Abstract
Summary
The effects of cortisone and pituitary growth hormone on embryonal tissues have been studied in chick embryos at time periods varying between 18 and 72 hours of incubation. No effects were noted at 18 and 30 hours. Mitotic counts have demonstrated the basic mitotic suppressing effect of cortisone in mesoderm at 60 hours and in ectoderm and mesoderm at 72 hours, although there were no changes in endoderm. An increase in mitotic activity was observed in embryos receiving growth hormone in the ectoderm and mesoderm at 60 hours, but not at 72 hours. However, an increase in cell density was observed in these embryonal tissues at 72 hours of incubation. Endoderm was also refractory to this hormone.
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