| Abstract: | The study of the development of of the chondrocranium in chick embryos with unilateral (right-sided) anotia revealed the following main characteristics. 1. The median axes of the chordal and the prechordal part of the cranial base are not in a straight line but show a deviation toward the right side. The angle between the two axes has its vertex in the region of the foramen hypophyseos. 2. The metotic cartilage and the foramina of the IXth and Xth cranial nerves are normal in position. 3. The tectum synoticum develops later and to a lesser extent than normal. 4. Between the basal plate, the metotic cartilage, the occipital arch and the supracapsular cartilage a foramen is formed which, later in development, is closed by outgrowths of the metotic cartilage and the basal plate. 5. The "optic area" shows a practically normal appearance which indicates that the cartilaginous ventral wall of the lagenal capsule is of basal plate origin. 6. The pro-otic process develops practically normal and, hence, is independent of the ear capsule. 7. The quadrate cartilage and the right lower jaw are displaced ventro-posteriorward. The earliest development of the perichondral bones shows some particularities which are closely correlated with the development of the various cartilaginous structures. |
