R. L. KAHN 849 



practical problems, including the choice of an antigen, the general plan of the test, 

 and the interpretation of the results. Of major importance was the standardization of 

 antigen to assure uniform results in the hands of different workers, for it had been 

 observed that different beef hearts produced antigens of different sensitiveness. 

 This led to the development of methods to correct such differences and to bring all 

 antigens to a uniform scale of sensitiveness. As a result, a practical method has 

 been developed which is highly specific for syphilis, and, in addition, special pro- 

 cedures have been devised which give further assistance in diagnosis and treatment. 



PRECIPITATION TESTS PROPOSED BY OTHER WORKERS' 



Michaelis was the first to observe precipitates on mixing syphilitic serum with 

 antigen which consisted of a watery extract of syphilitic liver. This antigen was 

 similar to that employed by Wassermann, Neisser, and Bruck in the development of 

 the Wassermann test. Soon Landsteiner, Miiller, and Potzel, also Levaditi and Maria, 

 showed that alcoholic extracts of syphilitic as well as of normal organs might be used 

 as antigens in the Wassermann test. Jacobstahl announced a precipitation method 

 in which an alcoholic extract of syphilitic liver was employed as an antigen and the 

 precipitates were read by darkfield illumination. This author suggested the probable 

 identity of complement-fixing and precipitin substances in syphilis. Precipitation 

 methods by Bruck and Hidaka, Hecht, Meinicke, and Sachs and Georgi followed. 



The original Meinicke test was a combined "water" and "salt-solution" method. 

 In the water method, distilled water was added to a given serum-antigen combina- 

 tion, producing precipitates in negative sera and turbidity in positive ones. In the 

 salt-solution method, 2.5 per cent sodium chloride solution was added to a serum- 

 antigen-distilled water combination, producing precipitates only in positive sera. 

 Meinicke's "third modification," which he claimed to be a combination of the water 

 and salt-solution method, was published in 1918. During the same year Sachs and 

 Georgi published the method which bears their name. The antigen was an alcoholic 

 extract of wet heart muscle reinforced with cholesterol. The serum was diluted i : 10 

 with normal saline before its use in the test. The final results in this method and in 

 Meinicke's third modification were read after twenty-four hours' incubation. 



In 1922 Meinicke proposed a turbidity reaction involving the use of a cholesterol- 

 ized antigen containing balsam. Later he devised a similar method with a cholesterol- 

 free antigen, and, more recently, a micro-reaction. Sachs and Klopstock also proposed 

 a method which shortens the incubation period by adding mastic to the extract anti- 

 gen and shaking the ingredients. For details of technique of these reactions as well as 

 for the precipitation methods proposed by Vernes, Dryer and Ward, Hecht, Dold, 

 Bruck, Wang, and others, the reader is referred to the original publications, 



OBSERVATIONS ON PRECIPITATION IN SYPHILIS 

 OPTIMUM CONCENTRATION OF THE INGREDIENTS 



As already indicated, the writer's first observation in connection with the pre- 

 cipitation phenomenon in syphilis was that concentration of the reagents that enter 



' For references and more complete summary, cf. Bruck, C: Serodiagnose der Syphilis. Berlin: 

 J. Springer, 1924; Kahn, R. L.: Serum Diagnosis of Syphilis by Precipitation. Baltimore: Williams & 

 Wilkins Co., 1925. 



