78 OUTLINES OF EQUINE ANATOMY. 



for tlie most part smooth, and is separated from tlie skin 

 only by tlie expanded tendons of extensor pedis and 

 extensor snffraginis, wliicli run from above downwards 

 inclined to the outer side, and are closely connected to- 

 gether. At its extreme superior part it presents a groove 

 marking out the limit of the superior articulatory surface, 

 and below this is roughened, especially on the inner side, 

 where is a roughened prominence for attachment of ex- 

 tensor metacarpi magnus. The j^osterior surface is flattened, 

 and on either side presents a roughened surface for attach- 

 ment of the metacarpal interosseous ligaments, binding the 

 small to the large bone. These surfaces are widest supe- 

 riorly and inferiorly, taper to a point slightly con- 

 verging, extendmg to about the inferior part of the middle 

 third of the bone. The space between them is concave, 

 and at the inferior part of the superior third inclined to 

 the inner side presents the medullary foramen, through 

 which a branch of the small metacarpal artery runs to 

 supply the bone. The extreme superior part of this 

 surface affords attachment to the superior extremity of the 

 superior sesamoideal ligament, the anterior surface of 

 which lies in contact with the greater part of the rest of 

 this surface, which, superiorly convex, at the lower part of 

 the middle third becomes concave centrally, agam be- 

 coming 2:>romment, especially along the middle line in 

 reaching the inferior articulatory surface. Here it is 

 pierced by a row of articular foramina. The margins of 

 the bone superiorly are roughened for attachment of the 

 capsular (car po -metacarpal) and annular ligaments of the 

 knee, centrally are smooth, forming with the small meta- 

 carpals grooves running from above downwards. Infe- 

 riorly they are rough for attachment of a ligament from 

 the inferior extremity of the small metacarpal bone, and 

 one from the lateral part of the sesamoid bone, and below 

 this present each side a rounded concavity for attachment 

 of the lateral ligaments of the fetlock. The tijpper surface 

 of the bone presents four distinct articulatory facets. One 

 is by far the largest and slants obliquely inwards, and 

 occupies the inner two -thirds of the surface. It articu- 

 lates with OS magnum and presents four margins. The 

 anterior margin has two convexities and extends farthest 

 backwards on the inner side, and there meets the inner 

 margin which runs obliquely from within outwards 



