ROLE OF THE PROSENCEPHALON IN SHIVERING 
cold test it sought a warm pad and heating lamp when they were 
moved around the laboratory. On the third day of testing, 40 days 
post surgery, the animal was placed in a cage with another larger 
cat renowned for aggressiveness. After a typical display of ag- 
gression by the second cat, H promptly escaped from the cage 
when the door was opened. During the cold test the warm pad and 
heating lamp 'were placed in the cage with the aggressive cat and 
at the conclusion of the cold test H , with a rectal temperature of 
33 C and still not shivering, entereathis cage to stand on the warm 
pad despite the aggressive cat's auditory and somatic objections. 
Although the impairment of shivering in Cats No. F , ST 25 
and H , is such as to implicate the integrity of the dorsomedial 
posterior hypothalamus in the production of shivering, the above 
results do not indicate how little of this tissue can remain in order 
to permit effective shivering. In Cat No. H an attempt was made 
to destroy all of the tissue of the posterior hypothalamus except 
the dorsomedial region. As Figure 11 shows, this attempt was only 
partially successful. At the tuberal level of the posterior hypothal^ 
amus in this cat, most of the dorsolateral ri^t side posterior 
hypothalamus was destroyed but the dorsomedial tissue was pre- 
served on the left side. However, on the left side most of the dorsal 
tissue was destroyed at the posterior hypothalamic level (Fig. 11- 
Gat No. H B), but the dorsomedial region was preserved on the 
rig^t side. Since this cat could shiver effectively, this would sug- 
gest the ipsilateral preservation of the dorsomedial posterior 
hypothalamus tissue was sufficient to permit effective shivering. 
This point is further illustrated in Cat No. ST 24, in which the pos- 
terior hypothalamic lesions were bilateral but only overlapped for 
a distance of 0.75 mm approximately. However, at the level or 
region of overlap there was widespread dorsomedial posterior 
hypothalamic destruction except in that the ventral tissue within 
this region was still intact. This animal could shiver quite effective- 
ly. Similarly, Cat No. H could shiverquite effectively with all the 
dorsomedial posterior hypothalamic region destroyed on the right 
and partially on the left. Again the more ventral tissue within these 
boundaries was intact on both sides. 
In summary, these limited observations on 18 cats would sug- 
gest that ipsilateral preservation of the dorsomedial posterior 
337 
