Modern civilization and modern science are in constant interplay and the relation of the state to medicine is simply one aspect of a much broader relationship—the changing sphere of government in the lives of the people. Industrialism has meant a large increase in population and the concentration of this population in huge cities. Factories and machine processes play a dominant role. Education has become almost universal. Research, inventions, still more research, and new applications of this research change industrial technology overnight. And the habits of living of the people through the development of apartment houses, radio, automobiles, aeroplanes, are also revolutionized. The pace quickens.The myriad problems of post-War international relations and national security, of currency and tariffs, of economic adversity and unemployment, the mounting public debt—all have thrust upon national and local governments a huge weight of responsibility. The depression has forced governments to assume control of basic economic activities, and, according to present indications, the trend will continue in the direction of more rather than less state activity.Governments have shown an increasing tendency to assume responsibility for the individual's general welfare. Modern industrialism and modern science have produced insecurity for a large section of the population—an uncertainty of life and limb and of employment, a risk of poverty in old age—that labour legislation and social insurance attempt to meet. Almost every type of social legislation has a direct or indirect effect upon the public health. Factory Inspection Acts, minimum wage legislation, control of the hours of work, housing schemes, health insurance, and workmen's compensation laws, illustrate the range of state activity in the field of public health. Legislation affecting medical care and public health agencies is simply a part of a much larger whole—the vast system of state activities and laws which has for its objective the greatest welfare of the people.