532 Dynamic Theory. 



the shock is less as the hands touch poiijts nearer together. The skin 

 of the animal is no doubt a conductor, and the shock felt is the dis- 

 charge from so much of the organ as communicates its electricity to 

 the part of the skin between the points touched. The violence of the 

 effect is thought to be due to ^ the rapidity of the succession of the 

 shocks. It is said that a single discharge of a Torpedo takes about one- 

 fourth of a second, and it is composed of about 25 separate shocks. 

 In the Torpedo, the top of the electric hexagonal prism, before described, 

 that is, its dorsal end, is positive, while the ventral end is negative. In 

 the Gymnotus, the head end is positive, the current being from head to 

 tail. In Professor Faraday's experiments with the Gymnotus, " needles 

 were converted into magnets ; iodine was obtained by polar decomposi- 

 tion of iodide of potassium ; and availing himself of this test, Fara- 

 day showed that any given part of the organ is negative to other parts 

 before it, and positive to such as are behind it. Finally heat was 

 evolved and the electric spark obtained." ( Owen, 1-357.) 



There are so many points of analogy between the electric organs and 

 the muscles, as to lead to the inference of a common origin for both. 

 The electric organs in the Torpedo appear to be modified muscles, the 

 prism, with its pile of flattened cells, being very like a muscle filament 

 with its constituent flattened discs. If such flattened discs were fixed 

 by their edges so that they could not contract under the electric stim- 

 ulus, they would be constrained to discharge their electricity instead of 

 turning it into work. They would thus become true electric organs. 

 The electric cells of the other fishes seem to have undergone greater 

 modification if we suppose them derived from ancient muscles, never- 

 theless their position in the animal strongly points to such derivation, 

 and we can readily perceive that if their attachments did not mechan- 

 ically restrain their contractility, their electricity instead of being dis- 

 charged might be employed in the compression of the cells and the 

 contraction of the organ. 



It is observed that a strong discharge from the electrical organ is 

 sometimes accompanied by muscular contraction. The Torpedo has 

 one stout muscle, the business of which is to contract the electric or- 

 gan itself. It has also been observed to retract the eyeball when de- 

 livering a discharge. There appears to be an intimate relation between 

 the muscles and the electric organs. Obviously, the more the contrac- 

 tion of either of the organs, the less the electrical discharges. During 

 the quiescence of the animal, the development of electricity goes on 

 from the circulation of the blood and from the chemical reactions pro- 

 duced in it, and this electricity constantly accumulates in the electric 

 organs as in an accumulator. 



A large amount of electricity is generated in all animals, including 



