In 1838 there was brought to London, and exhibited at the Adelaide Gallery, in the Strand, a living specimen of the electric eel, or gymnotus, being the first received in this country alive within the present century. It was fed upon fish, and occasionally with bullock's blood, and was kept warm by water, artificially heated. With this eel several interesting experiments were made, allowing periods of rest from a week to a month between each set. One of these is thus described:—

"I was so fortunate (says Professor Owen) as to witness the experiments performed by Professor Faraday on the large gymnotus which was so long preserved at the Adelaide Gallery, in London. That the most powerful shocks were received when the one hand grasped the head, and the other hand the tail of the gymnotus, I had painful experience, especially at the wrists, the elbow, and across the back. But our distinguished experimenter showed us that the nearer the hands were together, within certain limits, the less powerful was the shock. He demonstrated by the galvanometer that the direction of the electric current was always from the anterior parts of the animal to the posterior parts, and that the person touching the fish with both hands received only the discharge of the parts of the organs included between the points of contact. Needles were converted into magnets; iodine was obtained by polar decomposition of iodide of potassium; and availing himself of this test, Professor Faraday showed that any given part of the organ is negative to other parts before it, and positive to such as are behind it. Finally, heat was evolved, and the electric spark obtained."