310 PHYSIOLOGY OF BACTERIA 



of the initial number of viable cells. From these times, 

 the temperature coefficients of Table 91 could be 

 obtained. 



The results are fairly consistent with the exception of one too 

 high value in the first series. If the range from 30°C. to 60°C. is 

 taken in toto, the temperature coefficient is 10.2 or 7.96, just which, 

 depends on whether seventy-six or one hundred sixty minutes is used 

 as the correct time. 



The temperature coefficients for the entire range of the three 

 experiments are 8.34, 5.77 and 3.53 respectively. This difference 

 is very great. There are at least two possibilities that might account 

 for this difference: the stratum on which the yeast was dried; and 

 also, that no effort was made to dry the yeast to the same degree of 

 dryness. The varying moisture content would very likely affect 

 the temperature coefficient greatly, since the coefficient of death 

 by moist heat is very high. 



Despite several inconsistencies in the results, the data 

 are entirely sufficient to show that the chemical process 

 of dying of dry bacteria is not essentially influenced by 

 the change from '' growing temperatures" to ''killing 

 temperatures." At 30°C. and 37°C., the yeast would 

 have shown good growth in a suitable medium, while at 

 50°C., in the same medium, the yeast would have died. 

 This great contrast has been entirely eliminated by the 

 absence of water. No inactivation of enzymes or 

 coagulation of proteins by supramaximal temperatures 

 takes place because these processes require moisture. 

 Death is altogether controlled by oxidation, which is a 

 normal chemical process. 



The dry micrococci of Paul's are reduced from 100 living cells 

 to 1 in thirty-three days at 17°C. (Table 87). Calculating with a 

 constant temperature coefficient of 2.5, the same reduction would 

 require 



at 67°C. 33 ^ 2.5^ days = 8 hours 7 minutes 

 at 97°C. 33 -^ 2.5^ days = 31 minutes 



