208 BIOLOGICAL CHEMISTRY 



ment is altered so that it will not cause hydrolysis and the 

 altered complement is united to the substrate by an amboceptor 

 a portion of fresh enzyme cannot unite with the substrate 

 owing to the substrate being saturated with amboceptor and 

 altered complement. 



There are certain practical applications of the above 

 relations between complement and amboceptor. 



WASSERMANN REACTION 



In the Wassermann reaction for diagnosis of syphilis the 

 complement is used up by a special reaction and then the 

 absence of complement is demonstrated by the use of red 

 blood corpuscles and an inactivated hsemolytic serum. The 

 mixtures are made as follows : 

 A Inactivated blood serum + Antigen consisting of lipoid 



from healthy person extract 



B Inactivated blood serum -f- Antigen consisting of lipoid 

 from suspected case of extract 



syphilis 



C Inactivated blood serum -f Antigen consisting of lipoid 

 from known case of extract 

 syphilis 



to each of which is added fresh serum containing complement. 

 In A the serum does not unite the complement to the 

 antigen, but in C the complement is fixed. In B the comple- 

 ment is or is not fixed, depending on whether the case is or 

 is not syphilitic. 



To each of these is added an emulsion of red blood corpuscles 

 which have been " sensitised " by inactivated haemolytic 

 serum ; so that they are hsemolysed by the addition of comple- 

 ment. 



In A complement is present, but it is absent in C. Thus 

 haemolysis occurs in A but not in C. If haemolysis occurs in 

 B the unknown serum is not syphilitic and the converse. 



This test is not infallible, but it is a very useful guide in 

 diagnosis. Using specific agglutinating serum it is possible 

 to show complement " deviation " by bacteria, and this method 

 is used for the differentiation of bacterial species. 



SERUM TEST FOR PREGNANCY 



By digesting an emulsion of placental tissue (autolysis) 

 with blood serum it is claimed that the digestion occurs more 

 rapidly if the serum is from a case of pregnancy than from a 

 non-pregnant case. This is shown by allowing the digestion to 

 occur in dialysing tubes of parchment paper so that the amino 



