ELECTRIC TISSUE OF FISHES. 223 



the whole organ — is to be regarded as the basis of the 

 organ. A nerve-fibre passes to each electric plate ; 

 and nnder the influence of irritation, whether this is 

 due to the will of the animal or to artificial irritation 

 of the nerve, one side of this plate always becomes 

 more positive, the other more negative. As this occurs 

 in the same way in all the plates, the electric tensions 

 combine, as in a voltaic battery, and this explains the 

 very powerful action of such organs as compared with 

 that exercised by muscles, glands and nerves. 



There is, indeed, a great diflference between the 

 last-mentioned tissues and the electric tissues of elec- 

 tric fish. Muscles, nerves and glands when quiescent 

 generate electric forces, which undergo a change during 

 activity. Electric tissue, on the other hand, is en- 

 tirely inoperative when quiescent, and becomes elec- 

 trically active only when it is in an active condition. 

 Though unable to explain this difference, we must re- 

 mark that it affords no ground for tl e inference that 

 the actions of these tissues are fundamentally dif- 

 ferent. Whether a tissue exercises externally apparent 

 electric action, depends on the arrangement of its ac- 

 tive elements. But the changes which occur during 

 their activity in muscles, glands and nerves, and also 

 in electric tissue, are evidently so similar that they 

 must be regarded as related. An attempt will be made 

 in the next chapter to obtain a common explanation of 

 all these phenomena. 



7. It has already been stated that electric phenomena 

 have been observed in plants also, though we found no 

 sufficient reason to attribute any great physiological 

 importance to these. It therefore created much sur- 

 prise when the physiologist Burdon-Sanderson a few 



