Page:Natural History Review (1861).djvu/317

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Ratios between the dimensions of different parts of the Encephalon, in Man and in the Chimpanzee.

N.B.—All the above measurements, except those of the medulla, were taken by aid of the intra-cranial casts. They necessarily differ from those taken from the brain itself by various anatomists. Such measurements as relate to internal parts will be given hereafter.

The Fissures, Lobes and Convolutions. The Sylvian fissure, more vertical than in man, even in the preserved Chimpanzee's brain, fig. 4, S, appears still more so in the cast, fig. 3; but in the cast of the human brain it is, also, somewhat more upright than in the preserved specimens, though not so much as in the Ape. The fissure of Rolando, figs. 4, 5, R, is very distinct in the Chimpanzee's brain, passing obliquely forwards from the longitudinal fissure, in a zigzag line, and separating the first ascending convolution, fig. 5,4,4′, from the second ascending convolution 5,5′. The V-shaped figure which the two fissures of Rolando make, where they unite with the longitudinal