Mention the contributions of various scientists regarding viruses.

(N/A) $\rightarrow$ $D. J. Ivanowsky (1892)$ recognized certain microbes as the causal organisms of the mosaic disease of tobacco.
$\rightarrow$ These were found to be smaller than bacteria because they passed through bacteria-proof filters.
$\rightarrow$ $M. W. Beijerinck (1898)$ demonstrated that the extract of infected tobacco plants could cause infection in healthy plants and called the fluid $Contagium$ $\text{vivum}$ $\text{fluidum}$ (infectious living fluid).
$\rightarrow$ $W. M. Stanley (1935)$ showed that viruses could be crystallized and crystals consist largely of proteins.