398 OBSERVATIONS AND EXPERIMENTS 



With the help of a pair of platinum electrodes, to which a tele- 

 graph wire insulated with guttapercha served as a handle (see 

 above, pp. 380, 381), I readily observed that any point of the 

 organ nearer the tail behaves positively to any point nearer the head, 

 no matter where the point may lie on the circumference of a given 

 transverse section of the fish, whether on the back, flank, or belly. 

 The fish allowed a strip of platinum to be pushed quietly from the 

 flank under the belly without giving a shock, and only discharged 

 when the other electrode was put on it. 



It follows from these experiments, that the polar surfaces of the 

 organ lie at the head and the tail, and on account of the tubular 

 shape of the organ, the poles themselves must be sought some- 

 where in the body of the fish within the annular anterior or 

 posterior limit. It follows further, that the shocks must increase 

 with the distance of the contacts in the fish, or as we call it in 

 muscle or nerve, with the span of the leading-off arch. The result 

 confirmed this surmise. On a large Malapterurus I placed two zinc 

 saddles, first at a distance of I cm., then of 2 cm. from each other 

 at their inner edges, then so that the contacts were at the ends of 

 the organ, finally so that they touched the mouth and tail. I ob- 

 tained deflections of 20, 50, 116, 140 sc. respectively. In the last 

 experiment the fish gave two shocks, and, as I still worked without 

 the frog-interrupter, it remains doubtful whether the greater strength 

 of the effect was due only to the double shock, or also to the greater 

 difference of tension between the points from which it was led off". 



These facts had been already observed by Ranzi in Malapterurus 

 (see above, p. 388, note 2), and perfectly similar ones by Faraday 

 in the Gymnotus, but with reversed signs. But whereas De la 

 Rive remarks expressly that the anterior and the posterior halves 

 of the organ of Gymnotus discharge with precisely equal strength 1 , 

 it was found in Malapterurus that the anterior half of the organ 

 exceeds the posterior half in activity, and indeed in the ratio of 

 1 1 : 6. This ratio is very regular under ordinary circumstances, as 

 will be seen from the numbers to be given immediately. 



When I first met with this difference, I imagined that it must 

 be due to a difference of structure, perhaps to a difference in the 

 number of plates in a unit of length. But I convinced myself, in 

 common with Max Schultze, that nothing of the sort exists 2 . Then 



1 Archives de rElectricite", 1845, vol. v. p. 505; Traite" de I'Electricite" the"orique et 

 applique"e, etc., vol. iii. Paris, 1858, p. 76. 



2 Comp. M. Schultze in the Abhandlungen der naturforschenden Gesellschaft in 

 Halle, etc., he. cit. pp. 16, 17. 



