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: 
Order of Birth I 2-3 | 4-5 | 7-6 | 8-9 | ro-1r | 12+ 
Death rate in 1st year...... 16.2 | 12.4 | 13 143 | T7s4 Lazee- 3343 
Delicacy rate in rst year....| 3.9] 4.2] 5.7] 6.5] 6 8.3 9 
Both combined............. 20.1 | 16.6 | 18.7 | 20.8 | 23.4 | 26 42.3 
Data from births in Sheffield yield closely parallel results: 
Order of Births I | 2 | 3-4 |5-6| 7-8 |o-1o|rz-12|73+ 
Total Births... gees wie mame 2 ak 636 
Death rate in 1st year per 1,000 births|12.9 
691} 1156} 843] 518) 334] 143 | Io 
I1.6]11.5 |10.6/12.6]16.2/11.9 |24.8 
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 réle. 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 
