70 OUTLINES OF EQUINE ANATOMY. 



inner is the largest in every respect. Viewed from behind 

 forwards it is posteriorly convex, anteriorly concave. It 

 posteriorly slightly extends on to the back of the bone. 

 It articulates with os scaphoides. Its anterior, posterior, 

 and inner margins aiford attachment to the radio-carpal 

 capsular ligament. Its outer abruptly bends upwards 

 posteriorly in commencing the articulatory surface for os 

 hmare or middle sujface, which, after running upwards for 

 a short distance at the posterior pp.rt, bends outwards, thus 

 producing a convexity posteriorly, a concavity anteriorly, 

 separated from the anterior concavity of the scaphoid sur- 

 face by a slightly prominent articular ridge. It decreases 

 in size from its inner to its older margin, and is there con- 

 tinuous with the small convex articulatory surface which 

 extends on to the posterior surface of the bone, awd comes 

 anteriorly in contact with the cuneiform bone posteriorly 

 with trapezium. The posterior surface of the bone above 

 this articulatory portion presents a roughened prominence, 

 separated from the middle articulatory facet by a deep 

 fossa. This affords attachment to the thick posterior 

 annular ligament of the knee. Each side presents a pro- 

 minence, the inner is the largest, for attachment of a 

 lateral ligament of the knee. The outer prominence is 

 divided into two parts by a groove running from above 

 downwards, through which extensor suffraginis plays, 

 bound down by the annular ligament. The anterior sur- 

 face inferiorly presents four prominences for attachment 

 of the annular ligament, and three intervening grooves. The 

 outer groove gives passage to extensor pedis tendon, the 

 central to extensor metacarpi magnus, the internal runs 

 obliquely inwards and downwards as far as the articular 

 surface, and gives passage to extensor metacarpi obliquus. 

 The ULTTA is attached (as above described) to the pos- 

 tero-external ])art of the radius, superiorly by two small 

 synovial articulatory facets connected with the synovial sur- 

 face of the elbow- joint. Below this by a fibrous articulation, 

 and at the lowest part by an ossific union, and between the 

 ossific and the fibrous portion is the radio-ulnar arch. The 

 ulna is divided into a free and an attached portion. The 

 attached portion is prismatic, largest superiorly, and from 

 this tapers downwards, terminating insensibly, blending 

 with the outer edge of the posterior surface of the radius at 

 the superior part of the inferior third. The outer surface 



