DISINFECTANTS 79 



5 and 10° it may be 5 to 8, between 10 and 15°, about 3 

 to 4, and it thus gradually approaches the value of 2 to 3 

 which we find near the optimal temperature. The energy- 

 furnishing processes behave similarly. Although en- 

 zymes continue to function below the minimal tempera- 

 ture of growth, down to the freezing point (Foter and 

 Rahn, 1936; Rahn and Bigwood, 1939), their temperature 

 coefficients increase greatly near the freezing point. 



Quite contrary to growth rate, death rate displays a 

 fairly uniform temperature coefficient as far down as 

 the freezing point. While the number of experiments on 

 record on that subject is not great\ there is no instance 

 showing an increase similar to that of the life functions. 

 Death proceeds more slowly at lower temperatures, but 

 the decrease of the rate is very slight, its Qio is about the 

 same as at 20 or 30°, and not several times as large, 

 as we find it with growth and fermentation. The state 

 of dormancy induced by low temperature does not in- 

 terfere with death by chemical poisons. 



Since death is a destruction of the mechanism of 

 growth or cell division, the constancy of the temperature 

 coefficient indicates that the essential molecules involved 

 in this mechanism are not impeded much by low tem- 

 peratures in their reactivity with poisons, while they 

 are impeded in their reactivity with metabolites. This 

 is important for the explanation of the great retarda- 

 tion or complete inhibition of growth and energy pro- 

 duction of the cell. 



One of the several theories offered to account for this 

 phenomenon is that of an increase in viscosity of the 

 protoplasm. According to Belehradek (1935, p. 160), 

 ''such an increase would considerably hinder free move- 

 ments of reacting molecules with the result that the 

 biochemical reactions in the cell would be brought to a 

 standstill." But the hindering of free movement of re- 



1. See Table 16. 



