68 THE SURGICAL ANATOiMY OF THE HORSE 



remainder of this surface is smooth and blends with the posterior 

 surface. This is the surface which forms the anterior boundary of the 

 tube through which the perforans tendon plays at the tarsus. 



The lateral surfaces of the body are roughened for ligamentous 

 attachment. 



The tuber is a massive piece of bone which projects upwardly from 

 the outer portion of the body. It presents two surfaces, two borders, 

 and a summit. The outer surface is almost flat. The inner surface is 

 slightly concave and is smooth. This surface forms the outer boundary 

 of the tarsal sheath. The anterior border is curved in its length, with 

 the concavity directed forwards. It terminates inferiorly in a pro- 

 jecting, peak-like process. The posterior border is much thicker and 

 longer, and is almost straight. To it is attached the thick calcaneo- 

 metatarsal ligament. The summit of the tuber forms the point of the 

 hock in the living animal, and corresponds to the human heel. It 

 presents a central, roughened depression, in which the tendon of 

 the gastrocnemius muscle is inserted. In front of this is a convexity 

 upon which this tendon rests when the hock is flexed. Behind the 

 depression is another, much larger convexity. This is smooth, and over 

 it the tendon of the flexor perforatus muscle plays. Between this tendon 

 and the bone there is interposed a small synovial bursa. 



The Scaphoid. — This bone is placed between the astragalus and the 

 cuneiform magnum. It is flattened from above to below, and may be 

 said to have two surfaces and four edges. The superior surface is 

 slightly concave. It presents a large facet for articulation with the 

 astragalus. A non-articular area runs from the centre of the bone 

 outwardly. This area gives attachment to the astragalo-scaphoid 

 interosseous ligament. The inferior surface is slightly convex, and for the 

 most part smooth and articular. The larger portion of the smooth area 

 articulates with the cuneiform magnum, but postero-internally the bone 

 presents a small convex facet which articulates with the cuneiform 

 parvum. For the rest of its extent the inferior surface is roughened 



