The principles of teratology: are they still true?

James Wilson originally proposed a set of "Principles of Teratology" in 1959, the year before he helped to found the Teratology Society. By 1977, when these Principles were presented in a more definitive form in Wilson and Fraser's Handbook of Teratology, they had become a standard formulation of the basic tenets of the field. Wilson's Principles have continued to guide scientific research in teratology, and they are widely used in teaching. Recent advances in our knowledge of the molecular and cellular bases of embryogenesis serve only to provide a deeper understanding of the fundamental developmental mechanisms that underlie Wilson's Principles of Teratology.