THERMORECEPTOR PHYSIOLOGY 
DR. HANNON: Would you care to speculate how much of this is 
an Arrhenius effect, the temperature just slowing up the reaction? 
DR. HENSEL: This is very difficult to say because the whole 
curve does not look like an Arrhenius diagram. I think this curve 
might perhaps be due to the difference between two processes, each 
of which follows the Arrhenius law. 
DR. HANNON: Many rate reactions will show this phenomenon 
if the temperature range is wide enough. They usually describe 
these by two mathematical rate-processes. 
DR. HENSEL: This is just a formal description. We do not 
know anything about the processes involved in the thermoreceptors. 
It would be very interesting to know more about the mechanisms 
for transforming the temperature into the impulse discharge of the 
receptor. 
COL. QUASHNOCK: Is it possible to take the proximal portion 
of the nerve and stimulate it at the various frequencies to determine 
the threshold for sensation? 
DR. HENSEL: We have not tried this, but it could be done very 
easily. We use electrical stimulation of the nerve before cutting it. 
The subject reports the site of the sensation. 
DR. HEMINGWAY: You stated that slow cooling is not nearly 
as effective as fast cooling, and this brings up the point raised by 
Capt. Minard. During World War II we had some subjects who were 
cooled slowly, at the same time being very heavily clothed; I think 
they had clothing that built up to fourclos. In these subjects we ob- 
served that rectal temperature would drop two or three degrees 
without the appearance of shivering. 
DR. HENSEL: Yes, the same as observed in the measurement 
of CO . The rectal temperature will drop without any considerable 
sensation of cold. It might be a matter of the slow rate of cooling. 
The rate of cooling is much more important than the absolute 
temperature. 
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