THE THEORY OF ELECTRIC ORGANS 261 



exciting current. It is, in, fact a new name for that phe- 

 nomenon which Du Bois-Reymond indicated as ' positive 

 polarisation-current.' Du Bois-Reymond had also shown 

 that this particular effect was most markedly exhibited when 

 the functional activity or ' livingness ' was at its highest. 

 Under opposite conditions, again, it would disappear. The 

 intensity of this homodromous after-effect was thus dependent 

 on the degree of vitality of the tissue under experiment. 

 Hermann and Hering, however, afterwards showed that what 

 Du Bois-Reymond called * positive polarisation ' was in reality 

 excitatory reaction. These excitatory effects are known to 

 be caused by either the anode or the kathode l ; and I have, 

 in the course of the last chapter, demonstrated the fact that 

 it is the differential excitability of a tissue which determines 

 such uni-directioned response. It is difficult, therefore, to see 

 the necessity of a new name for these phenomena. Dr. 

 Waller himself, however, offers the following as an important 

 reason : 



* The great mass of living things, whatever else they 

 may give and take from their surroundings, take oxygen 

 and give carbonic acid ; they may live slowly or they 

 may live quickly sluggishly smoulder or suddenly 

 blaze. A muscle at rest is smouldering : a muscle in its 

 contraction is blazing ; the consumption of carbohydrate 

 and the production of CO 2 , never absolutely in abeyance, 

 even in the most profound state of rest, are sharply 

 intensified when the living machine puts forth its full 

 power, and there is then a sudden burst of heat, and an 

 electrical discharge. . . .' 2 



This amounts to another way of saying that the cause of 

 the excitatory galvanometric effect is some explosive dis- 

 similatory change, a view which I have already shown in 



1 ' Within a given " physiological " range of strength of current the negative 

 kathodic must, equally with the positive anodic, be designated an "irritative" 

 after -current, due entirely to " polar current-action." ' Bledermann, Electro- 

 Physiology (English translation), vol. I. p. 448. 



" Waller, Signs of Life, p. 74. 



