Tracheal ring sections were obtained from 19- to 20-day-old chicken embryos of the specific pathogen-free layer type. They were cultured in roller tubes containing Eagle's basal medium with addition of 200 U/ml of penicillin G, 0.05 M N-2-hydroxyethyl-piperazin-N'-2-ethanesulfonic acid, and 1% porcine serum. The motility of cilia was preserved in the best conditions for 7 to 11 days in the medium, and for a few days or less in the serum-depleted medium. Mycoplasma synoviae strains F2-C AS and WVU 1853 and M. gallisepticum strain S6 were hardly or not grown in the medium without tracheal organs. In the tracheal organ culture, however, growth of microorganisms took place independent of the presence of porcine serum. The cilia-stopping effect of the M. synoviae strains in the cultured tracheal tissue was milder than that of the M. gallisepticum strain tested. Mycoplasmas were found to have been grown and attached to cilia and epithelial cells when examined in electron micrographs and fluorescent antibody micrographs. Relationship between the virulence and cilia-stopping effect and the cytopathogenicity of the mycoplasmas are discussed.
