THE SENSE ORGANS AND SKIN OF THE HORSE 



ridges, which subside in front and are fused with the sole; they are united with each 

 other by the frog. For topographic purposes the wall may be divided into an an- 

 terior part or "toe" (Paries ungulse dorsalis), lateral parts or "quarters" (Paries 

 ungulte mediahs, lateraUs), and the angles or "heels" (Paries unguis; volaris s. 

 plantaris) . It presents two surfaces and two borders. The external surface is con- 

 vex from side to side and slopes obliquely from edge to edge. In front the angle of 

 inclination on the ground plane is about 50° for the forelimb, 55° for the hind limb; 

 on the sides the angle gradually increases and is about 100° at the heels. The curve 

 of the wall is ^^^der on the lateral than on the medial side, and the slope of the medial 

 quarter is steeper than that of the lateral 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 and in- 

 dicate the direction of the horn tubes. 

 i»' The internal surface is concave from side to 



side, and bears about six hundred thin primary 

 laminae, which extend from the coronary groove 

 to the basal border of the wall. Each bears a 

 hundred or more secondary laminae on its sur- 

 r^f\, \ \ ^ faces, so that the arrangement is pennate on 



\ 1 cross-section. These hornjf laminae are continued 



. f on the inner surface of the bars, and dovetail with 



corresponding laminae of the the corium. The cor- 

 ' ^ onary border (Margo coronarius) is thin. Its outer 



^ aspect is covered by a layer of soft horn known 



d ' '^Wf^"'^ as the periople (Limbus corneus) ; this appears as 



€ - 1-'^^^i ^ ring-like prominence above and gradually fades 



1-^ „ /' « ^ out below; at the angle it forms a wide cap or 



/i ^^ bulb and blends centrallj^ with the frog. The 



inner aspect of the border is excavated to form 

 the coronary groove (Sulcus coronarius ungulse), 

 which contains the thick coronary corium. The 

 Fig. 710.— Digit oi- Hoese, Showing groovc is deepest iu front, uarrows on the sides, 



Surface Relations of Bones and i • • -, i i n 1,1 i tot,- 



JoixTs. The Cartilage is Largelv ^ud IS Wide and shalloW at the hccls." It IS pcr- 



ExposED. forated by innumerable small, funnel-like openings 



a. First phalanx; 5, second phalanx; wliich are occupied by the papillae of the coronary 



n;lw tr^ntT.:,H''hn''i''f ■ '' f''"" ^'t'X ^orium iu the natural state. Between the border 



moicl or navicular bone; /, pastern joint; 



a. coffin joint ; h' , cut edge of wall of hoof of the Wall proper and the periople there is a small 



(70; !-, laminar corium. (After Ellenberger, groOVe which COntaiuS the COrluUl of the pcriople. 



At the heel this groove is merged with the coronary 



groove. The basal or ground border (Margo basi- 



laris) 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 periphery of the 



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

 by careful measurements of .50 fore and 36 hind feet the following average angles: 



Fore Foot Hind Foot 



Toe 47.26° 54.1° 



Medial angle 101. .57° 96.5° 



Lateral 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 00°. 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 2:13-^:1 in the hind hoof. 



2 The wide groove at the heels, however, contains chiefly the corium of the periople. 



