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of generations would occupy every habitable space. But, as 
a fact, the number of inhabitants of most countries is very 
stationary; what, then, are the causes which so exactly 
neutralize the tendency to increase 1 ? 
These are best learnt by exhaustively working out the 
history of 20 or 30 families, finding out how many of their 
members married, and at what ages, what was their issue, 
how many of the children died, owing to what causes, and so 
forth, as stated more fully below. Such an inquiry will 
necessarily lead to a far more accurate knowledge of the social 
condition of the people than could otherwise be obtained, and 
is sure to yield indirectly, as well as directly, a valuable 
harvest of results. 
1. Conditions of Marriage. —At what ages do they marry? 
how many do not marry at all ? What are the restrictions 
which hinder persons from marrying as soon as they are 
inclined ? how as regards the frequency of polygamy or 
polyandry and the number of wives, &c. ? What is the pro¬ 
portion of male and female adults ? 
2. — Separation of husband and wife. —Customs dependent 
on the institution of polygamy ; other circumstances which 
separate them periodically, or for long periods. 
3. Influences restrictive of fertility. —How long does the 
mother suckle her child ? At what ages does she begin and 
end child-bearing ? Is any diet adopted by women or other 
practice followed, as a check on fertility ? What is the pro¬ 
portion of children to a marriage ? What is the frequency 
of sterile women ? Are drugs, or physical means, used to 
induce abortion ? Is any operation performed on either men 
or women to induce sterility ? 
4. Loss of infant life. —Still-births, infanticide, and of what 
sex ? Death of child due to severe exertion of mother too 
soon after childbirth ? Do more children die at one time of 
the year than another '? and of what do they die—epidemics, 
other diseases, want, accidents, war? What is the mortality 
at different ages, as shown by the sizes of families whose 
parents are of different ages ? What is the proportion of 
aged men to aged women ? 
