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Mast cells in the chick embryo choroid plexuses.

The existence of mast cells in the choroid plexuses of the chick embryo lateral ventricles has been investigated by a microscopical and ultrastructural study carried out from the 9th incubation day to hatching. These cells have been seen within the perivascular connective of the choroid plexuses in the later stages of their embryonic development and are morphologically similar to those present in the connective stroma of other organs. A role of these cells in the regulation of the choroid vessel permeability as well as of the exchanges between plasma and cerebrospinal fluid (and viceversa) is suggested.