[Koch's postulates and virology].

It is shown, that the postulates of R. Koch are mainly devoted to the explanation of all symptoms of infectious diseases as a direct or indirect consequence of the action of the infectious agents. By this, Koch has directed the further work to the elucidation of the conditions for the occurrence of infectious processes, of the host-parasite relations and of the mechanisms of pathogenesis. Up to now the development of virology was substantially influenced by the realization of these principles which will also in future help to elucidate the remaining unsolved etiological problems of virology.