ANATOMY ND PHYSIOLOGY OF THE HORSE^S FOOT. 179 
jarring which must be greater in a solid than any other kind 
of foot. 
This admirable arrangement of its minute structure in 
layers of varying density, distributed according to the neces- 
sities of the case, is most conspicuous in the centre and ante- 
rior portions of the hoof-bone, the strain being most 
considerable at these parts, the texture is closest; while 
towards the wings or posterior portions, which are behind the 
axis of support, it is light, loose, and expanded, and better 
qualified to assist in lessening concussion when the foot meets 
the ground than in sustaining weight. 
Behind the pyramidal process which surmounts the front 
surface is a large, polished, slightly hollow space (fig. 4, f) for 
articulation with the lower end of the small pastern, and a 
portion of the navicular bones (fig. 4, g ), and on each side 
of this, passing backwards, is a flattened projection of some 
importance, conveniently designated the “ basilar process ” 
or tubercle (fig. 4 i), because it affords a basis for the support 
and attachment of an elastic cartilage situated here ; while 
at the lower side is a rather deep depression (fig. 4 h ), for the 
lodgment and fixation of one of the strong lateral ligaments 
that binds the bone in such a solid manner to the one above 
it. Below and behind these lie the oftentimes variable and 
irregularly shaped wings of the bone, the terminations of 
which have been termed its appendices or retrossal processes 
(fig. 4 /). Above the inner or concave border of the crescent, 
and immediately below the articulating surface, is a space for 
the lodgment of the navicular bone (fig. 5, /), and around 
the anterior edge of this excavation is seen a roughened 
surface, the semilunar ridge (fig. $, d), for the insertion of 
the powerful fibres of the large tendon that flexes the foot 
and assists in maintaining the angle of the pastern, while 
the animal is in a standing attitude. 
Exactly in the middle of the lower convex border — at the 
toe or front of the os pedis — there is often, though not inva- 
riably, a small indentation (fig. 5, e ) , which looks as if the 
bone had been notched, and sometimes a shallow narrow 
groove or faint depression extends from this up towards the 
pyramidal process. The extent of the notch when present 
varies in depth and width not only in animals of the same age, 
but in those of different ages, being in many young horses 
scarcely perceptible, and in others rather conspicuous, and 
nearly always increasing apparently as they advance in years. 
This indentation has been thought to mark the transition 
from didactylous to monodactylous animals, but I cannot help 
thinking that the manner of applying the toe-clip of the shoe 
