THE PHYSIOLOGY OF ELECTRICAL ORGANS. 



By Fkancis Gotch. 



Contents : — General Description, p. 561 — Minute Structure in R. batis, Gymnotus, 

 Torpedo, and Malapterurus, p. 563 — Functional Activity, p. 568 — The Electrical 

 Changes of Nerve-Organ Preparations ; Activity Effects, p. 571 — The so-called 

 Current of Rest, p. 571 — The Organ Response, p. 572 — Its Time Relations, 

 p. 575 — Self-Excitation of the Electrical Organs, p. 579 — Effect of Repeated 

 Stimuli, p. 582 — Residual Effect of the Response, p. 583 — Electromotive Force 

 of the Response, p. 583 — Polarisation Phenomena, Secondary Electromotive 

 Effects, Irreciprocal Conductivity, p. 584 — The Reflex Response of the Organs, 

 p. 588— The Nature of the Activity, p. 590. 



The possession by certain fishes of a peculiar power, which is now known 

 to be that of giving electric shocks, is such a remarkable phenomenon, 

 that it attracted the special attention of early naturalists, and is referred 

 to in ancient literature. The earliest record is probably the hieroglyphic 

 representation of the Malapterurus electricus in the Egyptian tomb of 

 Ti ; this fish, belonging to the Siluridm, is still found in the Nile, and 

 in the West African rivers. The numbing force exerted by the electric 

 ray of the Mediterranean caused this still more formidable fish to be 

 termed vapKr; by the Greeks, and torpedo by the Romans. The powers 

 of the electric eel, or Gymnotus, found in the branches of the Eiver 

 Orinoco, have always been feared by the inhabitants of this portion of 

 South America ; it is in many respects the most remarkable of all 

 electrical fish, since it attains a large size, 8 to 10 ft. in length, and its 

 electric power is thus very great. The shock of all these fish may 

 be sufficient to kill small animals and stun large ones, but although 

 the numbing effects on man were well known, their causation remained 

 a mystery until Dr. Walsh, in 1773, discovered that the power of the 

 Torpedo was due to the development of intense electrical currents, 

 through the functional activity of special organs situated one on each 

 side in the lateral mass of the body of the fish. 1 The general structure 

 of the organs in Torpedo was described by Lorenzini in 1678, and a 

 detailed account was given by John Hunter, who also described 

 the organ of Gymnotus} Organs of small size have been found in 

 certain species of skate and in the Mormyrus, the latter a fresh-water 

 fish found in the rivers of North Africa (Nile, etc.). These organs were 

 termed " pseudo-electric," because, though resembling in general struc- 

 ture those of Torpedo and Gymnotus, the electric shocks produced by 

 their activity were insufficient to attract notice by their effects upon 



1 Walsh, Phil. Tram., London, 1773, pp. 461-477. 



2 Lorenzini, " Osservazioni intorno alle Torpedini," Firenze, 1678 ; J. Hunter, "Works," 

 London, 1835, vol. iv. 



VOL. II. — 36 



