THE TECHNIQUE OF SERUM REACTIONS 273 



Protein Differentiation by Complement Fixation. That the technique 

 of complement fixation was applicable to the determination of specific 

 proteid antigen such as human or animal blood was shown by Gen- 

 gou l in 1902. The principles worked out by him have been practically 

 applied by Neisser and Sachs 2 and others to the forensic differentiation 

 of animal proteids and these tests are said to be more delicate and 

 reliable than precipitation tests made for the same purpose. 

 The substances necessary for the reaction are as follows: 



1. Complement, titrated as above. 



2. Hemolytic amboceptor as above. 



3. A five-per-cent emulsion of sheep corpuscles as above. 



4. Specific antiserum. 



This is obtained from a rabbit immunized with the proteid for which 

 the test is to be made; viz.: human or animal blood serum. This must 

 be titrated. In order to do this, diminishing quantities of the antiserum 

 are mixed in a series of tubes with the determined quantity of comple- 

 ment, and the antigen which is to be tested for, i.e., the homologous 

 serum with which the antiserum has been produced. Since the test 

 should be sufficiently delicate to determine 0.0001 c.c. of the antigen, 

 this quantity is added to each tube. The actual titration is as 

 follows : 3 



1. Antiserum, undiluted .1 + homologous serum .0001 + complement. 



2. Antiserum diluted by 10.75+ homologous serum .0001 + complement. 



3. Antiserum diluted by 10.75+ homologous serum .0001 + complement. 



4. Antiserum diluted by 10.3 + homologous serum .0001 + complement. 



etc., down to .1 



These tubes are incubated for one hour and hemolytic amboceptor 

 and red blood cells are added. The smallest quantity of antiserum 

 which has completely inhibited hemolysis is the "unit," and one and a 

 half to two times this quantity is used for the test. 



5. A solution of the blood spot or other material to be tested pre- 

 pared as for precipitin test. (See page 254.) 



For the actual test the following mixtures are made in a series of 

 tubes, each of which contains: 



1 Gengou, Ann. de 1' Inst. Pasteur, 1902. 



2 Neisser und Sachs, Berl. klin. Woch., 1905 and 1906. See also Citron, in Kraus 

 and Levaditi "Handbuch," etc, 



8 Citron, loc. cik 



