504 LIVING TORPEDOS IN BERLIN. 



closing 1 the homodromous current is seen to preponderate. The result 

 is obscured by two facts, first that the preparation conducts better 

 when warmed, and secondly that the negative polarisation weakens 

 the current ; nevertheless by closing the currents for a minute by 

 the hand, series are also obtained in which, in spite of all 

 hindrances, the preponderance of the homodromous current declares 

 itself plainly though feebly. Series of this nature will be com- 

 municated later (see below, 12). Dr. Sachs' investigations on the 

 organ of the Gymnotus also speak to the same effect 1 . 



Thus the question, whether the organ conducts irreciprocally in 

 reality or only in appearance, lies directly across our path, and we 

 must endeavour before all things to clear up this point. 



The first thing that presents itself, is the very striking de- 

 pendence of the phenomenon upon the current density, as is shown 

 in the following experiments. 



I sent the opening shocks of the inductorium, the primary coil 

 of which was filled with wires, through the preparation from one 

 skin surface to the other. The preparation rested in the usual 

 way on the triangular plate between the clay shields of the con- 

 ducting vessels. The galvanometer was in the same circuit. The 

 shocks, produced by opening the mercury key, were by means of 

 a Pohl's reverser, led through the preparation alternately in the 

 homodromous and the heterodromous direction. 



In the following table, C D denotes the distance of the secondary 

 from the primary coil ; the numbers are the deflections of the 

 galvanometer. The great difference of the strengths of the shocks 

 makes it necessary to put the bobbins at different distances from 

 the mirror, and the deflections are therefore reduced to 5000 turns 

 at a distance of 20 mm. 



5. Torp. Fresh. OC + 0-0031. 



CD = o 1501 | 215 f 501 4 215 f 453 j 215 I 477 I J 9 J 

 = 10 cm. | 25 f 28 | 27 f 28 j 27 f 27 



= 15 cm. t 7 4 7 t 7 I 7 



= o 1 453 1 227 



Taking the mean of the numbers of like signification, the ratio of 

 the heterodromous to the homodromous deflections is 



for CD = o : : 212-3 : 477-0 : : 100 : 224-7 

 = TO cm. :: 26-33 : 27-66 :: 100 : 105-1 

 = 15 cm. :: 7 : 7 : : 100 : 100-0. 



Hence there can be no doubt, first, that the phenomenon becomes 



1 Untersuchungen, &c., p. 218 ; p. 224 of this volume. 



