BACTERIOLYSIS AND ALLIED PHENOMENA 153 



These methods of heating, filtration, etc., of course only separate 

 the complements in certain lucky cases, and the more general 

 method involves the removal of some of these bodies by means of 

 sensitized red corpuscles. Thus fresh goat serum will reactivate 

 heated normal goat serum in its action on rabbits and on guinea- 

 pig's red corpuscles, the amboceptors for which are contained in 

 untreated animals. It will also reactivate the heated serum 

 of goats injected with rabbit's corpuscles, ox corpuscles, or dog's 

 corpuscles. Ehrlich and Sachs found that if they added this fresh 

 serum to rabbit's corpuscles, the complements which took part in 

 the two latter reactions were absorbed, whilst the others were 

 unaltered. Evidently, therefore, two complements at least are 

 present in goat serum. When the serum was allowed to act 

 on guinea-pig's corpuscles, the complements which reactivated 

 the normal amboceptors for rabbit's and guinea-pig's corpuscles 

 were removed, also that which activated the artificial ox ambo- 

 ceptor. By an elaboration of these methods Ehrlich and Sachs 

 were able to demonstrate that these five haemolytic actions depend 

 upon five different complements, each perfectly distinguishable 

 the one from the other. The subject will not be pursued farther, 

 though there is an abundance of evidence pointing to the same 

 end that the serum of every animal contains a very large number 

 of complements, some of which take part in one reaction, some in 

 another. As a rule, complements which take part in haemolysis 

 have no action on bacteria, or but little, and this is all the truth in 

 Metchnikoff 's theory of macro- and microcytase. 1 



Ehrlich lays it down as a law that amboceptors from a certain 

 species of animal are best complemented by complements from 

 this species, and this is true in general ; Muir has adduced some 

 exceptions. 



The main experimental basis for the Unitarian theory was 

 furnished by Bordet and Gengou. They found that if they added 

 "sensitized" bacteria i.e., bacteria which had been placed in 

 heated immune serum in fresh serum, all the complements were 

 removed, and the fluid would no longer dissolve sensitized red 

 corpuscles, so that evidently the haemolytic complement had been 

 removed. Again, Bordet showed that if he added fresh serum to 

 sensitized red corpuscles and allowed solution to take place, all 

 complements, bacteriolytic as well as haemolytic, were removed. 

 These facts are not disputed, and we shall have occasion to refer 



1 See p. 286. 



