We may fairly claim that general and special hospitals have been important agents, not only in reducing the fatality of disease, and in restoring to efficiency more rapidly than in the past a large proportion of the total population; but also in reducing the incidence of tuberculosis, of syphilis, and of other diseases. The public indebtedness to hospitals has another aspect, too often overlooked. The aggregation during the last hundred years of a steadily increasing proportion of our population in crowded towns has meant the introduction on a gigantic scale of elements inimical to health. Smoke and obscuration of sunlight, dust and noise, the substitution of indoor for outdoor occupations, the difficulties of milk supply for children, and above all inferior housing with associated increased facilities for infection, have combined to render healthy life in towns difficult of attainment. Nor must we omit from the adverse side of the balance sheet the greater loneliness of family life in towns, the diminution in neighbourliness, and the failure of public social opinion to produce the wholesome effect on conduct which it exercises in village life. And yet, notwithstanding these factors, urban death-rates and especially tuberculosis death-rates have declined more than rural death-rates, and in parts of some countries urban is even lower than rural mortality. Why is this? Our hospitals provide the key to the mystery. Parturition is freer from risk in town than in remote country districts; the means for the prevention of infection are better organized, and accident and disease are more promptly and more efficiently treated. The poor in towns receive as a matter of course in hospitals better treatment gratuitously than king or president could command thirty years ago. The relief to housing deficiency given by hospitals comes when most needed, in the emergencies of child-bearing and of sickness; and the net result of this and of better sanitary supervision is that although room-accommodation for families is much more restricted in towns than in country districts, the town-dwellers have a large share of their urban handicap removed by their superiority over country people in medical treatment. _The Continuing Mass of Preventible Disease_ The medical record of the past on the side of preventive medicine is one of increasing control over infectious diseases. In securing this result epidemiologists, pathologists, and vital statisticians can rightly claim first place, aided by the sanitary and industrial inspector and the sanitary engineer; the epidemiologist being dependent largely on the work of the pathologist and of the statistician for guidance in his field investigations, which have led to the discovery and removal of numerous sources and channels of infection.