332 Scientific Proceedings (130) 



Although the final results are read after overnight incubation, 

 it will be found that the strongly positive serums either react 

 spontaneously after adding antigen or show the presence of 

 definite precipitates after several hours incubation. From fifteen 

 to seventeen hours is more than ample for incubation. Pro- 

 longed incubation beyond these hours is to be avoided. An ele- 

 ment which will give false weak reactions particularly after pro- 

 longed incubation is the employment of tubes which will permit 

 considerable evaporation of the serum during the incubation 

 period. Agglutination tubes having an inner diameter of about 

 0.8 cm. will be found to give best results. 



We have not found it necessary to employ sterile salt solution. 

 Chemically clean but not sterile precautions are required in this 

 test. 



Status of Improved Procedure. 



The combination of the two steps outlined, together with 

 proper negative and positive controls, forms in our experience a 

 more dependable test than that originally described. 



160 (2120) 



Dilution of antigen for Wassermann test. 

 By R. L. KAHN. 



[From the Bureau of Laboratories, Michigan Department of 

 Health, Lansing, Michigan.] 



In the previous communication, the author described a method 

 for preparing antigen for the Kahn Precipitation Test and 

 showed (Procedure II) that the sediment formed on mixing and 

 centrifuging equal quantities of antigen and salt solution may be 

 redissolved in salt solution and employed in the above test for 

 syphilis. The question came up whether the same sediment taken 

 up in salt solution may not be used as an antigen in the Wasser- 

 mann test and the following experiments were carried out 

 accordingly. 



