The lactose-fermenting coliform organisms in milk and dung have been investigated.A large proportion of those recovered from raw milk by direct plating proved to be of theBact. aerogenestype and a number of “intermediates” was also present.In dung faecalBact. colilargely predominated, the proportion ofBact. aerogenesbeing very small.If the implication of these experiments be accepted it is possible that many of the coliform types found in milk are derived, not from faeces, in which the proportion ofaerogenesis small, but from external sources, such as contaminated utensils, and from food-stuffs.