HEMINGWAY, A. 
corticospinal tract, not that the entire pathway is there. Some of the 
fibres are intermingled with corticospinal fibres. 
DR. HEMINGWAY: Dr. Birzis destroyed the corticospinal tract 
in the medulla in acute experiments. She tested them two or three 
hours after the lesions were made and observed no shivering. Some 
lesions were large, some were small; but whenever the corticospinal 
tracts were destroyed, the animal did not shiver. 
DR. CLARK: We do not know anything about the path below the 
midbrain, but it is quite definite that some of the fibres that mediate 
shivering are intermingled with corticospinal fibres in the midbrain. 
DR. FREEMAN: Both she and I looked for unit activity in the 
cerebral peduncles in the midbrain but were not able to find any. 
However, this may be, as you point out, a statistical distribution 
problem . 
DR. CLARK: With the number of fibres in this area, attempts 
to get unit activity from a particular type are like reaching into a 
bucket to pick out the one black marble. 
DR. FREEMAN: Well, in that case, it would be the Mexican 
jumping bean in the marbles. 
DR. HEMINGWAY: Dworkin observed shivering in decerebrate 
preparations, but others have failed to confirm this. Stuart and 
Bard have observed a tremor in decerebrate preparations, but this 
tremor is ineffective metabolically. 
DR. CLARK: From the work we have on the way the temperature 
falls, I would say it is not very effective, although it is still shiver- 
ing, 
DR. STUART: Rather than shivering, I would say "intermittent 
muscular activity" that has no thermoregulatory function. 
DR. CLARK: I would not say that because it appears and dis- 
appears according to the temperature. 
30 
