CONVOLUTIONS OF BRAIN. 227 



(cerebrum) of higher Mammals (Figs. 219, 220). If the 

 brains of the various mammalian groups are compared with 

 reference to these convolutions and furrows, it appears that 

 theii gradual development is entirely proportionate with 

 the development of the higher intellectual activities. Much 

 attention has recently been devoted to this particular 

 branch of the Anatomy of the brain, and very striking 

 individual differences have been found even within the 

 human race. In all human individuals distinguished by 

 peculiar ability and great intellect, these swellings and 

 furrows on the surface of the great hemispheres exhibit a 

 much greater development than in common average men; 

 while in the latter, again, they are more developed than in 

 Cretins and others of unusually feeble intellect. There are 

 also similar gradations in the internal structure of the fore- 

 brain in Mammals. The great cross-piece (corpus callosum), 

 especially, the bridge between the two great hemispheres, 

 is developed only in Placental Animals. Other arrange- 

 ments, for example, in the structure of the lateral cavities, 

 which seem primarily to be peculiar to Men as such, re- 

 appear only in the higher species of Apes. It was long 

 believed that Man had some entirely peculiar organs in the 

 great brain (cerebrum), which are wanting in all other animals. 

 But close comparison has shown that this is not the case, 

 but that rather the characteristic qualities of the human 

 brain exist in a rudimentary state even in the lower Apes, 

 and are developed to a greater or less degree in the higher 

 Apes. Huxley, in his important and much-quoted book, 

 " Evidence as to Man's Place in Nature " (1863), has shown, 

 most convincingly, that within the Ape-series the differences 

 in the formation of the brain are greater between the 



