 In 1898, the Dutch microbiologist Martinus Beijerinck (1851–1931), a microbiology teacher at the Agricultural School in Wageningen repeated experiments by Adolf Mayer and became convinced that filtrate contained a new form of infectious agent.He observed that the agent multiplied only in cells that were dividing and he called it a "contagium vivum fluidum" (soluble living germ) and re-introduced the word "virus".Beijerinck maintained that viruses were liquid in nature, a theory later discredited by the American biochemist and virologist Wendell Meredith Stanley (1904–1971), who proved that they were in fact, particles.