CONTROL OF PERIPHERAL CIRCULATION 
conditioning process plays in these vasomotor reactions. Have you 
ever had any experience along those lines? I realize your patients 
are oftentimes one-shot deals, so they do not have much time for 
learning. 
DR. RODDIE: Well, we find that the more we train the subjects, 
the more stable are their blood flows. We have difficulty with people 
who are brought to us for the first time. However, you can condition 
people. Certainly you can condition the vasodilation of the forearm 
muscle during stress quite easily. However, when an experiment is 
done which involves repeated infusion of a certain drug, you can often 
see this increase in flow as the clock comes around to the time when 
the infusion should start. Whether this is conditioning or apprehen- 
sion I am not sure. 
DR. FREEMAN: Maybe they are the same, basically? 
DR. RODDIE: Yes. 
DR. FREEMAN: What is your interpretation of blushing? 
DR. RODDIE: Blushing is not understood. I think it means that 
there is a vasodilator nerve supply to the face and ears. We have 
looked at this a little bit duringthe experiments in emotional stress. 
During blushing, the vessels in the skin of the face and the ear dilate 
whereas in the skin of the fingers they will constrict. But it is very 
hard to devise a stimulus which will produce a blush repetitively, 
and we find that when we are trying to devise these things that we 
blush more than the subject. 
DR. HANNON: One other point here, you stated correctly that 
the skin is concerned with cold exposure with control of heat loss. 
There is also, in prolonged cold exposure, the possibility that the 
muscles can affect, not heat loss, but heat production, and there is 
some evidence of an increase in circulation of muscle that is not 
tied to heat production. I believe that Canadian workers have worked 
on this. 
DR. RODDIE; Yes. 
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