APPLICATIONS OF BACTERIOLOGY 257 



We know that complement (*.*., fresh normal serum) is fixed 

 by the combination antigen-antibody. Let us prepare two 

 such combinations : 



(1) Cholera vibrios and anticholera serum (heated to 56* C. 

 to destroy its complement). 



(2) Blood corpuscles and haemolytic immune body 

 (haemolytic immune serum heated to 56 C.). 



Now on the first combination fix complement (*>., add fresh 

 serum to the mixture and put in the incubator : the complement 

 exerts its bacteriolytic action). 



Now add the second combination ready for haemolysis and 

 return to the incubator. If the serum contains haemolytic 

 complement over and above the bacteriolytic, its presence 

 will be shown by the laking of the corpuscles and the 

 red tint spreading throughout the mixture. If, on the other 

 hand, no haemolysis occurs, it means that the first fixation 

 has used up all the complement of the fresh serum : there 

 is no haemolytic complement therefore distinct from the 

 bacteriolytic. 



Given a mixture complement + immune-body (antibody) 

 + antigen, we have always a means of knowing if the com- 

 plement has been fixed, namely, to add a mixture of blood 

 corpuscles and haemolytic immune-body ready for haemolysis. 

 Laking of the blood indicates the absence of a previous 

 fixation of the complement. For example, a serum is sent to 

 us of a man who has been suffering for some time from fever ; 

 typhoid fever is suspected ; if this is the case his blood ought 

 to contain an antibody (antityphoid immune-body) and in the 

 mixture of complement + serum of the patient + typhoid 

 bacilli, the complement will be fixed on the bacilli through the 

 intermediation of the serum. If after a suitable lapse of time 

 one adds to the same tube a mixture of haemolytic antibody 

 and red corpuscles, the complement being no longer free, the 

 corpuscles are not dissolved. 



Bordet's reaction furnishes therefore a means of recognising 

 by the presence or absence of haemolysis the presence or 

 absence of another immune-body (antibody), and in conse- 



