326 PHYSIOLOGY OF BACTERIA 



to high temperature. This is quite different from the behavior of 

 bacteria, or enzymes, or coagulating proteins. 



(c) THE CAUSE OF DEATH BY HEAT 



In trying to find the actual chemical or physical 

 changes in the cell causing death by heat, it will be 

 necessary to keep in mind the very high temperature 

 coefficient, and also the necessity of moisture. It has 

 been shown that death by dry heat is primarily an 

 oxidation process, with a temperature coefficient not 

 much above normal. This makes it certain that 

 oxidation cannot be the cause of death by moist heat. 



There are three groups of reactions which show high 

 temperature coefficients: the inactivation of enzymes, 

 the inactivation of toxins, and the coagulation of pro- 

 teins. Let us take the coagulation of hemoglobin which 

 was studied by Martin and Chick (1910) as an example. 

 Table 100 is a summary of their data and shows that 

 the coagulation of hemoglobin by heat is a time process 

 of measurable rate, but with a very high temperature 

 coefficient. The coagulation is a monomolecular process ; 

 this suggests either a hydrolysis, or a splitting off of 

 water. The temperature coefficient is 1.3 for 1°C. 

 increase, or 13.8 for 10°C. increase. The same authors 

 determined the temperature coefficient for the coagula- 

 tion of egg albumin (which is not a simple monomolec- 

 ular process, however) to 1.91 for VC or 646.0 for 10°C. 

 increase. 



Dried ovalbumin, heated to 120° for five hours, 

 remained perfectly soluble; the presence of water seems 

 to be essential for coagulation, and this again suggests 

 a reaction with water. 



The monomolecular process of the heat coagulation of 

 albumin has a striking similarity with the death by 



