$6 The Destiny of Man. 



thoughts and deeds. If the physiological 

 annals of that long and weary time could 

 now be unrolled before us, the principal 

 fact which we should discern, dominating 

 all other facts in interest and significance, 

 would be that mutual reaction between in- 

 crease of cerebral surface and lengthening 

 of babyhood which I have here described. 

 Thus through the simple continuance 

 and interaction of processes that began far 

 back in the world of warm-blooded animals, 

 we get at last a creature essentially differ- 

 ent from all others. Through the compli- 

 cation of effects the heaping up of minute 

 differences in degree has ended in bring- 

 ing forth a difference in kind. In the hu- 

 man organism physical variation has well- 

 nigh stopped, or is confined to insignificant 

 features, save in the grey surface of the 

 cerebrum. The work of cerebral organi- 

 zation is chiefly completed after birth, as 

 we see by contrasting the smooth ape-like 

 brain-surface of the new-born child with 

 the deeply-furrowed and myriad- seamed 



