Saturday, June 19, 2010

The Discovery of ‘Animal’ Electricity


Luigi Galvani (1737 – 1798) was an Italian physician and physicist. He demonstrated what we now understand to be the electrical basis of nerve impulses when he made frog muscles twitch. In 1791 he published his theory of animal electricity in the treatise, “Commentary on the Effect of Electricity on Muscular Motion”. Galvani challenged the idea of animal spirit as the cause of nervous activity. He based his conclusion on a series of experiments on amputated frog legs. He had found that he could induce the frog’s leg to twitch by stimulating the ends of the severed nerves.

In one case, during a thunderstorm, he connected a nerve stump to a long metallic wire that pointed to the sky, and obtained muscular contractions. He also found that he could produce movements when he suspended the leg between two different metals. Although he did not know it, he had shown that when dissimilar metals make contact through a salt solution an electrical current is produced (this was the first demonstration of the battery, later formally invented by Volta in 1800).

These discoveries led Galvani to conclude that nerves are capable of conduction electricity and their ‘invisible spirit’ must be electrical in nature. He called the force that activated the muscles ‘animal electricity’. This was one of the first forays into the study of bioelectricity, a field that still today studies the electrical patterns and signals of the nervous system.


Reference:

Wickens, A. (2005). Foundations of Biopsychology (2. Ed.). USA: Prentice Hall.

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