CLARJC, G. 
and there was no shivering. The results of these tests, which were 
performed months after the operation, are similar to those seen in 
chronic midcollicular preparations. Figure 15 illustrates the res- 
ponses of these same two dogs to a heat load. In one dog there was 
no deviation from the normal and in the other only a slightly higher 
temperature (Keller, 1950). These dogs, then, are the fourth type 
required by the dual center theory, that is, animals with much dis- 
turbed regulation against cold but with little or no disturbances 
against heat. This latter finding, though, does raise some serious 
difficulty with the localization of dual centers as proposed by Han- 
sen. The lateral limits ofthe lesion apparently include the postulated 
pathway from the anterior center for regulation against heat. Either 
there are descendingfibers further laterally than had been originally 
thought or some other lower center is concerned. Neither of these 
questions can be answered by the available data. 
There has appeared one paper (Sherwood, Massopust,McCruin, 
and Buchanan, 1954) on the localization in the hypothalamus of the 
rat of thermoregulatory integrating processes. In this species it 
was found that bilateral lesions involving any portion of the lined 
area shown in Figure 16, whether anterior, posterior, or tuberal, 
resulted in an inability to maintain normal body temperature when 
exposed to a cold load. There was no mention of usual body temper- 
atures of these rats in the animal room nor of any heat load tests. 
It is probable that they were tested entirely too soon after operation 
but the findings are not compatible with current dual center theory. 
It was mentioned earlier that Birzis and Hemingway had been 
able to elicit shivering in cats by electrical stimulation. In their 
experiments the active areas fit in very well with the dual center 
concept; however, there are two other reports of the electrical 
elicitation of shivering. The earliest of these is that of Akert and 
Kesselring (1951). This was a part of the findings in the long series 
of studies of the effects of stimulation of the brain in unanesthetized 
cats conducted in the laboratory of Hess. In this series there was 
one cat in which stimulation in a location similar to that reported 
by Birzis and Hemingway (1957) elicited shivering but in the other 
ten cases the active region was adjacent to the lateral ventricle and 
included six locations in the septum pellucidum, three in the caudate 
nucleus, and one in the anterior thalamus. There is no mention of 
how often stimulation inthese same locations did not elicit shivering. 
168 
