94 



OSTEOLOGY. 



trochlea consisting of two oblique prominences, separated by a- 

 deep groove, directed downwards and outwards, which corres- 

 pond to the articular surface on the distal end of the tibia. The 

 inferior surface is concavo-convex, and excepting a small oval 

 external portion, which rests on part of the cuboid bone, and a 

 roughened, excavated posterior portion, in which the great inter- 

 osseous ligament is attached, the whole of it articulates with th& 

 superior surface of the cuneiforme magnum. The posterior 

 surface is very irregular, and has four facets, which articulate 

 with the calcaneum, the intervening portion being excavated 

 and roughened. The lateral surfaces, the internal of which pre- 

 sents a tubercle inferiorly, are roughened 

 for the insertion of ligaments. The astra- 

 galus articulates with the tibia and calcan- 

 eum, the cuboid, and great cuneiform bones. 



CALCANEUM. 



(Fig. 22. L) 



The OS calcis or calcaneum, which forms 

 the prominent part, termed the i-)oint of the 

 hock, and corresponds to the heel-bone of 

 man, is situated immediately behind the 

 astragalus, and consists of a body and a 

 tuberosity. The hody is the inferior por- 

 tion, which is flattened laterally, slightly 

 convex externally, and unevenly concave 

 internally, both surfaces being roughened. 

 Anteriorly it has four articular facets, which 

 correspond to those on the astragalus, the interspaces being 

 rough for ligamentous attachment ; posteriorly it is grooved and 

 smooth, for the passage of the deep flexor pedis tendon ; infer- 

 iorly it has two facets to articulate with the cuboid bone. 



The tuberosity is oblong, and flattened laterally, its external 

 surface being rough ; internally it is smooth, and forms the tarsal 

 arch, a groove covered with fibro-cartilage, in which lies the above- 

 named flexor pedis tendon. Both borders are roughened, the 

 posterior one being straight, and giving attachment to the 

 calcaneo-cuboid ligament, while the anterior and shorter one is. 

 curved. The superior extremity is expanded and roughened ; 

 posteriorly it is covered with fibro-cartilage, over which thft 



Fig. 22. 

 Bones of left tarsus of a 

 Horse, seen from the front 

 and outside. 1, Calcaneum ; 

 2, Astragalus ; 3, Cuneiforme 

 magnum: 4, Cuneiforme med- 

 ium : 5, Cuboid. 



