The Initial Body and the Plaque Form in the Chlamydozoaceae.

Examination with the light microscope and any of several differential stains has failed to resolve the exact significance of the so-called initial bodies and plaque forms which, together with the elementary bodies, represent stages in the developmental cycles of the Chlamydozoaceae (lymphogranuloma-psittacosis group of agents; Rake, 1947). Previous studies from this laboratory (Rake and Jones, 1942) suggested that the initial bodies, particularly of the agent of lymphogranuloma venereum, are in fact larger single forms of the agent and that they divide as such in the early stages of the developmental cycle, but it was not clear whether the whole unit is larger or whether one is dealing with a single elementary body enveloped in a wide mantle of "capsular" substance. It seemed clear from differential staining with Noble's stain that the later plaque forms represent, rather than single forms, colonies of elementary bodies embedded in a "capsular" matrix. The elementary bodies themselves stain red, while the "capsular" material is green.