The term area 19 of Brodmann (guenon) refers to a subdivision of the cerebral cortex of the guenon defined on the basis of cytoarchitecture. It is cytoarchitecturally homologous to the area 19 of Brodmann (human) ( Brodmann-1909 ). Distinctive features ( Brodmann-1905 ): Compared to area 18 of Brodmann (guenon), the pyramidal cells of sublayer 3b of the external pyramidal layer (III) are not as densely distributed, the layer is not as narrow, and its boundary with the internal granular layer (IV) is not as distinct; the cells in sublayer 3b are concentrated at its outer boundary leaving a narrow clear zone with no large pyramidal cells adjacent to layer IV; the granule cells of layer IV are less densely distributed and are intermixed with larger polymorphic cells so that, while the layer is still quite dark and prominent, it is somewhat widened and not as self-contained; the internal pyramidal layer (V) is characterized by large pyramidal ganglion cells, most in small groups, a pattern not seen in area 18; the cells in the multiform layer (VI) are clearly larger than in area 18; overall area 19 is somewhat thicker and less densely populated than area 18.