404 OBSERVATIONS AND EXPERIMENTS 



the shock was over, consequently the fatigue of the fish was more 

 influential than the prolongation of the time of closure by in- 

 creasing the overweight. 



But I now began other series of experiments, in which I pro- 

 posed to prove directly, the regularity introduced by the frog- 

 interrupter into the results of the fish experiments. I wished to 

 show that the mean error of a series of deflections caused by the 

 fish was diminished by the frog-interrupter. With this object, 

 I made the wires proceeding from the cover, divide into two con- 

 ductors, the one of which led to the galvanometer, guarded as usual 

 by the frog-interrupter, and the other led to an unguarded galvano- 

 meter. The guarded galvanometer, until its circuit was opened, 

 weakened the current in the unguarded one. However this could 

 have no other effect on the result, than to make the deflections in 

 the unguarded galvanometer still more irregular. I made only 

 one such experiment, but it was unsuccessful, inasmuch as the 

 guarded galvanometer, for some incomprehensible reason, gave less 

 regular deflections than the unguarded one. Soon afterwards the 

 last of my fishes died, and I remained in the dark as to the reason 

 of failure. 



11. Of the relative immunity of Malapterurus from electric 



shocks. 



As long ago as 1842, in my * Vorlaufiger Abriss,' I discussed the 

 question 1 , how it happens that an electrical fish strikes other fish 

 to death, but neither itself nor, according to v. Humboldt's 2 and 

 Colladon's 3 experience its fellows ; why the Torpedo, which is vivi- 

 parous, does not kill the young in its uterus ? I was led to this 

 question by the consideration, that according to indubitable 

 physical laws, the shock of necessity passes through the body of 

 the fish itself, in fact that this body is more favourably situated in 

 regard to the organ for the reception of the shock than the body 

 of another animal approached by it. 



This statement might perhaps be doubted in regard to the 

 Gymnotus, on account of its head being so far in front of the 

 anterior polar surface of the organ. It is certainly correct in the 

 case of the Torpedo, and it is hardly invalidated by the remark, 



1 Poggendorff's Annalen, etc., 1843, vol. Iviii. pp. 29, 30, 75. 



2 Recueil d'Observations de Zoologie, etc., p. 80. 



3 Comptes rendus, etc., t. iii. p. 490; L'Inatitut, etc., t. iv. No. 181, p. 350; 

 Poggendorff s Annalen, etc., 1836, vol. xxxix. p. 413. 



