264 On the Effects of Certain Physical and 



the silver on the muscles, as in fig. 6, we apply the zinc and 

 silver on the nerves, as in fig. 7, the eff'ects are precisely the 

 same. 



Ex. 10. If, instead of preparing the frog in the manner de- 

 scribed, we merely divide the spinal marrow, and suspend the 

 animal so that its two inferior extremities may penetrate into 

 two glasses or cups, nearly filled with pure water ; and if we 

 connect the water of these glasses or cups with the two ends 

 of a Cruickshanks' trough, of from five to ten or twenty cells, 

 also filled with pure water, the first institution of the current 

 is attended by energetic mviscular actions ; if the current be 

 now continued for five or ten minutes, and then be interrupted 

 and renewed, similar actions are observed, but in a far less 

 mai'ked degree ; after a time they cease altogether, no mus- 

 cular actions being observed on breaking and remaking the 

 circuit. But that the nerves are in an electrogenic condition 

 is proved by reversing the wires, and the direction of the 

 current ; on making the circuit, muscular contractions are 

 observed as at first, until, at length, they cease in their turn. 



These phenomena may be repeated again. The experi- 

 ment was first made by Yolta, and its results have been de- 

 signated the " alternatives Voltaiques." It has been especi- 

 ally observed by Signor Matteucci. 



Having, in this manner, produced the electrogenic effect 

 in the limbs of a frog, I endeavoured, by disconnecting the 

 Voltaic circuit, and connecting the two portions of water in 

 which those limbs were separately suspended, to produce ob- 

 vious muscular contractions, but in vain ; it was only when 

 one of the wires attached to the trough was touched by the 

 platinum discharger, that very slight movements were ob- 

 served. 



This fact pi'oves, either that the muscular fibre is only ex- 

 citable through the medium of its nerve, or, which seems im- 

 probable, that it is, like the nerve, in every respect and degree 

 susceptible of electrogenic induction. 



Hitherto, I have refrained from noticing the slight differ- 

 ences observed in the two legs, afi'ected by spasmodic and 

 tetanoid action. This question is, however, illustrated by 

 the following experiment. 



