Edward Bancroft, an American Scientist, suggests that the 'shock' from the Torpedo Fish is electrical rather than mechanical in nature.
He showed that the properties of the shock were similar to those from a Leyden jar in that it could be conducted or insulated with appropriate materials.
One experiment suspended the muscle on a brass hook inside a glass tube with a water droplet to detect movement and 'irritated' the nerve with a silver wire.
This produced movement of the muscle and it may have been due to the induction of a small electrical charge - although Swammerdam would have been unaware of this.
He demonstrates the transfer of static electrical charge to a cork ball across 150 metres of wet hemp thread.
Later he found that the transfer could be achieved over greater distances by using brass wire.
William Harvey had developed similar ideas but they were never published. De Homine (Treatise of Man); 1662: Moyardum & leffen, Leiden.
The jar is named the 'Leyden Jar' after the place of its discovery.
On removing the brain all movement stopped (which would be in keeping with Descarte's theory) but then, when the frog was dissected and a severed nerve end stimulated with a scalpel the muscles twitched.
This proved that movement of a muscle could occur without any connection to the brain and therefore the transmission of 'animal spirits' was not necessary.
He noticed that the frogs' legs twitched during lightening storms and also when the weather was fine.
He interperated these results in terms of "animal electricity" or the preservation in the animal of "nerveo-electrical fluid" similar to that of an electric eel.