REGIONAL ANATOMY 9 
gliding surface for the passage of the flexor perforans ; 
two lateral surfaces, each rough and perforated by foramine, 
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 Tuarrp Puauanx, Os Penis, on Corrin Bonz.—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 foramine 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 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 the sensitive lamine. 
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 foramine; in this case more minute. In 
the recent state it is covered by the sensitive sole. The 
