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178 contracted, this at once produces a disturbance, and a current flows through the galvanometer. It is not an entirely satisfactory explanation, but it is the best that can at present be given.

I shall not discuss the theories that have been propounded to explain these remarkable phenomena, the investigation of which clearly demonstrates the existence of a true animal electricity. In 1791, Galvani, who was Professor of Anatomy and Physiology in Bologna, first announced that electricity, to use his own phrase, was secreted in, or originated from, the animal tissues. The great controversy that then arose, more especially between Galvani and Volta, who was Professor of Natural Philosophy in Pavia, led to the invention of the Voltaic pile in 1799, and still more to the discovery of the production of electric currents by the contact of dissimilar metals, more especially when one is acted on chemically by certain fluids. For a long time the brilliancy of the results flowing from investigations into Voltaic electricity threw the discoveries of Galvani into the shade; but by and by, as methods of observation became more refined, it was found that there is in truth an animal