BACTERICIDAL ACTION OF NORMAL SERUM 205 



And in series (c) we use the serum treated as in (6), and 

 after time for absorption add 0-01 c.c. of anti-F. Metchnikovi 

 serum. 



The tubes of all three series are placed in the incubator 

 for two hours at 37 C., and thereafter the test amount of 

 living V. Metchnikovi is added, and plates are made after 

 the usual incubation period, namely, three hours. 



The three following tables give typical results of experi- 

 ments of this nature : 



EXAMPLE 1. Partial Exhaustion by the Homologous Organism 

 y. Metchnikovi. 



In this case the result is what one would expect on the 

 supposition that a natural immune-body for V. Metchnikovi 

 is concerned in the bactericidal action of normal serum for 

 this organism. The previous treatment with the dead 

 emulsion of V. Metchnikovi would remove the , natural 

 immune-body, hence the great fall in bactericidal effect ; 

 whereas the addition of an artificially produced immune- 

 body more than restores the bactericidal action by bringing 

 complement into union with the organisms. Such an ex- 

 planation will, however, not hold in the following examples, 

 where heterologous organisms are used. 



