THE TECHNIQUE OF SERUM REACTIONS 327 



In the actual test a -series of tubes are prepared each of which con- 

 tains : 



1. Complement, the determined quantity. 



2. Antiserum, the determined quantity. 



3. Diminishing quantities of the inactivated serum to be tested for 

 antigen beginning with 1 c.c. 



Salt solution is added for dilution to 3 c.c. 



These substances are left together at 37 to 40 C. for one hour and 

 then the required quantities of amboceptor and red cells are added. 

 The reaction is controlled by tubes containing the same ingredients 

 without the typhoid antiserum. In a positive test there will be no 

 hemolysis in the tubes containing the patient's serum. 



Protein Differentiation by Complement Fixation. That the tech- 

 nique of complement fixation was applicable to the determination of 

 specific protein antigen such as human or animal blood was shown 

 by Gengou 18 in 1902. The principles worked out by him have been 

 practically applied by Neisser and Sachs 19 and others to the forensic 

 differentiation of animal proteins and these tests are said to be more 

 delicate and reliable than precipitation tests made for the same pur- 

 pose. 



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 protein 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 complement, 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 titra- 

 tion is as follows : 20 



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



w Neisser imd Sachs, Berl. klin. Woch., 1905 and 1906, See also Citron, in 

 Kraus and Levaditi ' ' Handbuch/ ' etc. 

 - (} Citron, loe. cit. 



