BACTERIOPHAGOUS ANTISERUM 139 



Experiment LIII. Prepare a mixture of equal parts of antibacterio- 

 phage-Shiga serum and culture of anti-Shiga bacteriophage. Allow them 

 to remain in contact for five days. They are placed under conditions such 

 that if the serum exerted a destructive action on the ultramicrobes its 

 effect could not fail of manifestation . After these five days of contact, three 

 tubes, each containing 10 cc. of sterile bouillon, are seeded with a drop of 

 a bouillon culture of Shiga bacilli. To the first of these tubes add a drop of 

 the mixture of antiserum-bacteriophage; to the second add a drop from 

 this first tube after it has been shakesn ; and to the third add a drop from the 

 second. We have thejn a series of three tubes, planted with B. dysenteriae 

 Shiga, containing decreasing concentrations of the serum-bacteriophage 

 mixture. After twenty-four hours at 37°C. normal cultures of Shiga are 

 obtained in the three tubes, and plantings on agar likewise give normal 

 cultures. Up to this point it looks as though the lytic principle has been 

 destroyed. 



Continue the experiment. Replace the three tubes in the incubator and 

 twenty-four hours later it is seen that lysis has commenced in the first 

 tube of the series. Agar inoculation from this tube remains sterile. The 

 last two, on the contrary, still contain a normal culture of B. dysenteriae. 

 Return the tubes again to the incubator. After twenty-four hours, that 

 is, three days after the beginning of the experiment, lysis takes place in 

 the last two tubes. All subcultures on agar remain sterile. 



The bacteriophage is therefore not destroyed by the antibac- 

 teriophage serum; its power is simply inhibited for a time. 



The experiment further shows that the action is truly inhibi- 

 tive, acting upon the entire number of ultramicrobes. In other 

 words, the delayed lysis is not due to the revival of certain ultra- 

 microbes particularly resistant, since lysis is produced even in 

 the last tube which has received, as a result of successive dilu- 

 tion, an infinitesimal quantity of the germs. 



The presence of an antilysin in the antibacteriophage serum 

 allows us to obtain further information regarding the nature of 

 the virulence of the ultramicrobe. 



Experiment LIV. To a suspension of the bacterium of barbone add a 

 drop of a bacteriophage culture active against this organism and then 

 10 drops of an antibacteriophage-Shiga serum, that is, a quantity of serum 

 completely inhibitive of lysis in a suspension of Shiga bacilli. Prepare 

 also a control without the serum. In both tubes lysis proceeds normally 

 and in a parallel fashion. Here, then, the serum has exerted no inhibitory 

 action. 



