67 



REMARKS ON FILTRATION EXPERIMENTS WITH YELLOW-PEVER BLOOD. 



We have been careful to give with some minuteness all the details 

 of the manner in which the blood was filtered in these experiments. 

 We know that the filtration of micro-organisms or other small parti- 

 cles through porcelain or diatomaceous earth, is influenced very much 

 by the length of time the filtration is continued, the pressure used, by 

 the character of the fluid in which the particles are suspended, the 

 temperature, and other factors which are perhaps less known. 



Our review of the literature on the filtration of blood and body 

 juices containing the infectious material of diseases, the causes of 

 which are unknown and which are believed to be ultra microscopic, 

 disclosed reports of successful and unsuccessful filtration with such 

 meager details that it is difficult to draw proper conclusions. Those 

 factors which control the power of a given filter to allow an organism 

 to pass or to hold it back also account for the different results which 

 various experimenters have obtained in certain cases. 



For instance, we succeeded in passing diluted yellow-fever serum 

 through the closest-grained Pasteur-Chamberland B filter that we 

 could obtain, whereas the French commission — Marcboux, Salimbeni, 

 and Simond — working at Eio de Janeiro, failed to pass the infective 

 agent of yellow fever through a Chamberland B filter, though they 

 found that it did pass through the Chamberland F filter,. As the 

 French commission used undiluted blood and we used diluted serum, 

 the apparent discrepancy in results is accounted for ; for it is a well- 

 known fact that particles suspended in an albuminous medium filter 

 with more difficulty than particles suspended in water, alcohol, or 

 other limpid menstra of this character. 



Nocard, Eoux, and Dujardin-Beaumetz, in 1899, endeavored to 

 repeat Loffler's experiment with aphthous fever. They first failed to 

 pass the infective agent contained in the lymph of this disease through 

 a Berkefeld filter because they used an albuminous fluid, viz, " Mar- 

 tin's serum-bouillon," in order to dilute the lymph with a nutrient 

 medium, thus hoping to obtain cultures without the danger of con- 

 tamination in the filtrate. They found, however, that the albuminous 

 matter contained in the diluting fluid clogged the pores of the filter, 

 so that the filtrate was not virulent. 



They repeated the experiment, using water to dilute the lymph in 

 the proportion of 1 to 50, when they found the organisms causing 

 aphthous fever readily passed through a Berkefeld filter, and gave the 

 disease.by intravenous injection to young and old cattle. 



It is also a well-known fact that filters which successfully hold 

 back certain bacteria will permit them to pass if the filtration is con- 

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