42 MANUAL FOR STABLE SERGEANTS. 



BONES OP THE FOOT. 



109. The bones of the pastern and foot are the first phalanx 

 (long pastern bone), the second phalanx (short pastern bone), the 

 third phalanx (coffin bone), and the navicular bone (distal sesamoid). 

 The first two bones require no description. 



110. The third phalanx (coffin bone) is entirely inclosed by 

 the hoof, which it resembles in shape. 



The upper or articular surface faces upward and backward and 

 articulates with the second phalanx. Immediately behind and below 

 this surface is a small area for the articulation of the navicular bone. 



The wall surface (front and sides) slopes downward and forward. 

 It is roughened for the attachment of the laminar corium and perfo- 

 rated by numerous small openings for the passage of blood vessels and 

 nerves. At the top of this surface, in front, is a ridge to which the 

 tendon of the extensor of the foot is attached. 



The under surface corresponds in shape to the sole of the hoof. 

 It is smooth except at the back part, which is roughened for the 

 attachment of the tendon of the deep flexor of the foot. 



The wings (angles) one on either side, project backward and give 

 attachment on their upper borders to the cartilages of the foot. 



111. The navicular bone (distal sesamoid) is shuttle-shaped, 

 and lies behind the junction of the second and third phalanges with 

 which it articulates. The deep flexor tendon of the foot passes over 

 its lower surface. 



THE ELASTIC STRUCTURES OP THE FOOT. 



112. The cartilages of the third phalanx, also known as the 

 lateral cartilages (fig. 21), are large elastic plates of cartilage, attached 

 one to either wing of the bone. They project backward and upward, 

 their upper borders extending above the hoof, where they may be felt 

 beneath the skin above the coronet at the heels. 



113. The digital cushion (plantar cushion) (fig. 19), the prin- 

 cipal elastic structure of the foot, is a wedge-shaped pad, situated 

 above the frog, below the deep flexor tendon of the foot, and between 

 the cartilages of the third phalanx. The apex or points is directed 

 forward and lies just below the lower end of the deep flexor tendon. 

 The base or back part lies under the skin of the heels. The digital 

 cushion acts as a buffer to the foot and prevents jar. 



