DIFFERENTIATION OF PROTEIDS BY COMPLEMENT FIXATION 1 95 



plement fixation. If it is required to know how delicate the complement 

 fixation reaction can be with this dose of antiserum, the following 

 experiment (Table IV) is performed. 



Diminishing amounts of human serum are mixed with a constant 

 quantity of complement and with this constant dose of antiserum. At the 

 same time a control series of tubes is used, in which the antiserum is 

 substituted by salt solution. After one hour of incubation at 37 C. 

 erythrocytes and hemolysin are added. 



TABLE IV. 



It is seen from the above table that o.ooooi c.cm. of human serum still 

 suffices to give a partial although incomplete fixation of the complement. 

 The delicacy of the antiserum in this particular instance is not very great. 

 In forensic practice, the reaction is carried out as shown in Table IV, but 

 instead of the human serum, the solution of unknown blood stain in various 

 dilutions is titrated. Control series B should not be omitted, because here, 

 any foreign substance contained in the extract and which might interfere 

 with the reaction can be detected. 



i :'6Xo. 2 c.cm. means o. 2 c.cm. of a 1:6 dilution. 



