sure, instead of at its summit, as in man and the Orang, I feel disposed, from a comparison of the parts in the Chimpanzee with the human brain, to consider this, so-called, unusually broad and forward origin of the bent convolution, 6, as in reality the homologue of the so-named "lobule of the superior marginal convolution," which is regarded by Gratiolet as peculiar to man: on such a supposition the bent convolution would arise in man's, the Orang's, and the Chimpanzee's brains, all at the same point; and if Dr. Rolleston's supposition be correct (l. c. p. 212), all these would possess a "marginal lobule," which, however, like the connecting convolutions, would be far more highly developed in man. On the interesting question of the relative superiority of the Chimpanzee's and Orang's brain, our specimen, on the whole, is in favour of the claims of the latter. The Chimpanzee's convolutions are more symmetrical. But the subject of the cerebral convolutions is too prolific a one to be discussed at length here.
It is utterly impossible to follow M. Gratiolet's analysis without coinciding with him, entirely, as to the correspondences of his essential subdivisions of the cerebral masses. One general fact he illustrates very fully, viz., that uniformity and symmetry of arrangement are marks, so far as they go, of inferiority of cerebral development. Now, this is not merely true in regard to different species of animals, or different individuals of the same species, but in any one brain, even in the human brain, there are certain convolutions which are more uniform and more symmetrical than the rest, and these very same convolutions vary less in different, though allied, groups of animals. The convolutions which are thus characterized in the Quadrumana and in Man, are those which belong to Foville's first order, those which form as it were the extreme rim or circumference of each cerebral hemisphere, viz., the convolution of the corpus callosum, on the inner side, and the convolution which surrounds the Sylvian fissure, on the outer side. The various fissures, or sulci, which separate these primary convolutions from those which occur next to them, also partake of the same comparative simplicity; whilst the further one recedes from them, on to the external surface of the hemisphere between them, the greater complexity and variety one meets with, both in the convolutions and in their intervening sulci. In accordance with this rule, the under surface and the internal surface, of the hemispheres are more simple than their external, or convex, surface; and hence, whilst the detection of corresponding parts becomes more and more difficult in certain portions of the latter region, as we ascend in the scale of organisation; in the two former the necessary landmarks continue very clearly recognisable. This is certainly the case in regard to the internal and under surfaces of the posterior part of the hemispheres; and if any one will examine the series of basal views of Quadrumanous brains in Gratiolet's work, in which the cerebellum has been removed, so as to show the under surface of the back part of the hemispheres, he will be able to trace in one of the
