Myoneural maturation and function of the foetal rat tongue at the time of secondary palate closure

Most authors consider the tongue active in secondary palate closure; some consider it passive; but specific information is wanting. We therefore studied the Holtzman rat foetal tongue by direct observation, histologically, under direct and neural stimulation, and when curarized. The tongue has differentiated into myoblasts (longitudinalis and verticalis) and young fibres (transversus, hyoglossus, genioglossus) four hours prior to closure. At this age it responds to both direct electrical and XII nerve nucleus stimulation. Curarization at high levels neither prevents closure nor abolishes foetal reflexes. The tongue myoneural apparatus is functional at palate closure.