STUART, D. G. 
during septal stimulation, it was observed during posterior hypo- 
thalamic stimulation. In the three cats (No.'s ST 14, 15 and 17) in 
which shivering was observed during septal stimulation, a more 
intense and less latent shivering was produced by the same or less 
intense stimulation. In Cat No. ST 5, the comparison is hardly 
valid in that the septum was stimulated 3.5 hours after induction 
of alpha chloralose anesthesia and the posterior hjrpothalamus was 
stimulated 9 hours post medication. That is to say, the preparation 
may have been at too deep a level of anesthesia to shiver during 
septal stimulation. However, in all other cats the stimuli were ap- 
plied to the two loci within a short period of time of each other. 
Figure 14 illustrates the comparisons for Cat No. ST 17. In this 
figure there are schemata of septal loci labelled 1 and 2, 2 being 
2 mm ventral to 1. The posterior hypothalamic loci 1 and 2 are 
within the previously determined dorsomedial region whose stimu- 
lation evokes shivering. The hypothalamic locus denoted 2 is 1 mm 
lateral and 1 mm ventral to the locus marked 1. Loci posterior 
hypothalamus 2 and septum 1 were stimulated for 30 seconds at 
50 pulses/sec with a pulse duration of 3 msec. In both cases shiv- 
ering was produced, but the stimulus intensity necessary at the 
hypothalamic locus was only half that necessary at the septal locus 
(800 /iA/ pulses vs. 1600 /.lA/pulse). Additionally, as shown in 
records No. 4 and 5 for the loci in Figure 14, shivering was more 
intense and appeared with less latency during hypothalamic than 
during septal stimulation. Loci posterior hypothalamus 1 and sep- 
tum 2 were stimulated for 60 seconds using the same frequency and 
pulse duration. As shown in records 4 and 5 for these loci, shiv- 
ering was less intense during the septal stimulation and required 
a stimulus intensity double that used during hypothalamic stimu- 
lation. These loci were stimulated in the order posterior hypothal- 
amus 2, septum 1, septum 2 and posterior hypothalamus 1 at 22.3, 
23.5, 23.6, and 24.5 hours after induction of alpha chloralose anes- 
thesia (60 mg/kg I. P.). The rectal temperature during stimulation 
of these loci was 37.8 C, 37.8 C and 38.8 C respectively. In all 
these cases the environmental temperature was 28 C . These results 
indicate that shivering can be induced by electrical stimulation of 
sensitive loci in both the hypothalamus and the septum, but the 
sensitivity of the hypothalamic loci is considerably greater than 
that of the septal loci as revealed by the necessary intensity of 
stimulating current and the EMG response. The EMG of the hind- 
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