
The Structure and Function of Nerve Fibres. 323 
The only fact gleaned from such an examination is that the salts present are 
very largely salts of potassium. Summing up all this indirectly-obtained 
evidence, it might therefore be said that there was reason to believe that a 
solution of potassium salts of more than usual concentration was present in 
the interior of individual nerve-fibres. 
Appreciating the fact that this statement might be critically examined in 
its bearing upon any one of the electrical phenomena elicited from the nerve, 
I made, a few years ago, a careful and detailed inquiry into the phenomenon 
known as the injury-current. Taking the supposed greater conductivity of 
the internal solution as 4 main guide to the choice of appropriate methods of 
experiment, I examined the possibility that the injury-current was due to the 
diffusion from this more concentrated solution first permitted by the circum- 
stances of injury. Electrodes placed upon the transverse-cut end and the 
longitudinal surface respectively were treated theoretically as if the first was 
in contact with the internal solution, the second in contact with the external 
solution, of a hypothetical single nerve-fibre represented by the nerve-trunk. 
Modifying the value of the external solution, I found that a very precise 
modification of the value of the electromotive force thus measured followed 
each variation in the external solution. The relation thus found between the 
value of the external solution and that of the electrical phenomenon I called 
the “ Concentration Law.’”? Its nature was such as to confirm the opinion 
that in this arrangement I was dealing with a liquid concentration cell, but if 
so it was evidently a special case in which the conditions present were 
curiously simple. Judging from the numerical statement of the law alone, 
this simplicity indicated a relation between the solutions present such that 
the internal solution must be supposed to be ten times more concentrated 
than the external solution. Such a difference of concentration as this seemed 
on other grounds improbable, and the necessity for such a conclusion entails 
a critical examination of the kind of concentration cell supposed to be thus 
formed and examined in the nerve. The hypothetical contents of this cell 
are (1) the internal solution, (2)a membrane of undetermined but presumably 
limited permeability, (3) the external solution. Knowing nothing as to the 
probable effect of the interposition of this membrane, it seemed best to seek 
for the case in which the value of the cell was reduced to zero. In this case 
it seemed fair to infer that the peculiarities of the membrane, supposing its 
permeability to be the same in both directions, were eliminated, and that the 
cell contents were now: (1) a solution, (2) a membrane, (3) another solution 
similar to the first. Having sought experimentally for such instances, and 
Norr.—*, etc. These numbers refer to the entries in the list of references printed at 
_ end of paper. - 
