1905. | The Structure and Function of Nerve Fibres. 343 
this complicated addition of states, and to them there has still to be added the 
chemical consequences attending upon true polarisation. Where there are so 
many factors to play with, there can be no difficulty in explaining any modifica- 
tion in excitability which may arise. It is doubtful if there is any advantage 
gained by doing so. For the present, it may only be pointed out that there is 
ample reason to expect a marked difference between the earlier and later stages 
of these alterations in function. 
Having considered in this preliminary way some of the classical phenomena 
produced by the passage of a current through nerve, it is possible to return 
to the more interesting subject of function. We see that the nerve owes its 
function to the possession of this core of colloid material, and to the property 
of “ pseudo-polarisation,” which is an attribute of the colloid material. There 
is still, however, another point to expand. Stress has been laid above on the 
apparently necessary condition, that the more rapidly moving ion of the 
electrolyte of the nerve should carry an electrical charge of the same sign as 
that which leads to the desolution (tends to lead to the coagulation) of the 
proteid colloids of the nerve. Introduction of the negative ion being the 
condition leading to desolution of the colloid and liberation of the electrolyte, 
then, if the process is to be transmitted, the motion of the liberated electrolyte 
must result in the bestowal of a similar charge upon the neighbouring portion 
of the colloid solution, and therefore the negative anion must have the 
oreater relative velocity. 
Let us consider what would happen if this were not the case. Let us deal 
with an assumed case, in which the bestowal of a negative charge being the 
condition essential t6 desolution, the positive kation has the greater relative 
velocity, Let ABCDE represent such a strip of colloid material. To begin 
with, the strip is homogeneous, and the distribution of potential, and of 
osmotic pressure along it, is uniform. Now, from any exciting cause 
whatever, let us suppose that the solution in A undergoes a change 
that in it desolution takes place, and electrolytes are set free. Diffusion 
tends to take place, therefore—the positive ion having the greater velocity— 
B becomes positively charged, and A is left negatively charged. The 
condition originally excited in A is hereby exaggerated, and more electrolytes 
are liberated, provided there is still a further stock to call upon. 
This fact would seem to indicate that there will be no further progression 
of such a process along the strip ABCDH, seeing that it certainly determines 
a more prolonged maintenance of the phenomenon in each spot affected. 
This, however, is not necessarily the case. B has become positively charged, 
its colloid particles have therefore gone into a state of more minute sub- 
division, and some of its inorganic salts have been consequently removed 
