LECT. V.] 



ELECTRICAL ORGANS 



77 



exciting current ; positive polarisation is in the same direction 

 as the exciting current. 



These four stages are reducible to two, by omission of 

 Type II. (variety below Type I.) and of Type III. (variety 



Tlic response is absolutely The response is absolutely 

 and relatively positive. and relatively negative. 



! a t 



aS I 



O-4J 



- 



The response is absolutely positive and relatively 

 negative. 



FlG. 34. Du Bois-Reymond's diagram (_Archh\ 1885, p. 121) to illustrate the 

 electrical response to electrical excitation of a strip of the electrical organ of Torpedo. 

 The direction of the normal organ-discharge is supposed to be upwards, so that the 

 first two responses of the upper line are homodrome in relation to the exciting 

 current ; the next two responses and all four responses of the lower line are 

 antidrome. 



above Type IV.). We thus have Type I. as the characteristic 

 response of the living organ, and Type IV. as that of the dead 

 organ. This if you will carefully read du Bois' description, 

 and clearly appreciate the significance of his terminology- 

 is the essential pair of features that respectively characterise 

 the living and dead states of an electrical organ it discharges 

 in a direction of its own while it is alive ; after death, it exhibits 

 the ordinary polarisation of a non-living electrolyte. 



