ON LIVING MALAPTEKURUS. 407 



again. Tetanising evidently affected them more than the current 

 of comparatively constant density. The Malapterurus withstood 

 the effect of the constant current also, and this appears to be of 

 special interest, as it did not need to be accommodated to it. 

 However, here also, it sought that position which is theoretically 

 the most protected. 



It is now clear why the Malapterurus does not suffer from its 

 own current, and the same reason will naturally hold good for other 

 electrical fish. They all possess, at all events relative immunity 1 as 

 regards electric currents, for the exposed muscles and muscle nerves 

 of electrical fishes, and even the electrical nerves themselves are 

 excitable by the current, and consequently their immunity must 

 have a limit of current density inferior to that attained in experi- 

 ments. It would certainly be possible to kill a Malapterurus with a 

 Leyden battery of a certain size, if it were charged to sufficiently 

 high tension. Wherever this limit may lie, the difference between 

 electrical fish and other animals is great enough to be regarded as 

 one of the most enigmatical facts of physiology. According to 

 ancient accounts, crabs are said to possess immunity as regards the 

 shock of the Gymnotus 2 . .1 therefore subjected the cray-fish of 

 this country to the same experiments as the fish and the frog. 

 It is true that they bear a great deal, perhaps because their chitine 

 tunics protect them. When they are tetanised, they twitch 

 violently, their body is contorted, their antennae are laid back, but 

 there is no such immunity as that of Malapterurus. I need not 

 refer to the well-known, and in part very naive tales concerning 

 the immunity of certain men from electric shocks 3 . 



1 In M. Colladon's paper on the Torpedo, we read (p. 491) : ' M. J. Davy a 

 constatd . . . que le courant cl'une pile ne parait pas faire souffrir ceux de ces 

 poissons qui sont interposes dans le circuit.' This is a misunderstanding of Col- 

 ladon's. John Davy's statement about the absence of influence of the current on 

 the Torpedo refers solely to the electrical organs, and only assists him to conclude that 

 the organs are not muscles. (Philosophical Transactions, etc., 1832, p. 269 ; Re- 

 searches, physiological and anatomical, London, 1839, v l- * PP* 3 2 ~34-) 



2 Priestley, The History and present state of Electricity, London, 1769, p. 403. 

 G. H. Loskiel, Geschichte der Mission der evangelischen Briider unter den Indianern 

 in Nordamerika, Barby, 1 789, p. 124; also in Voigt's Magazin fur das Neuste aus 

 der Physik, u. s. w., Gotha 1789. Bd. VI. St. ii. S. 171, Loskiel's statement 

 appears the more questionable, as there are no Gymnotus in North America. Alex, 

 v. Humboldt produced convulsive movements in crabs on the Lido by the simple 

 battery (Versuche fiber die gereizte Muskel- und Nerven-faser, Berlin und Posen, 

 1797, vol. i. p. 285.) 



3 Comp. Humboldt, Versuche iiber die gereizte Muskel- und Nerven-faser, u. s. w., 

 vol. i. p. 160 ; Recueil d'Observations de Zoologie, etc., p. 69. 



