FIXATION OF THE COMPLEMENT 



237 



r[f, however, the results had been as follows : 

 Tubes Nos. 1, 2, and 3 == complete haemolysis. 

 Tube No. 4 = slight haemolysis. 



it would have been concluded that the vibrio had not been sensitized by the 

 cholera immune serum ; that consequently there was no fixation of the 

 complement ; and that therefore the vibrio could not have been the cholera 

 vibrio. The assumed occurrence of partial haemolysis in tube No. 4 is to be 

 explained as due to a slight excess of bacterial emulsion ; the micro 

 organisms alone having absorbed some of the complement in the manner 

 already described (p. 235). 





DETAILS OF A COMPLEMENT-FIXATION EXPERIMENT AS ARRANGED FOR THE 



IDENTIFICATION OF A SUSPECTED CHOLERA VIBRIO (see p. 236). 



To put the result beyond all doubt it is still necessary to show : 



1. That the cholera serum in the quantity in which it was used does not 

 fix the complement in presence of any other species of bacterium, and in an 

 actual experiment an additional control tube would have been introduced 

 containing instead of the vibrio emulsion an emulsion of, for instance, the 

 typhoid bacillus. Haemolysis should, of course, occur under these conditions. 



2. That the vibrio under investigation does not fix the complement in 

 presence of another serum. Another control tube would therefore be prepared 

 with the emulsion of the vibrio but substituting, for example, an antityphoid 

 serum for the anticholera serum. Here again haemolysis should take place. 



The above then is the method of applying the complement fixation reaction 

 to the identification of an unknown organism. The data can be reversed 



