sometimes fell to twitching even when the sky was quite clear and there
was no sign of thunder. His natural conclusion was that this must be
due to hitherto unnoticed electrical changes in the atmosphere.
Observations maintained for hours every day, however, led to no
conclusive result; when twitchings did occur it was only with some of
the specimens, and even then there was no discoverable cause. Then it
happened one day that Galvani, 'tired out with fruitless watching',
took hold of one of the brass hooks by which the specimens were hung,
and pressed it more strongly than usual against the iron railing.
Immediately a twitching took place. 'I was almost at the point of
ascribing the occurrence to atmospheric electricity,' Galvani tells us.
All the same he took one of the specimens, a frog, into his laboratory
and there subjected it to similar conditions by putting it on an iron
plate, and pressing against this with the hook that was stuck through
its spinal cord. Immediately the twitching occurred again. He tried
with other metals and, for checking purposes, with non-metals as well.
With some ingenuity he fixed up an arrangement, rather like that of an
electric bell, whereby the limbs in contracting broke contact and in
relaxing restored it, and so he managed to keep the frog in continuous
rhythmical movement.

Whereas Galvani had been rightly convinced by his earlier observations
that the movement in the specimens represented a reaction to an
electric stimulus from outside, he now changed his mind. In the very
moment of his really significant discovery he succumbed to the error
that he had to do with an effect of animal electricity located
somewhere in the dead creature itself, perhaps in the fashion of what
had been observed in the electric fishes. He decided that the metal
attachment served merely to set in motion the electricity within the
animal.