REGIONAL ANATOMY 9 



gliding surface for the passage of the flexor perforans ; 

 Uvo lateral surfaces, each rough and perforated by fora- 

 mina?, and each bearing on its lower portion a thumb-like 

 imprint for ligamentous attachment, and for the insertion of 

 the bifid extremity of the perforatus tendon ; a superior 

 surface, bearing two shallow articular cavities, separated by 

 an anterior-posterior ridge, for the accommodation of the 

 lower articulating surface of the first phalanx ; an inferior 

 surface, also articulatory, which in shape is obverse to the 

 superior, bearing two unequal condyles, separated by an ill- 

 defined antero-posterior groove, which surface articulates 

 with the os pedis and the navicular bone. 



Development. — The bone usually ossifies from one centre, 

 but often there is a complementary nucleus for the upper 

 surface. 



The Third Phalanx, Os Pedis, or Coffin Bone. — This 

 also belongs to the class of short bones. It forms the 

 termination of the digit, and, with the navicular bone, is 

 included entirely within the hoof. For our examination it 

 offers three surfaces, two lateral angles, and three edges. 



The Anterior or Laminal Surface, following closely in 

 contour the wall of the hoof, is markedly convex from side 

 to side, nearly straight from above to below, and closely 

 dotted with foramina? of varying sizes. On each side of 

 this surface is to be seen a distinct groove, the pre plantar 

 groove, or pre plantar fissure, which, commencing behind, 

 between the basilar and retrossal processes, runs hori- 

 zontally forwards from the angles or wings of the bone, and 

 terminates anteriorly in one of the larger foramina?. As 

 the name ' laminal ' indicates, it is this surface which in 

 the fresh state is covered by a sensitive lamina?. 



The Inferior or Plantar Surface, hollowed in the form of 

 a low arch, presents for our inspection two regions, an 

 anterior and a posterior, divided by a well-marked line, the 

 Semilunar Crest, which extends forward in the shape of a 

 semicircle. The anterior region, as is the laminal surface, 

 is covered with foramina? ; in this case more minute. In 

 the recent state it is covered bv the sensitive sole. The 



