108 APPLIED IMMUNOLOGY 



ten days, or two weeks at the most, we are able to pre- 

 pare a powerful hgemolytic amboceptor, which re- 

 quires four or five weeks by the intraperitoneal 

 method. 



Titration of Hcemolytic Amboceptor, — For use in 

 the Wassermann test we aim to produce a hsemolytic 

 amboceptor of such strength that 1 c.c. of not less than 

 a 1-2000 dilution of rabbit's serum will hasmolyze 1 

 c.e. of a 5 per cent, suspension of sheep's corpuscles 

 in the presence of 0.1 c.c. of fresh guinea-pig serum 

 used as complement. Usually, by the intravenous 

 method described, the rabbit can be immunized so that 

 its serum in 1-3000 dilution will fulfil these re- 

 quirements. To determine the strength of the hsemo- 

 lytic serum, three or four days after the third injection 

 of the rabbit, about 2 c.c. of blood are drawn into a 

 small test-tube from a vein of the rabbit's ear. When 

 the blood has clotted and the clear serum separated, 

 the latter is drawn oiF and the natural complement in 

 it destroyed by heating the serum in a water-bath for 

 half an hour at 56° C. This deprivation of comple- 

 ment is known as inactivation. The complement used 

 in titrating the hsemolytic amboceptor and in the 

 Wassermann test itself is furnished by serum of the 

 guinea-pig, as it has been found that this animal has 

 an almost constant amount of complement present in 

 its blood. To obtain complement, a full-grown guinea- 



