HE United States has been the world's most gigantic laboratory to | test the hypothesis that, given the appropriate conditions, people of s different races, cultures, national origins, languages and religions can live together in relative peace and freedom. The historical conditions of the experiment have varied from time to time and on a number of crucial occasions it has been seriously interrupted. Though the outcome of America's historic experience has sometimes been in doubt, the end-product a dynamic, powerful, national society striving to live by the democratic creed lends plausibility to the proposition that group differences are not necessarily an insuperable obstacle to a high degree of social integration. In view of the importance of racial and cultural relations in American history it is not surprising that the attempt to understand these phenomena should attract widespread popular and scientific interest. This curiosity, ranging from the fascination which the subject had for educated laymen and politicians to the persistent challenge it provided to social scientists, is reflected in a vast and still rapidly growing literature. It is of some interest in this connection to note that the first books published in the United States to bear the title sociology were pro-slavery treatises on Negro-White relations. In a country which finally had to resort to a bloody civil war to maintain its national integrity in the face of the issue of Negro slavery and which in the course of the nineteenth century drew upon all the peoples and regions of the world to recruit thirty million immigrants, it was to be expected that practical questions of racial and cultural relations would also furnish the subject matter