Movement of palatine shelves in untreated and teratogen‐treated mouse embryos

Movement of palatine shelves in living mouse embryos after tongue displacement was evaluated by direct observation and by re‐examination of the shelves after freezing or submersion in fixative. Effect on shelf function of suspending the embryos in saline or plasma was compared with manipulations in air. Measurements were made of head dimensions and residual space between the palatine shelves in embryos fixed in the cornua or after experimental manipulation. All methods of evaluating palatine shelf behavior indicated movement toward the midline by the anterior portions of the shelves after tongue displacement. Experiments with complete detachment of the tongue demonstrated that the tongue contributes to the flattening of the shelves into a horizontal plane by exerting pressure from below. The same techniques applied to embryos treated with cortisone, vitamin A and x‐ray demonstrated reduced movement of palatine shelves toward the midline when compared with untreated embryos. The reduction was greatest with x‐irradiation and least with hypervitaminosis A.