HISTORICAL SURVEY OF THE SUBJECT.
The power of certain fishes to give electric shocks has been known from the earliest times. A hieroglyphic representation of AraZvi:germ/us eledvieua, the electric cat-fish, has been preserved on the Egyptian tomb of Ti (Gotch 50, and the still more formidable shock of the elec tric ray of the Mediterranean was used by the Roman physicians as a charm to cure their patients, procuring for the fish the popular and familiar name of torpedo (Dixon as). The numbing power of Gymnotus has long been feared by the South Americans, and many accounts of the extraordinary behavior of this giant eel-like fish have been published from time to time in popular form (Gotch so). Rumor would extend this extraordinary power to the snail Daudabardia, and General Davis describes the "wheel-bug" of the West Indies, Reduvius serrahis, with electric organs in its legs (Dixon 36), but these reports have not yet been substantiated.
The seven groups of fishes which have this electric power represent a wide range in structure and environment. Torpedo and the Rajithe are marine elasmobranchs and are of very similar structure, being broad, flat, of slow motions, with a habit of lying on the bottom of the ocean. Torpedo is especially common in all warm seas, but the skate has been found much more widely dispersed in the salt water of the world. Malopterurus, Gymnotus, and the Mormyrithe are fresh-water teleosts. Malopterurus differs considerably from the other two groups in structure, being a silurid of considerable size. It inhabits the River
Nile. Gymnotus is a South American eel-like fish of great length, found abundantly in the South American rivers. It has the character istic eel-like method of locomotion. The Mormyridm are typical tele ost fishes of great variety of shape and difference of habit, abounding in the Nile and other fresh waters of Africa (Gotch so).
Although the numbing effects of these fishes have been known so long, the cause remained a mystery until in 1773 Dr. Walsh (92) dis covered the presence of "intense electrical currents" in Torpedo, "developed through the functional activity of special organs situated, on each side, in the lateral mass of the body of the fish." In 1835 a description of the electrical organs of both Gymnotus and Tor pedo appeared in the works of J. Hunter (63), while in 1844 Stark (s7) and in 1846 Robin (7s) described similar organs on either side of the spinal column in the tail of Raja, although no shock could be felt by the hand. From that time the literature on the subject has con stantly increased until now every branch has been covered. The majority of the investigations were carried on during the latter part of the nineteenth and early part of the twentieth century, but a few investigators have continued the study to the present day.