Electrical Organs
 |
| 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.
