MANUAL FOR ARMY HORSESHOERS. 37 



29, The elastic structures are the cartilages of the third phalanx, also 

 known as the lateral cartilages and the digital cushion (plantar 

 cushion, Pis. IV and VI). All parts of the foot, except the bones, 

 are to a certain extent elastic, but these structures are especially so. 



The lateral cartilages are two large elastic plates of cartilage, one 

 attached to the top of each wing of the third phalanx. They extend 

 backward and upward so far that their upper borders may be felt 

 under the skin above the coronet at the heels. 



ullnUral li game at 



Distal bonlr 



Plate VI.— Third Phalanx of Horse; Lateral View. 

 a, b, Anterior and posterior extremities of cartilage. 

 (From Sisson's Anatomy of the Domestic Animals; copyright, W. B. Saunders Co.) 



The digital cushion (plantar cushion) is a very elastic viedge-shaped 

 pad, which fills up the space between the lateral cartilages on the 

 sides, the frog below, and the deep flexor tendon of the foot above. 

 The point, or front part, of the digital cushion extends forward to 

 the ridge vhich separates the sole surface from the tendinous sm-face 

 of the third phalanx and lies just below the lo\\er end of the deep 

 flexor tendon. The base, or back part, is covered by the skin above 

 the heels. If the frog comes in contact with the gi'ound when the 

 foot is planted, the digital cushion acts as a buffer and prevents jar. 

 (See PL IV.) 



