The first direct steps towards the reduction of infant mortality were directed against epidemic or summer diarrhœa. Medical officers of health have always been required in their annual reports to summarize the vital statistics in their districts; and since 1905 a more detailed statement of infant mortality during each part of infancy has been required. Annually, therefore, as well as when they received the weekly returns of deaths from the local registrars, there was forced upon their attention the fact that deaths of infants under one year of age formed a high proportion of total deaths at all ages (12.9 per cent. in 1917), and that of these infantile deaths a large proportion were caused by diarrhœa, the number varying with the temperature and the deficiency of rainfall in the summer months. In 1912, a year of relatively small mortality from diarrhœa, this disease caused 8.1 per cent. of all deaths under one year of age. For many years past it has been customary for medical officers of health to issue warnings as to summer diarrhœa, to arrange for the distribution of leaflets of advice concerning the disease, and to urge the necessity of more thorough cleanliness both municipal and domestic during the summer months. Even before the early notification of births became obligatory, in many areas the addresses of infants were obtained from the registrars of births and special visits were made to the mothers of infants during the months of June and July and especially to the mothers of those infants who were known to be artificially fed. The reports of medical officers of health of many of the large towns from 1890 onwards show that much valuable work was being accomplished, and the way was being prepared for more general measures against infant mortality. The importance of municipal sanitation in aiding the elimination of diarrhœal mortality is illustrated in the experience of many towns, and strikingly by the comparative experience of Leicester and Nottingham. The chief difference between the sanitary condition of the two towns was that in Nottingham in 1909 pail closets still served more than half the houses, while Leicester had abandoned this system entirely, substituting water-closets. Between 1889-93 and 1909 the diarrhœal mortality in Leicester had declined 52 per cent.; in Nottingham it had only declined 4 per cent.