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[Postnatal changes in the regions bordering the ventricle in the telencephalon of the cat].

In frontal, sagittal and horizontal series of sections through the telencephalon of 15 cats the postnatal development of the periventricular regions has been examined. Structure, distribution and postnatal changes of the matrix, of a zone of undifferentiated cells near the ventricle, and of packets of undifferentiated cells, so-called cell nests, are described in detail. In cats aged from postnatal day 1 to 84, the following findings have been obtained: 1. At term, almost the entire lateral wall of the lateral ventricle is lined by a matrix layer. After birth, it undergoes involution at rates varying at different sites.--In the medial wall of the lateral ventricle, a matrix occurs only in cats aged 1--5 days in a region rostral to the lamina terminalis. 2. In newborn and young cats a less compact layer of undifferentiated cells with dark nuclei was found to abut on the matrix. Near the album, this layer is characterized by a cell-rich outer zone, called the cell wall. The cell content of the layer of undifferentiated cells increases up to the 11th to 16th postnatal day. Later on it decreases. 3. The cell nests consist of groups of closely packed cells with small nuclei and scanty cytoplasm. The cell nests may be round, ellipsoid, elongated or irregular in form. They are often localized in direct contact to blood vessels. The cell nests occur in certain predilection areas, particularly in the region of the frontal white matter and in the centrum semiovale. In most regions of the cerebral cortex where cell nests occur, their number increases up to the 11th to 16th postnatal day and later decreases. At the 40th day most of the cell nests have disappeared. 4. Within the matrix and the layer of undifferentiated cells near the ventricle, and also within the cell nests, cell divisions and cell deaths occur. The structural changes described are discussed with respect to postnatal development of the cerebral hemispheres.