174 THE PRINCIPLES OF IMMUNOLOGY 



periment required numerous controls, the complete series being indi- 

 cated in the following protocol : 



1. Plague bacilli -j- immune horse serum -f- complement + v sensitized cells = 



No hemolysis. 



2. Plague bacilli + normal horse serum -f complement + sensitized cells = 



Hemolysis. 



3. immune horse serum -f~ complement + sensitized cells 

 Hemolysis. 



4. normal horse serum + complement + sensitized cells = 

 Hemolysis. 



5. Plague bacilli -f- immune horse serum -f* sensitized cells = 



No hemolysis. 



6. Plague bacilli + normal horse serum + sensitized cells = 



No hemolysis. 



Throughout the experiment all the sera were inactivated except the 

 fresh guinea-pig complement and all mixtures stood at room tempera- 

 ture for five hours before the addition of the sensitized erythrocytes. 

 Hemolysis in tube 2 shows that normal horse serum does not serve 

 as an amboceptor or sensitizer for the plague bacilli and therefore 

 does not prevent the complement from entering into combination with 

 the sensitized erythrocytes. Tubes 3 and 4 contain no bacterial 

 antigen, cannot utilize complement and therefore hemolysis appears. 

 Tubes 5 and 6 show that the bacteria are not hemolytic and that 

 neither of the inactivated immune sera nor the inactivated normal horse 

 serum contain complement for the completion of the amboceptor-cell 

 complex. Bordet and Gengou showed that the same phenomenon could 

 be observed with a wide variety of bacteria and specific immune sera 

 both of human and lower animal origin; these operate to fix both 

 guinea-pig and human complements, so as to prevent combination of 

 these complements with hemolytic immune sera from several species. 

 Furthermore, the immune sera so fixed might be specific for several 

 varieties of erythrocytes. Muir and Martin found, however, that 

 whereas most complements can be fixed in such experiments, this is not 

 universally true and occasional complements are met with which do 

 not enter into certain combinations. Furthermore, the process could 

 be reversed so that the fixation of complement in hemolysis prevented 

 its action to bring about bacteriolysis of sensitized bacteria. Thus it 

 appeared that one and the same complement operates for the produc- 

 tion of both bacteriolysis and hemolysis. This demonstration of the 

 unity of complement has been combated by later work, and it now 

 appears that there are certain exceptions to the rule, although it can 

 generally be accepted. 



Laboratory Demonstration of the Bordet-Gengou Phenomenon. In 

 order to demonstrate the phenomenon it is not necessary to use plague bacilli, as 

 others serve the purpose equally well. The readily obtainable typhoid bacillus 

 and typhoid immune serum can be used with good results. In setting up the test 

 it is important to bear in mind the fact that numerous substances may interfere 

 with the activity of complement, and among these are certain concentrations of 



