PRECIPITIN TESTS IN SYPHILIS 461 



moisture from the air after preparation. Thus fresh cholesterol 

 reagents should be prepared frequently. The sensitivity of the 

 emulsion is more dependent upon the cholesterol content than on 

 the antigen content. The antigen extract can be varied over a 

 range of 400 per cent while the cholesterol content has a range of 

 60 per cent in satisfactory emulsions. (Kline, 1931.) 



Dirty glassware and slides may result in spontaneous aggluti- 

 nation. 



Principle of the Meinicke Reaction. — In the Meinieke reaction 

 the reagin in the syphilitic serum disturbs the colloidal balance of 

 beef (or horse*) heart lipoids dispersed in three and one-half per 

 cent sodium chloride solution. The result is a microscopic to a 

 macroscopic flocculation, depending upon which of the several 

 modifications of Meinicke is followed. Negative .serum, lacking 

 reagin, does not change its uniform turbidity. The precipitate 

 is composed of a lipoidal fraction and balsam of Tolu filmed with 

 reagin and a denatured g]o])ulin fraction. This reaction, accord- 

 ing to Meinicke, is a ty])ical lipoid-binding reaction. It is equiva- 

 lent to agglutination or complement fixation in specificity ; and, 

 with an appropriate antigen, can be applied to the diagnosis of 

 any infectious disease or differentiation of a specific protein. It 

 is Meinicke 's conception that the antigen-antibody complex binds 

 lipoids (1926). 



Specificity.— Meinicke (1917, 1918, 1926-27), Jantzen (1921) 

 and Epstein and Paul (1921) claim equal specificity with the 

 complement fixation methods in general use. They believe this 

 flocculation method is slightly more sensitive in general syphilis 

 and decidedly more sensitive for the serological diagnosis of lues 

 congenita. 



Antigen. — The antigen is an ether-insoluble, alcohol-soluble 

 extract of beef heart. To this extract is added 1.4 per cent balsam 

 of Tolu and 0.01 per cent Victoria blue. The antigen is titrated 

 with weakly positive and negative serum by an arbitrary method. 

 (Meinicke, 1934.) 



Mixing of Antigen. — Reagents in the test are antigen extract 

 and three and one-half per cent sodium chloride solution. A 



*ln the earlier modification of the Meinicke reaction tlie antigen wa.=i prepared 

 from horse heart lipoids, but in his recent modification (1934) he uses beef 

 heart lipoids. 



