74 OUTLINES OF EQUINE ANATOMY. 



tinuous with the articulatoiy surface on its superior margin ; 

 one inferioiiy, separated by a roughened space from the 

 anterior margin, continuous with the articulatorj surface 

 of the inferior margin. Between and behind these this 

 surface is roughened for attachment of interosseous liga- 

 ments, posteriorly it terminates in a point. The superior 

 margin presents a smooth triangular concave surface for 

 articulation with the radius continuous with the superior 

 one on the internal surface for lunare. T]iq inferior surface 

 or margin presents an articulatory surface with the unciform, 

 which anteriorly is concave, posteriorly at the external side 

 convex. It is continuous with the inferior facet on the 

 inner surface for lunare. It is separated by a roughened 

 space from the ]30sterior margin, which presents a concave 

 ovoid articulatory surface extending obliquely forwards 

 and u^^wards ; with this the inferior articulatory surface of 

 trapezium comes in contact. It is separated from the 

 inferior articulation by a roughened dexn'ession, to which 

 its capsular ligament is attached. The anterior margin of 

 the bone is also roughened for ligamentous attachment. 



OS TRAPEZIUM is situated at the postero-external part 

 of the upper row. It is flattened from side to side, and 

 slightly curved inwards. It presents two surfaces and four 

 margins. The anterior margin has two articulatory facets, 

 the superior concave for articulation with the radius, and 

 extending on to the internal surface of the bone. It is sepa- 

 rated by a deep perforated groove from the inferior facet, 

 which is below and slightly externally placed, convex for 

 articulation with cuueforme ; internally placed to this the 

 anterior margin is rough. The superior and inferior margins 

 are rough, and extend from the anterior to the posterior 

 margin. The superior is sharpest, and from about its centre 

 over the external surface of the bone a roughened groove 

 extends towards the infero- anterior articulatory facet. 

 Flexores metacarpi externus et medius are attached to the 

 upper margin, and through the groove on the external sur- 

 face a rounded tendon of flexor metacarpi externus runs to 

 the outer small metacarpal bone. This groove presents a 

 prominent roughened edge, separating it from a depression ; 

 the rest of the external surface is convex and roughened for 

 attachment of the annular ligament, which is also attached 

 to the inferior margin and to the posterior margin, which 

 is rounded and rough. The internal surface is concave and 



