890 



THE SENSE ORGANS AND SKIN OF THE HORSE 



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

 and two borders. The internal surface is convex, and slopes with a varying 

 degree of obliquity downward to the convex border. It presents numerous small 

 funnel-like openings which contain the papillae of the sole corium in the natural 

 state. The external or ground surface is the converse of the preceding. It is nor- 

 mally arched — and more strongly in the hind than in the fore foot — but the curvature 

 is subject to wide variation; in heavy draft horses the sole is commonly less curved 

 than in the lighter breeds and may even be flat. The surface is usually rough, since 

 the horn exfoliates here in irregular flakes. The convex border is joined to the wall by 

 relatively soft horn, previouslj' referred to as forming the white line on the ground 

 surface of the hoof. The angle of junction is rounded internally and presents a 



Fig. 71^. — Right Fore Hoof of Horse; Ground Surface. 

 ly Basal or ground border of wall; .2, laminae of wall; 3, angle of wall; 4, bar; 5, sole; 5', angle of sole; 6, white 

 line (junction of wall and sole); 7, apex of frog; 8, central sulcus of frog; 9, 9, collateral sulci between frog and bars; 

 10, 10, bulbs of hoof. 



number of low ridges and specially large openings for the papillae of the corium. 

 There is frequently a ridge of larger size at the toe. The concave border has the 

 form of a deep angle which is occupied by the bars and frog. It concurs in part 

 with these in forming two pronounced ridges in the interior of the foot. The 

 parts of the sole between the wall and bars may be termed its angles. 



3. The frog (Cuneus ungulse) is a wedge-shaped mass which occupies the angle 

 bounded Ijy the bars and sole, and extends considerably below these on the ground 

 surface of the foot. It may be described as having four surfaces, a base, and an 

 apex. The internal surface bears a central ridge, the spine or "frog-stay" (Spina 

 cunei ungulse), which is high posteriorly and subsides abruptly in front. On either 

 side of this there is a deep depression, which is bounded outwardly by the rounded 



