The growth of the Reiter strain of Treponema pallidum in the chick embryo.

Attempts to cultivate the virulent Treponema pallidum in the developing hen's egg have yielded no conclusive proof that reproduction has occurred in the embryo, but indicate rather that the spirochetes have merely survived for the periods involved (Calloway and Sharp, 1941). Wile and Snow (1941) and Wile and Johnson (1944) have shown approximately 25 per cent of inoculated embryos to be infectious for rabbits after 8 days' incubation, but the lack of microscopically demonstrable spirochetes at that time, however, led them to suggest that the organism survived in an ultramicroscopic phase. Since positive evidence for an ultramicroscopic form is lacking, the failure of the virulent spirochetes to grow in chick embryos may be due to either an unsuitable host or the lack of anaerobiosis in the embryo. The fact that the so-called Reiter strain of Treponema pallidum is grown easily on a lifeless medium under anaerobic conditions suggested an approach to the question of the role of anaerobiosis in the embryonic culture. In the following experiments the influence of the presence or absence of developing tissue and anaerobiosis on the growth of this organism in chick embryos was studied.