INFLUENCE OF ORDER OF BIRTH, ETC. 



299 



English towns. The following table gives the death and delicacy 

 rates of 3,000 babies born in Bradford: 



Data from births in Sheffield yield closely parallel results : 



All of these results show that the death rate of infants is rela- 

 tively high for the first born and that it tends to decrease succes- 

 sively with the second and third and sometimes the fourth or 

 fifth born, after which there is a rise in the death rate which is 

 particularly high after the birth of the twelfth or thirteenth child. 



That the greater mortality of the first born is due to the same 

 causes which give rise to reduced size and weight is a conclusion 

 which, although having a certain amount of plausibility, it would 

 be rash to adopt, at least as an explanation of the whole difference 

 between the death rate of first and later born children. The first 

 born would naturally suffer more from the ignorance and inex- 

 perience of their mothers and there are other factors which would 

 affect unequally the various children of a family. Biological and 

 social factors may both affect the death rate of the first children 

 of a family, and it is a matter of great difficulty to assign to each 

 its proper role. Whatever may be the reasons why the first born 

 are handicapped in the first year of life, it is of much interest to 

 ascertain if this handicap persists in later years. Pearson and 

 some of his co-workers have maintained that this initial disadvan- 

 tage is correlated with a greater liability to tuberculosis, insanity 

 and other afflictions of adult life. As an illustration of the method 



