492 SPECIAL METHODS OF DISCOVERY. 



liar and unexplained fact, mentioned by Aristotle about 

 341 years B.C., that the torpedo fish had the power of 

 benumbing fishes and even men, was discovered the 

 science of animal electricity. It was also by carefully 

 investigating and rightly interpreting the peculiar facts 

 discovered by Galvani that Volta discovered chemical 

 electricity. Galvanism was first discovered in the year 

 1790, as ( animal electricity,' or a peculiar form of elec- 

 tricity residing in the muscles of animals. Galvani had 

 observed that convulsions were produced in the limb of 

 a frog, whenever a spark was taken from the conductor 

 of a neighbouring electrical machine ; and subsequently 

 that two pieces of dissimilar metal in contact with the 

 limb of the frog produced a similar effect whenever 

 they were brought into contact with each other. The 

 great fact which Galvani discovered, and the importance 

 of which he did not discover, was not that of muscular 

 contraction produced by electric discharge for that was 

 well known, and had been observed by Von Kleist and 

 Muschenbroeck in 1745 but that the contractions were 

 produced by the contact of dissimilar metals. It was 

 Volta who first saw the important truth contained in 

 the latter circumstance ; and his superior insight was 

 probably due to the circumstance that he came to the 

 investigation with a properly trained mind. He had 

 studied electricity for many years, and had already in- 

 vented his well-known electrophorus and electric con- 

 denser. He soon found that the essential condition of 

 the phenomenon was the contact of dissimilar metals with 

 a moist conductor ; and that the limbs of the frog acted 

 as such a conductor, and at the same time as a very sensi- 

 tive electroscope; and he concluded that what Galvani 

 had termed ' animal electricity ' should be called 4 metallic 

 electricity.' 



