84 ORIGINAL AUTICLES. 



the internal structure of the brain, the large size of the optic thalami in 

 relation to the corpora striata, and the total absence of a posterior cornu 

 to the lateral ventricle* — are all characters which are perfectly obvious, 

 and which separate the brain of the Lemur as completely from that of 

 Pithecus or Troglodytes, as from that of man. 



The description of the brain of Stenops tardigradus, by Yrolik, tells 

 the same story even more strikingly ; and the brains of Perodicticus and 

 other Prosimiae, exhibited in the Hunterian Museum, fully bear out the 

 conclusion, that the vast differences noted obtain throughout the Prosi- 

 mian division of the Quadrumana. 



M. Gratiolet, in fact, has been so struck by the immense discrepancy 

 between the Simiae and Prosimiae in cerebral structure, that he proposes 

 to consider the latter as forming a part of the order Insectivora. In this 

 view he is at variance with all the other zoologists ; but, in order to meet 

 all possible objections, I will, for the moment, suppose that he is right, 

 and that the order Quadrumana should be restricted to the Simiae. Even 

 on this supposition, the force of my argument remains unchanged ; for 

 the brains of the lower true apes and monkeys differ far more widely 

 from the brain of the orang than the brain of the orang differs from that 

 of man. Not only do they differ from the orang (and to a greater de- 

 gree) in most of those respects in which the orang differs from man, but 

 they present the absolute distinction, that while the orang, like man, 

 has two corpora candicantia, the lower apes, like the other Mammalia, 

 have only one. 



In respect of their cerebral characters, therefore, I hold it to be de- 

 monstrable that the Quadrumana differ less from man than they do from 

 one another; and that, hence, the separation of Homo and Pithecus in 

 distinct sub-classes, while Pithecus and Cynocephalus are retained in 

 one order, is utterly inconsistent with the principle of any classification 

 of the Mammalia by cerebral characters. 



On a future occasion I propose to take up the question, whether, on 

 other grounds, there is any reason for departing from the Linnean view, 

 that man is to be regarded as a genus of the same order as that which 

 contains the Quadrumana. 



* " Cornu posterius in Simiis et Phocis brevissimum et vix conspicuum est : in ce- 

 teris mammalibus plane desideratur."— Icones, p. 54. 



