Biological effect of the unsaturated fatty acid fraction from the X-ray irradiated rabbit liver (OX) on HeLa cells has been observed in vitro comparing with the effect displayed on the same strain cells by the unsaturated fatty acid fraction from the non-irradiated rabbits, which is extracted by the same method as in OX, The observations have proven that OX is a powerful cytotoxin in a concentration of 0.05-0.025 per cent and induces a severe cell degeneration and cell death, resulting in a marked arrest in the growth of the cells. The similar effect has been observed by unsaturated fatty acid fraction from the nonirradiated rabbits, but the effect was much less comparing to that of OX. Possible mechanism of the cell damage by OX has been discussed.</p
