ROLE OF THE PROSENCEPHALON IN SHIVERING 
Within the region thus localized, it was not possible to demon- 
strate stimulation of a specific part as being more effective in 
producing shivering than any other part when the responses of one 
cat were compared to another. For example, Figure 5 illustrates 
the production of well defined shivering by stimulation of a locus 
1.5 mm from the midline (arrow B) in Cat No. ST 10. In the same 
animal, stimulation of a locus 0.5 mm from the midline (arrow F) 
produced a much less defined shivering response. Stimulation of a 
locus 2.5 ram from the midline (arrow A) produced a larger and 
slower limb oscillation response that could not, by independent 
observation, be termed "shivering." In contrast, in other cats (e.g., 
ST 9) there was a better production of shivering by stimulation of a 
locus 0.5 mm from the midline with a more discontinuous production 
of less well defined shivering produced by stimulation of a locus 1.5 
mm lateral to the midline. 
The parameters of stimulation were similar in each given 
experiment, but the intensity of stimulation necessary to evoke 
shivering varied from animal to animal, ranging from 200 ^ A/pulse 
to 1600 \xK/ pulse. The frequency of stimulation utilized ranged 
from 25 to 100 pulses/sec. In some experiments 25 pulses/sec 
seemed more effective in evoking shivering than 50 to 100 pulses/ 
sec, and in others 25 and 50 pulses/sec seemed more effective 
than 100 pulses/sec. With the exception of two experiments (Cat 
No. ST 17 and Cat No. ST 33 ) no attempt was made to explore 
systematically the frequency-intensity combination that would evoke 
shivering when repeatedly stimulating the same locus. Figure 6 
illustrates an experiment in Cat No. ST 33 in which the minimum 
intensities necessary to evoke shivering at stimulus frequencies 
of 10, 25, 50, and 100 and 200 pulses/sec were determined. In all 
cases the stimulus pulse duration was 1 msec, the period of stim- 
ulation 30 seconds, and the locus of stimulation the same. An attempt 
was made to clarify the results by gauging shivering response as 
being "strong," "mild," or "dubious." This classification was based 
on a combination of independent observations and the pattern of 
recorded EMG's. This is shown schematically at the top of Figure 
6. A response was classified as "strong" and coded as a filled- in 
circle if the electromyogram of at least one limb muscle recorded 
shivering for the durationof the stimulus. A response was classified 
as "mild" and coded with an open circle when visible shivering 
either began when the stimulus began but terminated before the 
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