HIBERNATION IN MAMMAl.S— LYMAN and CIIATFIELD 



101 



scribed in the marmot and woodchuck by Duljois"- and Benedict and Lee/'"' in the 

 thirteen-Hned ground squirrel l)y Johnson,-- and in the hedgeliog by Chao and Yeh."^ 

 That the temperature gradient during arousal is dependent on differential vaso- 

 constriction was demonstrated by injecting a radio-opa(|ue Hquid (Thorotrast) into 

 the hearts of both normal anaesthetized hamsters and animals waking from hiberna- 

 tion.123 X-rays taken 3 seconds after the injection in normal anaesthetized animals 

 clearly outlined the whole circulatory system. In contrast, only the cranial portion 

 of the arterial system was outlined in the waking hiliernator, and 30 seconds or more 

 after the injection there were still only slight indications of circulation to the kidney, 

 viscera and femoral arteries. There was no evidence in the X-rays of a possible 

 arterial coarctation, nor could one be demonstrated by serial histological sections 

 of the aorta (fig. 14). 



Fig. 14. — Thorotrast injected into heart of normal anaesthetized hamster and hamster waking 

 from hibernation. A and B, normal hamster 2 and 9 seconds respectively after start of injection. 

 C and D, waking hibernator 4 and 35 seconds after start of injection. 



