176 BIOLOGY OF DEATH 



death rate dependent upon the inherited constitution, and 

 the percentage not so dependent. If pN be the number 

 of deaths in N cases which depend in no way upon the 

 inherited constitution of the individual, then (1-p) will 

 represent the chance of an individual dying because of 

 his inherited constitutional makeup, and (1-p) 2 will be 

 the chance of a pair of individuals, say two brothers, both 

 dying from causes determined by inheritance. If further 

 r denotes the observed correlation between individuals in 

 respect of duration of life, and r Q the correlation between 

 the same kin in respect of such measured physical charac- 

 ters as those just discussed, in the determination of which 

 it is agreed that environment can play only a small part, 

 we have the following relation: 



Substituting the ascertained values we have 



1. From parental correlations. 



0.1365 = .4675 (1-p) 2 



(1-p) 2 = .292 



(1-p) - .54 



2. From fraternal correlations 



0.2831 = .5156 (1-p) 2 

 (1-p) = .74 



From these figures it may be concluded, and Pearson 

 does so conclude, that from 50 to 75 per cent, of the 

 general death rate within the group of the population on 

 which the calculations are based, is determined funda- 

 mentally by factors of heredity and is not capable of 

 essential modification or amelioration by any sort of 

 environmental action, however well intentioned, however 

 costly, or however well advertised. Mutatis mutandis 

 the same conclusion applies to the duration of life. I have 



