366 



FUNCTIONS OF THE NERVOUS SYSTEM. 



482. As might be expected, the Cerebrum of Man bears by far the highest 

 proportion ; but this proportion is not so large in the transverse and vertical 

 diameters, as in the antero-posterior ; in fact, in the proportion of the vertical 

 diameter the Cerebrum of Man is equalled by that of the Dolphin, and nearly 

 so in that of the transverse diameter. In the complexity of the convolutions, 

 however, and in the thickness of the grey matter, the Cerebrum of Man 

 far surpasses that of this Cetaceous animal. In these respects the higher 

 Quadrumana present the nearest approach to it; but their brain is much infe- 

 rior in size. In descending the scale of Mammalia, there may be observed a 

 gradual simplification in the general structure of the Cerebrum, depending 

 upon a great diminution in the amount of commissural fibres ; until in the 

 Marsupialia the Brain presents nearly the same condition which it offers in 

 Birds ( 361). These animals manifest a much lower degree of Intelligence 

 than many Birds evidently possess; and it is interesting to remark, that their 

 Cerebral hemispheres are proportionally smaller than those which we find in 

 many Birds: the diminution in their relative size not being counterbalanced 

 (as it is in some other instances) by increased complexity of structure. In 

 the class of Birds, we observe that the Vulture and the Falcon, whose prcda- 

 ceous instincts give them a considerable amount of general energy, are much 

 inferior in the size of their brains to the Insessorial Birds, which are more 

 intelligent; and that of all, there is none in which the brain is so proportion- 

 ably large, as it is in the Parrot tribe, the educability of which is familiar to 

 every one ; whilst the easily-domesticable, but unintelligent Turkey, has a brain 

 of scarcely half the proportional size. The very small size of the Cerebrum 

 in Reptiles and Fishes, completely harmonizes with the same view ; these 

 animals presenting for the most part but feeble indications of intelligence. 

 Among Reptiles, the Tortoise has a Cerebrum comparable in length to that 

 of Birds; but its breadth and deptli arc far less. The largest Cerebra among 

 Fishes are found in the Shark tribe ; the superior intelligence of which is 



