THE TARSUS. 



131 



part, between this and the anterior articulation with the os calcis, is a facet which 

 rests upon the internal calcaneo-navicular ligament, the three forming one con- 

 tinuous articular surface. The posterior surface is of small extent, and marked at 

 its inner part by a groove for the flexor longus hallucis, which is continuous below 

 with that of the sustentaculum tali. Bounding the groove are two tubercles, of 

 which the internal is usually but little marked; while the external is more prominent 

 and gives attachment to the posterior band of the external lateral ligament of the 

 ankle-joint. 



The navicular or scaphoid bone is placed at the inner side of the foot 

 between the astragalus and the cuneiform bones. It is elongated transversely, and 

 compressed from before backwards. It presents 

 posteriorly an articular concavity for the head of 

 the astragalus, and anteriorly a convex surface 

 divided by two lines converging below into three 

 facets, which articulate respectively with the three 

 cuneiform bones. Its upper surface is convex 

 from side to side ; the lower is narrower and very 

 uneven. On the outer end there is in some 

 instances a small articular surface for the cuboid 

 bone ; the inner end forms the prominent tube- 

 rostty, directed downwards, and giving insertion 

 to the tendon of the tibialis posticus muscle. 



The cuneiform bones are known as first, 

 second, and third, from within outwards, or in- 

 ternal, middle and external. They are placed between the navicular bone and the 

 inner three metatarsal bones, and present anteriorly and posteriorly smooth surfaces 

 for articulation with those bones. The internal cuneiform bone is the largest, the 



A. 



Fig. 147. RIGHT NAVICULAR BONE, 



FROM BEFORE. (Gr. D. T.) 



Fig. 148. RIGHT INTERNAL CUNEIFORM BONE : A, INNER VIEW ; B, OUTER VIEW. (G-. D. T.) 



middle is the smallest. The proximal ends of the three bones are in the same trans- 

 verse line ; but at their distal ends the internal and external project forwards 

 beyond the middle one, and thus form a deep recess into which the base of the 

 second metatarsal bone is received. 



The internal cuneiform bone has its sharp border directed upwards, and 

 the thick rounded base of the wedge projects downwards on the inner border of 

 the foot. The anterior articular surface, for the first metatarsal bone, is much 

 larger than the posterior, is kidney-shaped and convex. The internal surface is 

 free, rather uneven, and marked by an oblique groove for the tendon of the tibialis 

 anticus muscle, ending below in an oval facet where the larger part of the tendon is 

 inserted. On the outer side, along the posterior and superior borders, is an L-shaped 

 surface, which articulates with the middle cuneiform, and at its anterior extremity 

 with the second metatarsal bone. 



K 2 



