Chapter IV 



THE EVOLUTION OF THE BRAIN 



George H. Parker 



NO organ is so distinctive of man as his brain. Long 

 recognized as the seat of his mental hfe, it is that 

 portion of his body most concerned with his per- 

 sonahty. Here take place those changes that give rise to his 

 sensations, his memories, his voKtions; here arise his emo- 

 tions, the figments of his imagination, his dreams; and 

 here too, in abnormal states, appear those idiosyncracies 

 and moods that pass over step by step into insanity. In 

 short, the brain is the organ of his mind, his very soul. 

 Not that the brain alone is all this, for this organ is buried 

 in his body, which, as an environment, yields among other 

 things the whole range of internal secretions determining 

 as they do in so many ways the setting for the individual 

 Hfe. But notwithstanding the importance of these surround- 

 ings, the brain harbors what is one's truest self and in this 

 respect no other organ in us is its peer. 



Man's brain more than any other part separates him 

 from all other creatures. Even its weight shows this. Two 

 hving animals only, the elephant and the whale, have 

 brains heavier than his. The elephant's brain weighs about 

 12 pounds, that of a large whale about lo pounds, while 

 man's brain turns the balance at almost exactly 3 pounds. 

 All other mammals such as the horse and the cow and even 

 giants like the rhinoceros and the hippopotamus have 

 smaller brains than man. The gorilla, a close relative to 

 man and slightly heavier in body than he is, has nevertheless 

 a brain scarcely one-third as large. Thus man outstrips 

 all other living animals, except the elephant and the whale, 

 in the absolute weight of his brain. 



Every one is familiar with the fact that the size of an 

 animal's brain is roughly proportional to that of its body; 

 the elephant has a gigantic brain, the mouse a diminutive 

 one. But it is not so commonly known that large animals 



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