Postnatal growth of the dorsal lateral geniculate nucleus of the cat.

The postnatal growth of the dorsal part of the lateral geniculate nucleus (LGNd) is studied in paraffin sections through the brains of 32 cats of known age. The changes in shape and position of the LGNd are described and it is shown that its volume increases from about 3.4 mm3 at birth to about 26.4 mm3 in the adult cat. When this value is corrected for shrinkage, the volume of the LGNd in the adult cat turns out to be about 44 mm3. The detailed measurements reveal that during the second and third week of postnatal life there is a particularly steep increase in volume and that the final values are already reached at around the 40th day. Concomitant with the increase in volume there is a decrease of the number of cells per unit volume of grey matter. In the binocular segment of lamina A the number of cells decreases from about 470 per (0.1 mm)3 at birth to between 95 and 130 per (0.1 mm)3 in the adult cat. Separate measurements of nerve cells and neuroglial cells indicate that the absolute number of nerve cells remains fairly constant during postnatal life, whereas between the second and sixth week a great number of neuroglial cells are newly formed.