GENERAL TECHNIC 417 



V. Antigen. As was previously stated, the ordinary alcoholic 

 extracts of syphilitic livers used as " antigens" in conducting the Wasser- 

 mann reaction are not biologically specific. It is generally accepted that 

 even in watery extracts of syphilitic livers the main antigenic principles 

 are lipoidal substances, independent of the Treponema pallidum itself. 

 Next to pure cultures of pallida, these aqueous extracts of luetic livers 

 come closest to being a specific biologic antigen. Although alcoholic 

 extracts of luetic liver may contain special lipoidal substances that 

 enhance their efficacy as antigens, yet, as shown by Noguchi, and as 

 confirmed later by us, alcohol does not serve well to extract pure cultures 

 of pallida, and therefore these extracts can hardly be regarded as specific, 

 in the sense that they contain antigenic principles of the spirochetes 

 themselves. The only specific biologic antigen is an aqueous extract 

 of a pure culture of pallida; this antigen is, however, much less service- 

 able than an ordinary organic extract, because the Wassermann reaction 

 depends upon the peculiar lipodophilic "reagin," which absorbs com- 

 plement with lipoids in a characteristic but biologically non-specific 

 manner. 



^The term "antigen," as ordinarily used in the Wassermann reaction, 

 must therefore be regarded as a misnomer. ; It is, however, so generally 

 used that it may be retained, with a distinct understanding as to its 

 actual meaning. 



With the discovery that alcoholic extracts of normal organs may serve 

 as antigen and that the chief antigenic principles reside in the lipoids, 

 it followed that extensive researches were undertaken in the hope of 

 discovering a lipoid, or a combination of lipoids, that would prove suffi- 

 ciently delicate to act specifically in the serum diagnosis of syphilis, and 

 not with normal serums or those of persons suffering from other dis- 

 eases. As a result, a large number of different extracts are in use. Each 

 has its own advocates, so that the general subject of antigens is the most 

 complicated one with which we have to deal in performing the Wasser- 

 mann reaction. 



While various organic extracts may be used, practical experience has 

 shown that some are better than others. It is important to remember: 



l. v That all antigens are capable in themselves of absorbing a certain 

 amount of complement. This is due to the presence of undesirable 

 extractives, some preparations containing more than others. In certain 

 doses, however, all antigens are capable of exerting this anticomple- 

 mentary action, and, other things being equal, that antigen is best which 

 shows this non-specification in the smallest degree. Before an antigen 

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