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 shallow 
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 triangular 
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 foramine. 
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 
-by 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. 
