498 LIVING TORPEDOS IN BERLIN. 



shocks of short duration depends. For it is difficult to imagine that 

 when a shock is once discharged, it will not reach a height corre- 

 sponding to the functional activity of the organ, independently of the 

 strength of the excitation ; and it seems just as little probable, that 

 the negative polarisation due to short sharp shocks, should exceed that 

 due to long feeble ones. According to the analogy of the polarisa- 

 tion of metal electrodes, the opposite would rather be expected. 

 This is the point in respect of which the experimental basis sought 

 for in vain in the previous paragraphs, is necessary. 



6. Unsuccessful experiments to produce relatively positive 

 polarisation by heterodromous currents. 



As I reflected upon these questions it occurred to me, that I had 

 not followed a certain path of experiment to its utmost limit, even 

 though I had not left it quite untrodden, and that it might possibly 

 lead to the goal. We have indeed laid down as a fact founded on 

 experience, that relatively positive polarisation due to the hetero- 

 dromous current, was never observed in the experiments with battery 

 currents on the Malapterurus, Gymnotus and Torpedo ; but we have 

 not hitherto undertaken experiments for the express purpose. Such 

 experiments must be designed so as to act on organ preparations by 

 heterodromous shocks as strong, and at the same time of as short 

 duration, as possible. If we should succeed in observing in this 

 way relatively positive, absolutely negative polarisation, there 

 could be no longer any doubt as to its existence, for there is no 

 reason to assume reversal of the direction of shock of the organ. 



At first, I still adhered to the use of galvanic currents closed for 

 a short time. I had indeed at an earlier date (see p. 473, Series 

 19 and 20) sent the current of 50 Groves through organ preparations 

 for a short time in vain ; more often on the contrary, when the 

 direction was homodromous, a negative preliminary shock had 

 shown itself, which it was very difficult to interpret. The period 

 of closing was o"-o629 ; I now chose a period twenty times shorter. 



4. Torp. Fresh. OC+ 0-0078. 



L. 8. I -545-35 t +45J + I 5 I -'4 



P- I 13-5; J 3 I 21 ; 20-5 4 15 



The failure could not be plainer. I now placed my hope on induc- 

 tion shocks. 



The Saxton's machine employed before, offered facility for such 

 experiments. It has a pair of T-shaped springs previously de- 



