THE FOOT. 



319 



Of the two borders, the external or anterior describes almost a semi-circum- 

 ference, and unites intimately with the inferior border of the wall. The internal 

 ov posterior, on the contrary, much less extensive, simulates a re-entering angle, 

 like the letter V, whose sides are adherent to the bars and the frog. 



c. The Frog. — The frog is a wedge or pyramid of soft horn, which covers 

 the plantar cushion, whose form it reproduces. Lodged in the angle formed by 

 the bars and the posterior border of 

 the sole, it is seen to be single in 

 front and bifid behind ; two faces 

 and two extremities are thus assigned 

 to it. 



The superior or internal face, 

 b (Fig. 114), is the reverse of the in- 

 ferior face of the plantar cushion ; 

 it presents, consequently, a marked 

 relief on the median line, known 

 under the name frog-stay, m (Figs. 

 113 and 115), and on each side two 

 gutters, /(, n, converging in front, 

 which respond to the branches of 

 the plantar cushion. Like the sole, 

 it is covered by a large number of 

 perforations, which receive the cor- 

 responding villosities of the velvety 

 tissue. 



The inferior or external face 

 (Figs. Ill and 116), much more 



important with regard to the exterior, is hollowed in its middle by a cavity, h, 

 called the median lacuna, separating the two branches, i, i, from each other. 

 Between each branch, i, and the bar are 

 the lateral lacunse, j,J (Figs. Ill, 113, and 

 115); finally, the boclg of the frog is the 

 point of juncture of its two branches. 



In the wild state, the inferior face of 



Fig. 114.— Interior of the hoof. 



Fig. 115.— Transverse section of the hoof (posterior 

 part). 



Fig. 116.— Frog and periople. 



the ftiruncular branches, in conditions of nature, is upon the same level as that 

 of the heels and the bars ; it consequently rests upon the ground, as can be 



