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UNITED STATES - MAY 27: Clarke's-type machine patented by Davis and Kidder and made by W H Burnap of Lowell, Massachusetts. It has a horseshoe magnet, two rotating bobbins and pulley wheels. The inside of the lid shows patients being treated with the apparatus, which was used for toothache, neuralgia and painful tics. Only a little while after Michael Faraday discovered (1831) that magnets induce electrical currents in wires, electromagnetic machines were pressed into therapeutic service. This typical example emphasises treatment of nervous diseases, including neurasthenia, a type of nervous exhaustion common in the 19th century. (Photo by SSPL/Getty Images)