; DISEASES OF THE FETLOCK, ANKLE, AND FOOT. 397 
The flexor pedis perforans, or deep flexor of the foot, passes down 
behind the cannon bone, lying against the suspensory ligament in 
front, crosses the fetlock joint in the groove made by the union of 
the two sesamoids, and is attached to the bottom on the coffin bone, 
after covering the navicular, by a wide expansion of its fibers. It is 
the function of this tendon to flex the coffin bone and, with it, the 
horny box. 
The flexor pedis perforatus, or superficial fico of the foot, follows 
the course of the preceding tendon and is attached to the middle of 
the ankle. The function of this tendon is to flex the foot at the 
fetlock. 
The extensor pedis runs down in front of the leg, is attached on 
the most prominent point of the coffin bone, and has for function the 
straightening of the bones of the ankle and foot. 
The bones, ligaments, and tendons are covered by a loose connective 
tissue, which gives a symmetry to the parts by filling up and round- 
ing off, and all are protected by the skin and hoof. 
The skin of the fetlock and ankle is generally characterized by its 
thickness and the length of its hairs, especially around the hind parts 
of the fetlock joint in certain breeds of horses. The most important 
part of this envelope is that known as the coronary band. 
The coronary band is that portion of the skin which secretes the 
horn of which the wall of the hoof is made. This horn much resem- 
bles the nail which grows on the fingers and toes of man. It is com- 
posed of cylindrical tubes, whith are held together by a tenacious, 
opaque matter. The horn extends from the coronary band to the 
lower border of the hoof. (Plate XX XTI, fig. 1.) 
The hoof is a box of horn, consisting of a wall, sole, and frog, and 
contains, besides the coffin, navicular, and part of the small pastern 
bones, the sensitive lamine, plantar cushion, and the lateral cartileges. 
(Plate XX XIII, fig. 4.) 
The sole of the foot incloses the box on the ground surface, is shaped 
like the circumference of the foot, except that a V-shaped opening is 
left behind for the reception of the frog, and is concave on the lower 
surface. The sole is produced by the velvety tissue, a thin membrane 
covering the plantar cushion and other soft tissues beneath the coffin 
bone. The horn of the sole differs from the horn of the wall in that 
its tubes are not straight and from the fact that it scales off in pieces 
over the whole surface. 
The frog is a triangular-shaped body, divided into two equal parts 
by a deep fissure, extending from its apex in front to the base. It 
fills the triangular space in the sole, to which it is intimately attached 
by its borders. The horn of the frog is produced in the same manner 
as the sole; but it differs from both the wall and sole in that the horn 
