MECHANISM OF DEATH 



319 



reproduced in the preceding table; the addition of 1 c.c. 

 of dead cells doubles the time required to kill Bad. 

 coll, and trebles the time for Micr. pyogenes. It is 

 necessary that the added dead cells come from a young 

 culture. Old cells exert no protective action. 



(b) THE ORDER AND RATE OF DEATH AT DIFFERENT 

 TEMPERATURES 



In the killing of bacteria by moist heat, the logarithmic 

 order is generally quite well established. Most of the 

 examples given in the chapter on the order of death 

 refer to death by heat. As typical examples, we may 

 mention (see Table 96) the death of Bad. coli at 48.9°C. 

 and 52.7°C., by Chick (1910) and the death of the spores 

 of B. anthracis at 80°C., 84°C. and 90°C., by Eijkman 

 (1912/13) of which only the survivor curves are given in 

 Fig. 31, p. 281 showing straight lines. 



The computed death-rates are sufficiently constant to 

 be used for the computation of the temperature coef- 



