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 by fine parallel striae, which extend from border to 

 border in an almost rectilinear manner. 



The slope of the wall varies considerably in apparently normal hoofs. Lungwitz found 

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



Fore 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 G0°. The length of the wall at the toe, quarters, and heels is in the ratio of about 

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



The inner surface is concave from side to side, and bears about six hundred 

 thin primary laminae (C'rista? ungulse), which ex- 

 tend from the coronary groove to the junction |; , 

 of wall and sole. Each bears 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 laminae 

 of the matrix. 



The proximal ur coronary border (Margo oc- 

 cultus) is thin. Its outer aspect is covered by a 

 layer of soft horn known as the periople ; this 

 appears as a ring-like prominence above and 

 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 border is excavated 

 to form the coronary groove (Sulcus coronalis 

 unguke), which contains the thick coronary ma- 

 trix. The groove is deepest in front, narrows 

 on the sides, and is wide and shallow at the 

 heels.^ It is perforated by innumerable small, 

 funnel-like openings which are occupied by the 

 papillae of the coronary matrix in the natural 

 state. 



The distal or ground border (Margo liber) of 

 the unshod hoof comes in contact with the 

 ground. Its thickness is greatest in front and 

 decreases considerably from before backward on 

 the sides, but there is a slight increase at the 

 angles. Its inner face is united with the per- 

 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 case of horses at liberty the wall is usually worn off to the level of the adjacent sole, 

 but if the ground is too soft the wail 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 about 3 : 2^ : 2 for the hind foot. 



2. The sole (Solea ungulse) 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 the heels, however, contains chiefly the matrix of the periople. 



..-C 



Fig. 573. — Digit of Horse, showing 

 Surface Relations of Bones 

 AND Joints. The Lateral Car- 

 tilage is Exposed. 

 a. First phalanx; 6, second phal- 

 an?v; c, third phalanx; d, lateral carti- 

 lage; e, third sesamoid or navicular bone; 

 /, pastern joint; g, cofEn joint; h! , cut 

 edge of wall of hoof (/(); i, laminar 

 matrix. (After Ellenberger, in Leiser- 

 ing's Atlas.) 



