FIXATION OF COMPLEMENT 155 



ment-fixation in 70 per cent, of 85 pathologically cer- 

 tain cases and in 66 per cent, of clinically certain cases 

 of tuberculosis. In 87 controls, taken from normal 

 and disease conditions, without any selection, all were 

 negative but three, these being two cases of leprosy 

 and one of Addison's disease. From these results the 

 reaction may be regarded as highly specific. 



The Complement-fixation Reaction as Applied to 



Protein Differentiation ( Neisser-Sachs 



Reaction) 



This method may be applied to supplement the re- 

 sults of the precipitation reaction, and may serve to 

 differentiate proteins where the precipitation reac- 

 tion fails. It is of practical importance in the medico- 

 legal identification of human blood. An anti-sheep 

 hgemolytic system is prepared in the same manner as 

 for the Wassermann reaction. For the identification 

 of human blood, an anti-human serum is made by in- 

 jecting a rabbit with human blood-serum. The anti- 

 serum should be prepared of such a strength that 0.03 

 or 0.04 c.c. will give complement fixation with 0.00001 

 c.c. of human serum. The antiserum having been 

 previously prepared, an extract of the suspected blood 

 is made in approximately 1-1000 dilution in the 

 same manner as for the precipitation reaction (see 

 Chapter X). 



The test is carried out according to the following 



