The relation of pathogenic viruses to the cells of their hosts

Abstract

It is now generally assumed by the majority of workers in the field of virus diseases that the term “ virus ” should be limited to those small organisms, either approaching or below the limit of ordinary microscopic visibility, which are incapable of multiplication in vitro except in the presence of living animal or vegetable cells. This limitation is obviously only provisional, as with a fuller knowledge of the conditions obtaining in the living cell it may at some time become possible to simulate these sufficiently closely to allow of the growth of the virus in a cell-free medium. Until this is accomplished, however, the presence of the living cell must be regarded as essential, and we are faced with the problem of elucidating its role in the multiplication of the virus.