226 THE EVOLUTION OF MAN. 



the animal, thus proving that the higher mental activities, 

 consciousness and thought, conscious volition and sensation, 

 may be destroyed one by one, and finally entirely anni- 

 hilated. If the animal thus treated is artificially fed, it 

 may be kept alive for a long time ; for the nourishment of 

 the entire body, digestion, respiration, the circulation of the 

 blood, secretion, in short, the vegetative functions, are in 

 no way destroyed by this destruction of the most important 

 mental organs. Conscious sensation and voluntary motion, 

 the capacity for thought and the combination of the various 

 higher mental activities, have alone been lost. 



This fore-brain, the source of all these most wonderful 

 nervous activities, reaches that high degree of perfection only 

 in the higher Placental Animals (Placentalia) ; a fact which 

 explains very clearly why the higher Mammals so far excel 

 the lower in intellectual capacity. While the "mind" of the 

 lower Placental Animals does not exceed that of Birds and 

 Reptiles, we find among the higher Placentalia an uninter- 

 rupted gradation up to Apes and Man. Accordingly, their 

 anterior brains show surprising differences in the degree of 

 perfection. In the lower Mammals, the surface of the great 

 hemispheres (the most important part) is entirely smooth 

 and even. The fore-brain, too, remains so small that it 

 does not even cover the mid-brain above (Fig. 230). One 

 stage higher, and this latter is indeed entirely covered by 

 the excessive growth of the fore-brain ; but the hind-brain 

 remains free and uncovered. At last, in Apes and in Man, 

 the fore-brain covers the hind-brain also. A similar gradual 

 advance may also be traced in the development of the 

 peculiar furrows and protuberances which are so charac- 

 teristically prominent on the surface of the large brain 



