Galvani and Animal Electricity

Twitching frog legs in 18th-century Bologna revealed that nerves and muscles run on electricity — sparking a feud that gave us the battery and, eventually, the action potential.

For centuries, Galen's "animal spirits" were the explanation for how nerves worked. In the 18th century, a new force — electricity — offered an alternative.

The twitching frogs

The Bologna physician Luigi Galvani (1737–1798) spent years experimenting with frog legs. He found that touching a frog's leg nerve with metal could make the muscle contract — even during a thunderstorm, or when two different metals touched the nerve and muscle. In 1791 he published De viribus electricitatis in motu musculari ("On the Forces of Electricity in Muscular Motion"), proposing that animals generate an intrinsic animal electricity, stored in muscles and conducted by nerves.

Volta's objection — and the battery

The physicist Alessandro Volta disagreed. He argued that the electricity came from the two dissimilar metals, and the frog was merely a sensitive detector. To prove it, he stacked discs of zinc and copper separated by brine-soaked cloth — and in 1800 announced the first electric battery, the voltaic pile. Both men were partly right: metals can generate current, and nerves and muscles genuinely produce electricity of their own.

Measuring the nerve signal

In the 1840s Emil du Bois-Reymond in Berlin detected the electrical "action current" travelling along nerves. In 1850 his colleague Hermann von Helmholtz measured its speed in a frog nerve: about 27 metres per second — far slower than electricity in a wire, which proved the nerve signal was a biological process, not simple conduction.

Sparks in culture

Galvani's nephew Giovanni Aldini toured Europe making the bodies of executed criminals grimace and twitch with electricity — spectacles that helped inspire Mary Shelley's Frankenstein (1818).