TECHNIQUE OF BACTERICIDAL TEST-TUBE EXPERIMENTS. 355 



fully killed (65 for J-l hour) and centrifuged will suffice. In these 

 cases, however, the supernatant fluid must always be examined 

 microscopically to make sure that all the bacteria have been removed 

 by the centrifuging. For any such dead bacteria loaded with ambo- 

 ceptor, which should remain in the fluid, would serve to deflect com- 

 plements in the further course of the experiment. However, in 

 many cases it is possible to remove all the bacteria by centrifuging. 

 In that case it is easy to show that the bactericidal, as well as the com- 

 plement-deflecting power of the serum, has disappeared with the absorbed 

 amboceptor. If only the deflecting power of the serum remains, 

 while the bactericidal power has disappeared, and if the comparative 

 test has shown that one was not dealing with a normal anticom- 

 plement or such like, we conclude that a complementophile ambo- 

 ceptoid is present, one which has originated from the amboceptor 

 produced by immunization. 



In many cases in which a plate test, as it has previously been 

 decribed, has seemed unsuited, another method has been used to 

 overcome the difficulty. Thus after allowing the immune serum to 

 act, instead of pouring plates, one can take a loop from each test- 

 tube and make slant agar streaks. If one the nmerely regards 

 very broad results, such as no growth, luxuriant growth, one will 

 obtain, by this simple means, useful comparative values. In this 

 way Dr. Lipstein and I have several times determined the power 

 of a gonococcus serum which we produced by immunization. 



