8 RESPONSE IN THE LIVING AND NON-LIVING 
through the non-polarisable electrode is from left to right. 
The uninjured end is therefore comparable to the zinc in a 
voltaic cell (is zincoid), the injured being copper-like or 
cuproid.! 
If the electrical condition of, say, zinc in the voltaic couple 
(fig. 8, c) undergo any change (and I shall show later that 
this can be caused by molecular disturbance), then the exist- 
ing difference of potential between A and B will also undergo 
variation. If for example the electrical condition of A 
approach that of B, the potential difference will undergo a 

Fic. 3.—DIAGRAM SHOWING THE CORRESPONDENCE BETWEEN INJURED (B) AND 
UNINJURED (A) conTacts IN NERVE, AnD Cu anp Zn 1n A Vottaic ELEMENT 
Comparison of (c) and (d) will show that the injured end of B in (d) corresponds 
with the Cu in (c). 
diminution, and the current hitherto flowing in the circuit 
will, as a consequence, display a diminution, or negative 
variation. 
Action current—We have seen that a current of 
injury—sometimes known as ‘current of rest —flows 
in a nerve from the injured to the uninjured, and that 
the injured B is then less excitable than the uninjured 
A. If now the nerve be excited, there being a greater 
1 In some physiological text-books much wrong inference has been 
made, based on the supposition that the injured end is zinc-like. 
