26 



LOGARITHMIC ORDER OF DEATH 



the total population is still a regular mortality curve, 

 drawn out over a longer time than the curves of each 

 grade. If the time scale is reduced to one-half, as in 

 Figure 6a, (which gives the mortalities : 12.7, 63.4, 21.2, 2.4 

 and 0.1 for successive 2-minute intervals) the shape of 

 the curve is the typical one. Curves and Tables show 

 that it is not only the sensitive cells that die early, and 

 not only the resistant ones that survive for the longest 

 time ; in both groups there is a small percentage of cells 

 of different degrees of resistance. 



Fig. 6a 



Fig. 6. Mortality curves of three groups of organisms representing 

 different grades of resistance (thin lines) and of a population con- 

 sisting of equal numbers from each of the three groups (heavy line). 



Fig. 6a. Curve of the composite population of Fig. 6 on a reduced 

 time scale. 



TABLE 6 

 Number of survivors in a population of 100 organisms, calculated 

 on the assumption that the death of n out of 10 cells kills one organism. 

 Comparison of n definite versus n random cells. The survival rate 

 of the cells is assumed to be 90% per minute. 



In the case of n definite cells 



