166 



THE SKELETON 



The internal surface presents near its middle and upper part an oval faeet for 

 articulation with the external cuneiform lione (fig. 172); behind this, a second facet 

 for the scajihoid is freciuentlv seen (fig. 173). Generally the two facets are con- 

 tinent and form an elliptical" surface (fig. 174). The remainder of the internal 

 surfact^ is rough, and has strong interosseous ligaments attached to it. 



Jutting from the inferior internal angle of the posterior surface is a process of 

 l)(»n(' ( calcanean process of cuboid), which projects beneath the sustentaculum tali. 

 This process occasionally terminates in a rounded facet, which plays on the head 

 of the astragalus external to the facet for the S])ring ligament. 



Articulations. — The cuboid articulates Avith the calcaneum, the external cunei- 

 form, the fourth and fifth metatarsal bones, frequently with the scaphoid, and 

 occasionally with the astragalus. 



Muscles attached to the cuboid : — 



Tibialis posticus. 



Flexor brevis hallucis. 



Ligaments :- 



.Superior calcaneo-cuboid. Inferior calcaneo-cuboid. 



Interosseous and the cubo-scaphoid ligaments. 



Ossification. — The cuboid is ossified from a single centre which appears a few 

 weeks after birth. Occasionally the nucleus is visible as a minute earthy spot in the 

 middle of the cartilage at l)irth. 



THE SCAPHOID 



The scaphoid (navicular) lH)ne receives in the hollow of its posterior surface 

 the head of the astragalus. Anteriorly it is convex, and divided by tAvo vertical 

 ridges into three facets, for the internal, middle, and external cuneiform bones. 



Fig. 175. — The Left Scaphoid. (Anterior view.) 



FOR INTERNAL CUNEIFORM 

 INNER BORDER 



TUBEROSITY 



FOR MIDDLE CUNEIFORM 

 OUTER BORDER 



FOR EXTERNAL CUNEIFORM 



Occasionally a fourth facet, extremely varial)lc in size, is seen at the outer inferior 

 angle for the culxjid. 



The upper (dorsal) surface is rough and broad; the inferior (plantar) surface 



Fi(i. 17().— The Left Scaphoid, showing a Facet fok the Cuboid. 



FOR INTERNAL CUNEIFORM 



FOR MIDDLE CUNEIFORM 



FOR EXTERNAL CUNEIFORM 

 FOR CUBOID 



is nothing more than a ridgo. The outer surface is rougli for ligaments; whilst 

 the inner forms a large and i)rominent eminence, the scaphoid tuberosity, which 

 affords an important attachment for the tibialis posticus tendon. 



