vicular bone.

[Illustration: FIG. 1.--THE BONES OF THE PHALANX. 1, The os suffraginis; 2,
the os coronae; 3, the os pedis; 4, the navicular bone, hidden by the wing
of the os pedis, is in articulation in the position indicated by the barbed
line.]

[Illustration: FIG. 2.--SECOND PHALANX OR OS CORONAE (ANTERIOR VIEW).
1, Anterior surface; 2, superior articulatory surface; 3, inferior
articulatory surface; 4, pits for ligamentous attachment.]

[Illustration: FIG. 3.--SECOND PHALANX OR OS CORONAE (POSTERIOR VIEW). 1,
Posterior surface; 2, gliding surface for passage of flexor perforans; 3,
lower articulatory surface.]

Cubical in shape, it is flattened from before to behind, and may be
described as possessing six surfaces: _An anterior surface_, covered with
slight imprints; _a posterior surface_, provided above with a transversely
elongated gliding surface for the passage of the flexor perforans; _two
lateral surfaces_, each rough and perforated by foraminae, 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
antero-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 foraminae of varying sizes. On each side
of this surface is to be seen a distinct groove, the _preplantar groove_,
or _preplantar fissure_, which, commencing behind, between the basilar and
retrossal processes, runs horizontally forwards from the angles or wings of
the bone, and terminates anteriorly in one