46 THE ARMY HORSE. 



the Avail where it bends inward and forward, and the har is the 

 division of the Avail running from the heel to Avithin about 1 

 inch of the point or apex of the frog. It lies between the 

 horny sole and the frog. 



The external surface of the Avail is coA^ered by a thin varnish- 

 like coat of fine horn, called the 'pertoj)le. 



The internal surface of the Avail is coA^ered by from 500 to 

 000 thin plates or leaves of horn, called the horny lamina. 

 Between the horny laminae, Avliich run parallel to each other 

 and in a direction dowuAvard and forward, there are fissures 

 into which doAetail the sensitive lamina^ and this union, as 

 previously stated, binds the Avail of the hoof to the os pedis 

 and lateral cartilages. 



The upper border of the Avail shows a deep groove (coronary 

 groove) into which fits the coronary band. 



The loAver border is called the ''bearing edge" (or "spread" 

 in the unshod foot) and is the part to Avhich the shoe is fitted. 

 The liovny soleis a thick plate of horn, someAvhat half-moon- 

 shaped, and has tAvo surfaces and two borders. 



The upper surface is couA^ex (round cr bulging upward) and 

 is in union with the sensitive sole from Avhich the horny sole 

 grows. The loAver surface is concave or hollowed out and is 

 covered with scales or crusts of dead horn, which gradually 

 loosen and fall off. 



The outer border of the sole joins the inner part of the loAver 

 border of the Avail by means of a ring of soft horn, called the 

 white line. This mark or line is sometimes called the guide 

 line, as it shoAvs Avhere the nail should be started in shoeing. 



The inner border is a V-shaped notch and is in union Avith 

 the bars, except at its narrow part Avhere it joins the frog. 



The horny sole protects the sensitive sole and does not, in a 

 healthy foot, bear Aveight, except a A^ery narrow border at the 

 Avhite line, an eighth or tenth of an inch in width. 

 * The hor7uj frog is the Avedge-shaped mass of horn filling up 

 the triangular space betAveen the bars. The loAver face shoAvs 

 two prominent ridges, separated behind by a caA'ity, called the 

 cleft, and joining in front at the apex or point of the frog; 

 these ridges terminate behind in the bulbs of the frog. Be- 

 tween the sides of the frog and the bars are two cavities, called 

 the commissures. The upper surface of the horny frog is the 

 exact rcA'erse of the lower and shows in the middle a ridge of 

 horn, called the frog stay, which assists in forming a firm 



