332 CYTOLYSINS 



portions of the complement were separated: the haptophore portion 

 corresponding to the mid-piece (the cell or bacterium being the first 

 piece), and the lytic cytophilic portion corresponding to the end-piece. 

 In successful complement splitting the mid-piece is believed to be in the 

 globulin fraction and the end-piece in the albumin fraction. Noguchi 

 and Bronf enbrenner 1 have cast considerable doubt upon these views, 

 and have shown that what is known as complement splitting is really 

 nothing more than an inactivation of the active principle of complement, 

 since both globulin and albumin fractions contain a part of the comple- 

 ment, a fact that can be demonstrated by the removal of the inhibiting 

 action of the acid or alkali used in the process. 



THE BORDET-GENGOU PHENOMENON OF COMPLEMENT FIXATION 



In the endeavor to demonstrate the unity of complement Bordet 

 and Gengou devised an experiment that has proved of great practical 

 value in the serum diagnosis of syphilis and other infectious diseases. 

 By mixing bacteria and their amboceptors with a little fresh serum con- 

 taining complement and letting the mixture stand aside for an hour or 

 so it was found that, upon the addition of corpuscles and their ambo- 

 ceptor, hemolysis did not occur, although the serum that had been used 

 as complement was capable, in its original condition, of producing hem- 

 olysis of these corpuscles. Bordet advanced this experiment to show 

 that the complement concerned in bacteriolysis is the same as that at 

 work in hemolysis, and consequently concluded that there is but one 

 single complement. 



This experiment of Bordet is usually spoken of as the "Bordet- 

 Gengou phenomenon," and is now used extensively in determining 

 whether or not a given serum contains certain amboceptors. The serum 

 to be tested is first inactivated, treated with the antigen composed of an 

 emulsion of the bacterium whose amboceptor it is desired to discover, 

 and then mixed with a small quantity of a fresh normal complement 

 serum. The mixture is placed in the incubator for an hour, during which 

 time the bacterial antigen unites with its amboceptor and the comple- 

 ment, i. e., fixes the complement, so that when red blood-cells previously 

 sensitized with heated hemolytic serum are added, hemolysis does not 

 occur because the complement in the fresh serum, which was suitable 

 for lysis of the sensitized corpuscles, has been " fixed" by the bacteria 

 by reason of the presence of specific amboceptors in the serum tested 



1 Jour. Exper. Med., 1912, 15, 598 and 625. 



