PELVIC LIMBS 749 



the groove which separates them. The fibular margin is well defined 

 and runs straight forward from its proximal half, and is produced 

 laterally near the distal end hy the peroneal tubercle, beyond which 

 it is emarginate and directed obliquely to the tibial side. The distal 

 margin is prominent and arcuate, and passes obliquely to the tibial 

 and proximal sides. The tibial margin is limited by the prolongation 

 forward of the tibial articular facet already described. This part of 

 the dorsal surface is rough and concave, and faces dorsally and to the 

 tibial side. A decided groove runs near the fibular border and parallel 

 with it and affords origin to the extensor brevis digitorum muscle, and 

 by a pit at the proximal end receives the insertion of the annular liga- 

 ment for the extensor longus digitorum. 



The fibular or external surface (Fig. 566) is high from the dorsal 

 to the plantar border in its proximal two-thirds, and low in its distal 

 third. The proximal margin is rounded, passing below into the outer 

 tuberosity and above into the sharp proximal margin of the dorsal 

 surface. Its dorsal margin, beginning at the proximal end, is at first 

 emarginate, then arcuate, then turns abruptly to the plantar, distal, and 

 fibular sides, and is continued for the rest of its length as a straight 

 and prominent border. At its distal end is a flat projection, whereof 

 the plantar surface is crossed by a deep groove passing obliquely from 

 the border distally and to the tibial side. The projection is called the 

 peroneal tubercle, and the groove transmits the tendon of the peroneus 

 longus muscle. There is no decided plantar margin, inasmuch as the 

 fibular surface passes without a definite line into the plantar surface. 

 The proximal part of the fibular surface is prominent and known as 

 the outer tuberosity; distal to which, however, it is concave in both 

 directions, and often marked by a distinct pit for the insertion of a part 

 of the external lateral ligament. When the bone is in position, this 

 part of the fibular surface faces nearly directly outward. The distal 

 part of the surface is limited to the border ; all that part beneath is 

 regarded as part of the plantar surface. 



The tibial or internal surface (Fig. 561) in its proximal two- 

 thirds resembles in shape the corresponding part of the fibular surface. 

 It is strongly concave from the proximal to the distal end to permit 

 the passage of the flexor tendons from the back of the ankle to the 

 sole of the foot. At its highest point at the distal end is seen part of 

 the fibular articular facet for the astragalus. At the junction of the 



