Frog galvanoscope

The frog galvanoscope is a sensitive electrical instrument used to detect voltage in the late eighteenth and nineteenth centuries. It consists of skinned frog's leg with electrical connections to a nerve. The instrument was invented by Luigi Galvani and improved by Carlo Matteucci.

The frog galvanoscope, and other experiments with frogs played a part in the dispute between Galvani and Alessandro Volta over the nature of electricity. The instrument is extremely sensitive and continued to be used well into the nineteenth century, even after electromechanical meters came into use.

Synonyms for this device include galvanoscopic frog, frog's leg galvanoscope, frog galvanometer, rheoscopic frog, and frog electroscope. The device is properly called a galvanoscope rather than galvanometer since the latter implies accurate measurement whereas a galvanoscope only gives an indication. In modern usage a galvanometer is a sensitive laboratory instrument for measuring current, not voltage. Everyday current meters for use in the field are called ammeters. A similar distinction can be made between electroscopes, electrometers, and voltmeters for voltage measurements.

Frogs were a popular subject of experiment in the laboratories of early scientists. They are small, easily handled, and there is a ready supply. Marcello Malpighi, for instance, used frogs in his study of lungs in the seventeenth century. Frogs were particularly suitable for the study of muscle activity. Especially in the legs, the muscle contractions are readily observed and the nerves are easily dissected out. Another desirable feature for scientists was that these contractions continued after death for a considerable time. Also in the seventeenth century, Leopoldo Caldani and Felice Fontana subjected frogs to electric shocks to test Albrecht von Haller's irritability theory.

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