HIBERNATION IN MAMMALS— LYMAN and CHATFIELD 



97 



I 234567 89 10 



DAYS IN HIBERNATION 

 Fig. 10. — The weight of seminal vesicles of castrated hamsters which hibernated for various 

 periods of time after injection of testosterone, compared with hamsters which did not hibernate. 

 The mean and standard deviation of ten untreated castrates provides a base line. 



300 

 Ul 

 :3 200 



_1 

 o 



^ 100 



: EXTREMES, WARM ROOM CONTROLS 

 MEAN.WARM ROOM CONTROLS 

 MEAN, COLD ROOM CONTROLS 

 NO, 592,7DAYS HIBERNATION 

 NO 655, 520AYS HIBERNATION 



DAYS 



Fig. n. — Effect of cold and hibernation on growth of tumor. In curves #3 and #4, the 

 dotted horizontal portion of each line indicates when the animal was hibernating ; the solid 

 portion indicates when it was awake. 



Since irradiation affects mitosis, it seems reasonable that the lack of cell division in 

 hibernation temporarily protects the animal from injury.^*'*^** 



Periodic wakings from hibernation. All reported laboratory experience indi- 

 cates that the hibernating mammal wakes from time to time during the hibernating 

 period and that these wakings are more frequent at the beginning and end of the 



«K. C. Brace (Blood 5; 648, 1953) has indicated that the life span of the woodchuck 

 erythrocyte is increased by exposure of the animal to cold, with a further increase of life span 

 during hibernation, but the number of animals used is so small that the results are not conclusive. 



