OSTEOLOGY. 93 



attacliment of interosseous ligaments. Along tlie anterior 

 margin may be seen a small facet looking inwards, con- 

 tinuous with a large one upon the margin looking forwards, 

 the rest of this margin is rough. The inferior margin is 

 mainly occupied by an irregular slightly concave articu- 

 latory surface for os cuboides, this is continued slightly 

 on to the internal surface at its inferior point as a small 

 facet for union with astragalus. From the siq^erior mar- 

 gin the process runs upwards. The loosterior margin is 

 continuous with the posterior margin of the process and 

 both are rounded and roughened for attachment of the 

 €alcaneo- cuboid ligament. The sujjerior extremity of the 

 process is tuberous, slightly inclined forwards. Anteriorly 

 it presents a smooth surface for a bursa, over which gastro- 

 cnemius extemus plays, becoming inserted just behind, 

 while still farther back this surface is smooth for the 

 bursa situated on the point of the hock, where the expanded 

 tendon of gastrocnemius internus forms a cap for it, be- 

 coming attached by a fibrous band running to the process 

 on either side. The anterior margin is thinner than the 

 posterior but rounded. The external surface is subcu- 

 taneous. The internal surface coated with fibro-cartilage, 

 continuous with that on the oblique posterior part of the 

 inner prommence of the body, over which the perforans 

 tendon plays, bound down by the posterior annular ligament. 

 OS ASTRAGALUS is a square bone at the inner part of 

 the upper row of the hock bones. It articulates superiorly 

 with the tibia, posteriorly with calcis, inferiorly with 

 cuneiforme magnum and cuboides. It has five surfaces. The 

 antero-superior surface presents two prominent rounded 

 articular ridges, running obliquely downwards and out- 

 wards. The inner ridge is the longest, and its inner side 

 the straightest, and completely coated with cartilage. It 

 extends beyond the outer, both anteriorly and posteriorly. 

 The outer ridge curls slightly outwards at its inferior 

 extremity, and is separated from the inner by a deep syno- 

 vial fossa, which is shorter than either of the grooves, and 

 generally presents a break in the articular cartilage cen- 

 trally. Between it, the grooves, and the inferior surface, 

 is a triangular depression, roughened for attachment 

 of extensor pedis accessorius. The ]}osterior surface of 

 the bone is extremely irregular. Internally it presents 

 superiorly a roughened prominence, and below this the 



