LIM, T. P. K. 
temperature the variations in the brain temperature have a greater 
influence in the initiation of panting than shivering. 
The relative roles and interactions of central and peripheral 
mechanisms at the onset of panting and shivering, as revealed in 
our stucfy, are certainly established in the animals under anesthesia. 
However, it is not certain whether such relationships between cen- 
tral and peripAieral mechanisms also exist in the unanesthetized 
animal. The elucidation of control mechanisms of bocfy temperature 
in the unanesthetized animal is quite difficult since shivering or 
panting may be produced by a conditioned reflex, and also a regional 
or steady state dissociation of body temperature is almost impos- 
sible in the intact animal. In addition tothis, due to the current un- 
certainty, particularly advocated by Dr. Benzinger, a careful study 
concerning the control mechanisms of body temperature in the 
unanesthetized animal is needed. 
Althougji our data are generally in accord with the duality hy- 
potheses, that is, that both central and peripheral mechanisms are 
involved in the control of body temperature, the mode of interaction 
of the two cardinal mechanisms remains unknown. And in addition, 
despite the classical works by Dr. Ranson and his associates, 
which provided a valuable evidence for locating the central control 
mechanisms of body temperature in the hypothalamus, the necessity 
for additonal work concerning the neuroanatomy of the central 
thermoregulatory area is apparent. Emplpyingmodernneurophysio- 
logical tools, it may be possible to demonstrate more clearly the 
locations and functions of heat dissipation and conservation in the 
forebrain as well as the midbrain. 
In conclusion then, perijAieral and central mechanisms for the 
initiation of thermal panting and shivering have been studied in the 
anesthetized dog employing a thermal dissociation technique. Our 
first conclusion is that thermal panting can be produced by central 
but not by peripheral heating alone. The hypothalamic temperature 
threshold for panting is higher in central heating alone than in whole 
body heating. Thermal panting established by whole body heating 
disappears whenever either central or peripheral temperature alone 
is lowered. Thus, it is concluded that both central and peripheral 
temperatures contribute to the initiation of panting, although the 
central temperature is more important. 
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