52 



ANIMAL M1:CHAN1SM. 



increased since Ch. Robin has shown that all the species of 

 the genus ray have electrical apparatus and functions in a 

 more or less rudimentary condition. Besides, the analysis 

 of this singular act, which is called the electric discharge^ has 

 been better studied, as physicists have themselves learned the 

 different properties of the electric agent. 



In the 1 8th century, they said, when speaking of the torpedo, 

 that ^'this fish when it is touched throws out a kind of 

 venom which paralyses and benumbs the hand of the fisher- 

 man." Muschenbroeck, in the last century, ascertained the 

 electrical nature of the torpedo's discharge. Walsh, in 1778, 

 saw plainly that the numbness produced by this animal differs 

 in no respect from that which is caused by the discharge of an 

 electrical machine. He proved by a great number of experi- 

 ments, that the effect produced by this fish is manifestly 

 electrical. He subjected the discharge to a series of trials, 

 in which it had the same effect as the electricity deve- 

 loped by machine. For instance, he showed that the animal 

 might be touched with impunity, by taking as a medium of 

 communication non-conductors of electricity. Besides, he made 

 the discharge pass through a chain of individuals holding each 

 other by the hand, and all felt the same singular effect which 

 is produced by the Ley den jar. 



At a later period Davy obtained with the current of the 

 torpedo the deflection of the galvanometer, the magnetization 

 of steel needles placed within a spiral of brass wire traversed 

 by the discharge, and the decomposition of saline solutions. 



Becquerel and Breschet verified the same facts in the wire 

 of the galvanometer, the current circulating from the back to 

 the belly of the animal. 



The demonstration of the spark came still later. Father 

 Linari and Matteucci obtained this spark by breaking in 

 various ways a metallic circuit through which the current of 

 the torpedo was passing. The most ingenious process is that 

 of Matteucci, who made use of a file in the following manner : 

 A metallic plate attached to a brass wire is fixed under the 

 belly of the torpedo ; on its back is placed a file on which the 

 end of a metallic wire rubs. The animal is then irritated, 

 and one or even several sparks are seen in the dark to pass 



