210 ANTI-BACTERIAL PROPERTIES OF SERUM 



amounts of the anti-serum 0-0001 to 0-1 c.c., we obtained 

 no Neisser-Wechsberg effect, all these amounts greatly 

 increasing the bactericidal effect of normal serum. This is 

 the serum which we have employed in most of the experi- 

 ments described above. It is not our purpose to discuss 

 these phenomena at present we mention them in order to 

 illustrate how much the properties of an immune-serum 

 may vary a fact which is not sufficiently recognized. The 

 only property which the three sera have in common is that 

 of leading to increased absorption of complement when used 

 in combination with the homologous organisms, i.e. the 

 Bordet-Gengou effect. As we have shown above, by this 

 method, which is essentially the employment of powerful 

 complement absorbers, bactericidal complement, hsemolytic 

 complement, and normal labile opsonin are all absorbed. 



From what has already been stated it will be evident 

 that we consider it impossible to suppose that the comple- 

 ment content is uniform ; that is, is made up of identical 

 molecules. Ehrlich, as is well known, has maintained the 

 plurality of complements, and in association with his co- 

 workers has given examples in proof of this contention. 

 We ourselves, in a previous section on haemolysis (p. 77), 

 have cited an example of this, namely, that sensitized guinea- 

 pig's corpuscles absorb the complement for sensitized ox's 

 corpuscles in much greater proportion than they absorb the 

 complement for sensitized guinea-pig's corpuscles. Differ- 

 ences in complement molecules as regards combining affinities 

 and certain physical properties undoubtedly exist. We have, 

 on the other hand, given examples where the differences 

 between complements of different animals are much greater 

 as regards the zymotoxic group than as regards the hapto- 

 phore group (p. 85). In the present series of observations 

 the differences in the complement content which come out 

 are quantitative rather than qualitative. 



An emulsion of bacteria may absorb bactericidal comple- 

 ment more readily than haemolytic complement, but if a 



