454 ELECTRO-PHYSIOLOGY CHAP. 



cross-section of the plate, so that the organs thus form prisms 

 with a much larger number of constituents than follows from the 

 number of the plates." 



If in the discharge of the organ we assume a sudden transi- 

 tion of the dipolar molecules from the "peripolar" to the 

 "pile-like" arrangement, the process that takes place obviously 

 coincides with that which du Bois-Keymond postulated in order 

 to explain the (galvanic) electrotonus of medullated nerve. 



But if the molecular hypothesis has already been proved 

 inadequate for nerve and muscle (to say nothing of gland- 

 currents and plant-currents), save on the boldest hypotheses to 

 account for the phenomena, we have the more reason to reject 

 it for the electrical organs, since all known reactions of these 

 structures can be explained from the "Alteration Theory" 

 without difficulty, starting only from the fundamental notion 

 that chemical differences are initiated in each plate in consequence 

 of excitation from the nerve, which produces a P.D. between the 

 interfaces in the given direction. 



Hence we must fall back upon the view, supported as 

 du Bois-Keymond himself admits (4 g, p. 46) by the strongest 

 reasons, that the absolutely and relatively positive polarisation of the 

 electrical organ by the homodromous current is nothing more than 

 the after-effect of the discharge produced by the latter. 



It therefore becomes very difficult not to regard the homo- 

 dromous positive after-current as the remainder of a previous 

 excitation, even from the standpoint of the molecular hypothesis. 

 Since this explains the discharge " from a pile-like arrangement 

 of the electromotive molecules," it is necessary to ask (as du Bois- 

 Keymond himself pointed out) " in what particulars this arrange- 

 ment and that produced directly by the homodromous current 

 differ ? why the latter does not always complete itself in a 

 discharge ? " Du Bois-Keymond imagines that " there may be 

 two states which, although both associated with a pile-like arrange- 

 ment of the molecules, and identical in their external action, are 

 yet distinct within the electrical plate " (since one corresponds with 

 discharge, the other with absolute positive, homodromous polar- 

 isation). Yet this seems to present far more difficulties than 

 the conception that, just as there are at the seat of direct 

 excitation, at the close of a muscle-twitch, prolonged galvanic 

 alterations (negativity), recognisable as the after-effect, or more 



