[A new concept of the normal and pathological development of the primary palate. 1. The normal fate of Hochstetter's epithelial wall].

The following conclusions as to the normal development of the primary palate were drawn from literary and own embryological studies and from morphological evaluations of congenital malformations in this region: 1. The nasal fin or so-called "Epithelmauer" consists of two epithelial layers. It is build, if the epithelial surfaces from the medial and lateral nasal processes touch each other. It represents a masked form of the oro-nasal groove which is also to be found in embryos of sauropsids. Therefore all mammalian embryos have a physiological cleft lip and jaw, which must be removed in order to create a mesenchymal fusion. 2. In its upper part the nasal fin consists of respiratory epithelium (nasal connecting lamina) and in its lower part it consists of oral epithelium (oral connecting lamina). 3. Many findings in the normal embryo and the results of pathological development argue that the cells of the nasal fin are not destroyed by mesenchyme but they persist. 4. Along the differentiation-line the oral epithelium separates gradually from the respiratory epithelium (remaining on the spot). 5. The oral epithelium is moved towards the palate thus permitting the mesenchymal fusion between the adjacent processes of the face. 6. This shifting oral connecting lamina is integrated into the epithelium of the palate.