ALLESSANDRO VOLTA 165 



through the muscle. Nevertheless, the muscle contracted 

 strongly. From then on, Volta used frog preparations as a 

 test for electrification, exceeding in sensitivity the finest 

 electroscope provided with his condenser. He now touched 

 the two nerve points with two different metals, for example 

 silver and tin, which were themselves also in contact; from 

 the resulting contraction he concluded that an electric cur- 

 rent was passing through the nerve, and says that *it is clear 

 that the cause of this current is the metals themselves, and 

 that the electricity here is excited in a manner of which we 

 have hitherto had no conception.' He contrasts 'animal 

 electricity' with 'metallic electricity,' regarding the seat of 

 the electrification as being the place of contact of the two 

 metals.^ In this connection he also made an observation 

 which had already been known twenty-five years previously, 

 but which had never been suspected of having any connec- 

 tion with electrical phenomena. If we apply to the tongue 

 two different pieces of metal, we experience at the moment 

 when the two pieces of metal touch one another a sharp sense 

 of a metallic taste. Volta here at once perceived in this the 

 same effect as with the frogs' nerves, only that in place of the 

 latter, the tongue forms the moist conductor. He distin- 

 guished according to the sour or alkaline taste experienced, 

 the points of entry and exit of the current on the tongue, and 

 even used this to determine the direction of the current 

 given by different metals. ^ Using frog preparations, other 

 animal preparations, and the tongue, Volta investigated 

 many different kinds of metal and also carbon and pyrites as 

 conductors in the solid state, and he already began to arrange 

 them in a series according to their degree of activity. These 

 conductors he called conductors of the first class, and liquids, 

 such as act in animal preparations or on the tongue, 



^ The quotations are taken from Volta 's paper published in 1792. 

 ^ Volta therefore even observed, although without knowing it, the 

 chemical effects of the electric current. 



