparatus, which after his death also passed into the 



possession of the physiological institute 1 , consists of three pairs of 



copper wheels on a common glass axis, by rotation on which, they 



1 I had once before worked with the same apparatus, through the kindness of 



Dove, for a similar object. Unterauchungen, etc., vol. ii. part i. 1849, p. 405. 



