CHATONNET, J. 
no muscular reaction when the central temperature is selectively 
decreased (Fig. 11). 
Keller (1959), in coagulation experiments on the dog hypothal- 
amus, reports cases of defect in the regulation of central temper- 
ature against cold, although potent reactions of shivering, no doubt 
of reflex origin, take place. On the other hand, the same author 
succeeded in observing shivering after elimination of the whole 
peripheral thermal sensitivity by cutting the brain stem except 
for the pyramidal bundles. In the last case the good resistance in 
cold exposure could be ascribed to brain sensitivity. 
The existence of a central cold-sensitive device in the brain 
seems well proved; nevertheless, its functional significance remains 
to be evaluated. 
One may also ask whether the thermogenetic response is spe- 
cific for each kind of activation (central or reflex). According to 
Davis and Mayer (1955), the chemical regulation, in its restricted 
meaning (without muscular activity), depends only on the central 
temperature. On the other hand, shivering and muscular activity 
would be under a pure reflex control. Some of the preceding results 
are in conflict with this view. As for the control of epinephrine, no 
recent direct evidence has been obtained. 
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