IN a Chadwick public lecture, delivered on October 25, on the sanitation of rural areas in the tropics and sub-tropics with special reference to housing, Prof. D. B. Blacklock expressed the view that rural sanitation in tropical and sub-tropical dependencies and possessions is gravely neglected. He touched on the subject of hygienic conditions in rural West Africa, but attention was directed chiefly to the present state of rural India. The chief part of the lecture dealt with housing in the rural areas, and Prof. Blacklock emphasised by suitable illustrations how diseases of various kinds come to be associated with types of houses showing special defects. These defects are either of site, of structure and material, or due to the habits of the inmates. A house-relation of many diseases in tropical and sub-tropical countries is Directly traceable to an origin in such defects; the removal of the known defects would largely eliminate those house-diseases, which seriously affect millions of people. To-day we have at our disposal in the shape of broadcasting a valuable method of impart ing the principles of village hygiene even to those who can neither read nor write. In addition to such educative methods, it is the duty of any Government which wishes to attain success in raising the standard of rural sanitation to undertake a further measure. This is the building, using local materials so far as is possible, of standard houses and villages at many accessible places in each province or even district as examples of hygienic construction. Demonstration villages kept up to the standard would exemplify to the villagers more vividly than other methods the dangerous defects of their own homes.