SUMMARY
The influence of variation in the concentrations of cardiolipin and lecithin in the preparation of antigen for Meinicke's test has been studied. An antigen containing lecithin and cardiolipin in the proportion of 3 to 1 gave sensitive and specific reactions with positive sera and stable reactions with negative sera. This sensitive antigen gave a some what larger incidence of prozone inhibition (4 plus reactions) than usual; but among 1,782 sera tested with this antigen there was none giving a “biologically false 4 plus reaction. For the purpose of standardization, an antigen containing lecithin and cardiolipin in the proportion of 3 to 1 with adjustment of the total lipid content against that of balsam of Tolu is recommended.