THE METABOLIC ACTIVITY OF VERTEBRATES 77 



AO 



12M 12N 12M 12N 12M 12N 12M 12N 12M 12N 12M 12N 12M 

 Time of day 



Fig. 23. 



The brain temperature recorded from a ground squirrel as it begins 

 to enter hibernation (After Strumwasser F. : Am. J. Physiol Vol 196 

 1959). 



lowered from 37°-35°-30°-27°-23° before the animal enters 

 hibernation. It is apparent that by this mechanism the condition 

 of the overall metabolic control is being tested in order to see 

 whether it is all co-ordinated for entry into this quite new state. 

 During hibernation the temperature is low but is maintained 

 quite accurately at a given level, in some cases 10-05° C. of a 

 temperature several degrees higher than the environment. While 

 in hibernation the nervous system retains a certain amount of 

 activity although the cortical waves may be lost in the hamster. 

 The ground squirrel Citellus still shows cortical waves of 10/ 

 second but reduced amplitude at 5° C. It can localise sounds as 

 well as make small sounds itself when slightly disturbed at brain 

 temperatures of 6- 1 ° C. 



Arousal from hibernation is a relatively rapid process and is 

 associated with an enormous increase in oxygen consumption. 

 In hamsters, the metabolism may increase 2-4000 times as the 

 temperature rises to 37° C. within two hours. It is apparent that 

 the whole state of the organism during hibernation is a special 



