Robert O. Becker and Andrew A. Marino, Electromagnetism and Life, SUNY Press, 1982

GALVANI'S DEMONSTRATION OF BIMETALLIC GENERATION OF ELECTRICITY

The vertebral column of the frog, with nerves attached to the muscles of the legs, rests on a plate of silver (F) with the legs on a plate of copper (G). When the experimenter connects the two plates with an iron rod, the circuit is completed, and current flows through the preparation, stimulating the nerves and producing muscle contraction in the legs. Galvani, of course, believed the source of the current to be in the animal tissues.