ANTERIOR HYPOTHALAMIC LESIONS 
DR. FREEMAN: We lowered the thermode routinely by short 
steps and stimulated each stage until we got a response. If you push 
it all the way to bottom, there is maximal damage to the structure 
that one is generally trying to stimulate. We went by easy stages. 
DR. CLARK: But, you did not get anything until you got deeper? 
DR. FREEMAN: Well, the points represent the position of the 
thermode at the time of an effective response. 
DR. CLARK: Presumably the thermode was in the area that 
is sensitive to heating. You did not get anything because that area 
should be up around the aqueduct. 
DR. FREEMAN: That is true; however, your pathway swings 
somewhat laterally there, is that correct? 
DR. CLARK: Well, there are no data on that. As far as the 
pathway for panting, yes, because if you leave just lateral ex- 
tremities of the midbrain, you still get panting, and those dogs 
cannot regulate against cold. 
DR. FREEMAN: This is Keller's work you are describing? 
DR. CLARK: Yes. 
DR. FREEMAN: That, I think, is also quite compatible with the 
finding of this region of sensitivity, that is, the anterior midbrain. 
DR. CLARK: No, Ithinkit is just a question of whether the path- 
way extends that far laterally. In other words, I think it is rather a 
diffused pathway that extends through the entire mesencephalon. 
DR. STUART: I think in fairness to Ranson and Magoun, it should 
be stated that they thought that the posterolateral hypothalamus in- 
tegrated heat conservation rather than heat productive mechanisms. 
In a 1940 review (Ergebn. Physiol. 41:56, 1939) they mentioned the 
difficulty encountered in instigating shivering pre-operatively with 
the applied cooling load. Thus they did not wish to attribute the inte- 
gration of shivering to that particular region of the hj^jothalamus. 
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