ANTERIOR HYPOTHALAMIC LESIONS 
with damage to the posterior hypothalamus or in animals with ex- 
tremely large lesions anywhere in the hypothalamus, hypothermias 
are routine and many of these last a week or more. This finding 
with posterior hypothalamic lesions fits the dual center theory fairly 
well but with more anterior lesions the fit is not so good. These 
hypothermias following large anterior lesions have also been repor- 
ted by McCrum {X953); however, Keller (1960) has stated that this 
is not the usual occurence in his series. The difference may lie in 
the type of lesion for Keller's have routinely been produced by 
suction or thermocoagulation while ours and those of McCrum (1953) 
were electrolytic. On the other hand, such hypothermias usually do 
not result from large purely unilateral electrolytic lesions. One 
might assume that the reversible hypothermias and hyperthemias 
might be due to some type of reversible damage to remnants of the 
dual centers, or, on the other hand, that these normal body tempera- 
tures are due solely to vasomotor responses which remain active 
but not fully integrated even in the chronic midbrain dog (Keller, 
1960). However an explanation rather than an assumption is needed. 
These three questions — the effect of exercise, the course of 
fever, and the maintenance of normal body temperature at the usual 
ambient temperatures in the presence of damage to one or both of 
the dual centers — present fields for research rather than insur- 
mountable difficulties for the dual center hypothesis. However, neg- 
lect of these problems and continued overgeneralization on insuffi- 
cient evidence (such as was perpetuated by Strom (1960) in the new 
so-called Handbook of Physiology) will not lead to clarification of 
the problems of thermoregulation. These three questions were not 
considered in Ranson's review and there have been no answers in the 
past two decades. There has appeared, however, much that has been 
considered confirmatory evidence for the dual center theory and 
some work which may be contradictory. Some of the confirming 
studies will be briefly discussed, then some of the contradictory 
data, and finally some of my own recent work. 
In these intervening years there have appeared a number of 
papers which have purported to confirm the localization for the dual 
centers as outlined by Ranson. In particular there have appeared a 
number of reports from Scandinavian workers who have heated the 
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