MECHANISM OF DEATH 



315 



cells by repeated freezing and thawing as compared with 

 check cultures remaining frozen over longer periods of 

 time (Table 93). 



It was also found by the same authors that in milk, 

 bacteria are not decreased as much by freezing as in 

 water. 



Table 93. — Death by Continuous Freezing and by Alternate 



Freezing and Thawing 



(Numbers indicate plate counts per c.c.) 



Recently, extensive studies on the freezing of bacteria 

 and yeasts have been published by Tanner and William- 

 son (1928), not so much with the object of studying the 

 fundamental reactions concerned as to test the differences 

 of resistance of different species. The organisms were 

 frozen in small samples and kept at —13 to — 15°C.; 

 for each test, one of these samples was thawed and a 



