BREEDS OF HORSES 107 



they dovetail. (4) The fleshy sole, which covers the entire under 

 surface of the foot, excepting the fleshy frog and bars. The horny 

 sole is produced by the fleshy sole. (5) The fleshy frog, which 

 covers the under surface of the plantar cushion and produces the 

 horny frog. 



Horny, Box, or Hoof. The horny box, or hoof, consists of wall 

 and bars, sole and frog. The wall is all that part of the hoof which 

 is visible when the foot is on the ground. As already stated, it con- 

 sists of three layers the periople, the middle layer, and the leafy 

 layer. 



Bars. The bars are forward prolongations of the wall, and 

 are gradually lost near the point of the frog. The angle between 

 the wall and a bar is called the buttress. Each bar lies against 

 the horny frog on one side and incloses a wing of the sole on the 

 other, so that the least expansion or contraction of the horny frog 

 separates or approximates the bars, and through them the lateral car- 

 tilages and the walls of the quarters. The lower border of the wall 

 is called the bearing edge, and is the surface against which the shoe 

 bears. By dividing the entire lower circumferences of the wall into 

 five equal parts, a toe, two side walls, and two quarters will be ex- 

 hibited. The "heels," strictly speaking, are the two rounded soft 

 prominences of the plantar cushion, lying one above each quarter. 

 The outer wall is usually more slanting than the inner, and the 

 more slanting half of a hoof is always the thicker. In front hoofs 

 the wall is thickest at the toe and gradually thins out toward the 

 quarters, where in some horses it may not exceed one-fourth of an 

 inch. In hind hoofs there is much less difference in thickness be- 

 tween the toe, side walls, and quarters. The horny sole, from which 

 the flakes of old horn have been removed, is concave and about as 

 thick as the wall at the toe. It is rough, uneven, and often covered 

 by flakes of dead horn in process of being loosened and cast off. 

 Behind, the sole presents an opening into which are received the 

 bars and horny frog. This opening divides the sole into a body and 

 two wings. 



The periphery of the sole unites with the lower border of the 

 wall and bars through the medium of the white line, which is the 

 cross section of the leafy horn layer of the wall, and of short plugs 

 of horn which grow down from the lower ends of the fleshy leaves. 

 This white line is of much importance to the shoer, since its dis- 

 tance from the outer border of the hoof is the thickness of the wall, 

 and in the white line all nails should be driven. 



The Frog. The frog, secreted by the pododerm covering the 

 plantar cushion or fatty frog, and presenting almost the same form 

 as the latter, lies as a soft and very elastic wedge between the bars 

 and between the edges of the sole just in front of the bars. A broad 

 and shallow depression in its center divides it into two branches, 

 which diverge as they pass backward into the horny bulbs of the 

 heel. In front of the middle cleft the two branches unite to fonn 

 the body of the frog, which ends in the point of the frog. The bar 



