1 86 Dynamic Evolution 



those which do survive, the children of old 

 parents live longer than those of young 

 parents. 



Infant death occurred most frequently to 

 the last child of the family, and indicated 

 failing health of the parents. When an 

 infant death occurred in the middle of a large 

 family it was noted that with great frequency 

 the nearest child, before or after the infant 

 death, lived a less length of time than the 

 other children. These facts indicate periods 

 of ill health on the part of the mothers at 

 about the times of the infant deaths. We may, 

 therefore, revise the former statement and 

 say that as long as parents retain their health 

 and vigor, the older they are the greater will 

 be the natural longevity of their children. 



A partial, but no systematic investigation 

 was made into the effects of several successive 

 generations of late reproduction on longevity, 

 with indications that the effects are cumula- 

 tive in the same way that mental and physi- 

 cal energy is cumulative. Thus, several 

 families were found which had four or five 



