FREEMAN, W. J. 
shivering could be abolished with minimal involvement of other 
activities of the animal. This was a simple logical deduction from 
our data and from the doctrine of centers. So, then, a series of 
lesions was made (Fig. 10) in these sites in 34 animals, 29 of which 
survived for at least three days. Ability to shiver was measured by 
rectal temperature or by oxygen consumption rate in response to a 
standard cold stress three, ten, and twenty-one days post-opera- 
tive ly. 
In eight cats there was a transient impairment, two of the cats 
having developed intercurrent respiratory infections (Fig. 10, 
"deficient"). A similar series of lesions in animals which never 
showed a deficit are shown on the other side. The location and size 
of the two sets of lesions was as close as can be expected with the 
various technical difficulties of placing bilaterally symmetrical 
lesions. 
So, then, this must be regarded as essentially an inconclusive 
experiment. There was some transient impairment of the ability to 
shiver in response to cold in a small proportion of the animals, 
approximately one-quarter of them. In the remainder, there was no 
deficit and yet these lesions corresponded rather closely to the 
areas in which it had been predicted they would produce a deficit 
of shivering. The question must be asked, why did this experiment 
fail? I do not think that one can blame technical factors. I think, 
rather, that one must look to the basic h5T3othesis to the doctrine 
of centers. I think that we assumed a degree of stability and of 
localization of function in the brain which does not exist. 
In the first place, we have underestimated the number of func- 
tions or the degree of functional complexity of this area. This 
structure must do many other things besides regulate shivering, 
if, indeed, it does that. This is reflected in the fact that most of 
our animals during the early post-operative period showed impair- 
ment of other functions as well, such as walking, grooming, eating, 
etc. 
I think, secondly, we have overlooked the plasticity of the brain. 
The basic phenomenon apparent in this set of studies is that the 
brain recovered the function lost immediately after operation. It 
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