22 THE KINGDOM OF MAN 



however, he was not deficient. Probably this creature 

 had nearly the full size of brain and every other physical 

 character of modern man, although he had not as yet 

 stumbled upon the art of making fire by friction, nor 

 converted his conventional grunts and groans, his 

 screams, laughter, and interjections into a language 

 corresponding to (and thenceforth developing) his power 

 of thought. 



9. THE ENLARGED BRAIN. 



The leading feature in the development and separa- 

 tion of man from amongst other animals is undoubtedly 

 the relatively enormous size of the brain in man, and 

 the corresponding increase in its activities and capacity. 

 It is a very striking fact that it was not in the ances- 

 tors of man alone that this increase in the size of the 

 brain took place at this same period, viz. the Miocene. 

 The great mammals such as the titanotherium, which 

 represented the rhinoceros in early Tertiary times, had 

 a brain which was in proportion to the bulk of the body, 

 not more than one-eighth the volume of the brain of 

 the modern rhinoceros (see Fig. 5). Other great mammals 

 of the earlier Tertiary period were in the same case ; and 

 the ancestors of the horse, which are better known than 

 those of any other modern animal, certainly had very 

 much smaller brains in proportion to the size of their 

 bodies than has their descendant. 



We may well ask to what this sudden and marked 

 increase in the size of the brain in several lines of the 

 animal pedigree is due. It seems that the inborn 

 hereditary nervous mechanism by which many simple 

 and necessary movements of the body are controlled 

 and brought into relation with the outer world acting 

 upon the sense-organs, can be carried in a relatively 



