414 THE OSTEOLOGY OF VULPES MACROTIS. 



the articular surface of the tibia, an ossification of the internal inter-articular semi- 

 lunar cartilage," does not appear to be present. A patella of some size, however 

 (8 mm. long), and of an oval form, exists in its usual place in the common extensor 

 tendon at the front of the knee-joint. Its anterior surface is convex and roughened, 

 while posteriorly it presents an articular facet for each femoral condyle. 



Morphologically, the tibia and fibula of the leg are interesting bones. Viewing 

 the former upon its anterior aspect it will be noticed that the upper moiety of the 

 shaft is gently curved in such a manner that it is concave on its outer side and 

 correspondingly convex upon its inner side. Below the middle of the bone it is 

 nearly straight, with a slight inclination, however, to exhibit a curvature the 

 reverse of what has just been described as being found in the upper half. Again 

 the upper half of the tibia is massive and strong, the crest upon its anterior aspect 

 being prominently developed. This feature is most conspicuous above, gradually 

 disappearing as the middle of the shaft is approached, after which this part of the 

 bone is compressed in the antero-posterior direction. A horizontal section made 

 first below the summit would be distinctly triangular, and a similar one made in 

 the lower third would be elliptical. Seen from above the summit of the tibia has a 

 cordate outline, the apex being to the front, and the figure completed by a median 

 notch behind. In this latter locality the margins are curled downward, and par- 

 ticularly so where the fibular articulation is found, so that this facet is beneath this 

 projecting part of the summit of the tibia, and consequently the fibula is shorter 

 than the former bone proximally. 



The tibial shaft is wonderfully smooth, and exhibits longitudinal muscular 

 ridges only at its upper third at the posterior aspect. Distal ly, its extremity is but 

 moderately enlarged, and compressed from before backward. Its basal aspect is 

 peculiarly concaved in order to articulate with the astralagus of the tarsus. This 

 concavity would not be suspected simply by viewing the bone directly from in front, 

 from behind, or from the side, so completely is it on the basal end of the shaft. 

 It is marked by a distinct and deep little notch anteriorly, close to the internal 

 malleolus. 



The fibula is an exceedingly slender bone of uniform calibre, being markedly 

 compressed from side to side, including its extremities, which are rounded and 

 dilated. The upper one of these articulates with the tibia in the manner described 

 above, while the lower one projects beyond the end of the former, where it becomes 

 the external malleolus of the ankle-joint. Owing to the aforesaid curvature of the 

 upper half of the tibial shaft, the fibula stands far apart from its companion in that 

 part of the skeleton of the leg, but below the middle of the shaft, these two bones 

 come in contact, and from this point to the distal fibular enlargement (external 

 malleolus) they are in extremely close contact, probably actually co-ossified in very 

 old individuals. Flower says the " fibula is slender, and in dogs curved towards 

 the tibia, the lower half being closely applied to that bone." This is true only 

 in part, as proximally it is the tibia that is curved away from the fibula, the 

 latter, as has been said, being almost perfectly straight from one end to the other. 



