10 DISEASES OF THE HORSE'S FOOT 



posterior region, lying immediately behind the semilunar 

 crest, shows on each side of a median process a large 

 foramen, the Plantar Foramen. From this foramen runs 

 the Plantar Groove, a channel, bounded above by the 

 superior edge, and below by the semilunar crest of the 

 bone, which conducts the plantar arteries into the Semi- 

 lunar Sinus, a well-marked cavity in the interior of the bone. 



The Superior or Articular Surface consists of two shal- 

 low depressions, divided by a slight median ridge. Its 

 posterior part shows a transversely elongated facet for 

 articulation with the navicular bone. 



The Superior Edge, outlining the superior margin of the 

 laminal surface, describes a curve, with the convexity of 

 the curve forward. In the centre of the curve is a tri- 

 angular process, the Pyramidal Process, which serves as 

 the point of attachment of the extensor pedis. 



The Inferior Edge, the most extensive of the three, 

 separates the laminal from the solar surface. It is semi- 

 circular in shape, sharp, and finely dentated, and is per- 

 forated by eight to ten large foraminae. 



The Posterior Edge, very slightly concave, divides the 

 small, transversely elongated facet of the superior surface 

 from the posterior region of the inferior surface. 



The Lateral Angles of the bone, also termed the Wings, 

 are two projections directed backwards. Each is divided 

 b\ a cleft into an upper, the Basilar Process, and a lower, 

 the Retrossal Process. In old animals the posterior portion 

 of the cleft separating the two processes gradually becomes 

 filled in with bony deposit, thus transforming the cleft into 

 a foramen, which gives passage to the preplantar artery. 

 We may mention in passing that the lateral angles give 

 attachment to the lateral fibro-cartilages, and that the 

 lateral angles themselves in old horses become increased 

 in size owing to ossification of portions of the adjacent 

 lateral cartilages. 



Development. — The os pedis ossifies from two centres, 

 one of which is for the articular surface ; but this epiphysis 

 fuses with the rest of the bone before birth. 



