In 1791, while working at Bologna University, Luigi Galvani discovered that the muscle of a frog contracted when touched by a metallic object. This phenomenon became known as animal electricity, as the theory was later disproven. Prompted by these experiments, Volta initiated a series of experiments using zinc, lead, tin or iron as positive plates. Copper, silver, gold or graphite was used as negative plates. In 1800, after extensive experi-mentation, he developed the voltaic pile. The original voltaic pile consisted of a pile of zinc and silver discs and between alternating discs, a piece of cardboard that had been soaked in saltwater. A wire connecting the bottom zinc disc to the top silver disc could produce repeated sparks.
Volta built different piles using thirty, forty or sixty elements. This enabled him to study the action of the pile on the electric fluid, depending on the number of elements. He confirmed that the electric shock increased in intensity with the number of elements used in the pile.
