The infectious fevers have, during the last fifty years, been the subject of much epidemiological research, and have thus been made to yield up secrets which have materially affected the whole outlook of preventive medicine. But there yet remains for exploration a vast adjacent territory, that of minor coccal infections of the skin. However, whereas the former, being clearly defined clinically and in many cases subject to compulsory notification, lend themselves well to investigations of this sort, Impetigo, as a type of minor coccal dermatitis, surrounds itself with dificulties. For not only does it vary very much in its appearances by the time it is first seen but it is often of so little severity that it does not come under the observation of a physician at all, so that the influence of missed cases, always an important factor to be reckoned with in the study of epidemics, may assume such proportions as to give quite an erroneous impression of the total incidence of the disease. Consequently the epidemic aspects of impetigo have as yet received very little attention.