276 THE BRAIN OF QUADRUPEDS AND 



especially the latter) are in a comparatively rudimentary 

 condition. 



Speaking generally, it may be said that in Quadrupeds 

 the Brain tends gradually to become more and more con- 

 voluted as we proceed from lower to higher orders. It 

 must not be supposed, however, that anything like a 

 serial development is to be detected in the first place, 

 because certain differences in ' plan of Convolution,' seem to 

 be traceable among them ; and secondly, because in all the 

 orders (and therefore, even in cases where the same plan 

 is observable), the degree of complicacy of the convolutions 

 is very largely determined by the mere size of the animal. 

 It has been found, for instance, as a general rule to which 

 there are only few exceptions, that in animals of the same 

 group or order, the number and complexity of the convolu- 

 tions increase with the size of the animal. This may be 

 recognized, for instance, by a comparison of the brain of the 

 Horse with that of the Elephant ; of those of the Sheep 

 and Ox ; of the brain of the Cat with that of the Seal ; 

 and also, as we shall find, of those of smaller and of 

 larger Quadrumara. In the Elephant, the largest though 

 also the most sagacious of existing Quadrupeds, the com- 

 plexity of cerebral convolutions is at its maximum. They 

 are also exceedingly complex in the huge Cetacea, and 

 even in some of the smaller representatives of the same 

 class. 



It has been previously shown that the weight of the 

 Brain as compared with that of the body is less in different 

 orders of animals, as the size of the representative of any 

 such order increases ; yet now it appears that this smaller 

 proportional size of the Brain in large animals is, to a 

 certain extent, compensated by its greater proportional 

 extent of surface ganglionic matter obtained through 

 increased number and depth of Convolutions. 



