502 



THE SENSORIAL FUNCTIONS. 



produce, likewise, even in birds, transverse furrows 

 on the surface ; and from the interposition of a 

 substance of a grey colour between the laminae of 

 the white medullary matter, a section of the cere- 

 bellum presents the curious appearance (seen in 

 Fig. 459), denominated, from its fancied resem- 

 blance to a tree, the Arbor Vitte. 



Thus far we have followed an obvious gradation 

 in the developement and concentration of the dif- 

 ferent parts of the brain ; but on arriving at Man, 

 the continuity of the series is suddenly disturbed 

 by the great expansion of the hemispheres, (Fig. 

 461), which, compared with those of quadrupeds. 



bear no sort of proportion to the rest of the nervous 

 system. Both Aristotle and Pliny have asserted 

 that the absolute, as well as the comparative size 

 of the human brain is greater than in any other 

 known animal ; exceptions, however, occur in the 

 case of the Elephant, and also in that of the Whale, 

 whose brains are certainly of greater absolute bulk 



