Longevity 181 



there is a second deduction from general 

 principles and the known habits of human 

 beings, the conclusion of which is that the 

 older the parents the greater is the percent- 

 age of infant mortality. The "infant mor- 

 tality" used in this investigation was all 

 deaths occurring between birth and twenty- 

 five years of age, and the brothers and sisters 

 compared for longevity were those which 

 died after arriving at twenty-five. Only 

 those families were used which had four or 

 more adults living long enough to be in- 

 cluded in the table. The average number per 

 family was about six. 



In preparing the table a sheet of paper was 

 used having vertical columns, and at the 

 heads of the columns were placed the num- 

 bers "21," "22," "23," etc., representing 

 the ages of the fathers at the births of the 

 children recorded in the columns below. If a 

 family had one child when the father was 25 

 and living to the age of 60, a second child 

 when the father was 27 and living to the age 

 of 65, a third child when the father was 30 



