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April 24, 1948


Author Affiliations

Bethesda, Md.

From the National Institute of Health.

JAMA. 1948;136(17):1081-1083. doi:10.1001/jama.1948.02890340007003

Electron microscopes make it possible to see the elementary infectious particles of the smallest viruses and thus to study these hitherto invisible agents of disease in the same general way that bacteria have been studied with optical microscopes. In such a study the first problem that arises, and one that must be successfully met before others can properly be attacked, involves learning to recognize the individual units of virus activity among the masses of tissue and other extraneous material with which they are associated. For this a virus should be available in purified form; otherwise, it is as dangerous to ascribe virus activity to specific objects seen in the microscope as it is to pick some particular organism in a mixed bacterial culture as being responsible for a disease induced by the culture as a whole. Viruses grow only on living matter, and they must therefore usually be separated from