242 NEW CLASSES OF GALVANTf CONDUCTORS. 



and placing very irritable organs in the way of the discharge, 

 tempted m **" Aftei " several fruitless attempts,- I arrived at the following 

 vain. combination, the success of which has never since disap- 



pointed me, and perhaps furnishes an interesting datum for 

 the general theory of the electric charge. 

 Successful ex- Let a powerful pile be perfectly insulated, and its two 

 flames be united in one insulated as perfectly. Prepare as 

 speedily as possible the hinder extremities of a frog, so thlit 

 the ischiatic nerves shall be disengaged from the rlefh, and 

 from the spine, the lumbal' vertebra? of which are removed. 

 Place the muscles on the negative pole of the pile, letting 

 the nerves hang down freely ; and, holding an exciting arc- 

 by a completely insulating handle, apply one extremity to 

 the flame, and the other to the nerves. By this no contrar- 

 Cautions. tiou will be occasioned : or should there by chance be some 



traces of contraction, as in fact has occurred to me, though 

 very rarely, these must be considered as exceptions pro- 

 duced either by the defective insulation of the handle, a 

 mere mechanical irritation of the very susceptible nerves, or 

 by the action of the atmospheres of the poles ; for I have 

 found in another series of experiments, that every pole, 

 charged by the contact of the opposite pole, becomes the 

 centre of a sphere of activity, in which the capacity of sub- 

 stances is powerfully modified without contact, and solely 

 by the mechanism of electric influences. 

 This may ac- I am tempted to explain by the last mentioned property 

 sparks be'ui" tl 10se sparks, which observers of credit affirm they have ob- 

 obtained by tained by the contact of a single pole, when the pile con- 

 tie contact of s j st j n p - thousand pairs possessed verv great energy: and 

 a single pole. . [ . . 



I conceive, that the contractions sometimes seen in the case 



in question result from the weak positive electrisation, which 

 the negative pole produces by its influence on the exciting 

 arc, so that the equilibrium is restored not between the po- 

 sitive and negative poles, to which the flame presents an in- 

 surmountable obstacle, but between the negative pole and 

 the anterior part of the insulated arc, become positive by 

 influence. li. is obvious, that the effect of this restoration 

 of equili b/iii m must be ©f infinitely small intensity; and 

 that, to produce the weakest contractions, it supposes an ex- 

 traordinary degree of excitability. 



Be 



