344 STRUCTURE AND ACTIONS OF ELECTRIC ORGANS. 
organs of the Gyrnnotus are essentially the same in structure, 
hut differ in shape in accordance with the conformation of the 
animal; they occupy one-third of its whole hulk, 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 Malapti.rurus. 
(fig. 179), there is not any electrical organ so definite as those 
just described; hut 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 Gyrnnotus. 
423. In all these instances, the electrical organs are sup¬ 
plied with nerves of very great size, larger than any others in 
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. Even 
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, xn.) ; 
and it may be safely affirmed that the Nervous force develops 
