ANTERIOR HYPOTHALAMIC LESIONS 
DR. FREEMAN: We developed our own interpretation of this 
which we still think is compatible with a dual center data. The 
anterior hypothalamus consists of heat-sensitive and cold-sensitive 
neurons, and these have an inhibitory effect upon neurons in the pos- 
terior hypothalamus which in turn are responsible for activation of 
heat- conservation and heat-production mechanisms. Heating anteri- 
orly will, in effect, increase this inhibition and depress the mech- 
anisms, whereas cooling anteriorly will do the reverse, cause a 
release from inhibition. An inhibition of inhibition, if you will, allows 
these mechanisms to spring up. Now, if you make a lesion anteriorly, 
you remove this inhibition, you produce an an animal with tendency 
to excessive heat production. This animal has no difficulty in main- 
taining himself in the face of cold stress, whereas an animal with a 
lesion posteriorly will tend to lose the capacity for heat production. 
When the temperature now goes up, there is no automatic mechan- 
ism; when the temperature goes down, there is no preventative 
mechanism left. We think that these are compatible if you express 
the dual center in terms different from those originally proposed. 
DR. CLARK: They are not compatible with the rest of the 
evidence. 
DR. FREEMAN: In what way? 
DR. CLARK: You can produce a cat with a large electrolytic 
lesion just caudal to the optic chiasma. These are large lesions, 
say from L four to R four and from zero down to the base; those cats 
will show low temperatures; at a room temperature of 22 C the 
temperatures will be so low you cannot read them on a clinical ther- 
mometer, and I have had temperatures as low as 25 C. Those are 
electrolytic lesions; if you make a lesion with a knife mounted in the 
stereotaxic frame at the same location, you do not get these hypo- 
thermias. The only trouble is that a knife wound like that is very 
hard to see in histological sections. You cannot be sure. You 
know that you went down and hit bottom, but in the sections, you 
cannot show where the edges of the lesion are. In fact, you may 
hardly be able to see the lesion at all. 
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