164 THE TREND OF THE RACE 
between a high birth rate and a high infantile death rate is not 
simply a matter of cause and effect as so many of the Neo-Mal- 
thusians assume. While large families may not be so adequately 
supported on a small income as small ones, the association of high 
birth rates and high infant death rates is to a large extent due to 
the fact that both have a common cause in the lack of knowledge 
or prudence in the parents. In families in which the number of 
births is voluntarily limited, the death of a child is apt to be 
followed by the birth of another to replace the loss, as is very 
commonly the case in France. But even where there is no at- 
tempt to regulate the propagation of the race there are certain 
physiological factors which tend to bring about a correlation 
between high infant mortality and a high birth rate. It is a 
well-known fact that, while a child is nursing, the mother is much 
less apt to conceive. Even primitive peoples often take advan- 
tage of this fact and nurse their offspring for a long time in order 
to avoid having others. The death of an infant and the conse- 
quent interruption of lactation is commonly followed by another 
conception. The more rapidly infants die the more rapidly, 
therefore, new conceptions are apt to occur. 
The birth rate has fallen in several cities in Germany much 
faster than the infant mortality. In Munich, for instance, the 
birth rate fell from 1876-80 to 1906-09 over three times as much 
as the infant mortality, and in 349 German cities of over 15,000 
inhabitants the birth rate fell from 1901 to 1909 over three times 
as much as the infant death rate. Mombert has pointed out that 
in many cities and districts (Frankfurt, Stettin, Cologne, etc.) 
in Germany the infant death rate has risen while the birth rate 
has decreased, and in a few cities the birth rate has increased 
while the infant death rate has decreased. 
France shows an unfortunate condition in having a low birth 
rate and a high infant death rate. 
The classes in which the birth rate has fallen most are those in 
which the habit of nursing offspring has most fallen into disuse. 
The interruption of lactation would naturally tend to increase 
fecundity, but it has not done this, largely, no doubt, because it 
