Small medical Tesla coil used for electrotherapy around the turn of the century, manufactured by the Eugene Ducretet firm of Paris. The coil itself "(T)" is immersed in a tank of oil to prevent current leakage due to corona discharge. It is connected to a Leyden jar "(L, right)" to make a tuned circuit, and a spark gap "(e)", powered by a Ruhmkorff coil "(not shown)" One of the high voltage terminals "(E)" is attached through a wire to a pointed electrode on an insulated wand which produces a brush discharge which is applied to parts of the patients' body to treat various ailments. The other high voltage terminal is attached to a ground electrode which the patient holds.