INFLUENCE OF ORDER OF BIRTH, ETC. 



313 



Table Showing the Influence of the Age of the Mother on Birth Mortality, 

 Eliminating and not Eliminating the Effect of Order of Birth 



When the effect of order of birth is eHminated there remains a 

 very considerable correlation between the age of the mother and 

 the percentage of stillbirths. On the other hand, when the 

 influence of maternal age is eliminated there is after the first 

 birth little relationship between birth order and ante-natal 

 mortality. 



There is no reason to suppose that these effects of age depend 

 upon influences which may be properly described as hereditary. 

 They may be expressive of changes in the maternal organization 

 rather than any primary differences among the offspring. The 

 same may be said for the relation between age of parents and 

 height and weight of their children. The younger mothers tend 

 to bear the smallest children. When we deal with large numbers 

 of cases it is found that there is a slight increase of height and 

 weight as the age of mothers increases. A part of this is due to 

 the very evident increase of giant births (over 4000 gr.) with 

 increasing age of the mothers. (See Prinzing, Med. Statistik, 

 p. 52.) As Gini has shown, the apparent influence of age on the 

 size of offspring is really due mostly to order of birth. "The age 

 of the mother," he says, *'hr.s no decisive influence of its own on 

 the dimensions of the foetus; the increase which is found in these 



