THE INJURY CURRENT OF NERVE 
271 
Such a conclusion is, however, difficult to follow ; since in the first place there 
is small ground for entertaining a belief in a relatively greater volume of the 
solutions of electrolytes placed there, and in the second place such a conclusion is in 
contradiction to the fact that in the model the conditions were obtained otherwise, 
namely, by the use of an internal solution of greater specific conductivity and not of 
greater volume. 
One is, therefore, justified in stating, that the only obtainable evidence is- in 
favour of the view that the solutions of electrolytes present within the axis cylinder 
are of greater specific conductivity than the solutions present elsewhere in the nerve 
trunk. 
Since such a greater conductivity can only be explained in one of two ways, 
namely, that the electrolytes in the internal solution are different in nature or greater 
in concentration than those found in the external solution ; such an inference may be 
used to point to one of these two conditions as of probable occurrence, and this is of 
great importance from the point of view of the ' injury current.' Immediately it is 
granted that the internal and external solutions are not the same, it becomes almost 
necessary to assume that the rupture of such a compound conductor would give 
rise to new processes of diffusion, and so to an ' injury current.' 
Even if we abandon this most probable view, that there is a pre-existing difference 
between the solutions, and for the time being suppose that the internal and the ex- 
ternal solution are one and the same in nature and in concentration ; still we cannot 
afford to neglect the importance of this tubular membrane, capable of maintaining a 
difference between the solutions, should any new cause for such a difference arise. 
Let any chemical change occur in the matter within the tubular diffusion obstacle, 
and lead to the formation of new electrolytes and to their appearance in the solutions 
therein contained ; at once is seen the possibility that they may be confined to this 
situation by the enclosing membrane. 
Let, for example, carbonic acid be produced from the destruction of some com- 
plex organic body in the axis cylinder, then it is conceivable that this substance might 
diffuse with greater ease along the track of the internal solution than through the 
membrane into the external solution. At once a difference is created between the 
two solutions, and, were the nerve ruptured, then at the injury the carbonic acid would 
have its first chance of freely escaping from the internal into the external solution. 
Granted the core model structure of the nerve fibre and the existence of this 
tubular surface of separation of the solutions contained in the nerve, we are at once 
presented with an important factor determining the origination of an 'injury current.' 
The first effect of injury is to disturb this barrier between the internal and 
external solutions, and whenever differences already exist between them, to give rise 
ipso facto to a 'current of injury.' 
