BACTERIOPHAGOUS ULTRAMICROBE 125 



OPSONIC POWER OF THE LYSINS 



In the following experiments the opsonic power has been de- 

 termined by the method of Wright and Douglas, making a mix- 

 ture of one part of the fluid of which the opsonic action is to be 

 measured, one part of a suspension of leucocytes, and one part 

 of a suspension of the bacteria against which the opsonic effect 

 is to be determined. The mixture is aspirated in a capillary 

 pipette which is sealed and placed in the water-bath at 38°C. for 

 fifteen minutes. The contents of the pipette are then spread on 

 a slide, stained, and examined. 



As reagents we have taken: Guinea pig leucocytes, a culture 

 of an anti-Shiga bacteriophage, and a suspension of Shiga bacilli. 



Experiment XXXIV 



1. Control. 



Leucocytes, bacilli, ordinary bouillon 

 100 leucocytes phagocytize 36 bacilli 



Opsonic index = 1 



2. Leucocytes, bacilFi, culture of bacteriophage two years old 

 100 leucocytes phagocytize 692 bacilli 



Opsonic index = 19.2 



3. The same mixture, except the bacteriophage culture is diluted 1 :250 

 100 leucocytes phagocytize 156 bacilli 



Opsonic index = 4.3 



4. Leucocytes, bacilli, culture of bacteriophage six days old 

 100 leucocytes phagocytize 1510 bacilli 



Opsonic index = 41.9 



5. The same mixture, except the bacteriophage culture is diluted 1 :250 

 100 leucocytes phagocytize 146 bacilli 



Opsonic index = 4.1 



6. The same mixture, except the bacteriophage culture is heated at 



60 Q C. for 30 minutes 

 100 leucocytes phagocytize 728 bacilli 



Opsonic index = 20.2 



7. The same mixture, except the bacteriophage culture is heated and 



diluted to 1:250 

 100 leucocytes phagocytize 101 bacilli 



Opsonic index = 2.7 



In the mixtures 2, 4, and 6, the indices recorded represent a 

 minimum . Many leucocytes contain such a number of phagocy tized bacilli 

 that counting is impossible. Since in the above counts only those cells 



