Growth in the Chick Embryo of Strains of Trachoma and Inclusion Blennorrhoea Virus of Differing Virulence

Abstract
The growth in the chick embryo yolk sac of trachoma and inclusion conjunctivitis (TRIC) strains which differ in virulence for the chick embryo was measured in terms of ELD50 inclusion forming units in HeLa cells and total particles. Observed differences in rates of growth are consistent with the assumption that greater virulence depends on a higher rate of multiplication in the chick embryo. All strains were equally labile when heated at 37[degree] in vitro but only the more virulent kill chick embryos at 37[degree].