The failure of physicians to "socialize" or "humanize" their knowledge is due to two causes: (1) no one has been applying _result tests_ to the profession as a whole and to the state in its capacity as doctor, testing carefully the sickness rate, the death rate, and the expense rate of preventable diseases; (2) physicians themselves have not needed to know, either at college or in practice, the tax levied upon their communities by preventable sickness. Public schools can do much to secure result tests for individual physicians, for the profession as a whole, and for boards of health. Schooling in preventive medicine, or, better named, schooling in preventive hygiene, will fit physicians to do their part in eradicating preventable disease. Preventive hygiene is not an essential part of the training of American physicians or nurses to-day. Not only are there no colleges of preventive hygiene, but medical schools have not provided individual courses. It is possible for a man to graduate with honors from our leading medical colleges without knowing what "vital statistics" means. Even boards of health, their duties and their educational opportunities, are not understood by graduates; it is an accident if the "social and economic aspects of medical practice," "statistical fallacies," "hospital administration," "infant mortality," are familiar terms. It is for this reason, rather than because physicians are selfish, that indispensable and beneficent legislation is so generally opposed by them when the prerogatives of their profession seem in danger. Practically every important sanitary advance of the past century has been fought at the outset by those whose life work should have made them see the need. Physicians bitterly attacked compulsory vaccination, medical inspection of schools, compulsory notification of communicable diseases. What is perhaps more significant of the physician's indifference to preventive hygiene is the fact that most of the sanitary movements that have revolutionized hygienic conditions in America owe their inception and their success to laymen, for example, tenement-house reform, anti-child labor and anti-tuberculosis crusades, welfare work in factories, campaigns for safety appliances, movement for a national board of health, prison, almshouse, and insane-asylum reform, schools for mothers, and milk committees. The first hospital for infectious diseases, the first board of health, the first out-of-door sea-air treatment of bone tuberculosis in the United States, were the result of lay initiative. Dr. Hermann M. Biggs says that in America the greatest need of the medical profession and of health administration is training that will enable physicians and lay inspectors to use their knowledge of preventive hygiene for the removal of living and working conditions that cause preventable sickness. A physician without knowledge of preventive hygiene is simply doing a "general repair" business.