Portable electrical device for medical use. It was thought to be useful in treating neurological diseases and local paralysis. The two electrical sources of circular shape in the upper part of the apparatus used mercury sulfate, (powdered in a special glass container) which was added before the use of the device. The sources are connected in series. A switch was interrupting the current in the first coil so that a voltage was induced in the second. The latter was connected with two handles (missing) with a brass ending, held by the patient who accepted a weak electroshock. The handles were doused with a sponge dipped in salt water for better conductivity. The bronze cap of the coils regulated the voltage of the secondary coil that was exerted to the patient. The greater the length of the coils covered by the bronze cap, the lower was the voltage.

(http://instrumenten.teylersmuseum.nl/index.php?option=com_vr&Itemid=3&ta...)