II 



THE POSTERIOR LOBES 137 



Natural History Review for July, 1861. The sharper definition 

 of the lower edge of the cast of the cerebral chamber in the 

 Chimpanzee arises from the circumstance that the tentorium 

 remained in that skull and not in the Man's. The cast more 

 accurately represents the brain in the Chimpanzee than in the 

 Man ; and the great backward projection of the posterior lobes 

 of the cerebrum of the ^former, beyond the cerebellum, is 

 conspicuous. 



suppose that the cerebellum of an ape is naturally 

 uncovered behind is a miscomprehension com- 

 parable only to that of one who should imagine 

 that a man's lungs always occupy but a small 

 portion of the thoracic cavity, because they do 

 so when the chest is opened, and their elasticity 

 is no longer neutralized by the pressure of the air. 



And the error is the less excusable, as it must 

 become apparent to every one who examines a 

 section of the skull of any ape above a Lemur, 

 without taking the trouble to make a cast of it. 

 For there is a very marked groove in every such 

 skull, as in the human skull which indicates the 

 line of attachment of what is termed the tentorium 

 a sort of parchment-like shelf, or partition, 

 which, in the recent state, is interposed between 

 the cerebrum and cerebellum, and prevents the 

 former from pressing upon the latter. (See Fig. 17.) 



This groove, therefore, indicates the line of 

 separation between that part of the cranial cavity 

 which contains the cerebrum, and that which 

 contains the cerebellum ; and as the brain exactly 

 fills the cavity of the skull, it is obvious that the 

 relations of these two parts of the cranial cavity 



