CHAPTER XXVIII 

 THE BRAIN OF APES AND OF MAN 



A GREAT and undoubtedly very important differ- 

 ence between man and apes is the much greater 

 size of the brain in man. This difference is most con- 

 veniently measured by filling the cavity of a skull, once 

 occupied by the brain, with shot or other such material, 

 and then measuring the bulk of the material required 

 for that purpose. The unit which it is convenient to 

 use in all such measurements is the cubic centimetre, 

 because it is that used by scientific workers all over the 

 world. A cubic centimetre is a cube the side of which 

 is a centimetre long, and two and a half centimetres are 

 equal to one inch. Moreover, if ever one is doubtful as 



, to just how much an inch is, one has only to get hold of 



'! a halfpenny and mark off its breadth on a piece of paper. 

 That is an inch, and two-fifths of it are a centimetre. 

 Using, then, cubic centimetres as our units, we find that 

 a good average European human brain is of the bulk of 



j 1500 units. The gorilla has a slightly larger brain than 

 the chimpanzee or the orang. Individual specimens 

 differ a good deal. This is noteworthy as showing a 

 tendency of this important organ to vary. One of good 

 medium bulk measures 500 units, or a third of that of 



I the well-developed European. The size of European 

 human brains also varies within very large limits — about 

 a third more and a third less — that is, from about 1000 



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