Diagram of community studied. The community is outlined by the broken line and the lower and right-hand margins of the figure; the area is roughly 1000 × 600 ft. The black blocks represent houses in which paralytic poliomyelitis occurred; the shaded blocks represent houses in which abortive poliomyelitis occurred. The residence of individuals with positive stools is indicated by a cross. Figure and legend reprinted from ref. 35.