Section 6. 



The Cerebrum. 



The cerebrum is composed of grey and white matter, the grey 

 being externally placed like a mantle and thrown into convolu- 

 tions. The use of the convolutions is to increase the surface 

 of the grey matter, and their depth has been supposed to bear 

 some relationship to the intelligence of the animal. There are 

 many animals whose cerebra are quite smooth ; there are others, 

 like the bear, seal, and whale, whose cerebra are much more 

 convoluted than in man. 



Weight of brain in relation to body weight has been suggested 

 as a measure of intelligence, and when the comparison is made 

 among animals of the same group it may be possible that the 

 heavier brains are the more intelligent. Weight of brain may, 

 however, depend upon such factors as fluid, white matter, 

 and grey substance. Colin compiled an elaborate series of 

 tables of weight of the cerebral nervous system in animals, and 

 showed that the proportion of brain to body weight was as 

 follows : 



Man 



Cat 



Dog 



Rabbit 



Sheep 



Ass 



Pig 



Horse 



Ox 



to 52 

 > 99 



. 235 

 . 295 

 . 317 

 . 332 

 . 369 

 . 593 

 . 682 



For every kilogramme of body weight — 



Man requires - 

 Cat requires - 

 Dog requires - 

 Rabbit requires 

 Sheep requires 

 Ass requires - 

 Pig requires - 

 Horse requires 

 Ox requires - 



1900 grammes of brain. 



n-37 

 480 



3'3i 

 300 

 2*46 

 1-90 

 168 

 1-47 



In proportion to its size a mouse has more brain than a man, 

 thirteen times more than a horse, and eleven times more than an 

 elephant ; a cat has much more than a dog ; a rabbit nearly 

 approaches a dog. It is evident that outside its own group the 



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