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4-8 9-13 14-18 19-23 24-28 29-33 34-38 39-43 



DAYS AFTER ONSET OF HIBERNATION 



Fitnare 1. Tenipei.ilure-grovsth relations Ijelween a reprL'senlative number (j1 psychro- 

 philic baclena ami culifurni IjaciUi. 



mined. None of the coliform bacilli tested grew at temperatures 

 below 5° C. This would imply that little or no multiplication of these 

 organisms occurred in the intestinal tract of the animals while they 

 were in the hibernating state and it would be consistent with the 

 decrease in the counts as shown in Figure 1. The psychrophiles, on 

 the other had, grew well when incubated at temperatures down to 

 0° C. Although Ingraham and Stokes (19 59) report that some psychro- 

 philic bacteria have a maximum growth temperature above 37° C, 

 none of the psychrophiles isolated in our study gave evidence of 

 growth at temperatures above 35° C, During this study the average 

 duration of continuous hibernation was 6 days with extremes of 2 and 

 19 days. Between periods of hibernation the animals were active for 

 an average of 1.3 days, indicating that they were in hibernation ap- 

 proximately 82 per cent of the time. This figure must be considered 

 conservative, because it takes an active animal from 8 hours to 

 several days to become completely dormant, and the waking process 

 requires about 3 hours (Lyman and Chatfield, 1955). 



406 



