48 



LOGARITHMIC ORDER OF DEATH 



peratures near this maximum, the survivor curve be- 

 came definitely concave downwards (Fig. 11). If we 

 realize that with many species the synthesis mechanism 

 can reproduce all the parts of a cell in 15 to 30 minutes, 

 it is not surprising that the effect of repair becomes 

 perceptible when the process of dying is extended over 

 several hours. 



The following simplified analysis might make clear 

 the writer's conception of the interaction between death 

 and repair. Let us assume that death is brought about 

 by the inactivation of the mechanism of cell division and 

 that the earliest phase of this process can be reversed by 

 the synthesis mechanism. Let the rate of injury be 50% 

 (that is, affect 50% of the cells) per hour, and the rate 

 of repair during the first hour be 40%. Then, only 10% 

 of the cells cannot be repaired, and the death rate is 10%. 

 But, the harmful environment affects not only reproduc- 

 tion, but also the synthesis mechanism which, we as- 



Fig. 11. Death by heat of Torula cremoris. This graph shows that 

 different types of curves may be obtained when death is slow (at 48°) 

 and when it is rapid (at 49.1°). From data of Woerz, 1931, unpub- 

 lished.) 



