Observation of palatine shelves in living rabbit embryos

Rabbit embryos were removed from the uterus just prior to the time of palate closure, submerged in saline, and observed for evidence of shelf movement. When the tongue was displaced from between the palatine shelves the latter were not seen to move. After fixation and sectioning, the angle of the shelves to the sagittal plane was measured. This angle progressively approached that of embryos fixed in utero prior to shelf transposition when the tongue, or both tongue and lower jaw, were removed during manipulation in vivo. When the tongue was released it either returned to a position between the shelves or remained ventral to the shelves and forced them into a horizontal position. Thus there was no evidence of a pronounced intrinsic shelf force in rabbit embryos under the conditions of this experiment.