292 IMMUNOLOGICAL METHODS OF DIAGNOSIS 



spirochetal antigen on the one hand and complement on the other. 

 As shown in Fig. 18, the complement would then be bound to a 

 greater or less extent as the result of the interaction between the 

 other two factors. Since the cultivation of the syphilitic spirochete 

 had at that time not been accomplished, however, Wassermann was 

 obliged to make use of extracts of organs which were rich in the 

 organisms in question. To this end he employed saline extracts 

 of livers from syphilitic fetuses. With such material as antigen 

 he then actually obtained complement fixation of marked degree, 

 and he very naturally concluded that the reaction which took place 

 was one corresponding to that occurring between a bacteriolytic 

 amboceptor and its corresponding antigen. 



Later studies, however, showed that this could not be the case, 

 since identical results were obtained with alcoholic extracts derived 

 not only from syphilitic organs, but from perfectly normal tissues 

 as well. At the present time we know that the reacting substance 

 of the "antigen" is in no sense a specific constituent of the spirochete, 

 but apparently a lipoid of the order of lecithin. The syphilitic anti- 

 body accordingly cannot be an amboceptor in the sense of Ehrlich, but 

 is evidently a substance which possesses a marked affinity for certain 

 lipoidal bodies, with which it is capable of interacting, with the 

 consequent absorption of complement. Of the nature of this inter- 

 action we know nothing. Pending investigations in this direction 

 we may nevertheless represent the process diagrammatically, as I 

 have done above, bearing in mind that in the Wassermann reaction 

 the factors designated as antigen and antibody are so termed only for 

 sake of convenience. For the antibody in question I would suggest 

 the term, lipoidophilic antibody, as denoting its essential characteristic 

 and its nature as a reaction product to infection. 



PREPARATION OF THE REAGENTS. 1. Preparation of the Antigen. 

 While Wassermann originally advocated the use of saline extracts 

 of syphilitic livers, and other investigators then showed that alco- 

 holic extracts of normal organs (heart, liver, kidney) answer the 

 purpose as well, Noguchi pointed out that the "antigenic" properties 

 of such extracts essentially belong to the acetone-insoluble fraction, 

 and that undesirable "side" reactions can be avoided by utilizing 

 this fraction only. For this reason I have abandoned the use of 

 simple alcoholic extracts altogether, and employ the acetone-insoluble 

 fraction exclusively. This is prepared as follows : Fifty or a hundred 



