522 LIVING TORPEDOS IN BERLIN. 



absolutely and relatively, positive, homodromous polarisation an 

 electromotive force which may amount to that of twenty Groves 

 (pp. 453, 454)' If such a force were the cause of the superiority of 

 the homodromous current, how could it be explained that even in 

 homodromous direction, the preparation conducts worse than physio- 

 logical salt - solution, or even than frog's muscle ? It cannot 

 be maintained that the smallness of the current strength as com- 

 pared with the tremendous homodromous force is dependent on bad 

 conduction, for even the heterodromous conductivity is not bad 

 enough for that. Besides this, if the superiority of the homo- 

 dromous current depended upon polarisation, it would be impossible 

 to conceive how on the death of the organ, or on boiling it, the 

 conductivity for both currents becomes the same and then absolutely 

 increases, so that it even exceeds that of physiological salt-solution. 

 The enfeeblement of the current cannot therefore be a consequence 

 of the falling off of an electromotive force in the same direction 

 with it. 



It seems, as has already been said, impossible to escape the weight 

 of these reasons, and the existence of irreciprocal conduction in the 

 electrical organ is to be regarded as an established fact from hence- 

 forward. However, a considerable change in our conception of this 

 remarkable property of the organ is to be looked forward to. 



I now recollected that I had carried out these experiments, other- 

 wise to all appearance conclusive, with induction shocks only. It 

 occurred to me that in the series of observations mentioned above, 

 p. 503, in which the current of a Grove's battery was closed for a 

 longer period through the preparations, the superiority of the 

 homodromous current continued indeed perceptible, but by no means 

 so considerable as in the experiments with induction shocks, or with 

 battery currents of short duration. I now began to suspect that the 

 irreciprocity of conduction must depend, not only on the density 

 but also on the duration of the current, and this was found to be 

 the case. 



Instead of the secondary coil as in the previous experiments, a 

 Grove's battery was placed directly in the circuit of the gal- 

 vanometer, on the mirror of which, only 45 turns acted from a 

 suitable distance. The battery current was closed through the 

 mercury key by hand for any desired period as timed by the clock. If 

 for a short time only the contrivance mentioned above was employed 

 (p. 481, note). When required, it was exchanged for the secondary 

 coil of the inductorium, which was pushed quite up to the primary 



