174 ANATOMY AND PHYSIOLOGY OF THE HORSE J S FOOT. 
external envelope to be examined subsequently. We will 
adopt the latter course, as it is one with which we are best 
acquainted, and perhaps it offers the greatest facilities for 
making the description of the foot most readily understood.* 
The Bones of the Horse’s Foot. — The bones of the foot, look- 
ing at it as limited to the very extremity of the limb, are 
three in number, viz., the middle, small pastern bone, or 
second phalanx, which corresponds to the second digital 
phalanx of man's hand or foot ; the pedal, distal, ungual bone 
or third phalanx, which may be compared to the terminal 
finger or toe bone, with its nail attached ; and the navicular 
or inferior sesamoid bone, which has no counterpart in the 
human hand or foot. 
Small Pastern Bone. — This bone (fig. 3, c) is also named 
the second phalanx , os corona , or crown bone , and is situated 
partly above and partly below the upper margin of the hoof, 
inclining in a more or less oblique direction, from above 
forwards, following the same angle of inclination as the bone 
above it — the large pastern bone (fig. 3, a). Its structure 
is exceedingly dense, and capable of withstanding a great 
amount of strain, its outer or cortical texture being a very 
thick and compact layer of bony matter, while its interior or 
cancellated structure is remarkable for its vascularity. In 
shape it is somewhat square and short ; a cursory glance at 
it would at once demonstrate that it was specially adapted 
for strength and stability, fitted to sustain weight and support 
the attachment of powerful ligaments. At its upper ex- 
tremity are two smooth, concave depressions or glenoid 
cavities, separated by a slight middle ridge, and covered with 
elastic cartilage to facilitate movement and diminish concus- 
sion. This extremity is adapted for articulation with the 
lower or convex extremity of the first phalanx. The inferior 
end of the bone is the reverse of the upper in being convex, 
and slightly depressed from before to behind in its middle, 
to articulate somewhat extensively with the pedal and navicu- 
lar bones, through the medium of the articular cartilage 
covering their surfaces of contact. The upper part of its 
posterior surface shows a smooth fibro-cartilaginous patch, 
over which glides the large flexor tendon of the foot — the 
perforans or profundus. At each side of this portion, the 
* As before remarked, I have refrained from entering at any considerable 
length into the details of descriptive anatomy when speaking of the structure 
and composition of the horse’s foot. Those who are desirous of becoming 
thoroughly acquainted with these I would refer to the classical and unequalled 
monograph by M. H. Bouley — the ‘Traite le ^Organisation du Pied du 
Cheval.’ Paris, 1851. 
