[Cultivation of F. tularensis in developing chick embryos]

In cultivation of the causative agent of tularemia in the organism of chick embryos (8-10 days of incubation) it was found that the virulent strains multiplied intensively in the yolk sacs causing the death of the embryos on the 3rd-4th day after the infection; as to the virulent strains-they were only preserved in the embryos. The period of death of the embryos and the accumulation of bacteria depended on the strain virulence. No differences in the anatomical structure of the cells belonging to the virulent and avirulent strains could be found.