RODDIE, I. C. 
DR. FREEMAN: How do you account for the absence of this 
mechanism in the palm of the hand? 
DR. RODDIE: This is difficult. Fox and Hiltonbelieve that in the 
hand, release of vasoconstrictor tone permits such a large increase 
in flow that the effect of bradykinin cannot be picked up by present 
techniques. 
DR. FREEMAN: Have they also considered the possiblility that 
local metabolites of the same sort as are produced in other active 
tissues might be responsible for vasodilatation in the skin? CO is 
probably the best example produced in the brain. 
DR. RODDIE: That will not quite fit since increase in the blood 
flow which this substance or this mechanism produces is very much 
greater than is necessary for the demands of the metabolic needs of 
the tissues. When the body is heated, the oxygen saturation of the 
efferent venous blood from the skin rises to practically full satur- 
ation. 
DR. HANNON: These two areas are normally exposed, whereas 
the skin of the forearm is covered. Is there a possibility that you 
might get some different response in a native living in the tropics 
who had his forearm skin exposed? 
DR. RODDIE: I do not know of any evidence that would support 
this. We have looked at a very narrow group of people, Irish medical 
students, and ourselves, but have not really extended it beyond that. 
MR. EAGAN: I believe that Edholm, Fox, and McPherson, in 
their first experiments had concluded that there was no vasocon- 
strictor control to forearm skin. Now, was this because they just 
did not start with cooled subjects so that they were at the neutral 
zone in the beginning? 
DR. RODDIE: Yes, that is it. In Belfast, where we are used to 
rather colder conditions than in London, when we blocked the nerves, 
our subjects were usually sufficiently cold to show some release of 
vasoconstrictor tone. 
DR. FREEMAN: Perhaps to change the subject a little bit. Dr. 
Hannon's question brings up the general notion of how great a role 
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