Page:Encyclopædia Britannica, Ninth Edition, v. 2.djvu/176

Rh 162 Troglodytes it reaches but very little beyond its proximal end. The entire pelvic limb, measured from the summit of the femur to the distal end of the longest digit, is absolutely greatest in the gorilla, and then in the orang and the chimpanzee. If the pes be removed, then the leg of the chimpanzee is longer than that of the orang. Compared with the length of the spine, the entire pelvic limbs of Hylobates and Ateles are longest, namely, as 162 or 169 to 100. That of Hapale is the shortest, being but as 110 to 100. Without the pes, the leg of Hapale is also shortest relatively com pared with the spine, namely, as 77 to 100; while that of Hylobates is longest, namely, as 125 to 100. The os innominatum is in every species strikingly different in form from that of man. In absolute size this bone attains its maximum in the gorilla, where it is much larger than in man, and where the ilium is very broad. The external surface of the ilium is generally more or less concave, and concave only. In Troglo dytes and Simia, however, it is more or less convex, but not as in man, and therefore there is no sigmoid curva ture of the crest of the ilium, and there are no distinct gluteal lines. The internal Flo. 19 ._ske]eton of the Gorilla Surface Of the ilium is gene- glodytes gorilla). From De Blainville. rally narrow and flat, or only slightly concave, except in the gorilla. The tuberosity of the ischium is always a marked and more or less rugose enlargement of the bone; but in the Simiadw below Troglodytes it is flattened and very much developed, and so much everted that sometimes (in Cynocephalus) its transverse exceeds its antero-posterior diameter. In the Cebidai it again becomes small, and more or less rounded. The spine of the ischium is generally very small, yet distinct. Only in Simia does it attain a considerable sharpness and prominence. The great sciatic notch is never veiy deep and concave, as in man. It is most concave in the gorilla, the orang, and in Cynocephalus. The lesser sciatic notch is generally represented by a margin which is so slightly concave as to be almost or quite straight save through the eversion of the tuberosity. The projection of the spine of the isclmim proditces in man a deep notch such as exists in no ape. The cotyloid notch, and the excavation continuous with it, are constantly present, even in Simia, where, however, it is very small and narrow, in harmony with the absence of the ligamentum teres. The femur s length, compared with that of the spine, is as 67 to 100 in Hylobates, 61 in Ateles, 54 in the gorilla, 47 in Simia. It is shortest in Chrysothrix, 40, and Hapale, 37. In the Simiince it is shorter than is the humerus, its proportion to which in Simia is as 73 to 100. Only in some of the Semnopithecinai does its length exceed that of the humerus more than it does in man. The shaft of the femur is sometimes nearly straight, as in Hylobates and in most Cebidai. The femur is stoutest, relatively as well as absolutely, in the gorilla. It is slenderest in Hylo- [ANATOMY bates. The neck of the femur is longest in Simia and Hylobates; shortest in Hapale. Except in the Simiincs and in Mycetes, the great trochanter is pointed at its upper end. The trochanteric fossa is shallow in the gorilla, but is in most forms deep. The lesser trochanter is at its mini mum of relative size in the Simiince,, and is largest relatively in Hapale, and the posterior surface of the femur is in that genus wide and flat between the trochanters. The pit for the insertion of the ligamentum teres is always present, except in the orang and gorilla, where it is absent almost con stantly in the first ape, occasionally in the second. In the Simiince, Ateles, and Lagothrix the internal condyle pro jects considerably further backwards than does the external one. The angle formed by the neck of the femur with the shaft varies from about 155 (Simia) to 128 (the gorilla). The tibia and fibula never become ankylosed together. The tibia is absolutely longest in the gorilla. Its length, compared with that of the spine, is never so great as in man, except in Hylobates, in which it is slightly longer relatively. It is shortest in Mycetes, about as 37 to 100. Its length is generally less than that of the femur, but sometimes, in Hapale, it slightly exceeds it. It is never, however, so short compared with the femur as in man. The crest of the tibia is not so sharp as in man. The shaft is sometimes straight, as in Lagothrix and Pithecia, sometimes considerably curved, as in the gorilla and lower Cebidcc. The malleolus is generally well-developed, but sometimes, as in the orang, very short. Its articular sur face is sometimes nearly at right angles with the inferior surface of the shaft of the tibia, as in the chimpanzee ; sometimes it forms an obtuse angle with that surface, as in the gorilla, and still more in the orang. The distal articular surface of the shaft of the tibia is rarely hori zontal, as in Ateles and Lagothrix. In the Simiadcc and lower Ccbidce the outer portion rises so that the articular surface slopes upwards and peronead. The fibula has its malleolus much produced outwards, projecting only about as much as, or rather less than, the tibial malleolus, where as in man the fibular malleolus is much deeper than the tibial one. The length of the pes (or foot) is absolutely greatest in the orang and gorilla. Estimating the spine as 100, the length of the pes is as much as 53 in the orang; it approximates to man (35 to 100) most in the lowest Simiadce, and in Chrysothrix 36 to 100. The propor tional length of the pes to the rest of the pelvic Hmb is greatest in Simia (58 to 100), then in Nycti2thecus and Hapale (50 to 100), but never falling quite so low as in man, where it is 30 to 100. Its length, as compared with that of the tibia, is greatest in Simia (122 to 100). In all the rest it is more than four-fifths, except sometimes in Hylobates, which however is never so small as in man, i.e., as 67 to 100. The length of the pes, compared with that of the manus, is greatest in Chrysothrix (177 to 100). In Ateles it sinks to 113 to 100, and in Hylobates to 85 or 84 to 100. The absolute length of the tarsus is never so great as in man, though that of the gorilla is nearly as long. The rest of the foot is so much longer relatively in apes than in man, that, whereas in him the proportion of the tarsus to the whole pes is as about 46 to 100, it is only 39 to 100 in the gorilla, which in this respect approaches nearest to man. The proportion sinks to 26 to 100 in Simia and Ateles, and 27 or 28 to 100 in Hylobates. Only in Simia and Hylobates is the tarsus ever less, or only a very little more, than twice the length of the carpus. The tarsus consists constantly of the same seven bones as in man, and these bones are so arranged, or bound together by ligaments, as to form a transverse and an antero-posterior