ANTERIOR HYPOTHALAMIC LESIONS 
it in unanesthetized preparations, probably because there I cut down 
the power output of my diathermy apparatus. But we have a lot to 
learn. As far as the localization of these centers is concerned, I 
think we know quite a bit about heat conservation because Keller 
has had several animals that could regulate quite adequately in the 
heat, but could not in the cold. 
DR. HEMINGWAY: Does that include shivering, heat conserva- 
tion, and heat production? 
DR. CLARK: Yes. These animals when put in the cold would 
show a drop in body temperature similar to that you might see in a 
chronic midbrain preparation. 
DR. HEMINGWAY: Does that include shivering and cutaneous 
vasoconstriction, both in that one term? 
DR. CLARK: Yes. Of course, even these will show some vaso- 
motor changes. You get those even in the chronic midbrain dog. 
DR. LIM: From your recent data, do you suggest that chronic 
preparation should be made at least six months after operation? 
DR. CLARK: Well, there I do not know, but I do know that you 
have to differentiate between acute and chronic effect of lesions, and 
I think that any report that is based on animals a week, two weeks, 
one month, or two months after the operation should be questioned. 
DR. STUART: If the function does not return? 
DR. CLARK: Yes. Now, of course, determining the things that 
an animal can do a week after the operation as well as a normal 
dog is important, but one may be misled concerning the loss of 
function, for a week or up to two months or maybfe three months. Of 
course, the questions are: Is it due to tissue that regains function? 
Is it due to some other center vicariously functioning? You have a 
lot of problems in there, but the important thing after any brain 
operation is what the animal can do that approaches normal, not 
what is lost. 
DR. HEMINGWAY: That raises a question which Dr. Freeman 
and I have talked about many times. He thinks that if there is des- 
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