194 Chapter VII 



and Morgenroth lay special stress on the importance of an experi- 

 ment which has enabled them, by means of filtration, to separate 

 two complements from the normal serum of the goat, one of them 

 attacking the red corpuscles of the guinea-pig, the other those of the 

 rabbit. 



Max Neisser^ has adopted this view of the plurality of alexines. 

 According to Ehrlich and Morgenroth, the same serum may possess 

 several complements which attack the red blood corpuscles of various 

 species and other complements which attack micro-organisms. In 

 favour of this thesis Neisser gives a summary of his experiments on 

 tlie absorption of complements which, in his opinion, prove the 

 plurality of alexines. By centrifugalising rabbit's blood serum to 

 which he had previously added a certain number of anthrax bacilli, 

 he obtained a fluid which no longer destroyed this bacillus but 

 which still dissolved the red corpuscles of goat and sheep. There 

 are then, according to Neisser, in the normal serum of the rabbit, at 

 least two different complements ; one for the bacilli and one for the 

 red corpuscles. 



With the object of explaining the discrepancy between these 

 results and those of his previous experiments, Bordet^ undertook 

 [205] a new series of researches on the absorption of cytases. He first 

 made it clear that the normal red corpuscles, when plunged into a 

 normal haemolytic serum, are incapable of fixing all the cytase. 

 When such a serum is centrifugalised, after a prolonged contact 

 with red corpuscles of a different species, the fluid no longer dissolves 

 normal red corpuscles. But if these latter be sensibilised by means 

 of a specific fixative, the red corpuscles are dissolved in large 

 numbers. It must be admitted that in this experiment we have 

 to do with a single cytase because, before centrifugalisation, as after 

 it, the red corpuscles of the same species are added. In the first 

 case, however, these corpuscles were normal, whilst in the second 

 they were sensibilised by the fixative. 



When, after the first part of this experiment, that is to say, after 

 the fixation of a certain quantity of cytase by the red corpuscles, we 

 centrifugalise the mixture and add, not the sensibilised red corpuscles 

 of the same species but the normal red corpuscles of a different 

 species, we find that the latter stiU dissolve and fix a certain quantity 

 of cytase. As the first experiment (with sensibilised red corpuscles) 



^ Deutsche med. IVchnschr., Leipzig, 1900, S. 790. 

 2 Aim. de I' Inst Pasteur, Paris, 1901, t xv, p. 303. 



