VIII 



.] FALLACY OF THE ELECTRODES 131 



of counter-currents at make exceeding the sum of counter- 

 currents at break. A closer scrutiny of the conditions of the 

 reaction shows that both factors are, or may be, effective, i.e., a 

 physiological reaction in the direction of break can occur by 

 reason of post-anodic action-current, and a physical reaction in 

 that same direction can be due to an algebraic sum of ordinary 

 polarisation currents.* 



It is not quite, easy to clearly demonstrate the physiological 

 factor even in a favourable case, and practically impossible to 

 do so in an unfavourable case ; I have therefore not made 

 systematic use of this first disposition of test 



The second disposition, by which only the after-effect of 

 tetanisation is observed on the galvanometer, is, in my experi- 

 ence, less liable to be misleading than the first. But the 

 case to which I systematically applied it, viz., the human skin, 

 has been a somewhat favourable one to follow out, since by 



SKIN Living- Decid 



Response 



break * > 



Response > > 



reason of its physiological disposition the skin gives sign of 

 life by an outgoing response to all directions of induction 

 currents. Tetanisation by such alternating currents provokes, 

 first, a summation of physiological (outgoing) effects ; second, 

 a resultant of alternated polarisation effects which is in the 



* Von Fleischl's deflection is discussed at some length in Animal 

 Electricity, pp. 115-119, 1897. The superior polarisation by make there 

 alluded to is shown in a paper to the Physiological Society (i2th Nov. 

 1898), on the "Influence of Polarisation on the Electrical Resistance of 

 Nerve." A deflection in the direction of break, during the* passage of alter- 

 nating induction shocks, might also be due to an irreciprocal resistance, 

 smaller to the break than to the make shock, as occurs in the passage of 

 alternating currents through a vacuum tube. I have not undertaken the 

 physical analysis of these possible factors, and have simply abstained from 

 using von Fleischl's deflection as a sign of life. 



