CHAP. 1. VOLTA. 5 



were not denied; the dispute arose as to the ex- 

 planation of them, and the controversy that succeeded 

 is one of extreme interest. Amongst other import- 

 ant results,, the following ftmdamental facts were 

 established. One by Galvani, who shewed that 

 when a circuit is formed by means of any conducting 

 substance, whether metals or not, between the nerve 

 and the muscle, muscular contractions are produced 

 in the muscles supplied by that nerve, and that the 

 contractions may be produced even when the free 

 end of the nerve alone, touches the external surface of 

 the muscle. The other by Volta, who shewed that 

 the contractions were the greatest when two hete- 

 rogeneous metals were employed to complete the 

 circuit, and that contractions would also be pro- 

 duced when a portion of the nerve . alone was 

 included withia the circuit. Galvani explained the 

 effects, by supposing that the muscles acted as 

 reservoirs of electricity, similar to a charged Leyden 

 jar, electricity being formed by the brain; (over- 

 looking the possibility, pardonable at his time, that 

 other parts as well as the brain might produce 

 electricity ;) and that the inner and outer smfaces of 

 the muscles being in opposite electric states, when 

 the circuit was completed the contraction of the 

 muscle ensued, in consequence of the reunion of 

 the electricity of the two surfaces. Volta, on the 

 other hand, considered that the effect was due to 

 the electricity which was developed by the mere 

 contact of the heterogeneous metals, or other sub- 



