198 THE TREND OF THE RACE 
show that in a region that has a high infant death rate, the death 
rate for older children is higher than it is in some other region 
with a low infant death rate. What we want to know is whether 
the child death rate is less than it would have been under the same 
conditions if the infant death rate had not been so high. If it 
should be found that a high infant mortality is generally followed 
some years later by a reduced child mortality of the same group 
and under the same environment the evidence would point to the 
selective value of early mortality. 
An investigation of this problem was made by Mr. E. C. Snow 
whose memoir on The Intensity of Natural Selection in Man con- 
tains evidence of much painstaking and critical labor even though 
it may leave something to be desired in the way of lucidity of expo- 
sition. The data for one study were taken from the Reports of the 
Registrar General for England and Wales, and those for another 
were obtained from the vital statistics of Prussia. Correlations 
were worked out for various districts of England and Prussia 
between the mortality of early life (1-3 years in different cases) 
and the mortality of subsequent age intervals. After many 
corrections for environmental differences and the variable sizes of 
the cohorts, the data were found to show a negative correlation 
between the death rates of early periods and those of later periods 
of life. In other words, a relatively high death rate in the first 
period renders the death rate of the survivors in the subsequent 
period less than it otherwise would have been. Such a result is 
not inconsistent with the conclusion stated previously, that cer- 
tain regions have a relatively high death rate for several succes- 
sive years. There may be a more severe selection all through life 
in one group than there is in another. 
It would be a matter of interest to ascertain, though the 
problem would present many difficulties, whether the death rate 
tends to be less selective, or in other words more indiscriminate 
as we approach the period of birth. A priori, this would seem 
to be very probable. There may be some truth in Dr. D. S. 
Jordan’s statement that ‘‘a strong child can be killed almost as 
readily as a weak one when it is very young,” and it is when 
