a 
- 344 sTRUCTURE AND ACTIONS OF ELECTRIC ORGANS. 
organs of the Gymnotus are essentially the same in structure, 
but differ in shape in accordance with the conformation of the - 
animal ; they occupy one-third of its whole bulk, and run 
nearly along its entire length, being arranged in two distinct 
pairs, one much larger than the other. In the Malapterurus 
Fig. 179.— ELectRIc MALAFPTERURUS. 
(fig. 179), there is not any electrical organ so definite as those — 
just described ; but the thick layer of dense areolar tissue 
which completely surrounds the body, appears to be sub- 
servient to this function ; being composed of tendinous fibres — 
interwoven together, and containing a gelatinous substance in ; 
its interstices, so as to bear a close analogy with the special 
organs of the Torpedo and Gymnotus. 
423. In all these instances, the electrical organs are sup- ; 
plied with nerves of very great size, larger than any others in © 4 
the same animals, and larger than any nerves in other animals © 
of like bulk. These nerves arise from the top of the spinal — 
cord, and seem analogous to the pneumogastric nerve ($ 458) ~ : 
of other animals. The influence of these nerves is essential to ~ 
the action of the electric organs. If all the trunks on one” 
side be cut, the power of the corresponding organ will be 
destroyed, but that of the other may remain uninjured. If 
the nerves be partially destroyed on either or both sides, the 
power is retained by the portions of the organs which are still 
connected with the brain by the trunks that remain. Eyen 
slices of the organ entirely separated from the body, except by 
a nervous fibre, may exhibit electrical properties. Discharges 
may be produced by irritating the part of the nervous centres 
from which the trunks proceed (so long, at least, as they are 
entire), or by irritating the trunks themselves, In all these 
respects, there is a strong analogy between the action of the 
nerves on the electric organs and on the muscles (Chap. X11.) ; 
ind it may be safely affirmed that the Nervous force dev elops 
