A Rapid Method for the Macroscopic Agglutination Test

While using the Kahn Precipitation Test and especially the quantitative procedure, the possibility suggested itself of applying similar principles of concentration to the demonstration of agglu-tinins. If an immediate agglutination reaction could be obtained by an accurate, quantitative method, the advantages would at once be apparent. Working along these lines, a rapid method for the macroscopic agglutination test has been developed. The method involves concentration of the antigen, the use of small amounts of both antigen and serum, together with thorough mixing. Results read within five minutes after adding serum to suspension correspond to those obtained by a standard method requiring from eighteen to twenty-four hours. EXPERIMENTAL The first experiments were made with 0.15 cc. of varying dilu-tions of an antityphoid serum (1:20 to 1:1000) and 0.05 cc. of a very heavy killed suspension of B. typhosus. These were mixed in small test tubes (75 by 13 mm.), shaken vigorously for two min-utes, 0.5 cc. saline added and read-thus following the quantities and mechanics of the Kahn Precipitation Test. There was complete agglutination throughout, with no clump-ing in the control (0.15 cc. saline plus 0.05 cc. suspension). This experiment was repeated with B. typhosus and B. paratyphosu8