The chimpanzee approximates more nearly to the human structure in those deviations which are numbered 4, 5, 6, 7, 8, 9, 10, 12, 13, 17, 18, 19, 20, 21, 22, 23.
The orang has a nearer resemblance to man :-1. In the junction of the sphenoid with the parietal bones. 2. In having twelve pairs of ribs. 3. In the form of the scapula, especially in its greater breadth.
Owen well observes that it is a result of the preceding comparison that the chimpanzee ought to rank above the orang in a descending series, and not below it as in the ‘Itegne Animal' of envier.
Linnaeus, as we have seen, gave the chimpanzee that superiority of rank, but erred as much on the other Bide by placing it under the genus Homo for both the chimpanzee and orang, according to Owen, differ in structure from the human subject :-1. In the diastema, or interval between the cuspidati and incisors in the upper jaw, and between the cuspidati and bicuspides of the lower jaw. 2. In the greater magnitude of the intermaxillary bones, indicated in the adult by the distance of the foramina incisive from the incisive teeth ; both of which differences result from the greater proportional develop ment and different forms of the cnspidati and incisors. These, as the author observes, are differences of generic value. 3. In the more backward position and oblique plane of the occipital foramen. 4. In the smaller proportional size of the occipital coudyles. 5. In the larger proportional size of the petrous bones. 6. In the greater proportional de velopment of the jaws. 7. In the flatness of the nasal bone, which is rarely divided in the menial line, while in man the nasal bones are as rarely consolidated into ono. 8. In the presence of the ant - auditory process of the temporal bone, and the absence of the mastoid and styloid processes. 9. In the absence of the process of the ethmoid, called crista galli. 10. In the shortness and comparative weakness of the lumbar region of the spinal column ; which is also composed of four in stead of five vertebrm. 11. In the narrowness and pro portional length• of tho sacrum. 12. In the flatness of the ilia, and the larger development and outward curvatIme of the Ischia. 13. In the position of the pelvis in relation to the spine. 14. In the larger proportional development of the cheat. 15. In the greater length of the upper extremities. 16. In the wider interval be tween the ulna and radius. 17. In the shortness and weakness of the thumb, and narrowness of the hand in relation to its length. 18. Iu the shortness of the lower extremities. 19. In the greater proportional length and narrowness of the foot. 20. In the small size of the os erileis. 21. In the shortness and oppose able condition of the hallux.
" These differences," adds Professor Owen, "result from original formation, and are not liable to be weakened in any material degree, either on the one hand, by a degradation of the human species, or, on the other hand, by the highest cultivation of which the anthropoid apes are susceptible." In following out this osteological comparison it becomes necessary, for the assistance of the student, to give a sketch of the cranial development in man and in the anthropoid apes, so that he may have under his eye the comparative form of each.
We cannot do better than give the following conclusive statements of Professor Owen.
"Certain modifications in the form of the human pelvis have been observed to accompany the different forme of the cranium which characterise the different races of mankind; but there is nothing in the form of the pelvis of the Australian or Negro which tends to diminish the wide hiatus that separates the bimanous from the quadrumanous type of structure In regard to . this part of the
skeleton. Observation has not yet shown that the pelvis of the orang, in a state of captivity, undergoes any change approximating it towards the peculiar form which the same part presents in the human subject. The idea that the iliac bones would become expanded and curved forwards, from the pressure of the superincumbent viscera, consequent on habitual attempts at progression on the lower extremities, Is merely speculative. Those features of the cranium of the amps which stamp the character of the irrational brute most strongly upon their frame, are however of a kind, and the result of a law, originally impressed upon the species, which cannot be supposed to be modified under any circumstances, or during any lapse of time; for what external influence operating upon and around the animal can possibly modify in its offspring the forms, or alter the size, of the deeply-seated germs of the permanent teeth 1 They exist before the animal is born; and let him improve his thinking faculties as he may, they must, in obedience to an irresistible law, pass through the phases of their development, and induce those remarkable changes in the maxillary portion of the skull which give to the adult orange a more bestial form and expression of head than many of the inferior Sinthe present. It is true that in the human subject the cranium varies in its relative proportions to the face in different tribes, according to the degree of civilisation and cerebral development which they attain ; and that in the more debased Ethiopian varieties, and Papuans, the skull makes some approximation to the quadrumanous proportions : but in these cases, as well as when the cranium is distorted by artificial means or by congenital malformation, it is always accompanied by a form of the jaws, and by a disposition and proportions of the teeth, which afford unfailing and impassable generic distinctions between man and the ape. To place this propo sition in the most unexceptionable light, I have selected the cranium of a human idiot, in whom nature may be said to have performed for us the experiment of arresting the development of the brain almost exactly at the size which it attains in the chimpanzee, and where the intellectual faculties were scarcely more developed ; yet no anatomist would hesitate in at once referring this crauium to the human species. A detailed comparison with the cranium of the chimpanzee or orang %howl; that all those characters are retained in the idiot's skull which constitute the differential features of the human structure. The cranial cavity extends downwards below the level of the glenoid articulatory surfaces. The nasal bones are two in number, and prominent. The jaws and teeth exhibit the bimanous characters as strongly as in the most elevated of the human race. The cuspidati do not project beyond the contiguous teeth, and consequently there are no interruptions in the dental series, WS in the orange, where they are required to lodge the disproportionate crowns of the canine teeth." Ni. Geoffrey St. Hilaire characterised the sub-genus Troglodytes from immature Chimpanzees; and as Professor Owerfa observations were made upon the skeleton of an adult individual, and he has consequently altered the zoological characters given by Geoffrey, we follow Professor Owen's definition.