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 (PI. VII. fig. ],</), 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 (/) 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 theentocondyloid prominence (h'). There is no ridge continued from the linea aspera 

 to the outer condyle, as in Man ; that ridge (PL VII. fig. 6, g, 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, i') is much more marked in the Gorilla than in Man ; the outer 

 condyle (i) 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 (/c) 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 has an articular head (PI. VII. 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 aduhs of the genus Troglodytes was known. 



