406 OBSERVATIONS AND EXPERIMENTS 



.the fish died ; some sorts of fish were more easily killed than 

 others. Frogs were strongly tetanised, but recovered easily 1 . 



Now, if I put a Malapterurus in the tub instead of or along with 

 the fish, it behaved in a very different manner. By the shocks 

 which sufficed for the fatal stupefaction of the other fishes, it 

 appeared to be unaffected, just like a frog in a Guericke's vacuum 

 as compared with a guinea-pig or a linnet. If a fish or a frog 

 came too near it, it also discharged its battery, as was indicated by 

 the multiplier needle which was thrown against the stop and the 

 astaticism of which was destroyed. The only perceptible effect of 

 the shocks upon the Malapterurus was, that on opening the key, its 

 barbels were laid back, and it is worthy of remark, that the barbels 

 of the Silurus also move in a similar way when it is tetanised. 

 However, when the utmost force was imparted to the shocks, by 

 pushing the coil fully up, it was easy to see that the fish noticed 

 and avoided them. If it came in the neighbourhood of the elec- 

 trodes, where the current density was greatest, it withdrew hastily, 

 gave a shock or two, and sought with correct instinct, that position 

 in which its axis of length cut perpendicularly the least dense 

 current curves, as if it knew the laws of the distribution of current 

 in non-prismatic conductors. But it moved gills and fins with 

 usual rhythm in the midst of the strongest currents, and swam out 

 of their range without a single convulsive or involuntary move- 

 ment. 



Tin electrodes in connexion with the induction apparatus, and 

 platinum electrodes in connexion with the half length of the nerve 

 multiplier, were put on a dying Malapterurus, which lay in a small 

 parallelepiped glass trough, which it almost filled (see p. 405). 

 Even with two Groves in the primary circuit of the induction 

 apparatus and with the coil quite pushed in, the fish seemed not to 

 perceive the shocks at all, breathed on quietly and did not dis- 

 charge. A deflection in successively opposite directions now 

 presented itself. 



The result was substantially the same with the current of a 

 Grove's battery of thirty cells, in place of the alternating current 

 of the inductorium. The common river fish, whilst the key was 

 shut, lay on their side and their fins twitched. When it was 

 opened, a general convulsive movement ensued, but shortly after- 

 wards, if the current had not lasted too long, they swam about 



1 Comp. similar experiment by E. Bottger in PoggendorfFs Annalen, etc., 1840, 

 vol. 1. p. 39. 



