of physique demanded was extremely low, while Major-General Sir F. Maurice has stated50 that, even when all these rejections have been made, of those who actually are enlisted, at the end of two years only two effective soldiers are found for every five who enlist. It is not difficult to see a bearing of these facts on the birth-rate. The civilized world is becoming a world of towns, and, while the diminished birth-rate of towns is certainly not mainly the result of impaired vitality, these phenomena are correlative facts of the first importance for every country which is using up its rural population and becoming a land of cities.
From our present point of view it is thus a very significant fact that the equipoise between country-dwellers and town-dwellers has been lost, that the towns are gaining at the expense of the country whose surplus population they absorb and destroy. The town population is not only disinclined to propagate; it is probably in some measure unfit to propagate.
At the same time, we must not too strongly emphasize this aspect of the matter; such over-emphasis of a single aspect of highly complex phenomena constantly distorts our vision of great social processes. We have already seen that it is inaccurate to assert any connection between a high birth-rate and a high degree of national prosperity, except in so far as at special periods in the history of a country a sudden wave of prosperity may temporarily remove the restraints on natural fertility. Prosperity is only one of the causes that tend to remove the restraint on the birth-rate; and it is a cause that is never permanently effective.