THE HOOF 



765 



internal side, and the external quarter is more oblique than the internal one. The 

 surface is smooth and is crossed by more or less distinct ridges, which are parallel 

 with the coronary border and indicate variations in the activity of the growth of 

 the hoof. It is also marked Ijy fine parallel stria, which extend from border to 

 border in an almost rectilinear manner. 



The slope o( the wall varies considorahly in apparently normal hoofs. Lungwitz found 

 by careful measurements of 56 fore and 36 hind feet the following average angles: 



Fork Foot Hind Foot 



Toe 47.26° 54.1° 



Inner angle 101.57° 96.50° 



Outer angle 101.37° 96.1° 



The wall of the fore foot may even be more upright than that of the hind, and may have an 

 angle of 60°. The length of the wall at the toe, quarters, and heels is in the ratio of about 

 3 : 2 : 1 in the fore fcxjt and about 2 : IJ^ : 1 in the hind hoof. 



The inner surface is concave from side to side, ;iiid benrs nbout six hundred 

 thin primary laminae (Crista? ungulse), which ex- 

 tend from the coronary groove to the junction 

 of wall and sole. Each liears a hundred or more ;•: 

 secondary laminae on its surfaces, so that the 

 arrangement is pennate on cross-section. These ^»- 

 horny laminae are continued on the inner surface of 

 the bars, and alternate with corresponding lamina' 

 of the matrix. 



The proximal or coronary border (Margo oc- \ 1^ — a 



cultus) is thin. Its outer aspc^ct is covered by a 



layer of soft horn known as the periople; this #; ) /^kK"'^' 



appears as a ring-like prominence above and ^^\^^...^^y^k. 



gradually fades out below; at the angle it forms 

 a wide cap or bulb and blends centrally with the 



frog. The inner aspect of the Ijorder is excavated i d \ ^^ak--3 



to form the coronary groove (Sulcus coronalis vw^j^.^ t|5'4'« 

 ungulse), which contains the thick coronary ma- X^^ ferS^y-^ . :f^^l^.--c 

 trix. The groove is deepest in front, narrows ^HBBBBH^^^'^ ' 

 on the sides, and is wide and shallow at the 

 heels.^ It is perforated by innumerable small, f 



funnel-like openings which are occupied by the „ ^,^ .^ 



J ^ ... Fig. 57.3. — Digit of Horsf., showing 



papillae of the coronary matrix m the natural Surface Relations of Bones 



state. AND Joints. The Lateral Car- 



The distal or ground border (Margo liber) of tilage is xposed. 



J, 1 1 1 c • J. J. -ii ii "' First phalanx; 6, second i)hal- 



the unshod hoot comes m contact with the anx; c, third phalanx; d, lateral carfi- 

 grOUnd. Its thickness is greatest in front and lage; e, third sesamoid or navicular hone; 



decreases considerably from before backward on /.I'^^'e;" J<;j"t: .'/.coffin joint; ;/, cut 



. , , , . ,. , . edge of wall of hoof (h)\ i, laminar 



the Sides, but there is a slight increase at the matrix. (After Ellenberger, in Leiser- 



angles. Its inner face is united with the per- in^'s .^.tias.) 



iphery of the sole by horn of lighter color and 



softer texture, which appears on the ground surface of the hoof as the white line. 



In the ease of horses at liberty the wall is usually worn of? to the level of the adjaeent .sole, 

 but if the ground is too soft the wall is likely to become unduly long and split or break or undergo 

 deformation. On very hard or rough ground, on the other hand, the wear may be in excess of 

 the growth. In the case of shod horses it is necessary to remove the excess of growth of the wall 

 at each shoeing. The thickness of the wall at the toe, quarters, and heels is about in the ratio 

 of 4 : 3 : 2 for the fore foot and al)Out 3 : 2}4 '■ 2 for the hind foot. 



2. The sole (Solea unguke) forms the greater part of the ground surface of 

 the hoof. It is somewhat crescentic in outline, and presents two surfaces and two 

 borders. 



1 The wide groove at tire heels, however, contains chiefly the matrix of the periople. 



