Smithsonian Report. 1942. — Stanley 



1. Mixture of Tobacco Mosaic virus With normal Rabbit Serum, 



The contaminating bacterium serves to give a good idea of the relative size of the molecules of virus. Elec- 

 tron micrograph with magnification X ca. 2.'i,000. (From Jaurnal of Biological Chemistry.) 



2 Tobacco Virus With Antitobacco Virus rabbit serum 

 An electron micrograph with magnification X ca. :<(l,0(IO. (From Journal of Biological Chemistry.) 



