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 animals. 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, differences 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, creatures 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 neopallium) are much more strongly represented in the ape (Fig. 2). Moreover, the plan formed by the folding of the neopallium in the lion (Fig. 1) seems to be so utterly unlike that of the ape that anatomists are still disputing whether
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