Brain of the Orangutan
Brain of the Orangoutang, showing arrangement of the convolutions. Sy, fissure of Sylvius; R, fissure of Rolando; E P, external perpendicular fissure; Olf, olfactory lobe; Cb, cerebellum; PV, pons Varolii; MO, medulla oblongata. As contrasted with the human brain, the frontal lobe is short and small relatively, the fissure of Sylvius is oblique, the temporo-sphenoidal lobe very prominent, and the external perpendicular fissure very well marked.
Baker, W. Morrant & Harris, Vincent Dormer Kirkes' Hand-book of Physiology, 13th ed. (Philadelphia: P. Blakiston's Son & Co., 1892) 643