Precipitation Reaction for Syphilis. 



of the amount filtered off. The second extraction is carried out 

 for about a month in the ice box. Both filtrates may be used as 

 antigens. 



Add rapidly three parts of salt solution to I part of antigen. 

 The mixture should be opalescent and but slightly milky. No 

 precipitate should form after standing over night at room temper- 

 ature. Antigens conforming with these requirements have been 

 kept for 2 weeks without any apparent change in antigenic prop- 

 erties. 



Add o.i c.c. of antigen to 0.3 c.c. of clear inactivated serum 

 and incubate in the water bath. The strongly positive sera show 

 immediate clouding and, withir 5 min., visible precipitation. For 

 uniformity, the tests are read after 1 hour and 3 hours incubation. 

 Those showing marked precipitation at the end of 1 hour are 

 considered strongly positive; marked precipitation at the end of 

 3 hours are considered positive; weak precipitation, weak positive 

 and questionable, doubtful positive. 



Of 1,119 comparative tests carried out with the precipitation 

 and Wassermann reactions as performed in this laboratory, 98 

 per cent, showed agreement. It is hoped that this test will form 

 an important supplement to the Wassermann test. 



84 (1831) 



A simple quantitative precipitation reaction for syphilis — micro 



procedure. 



By R. L. KAHN. 



[From Bureau of Laboratories, Michigan Department 

 of Health, Lansing, Mich.} 



The precipitation reaction presented in the preceding paper 

 may be employed also as a microscopic procedure. Prepare 

 hanging drop preparations in the usual manner by mixing a small 

 drop of serum with the same amount of antigen. Read results 

 after 1 and 3 hours incubation at 37. 5 0 C. Those sera showing 

 precipitation give the appearance of clumps of minute globules, 

 while the negative sera appear homogeneous. This procedure, 

 however, requires much experience and care in its manipulation. 



The following micro-method is, in our experience, far simpler 

 to execute and is recommended: Pipette 0.03 c.c. quantities of 



