Not the least important among the problems the citizens of San Francisco are facing is the prevention of infectious disease. In catastrophes such as the one which has overtaken the great city of the Pacific coast, two factors are especially active in increasing the prevalence of diseases of germ origin. These are: First, the close physical association, even involving personal contact, into which a very large proportion of the population are forced, and, second, the diminished powers of resistance due to hunger, thirst, exposure, fatigue, and all the other accompaniments of the situation. The men, women and children exposed to infection become, so to speak, more inflammable at the same time that the opportunities for exposure are enormously multiplied. It needs no ghost to come from the grave to tell us of the danger. A difficult task lies before those on whom falls the responsibility for maintaining the public health