"When Dr. W.M. Stanley of the Rockefeller Institute's Princeton station crystallized the virus which produces the mosaic disease of tobacco, there was a great hullabaloo among the biologists. And rightly so. Were these crystal alive? Apparently no more so than diamonds, glass, sand or other crystals with which we are familiar. Yet when virus crystals were put on a tobacco leaf, the mosaic disease spread like a slow fire over a whole field just as if it had been infected by living bacteria."