INHIBITION OF COMPLEMENT. 281 



be regarded as distinct antibodies, receptors of 

 the first order. Moreschi, however, has thrown 

 doubt on the existence of such distinct antibodies 

 for the reason that in using normal serum as com- 

 plement a mixture of protein substances is used 

 giving rise, in immunization, to antialbuminous 

 bodies which react with the antigen to form com- 

 binations which inhibit or bind complement. Such 

 combinations in the form of precipitates may be 

 demonstrated to act as anticomplements. The 

 existence of true anticomplements, therefore, 

 while not disproved, has not been satisfactorily 

 demonstrated. 



The presence of complementoid in inactivated 

 serum may also act as a cause of complement in- 

 hibition by occupying the receptors of the anti- 

 body. When these various factors which com- 

 plicate the complement fixation reaction are con- 

 sidered, it will be seen that great care must be 

 taken in both the technic and the interpretation of 

 results. 



The substance concerned in antigen, antibody Nature of 

 complement fixation is obtained by processes of Deviation 

 immunization similar to those concerned in other 

 antibodies. In the one case the reaction is fol- 

 lowed by perceptible results, in the other by 

 fixation of complement. The question arises: are 

 the antibodies in these two kinds of reaction iden- 

 tical or not? 



That the complement fixation antibody is dis- 

 tinct from precipitins and agglutinins is indi- 

 cated in different ways. Muir and Martin, by 

 immunizing rabbits with guinea-pig serum, ob- 

 tained an antibody capable of complement fixation 



