Evidence is wanting, however, to show that there is a decrease in the
sexual power of any nation.

France might be flattered to be told that her low birth-rate is due to
the high intellectual attainments of her people, and that the rapidly
decreasing birth-rate is due to a rapid increase of her intellectual
power during recent years.

Ireland and New Zealand would be equally pleased could they believe that
their low, and still decreasing birth-rate is due to the lessening of
the sexual instinct, attendant upon, and resulting from a high and
increasing intellectual power and activity.

The fact is, that the sexual instinct is so immeasurably in excess of
the maximum power of procreation in the female, that an enormous
reduction in sexual power would require to take place before it would
have any effect on the number of children born.

The number of children born is controlled by the capacity of the human
female to bear children, and one birth in every two years during the
child-bearing period of life is about the maximum capacity.

A moderate diminution in the force of the sexual instinct might lead to
a decrease in the marriage rate, but it would require a very serious
diminution bordering on total extinction of the instinct to exert any
serious effect on the fecundity of marriage.

All that can be claimed for this theory of population is, that,
reasoning from known physiological analogies, we might expect a
weakening of the desire for marriage, coincident with the general