II THE POSTERIOR LOBES 135 



In many of these creatures, such as the Sairniri 

 (Chrysolhrix), the cerebral lobes overlap and 

 extend much further behind the cerebellum, in 

 proportion, than they do in man (Fig. 17) and it 

 is quite certain that, in all, the cerebellum is com- 

 pletely covered behind, by well developed posterior 

 lobes. The fact can be verified by every one who 

 possesses the skull of any old or new world 

 monkey. For, inasmuch as the brain in all mam- 

 mals completely fills the cranial cavity, it is 

 obvious that a cast of the interior of the skull 

 will reproduce the general form of the brain, at any 

 rate with such minute and, for the present.purpose, 

 utterly unimportant differences as may result from 

 the absence of the enveloping membranes of the 

 brain in the dry skull. But if such a cast be made 

 in plaster, and compared with .a similar cast of the 

 interior of a human skull, it will be obvious that 

 the cast of the cerebral chamber, representing the 

 cerebrum of the ape, as completely covers over and 

 overlaps the cast of the cerebellar chamber, repre- 

 senting the cerebellum, as it does in the man 

 (Fig. 21). A careless observer, forgetting that a 

 soft structure like the brain loses its proper shape 

 the moment it is taken out of the skull, may 

 indeed mistake the uncovered condition of the 

 cerebellum of an extracted and distorted brain for 

 the natural relations of the parts ; but his error 

 must become patent even to himself if he try to 

 replace the brain within the cranial chamber. To 



