16 PROFESSOR OWEN ON THE OSTEOLOGY OF 
inner commencement of the linea aspera, called the ‘ spiral line’ of the femur, is well 
marked in the Gorilla (Pl. VIL fig. 1, g), but begins close to the inner side of the lesser 
trochanter ; what are called ‘middle’ and ‘outer lines’ of the linea aspera are less 
definitely marked than in Man. A rough tract is continued from the ecto-gluteal! 
ridge (f) obliquely downwards to the middle of the linea aspera, where the medullary 
artery penetrates the bone, the direction of the canal (fig. 1, m) being, as in Man, 
obliquely upward and forward. Below this the linea aspera is continued more faintly 
to the entocondyloid prominence (h'). There is no ridge continued from the linea aspera 
to the outer condyle, as in Man; that ridge (Pl. VIL fig. 6, 9, a’) is lost in the Gorilla 
upon the outer border of the bone. The production of the buttress-like ridge of dense 
bone from the middle of the back part of the shaft of the femur in Man, forming the 
most prominent part of the linea aspera, and strengthening it for the habitual support 
of the erect superincumbent trunk, is not present in the Gorilla ; nor was it called for 
in the occasional assumption of the erect posture by that Ape. The ectocondyloid 
prominence (ib. fig. 1, 7!) is much more marked in the Gorilla than in Man; the outer 
condyle (7) is relatively smaller and projects less backward. The popliteal space is 
more shallow and less defined; the intercondyloid space is wider and less deep, and 
its greatest width is anteriorly—the converse of that in Man. The entocondyloid 
tuberosity (k', fig. 1) is less defined and less prominent than in Man. The rotular 
surface is much less concave transversely, and the condyloid convexities less produced 
from before backwards, than in Man; that of the inner condyle (k) is broader than that 
of the outer condyle (i); and the whole distal surface (fig. 3) is relatively broader trans- 
versely, than in Man. 
The femur of the Chimpanzee (PI. VII. fig. 4) is more slender in proportion to its 
length, and is straighter than in the Gorilla. In the smaller proportional size of the head 
of the bone (fig. 5), and in the more backward position of the trochanter minor (e), it 
recedes further from the human femoral type ; but the axis of the neck forms with that of 
the shaft of the bone a less open angle than in the Gorilla. The shaft of the thigh-bone 
is more cylindrical, approaching nearer the shape of that part in inferior Apes. In the 
well-marked surface for the insertion of the ectogluteus muscle, in the origin of the linea 
aspera from the spiral line (fig. 4, g), in the minor production of the ‘linea’ at the middle 
of the shaft, in its continuation to the inner rather than to the outer condyle, in the 
more developed ectocondyloid prominence (i), in the shape and depth of the rotular and 
intercondyloid spaces, and in the proportions of the two condyloid convexities, the 
femur of the Chimpanzee repeats the characters by which the femur of the Gorilla 
departs from the Human type of the bone. 
The thigh-bone in Man hasan articular head (Pl. VIL fig. 7) composed of a larger pro- 
portion of a sphere than in the Gorilla (fig. 2) or Chimpanzee (fig. 6); the depression for 
‘ The idea that the cause of the prerogative of the human organization, for supporting the body in equilibrio 
on one foot only, is to be found “in the length of the cervix femoris,” was formed and expressed before the 
organization of the adults of the genus Troglodytes was known, 
