THERMORECEPTOR PHYSIOLOGY 
DR. HANNON: If there are no further questions, we can go on 
with Dr. Hensel, I believe; he has something possibly related to 
this. 
DR. HENSEL: I appreciate very much this opportunity to dis- 
cuss some data on metabolism of the no n- anesthetized cat during 
hypothalamic cooling. 
Figure 1 shows a device for the cooling. In most cases, two 
cooling units were implanted symmetrically into the anterior 
hypothalamus. The thermodes have an outer diameter of one milli- 
meter. The right part or the left part of the anterior hypothalamus 
can be cooled separately, or both parts at the same time. The brain 
temperature at a certain distance apart from the thermode is 
measured by means of a thermistor. The cooling water comes in 
centrally and leaves the thermode through a lateral tube. 
I must say I disagree a little with Dr. Hemingway, because we 
found that the cats are quite cooperative andean be trained to quite 
a high degree (Fig. 2). 
A heatedthermocouple unit was used for recording the cutaneous 
blood flow in the ear. For measuring the metabolism, the cat is put 
into a double-walled perspex box which can be circulated with water 
and set at any desired temperature by means of a thermostat. The 
measurement of O consumption and CO output is made in an open 
system. The chamber is perfused with a stream of air of constant 
velocity and the air coming out of the chamber is continuously 
analyzed for CO and O . 
We studied quantitatively the heat production under various 
external temperatures, and at the same time, under the standardized 
hypothalamic cooling. We found the correlation shown in Figure 3. 
The lowest temperature in the chamber was about 5 C or 6 C, 
the highest 40 C. The lower the external temperature, the higher 
the metabolic increase during the same standardized hypothalamic 
cooling by about 2 C.I think this is another example of the cor- 
relation as shown by Dr. Lira between the external stimulus and 
the hypothalamic cooling in the unanesthetizedandunrestrainedcat. 
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