But as the brain and its faculties develop, powerfully aided indeed by the very difficulties of the sexual life, the impulse for sexual union has to traverse ever longer, slower, more painful paths, before it reaches--and sometimes it never reaches--its ultimate object.

This means that sex gradually becomes intertwined with all the highest and subtlest human emotions and activities, with the refinements of social intercourse, with high adventure in every sphere, with art, with religion.

The primitive animal instinct, having the sole end of procreation, becomes on its way to that end the inspiring stimulus to all those psychic energies which in civilisation we count most precious.

This function is thus, we see, a by-product.

But, as we know, even in our human factories, the by-product is sometimes more valuable than the product.