PELVIC LIMBS 



761 



FIG. 577. 



THE ECTOCUNEIFORM. 



General Description. The Ectocuneiform is placed about in the 

 centre of the distal row of tarsal bones (Fig. 577). It may be said to 

 be in the main axis of the foot, inasmuch as distal to it lies the prin- 

 cipal digit, to which the direct weight of the body is transmitted 

 through the ectocuneiform, the scaphoid, the 

 astragalus, and the tibia. This cuneiform is 

 easily distinguished from the other cuneiforms 

 by its superior size and complexity, and from 

 the cuboid by the absence of the block-like 

 form and deep groove of the latter. 



The ectocuneiform is prismatic, one side of the 

 prism forming the dorsaj surface and the other 

 two sides forming the lateral surfaces ; at the 

 proximal and distal ends it is cut off squarely ; 

 the plantar aspect is produced into a promi- 

 nent vertical hook, whereof the concave side 

 faces toward the digits and holds in place the 

 tendon of the peroneus longus on its way to 

 insertion on the first rudimentary metatarsal. 

 The ectocuneiform presents five surfaces, the 

 dorsal, the tibial, the proximal, the distal, and 

 the fibular. Of these the dorsal is non-articular, 

 and the other four articulate with contiguous 

 bones. The end of the plantar hook is the only 

 true plantar surface. 



The proximal surface (Fig. 578) is trian- 

 gular, with the base of the triangle formed by 

 the dorsal border and the sides by the tibial and 

 fibular borders, which meet below at the rounded 

 apex. The base is about as long as a line drawn 

 from the base to the apex. The dorsal margin 



is gently and regularly arched ; the lateral borders are slightly arcuate 

 above the middle, while below they are nearly straight and directed 

 obliquely to the middle line. The dorso-tibial angle is more promi- 

 nent than the dorso-fibular. 



The proximal surface is entirely occupied by one facet, which is 

 large, triangular, and smooth for articulation with a facet on the dorsal 



POSITION OF ECTOCUNEI- 

 FORM. 



