12 DISEASES OF THE HORSE’S FOOT 
Tue Navicunar Bonz, SxutrLe Bons, on Smauu Susa- 
morD.—Placed behind the articulating point of the second 
and third phalanges, this small shuttle-shaped bone assists 
in the formation of the pedal articulation. It is elongated 
transversely, flattened from above to below, and narrow at 
its extremities. In it we see two surfaces, and two borders. 
The Superior or Articular Surface of the bone, which may 
easily be recognised by its smoothness, is moulded upon 
the lower articular surface of the second phalanx, being 
convex in its middle, and concave on either side. 
The Inferior or Tendinous Surface resembles the pre- 
ceding in form, but is broader and less smooth. In the 
recent state it is covered with fibro-cartilage for the passage 
of the flexor perforans. 
The Anterior Border possesses above a small trans- 
versely elongated facet for articulation with the os pedis, 
and below a more extensive grooved portion, perforated by 
numerous foramine, affording attachment to the inter- 
osseous ligaments of the articulation. 
The Posterior Border, thick in the middle, but thinner 
towards the extremities, is roughened for ligamentous 
attachment. 
Development.—The bone ossifies from a single centre. 
B. THE LIGAMENTS, 
Tue ARTICULATION OF THE First wiTH THE SECOND 
PHALANX, OR THE Pasrern Jornt.—Adhering to the limit we 
have set, this articulation should not receive our attention. 
As, however, we shall in a later page be concerned with 
fractures of the os corone, which fractures may affect the 
articulation above mentioned, a brief note of its formation 
will not be out of place. 
It is an imperfect hinge-joint, permitting of extension and 
flexion, allowing the first phalanx to pivot on the second, 
and admitting of the performance of slight lateral move- 
ments. It is formed by the opposing of the inferior surface 
of the os suffraginis with the superior surface of the os 
corone. The articulating surface of the os corone is 
