LIVING TORPEDOS IN BERLIN. 497 



the case of single shocks, to arrange for a uniform closure of the 

 galvanometer circuit after each individual shock. 



All this demands a special investigation, for which I have not 

 leisure at present. In regard to the question how the negative 

 polarisation in the electrical organ behaves for closing and opening 

 shocks, we must be content with the simplest assumption in the 

 mean time, viz. that it is proportional to the amount of electricity, 

 and thus is the same for the two shocks. 



5. Continued discussion of the results of polarisation of 

 the organ by alternating currents. 



The result of polarising the organ by the alternating currents of 

 induction apparatus, can be readily explained by means of the last- 

 mentioned hypothesis in conjunction with the indubitable fact, that 

 when the direction is homodromous, strong currents of short dura- 

 tion produce stronger absolutely and relatively positive polarisation 

 than weaker currents of long duration. For here also, as with the 

 congruent alternating currents of Saxton's machine, the relatively 

 negative polarisations in both directions cancel each other : since 

 the heterodromous shocks produce no relatively positive polarisa- 

 tion or only infinitely little, the homodromous absolutely positive 

 polarisations alone remain, and these prove to be stronger with 

 homodromous strong shocks of short duration than with homo- 

 dromous weak shocks of long duration. 



It is another question, how much these experiments have contri- 

 buted to decide whether the homodromous absolutely positive 

 polarisation is only an after-effect of a shock, or an independent 

 phenomenon. This decision is not such as I had expected. I had 

 overlooked the circumstance that the relatively negative polarisa- 

 tions due to both currents may cancel each other, but not, as I had 

 assumed, the relatively positive ones, because, if there are any such at 

 all in the organ, the heterodromous current does not produce them, 

 or only produces traces of them. ' Thus it was an error, when I sup- 

 posed, that tetanising in itself would leave behind it no polarisation, 

 so that an absolutely positive effect produced by it must be conceived 

 of as solely an after-effect of shocks. If the observed results have 

 any bearing on our question, it is rather in the opposite sense. It 

 has been seen that, to express myself briefly, according to the polari- 

 sation theory the phenomena are not difficult to explain ; whereas 

 the after-effect theory fails to explain on what the weak absolutely 

 positive polarisation with heterodromous direction of the stronger 



Kk 



