[Formation of a system of exogenous tangential fibers in layer I of the cerebral cortex in the ontogeny of the dog].

During pre- and postnatal periods, development of nuclear projections of the diencephalon into the cortical layer I has been studied in dogs by means of silver nitrate impregnation after Cajal. It has been stated that after the 5th week of the intrauterine development a great number of fibres from the diencephalon, through the germ of the cortical lamina, begin penetrating into the layer 1 within the areas of the paleocortex, the island, the subicular field of the archicotex, the presubicular and entorhinal cortex. A little less fibres have been revealed in the sensomotor and temporoentorhinal areas on the convex surface of the frontal lobe and on the medial surface of the occipital lobe. At the places of their penetrating into the cortical layer 1, by the time of birth, the fibres have sprouted up thickness of the whole area of the hemisphere.