THE RE-ACTIONS OF ORGANIC MATTER ON FORCES. 51 



substituted for muscles. The special causes of these pheno- 

 mena have not yet been determined. Considering that the 

 electric contrasts are most marked where active secretions 

 are going on considering, too, that they are difficult to 

 detect where there are no appreciable movements of liquids 

 considering, also, that even when muscles are made to con- 

 tract after removal from the body, the contraction inevitably 

 causes movements of the liquids still contained in its tissues ; 

 it may be that they are due simply to the friction of hetero- 

 geneous substances, which is universally a cause of electric 

 disturbance. But whatever be the interpretation, the fact 

 remains the same: there is throughout the living organism, 

 an unceasing production of differences between the electric 

 states of different parts; and, consequently, an unceasing 

 restoration of electric equilibrium by the establishment of 

 currents among these parts. 



Besides these general, and not conspicuous, electrical phe- 

 nomena common to all organisms, vegetal as well as animal, 

 there are certain special and strongly marked ones. I refer, 

 of course, to those which have made the Torpedo and the 

 Gymnotus objects of so much interest. In these creatures 

 we have a genesis of electricity which is not incidental on 

 the performance of their different functions by the different 

 organs; but one which is itself a function, having an organ 

 appropriate to it. The character of this organ in both these 

 fishes, and its largely-developed connexions with the nervous 

 centres, have raised in some minds the suspicion that in it 

 there takes place a transformation of what we call nerve- 

 force into the force known as electricity. Perhaps, however, 

 the true interpretation may rather be that by nervous stimu- 

 lation there is set up in these animal-batteries that particular 

 transformation of molecular motion which it is their function 

 to produce. 



But whether general or special, and in whatever manner 

 produced, these evolutions of electricity are among the re- 

 actions of organic matter called forth by the actions to which 



