Modesty (whether or not of the merely superficial and exterior kind) is more developed among urban populations.

In speaking of sexual things in the towns people veil their thought more; even the lower class in towns employ more restraint, more euphemisms, than peasants.

Thus in the towns a child may easily fail to comprehend when risky subjects are talked of in his presence.

It may be said that the corruption of towns, though more concealed, is all the deeper.
Maybe, but that concealment preserves children from it.

The town child sees prostitutes in the street every day without distinguishing them from other people.