680 



DISEASES OF UNKNOWN ETIOLOGY 



FILTRABLE VIRUS 



Recent investigations into the causation of disease have revealed 

 that a considerable number of infections may be caused by organisms 

 too small to be held back by filters through which even the smallest 

 bacteria cannot pass. The earliest observations of such "filtrable 

 virus" are probably those of Frosch (1898) in foot-and-mouth disease 

 and of Beijerinck in the mosaic disease of tobacco. Since then similar 

 investigations have shown that a large number of diseases are probably 

 caused by such minute organisms; their investigation, long delayed 

 by the belief in their invisibility by even the most powerful microscopic 

 aid, and by our inabiUty to cultivate them, has taken new impetus 

 from the discovery of and the cultivation of minute globoid bodies from 

 the virus of poUomyelitis by Flexner and Noguchi (see below). The 

 following tabulation is based largely on the comprehensive summary 

 pubUshed by Wolbach.^ 



DISEASES CAUSED BY FILTRABLE VIRUS 



1 Wolbach, Jour, of Med. Res., xxvii, 1912. 



