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. 1 



If the electrical condition of, say, zinc in the voltaic couple 

 (fig. 3, 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 



A -B 



FlG. 3. DIAGRAM SHOWING THE CORRESPONDENCE BETWEEN INJURED (B) AND 

 UNINJURED (A) CONTACTS IN NERVE, AND Cu AND ZN IN A VOLTAIC 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. 



