Bologna Frog Preparation
1791 · Galvanism · Work 221 of 1,871
Galvani's experimental apparatus on the stone balcony parapet of his Bologna house, a bimetallic arc of copper and zinc, brass hooks set into the iron railing, a laboratory notebook open at a page of diagrams beside them.
- What it was used for
- The Bologna physician and anatomist Luigi Galvani prepared frog legs, cut off at the spine, with the nerves exposed. He used them as sensitive detectors of electricity in nerve and muscle. From late 1780 he stimulated them with a friction machine, a Leyden jar and atmospheric electricity. He also saw twitches when preparations hung on brass hooks from an iron railing and the brass touched the iron. After more than ten years of experiments his 56-page Commentarius appeared in the Bologna Academy's volume for 1791; according to Marco Bresadola (University of Ferrara) it actually appeared at the beginning of 1792.
- What was new
- Galvani claimed that electricity arises inside the animal itself and drives muscle movement; he compared the muscle to a small Leyden jar. Alessandro Volta repeated the experiments from 1792. He explained the twitches by contact between two different metals and treated the frog as a mere detector. In 1794 and 1797 Galvani produced twitches with no metal at all, first with nerve and muscle, then with nerves alone. To refute him, Volta built a pile of metal plates and salt water, with no frog, that delivered a steady current; he described it in March 1800. Galvani did not live to see it: he died in December 1798, after losing his university posts for refusing the oath to the Cisalpine Republic. According to Bresadola both causes worked together: the metals gave the stimulus, the fibre's own electricity the twitch.