

LIVING TOKPEDOS IN BERLIN. 425 



the ventral shield, soaked with sea water, to prevent the edge of 

 the dorsal shield dd from ever touching- the ventral, the effect of 

 which would he to render the result in the experimental circuit as 

 useless as in Humboldt's and Gay Lussac's key experiment l . The 

 fish rests on the flannel, and is represented in the figure as if in 

 cross section through the organ. The dorsal shield is an arched 

 zinc plate with the edge turned up, the upper surface of which is 

 lackered, having a wooden knoh in the middle through which the 

 leading-off wire d'Hd is conducted insulated to the second handle. 

 The diameter of the dorsal shield corresponding to the median plane 

 of the fish is indicated by a red mark. I had two shields for 

 Torpedos of different sizes, the one 32 and the other 18 cm. in 

 diameter. The sea water in the vessel was in sufficient quantity 

 for its surface just to touch the back of the fish. 



5. Sluggishness of the Torpedo in confinement. 

 In the case of the Malapterurus the putting on of the shield 

 was sufficient to induce them to give shocks, and if not fatigued 

 they would give two or three in succession 2 ; if the cover was 

 pressed down upon them they would give more frequent shocks 

 with convulsive movements until exhausted. The Torpedos on the 

 contrary often failed to react when the dorsal shield was put upon 

 them, and indeed there was no certain method of exciting them to 

 give shocks when in this condition. They would allow themselves 

 to be squeezed, rubbed, pricked, pinched either on the dorsal or 

 ventral surface so far as these were accessible, without being excited 

 to action. No shock was induced even when I applied the fully 

 pushed up secondary induction coil connected with a Duchenne 

 brush, to a portion of skin which projected out of the water, 

 although at the same time the gastrocnemius of the frog-alarum 

 was tetanized. As these Torpedos had not been nearly so long in 

 captivity or kept without food as had been the case with the 

 Malapterurus, it must be assumed that there is a difference in the 

 nature of the two kinds of electrical fish. It would appear, how- 

 ever, from the statements of Walsh, Matteucci and Colladon as to 

 the behaviour of their freshly-caught Torpedos 3 , that this difference 



1 Gilbert's Annalen der Physik, 1806, vol. xxii. p. 8. Untersuchungen iiber 

 thierische Elektricitiit, vol. ii. part i. pp. 15, 105. Gesammelte Abhandlungen, 

 vol. ii. p. 695. 



2 Gesammelte Abhandlungen, vol. ii. p. 617. 



s Untersuchungen, p. 255. Matteucci, Traitd des Phe'nomenes electro-physiolo- 

 giques des animaux, Paris, 1844, P- J 45- 



