] 42 Papers from the Department of Marine Biology. 



HISTORICAL SURVEY OF THE SUBJECT. 

 GENERAL. 



The power of certain fishes to give electric shocks has been known 

 from the earUest times. A hieroglyphic representation of Malopterurus 

 electricus, the electric cat-fish, has been preserved on the Egyptian 

 tomb of Ti (Gotch 5o), 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 38) . 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 Daudahardia, and General Davis 

 describes the 'Vheel-bug" of the West Indies, Reduvius serratus, with 

 electric organs in its legs (Dixon 38), but these reports have not yet 

 been substantiated. 



The seven groups of fishes which have this electric power represent a 

 wide range in stmcture and environment. Torpedo and the Rajidse 

 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 Mormyridse 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-hke method of locomotion. The Mormyridse are typical tele- 

 ost fishes of great variety of shape and difference of habit, abounding in 

 the Nile and other fresh waters of i\irica (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 (87) 

 and in 1846 Robin (78) 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 earlj' part of the twentieth century, but a few 

 investigators have continued the study to the present day. 



