144 WHAT IS LIFE ? 



independent of education, and only partly. Such are 

 called men with innate ideas. 1 And when such men 



1 " Taking a series of human brains, and comparing the convolu- 

 tions of uncivilised and civilised men, of men distinguished by 

 abilities much above or much below the average, a general relation is 

 traceable between complexity of surface and degree of intelligence. 

 The basal ganglia are identical in the two cases, but the higher brain 

 is more richly convoluted, its sulci. are more numerous ; the lower 

 brain is simpler, its sulci are less numerous ; the latter is practically 

 a simplified diagram of the former ; the effect of the difference is that 

 the total area of grey matter is greater in the more highly than in 

 the less highly organised brain. This is all we know with regard to 

 the relation between quality of organ and quality of f unction ; finer 

 and more impalpable relations doubtless exist, but have not been 

 demonstrated ; the very absence of anatomical difference in the brains 

 of average and of exceptionally able men leaves us, however, free to 

 think, and justified in believing, that beyond quantity of grey matter 

 there are differences in its quality. Perhaps its cells are more 

 numerous, perhaps these more numerous cells are of better quality in 

 the brains of the exceptionally able ; but no microscopical or chemical 

 proof has been given for or against such suppositions, still less is 

 there any physical evidence available to distinguish the brain matter 

 of 'good' men from that of 'bad' men." ("An Introduction to- 

 Human Physiology," A. D. Waller, M.D., F.R.S., 1896, p. 522.) 



" The total number of nerve-cells in the human brain has been 

 estimated at 2,000 millions." (Idem, p. 528.) 



" The brain, or, more precisely speaking, the cortex of the brain, 

 is the organ of intelligent sensation and motion. Taken in the 

 rough, the intellectual rank of animals bears some relation to the- 

 weight of the brain. Thus the average ratio between brain-weight 

 and body-weight is in round numbers : 



In fishes . . . 1 to 5,000 



reptiles . 1 to 1,500 



birds . . . 1 to 220 



,, mammals . . . 1 to 180 



,, ourang . . . 1 to 120 



,, man . . 1 to 50 



But mere weight of brain is not a regular index of degree of in- 



