236 EXPERIMENTS relating to 
‘* and as the circulation of the Leyden phial fuppofes two con- 
“* trary electricities, the one more condenfed or pofitive, and 
“‘ the other lefs fo or negative, fo Profeifor Gatvani concludes, 
“ that a fimilar diftinétion takes place in the bodies of animals, 
“ and that one of thefe ele@tricities, to wit, the condenfed or 
“ pofitive, is feated in the nerves, and the other in the mufcles*.” 
Hence both of them have conceived it neceflary, to eftablith 
a communication between the nerve and the mufcle, by means 
of metalline coating of the nerve and pieces of metal and me- 
talline conduétors ; or by coating the nerve with lead or tin, 
then laying one piece of filver in contac with the tin, and ano- 
ther in conta@t with the mufcle; and, in the laft place, efta- 
blifhing a communication between the two pieces of metal, or 
between the nerve and the mufcle, by means of a brafs- -wire, 
which they term a conductor’ f. 
But, inftead of this complex apparatus, I have found, from 
the above experiments, that the mufcle is thrown into aétion, 
although no metal is direly in contact with it, or when the 
communication between the metals and the mufcle is made by 
the nerve alone. 
Ir appears therefore, that Profeffor Ganvant and Dr VALLI 
have allowed preconceived theory to conduct their experiments, 
inftead of allowing their experiments to conduét their theory ; 
in confequence of which, feveral of their experiments have 
been performed with lefs accuracy than might have been ex- 
pected. Thus, they tell us, that if the condudtor is firft applied 
to the mufcle, the convulfions are {tronger than when it is 
firft applied to the nerve; that the {hocks are ftronger when the 
feet communicated with the earth, tc. whereas the application 
of the conductor to the mufcles, or of the feet to the earth, are 
quite out of the queftion. 
2. We 
%* See Medical Facts and Obfervations, Lond. 1792. p. 187, 188. 
+ Ditto, p. 187. 191, 21I~ 
