SYMPOSIUM ON PUBLIC HEALTH PROBLEMS 79 
there would be but one type of mammal or one type of life. 
By using “the words nature and nurture for the terms 
heredity and environment” and thinking of a living being not 
as nature alone, nor as the sum of nature and nurture, but as 
the product of nature and nurture, we can, I think, more readily 
see that effective work in the reduction of infant mortality re- 
quires the ascertainment of the social, economic and civic 
factors involved. 
An infant with the most favorable heredity will most cer- 
tainly succumb if exposed long enough to the fumes of illum- 
inating gas, hence we guard it against such exposure and we 
guard it also against exposure to damp and to cold draughts— 
even though there be no respiratory taint in its heredity. 
Things that kill and weaken do not invariably attack the unfit, 
they sometimes kill the fit or make them unfit. 
The Children’s Bureau has no administrative functions. It 
has been ordered by Congress to “investigate and report,” 
and it is seeking to ascertain the degree of coincidence that 
exists between various social, economic, and civic factors, and 
a high or low infant mortality rate. 
Its method of studying infant mortality is to secure 
data directly from the mother by visiting her after at 
least one year has elapsed since the birth of her child, even 
though the child may have been stillborn or may not have sur- 
vived a full year. Some of the questions are very intimate and 
personal, but our refusals have averaged less than one per 
one thousand mothers interviewed. 
Our findings thus far indicate that a high infant mortality 
rate is a definite, significant symptom of defective social and 
economic conditions, but it is exceedingly difficult to measure 
the relative importance of each factor. 
On account of poverty a mother may remain ignorant of the 
simple rules of hygiene that might promote her own and her 
baby’s health. Or, on the other hand, she may well know the 
advantages of fresh air, cleanliness, sunlight, and proper food 
for herself and baby, but be without the necessary facilities for 
ventilating her home, or without time or means to secure 
cleanliness and other wholesome conditions that she appre- 
1 C. W. Saleeby, M.D., ‘Nature and Nurture,” Nat. Health, London, Mar. ’16, 
