The believers in the doctrine that the human species is essentially distinct from all the known monkeys have laid great stress on the difference between the foot of man and that of anthropoid apes. This difference cannot be denied. Man assumes the direct posture habitually, while monkeys, even the highest of them, walk on two legs only occasionally. There has followed from this a greater development of the feet in monkeys. Yet this difference ought not to be exaggerated. It has been sought to prove that monkeys are “quadrumanous,” and that their hind legs terminate in “hind-hands.” But it is clearly shown that in all essential respects the hinder limb of the gorilla terminates in as true a foot as that of man.[52] “The hind limb of the gorilla, therefore, ends in a true foot, with a very movable great toe. It is a prehensile foot, indeed, but is in no sense a hand; it is a foot which differs from that of man not in any fundamental character, but in mere proportions, in the degree of mobility, and in the secondary arrangement of its parts.”[53] In all these cases the argument is confirmed, “that be the differences between the hand and foot of man and those of the gorilla what they may, the differences between those of the gorilla and those of the lower apes are much greater.”[54] The comparison of muscles and of other internal organs leads to the same conclusion; the differences between monkeys are more varied and greater than those between anthropoids and man. The anatomy of the brain has been much discussed with regard to this. Several distinguished zoologists, amongst them Owen in particular, have insisted on the absence in all monkeys of certain parts of the brain peculiarly characteristic of man. Such are the posterior lobe, the posterior cornu, and the lesser hippocampus. Controversy on this topic has been animated; but, ultimately, the opinion of Owen did not triumph, and now it is unanimously accepted that the parts of the brain in question are “precisely those structures which are the most marked cerebral characters common to man with the apes. They are among the most distinctly simian peculiarities which the human organism exhibits.”[55] [Illustration: FIG. 6.—Cæcum and vermiform appendage of man (after Ewald). ] As regards the brain, the differences between man and anthropoid apes are certainly less marked than those that exist between the higher and lower monkeys. The digestive tract affords another argument in favour of the affinity of anthropoid apes to man. The human cæcum is furnished with the very remarkable and strange vermiform appendage which often is the cause of a grave and prevalent illness known as _appendicitis_. Now, it is quite remarkable that this organ is practically identical with the vermiform appendage of anthropoid apes. A glance at the accompanying figures (6 and 7) will convince the reader of this. Yet none of the other monkeys present any such resemblance with man. [Illustration: