Many observers of malaria entertain the opinion that the incidence of malaria in the United States is experiencing a declin which cannot be altogether attributed to conscious efforts a malaria control, since the phenomenon is noticed in all sections. While undoubtedly the resultant of several factors, observation made during the course of a malaria survey in Southeast Missouri in 1921 are strongly suggestive that one of these factors is the degree to which human habitations afford an obstacle to the unrestricted attack of their occupants by anophelines.
This survey covered a block of 141 square miles in which all conditions encountered in the general region were represented. There were 583 occupied rural dwellings in the area, of which 50 were visited and the occupants interrogated and a portion examined. Data were secured from a population of 2570.