ANATOMY OF THE FOOT. 371 



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 of 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 flexor 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 connect- 

 ive tissue, which gives a symmetry to the parts by filling up and 

 rounding 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 hand 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, which are held together by a tenacious 

 opaque matter. The horn extends from the coronary band to the 

 lower border of the hoof. (Plate XXIX, 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 laminae, plantar cushion, and the lateral cartilages. 

 (PlateXXX, 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 

 is soft, moist, and elastic to a remarkable degree. It is the function 

 of the frog to destroy shock and to prevent slipping. 



