This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
In 1892, the Russian botanist Dmitri Ivanovsky filtered sap taken from tobacco plants infected with mosaic disease through a filter fine enough to remove ordinary bacteria, and found the filtered liquid was still infectious. Ivanovsky was cautious about what this meant, suggesting the agent might be a toxin produced by bacteria rather than a new kind of pathogen. Six years later, the Dutch microbiologist Martinus Beijerinck repeated the experiment independently and went further: he proposed that the infectious agent was a fundamentally new form of matter, which he called contagium vivum fluidum, a soluble living germ, distinct from any known bacterium. Historians of science still dispute how the discovery credit should be split between the two: Ivanovsky observed the phenomenon first, but Beijerinck correctly interpreted what it meant. The dispute is recorded on this atlas as a genuine open disagreement rather than settled in favor of either man, since neither reading of the record is without support.