Martinus Beijerinck

Martinus Beijerinck was a Dutch microbiologist and botanist who, repeating Dmitri Ivanovsky's tobacco mosaic filtration experiment independently in 1898, concluded that the filterable agent was not a bacterial toxin but a new, self-replicating class of infectious matter, which he named a virus. He spent most of his career at the agricultural school in Delft, later the Technical University of Delft, working on microbiology of soil and fermentation as well as plant disease. Beijerinck's insight that the agent could reproduce only inside a living host, rather than existing as free-living matter, set the conceptual foundation the field of virology built on for the next several decades, though the physical, particulate nature of a virus was not confirmed until X-ray crystallography imaged one in 1941, a decade after his death.