ABSTRACT
Previous chapters dealt with discoveries related to bacteria. We now come to discoveries about viruses where accident and happenstance have played even greater roles. This is not surprising when you realize that viruses are so infinitesimally small that a hundred million polio viruses, for example, could fit on the period at the end of this sentence. They cannot be seen with conventional microscopes, they cannot be grown in the laboratory by customary means, their components tend to vary, their effects and behavior change with different hosts, and they can even infect bacteria.
