STUART, D. G. 
become active and continuous until 10 minutes post the cessation of 
stimulation. In all cases the stimuli had a frequency of 25 pulses/sec 
and a pulse duration of 1 msec. On the basis of such observations, 
it was arbitrarily decided to use a stimulus intensity that would 
evoke the second, rather than the third, suppressive response. 
Figure 20 illustrates a typical experiment in which spontaneous 
shivering was suppressed by electrical stimulation. In this experi- 
ment on Cat No. ST 22, the stimulus frequency was 25 pulses/sec, 
the pulse duration 1 msec, and the stimulus intensity 800 ^ A/pulse. 
Each fifth minute, a locus was stimulated in the order A, B, C, D, 
E, and F. As shown, shivering was not suppressed during stimulation 
of locus A. It was mildly suppressed during stimulation of loci B, 
D, and E, and strongly suppressed during stimulation of loci C and F. 
Figure 21 summarizes the results for 8 cats in which the septum 
was systematically explored for loci whose activation suppressed 
shivering. The schemata of Planes A and B and the loci numbers 
have been described previously. An intermediate frontal plane was 
systematically explored, but the results are not listed. Similarly, 
loci were stimulated at 1 mm depths, but the results are not listed 
for these intermediate loci. In Cats No. ST 19 and ST 31, both the 
left and right sides of the septum were stimulated. Cat No. ST 19 
was under alpha chloralose medication. InCatNo. ST 31, an attempt 
was made to destroy the right side fornix at a more caudal level 
one week prior to experimentation to permit degeneration of pre- 
commissural fornical fibers. In Cats No. ST 27 and ST 29, an attempt 
was made one week prior to experimentation to destroy the fornix 
bilaterally at a more caudal level. By "mild suppression" it was 
meant that shivering stopped for part of the stimulus duration, while 
in "strong suppression" the activity was suppressed for the entire 
stimulus duration. 
The results indicated that stimulation of ventromedial (loci 7, 
8, and 16) and ventrolateral (loci 4 and 12) midseptal and posterior 
septal regions consistently evoked asuppressionof shivering. Stim- 
ulation of extreme dorsal regions (loci 1, 5, 9, and 13) tended not 
to suppress shivering, but some variability of response existed. 
Stimulation of intermediate regions (loci 2, 3, and 6) suppressed 
shivering in some cats and not in others. Stimulation of locus 11 
never suppressed shivering although stimulation of locus 10 some- 
times and locus 12 always suppressed shivering. In every experiment 
the responses listed were reproducible. 
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