LIVING TOKPEDOS IN BERLIN. 431 



solution. To these others were attached similarly soaked with sea 

 water. These last were pointed, and the points projected beyond 

 the zinc pads so as to touch the surface of the fish at the spot at 

 which it was to be led off. The zinc plates were connected by 

 wires with the galvanometer, the bobbins of which possessed 5000 

 turns, at a distance of 30 mm. from the very light reflecting magnet 

 which was quite aperiodic l . If the fish gave no shock the mirror 

 was deflected only a very few degrees of the scale. These ine- 

 qualities were balanced by the round compensator. The frog- 

 alarum was brought into connection with two horizontal zinc 

 plates, one of which rested on the bottom of the glass vessel, while 

 the other just dipped into the water (see above, p. 426). I ob- 

 served the galvanometer, Prof. Fritsch who is accustomed to 

 handle Torpedos manipulated the fish, and Prof. Christiani took 

 charge of the rest of the arrangements. 



"When one point was placed upon the median and the other upon 

 the outer edge of one organ, in a line which bisected it about 

 equally, and the fish was excited, a deflection was observed almost 

 simultaneously with the sound of the frog-alarum, and this deflec- 

 tion (through the galvanometer) was always from the median to the 

 outer edge. The extent of the deflection was very unequal, e. g. on 

 one day it was 135 right and 100 left, while on another it was 100 

 right and 500 + 3; sc. left ; that is to say, in the latter case the scale 

 disappeared from the field of vision. These differences may have in 

 part arisen from differences of resistance in the circuit caused by 

 the greater or less pressure of the pointed pads ; for the most part, 

 however, they depended on the irregular efforts of the fish. When 

 deflections were observed beyond the limits of the scale it is 

 possible that several shocks occurred in such rapid succession that 

 they were confused in the frog-alarum. 



If one point was placed upon the median edge while the other 

 was placed upon the median line, deflections occurred constantly in 

 the direction previously observed, namely from the edge of the organ 

 to the median line. Thus in four cases the amount of deflection was 



Right. Left. 



1 30 



2 15 



3 20 



4 1 9sc. 



shewing as much regularity as could have been anticipated. The 



1 I used Mirror I of my first Treatise Ueber aperiodische Bewegung gedlimpfter 

 Magnete.' Lou. cit. vol. i. pp. 308, 309. 



