Prof. Owen on the Cerebral Characters of Man and the Ape. 457 



My own dissections of the brains of the Chimpanzee, and Orang 

 utan, and of a partially decomposed one of the Gorilla, have 

 assured me of the accuracy of the Dutch anatomists' figures, as 

 rightly and truly representing the degree to which the brain in 

 the Ape approaches in size and structure to that in Man ; save 

 that, in the Gorilla, in connexion with its greater proportional 

 muscular development, the proportional size of the cerebellum is 

 larger than in the Chimpanzee and Orang ; and in that respect 

 both the latter Apes seem to approach nearer to Man. 



But the difference, as compared with the Negro, is so much 

 greater than is that observable between any two steps in the 

 descending series from the Chimpanzee to the Lemur — or, in 

 other words, the rise in cerebral development is so great and 

 sudden in the Negro, especially when the bulk of Man's body is 

 considered*, that it seems to me to constitute one and the most 

 important of the differential structural characters between the 

 Human and Ape kincls. 



In the brief definitions used in systematic zoology for groups 

 characterized on such differences, the meaning of terms must be 

 defined ; and this I was careful to do in my Paper on the pri- 

 mary distribution of Mammals according to cerebral characters f. 

 I had previously, with other anatomists, used the term ' posterior 

 lobe' of the cerebral hemisphere in a somewhat vague sense; 

 knowing, as Cruvelhier, Todd, and others have stated, that there 

 was no natural boundary marking out a posterior lobe from the 

 so-called middle lobe in the human brain. To make my meaning 

 clear, when it became especially requisite to do so, I therefore 

 proposed a definition from internal structure and relative posi- 

 tion, and signified the ' posterior lobe ' as that " which covered 

 the posterior third of the cerebellum and extended beyond it." 

 The accepted definitions in Human Anatomy, of the ' posterior 

 cornu ' of the lateral ventricle and its eminence the ' hippocam- 

 pus minor,' were so precise and determinate, that propositions re- 

 garding them could not, I thought, be mistaken. As it seems, 

 however, that they have been, I here quote from a late and de- 

 servedly esteemed compendium of descriptive Anthropotomy J : 

 " The ' posterior cornu,' or digital cavity, curves backwards into 

 the substance of the posterior lobe, its direction being backwards, 

 outwards, and then inwards. On its floor is seen a longitudinal 

 eminence which corresponds with a deep sulcus between two 

 convolutions : this is called the ' hippocampus minor ' " (p. 463). 



* From known physiological necessity, the brain is relatively large in 

 immature and small warm-blooded Vertebrates, 

 t Proceedings of the Linnsean Society, 1857. 

 X Anatomy, Descriptive and Surgical, by Henry Gray, F.R.S. 8vo, 1868. 



Ann. ^ Mag. N. Hist. Ser. 3. Vol. vii. 30 



