HISTORICAL REVIEW 
DR. CLARK: Well, it is not a strong shiver, and you have the 
problem of defining shivering. If you have your hand on the hind 
quarter of such a dog, you can feel a trenoor which disappears when 
the animal is warm and shows up when he is cold. It is not enough 
to maintain normal temperature levels, but it is definitely there. 
DR. STUART; Have you ever observed shivering following 
complete destruction of the preparation's cerebral peduncle? 
DR. CLARK: Yes, but not as much as in the preparation with 
partial destruction. In the complete transection, if you lower his 
temperature to 29 G, quite frequently you can feel a tremor. Bard 
has found the same thing in his cats. 
DR. FREEMAN: This phenomenon of an increased thermogen- 
esis with some portions of the nervous system still intact would 
imply that there is some descending activity which potentiates shiv- 
ering that is set up in the spinal cord, or that there are parts of the 
brain stem affected by the external cooling. Have you attempted to 
stimulate electrically in various portions of the brain anterior to 
the sections to see if you can increase this effect? 
DR. CLARK: No, we have not. I would like to point out that we 
do not feel that these animals are truly poikilothermic. The fact 
that they still retain some indication of panting, some indication of 
shivering, indicates they are not poikilothermic. In addition, they 
show something in the way of vasomotor control. Thus, if you take 
a midbrain dog and lower his temperature into the cold and then 
bring it back into the warm, his skin temperature would jump up 
rather more rapidly than you would anticipate on the basis of simple 
rewarming. Consequently, we have fairly good evidence that, in the 
dog at least, there is some vasomotor control in the midbrain 
preparations. 
DR. HEMINGWAY: Would you care, Dr. Clark, to comment on 
Dr. Keller's statement that the descending pathways for shivering 
are in the corticospinal tracts. 
DR. CLARK: I think that this is one of his points which has 
been misinterpreted. He states that some of the fibers are in the 
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