REVERSED POLAR EFEECTS IN LIVING TISSUES 213 



The luminescence at make now took place at the anode, 

 and at break at the kathode. On reversing the current, the 

 new anode, formerly kathode, gave responsive illumination, 

 and at break the new kathode responded. In these results, 

 therefore, it will be seen that we have an instance of reversal 

 of polar effects, under excessively high E.M.F. 



These reversed effects are usually observed with a high 

 E.M.F. ; but sometimes, as has been said, owing to a modified 

 condition of the tissue, they may be obtained, under the 

 action of even a moderate E.M.F. I shall now give a very 

 interesting example in which we can trace the process of 

 reversal owing to the modification induced by fatigue, in a 

 manner somewhat similar to the last experiment described in 

 the case of Mimosa (p. 209). 



I took a fresh specimen of the detached organ, and carried 

 out four successive experiments on it, observing the effects 

 at both make and break, the E.M.F. used being twenty volts. 

 In order to present these results at a glance, I shall again put 

 them in a somewhat tabular form. 



(i) At make — Luminous response at kathode, which 

 irradiates slightly towards anode. 



At break — Little effect at anode, but natural luminosity 

 of the kathode falls below par. This shows the depressing 

 action of kathode-break. 



(2) At make — Luminous response at both anode and 

 kathode. 



At break — Luminous response at kathode only. These 

 effects, especially that of break-excitation at kathode, show 

 that the condition of reversal has set in. This will become 

 still more pronounced in the succeeding experiments. 



(3) At make — Luminous response appears at anode and 

 irradiates slowly towards kathode. 



(It will be seen that we have here a complete reversal of 

 the effects observed in (i) at make.) 



At break — No immediate effect is at first observed ; 

 later, a flash passes from anode to kathode. 



(4) At make — Luminous response at anode. 



