412 THE BACTERIOPHAGE AND ITS BEHAVIOR 



(B) A mixture is made of equal parts of leucocjiie suspension, cul- 

 ture of the bacterium of barbone, and a fresh (four days old) suspension 

 of the Barbone-bacteriophage. During incubation at 38°C. drops 

 taken for examination show: 



Immediately, in 100 leucocytes there are 30 bacteria. 



After two and one-half minutes in 100 leucocytes there are 139 

 bacteria. 



After five minutes, in 100 leucocytes there are 201 bacteria. 



After seven and one-half minutes, in 100 leucocytes there are 271 

 bacteria. 



After ten minutes, in 100 leucocytes there are 269 bacteria. 



In the control mixture, made with bouillon, no bacteria were phago- 

 cytized. 



Here it is impossible to calculate the opsonic indices, since no phago- 

 cytosis occurred in the control mixture. The indices are infinity. 



As was the case with the dysentery bacillus, the bacterium of barbone 

 which resists the action of the bacteriophage is also resistant to phago- 

 cytosis. 



Prepare a mixture of one-third leucocytic suspension, one-third of 

 the same suspension of Barbone-bacteriophage as that used in the pre- 

 ceding experiment, and one-third of a suspension of the bacterium of 

 barbone resistant to dissolution. After fifteen minutes at 37° C. 100 

 leucocytes have ingested 3 bacteria, that is to say, 90 times less than 

 with normal bacteria. 



The race of Shiga-bacteriophage employed in the experiments 

 previously described manifests a definite, although feeble, virulence 

 for B. hjphosus. The following experiments show that it also exerts 

 a definite opsonic action on this bacillus, 



1. Mix equal parts of bouillon, leucocyte suspension, and B. typhosus 

 suspension. 



After fifteen minutes at 38°C. 100 leucocytes have phagocytized 68 

 bacilli. The opsonic index is 1. 



2. Mix equal parts of Shiga-bacteriophage suspension, leucocyte 

 suspension, and typhoid suspension. 



After fifteen minutes 100 leucocytes have ingested 203 bacilli. Op- 

 sonic index = 3. 



3. Mix equal parts of leucocyte suspension, typhoid suspension and 

 the solution of the alcoholic precipitate (the same one as that employed 

 in the experiments with the dysentery bacillus). 



