BACTERIOLYSIS AND ALLIED PHENOMENA l6g 



amboceptor. These facts are admitted by Ehrlich, but he shows 

 that they do not constitute any real evidence against the pluralist 

 conception, since in some cases it may be shown that, though all 

 complements are absorbed, this may be at different rates, and by 

 stopping the process at a proper time, some may have disappeared, 

 whilst others are left. 



The practical importance of these observations arises from the 

 fact that they give us a method by which we can demonstrate the 

 presence or absence of an antibody to a given antigen, or of an 

 antigen to a given antibody. For example, the sensibilatrice or 

 amboceptor for the tubercle bacillus is very difficult to demonstrate, 

 since the organism is so resistant that it is never obviously dis- 

 solved, even partially, in the most potent serum we can obtain. 

 Nor are bactericidal experiments more promising, owing partly to 

 the resisting power of the organism and partly to the technical 

 difficulties. The only evidence (apart from the presence of 

 agglutinins) which we have in favour of the formation of specific 

 antibodies to tuberculosis is derived from an application of Bordet's 

 phenomenon. The experiments were carried out as follows : A 

 guinea-pig was injected with the bacillus of avian tuberculosis, to 

 which it is but slightly sensitive, and the blood was examined by 

 mixing it with an emulsion of the bacilli. If amboceptors were 

 present they would combine with the bacilli, and draw to them all 

 the complements of the fluid, which would thus lose its power of 

 activating suitably sensitized red corpuscles. This was found to 

 occur, and Bordet and Gengou deduced that the guinea-pig had 

 formed antibodies to the slightly virulent tubercle bacilli. When, 

 on the other hand, the guinea-pigs were injected with virulent 

 human tubercle bacilli, no such antibodies could be demonstrated. 



As an example of the recognition of an antigen by means of 

 Bordet's phenomenon, we shall quote Bruck's demonstration of 

 the presence of tuberculin, or at least of some derivative of the 

 tubercle bacillus, in the blood of patients suffering from general 

 tuberculosis. Here the problem is changed. We have a specimen 

 of serum which we want to test, not for the antibody, but for the 

 antigen. The procedure is as follows : The serum is heated and 

 mixed with a serum known to contain antibodies to the tubercle 

 bacillus (antituberculin of Hochst). To this mixture is added 

 fresh guinea-pig's serum, and lastly sensitized red corpuscles. It 

 is found that no haemolysis takes place. In a control experiment, 

 in which normal human blood took the place of that from the 



