Abstract
Summary Yolk sacs infected with trachoma, inclusion conjunctivitis, lymphogranuloma venereum, psittacosis 6BC or meningopneumonitis were extracted repeatedly with fluorocarbon. The resulting suspension of elementary bodies contained little egg material. The particles were distinct, and reacted with strain-specific rabbit antisera as measured by indirect fluorescence. The homologous antiserum usually yielded the highest titer; heterologous antisera showed equal, intermediate or no reaction; antisera to normal yolk sac were negative. Psittacosis 6BC and meningopneumonitis could be separated easily from TRIG agents. LGV, an IC isolate, and BOUR, a trachoma isolate, showed much cross-reaction, but BOUR could be differentiated regularly from another trachoma isolate (ASGH).