These structures are responsible for two major processes, the immunological reaction of the organism on virus inoculation, and the penetration of the virus into the cell. Effective protection against virus infection has until now been immunological. But not all virus infections are subject to immune reactions. In this connexion the question arises as to what determines the nature of the organism's immunological reaction on virus inoculation. Why do we observe stable immunity after such virus infections as measles, smallpox, mumps and others, and not after influenza? The solution of this problem will involve the investigation of:(a) the chemical composition and properties of the surface structures and, primarily, of the antigenic determinants of the virus's immunological specificity;(b) the sources of genetic information employed during the synthesis of virus membrane components;(c) the sub-cellular structures which implement the synthesis of virus membrane components. The importance of the study of the chemical structure of the antigenic determinants arises from their possible identity with blood antigenic determinants. But the organism does not form antibodies against its own blood