STUART, D. G. 
given region until shivering had been continuous in at least one 
limb for a period of 5 minutes. In two of these experiments the 
fornices had been sectioned at a more caudal level one week prior 
to experimentation. In six additional experiments the intensities 
of stimulation needed to suppress shivering during septal, anterior, 
and posterior hypothalamic stimulation were compared. In two of 
these experiments the relative inhibitory effects of various stimuli 
frequencies and pulse durations were noted. 
The surgical, electronic, brain fixing, sectioning, staining, and 
electrode tract reconstruction techniques were similar to those 
described above. 
Results. In order to explore systematically the septum and 
posterior hypothalamus for loci whose stimulation suppressed shiv- 
ering, it was considered advisable to use cats anesthetized with 
pentobarbital sodium. This was done because continuous shivering 
occurs spontaneously in the waning stages of such anesthesia. If 
the intensity of stimulation necessary to suppress shivering is kept 
constant in each mapping experiment, it is important that such an 
experiment be conducted in as short a time as possible so that the 
preparation can be stimulated at a relatively constant level of anes- 
thesia. Since it was arbitrarily decided that no locus would be 
stimulated until shivering had been active and continuous for the 
preceding 5 minutes, it was necessaryto utilize a stimulus intensity 
that would clearly produce a suppression of shivering when applied 
to an "active" locus without a concomitant long post- stimulation 
period of suppressed shivering. 
Figure 19 illustrates this point. In this experiment on Cat No. 
ST 22, continuous shivering was occurring in the waning stages of 
pentobarbital sodium anesthesia. Stimulation of a dorsal supraoptic 
locus evoked a short and mild suppression of shivering 5 seconds 
after the cessation of stimulation. The intensity of stimulation was 
200 M A/pulse. Five minutes later a stimulus intensity of 300 ju A/ 
pulse applied to the same locus evoked a suppression of shivering 
in the latter half of the 30- second stimulation period. Shivering 
resumed immediately post- stimulation. Five minutes later stimu- 
lation of the same locus with a stimulus intensity of 400 n A/pulse 
evoked immediate suppression of shivering, and shivering did not 
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