BACTERIOLYSIS AND ALLIED PHENOMENA 163 



theses can be adduced which have been so rich in leading to the 

 discovery of new facts. 



It will now be necessary for us to glance briefly at some 

 alternative hypotheses, and it must be pointed out that the com- 

 paratively short notice they will receive must not be taken to 

 imply that there is less to be said in their favour. The trend of 

 modern research tends on the whole against Ehrlich's views ; yet 

 in the history of immunity his researches will always be regarded 

 as of the greatest interest and value. 



It may be pointed out that the cast-off receptors of red 

 corpuscles, bacteria, etc., may combine with the complemento- 

 phile groups of an amboceptor, and thus appear to act as a 

 cytophilic anti -amboceptor. 



Bordet holds that the immune body is not an amboceptor at 

 all i.e., that it does not act as a link between the corpuscle or 

 bacterium and the complement, but that it sensitizes the former 

 and renders it susceptible to the action of the latter. On Ehrlich's 

 theory, amboceptor unites with cell and complement with ambo- 

 ceptor; on Bordet's, both substances unite with the cell direct. 

 On the latter theory many, if not all, of the results observed by 

 Ehrlich and others are explicable, and there appears to be no 

 experimentum cruets by which the truth can be determined. A diffi- 

 culty in the way of accepting Ehrlich's amboceptor theory is this : 

 there is no proof that complement and immune body ever unite 

 unless the latter has already combined with a cell, or with anti- 

 amboceptor, or with free receptors. The only example to the 

 contrary is supplied by Ryes' cobra-lecithid, which, though of 

 great interest, can hardly be quoted as a case in point, since 

 lecithin differs so markedly from the ordinary thermolabile 

 complements of serum. Another case (in the deviation of the 

 complements) in which this process appears to take place is 

 extremely complicated, and the evidence ,in favour of the direct 

 union of complement and antibody quite unsatisfactory. It 

 follows, then, that we must either assume that the mere union 

 of the cytophile group of the antibody with some other object 

 increases the affinity of the complementophile group for comple- 

 ment (as has been done here), or we must agree with Bordet that 

 cell and complement unite directly, but only after the latter has 

 been prepared by the action of immune body. A very important 

 observation of Muir's is of interest in this connection. Muir 

 showed that after red corpuscles had been saturated with immune 



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