INFLUENCE OF ORDER OF BIRTH, ETC. 311 



Closely associated with the effect of order of birth upon off- 

 spring is the problem of the influence of parental age. This topic 

 has received more or less attention from the time of Aristotle to 

 the present. Various opinions have been put forth with a degree 

 of confidence which is often in inverse proportions to the ade- 

 quacy of the evidence upon which they were based. The subject 

 is more difficult than appears upon the surface, and, like the one 

 that has just been discussed, presents many pitfalls. Without 

 troubling ourselves with theories which are unsupported by 

 statistical data let us consider some of the more important 

 contributions to the solution of our problem. 



With the increasing age of parents there is apparently an 

 increased percentage of abortions and stillbirths 11 we except the 

 offspring of .very young mothers. Data from Paris and Buda- 

 Pest are given in the following table from Prof. Gini: 



Relations of Age of Parents to Percentage of Abortions and Stillbirths 



Here it is shown that with the exception of some irregularities 

 in the first horizontal column giving the percentage of miscar- 

 riages and stillbirths of mothers below 20 years of age, there is 

 a general increase in the percentage of both miscarriages and 

 stillbirths as the age of the mother increases. Both kinds of 



American men of science (Sci., Mar. 5, 1917), and by the (as yet unpublished) 

 researches of two of my students. 



