CHAPTER XIII. 



THE METHOD OF COMPLEMENT FIXATION. 



Its principle. Antituberculin. Ehrlich's side-chain theory. Serum diagnosis of 

 syphilis, and diseases caused by animal parasites. 



It has already been demonstrated that neither bacteriolysis 



The Question nor hemolysis can take place without the presence of comple- 



of Multipli- ment. The question therefore arises whether this complement 



city of Com- is the same in both of these reactions or whether normal serum 



plements. p osse sses different complements. In order to solve this, a 



number of very complicated experiments have been carried 

 out by Ehrlich and Morgenroth, Metchnikoff, and Bordet and Gengou. 

 Ehrlich and Morgenroth endeavored to show that not only do the comple- 

 ments of different animals of the same class vary, but that numerous com- 

 plements exist within one individual serum (conception of the multiplicity 

 of complements). Metchnikoff believed that each serum contained at 

 least two complements, the microcytase and the macrocytase, thus enlist- 

 ing the supporters of a dualistic theory. Bordet and his school, on the 

 other hand, although agreeing with the idea that the complement varies in 

 different animals, deny its multiplicity and contend that any given serum 

 contains but one alexin, or complement the theory of unity of complement. 

 It would be superfluous to cite all the experimental data supporting these 

 opinions, but nevertheless a review of the classical experiment of Bordet 

 and Gengou which corroborated the existence of only one complement, thus 

 offering the fundamental principle for the establishment of the most impor- 

 tant method of serum diagnosis, namely, complement fixation, would not 

 be out of place. 



Bordet and Gengou mixed in a test-tube typhoid bacteria 



The Principles ( an tig e n), inactivated typhoid immune serum (amboceptor) 



^enTrfcT anc * norma ^ semm (complement). Union of the bacteria and 



ation. immune serm first took place followed by absorption of, and 



coalescence with, the bacteriolytic complement contained in 

 the normal serum. As a result, bacteriolysis occurred and the bacteriolytic 

 complement was used up during this process. Bordet and Gengou rea- 

 soned that if the bacteriolytic and hemolytic complements were identical, 

 then in the above mixture of typhoid bacteria, immune serum and normal 

 serum, the hemolytic as well as bacteriolytic complement should be absent, 

 while if the plurality of complement exists, the hemolytic complement 

 should still be present. Accordingly, after a certain interval, washed 

 erythrocytes and inactivated homologous immune serum were added and 



152 



