Frog galvanoscope

Also in the eighteenth century, Leopoldo Caldani and Felice Fontana subjected frogs to electric shocks to test Albrecht von Haller's irritability theory.

This research included the muscular response to opiates and static electricity, for which experiments the spinal cord and rear legs of a frog were dissected out together and the skin removed.

An electric machine discharged just at the moment one of Galvani's assistants touched the crural nerve of a dissected frog with a scalpel.

Galvani's wife notices the frog twitch when an assistant accidentally touches a nerve and reports the phenomenon to her husband.

Alessandro Volta opposed this theory, believing that the electricity that Galvani and other proponents were witnessing was due to metal contact electrification in the circuit.

Volta's motivation in inventing the voltaic pile (the forerunner of the common zinc–carbon battery) was largely to enable him to construct a circuit entirely with non-biological material to show that the vital force was not necessary to produce the electrical effects seen in animal experiments.

Matteucci, in answer to Volta, and to show that metal contacts were not necessary, constructed a circuit entirely out of biological material, including a frog battery.

[13] Matteucci used the frog galvanoscope to study the relationship of electricity to muscles, including in freshly amputated human limbs.

These may be made to the nerve and the foot of the frog's leg by wrapping them with metal wire or foil,[16] but a more convenient instrument is Matteucci's arrangement shown in the image.

The galvanometer was made possible in 1820 by the discovery by Hans Christian Ørsted that electric currents would deflect a compass needle, and the gold-leaf electroscope was even earlier (Abraham Bennet, 1786).

[19] Yet Golding Bird could still write in 1848 that "the irritable muscles of a frog's legs were no less than 56,000 times more delicate a test of electricity than the most sensitive condensing electrometer.

"[20] The word condenser used by Bird here means a coil, so named by Johann Poggendorff by analogy with Volta's term for a capacitor.