124 RESPONSE IN THE LIVING AND NON-LIVING 
there could be no possibility of the evolution of CO,, 
they tended again to become normal. 
If after mounting a wire in a cell filled with water, 
it be set aside for too long a time, I have sometimes 
noticed that it undergoes a certain modification, owing 
to which its response ceases to be normal and becomes 
reversed in sign. I have obtained this effect with 
various metals, for instance lead and tin, and even with 
the chemically inactive substance 

platinum. . 
ta) i { ] ' 'o! ' : : 
& Pa) | a Pe | a oe 
phhren POM P22 
et) > i Be 
i w 
-~ os Ma " 
t 
= before . after 

Fic, 75.—ABNoRMAL PosirIvE (tp) Respons—E IN NERVE CONVERTED INTO 
Normal (powN) Response AFTER Continuous Stimunation T (WALLER) 
The galvanometer is not dead-beat, and shows after-oscillation. 
The subject will be made clearer if we first follow 
in detail the phenomenon exhibited by modified nerve, 
eiving this abnormal response. The normal responses 
in nerve are usually represented by ‘down’ and the 
reversed abnormal responses by ‘up’ curves. In the 
modified nerve, then, the abnormal responses are ‘up ’ 
instead of the normal ‘down.’ The record of such 
abnormal response in the modified nerve is shown in 
fio. 75. It will be noticed that in this, the successive 
