268 INFECTION AND IMMUNITY 



volume brought up to 3 c.c. with normal salt solution. This mixture is 

 thoroughly shaken, and placed for one hour in a water bath or in the 

 incubator at 37.5° C. At the end of this time, there is added 1 c.c. of 

 a 5 per cent emulsion of sheep's corpuscles, and two units of hemolytic 

 amboceptor, determined by a titration of the inactivated hemolytic 

 rabbit serum, as described above. This mixture is again placed at 37.5° 

 C. for one to two hours. If the antibody is present in the suspected 

 serum, no hemolysis takes place. If absent, haemolysis is complete. 



No test is of use unless suitable controls are made. The controls 

 set up should be as follows: 



Control 1. For each serum tested the mixture described above, 

 omitting antigen. 



Controls 2 and 3. The mixture made as in the test but with knoiun 

 syphilitic serum (2) with and (3) without antigen. 



Controls 4 and 5. The mixture made as in the test, but with 

 normal serum (4) with and (5) without antigen. 



Control 6. Antigen and complement alone, left together for an hour 

 before the addition of blood cells and amboceptor in order to preclude 

 the possibility of the antigen itself fixing complement. When working 

 with a well-controUed antigen this control may be omitted. 



Controls 7 and 8. The hemolytic system, complement, blood cells 

 and amboceptor, set up in order to show that the system is in working 

 order (7) with and (8) without antigen. It is convenient to set the 

 tubes in two rows in a rack, the front row containing antigen, the 

 back row containing the same mixture without antigen. 



In a positive test, the test itself, and Control 2, alone, should show 

 inhibited hemolysis. The other tubes should show complete solution 

 of the hemoglobin. (See scheme, p. 259.) 



Modifications of the Wassermann Test. — Baiter's Modification. — 

 Bauer ^ utilizes the fact that normal human serum contains a certain 

 amount of hemolytic amboceptor for sheep's corpuscles. In consequence 

 he omits in his reaction the use of specifically immunized hemolytic 

 rabbit serum. In carrying out the test he uses but four tubes: 



1. Contains 0.1 c.c. of complement, the titrated amount of antigen, 

 and 0.2 c.c. of the inactivated serum to be tested. 



2. Contains the same mixture without antigen. 



3. Is hke one, except that normal serum is substituted for that of the 

 patient. 



» Bauer, Deut. med. Woch., xii, 1908, and Berl. klin. Woch., xvii, 1908. 



