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 MALAPTKRURUS. 



(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 

 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 



