THE CONDUCTIVITY OF THE INTERNAL SOLUTION 
If, as has been assumed in the previous section, the immersion of a nerve in 
solutions approximately isotonic with ' normal saline,' and in solutions slightly more 
concentrated than this, does not affect to any appreciable extent the pre-existing 
concentration of the internal solutions; it should be possible by measurements of 
the conductivity before and after the immersion to calculate the amount of this 
which is due to the 'internal solution.' 
The data from the following two experiments may serve this purpose in a pre- 
liminary fashion, sufficing until they can, as is intended, be repeated with solutions of 
other concentrations. 
The first experiment given below, A, serves to shew that a nerve which has been 
immersed in a -745 grammes per cent, solution of potassium chloride is practically 
unaltered, as far as its conductivity is concerned, by the immersion ; just as in the 
last section it was shewn that it is unaltered as far as the difference of potential 
between its longitudinal surface and cross section is concerned. 
The experiment is produced mainly so that it may be seen that the basis of the 
calculation made upon data of the subsequent experiment, B, is not very, far from 
accuracy. This basis being the assumption that the conductivity of the external 
solution pre-existent upon the nerve is practically that of a "745 grammes per cent, 
solution of potassium chloride. 
Experiment A 
Sciatic Nerve of cat immediately removed from the animal after death. 
The following measurements were made before and after immersion of the nerve in "745 per cent. 
KC1 (iV normal solution), for five minutes, at i8°C. : — 
Before 
After 
Weight 
•200 grammes * 
Weight 
•201 grammes* 
Length 
_)_■ 7 centimetres 
Length 
4"6 centimetres 
Resistance 
20,500 ohms 
Resistance 
20,100 ohms 
* The treatment to which these nerves were subjected was exact]}' the same as that dealt out 
to the nerves used in the experiments of the preceding section : the time of immersion, the tem- 
perature of the solution, the method of subsequent drying of the nerve in filter paper, etc. 
The attempt was always made in the subsequent drying of the nerve to regain after immersion 
the original condition of the nerve, as far as the presence of surface moisture is concerned. To 
