SERUM DIAGNOSIS OF SYPHILIS. 167 



a reaction is not sufficient. Not before an absolutely negative reaction 

 has been attained should specific therapy cease. 



Several authorities consider only such tests as positive where there is complete absence 

 of hemolysis. This principle is proven as incorrect by their own statistics; a great 

 number of their surely syphilitic cases give a negative reaction. 



If the third tube (serum control) does not hemolyse, the test can neither be considered 

 as positive nor negative. Very frequently the third tube of very strongly positive cases 

 will hemolyse very much more slowly than negative cases; these tests must therefore 

 remain in the incubator for a longer period than the negative or weakly positive ones [ed]. 

 and until the serum tube is completely hemolysed. 



b. Modifications of Wassermanrts Technique. 



On account of the somewhat complex technique of the reactions, numer- 

 ous attempts have been made to simplify the test in one way or another. 

 The greatest difficulty lay in the preparation of a suitable antigen. From 

 the sundry modifications and improvements made in this respect, perhaps 

 the most important was announced simultaneously by Landsteiner, Muller 

 and Potzl, and Forges and Meier. 



They showed that by alcoholic extraction of luetic and even normal 

 organs of human beings and lower animals, substances were obtained 

 which could be used as a substitute for the aqueous syphilitic antigen. The 

 belief therefore arose that the active agents in the luetic extract belong to the 

 class of lipoids, and Forges and Meier endeavored to isolate them from the 

 serum. Thereupon it became evident that lecithin could replace the antigen, 

 but only up to a certain point. Further study by H. Sachs lead to the 

 adoption of entire formulae for artificial antigens. 



The new principle disclosed by these discoveries lead to many modifications in the 

 preparation of the antigen, the main advantage of which consisted in bringing the reaction 

 into more general use and application. The previous necessity of making an extract 

 from the liver of a luetic fetus somewhat limited this. The Wassermann reaction became 

 in a short period of time much more popular, although one could not adhere to it with the 

 same idea of specificity as before. 



Other changes in the reaction, referred to the serum for examination. 

 H. Sachs demonstrated that the inactivation at 56 C. destroyed a great part 

 of luetic the "reagine." The dispensation of the latter was therefore recom- 

 mended. It soon became evident, however, that by so doing, a great number 

 of normal and non-luetic pathological sera gave a positive reaction. // is 

 best therefore that this modification should by all means be discarded. 



As all fresh sera contain complement, the addition of guinea-pig's 

 complement seemed superfluous if the serum for examination is employed 

 in an active form. The following combination was therefore proposed: 



1. Luetic extract or one of its substitutes. 



2. Active luetic serum (contains luetic "reagine" + complement). One hour in 

 incubator. 



