TEMPERATURE REGULATION "CENTERS" 
to the completed process, e.g. frequency, rhythm icity, and intensity. 
But it is also proposed that these same structures are active during 
all other kinds of behavior produced by the intact nervous system, 
and that the essential nature of the contribution of each would, in 
some sense, be the same as that during shivering. The precise 
pattern of output would be determinedsolely by the previous pattern 
of input. 
CONCLUSION 
It can be said finally that even where the available evidence 
indicates the existence of a center in the classical sense, such an 
achievement can no longer be regarded as a satisfactory end point. 
For, if it be demonstrated that stimulation of a given structure 
will produce shivering, or, for that matter, feeding, non-feeding, 
rage, sleep, sexual behavior, etc., it must be recognized that the 
stimulus evoking this is not normally present in the brain. Where 
then does it normally come from? What is the nature of the cellular 
activity that the electrical stimulus has produced; and how does 
this compare with the normal pattern of electrical or cellular 
activity? How is this normal pattern brought into being by afferent 
fibers? Is a transmitter substance involved? Are there chemical 
gradients of ions moving in response to endogenous electrical fields? 
What is the nature of the efferent activity? These are all questions 
which are now within the realm of analysis and I think should con- 
stitute the bulk of work in neurophysiology in future decades. 
The conclusion of this review is that the various parts of the 
brain may not be so organized as to subserve particular functions 
throu^ the increased activity of particular parts, the other parts 
then remaining quiescent. It is suggested, rather, that during most 
reflex activities, virtually all parts ofthe brain are active, that each 
part of the brain contributes some basic element to all types of 
reflex activity, and that distinctive spatial-temporal patterns of 
behavior are determined largely by the pattern of sensory stimula- 
tion, which is maintained before and duringthe activity. In this view 
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