The whole skeleton, and particularly the skull of man, and the higher monkeys, present certainly some marked differences; but here again the differences are less than those between the anthropoid apes and other monkeys. As regards the osteology the proposition laid down by Huxley is just. So that, for the skull, no less than for the skeleton in general, the proposition holds good, that the differences between man and the gorilla are of smaller value than those between the gorilla and some other apes." * 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 occasion. ally. 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.† "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." + 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 + Loc. cit. p. 126. * Loc. cit. p. III. Loc. cit. p. 126. those of the gorilla and those of the lower apes are much greater."* 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 Cæcum FIG. 6.-Cæcum and vermiform appendage of man (after Ewald). anthropoids and man. The Several anatomy of the brain has been much discussed with regard to this. 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. "† 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 *Loc. cit. P. 127. + Loc. cit. p. 139. 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 accompany FIG. 7.-Cæcum and vermiform appendage of the chimpanzee (from a preparation in the Paris Museum of Natural History). numerous, that forty years' science has proclaimed the existence of a close affinity between man and the anthropoid apes. The view has become an established doctrine, now that no single fact has been brought against it. Since the theory was enunciated we have learned much regarding the natural history of these apes. Generally, when a theory is false, a new set of facts overthrows it. Attempts may be made to trim the new facts to the existing theory, but such attempts are doomed to failure, and the theory disappears. It is of special interest, then, to confront the simian theory of the origin of man with a series of facts gathered by science since the theory was propounded. When Huxley wrote, the embryological history of anthropoid apes was practically unknown. Darwin, Vogt, and Haeckel, in their attempts to support the theory of the animal origin of man, had not sufficient knowledge of the embryology of monkeys. It is only recently that important work on this subject has been published. It is known that the history of development is very often an excellent guide in tracing the relationship of organisms. It is therefore interesting to examine the established facts concerning the embryology of anthropoid apes. The material for these studies is very difficult to obtain, and it is not astonishing that even our present state of knowledge is still imperfect. The placenta often gives information of great importance in the classification of mammals. It is sufficient to glance at the zonary placenta of dogs and seals to be convinced of the relationship of these two species, which at first sight seem so different. Now, the placentas of all the anthropoid apes examined up to the present are of the same discoid type as that of man. The arrangement of the umbilical cord of man, which was formerly considered as quite peculiar to him, is found in anthropoid apes, as has been established by Deniker* and Selenka.† It is striking that the anthropoids resemble man rather than the lower Fi. 9-Human foetus of three months and a half. monkeys in the relation of the foetus to the foetal membranes. With regard to the embryos themselves, the similarity between those of monkeys and of man is very great. Selenka insists on the fact that the youngest stages of human development that have been obtained can hardly be distinguished from those of the lower monkeys either in position or in shape. More advanced stages exhibit greater differentiation, and the later embryos of man resemble those of * "Archives de Zoologie expérimentale," 1885. t "Studien über Entwickelungsgeschichte der Thiere," 1898-1902. |