" 19. The minor extent of connection of 1 the lachrymal with the pars plans' of the mthmoid, or their separation by the junction of the orbital plate of the maxillary with that of the frontal behind the lachrymal.
" 20. The depth of the olfactory fossa, and the absence or rudimental state of the crista galli.
" 21. The squamosal, lambdoidal, alisphe noidal and pterygoid air-cells.
" 22. The more prominent cusps of the molar teeth.
" 23. The larger relative size, and more complex grinding surface of the last molar tooth in both jaws.
" 21. The larger relative size of the pre molars, especially of the first.
" 25. The more complex implantation of the premolars by three roots, two external and one internal.
" 26. The much larger and longer canines.
" 27. The sexual distinction in the develop ment of these teeth.
" 28. The more sloping position of the crowns of the incisors.
" 29. The broader and higher ascending ramus of the lower jaw.
" 30. The total absence of the prominence of the symphy-sis forming the chin.
" In the form of the premaxillaries, and the earlier obliteration of their sutures," Prof. Owen continues, " the smaller chimpanzee more nearly resembles man than the great gorilla does ; it seems also to deviate less through the minor development of the canine teeth, and of the parietal and sagittal crests ; but it has been shown, in the comparison of the skulls of Troglodytes gorilla and T. niger, that the latter departs in more numerous and important particulars further from the human type." Now, of the foregoing characters, some of those which constitute the most striking fea tures in the cranium of the Chimpanzee, are those which must be admitted from analogy to be liable to variation under the influence of a change of habits, provided such change could be induced. Thus we find that in dogs, the general form of the cranium, and the sagittal crest, undergo considerable modifica tion ; the brain acquiring a very large size, in several of the domesticated races, at an early period of life ; and the parietal bones being expanded over it so as to form a smooth dome, instead of rising up to meet in a ver tical ridge. But the prominence of the supra orbital ridge does not seem to be in any way connected with the relative development of the cerebrum and of the muscular system ; and as Prof. Owen remarks, " We have no grounds from observation or experiment to believe the absence or the presence of a pro minent supra-orbital ridge to be a modifiable character, or one to be gained or lost through the operation of external causes, inducing particular habits through successive genera tions of a species. It may be concluded, therefore, that such feeble indication of the supra-orbital ridge, aided by the expansion of the frontal sinuses, as exists in man, is as much a specific peculiarity of the human skull, in the present comparison, as the ex aggeration or suppression of this ridge is respectively characteristic of the chimpanzees and orangs." The same may be said of nearly
all the other distinctive characters which have been so minutely enumerated ; for they serve to distinguish the great chimpanzee from all the varieties of the human race, from the most degraded African, as well as from the most elevated European. The shape, size, and construction of the " pre maxillary" bones (" inter-maxillaries " of the ordinary nomenclature) are peculiarly distinc tive; for they not only differ from those of Man in their vastly greater proportional size, their greater prominence, and the longer per sistence of their sutures, but also in their upward extension around the nostrils, so that they completely exclude the maxillary bones from their borders, and form the bases of support for the nasal bones (fig. 800.) It is to be remembered that the apparent defi ciency ofthe inter-maxillary bone in the human subject is the result of its early coalescence with the maxillary ; and that this coalescence may he prevented by an arrest of development, so that the two bones remain permanently distinct.* Having dwelt thus fully on the distinctive features of the Osteology of Man, it will be sufficient to pass over his other peculiarities of conformation more cursorily, referring to the article QUADRUMANA for more minute details. In his the most charac teristic difference is the much greater de velopment of those muscles of the trunk and limbs, which contribute to the maintenance of the erect posture. Thus the gastrocnemii and the other muscles which tend to keep the leg erect upon the foot. form a much more prominent "calf" than is seen in any other animal. So, again, the extensors of the leg upon the thigh are much more powerful than the flexors ; a character which is pecu liar to man. The glutei, by which the pelvis is kept erect upon the thigh, are of far greater size than is elsewhere seen. The superior power of the muscles tending to draw the head and spine backwards, has been already referred to. Among the differences in the attachment of individual muscles, we may no tice that the flexor longus pollicis pedis pro ceeds in man to the great toe alone, on which the weight of the body is often supported ; whilst it is attached in the chimpanzee and orang to the three middle toes. The latissi mus dorsi of man is destitute of that pro longation attached to the olecranon, which is found in most of the lower Mammalia, and which exists even in the chimpanzee, pro bably giving assistance in its climbing movements. The larger size of the muscles of the thumb is, as might be expected, a characteristic of the hand of man, though the number of muscles by which that digit is moved is the same in the chimpanzee as in the human subject. The existence of the extensor digiti indicis, as a distinct muscle, however, is peculiar to man.