A Comparative Study of the Actions of Six Tetracyclines on the Development of the Chick Embryo

The series of studies of Bevelander and his colleagues, conveniently summarized in his letter (1963), together with the observations collected by Shils (1962), has focused attention on the potentially toxic nature of the tetracyclines particularly in embryos and in develop- ing tissues. It was felt that a comparison should be made between older and newer, more soluble tetracyclines to try to discover whether alteration in the molecule had increased toxicity and whether any teratogenic effects could be detected.