[Connections of field 17 of the visual cortex with the mammillary nuclei in cats].

Using optical techniques by Nauta--Gygax, Wiitanen and Eager, degenerating nerve fibres and terminals were demonstrated to be present in the hypothalamic mammillary nuclei 9 days after a part of field 17 of the brain cortex was extirpated. Electron microscopic examination revealed different changes in large and small terminals of the boutons 5, 7 and 11 days after similar operations. The data represented demonstrate direct monosynaptic bilateral connections in field 17 of the optic cortex with the hypothalamic mammillary nuclei in cats. They are realized by fine fibrillae terminating mainly in large terminal boutons which form synapses on big and small dendritic branches. Thus, there is a structural base for the immediate influence of the optic cortex on the posterior hypothalamus.