446 ELECTRO-PHYSIOLOGY CHAP. 



organ will be a little increased after each cut, but falls deeply 

 after a few minutes." Gotch obtained the strongest effect on 

 immersing the mixed bundles of prisms for a short time in hot 

 water, leading off two minutes later from ventral and dorsal 

 surfaces. The E.M.F. (in the direction of the discharge) then 

 rose to 0'0226 or even 0'0336 Raoult, but fell within a quarter 

 of an hour to its normal magnitude. That this was not a case of 

 hydrotherrnal action follows from the fact that even superficial 

 scalding of the dorsal and ventral halves of the prisms increased 

 the E.M.F. in the direction of the discharge. 



On the tail of the ray, Burdon-Sanderson and Gotch (13 c) 

 again occasionally determined a " current of rest " in the direction 

 of the discharge, on leading off from the anterior and posterior 

 ends. In organ-preparations this is usually much more developed, 

 especially after the momentary action of high temperatures 

 (immersion in hot water). Every natural or artificial stimulation 

 of the organ causes a more or less pronounced " after-effect " in 

 the direction of the discharge, and this only declines gradually. 



After these experiments there can be no doubt that we are 

 here in presence of a slowly-declining excitation of the prisms of 

 the electrical organ (due to mechanical or thermal stimulus), in 

 which the process in each plate may be compared to the gradually 

 disappearing negativity of a strip of muscle modified by veratria, 

 and excited by a brief stimulus. This seems to Biedermann an 

 even more cogent example than that which Gotch selected, of the 

 normal demarcation current in muscle, although both phenomena 

 are fundamentally due to the same cause, the preponderance of 

 the dissimilatory process over simultaneous assimilation. As the 

 persistent excitation in the muscle is expressed by negativity of 

 the affected parts, so in the electrical organ it is expressed by 

 weak electromotive activity in the same direction as that of the 

 strong electromotive action during its natural function. Du Bois- 

 Reymond calls this comparison of Gotch a logical error, but it 

 would not be difficult to invalidate the objections adduced against 

 it. In the present connection, however, this is unnecessary, since 

 we are really dealing only with the question of whether under 

 the above conditions any permanent excitation of the electrical 

 organ in the direction of the discharge can be affirmed or not, 

 and du Bois-Eeymond himself admits the former. For how other- 

 wise can the dictum be interpreted that the organ current is only 



