310 ORIGINAL ARTICLES. 



sure, instead of at its summit, as in man and the Orang, I feel dis- 

 posed, 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 Chimpan- 

 zee's brains, all at the same point ; and if Dr. Eolleston's supposition 

 be correct (1. 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 rela- 

 tive superiority of the Chimpanzee's and Orang's brain, our specimen, 

 on the whole, is in favour of the claims of the latter. The Chim- 

 panzee'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 uni- 

 form and more symmetrical than the rest, and these very same con- 

 volutions 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 Eoville'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 



