280 Electric Fishes. 
part of the belly. Heating and chemical effects have like- 
wise been obtained. According to the experiments of 
Matteucci :—1. All the dorsal parts of the electrical organ 
are positive to all the ventral parts. 2. Those points of the 
organ on the dorsal face which are about the nerve which 
penetrate this organ are fosztive relatively to other points 
of the same dorsal face. 3. Those points of the organ on 
the ventral face are negative relatively to other points of 
the same ventral face. 
The Gymnotus. —This electrical fish is a native of the 
warmer regions of America and Africa. There are several 
species of the Gymnotus, but only one is electrical. In 
general aspect it very much resembles an eel—the body is 
smooth, and without scales (a peculiarity of all electrical 
fishes). The electric organs consist of alternations of dif- 
ferent substances, and are most abundantly supplied by 
nerves ; their too frequent use is succeeded by debility and 
death. The electric organs may be removed without injury 
to the fish. 
These organs form more than one-third of the whole fish. 
The two electrical organs are separated at the upper part 
by the muscles of the back, at the lower part by the middle 
partition, and by the air bag at the middle part. 
The electrical organs consist of two parts—viz., flat par- 
titions or septa, and thin plates or membranes intersecting 
them transversely. The septa are thin parallel membranes 
stretching in the direction of the fish’s length, and as broad 
as the semi-diameter of the animal’s body. They vary in 
length, some of them being as long as the whole body. 
The very thin plates which intersect the septa have their 
breadth equal to the distance between any two septa. 
There is a regular series of these plates, from one end of 
any two septa to the other end, 240 of them occupying a 
single inch. 
The electric organ of the Gymnotus depends entirely on 
its will. It does not keep its organs always charged, and 
it can direct its action towards the point where it feels it- 
self most strongly irritated. When two persons hold hands, 
and one touches the fish with his free hand, the shock is 
commonly felt by both at once. Occasionally, however, in 
the most severe shocks, the person who comes into imme- 
diate contact with the fish alone receives it. 
A fine specimen of this remarkable fish was for some 
time, in possession of the proprietors of the late Gallery of 
Practical Science in Adelaide street, and was made the 
