Electrical Organs

The Torpedo, with its electrical apparatus displayed. - b, branchia; c. brain; electric organ ; g, cranium; me, spinal cord; n, nerves to the pectoral fins; nl, nerollaterales; np, branches of the pneumogastric nerves going to the electric organ; o, eye
Fig. 18. - The Torpedo, with its electrical apparatus displayed. - b, branchia; c. brain; electric organ ; g, cranium; me, spinal cord; n, nerves to the pectoral fins; nl, nerollaterales; np, branches of the pneumogastric nerves going to the electric organ; o, eye.
Certain fishes belonging to the genera Torpedo (among the Elasmobranchii), Gymnotus, Malapterurus, and Mormyrus (among the Teleostei), posses organs which convert nervous energy into electricity, just aa muscles convert the same energy into ordinary motion, and therefore may well be mentioned in connection with the nervous system. The "electrical organ" is always composed of nearly parallel lamellaj of connective tissue, enclosing small chambers, in which lie what are termed the electrical plates. These are cellular structures, in one face of which the final ramifications of the nerves, which are supplied to the organ by one or many trunks, are distributed. The face on which the nerves ramify is in all the plates the same, being inferior in Torpedo, where the lamelte are disposed parallel to the upper and under surfaces of the body; posterior in Gymnotus, and anterior in Malapterurus, tlie lamallae being disposed perpendicularly to the axis in these two fishes. And this surface, when the discharge takes place, is always negative to the other.

In Torpedo the nerves of the electrical organs proceed from the fifth pair, and from the "electric lobo" of the medulla oblongata, which appears to be developed at the origin of the pneumogastrics. In the other electrical fishes the organs are supplied by spinal nerves; and, in Malapterurus, the nerve consists of a single gigantic primitive fibre, which subdivides in the electrical organ.

The ordinary Rays possess organs of much the same structure as the electrical apparatus, at the sides of the tail.