IMMUNITY AND SUSCEPTIBILITY. 563 



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, there- 

 fore, prevented. The technic of the test is as follows: the syphilitic 

 antigen is prepared by making an aqueous or alcoholic extract of the liver 

 of a syphilitic fetus. This antigen is supposed to contain the protein prod- 

 ucts 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 cor- 

 puscles which when combined with these corpuscles will cause a liberation 

 of hemoglobin. In the rabbit's serum there is both hemolytic ambo- 

 ceptor and complement. It is necessary to heat this hemolytic rabbit 

 serum to 56 for thirty minutes in order to destroy its complement 

 and also it is necessary to find out accurately the amount of guinea 

 pig serum which will complement the resulting hemolytic amboceptor. 

 This definite amount of complement having been determined, it is 

 mixed with syphilitic antigen plus the suspected syphilitic amboceptor 

 mentioned above and allowed to incubate for one hour and thirty minutes 

 at 37. If the serum is from a case of syphilis the antibodies (ambo- 

 ceptors) will be present and combine with the antigen, and also the guinea 

 pig serum complement. The next step in the technic is to add to the 

 above-mentioned mixture the hemolytic amboceptor and its antigen, 

 sheep corpuscles. If the complement has been bound there will be 

 none left to combine with the hemolytic amboceptor and no hemolysis 

 of the sheep corpuscles will result. If the patient's serum does not con- 

 tain syphilitic amboceptors or antibodies the complement will not be 

 bound and hemolysis will result. This test has been designated as the 

 Wassermann test, on account of the man first working it out in the 

 case of syphilis, and has shown itself to be very efficient in the diagnosis 

 of this disease. 



The fixation of the complement may be made use of in the detection 

 of any bacterial antibody, the procedure being the same as above in- 

 dicated and the hemolytic system used as an indicator as in the case of 



