the tentative antigen unit, a third test is applied. One, two and 

 four units of antigen are placed in tubes and a unit of corpuscles 

 is added to each, together with sufl&cient salt solution to make the 

 total volume i c.c, and these are incubated for an hour. The 

 corpuscles should not be laked. If they are laked the antigen is 

 itself markedly hemolytic. A satisfactory antigen should per- 

 form its specific function of fixing complement in the presence 

 of a s)rphilitic serum in an amount which is at most }io of the 

 amount which is in itself either anti-complementary or hemolytic. 

 It keeps well in the refrigerator as the alcoholic solution. The 

 dilution for use should be freshly prepared by slowly adding the 

 salt solution, a few drops at a time^ to the alcoholic antigen in a 

 test tube, with thorough shaking.^ 



The antigen is the element in the test which is designed to 

 enter into, chemical reaction with the specific substance in the 

 patient's blood, which is present there as a result of active syphilis. 

 During the course of this reaction, complement is absorbed 

 or destroyed. The nature of the lipoidophilic substance'' is un- 

 known. It behaves in the test very much as a specific immune 

 body \yould be expected to behave. Experience has shown that an 

 antibody of this- nature is rarely present in other conditions 

 than active syphilis and that it is present in this disease. Upon 

 the results of this experience we have to rely in ascribing diagnos- 

 tic value to the test. 



In performing a test for diagnosis, sera from several patients 

 should be tested at the same time, and one, two or three sera, pre- ' 

 viously tested and found to fix complement in varying degrees, 

 and at least one serum known to give a negative result, should 

 be tested along with the new samples. Three tubes are used for 

 each serum to be tested. The first incubation is carried out in the 

 refrigerator over night and the second incubation, after the addi- 

 tion of the sensitized cells is at 37° C. in the water bath. 



' The anticomplementary test upon one, two, three and four units of antigen 

 must be repeated every time a diagnostic test is'carred out and simultaneously 

 with it using the identical reagents. ' 



' ^Simon: Infection and Immunity, Phila., 1912, p. 272. 

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