37* VHILOSOPHY OF ZOOLOGY. 



The influence of the nerves in the production of the 

 electrical shock has been examined with care by Mr TOD, 

 and the results which have been published * throw consi- 

 derable light on the mysterious process. He made an in- 

 cision on each side of the cranium and gills of a lively tor- 

 pedo, and pushed aside the electrical organs so as to expose 

 and divide their nerves. The animal was then placed in a 

 bucket of sea-water. On examining it in about two hours 

 afterwards, he found it impossible to elicit shocks from it 

 by any irritation ; but it seemed to possess as much activity 

 and liveliness as before, and lived as long as those animals 

 from which shocks had not been received, and which had 

 not undergone this operation. Two of these animals being 

 procured, the nerves of the electrical organs of one of them 

 were divided after the manner above described. They were 

 placed each in separate buckets of sea-water, and allowed to 

 remain undisturbed. This was performed in the morning ; 

 and, when examined in the evening, it was impossible to 

 distinguish between the liveliness or activity of either. Of 

 other two of these animals, the nerves of the electrical or- 

 gans of one of them were divided. Being placed each in 

 separate buckets of sea-water, they were both irritated as 

 nearly alike as possible. From the perfect animal, shocks 

 were received : after frequent repetition, it became weak 

 and incapable of discharging shocks, and soon died. The 

 last shocks were not perceptible above the second joint of 

 the thumb, and so weak as to require much attention to 

 observe them. From the other, no shocks could be receiv- 

 ed : it appeared as vivacious as before, and lived until the 

 second day. This experiment was frequently repeated, 

 with nearly the same results. The nerves of one electric 



* jPhil. Trans. 1816, p. 120. Ibid. 1817. p. 32. 



