THE ELECTRIC CONDUCTIVITY OF MAMMALIAN NERVE 65 
conductivity would be proportional to the conductivity of the solution used. The 
whole conductivity of the nerve would be equal to the sum of a constant quantity 
plus a quantity proportional to the conductivity of the solution used. Now if the 
values given above tor the conductivity after immersion (expressed as ratios to the 
conductivity before immersion) are plotted against the conductivities of the solutions, 
the result is as shown in the accompanying figure. The relation is a straight line, or 
very nearly so. Its equation would have the form y = ax + c. The ordinate 
(conductivity of the nerve after immersion) is equal to a constant c (80 per cent, ot 
the normal conductivity of nerve) plus a quantity which is directly proportional to x, 
the conductivity of the solution. The whole series of results is therefore in harmony 
with the view that 80 per cent, of the conductivity of nerve is provided by the 
internal solution. 
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My measurements afford another means of calculating the relative conductivity 
of the internal and external solutions of a nerve. Before immersion the external 
solution has a conductivity about equal to that of the 1 /8th gramme-molecular 
solution of KC1. After immersion the external solution has a conductivity equal to 
that of the KC1 solution used ; therefore, the conductivity of the external solution is 
changed in a known ratio. The original conductivity of the nerve is equal to the sum 
of the internal and external conductivities, while the conductivity after five minutes' 
immersion is equal to the same internal conductivity plus a known multiple of the 
original external conductivity. We have thus two equations for finding our two un- 
known conductivities — internal and external. Macdonald' has already solved such 
equations in a typical case. Part of the object of my work was to see whether the 
values so calculated would agree in different cases and with different strengths of 
solution. I found considerable variability among the individual nerves, but close 
agreement between the averages for different strengths of immersing solution. The 
K 
I. Op. at., p. 342 
