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A TEXTBOOK OF PHYSIOLOGY 



The Cerebral Hemispheres. The cerebral hemispheres are the 

 latest outgrowths of the brain to .be developed, and are particularly 

 well developed in the higher apes and man. Particularly is this the 

 case in man, where the cerebral hemispheres reach a large size and 

 become much convoluted. The convolutions are marked off by 

 fissures and sulci. 



The great development of the brain of man is seen from the fol- 

 lowing figures: 



Brain Weight. 



Body Weight. 



Ratio of Brain to 

 Body Weight. 



Elephant 



Man . . 



Horse 



Donkey 



Lion . . 



Gorilla 



Ourang 



Chimpanzee 



Dog (St. Bernard) 



Macaque monkey 



Rabbit 



5,443 

 1,431 



615 



385 



219 



463 



431 



406 



123 

 97-7 

 9-7 



3,048,000 



66,200 



375,000 



175,000 



119,500 



90,000 



80,000 



80,000 



53,000 



7,280 



1,420 



1:560 



46 

 698 

 457 

 546 

 194 

 186 

 197 

 1:430 

 1: 74-5 

 1: 146 



Man's brain is only surpassed in weight by that of the whale and 

 the elephant. It is markedly heavier than that of the primates. 

 Although this indicates man's great intellectual development, mere 

 weight of brain is not in itself everything. One of the heaviest brains 

 on record belonged to a bricklayer. But many great men have had 

 brains decidedly above the average in weight. Byron's brain weighed 

 2,238 grammes, Cromwell's 2,233 grammes, Cuvier's 1,830 grammes. 

 Many eminent men, however, have not had such exceptionally heavy 

 brains. Helmholtz's brain weighed 1,430 grammes, Gauss's brain 

 1,492 grammes. The depths of the convolutions rather than the 

 absolute weight appears to be of importance. 



The Functions of the Cerebrum. The functions of the cerebrum 

 have been elucidated by studying the effect of its removal or partial 

 removal. This varies with the status of the animal in the evolutionary 

 scale. Thus, in the early experiments on this point it was found 

 that in a bony or teleostean fish the effect of removal of the fore- 

 brain was scarcely apparent ; such a fish immediately seized and 

 swallowed a worm when thrown near it. The fish either did not 

 touch or, if seized, did not swallow a skein of thread of about the 

 dimensions of the worm. When thrown one red and four white - 

 wafers, the red was regularly devoured first. The fish would follow 

 a worm held in the forceps, but would not attempt to swallow it. 



