ROLE OF THE PROSENCEPHALON IN SHIVERING 
It is not here the purpose to claim that the dorsomedial region 
of the posterior hypothalamus is an exclusive "center" for shivering. 
Figures 3, 14, and 26, and Table VIII illustrate EEC, heart and 
respiratory changes during stimulation of this region. Rather it is 
to suggest that activation of certain neurons within this region pro- 
duces shivering along with other ergotropic effects. 
Shivering limbs have a tremor frequency of 9 to 11 cycles/sec. 
This frequency was not effective in producing shivering when applied 
to an electrical stimulus to the hypothalamus. Stimuli of frequency 
25 to 100 pulses/sec were much more effective. This suggests that 
the rhythm of shivering is controlled peripherally, but shivering 
itself is instigated centrally. This concept will be elaborated at a 
later symposium. It helps to explain the paucity of information from 
Hess's laboratory (Akert and Kesselring, 1951, Hess, 1957) con- 
cerning the production of shivering during electrical stimulation of 
the prosencephalon. That is to say, when the brains of over 350 
anesthetized and unanesthetized cats were stimulated at about 7,000 
prosencephalic loci, shivering was observed but 11 times in 8 cats. 
The stimulus used in this laboratory consisted of a variable direct 
current that could be mechanically interrupted but 4 to 15 times/sec. 
If Hess had had the advantage of modern electronic stimulators per- 
mitting higher stimulation frequencies, he undoubtedly would have 
unmasked even more physiology of the diencephalon. 
Electrolytic Lesion Studies 
Methods. In these experiments bilateral electrolytic lesions 
were made in various hypothalamic regions of 29 cats. Each cat 
was anesthetized with pentobarbital sodium (35 mg/kgl. P.) and the 
head mounted in a stereotaxic frame. The scalp skin was reflected 
on appropriate holes burred through the calvarium to permit inser- 
tion of a stereotaxic ally oriented insulated monopolar electrode. 
Each electrode was 0.7 mm in diameter and without insulation 
approximately 1 mm from the tip. An electrolytic lesion was made 
by cathodal polarization of the electrode with a current of 1.5 to 
2.5 mA passed for 1 to 2 minutes. A remote anodal connection was 
provided on the tongue. The scalp skin was repositioned with wound 
327 
