How did Luigi Galvani compare muscles and nerves to a Leyden jar?

Luigi Galvani proposed that animal tissue functioned similarly to a Leyden jar, a device used to store static electricity.12

In his theory of "animal electricity," Galvani hypothesized that the brain acted as an organ to secrete an "electric fluid," which was then conducted by the nerves to the muscles. He compared the nerves and muscles to the inner and outer surfaces of a Leyden jar, suggesting that these tissues could store and discharge this vital electrical force to stimulate muscular contraction.2

While Galvani was correct that electrical stimuli cause muscles to contract, his specific analogy and his belief in an innate "animal electricity" were challenged by Alessandro Volta. Volta argued that the electricity originated from the contact between dissimilar metals rather than from the animal tissue itself, a debate that ultimately led to the development of the voltaic pile.23