LOGARITHMIC ORDER OF DEATH 



25 



the cells are not of uniform resistance. Our assumption, 

 then, seems to disagree with the facts. There is no 

 contradiction, however, since the assumption does not 

 deny the actual existence of a graded resistance, it merely 

 states what is the consequence of a uniform resistance. 

 But there is a point where the theory of the loga- 

 rithmic order of death is in direct contradiction with the 

 theory which explains the mortality curves by a graded 

 resistance. If the typical mortality curve of higher or- 

 ganisms, which is spread over a certain length of time, 

 were due to a gradation in resistance, a uniform resis- 

 tance should result in crowding the death of all indi- 

 viduals into the same instant. This last point is pre- 

 cisely what is contradicted by the theory of the logarith- 

 mic order. 



To illustrate this point, let us assume a population of 

 tadpoles killed by heat, where death occurs when n = 

 100 brain cells are incapacitated. Three grades of re- 

 sistance are assumed to be present, characterized by sur- 

 vival rates of 10%, 20% and 30%, respectively; the pop- 

 ulation consists of 100 individuals of each grade. Table 

 3 and Table 5 give the mortality for each grade and Table 

 5 gives also the mortality for the entire population. Fig- 

 ure 6 illustrates the fact that tadpoles of the same re- 

 sistance do not die at the same moment, and that the 

 maximum mortality occurs later and later, as the re- 

 sistance increases. The composite mortality curve for 



TABLE 5 

 Calculated mortality curve of a population consisting of organisms 

 of three groups of different resistance. 



Number 



of 



Individuals 



Group I: 100 

 Group II: 100 

 Group III: 100 

 Total: 300 

 Percentage 



Survival 

 rate per 

 minute 



Number of individuals dying per minute 



