3°4 
THOMPSON YATES LABORATORIES REPORT 
There is, however, another fact to consider, namely, that if at any time the tem- 
perature of the nerve could be suddenly changed from 38°C. to I7°C, the value of 
the injury current (as determined by a diffusion process) would be found to be quite 
different, without there being any intervening differential rate of decline to consider. 
In view of such consideration it will be seen that in the second part of the experi- 
ment the temperature of the nerve, which had been for twenty-five minutes at 38° C, 
was changed to i~°C. without producing any alteration in the low value due to more 
rapid decline through the preceding twenty-five minutes. The result of this secondary 
modification in this experiment is also of interest from another point of view. A 
differential modification of the temperature of the ' internal ' and ' external ' solutions 
of the nerve might be of importance. Taking the main characteristic of the physical 
structure or nerve to be the separation of its solutions by tubular membranes, such a 
characteristic might conceivably be a factor determining that the temperature of the 
' external solution ' should be more readily capable of modification than that of the 
4 internal solution.' Such a differential modification would alone account for great 
modification of the injury current, and is probably accountable for differences 
observed in the nerve injury current at very different temperatures of the air. It is 
satisfactory, therefore, to note that the modification produced in five minutes must 
have, in view of the result obtained, equally affected all the factors in the production 
of the injury current. For had the cooling affected only the external solution, the 
injury current would have been increased. Immersion in a solution at a temperature 
of 1 8° C. is therefore convenient, and also five minutes is an adequate time in which 
to bring the whole nerve approximately to this temperature. 
