STUDIES IN MICROBIC HEREDITY VIII. THE INFECTIVITY AND VIRULENCE OF A FILTRABLE PHASE IN THE LIFE HISTORY OF B. FUSIFORMIS AND RELATED ORGANISMS

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Abstract
Evidence is presented that B. fusiformis and related organisms often associated with it in infective processes have a filtrable or gonidial phase on which their virulence primarily depends[long dash]an infective granule, so to speak. This phase is usually not to be cultivated under the same conditions under which the parent form germinates. Some Of these forms are probably invisible. The conditions suitable for germination of this phase, particularly in vivo, may result in its cyclic evolution to a totally different stage (bacterial type) in the infectious complex. The various members of this complex, or part of them, may be avirulent in their adult phase, but quite virulent in the filtrable phase. Different orders of these gonidia seem to differ greatly in virulence. Some may be of lesser virulence than the parent form. The fact that common non-pathogenic organisms may have a virulent, filtrable, but uncultivable phase in their life history suggests a revaluation in present conceptions of viruses, so-called. It also suggests a revaluation of views as to what constitutes a secondary infection. The latter are obviously of 2 kinds (1) those genetically related to the infective or filtrable form and helping to make up the infective complex; (2) chance invaders having no genetic relation to any member of the complex. Such considerations have an obvious and important bearing on current views of epidemiology, infection and immunity.