It is thus that civilization, at a certain point in its course, renders inevitable the appearance of that wider and deeper organization of life which in the present volume we are concerned with under the name of Social Hygiene. That movement is far from being an abrupt or revolutionary manifestation in the ordinary progress of social growth. As we have seen, social reform during the past eighty years may be said to have proceeded in four successive stages, each of which has involved a nearer approach to the sources of life. The fourth stage, which in its beginnings dates only from the last years of the nineteenth century, takes us to the period before birth, and is concerned with the care of the child in the mother's womb. The next stage cannot fail to take us to the very source of life itself, lifting us beyond the task of purifying the conditions, and laying on us the further task of regulating the quantity and raising the quality of life at its very source. The duty of purifying, ordering, and consolidating the banks of the stream must still remain.[8] But when we are able to control the stream at its source we are able to some extent to prevent the contamination of that stream by filth, and ensure that its muddy floods shall not sweep away the results of our laborious work on the banks. Our sense of social responsibility is developing into a sense of racial responsibility, and that development is expressed in the nature of the tasks of Social Hygiene which now lie before us.