The Origin of the Electric Organs in Astroscopus Guttatus. 145 



Cavendish in 1780 (29) was the first to conceive of the idea of current- 

 curves and to imitate the shock of Torpedo by ordinary electricity. He 

 was far in advance of his time and it was not until a century later that 

 Faraday (42) reached the same opinion. Although it has since been 

 possible by modern methods and apparatus to considerably modify 

 and correct the current-curves of Cavendish, the basic idea remains his. 



In 1831 Colladon of Geneva, experimenting on the Torpedo, gave the 

 name of "Colladon's currents" to those currents running between 

 points on either the ventral or the dorsal surface (31) . A few observa- 

 tions were made the same year by Matteuci (72), but not until the 

 discovery by Bilharz in 1857 (ie) was any further advance made in the 

 study of the electrical currents. DuBois-Reymond then calculated 

 that "the greater the length of a Torpedo column, provided the number 

 of plates in the unit of length is the same, so much greater must be its 

 electromotive force ; and by as much as the columns diminish in height 

 from the inner to the outer edge of the organ, by so much may the 

 electromotive force of the median columns be greater than that of the 

 outer ones" (is). At the same time he discussed the matter of immu- 

 nity in electric fishes, finding that all electric fishes are practically 

 immune to their own shock and relatively so to the shock of another 

 fish of the same species, much as a viper is immune to its own poison, in 

 spite of the fact that the body of the fish is much more favorably 

 placed to receive the shock than are the bodies of neighboring fishes. 

 Definite electric currents are known to pass through the body of the 

 fish. They have been detected in the digestive tract, in the brain and 

 spinal cord, and found to be of appreciable intensity, yet the fish 

 remains apparently unaware of the shock. 



Marey in 1879 (71) was the first to represent graphically the reflex 

 currents of Gymnotus and Torpedo by the use of the telephone. Schon- 

 lein (ss) repeated the experiments with a galvanometer and calculated 

 the voltage of the individual electroplaxes in Torpedo and in Raja; 

 Crerner (Gotch 50) used the "saitenelektrometer" of his own invention, 

 and in 1899 Garten (4s) made very accurate measurements and records 

 with the capillary electrometer. In 1881 Sachs (so) published his work 

 on the physiology of the organs of Gymnotus; while Gotch and Burch 

 (52, 53) and Koike (66) have independently published similar works on 

 Malopterurus, so that the shock in these three fishes has been ex- 

 haustively investigated. The general results have shown that electric 

 organs have much the same electrical properties as muscles and 

 nerves, with the difference that in the case of the electric organs the 

 elements are considerably modified and so arranged in series as to give 

 the effect of a battery in which an otherwise insignificant current can 

 be made measurable by addition (Gotch so). 



Gotch and Burdon-Sanderson (27, 28) followed up these experiments 

 on the weak electric fishes, finding them to be similar in both the 



