Differences in the size of the palatal processes in mouse embryos with cleft palate induced in two critical periods.

Using planimetric measurements of projections of the space between the palatal processes of ICR-Velaz mouse embryos, we indirectly demonstrated that the pre-horizontalization size of the palatal processes after the i.m. administration of 7.5 mg cortsone acetate on the 12th day of gestation was smaller than in the controls. After horizontalization, the inadequate palatal processes were unable to meet in the midline as they do in the majority of normal embryos. The administration of 0.5 mg 6-amino-nicotinamide on the 14th day of gestation did not significantly affect the size of the palatal processes.