Parallel with this series, and with a like sudden and great interval between the highest ape and man, was the progression of the modifications of the foot, which were traced up from the Carnivora, though Galeopithecus, the aye-aye, and other lemurs, the platyrrhine and catarhine Quadrumana, up to man. It was associated with the intellectual capacities, the power of framing general propositions, and of expressing thought in articulate speech. The sudden advance of so supremely important an organ as the brain, in the human race, and the marked hiatus between the highest grade of its structure and the next step below, attained by the orangs, chimpanzees, and gorillas, was one of the most extraordinary in the whole range of Comparative Anatomy. Passing on to the Lemurine series, he showed how the still descending cerebral organ graduated into that of the ordinary Feline. Professor Owen then pointed out the close and gradual transition in the Quadrumanous series, from the gorilla's brain to that of the smooth and unconvoluted cerebrum of the marmoset, such simplification of the cerebrum being unaccompanied by difference of its relative horizontal extent to the cerebellum and he noticed the intermediate exceptions, where, as in the maimon baboon, through the restricted development of the cerebellum, the smooth, unconvoluted posterior part of the cerebrum, even extended beyond the cerebellum,an exception of that kind, like the long nose of the Semnopithecus nasicus, which serves to prove the rule. This evidence of the cerebral organ in the largest and most anthropoid of the anthropoid apes was alone wanting to test the validity of the zoological character of the group represented by man, as given in the author's Classification of Mammalia.
He then contrasted the sudden and great development of the cerebral organ presented by a man of the lower order great increase in absolute size still greater superiority in relative size to the bulk and weight of the body the gorilla having the trunk, and head, and upper limbs of a giant, supported on dwarfed, but powerful grasping legs. The cerebrum extended over the cerebellum, not beyond it. The brain of the highest known ape showed no increase of the relative extent of cerebrum over cerebellum beyond that of the small South American monkeys. He contrasted with it the cast of the brain of a man, from the museum of Professor Clark, taken after the brain had been hardened for the purpose, and stripped of its coverings it, therefore, showed some contraction of size but the cerebrum and cerebellum being equally condensed, their relative proportions were preserved. Professor Owen premised that the cast which he exhibited was not that of the brain of the gorilla, but of the interior of the skull of an adult male of that ape it, therefore, presented a slightly exaggerated view of the size of that organ but the proportions of the cerebrum to the cerebellum, and the size and general disposition of the convolutions of the cerebrum, were shown. The Brain and Limb Characters of the Gorilla and Man (1862) On the Zoological Significance of the Brain and Limb Characters of the Gorilla, as Contrasted with Those of Man
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