Below the carpal and tarsal joints, the fore and hind limbs correspond almost exactly in structure as well as function.
The ulna is curved and rather stout; it articulates with both carpal bones; the cubital quills often cause rugosities on its dorsal surface.
R', u', Radial and ulnar carpal bones; with the three digits I., II., III.
The flexor digitorum sublimis muscle arises fleshy from the long elastic band which extends from the inner humeral condyle along the ventral surface of the ulna to the ulnar carpal bone, over which the tendon runs to insert itself on the radial anterior side of the first phalanx of the second digit.
The carpal joint, corresponding to the wrist of man, is commonly called the " knee " of the horse, the joint between the metacarpal and the first phalanx the " fetlock," that between the first and second phalanges the " pastern," and that between the second and third phalanges the " coffin joint."
In the fore-limb the upper and lower series of carpal bones scarcely alternate, but in the hindfootthe astragalus overlaps the cuboid, while the fibula, which is quite distinct from the tibia(as is the radius from the ulna in the fore-limb), articulates with both astragalus and calcaneum.
Its plumage is plain in colour, being of an almost uniform greyish black above, the space round the eyes and a ring round the neck being variegated with white, and a patch of pale rufous appearing above the carpal joint, while the lower parts of the body are white.
From the carpal joint to the tip. The top of the head is white, bounded by black, which, beginning in stiff bristly feathers turned forwards over the base of the beak, proceeds on either side of the face in a well-defined band to the eye, where it bifurcates into two narrow stripes, of which the upper one passes above and beyond that feature till just in front of the scalp it suddenly turns upwards across the head and meets the corresponding stripe from the opposite side, enclosing the white forehead already mentioned, while the lower stripe extends beneath the eye about as far backwards and then suddenly stops.