One of the greatest figures in the history of technology was an amphibian. Numerous frogs were martyred to the discovery of bioelectricity and the invention of electrocardiography. Frogs also played a supporting role in the development of the first source of continuous current, a turning point in the study of electricity.
In my
History of Wireless, I discuss the “animal electricity” experiments of Luigi Galvani and his debate with Alessandro Volta, driving the latter to construct his “voltaic pile.” Galvani noticed that a frog’s crural nerve could be stimulated wirelessly to create a muscle contraction. This was first demonstrated indoors using a static electricity generator and then outdoors during lightning storms. Later, Galvani discovered he could trigger contractions merely by completing a circuit containing dissimilar metals, though he stubbornly refused to acknowledge that the source of electricity was external to the frog.
Galvani’s mistake drove Volta to perform further experiments demonstrating dissimilar metals can be used to generate electricity. (However, Volta failed to see that a chemical reaction rather than mere contact was the cause.) Armed with Volta’s invention, natural philosophers were empowered to make a series of further discoveries.
Was Luigi Galvani the first person to encounter wireless communication via electromagnetic waves? Close examination of Galvani’s research papers (as explained in the December 1971 issue of
IEEE Spectrum by L.A. Geddes and H.E. Hoff) reveals that the muscle contractions in his first “wireless” experiments were due to electro-static induction. In his book
The Ambiguous Frog, Marcello Pera shows that lightning storms also triggered contractions via electro-static induction. Galvani happened upon a wireless effect, but it was not due to electromagnetic waves. (This is not as odd as it might seem: in the late 19th century Joseph Henry, William Preece, and Oliver Lodge all pursued wireless communication via magnetic induction, which also does not involve electromagnetic waves.)
Galvani lost the debate with Volta but is now rightly considered the discoverer of bioelectricity. His work inspired Carlo Matteucci, who invented the “rheoscopic frog”—a severed sciatic nerve and its innervated gastrocnemius muscle that could be used as a sensitive electricity detector. In 1856, Kolliker and Mueller used the rheoscopic frog to observe the electrical activity associated with the beating heart of another frog.
The rheoscopic frog was crucial to the development of electrocardiography. Though early researchers had galvanometers for detecting and measuring electrical current, the response time of those devices was too slow for observing the heart’s electrical activity. The rheoscopic frog was the best electrical test and measurement instrument available for that purpose—until it was replaced decades later by the capillary electrometer and then the string galvanometer.
