THE EVOLUTION OF THE BRAIN 



someone else to discover the same structure in some non- 

 human brain. Scores of such futile claims have been made 

 decade after decade. But at last we have learned that there 

 is no distinctive structure in the human brain; there is no 

 tissue or formation that is not found in apparently as highly 

 differentiated form in the brains of certain non-human ani- 

 mals. What then, it will be asked, is the real difference 

 between the human organ of mind and that of the ape, which 

 approaches man's brain most nearly in form? 



If the brains of a series of mammals are compared, dif- 

 ferences in shape and pattern at once become obvious. The 

 anatomist can discriminate between them as easily as he can 

 recognize the animals themselves. For example, compare 

 the brain of a lion with that of a gorilla (Figs. 1 and 2). 

 In both a great body of tissue (cerebral cortex known as 

 the neopallium) is built up above the smaller mass that 

 formed the older type of brain, a mass that was conjoined 

 mainly with the sense of smell and that is relatively larger 

 and more potent in the lion than in the ape (compare Figs. 

 1 and 2). The neopallium is the receptive organ of such 

 senses as vision, hearing, and touch; it is the instrument 

 whereby the information brought into the brain by these 

 special senses can be blended and recorded so as to be 

 recalled in memory and to influence the movements and 

 behaviour of the whole organism. 



By comparing the brains of the lion and the gorilla, crea- 

 tures of roughly the same bulk, we may see that, although 

 in the lion the sense of smell is more strongly represented 

 than in the gorilla, the other senses (expressed in the neo- 

 pallium) are much more strongly represented in the ape 

 (Fig. 2). Moreover, the plan formed by the folding of the 

 neopallium in the lion (Fig. l) seems to be so utterly unlike 

 that of the ape that anatomists are still disputing whether 



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