research for the detection of viruses, their identification, and the study of their bio-logical properties. For isolating viruses that come from man, animals, and plants, the material under investigation may be introduced into the organisms of experimental animals and plants that are sensitive to the viruses, or cell (tissue) cultures and organ cultures may be infected. The presence of the virus is proved by the characteristic affliction in the experimental animals (or plants); in tissue cultures it is proved by a lesion of the cells, the so-called cytopathologic action, which is recognized by microscopic or cytochemical investigation. The so-called plate method used in virologjcal research involves observing defects in the cellular layer caused by destruction or lesion of cells in foci of virus accumulation. Virions, which have a characteristic structure in different viruses, can be identified by electron microscopy. Further identification of viruses is based on the combined use of physical, chemical, and immunological methods. For ex-ample, viruses are distinguished by sensitivity to ether, which is related to the presence or absence of lipides in their shells. The type of nucleic acid of the virus (RNA or DNA) can be determined by chemical or cytochemical methods. Serological reactions with serum obtained by immunizing animals with the corresponding viruses are used to identify virus proteins. These reactions make it possible to recognize not only strains of viruses but also their varieties. Serological research methods based on the presence of antibodies in the blood permit the diagnosis of viral infections in man and higher animals and the study of the circulation of viruses among them. Special research methods are used to reveal latent (concealed) viruses in man, animals, plants, and bacteria.
REFERENCESShubladze, A. K., and S. la. Gaidamovich. Kratkii kurs prakticheskoi virusologii. Moscow, 1949.
Zhdanov, V. M., and S. la. Gaidamovich. Virusologiia. Moscow, 1966.
V. M. ZHDANOV