196 ANTI-BACTERIAL PROPERTIES OF SERUM 



amount of complement, and a large number with the smallest. 

 A period of two hours at 37 C. was allowed in each case for 

 absorption by the dead organisms ; the tubes of the control 

 series containing no organisms being placed in the incubator 

 at the same time. At the end of that time the test amount 

 of living organisms was added to each tube, and a further 

 incubation period of three hours at 37 C. was allowed for 

 bactericidal action to occur. 



REMOVAL OF BACTERICIDAL ACTION BY HOMOLOGOUS 

 BACTERIA 



In this series of experiments we have endeavoured to find 

 the smallest amount of dead culture of an organism which 

 will distinctly reduce the bactericidal action of a given 

 amount of serum for the same organism. The amount of 

 living culture has varied, but it has been so adjusted that, 

 with the highest amounts of normal serum, killing of the 

 bacteria is complete, or very nearly so. The following are 

 examples : 



EXAMPLE 1. Vibrio Metchnikovi. Inoculation with 0-0005 c.c. 

 24:-hour bouillon culture of V. Metchnikovi. 



From this experiment it is seen that 0-001 c.c. of dead culture 

 distinctly reduces the bactericidal effect on 0-0005 c.c. of living 

 culture. 



