ELECTRICAL FISHES 359 



leather model of the tish, saturated with sea-water, he covered the 

 organs corresponding to the poles with tinfoil, connecting them 

 by insulated wires to a Leyden battery. In this way he made a 

 true picture of the distribution of potential (lines of current) out- 

 side the fish in the surrounding water, and then showed how a 

 hand dipping into the water must feel the electric shock without 

 actually coming into contact with the fish, the intensity being 

 greater in proportion as the hand is nearer the fish. This agrees 

 with the observations of van der Lotts (4 e, p. 128) in 1762, to 

 the effect that a shock can be given through the air, which the 

 electric eel projects through its air-holes ; as well as the later 

 observations of C. Sachs that the jet of water from the bung-hole 

 of a vessel containing a gymnotus may conduct the shock. 



The discovery of galvanic electricity, and subsequent dispute 

 between Galvani and Volta, could not fail to be of great import- 

 ance to the theory of electrical activity in these fishes, as the 

 most pronounced manifestation of animal electricity ; while here, 

 as so often elsewhere in physiology, the mechanism of the electrical 

 organs was referred directly to the dominant physical theories. 

 Volta himself detected the analogy between the pile which he 

 discovered, and the organ of the torpedo, which is built up of 

 prismatic columns (Collezione dell' Opere, etc., Florence, 1816, t. ii. 

 pt. ii. p. 99) ; and even defined the pile as an artificial electrical 

 organ. Such a theory, according to which electricity is developed 

 from the contact of three dissimilar elements, had to encounter 

 great difficulties, foremost among which is the constant action 

 of the pile ; while the activity of the electrical organ is obviously 

 under the control of the animal. These objections were got 

 over by conceiving the fish to execute certain movements in the 

 act of discharging, by which the supposed electromotive elements 

 of its batteries, the nature of which was quite unknown, were 

 first brought into contact (Volta) ; or by conjecturing the 

 outfiow of a defective constituent at the will of the animal (A. 

 von Humboldt). One great difficulty was the impossibility of 

 insulating the organ, which led Valentin (34) at the beginning 

 of the forties to ascribe to the tendinous septa that surround 

 the columns (prisms) of the organs the function of insulators. 

 Schonlein, at the same time, held that the gymnotus could 

 voluntarily insulate itself from the surrounding water. 



The uncertainty (notwithstanding the apparent proof of the 



