448 LIVING TORPEDOS IN BERLIN. 



The tables in the Appendix do not require any further explana- 

 tion than has already been given in the Memoir * On secondary 

 electromotive phenomena.' The numbers in the horizontal series 

 indicated by 8, are the deflections through the secondary current, 

 those indicated by P, are the primary deflections. A glance at 

 these series, e.g. at series 10, will show that in this and the follow- 

 ing as far as 13, the homodromous current ( f ) induces both 

 absolutely and relatively positive polarisation, the heterodromous 

 current ( j ) absolutely positive and relatively negative. From 

 here onwards polarisation by both currents becomes relatively 

 negative, the heterodromous remains absolutely positive, the homo- 

 dromous becomes even absolutely negative, but is at first much 

 weaker than the absolutely positive but relatively negative polarisa- 

 tion due to the heterodromous current. As the preparation becomes 

 exhausted this difference disappears more and more. 



All the series of experiments with short currents sent in alternate 

 directions take as a rule this course. Whether the observation 

 begins with the homodromous or the heterodromous current, 

 polarisation by both currents becomes sooner or later relatively 

 negative the sooner (that is after the smaller number of alternations) 

 the longer the closing time, but if the closing time has a certain 

 duration even the first homodromous current produces polarisation 

 which is both absolutely and relatively negative. The same thing 

 occurs when the functional activity of the preparation is too small. 

 Here from the very beginning only relatively negative polarisation 

 is obtained by both currents, but the homodromous polarisation is 

 appreciably the weaker of the two. Thus the condition arises at 

 once which with a better state of the preparation only gradually 

 appears in the course of a long series of observations, viz. that ' the 

 negative polarisation-current is always stronger in the direction of 

 the shock/ 



We have thus insensibly arrived at an important result. For 



these are the words in which Sachs summed up his researches on 



homodromous and heterodromous polarisation in the Gymnotus 1 , 



and of which I had hitherto supposed and repeatedly said that they 







occupied myself for several years with such experiments, I had at length an experi- 

 mental Alarum clock made for me by Baltzar and Schmidt of Leipsic, which could 

 be set to various periods so as to indicate to the observer by the stroke of a bell 

 at intervals of I, i, i|, 2, 2$, 3$, 5 or 10 minutes, that the moment for a fresh 

 observation was come, he having been warned by another signal. 

 1 Untersuchungen, pp. 217, 218. 



