ELECTRIC FISH 



ment of these electrical organs is similar to that of 

 ordinary muscles, and it is only during development 

 that they come to differ. The primitive fibres thicken 

 and change until they take the form of little prismatic 

 columns, instead of remaining similar to the fibres of 

 the striated muscles. 



This likeness of structure applies equally to their 

 action. The normal muscle acts when it is stimulated 

 by the nervous impulse from the centres, the brain 

 and the spinal cord. Before it receives that stimulation 

 it is inert, afterwards it contracts. This contraction is 

 not continuous but comes about in a series of successive, 

 rapid shocks which run one into the other. In the same 

 way the electric organ, innervated by large nerves from 

 the centres, receives from them the influx which sets it 

 in action. Then it produces electricity, emitting it at 

 short intervals, in successive discharges which produce 

 the shock. This electrical discharge is the strict equiv- 

 alent of muscular contraction. The organ produces 

 electricity as the muscle produces movement. 



If we go further into the study of this remarkable 

 likeness, we find out how it is brought about. The 

 electrogenic property of these organs, in spite of its 

 apparent precision and completeness, is not peculiar to 

 them. It is found elsewhere, notably in the true muscles 

 themselves, but it is less powerful and less apparent 

 because it is hidden beneath other and more important 

 functions. All living tissues, when they are in action, 

 produce electricity, not very much, but in an appreciable 

 degree. It is a consequence of the chemical changes 

 which take place in them. Contracting muscles are 

 more active in this respect. Not only does their action 

 appear in the production of mechanical energy, but also 

 in that of a relatively considerable quantity of electrical 

 energy. The specialized organs of torpedoes, electric 

 eels and the like, the organic batteries which these fishes 

 have in their bodies, only accentuate a condition which 

 is present to begin with. The mechanical power is 

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