Set of Perkins metal 'tractors', late 19th century.
© Science Museum / Science & Society Picture Library
Following the discovery of 'animal electricity' by Luigi Galvani (1737-1798) Elisha Perkins (1741-1799) took a growing interest in the effects of electricity and magnetism on the body. He invented pairs of metal rods, or 'tractors', one silver and one bras, which he claimed would draw out pains from anywhere in the body and could treat conditions such as numbnes, muscle weaknes, and gout. The implements were held in the hand, with the point on the skin, and used to redirect the bodies natural electricity to make the muscle twitch. Perkins and his son sold large numbers of the 'tractors' both in America and later in Europe.