FILTERABLE VIRUSES 435 



from the infecting material while that of others will pass 

 through them.* 



Contagious pleuro-pneumonia. The virus of contagious 

 pie uro- pneumonia in cattle does not pass through the Cham- 

 ber land filter B. Nocard and Roux 2 inoculated collodion cap- 

 sules containing bouillon with the "lymph" exudate of con- 

 tagious bovine pleuro-pneumonia, sealed and placed them in 

 the abdominal cavity of rabbits. In from 15 to 20 days the 

 liquid became cloudy and with a magnification of 2000 diam- 

 eters and a brilliant illumination, they detected minute bodies 

 in the liquid. With this culture they produced the same dis- 

 ease in cattle that follows the inoculation of the exudate. No- 

 card 3 found that the pulmonary exudate was rendered harm- 

 less by passing it undiluted through a Berkefeld or a Chamber- 

 land filter, but when diluted from 60 to 80 times its volume 

 with water or bouillon and passed through a Berkefeld or 

 Chamberland F. filter it was infective. The closer grained 

 filters such as Kitasato's or Chamberland B. kept the virus 

 back. 



Foot and mouth disease. Loeffler and Frosch 4 found 

 that the virus of foot and mouth disease when diluted passed 

 through a Berkefeld filter that refused to pass Ps. fluorescence. 

 The Kitasato filter of finer pores kept back the virus. This was 

 the first among the diseases* of animals to have its virus demon- 



* In filtering the substance containing the virus it is important 

 that the filter employed is perfect and is capable of keeping back 

 known bacteria. There is considerable difference in the density of 

 filters of the same make. Secondly, the conditions under which the 

 filtration takes place should be such that the virus can not grow 

 through the filter. 



2 Nocard and Roux. Ann de 1'Inst. Pasteur, Vol. XII (1898) p. 

 240. 



3 Nocard. Handbuch der pathogenen Mikroorganismen, Kolle and 

 Wassermann, Bd. Ill (1903) p. 704. 



4 Loeffler and Frosch. Centralbl. f. Bakt, Bd. XXIII (1898) p. 371. 



* The mosaic or spotted disease of the tobacco plant was the 

 first infectious disease to furnish experimental evidence that there 

 was a virus that would pass through such a filter. Iwanowski in 

 1892 determined that the filtered juice of this plant was infective. 

 In 1899 Beigerinck independently rediscovered the same fact. 



