Page:Natural History Review (1861).djvu/325

Rh between the hinder end of the corpus callosum and the internal perpendicular fissure. The widths of the cornua of the lateral ventricle vary according as their sides are held asunder, but they are large cavities. About the same proportionate quantities of corpus striatum and optic thalamus are seen in the anterior cornu and body of the ventricle, as in man. In fig. 5, the thin curved margin of the fornix, with the rounder commencement of the hippocampus major, are seen entering the descending cornu. On the inner side of the floor of the posterior cornu is a convex eminence, the hippocampus minor. Between the bend of the hippocampus major and the hippocampus minor is a triangular eminence, also prolonged into the posterior cornu; this is a small pes accessorius or eminentia collateralis. All the parts to be found in the human posterior cornu are thus represented in the Chimpanzee, in proof of which we may refer to the irrefragable evidence of the photograph, fig. 5. A comparison of the natural parts with Schroeder van der Kolk's and Vrolik's figure, 4, Plate II.,—which is so differently interpreted just now, being equally quoted to show the presence and the absence, in the Quadrumanous brain, of the same parts, viz. the posterior lobes, the posterior cornu, and the hippocampus minor, has compelled me to the conclusion that, although those anatomists have had to dissect a displaced and deformed posterior lobe, and have removed its substance rather freely, still the eminence figured, and marked e, by them, is really a hippocampus minor. To make this clear we may refer to the annexed sketch, fig. A., drawn by myself from nature, in which the parts are shown of their true size.