STUART, D. G. 
low bocfy temperatures in a 25 C environmental temperature but 
could not shiver. When exposed to a 45 C environmental tempera- 
ture, the animals' rectal temperature rose to 41 C to 43 C, this 
rise being accompanied by assumption of a languid posture that 
would permit maximal conductive heat loss. However, panting was 
not evident. Thus at four days after surgery, these animals verged 
on poikilothermy rather than homeothermy. Forty-nine days after 
surgery the two animals that survived the initial tests had normal 
rectal temperatures in the 25 C environmental temperature, could 
shiver in response to cold stresses and pant in response to heat 
stresses. Two other animals, H and H , with massive hypothal- 
amic lesions, demonstrated similar results when tested five days 
after surgery. Both these animals expired during the heat stress 
tests, without assuming languid postures and without panting. 
These results are listed to illustrate the author's reluctance 
to expose animals with massive hypothalamic lesions to heating 
and cooling tests in the early postoperative period of recovery. In 
this somewhat enfeebled condition death often results and the somatic 
responses to both high and low body temperatures are usually im- 
paired above and beyond the impairment present after the animals 
have recovered relatively fully from the surgery. 
Comments. The results support the electrical stimulation data 
in implicating the dorsomedial posterior hypothalamus in the pro- 
duction of shivering. If it is also accepted that cutaneous vasocon- 
striction is activated by the dorsolateral posterior hypothalamic 
neurons, then some of the seemingly diverse results of other in- 
vestigators can be explained in rather simple terms. For example, 
Figure 12 shows typical lesions produced by three sets of inves- 
tigators whose results have been widely quoted. First, Isenschm id's 
work with Krehl (1912) and Schnitzler (1914) implicated the lateral 
hypothalamus in temperature regulation (Figure 12 - Isenschm id 
D) but not the medial hypothalamus (Figure 12 - Isenschm id C). 
However, in this work, the animals' rectal temperatures were taken 
over a range of environmental temperatures, and at very low en- 
vironmental temperatures the body temperature of the animal with 
lesion C began to fall. If it is assumed that all these animals were 
in a debilitated condition and that, at least in terms of functional 
and nonfunctional nervous tissue, "C" could not shiver but could 
vasoconstrict, then it is feasible that its body temperature would 
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