7o8 MICROBIOLOGY OF DISEASES OE MAN A^^D DOMESTIC ANIMALS 



with complement. Occasionally complement is absorbed by tissue 

 cells and prevented from combining with amboceptor. In case there is 

 an excess of amboceptors in a serum and only a small amount of com- 

 plement, it may be deviated. In this case the cells will have taken up 

 all the possible amboceptor and there will be an abundance of ambo- 

 ceptor free in the serum. It has been demonstrated that complement 

 will combine with free amboceptor before it will combine with the 

 amboceptor which has been bound to the cells. In this case all the avail- 

 able complement will be taken up by the amboceptor which is free and 

 consequently there will be no lysis. This fact is of importance irj. certain 

 infections where the development of bacteriolytic substances are of 

 importance and necessary in effecting a recovery. The infectious 

 microorganisms may not be destroyed for the above reason. 



The Deflection of the Complement as a Test for -A ntibodies. — A very in- 

 genious procedure has been devised for the testing of serums for xmknown 

 antibodies similar to bactericidal substances and lysins. The method 

 of demonstrating the fixation of the complement was first worked out 

 by Bodet and Gengou. The reaction is made use of in the test for 

 syphilis which is briefly stated as follows: when the syphilitic antigen 

 is combined with the supposed amboceptor in the blood serum of the 

 suspected case of syphilis and a foreign complement, which has been 

 accurately standardized, is added, this complement is bound and is, 

 therefore, prevented from combining with red blood corpuscles, and 

 a hemolytic amboceptor which may be added later. Hemolysis is, 

 therefore, prevented. Thetechnicof the test is as follows: the syphi- 

 litic antigen is prepared by making an aqueous or alcoholic extract of 

 the Hver of syphilitic fetus or in several other ways. This antigen is 

 supposed to contain the protein products of the Treponema pallidum, 

 the etiological microorganism of syphilis. The blood serum of the 

 suspected case of syphilis is heated to 56° for thirty minutes in order 

 that the normal or immune serum complement may be destroyed. The 

 new complement is supplied from normal guinea-pig serum. Before 

 beginning the test it is necessary to have a rabbit immunized with some 

 hemolytic antigen, such as sheep erythrocytes. There is developed in 

 the serum of the rabbit the hemolysin for sheep corpuscles which when 

 combined with these corpuscles will cause a liberation of hemoglobin. 

 In the rabbit serum there are both hemolytic amboceptors and comple- 

 ment. It is necessary to heat this hemolytic rabbit serum to 56° for 



