A Standardized Modification of the Laughlen Test for Syphilis.

The antigen was made thus: to 1 ml. of Kahn antigen was added a "small quantity" of a fat stain (Scharlach R or Sudan 111) and four drops of tinct. benzoini co., B.P. The mixture was warmed in a water-bath at 50' C., and 10 ml. of 1.5 per cent saline, also warmed to 50' C., was added. This pink, milkylooking fluid was "sensitized" by the addition of varying amounts of 9 per cent salt solution. For the test one drop of this sensitized antigen was mixed on a slide with one drop of the serum under examination and gently rocked for 10 minutes; precipitation occurring within this time indicated a positive result. Several modifications of this technique have been described by various workers.