BA CTERIOL YSINS A ND HMMOL YSINS 117 



A quantity of the serum to be tested is placed in a 

 test-tube with some antigen and a known amount of 

 complement is added. A sufficient amount of time 

 is allowed for the antigen to combine with the anti- 

 substance and for this combination to absorb the 

 complement. A definite amount of sheep cells plus 

 sheep cell antibody is added and the amount of 

 haemolysis which takes place is ah indication of the 

 amount of complement still free in the mixture. If 

 complete haemolysis takes place all of the comple- 

 ment was free. Consequently, none was absorbed 

 by the patient's serum plus the antigen and the 

 serum tested was, therefore, negative. If, on the 

 other hand, no haemolysis occurs, there is no free 

 complement. Therefore, it must have been ab- 

 sorbed by the patient's serum and the antigen. The 

 serum tested was, therefore, positive. 



THE WASSERMANN TEST IN DETAIL. 



PREPARATION OF THE REAGENTS. Before pro- 

 ceeding with the detailed description of the test itself 

 we shall describe the preparation of the various 

 reagents. In this we shall follow the technique 

 employed in the laboratory of the New York City 

 Department of Health under the supervision of one 

 of the writers. 



Patient's Serum. The clear serum collected from 

 the patient is inactivated at 56 C. for one-half hour. 



