THE THEORY OF ELECTRIC ORGANS 263 



had up to the present been exhaustively studied. It is, then, 

 somewhat hazardous to declare that because a particular 

 phenomenon has not yet been observed to occur in inorganic 

 matter, it is by that fact demonstrated to be hyper-physical 

 in its nature, and must be relegated to the different and 

 mystical category of the exclusively vital istic. The very 

 foundation of such a statement would be swept from under 

 it, the moment it was shown that the same phenomenon 

 followed, under the same circumstances, in conditions which 

 were admitted to be purely physical. 



I have shown, it will be remembered, in the previous 

 chapter, that the uni-directioned response to electrical 

 shocks in either direction was due to the differential 

 excitability of the structure. The response of any aniso- 

 tropic organ would .always be from the more to the less 

 excitable, the more excitable becoming relatively galvano- 

 metrically negative. There may here be various cases of 

 excitation, all giving results of the same type, say, a respon- 

 sive current from B to A. The first is that in which, on 

 excitation, both B and A become galvanometrically negative, 

 A being the less so of the two. In the second case, the excit- 

 ability of A being slight, or negligible, B alone becomes 

 negative. And in the third case, excitation induces 

 positivity of A and negativity of B. In all these cases the 

 relative negativity of B being greater, the responsive current 

 will flow from B to A. The resultant current is made up, 

 in the first case, by subtracting the galvanometric negativity 

 of A from that of B ; in the second case, it consists of the 

 galvanometric negativity of B, that of A being zero ; and in 

 the third case, it is produced by the addition of the effect 

 at A to that at B. Examples of the last of these will 

 be found in certain animal and vegetable skins, described 

 in Chapter XXII. 



These being the conditions, then, for the induction of 

 the uni-directioned responsive current, it appeared to me 

 probable that the same result could be obtained with 

 inorganic substances, provided that the specimen were so 



