128 THE BACTERIOPHAGE AND ITS BEHAVIOR 



Another experiment, performed with the staphylococcus, may be 

 cited since it substantiates further this conclusion. A flask containing 

 250 cc. of bouillon (pH 7.8) is seeded with a strain of Staphylococcus 

 aureus. After incubation for 15 days at 27°C. the culture is filtered 

 through a Chamberland candle. Two series of tubes are then prepared 

 as follows: 



Series I 



Tube 1. 10 cc. of fresh bouillon 



Tube 2. 7.5 cc. of fresh bouillon + 2.5 cc. of the filtrate 

 Tube 3. 5 cc. of fresh bouillon + 5 cc. of the filtrate 

 Tube 4. 2.5 cc. of fresh bouillon + 7 .5 cc. of the filtrate 

 Tube 5. 10 cc. of the filtrate, undiluted with bouillon 

 To this series of tubes a suspension of the staphylococcus is added, 



the strain being the same as that used for the preparation of the filtrate. 



After 24 hours all of the tubes are turbid, but the turbidity in tube 5 



is about half as great as that in tube 1. After 48 hours all tubes show 



the same degree of turbidity.* 



Series II 



The initial mixtures of fresh bouillon and of filtrate are the same as 

 those in series I. To the 5 tubes a suspension of the staphylococcus 

 is added to provide approximately 125 million organisms per cubic 

 centimeter. All of the tubes are then inoculated with 0.001 cc. of 

 Staphylo-bacteriophage. After 24 hours, the dissolution is complete 

 in tubes 1 and 2, partial in the other three. After 48 hours it is com- 

 plete in all. The number of corpuscles, per cubic centimeter at this 

 time is: 



Tube 1. 52,000 million 



Tube 2. 46,000 milHon 



Tube 3. 38,000 miUion 



Tube 4. 44,000 million 



Tube 5. 50,000 mUlion 

 I have not been able to determine the cause of these differences, but 

 in spite of this variation it is possible to conclude that the products 

 resulting from the distinctive activity of the bacterium itself have no 

 effect upon the phenomenon of bacteriophagy, nor upon the multipli- 

 cation of the bacteriophage corpuscles. 



* According to this experiment the staphylococcus, at least the strain under 

 examination, has but little "vaccinatinj!;" activity. 



