THE IMPENETRABLE SEA 



torpedoes, catfish and electric eels are modified muscle- 

 tracts. The associated nerve-endings are. comparable to 

 the normal terminations of the motor nerves on muscles. 

 But this fact contributes nothing whatever to the solution 

 of the problem. Nor does the structure of the muscle- 

 tracts shed the slightest light on the question: How do 

 these electric fishes produce and control their electrical 

 currents? The organs consist of a very large number of 

 rounded columns or chambers, each enclosed in a thin 

 membrane. 



The entire structure is duplex. The columns are 

 separated by longitudinal and transverse partitions of 

 fibrous connective tissues. The nerves taper to extreme 

 thinness, branch considerably, and finally fuse with what 

 may be described as ''plates" or ''discs" of modified mus- 

 cular substance. Each of the columns or prismatic 

 chambers contains a jelly-like substance or fluid. 



A rough model of the structure might be made by 

 making a number of piles of coins, with attenuated 

 bladders between them — in fact a kind of "voltaic" 

 group of piles. The length of the columns, and conse- 

 quently the number of discs in the various piles, varies 

 according to their position in the creature's body. The 

 columns extend right through the creature's body, from 

 the skin of the back to that of the abdomen, and are 

 clearly visible on both sides, so that those in the middle 

 of the animal are necessarily the longest and those at 

 either end are much shorter piles of discs. 



In some large specimens of the electric fishes as many 

 as eleven hundred columns have been counted. A vast 

 amount of blood is circulated through its electric organ, 

 and the structure is permeated with complicated mazes 

 of nerves which run in every direction — far more com- 

 plex than any telephone switchboard's wires. How the 

 discs in the structure come to be charged with electricity 

 is still a mystery to which science has not yet provided 

 the complete answer. 



196 



