Nowhere has this been so thoroughly studied and so clearly proved as in the United States.

It is only necessary to mention Dr.C.B.Davenport of the Department of Experimental Evolution at Cold Spring Harbor (New York) who has carried on so much research in regard to the heredity of epilepsy and other inheritable abnormal conditions, and Dr.Goddard of Vineland (New Jersey) whose work has illustrated so fully the hereditary relationships of feeble-mindedness.
The United States, moreover, has seen the development of the system of social field-work which has rendered possible a more complete knowledge of family heredity than has ever before been possible on a large scale.
It is along such lines as these that our knowledge of the eugenic conditions of life will grow adequate and precise enough to form an effective guide to social conduct.

Nature, and a due attention to laws of heredity in life, will then rank in equal honour to our eyes with nurture or that attention to the environmental conditions of life which we already regard as so important.

A regard to nurture has led us to spend the greatest care on the preservation not only of the fit but the unfit, while meantime it has wisely suggested to us the desirability of segregating or even of sterilising the unfit.

But the study of Nature leads us further and, as Galton said, "Eugenics rests on bringing no more individuals into the world than can be properly cared for, and these only of the best stocks." That is to say that the only instrument by which eugenics can be made practically effective in the modern world is birth-control.
It is not scientific research alone, nor even the wide popular diffusion of knowledge, that will suffice to bring eugenics and birth-control, singly or in their due combination, into the course of our daily lives.
They need to be embodied in our instinctive impulses.