[Quantitative architectonic variations in the visual cortex of mice following varying light exposure of the visual organ].

Quantitative - architectural investigations were carried through with two experimental groups of white mice. One group was expsed to a source of light day and night, the other group lived under normal light variations. The animals of both groups were already born under the mentioned conditions and killed in etherization after 51 days. After the determination of the brain-weights, which showed smaller quantities for the group living under light day and night, sections of 10 mum were stained according to the NISSL method and the thickness of the cortex was measured. The layers in the area striata were examined with regard to possible differences. But in this connection no differences between the two groups were to be found. According to the point - method the different coefficients of the cortical layers were determined. The mathematical - statistical analysis with the help of t-test showed significantly bigger coefficients with the latter group (living under light day and night). These coefficients correspond to a smaller part of volume of neurons or their components in a defined volume. This way it was proved that changed light conditions result in changes of the microscopical structure of the area striata. At the same time significant changes occur in the nucleus-plasma-relation of the various layers. These make us recognize the functional adaptations to the changed environmental influences.