Galvani and Animal Electricity (1791): Frog Legs and Nerves

Luigi Galvani’s theory of animal electricity, published in Bologna in 1791, grew out of more than a decade of experiments on frog legs that twitched when touched by metal. Galvani argued that living tissue produces its own electricity and that nerves carry it to the muscles. His work founded the science of electrophysiology and provoked a famous dispute with Alessandro Volta that led to the first electric battery.

Background: electricity in the eighteenth century

By the mid-eighteenth century electricity was a popular field of research. Experimenters could store charge in the Leyden jar, and Benjamin Franklin had shown that lightning was electrical. Doctors were already giving patients shocks for paralysis, and some naturalists knew that torpedo fish and electric eels could deliver shocks of their own.

How nerves made muscles move remained a mystery. Many scholars believed in “animal spirits”, a subtle fluid flowing through the nerves. Galvani set out to test whether electricity might be that fluid.

Galvani and his laboratory

Luigi Galvani (1737–1798) was a physician and professor of anatomy at the University of Bologna, then part of the Papal States. He worked with his wife, Lucia Galeazzi, daughter of a Bologna professor, and with assistants including his nephew Giovanni Aldini. From about 1780 he used frogs because their legs, prepared with the spinal nerves attached, were very sensitive to small stimuli.

The experiments

According to Galvani’s account, a leg twitched violently when an assistant touched its nerve with a scalpel while an electrical machine nearby gave off a spark. He then explored the effect systematically. In 1786 he hung prepared frogs on iron railings with brass hooks, expecting thunderstorms to make them move. The legs also contracted on calm days whenever the hook was pressed against the iron.

Galvani found that he could produce contractions indoors simply by joining nerve and muscle with an arc made of two different metals. He concluded that the electricity was already stored in the animal, like a charge in a Leyden jar, and that the metal arc merely released it. He published his findings in 1791 in De viribus electricitatis in motu musculari commentarius.

The dispute with Volta

Alessandro Volta, professor of physics at Pavia, at first accepted Galvani’s ideas. By 1792–1793, however, he argued that the current came from the contact of two dissimilar metals, and that the frog was simply a very sensitive detector. The debate divided scientists across Europe.

Galvani and his supporters replied with experiments showing that muscles contracted with no metal at all, for example when a cut nerve was brought into contact with muscle. Volta, for his part, sought to prove that metals alone produced electricity. In 1800 he stacked discs of zinc and copper separated by brine-soaked cloth and produced a steady current: the voltaic pile, the first battery.

Later life and legacy

Galvani did not see the end of the debate. In 1797 he refused to swear an oath to the new Cisalpine Republic set up after the French conquest of northern Italy, and lost his university post. He died in Bologna on 4 December 1798.

His nephew Aldini toured Europe demonstrating “galvanism”, including a notorious 1803 demonstration in London in which electricity made the face and limbs of an executed man’s body move. Such displays fed popular fascination with reviving the dead, and in her 1831 introduction to Frankenstein (first published 1818) Mary Shelley recalled galvanism among the ideas behind the novel.

Doctors also seized on galvanism as a possible treatment. In the early nineteenth century electrical stimulation was tried for paralysis, deafness and other conditions, with mixed and often unproven results. More reliable uses came much later, in technologies such as cardiac pacemakers and nerve stimulators that rest on the same basic principle that electricity can trigger nerves and muscles.

Scientifically, Galvani was vindicated. In the 1840s Carlo Matteucci and Emil du Bois-Reymond measured electrical currents in muscle and nerve, and modern neuroscience rests on the fact that nerves transmit electrical impulses.

Myths and facts

It is often said that Galvani was simply wrong and Volta right. In reality, each had discovered something genuine: Volta the electrochemical current between metals, Galvani the electrical nature of nerve and muscle activity. Another simplification credits Galvani alone; his wife and assistants took part in the laboratory work, although their exact roles are poorly documented.

Timeline

• 1737, 9 September: Luigi Galvani is born in Bologna.
• c. 1780: Galvani begins electrical experiments on frog legs.
• 1786: Galvani observes contractions in frogs hung on iron railings with brass hooks.
• 1791: De viribus electricitatis in motu musculari is published in Bologna.
• 1792–1793: Volta begins to argue that the current comes from dissimilar metals.
• 1798, 4 December: Galvani dies in Bologna.
• 1800: Volta announces the voltaic pile.

Why it matters

Galvani’s frog legs revealed that life and electricity are linked. His work opened the study of electrophysiology, and the argument it started produced the battery, one of the foundations of modern technology. Few scientific disputes have proved so productive for both sides.