124 ELEMENTS OF HIPPOLOOY. 



pulling back — tendon of the leg. Another broad tendon is fas- 

 tened to the front of the coffin-bone to pull it forward. This is 

 an extensor tendon. Both are well shown in Figure 82. 



Under the flexor tendon and the lateral cartilages is placed 

 a soft, highly elastic cushion, called the plantar cushion, that, 

 by its compression between the sole and frog of the hoof on its 

 under side and the tendon and lateral cartilages above it, acts 

 to soften the shock of impact. 



Enveloping all the structures above enumerated is the fleshy 

 continuation of the skin, much changed in appearance from that 

 above the hoof. This covering is highly vascular — that iSj it is 

 abundantly supplied with nerves and with blood and other ves- 

 sels that supply the foot. The upper border of this covering is 

 called the coronary band, and along the upper border of this 

 band is another band, called the perioplic ring. Below the 

 coronary band the fleshy covering of the foot is covered with a 

 series of little ridges, called the sensitive laminae. They fit 

 into corresponding depressions in the inner surface of the wall. 

 These depressions in the wall are called the insensitive laminse. 



On the plantar surface, the fleshy envelope is called the 

 velvety tissue. 



The hoof is the nail of the horse. It is composed of three 

 parts — the wall, the sole, and the frog. The wall includes all 

 that portion of the horny box that is visible ^hen the foot is on 

 the ground. The wall is divided into three regions : the toe, in 

 front; the quarters, on the sides; and the heels, in rear. At the 

 heels the wall doubles back, towards the center of the foot, 

 forming the bars. The wall is thickest at the toe and is grad- 

 ually thinner towards the heels, where it thickens again to form 

 the bars. The outer face of the wall is composed of a great 

 number of filaments, similar to hair in their growth and compo- 

 sition, compacted firmly together with a natural glue, and grow- 

 ing downward from the coronary band. It is covered with a sort 

 of natural varnish that is secreted by the perioplic ring. The 

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