36 EQUINE ANATOMY. 



THE FOOT. 



This is divided into the taisus, metatarsus and bones of the 

 digit. 



THE TARSUS. 



The tarsus corresponds to the carpus of the anterior foot, and 

 consists of six or seven segments. 



These segments are divided into two rows : an upper and lower. 

 In the former, in front, is the astragalus, behind the os calcis ; in 

 the latter, outside, is the cuboid, inside, above, the scaphoid, be- 

 low the large and small cuneiforms. There are sometimes three 

 cuneiforms, making seven segments. 



THE ASTRAGALUS. 



The astragalus lies between the tibia above, the scaphoid be- 

 low, and the calx behind. 



It has external and internal rough faces, a posterior with facets 

 for the OS calcis, an inferior convex for the articulation with the 

 scaphoid and a superior and anterior with two articular elevations 

 and a depression for the tibial articular surface. 



Articulations, 4. 



Tibia, os calcis, scaphoid and cuboid. 



THE OS CALCIS OR CALCANEUS. 



The OS calcis is elongated, lying behind the astragalus, above 

 the cuboid, and forming the summit of the tarsus. It shows — 



A convex outer su7face and concave inner, forming the tarsal 

 arch. 



A concave anterior and thick posterior border. 



A superior extremity with a rough spot for insertion of the gas- 

 trocnemius, a smooth surface on which the tendon plays, and be- 

 hind another for the gliding of xhQ petforatus. 



The inferior extremity shows articular facets for the astragalus 

 and cuboid. 



Articulations, 2. 



Astragalus and cuboid. 



I'he cuboid is irregularly quadrilateral in shape, and articulates 

 with the calcaneus, astragalus, scaphoid, jniddle and external 

 metatarsals, and large cuneiform. 



