382 THE ANATOMY OF THE HORSE 



The base is surmounted by a smooth articulatory surface, surrounded 

 iuferiorly by roughened tuberosities, except anteriorly, where two smooth 

 articular surfaces occur, which articulate with corresponding surfaces 

 mentioned as existing on the metacarpus magnus. 



The body is trifacial. The anterior surface is rough, and articulates 

 with the metacarpus magnus. The inner surface is excavated. The outer 

 surface is convex and smooth. The apex terminates in a bulbous extremity, 

 which looks posteriorly, and does not articulate with the metacarpus magnus. 



THE PHALANGEAL BONES (PASTERNS AND 

 FOOT) 



Beyond the metacarpus in the horse, there is only a single bone in each 

 joint, the five fingers being merged in one. The same number of phalanges, 

 however, is maintained, counting from the metacarpus to the distal phalanx, 

 which is the pedal bone. The whole may, therefore, be considered as 

 analogous to one human finger, with the addition of the two sesamoid bones, 

 and the navicular bone, all three of which are intended to assist in giving 

 leverage to the tendons moving these parts. The highest of these is the 

 OS suffroginis or larger pastern, the next the os co7'ona or lesser pastern, and 

 the lowest the os jj^dis or coffin-bone. 



The Os Suffraginis and its Ossa Sesamoidea 

 may be taken together, the latter lying on each 

 side of the back of its superior extremity, but play- 

 ing only on the large metacarpal. They are separately 

 shown at Fig. 30. The os suflfraginis has a body and 

 two extremities. 



The body shows an anterior surface, which is con- 

 -OssA Sesamoidea. ^^^ ^^^ smooth ; and a posterior which is rough and 

 flattened, and presents superiorly a triangular space, 

 bounded lateral!}^ by two roughened ridges, which meet at a point inferiorly. 

 The superior extremity presents two shallow concavities, which are 

 separated one from the other by a deep transverse canal. Behind these 

 concavities, two tuberosities exist for the attachment of the crucial 

 ligaments. 



The inferior extremity has two semi-cylindroid convexities, divided 

 transversely by a shallow depression, which is widened posteriorly. 



Os CoRONiE (corona, a coronet) is in form a parallelogram with four 

 surfaces. 



The anterior surface is convex and roughened, presenting two tuber- 

 osities below. 



The posterior surface is smooth, and has superiorly a semilunar smooth 

 surface. 



The superior surface presents two ovoid concavities, divided by an 

 eminence running from behind forwards, and bounded, anteriorly and 

 posteriorly, by two roughened projections. These form the lesser fetlock 

 joint with the bone above. 



The inferior surface i^esembles the corresponding part of the oa 

 sufFraginis. 



