LIM, T. P. K. 
of Table I. Note that the average hypothalamic temperature was kept 
at the low value of 36.3 C, whereas the subcutaneous temperature 
of the thigh reached the high value of 45.1 C. The latter is 4.4 C 
above the level of this temperature at the time panting began in 
whole body heating. The mean rectal temperatures were identical 
in the two series. 
A second group of four dogs anesthetized with chloralose was 
subjected to the same procedure with essentially identical results. 
None of these four animals panted, the respiratory rate increasing 
from the mean control value of 18/min to only 47/min at the end 
of the heating period. The maximum temperatures reached at this 
time are summarized in line 3 of Table I. The mean hypothalamic 
temperature was somewhat higher, and the subcutaneous tempera- 
ture somewhat lower than in the barbital group, but the latter 
temperature was still 3.6 C above the threshold for panting in 
whole body heating. 
From this series we conclude that if hypothalamic temperature 
is kept between 36 C to 38 C, panting cannot be produced in the 
anesthetized dog by peripheral thermal stimuli alone within the 
temperature range studied. It is considered unlikely that these re- 
sults would have differed if the head skin had been included in the 
heating. The results thus imply that panting in whole body heating 
cannot depend upon peripheral stimuli alone. Such stimuli do, how- 
ever, produce some increase in respiratory rate, and this may be 
called "p re-panting hype rpnea." 
Series III - Central Heating 
In the next series, we wished to determine whether "central 
panting" could be produced or not. Therefore, the hypothalamic 
temperature was gradually raised by heating the carotid arterial 
blood over a period of 40 to 60 minutes. Of six animals so treated, 
four panted while the other two showed onlypre-panting hyperpnea. 
The hypothalamic, subcutaneous, and rectal temperatures at the 
onset of panting (or the maximum levels attained without pan- 
ting) are summarized in lines 4 and 5 of Table I. Note that 
