376 BACTERIOLYSINS 



CONTROLS 

 Control 1: 0.5 c.c. culture plated immediately: many thousands 



of colonies. 

 Control 2: 0.5 c.c. culture plated after being incubated three hours: 



plate very crowded; number of bacteria increased. 

 Control 3 : Varying amounts of normal rabbit serum used as com- 

 plement. The first plate containing 0.1 c.c. serum showed a 

 slight bactericidal action; the remaining plates showed many 

 thousand of colonies and were comparable to control No. 1. 

 Control 4: 0.5 c.c. complement serum: sterile. 

 Control 5: 0.01 c.c. inactivated immune serum: sterile. 

 Control 6: 0.01 c.c. inactivated normal control serum: plate shows 



several colonies of contaminating bacteria. 

 Control 7: 0.01 c.c. inactivated immune serum plus culture: plate 



shows many thousands of colonies. 

 Control 8: 0.01 c.c. of inactivated normal serum plus culture: 



many thousands of colonies. 



An examination of this experiment shows that the dose of culture 

 was satisfactory, that the culture increased during the three hours of 

 primary incubation, that the complement serum was very slightly 

 bactericidal in a dose lower than that used in making the test, and that 

 the technic was fairly satisfactory, slight contamination being present 

 in but one plate -that of the inactivated normal control serum. 



The most striking result observed is the absence of bactericidal ac- 

 tivity in the first two plates, which contained the largest amount of 

 immune serum and where one would naturally expect to find complete 

 sterility. The titer of this serum was between 1 : 3200 and 1 : 6400. 

 According to Neisser and Wechsberg, these paradoxic results are caused 

 by deviation or "deflection of complement," as was explained in a pre- 

 vious chapter. In bactericidal experiments, according to Neisser, the 

 deflection is caused by an excess of amboceptors in the immune serum. 

 In a mixture of bacteria, complements, and large amounts of amboceptor 

 the complement is bound not only by the amboceptors anchored to the 

 bacteria, but also in large measure by "free" amboceptors that are not 

 anchored to bacteria. A portion of the anchored amboceptor, therefore, 

 finds no complement at its disposal, and is, therefore, unable to exert any 

 bactericidal action, which gives rise to a relative lack of complement. 



This phenomenon resembles the action of agglutinoids in the agglu- 

 tination reaction, where, in the lowest dilutions, agglutination is feeble 

 or absent, but becomes manifest in the higher dilutions. 



