BACTERICIDAL ACTION OF NORMAL SERUM 211 



sufficient amount be used the latter will be taken up also. 

 Bordet and Gengou showed that sensitized bacteria of 

 various kinds took up haemolytic complement, and came to 

 the conclusion that bactericidal and haemolytic complements 

 are identical. Though their results are valid, their conclu- 

 sion is not justified. Because various complements are taken 

 up by powerful absorbers, it does not follow that they are all 

 the same, and as a matter of fact weaker absorbers bring out 

 differences. The results of the present series of experiments 

 show that differences in combining affinity exist, but these 

 are quantitative rather than qualitative ; though by other 

 methods certain qualitative differences can also be established. 



CONCLUSIONS 



1. A distinction is to be drawn between absorption of 

 complement by bacteria and the bactericidal effect which 

 may follow, the latter implying a sensitiveness of the bac- 

 terium to the combined complement. Organisms may 

 absorb complement by themselves, and to a greater extent 

 through the medium of an artificial immune-body, without 

 being killed. 



2. Treatment of a normal serum with increasing amounts 

 of a dead emulsion of a bacterium usually produces effects 

 in the following order : (a) diminution of the bactericidal 

 action on the same bacterium; (b) diminution of the bacteri- 

 cidal action for other bacteria ; (c) diminution of haemolytic 

 complement. 



3. Bactericidal action of normal serum for one organism 

 can be greatly reduced by treatment with other organisms in 

 the dead condition, without the haemolytic effect being 

 appreciably altered. This shows that there is a moiety of 

 the serum which has a special affinity for bacteria in general, 

 and is mainly concerned in bactericidal action when such 

 occurs it may be called bacteriophilic complement. 



4. When the bactericidal action of normal serum for a 

 particular organism has been greatly reduced by treatment 



