Page:Popular Science Monthly Volume 13.djvu/449

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seems diminished when we compare the man-apes with the baboons and lower, tailed monkeys in this respect. The cranium of the gorilla is also very small in proportion to that of man. The contents of the smallest skull of man is given at sixty-two cubic inches; that of an adult gorilla is given at thirty-four cubic inches. But this difference loses much of its value when we see the amount of variation in men of the skull measurements. Thus the largest human skull shows a capacity of 114 cubic inches, being about twice the size of the smallest adult human skull.

Now, the difference thus shown in man of fifty-two cubic inches between the capacity of the largest and smallest skulls is greater than that between the smallest human skull and that of the gorilla, which is only twenty-seven inches. These figures will probably be still further modified so soon as we get accurate measurements of the skulls of certain African and Indian hill tribes more recently discovered. Indeed, it is already stated that twelve cubic inches of cranial capacity will cover the difference between the smallest human and the largest simian skull yet known. Again here, as with the prognathic characters, the importance of the difference in cranial size is diminished by the fact of its variation among the apes and monkeys, which latter are found to fall as much below the apes in cranial capacity as the apes do as compared with man. The skull of the gorilla exhibits considerable variation in the specimens which have been yet examimed. The males seem to have a prominent bony ridge on the crown of the skull, but this development of the bone stands in proportion to the muscles of the jaws which reach on each side up to the crest which they deposit. Where the jaws are weaker, as in the female, the crest is undeveloped, the muscles do not reach up so far and they deposit smaller ridges on the side of the skull. These crests are, however, wanting in the orang-outang, a lower kind of man-ape than the gorilla, where they are replaced by two bony ridges, a couple of inches apart, as we learn from Mr. Wallace's interesting writings. But the variation among the skulls of the gorilla yet examined is so great in the proportion of the different parts of the face, that it is evident there is a greater amount of individual peculiarity in this than in any other animal except man. This point is worthy of a much more extended examination than it is now possible to give to it. It is sufficient to state that these differences seem to have prompted Dr. Wyman and Du Chaillu to suspect species where in fact we find only one kind of gorilla as more specimens come to hand and supply the intermediary links. With regard to the permanent teeth of the gorilla they are thirty-two in number, just as in man. The principal difference is that the canine teeth, at least in the adult males, are longer than in man, and project. The jaws being more powerful and more constantly in use, the teeth are stronger and proportionally stouter than in man. And where we find any difference, such as is offered by the large canines, and the break in the lower series to admit of the play of