56 



THE BACTERIOPHAGE AND ITS BEHAVIOR 



We may consider first the reaction as it develops in suspensions of 

 low bacterial content, for example, in a suspension containing 1 million 

 Shiga bacilli per cubic centimeter. Let us inoculate a series of tubes, 

 each containing 10 cc. of such a suspension, with decreasing quantities 

 of the Shiga-bacteriophage as indicated in table 4, The results, ex- 

 pressed by the macroscopic appearance of the tubes at different inter- 

 vals will be as indicated. 



The figures within the parentheses indicate the opacity of the cloud, 

 by comparison with control tubes containing titrated suspensions of 

 formolized Shiga bacilH. Further experiment showed that tube 11 did 

 not contain any of the bacteriophage principle. 



(?) = clouding doubtful; if any, very slight. 



Let us repeat this experiment, under the same conditions, except 

 that we will combine the same series of dilutions of the bacteriophage 

 filtrate with a suspension containing 100 million bacilli per cubic centi- 

 meter, that is to say, with a definitely cloudy suspension rather than 

 with one having but 1 million organisms per cubic centimeter. As 

 will be seen, the ultimate results are entirely comparable to those 

 obtained with the less concentrated bacterial suspension (table 5). 



The following experiment (table 6) shows that the general course 

 of the process of bacteriophagy is the same if it is performed with a 

 Staphylo-bacteriophage in decreasing amounts combined with a sus- 

 pension of the staphylococcus. Here, each tube contains 10 cc. of a 

 suspension of Staphylococcus aureus in a salt-peptone bouillon, adjusted 

 to pH 7.8. Incubation is at 32°C. 



