20 PROFESSOR OWEN ON THE OSTEOLOGY OF 
are more nearly confluent ; the rotular protuberance (f) is less prominent. As in the 
Gorilla, the analogy of the leg with the forearm is maintained by the width of the inter- 
osseous space, the modification of the lower limb for a special office not being carried 
out so far as in the Human subject. The inner malleolus is thicker and more truncate 
at its lower extremity (fig. 7, 7’) ; the distal articular surface is more convex transversely, 
and the outer and front angle (fig. 7, k) is more produced, than in the Gorilla. 
The Human tibia (Pl. VIII. figs. 9, 10), besides its greater length, differs in the 
more equable diameter of the shaft, and more parallel contour of the outer and inner 
sides, with a considerable reduction of the interosseous space. ‘The crest (h) descends, 
near the middle of the anterior surface of the shaft, with a slightly sigmoid or wavy course. 
The distal articular surface (m) is uniformly concave from before backward, and is straight 
from side to side at the bottom of the tibia ; it is continued at a less open angle, and to 
a greater extent, upon the articular side of the inner malleolus (7), the articulation with 
the astragalus being deeper and firmer than in the Gorilla or Chimpanzee. 
The fibula is a thicker and stronger bone in proportion to its length in both the 
Gorilla (Pl. VIII. fig. 1, f) and Chimpanzee (ib. fig. 5, f) than in Man: its proximal 
end in the Gorilla (fig. 4) shows a weli-marked articular depression, of a larger propor- 
tional size than is the corresponding flattened facet in Man (fig. 11); and the rough 
prominence external to this is more developed in both the great Apes (figs. 4 & 8). The 
shaft is straighter, and shows no inclination towards the tibia as in Man. The expanded 
lower end inclines more outward, aud does not descend to the level of the inner malleolus. 
In Man (fig. 9, 2), it is more vertical, and descends lower than the inner malleolus— 
interposing a greater obstacle to lateral inflections of the foot upon the leg than in 
either the Gorilla or Chimpanzee. 
Bones of the Foot.—Plate XI. 
The chief departure from the Human type of foot, exemplified by the figures in the 
above Plate, is the angle at which the innermost toe in the Gorilla (fig. 2, i) articulates 
with the tarsus ; whereby it becomes an opposable thumb, as in other Quadrumana. 
In the Orang-utan the foot is longer than the leg; in the Gorilla it is nearly as long ; 
in Man it is shorter: thus, the length of the tibia in a Man being 16 inches, that of the 
foot-bones is 10 inches (as in Pl. XIII. fig. 1); whilst in the Gorilla, the length of 
the tibia being 123 inches, that of the foot is 12 inches (as in Pl. XIII. fig. 2). 
The foot is so articulated with the leg in the Gorilla, that the sole is turned a little 
inward ; the concavity of the sole lengthwise is greater than in Man by reason of the 
permanent partial flexure of the toes, the disposition of the articular ligaments being 
such as to oppose some force to the attempt to press the toes into a straight line, such 
as they generally present in Man. The transverse arch or concavity is less deep across 
the tarso-metatarsal joints than in Man. The tarsus is shorter in proportion to the foot, 
and is broader thanin Man. There is less inequality in respect of thickness between the 
