Filterable Viruses a Critical Review

In all fields of work, times come when one must stop and take thought. New facts, new ideas, and new suggestions alter lines of endeavor in every field of research. We are here today for the purpose of taking thought concerning the knowledge of the so-called filterable viruses and the diseases caused by them. I have been asked to give a critique of this knowledge. It is quite obvious that I shall be unable within an hour to analyze thor-oughly and to criticize authoritatively all the work in this field. Therefore, I shall review quickly some facts and ideas concerning this group of diseases as a whole and then discuss a few reports concerning several of its individual members. In table 1 are listed most of the diseases which are included by different observers in the group under discussion. The etiological agents concerned in these diseases, or groups of them, have been given a variety of names, e.g., filterable viruses, invisible microbes, ultra-microscopic viruses, inframicrobes, protista, microplasms, chlamydozoa, and strongyloplasms. A superficial examination alone is convincing that none of these names is applicable to all of the etiological agents. Names, however, facilitate the inter-change of facts and ideas between individuals. For practical purposes, then, the term filterable viruses, mainly because of its wide usage, is as satisfactory as any name suggested. Throughout this discussion the term filterable viruses will be employed in a noncommittal way to designate certain active