502 



THE ANATOMY OF THE HORSE 



band, is marked by its whitish colour. On its external surface it resemblea 

 the crust below ; but internally it differs in being smoothly excavated, 

 ■whilst the crust exhibits perpendicular strije, corresponding with the laminse; 

 but this is not well shown in Fig. 8G. In examining the cut of the sole, Fig. 

 88, it will be seen that the crust is bent inwards towards the frog at the 

 heel on each side : these are the bars, which in the natural foot appear as 

 sharpened prominences, extending from the heels into the centre of the foot, 

 between the sole and the frog, and which are useful as buttresses, supporting 

 the crust from being crushed inwards by the superincumbent weight. The 

 sole is the plate at the bottom of the foot, which should be slightly concave 

 downwards, and is fixed to the inner edge of the crust, and the outer sides 

 of the bars, and not to their lower surfaces. Its usual thickness is about 

 one-sixth of an inch, but it will vary greatly in different horses, and it is 

 thicker where it runs back between the bars and the crust. It is secreted 



Fic. SO.— The Hoor. 



A. Outer surface of crust. 



B. Inner surface of crust. 



C. Upper surface of sole. 



D. Part corresponding with the cleft 



of the frog. 



E. Coronary band. 



Fio. 87.— Front View of the 

 Foot, with the Hoof re- 



A. Coronary substance. 



B. 5000 LaniiniE. 



—The under si-rfacb 

 OF the Foot. 



A. Cleft of frog. 



B. B. Sole. 



C. Cleft between heels. 



in plates, which can readily be separated with a knife in that direction. 

 The frog is the prominent, triangular, and elastic substance, which fills up 

 the space between the heels posteriorly, the bars on each side, and the sole 

 in front. In the middle is a longitudinal fissure, called the cleft, the sides 

 of which should form an angle of about forty-five degrees. In front of this 

 cleft is a solid wedge of the elastic horny substance, constituting the frog, 

 which lies immediately beneath the navicular bone, and has received the 

 name of the cushion. Posteriorly it is spread out into a thin band on each 

 side which covers the bulbs of the heels, and j)asses round the upper part of 

 the wall constituting the coronary froghand of Bracy Clark, which is con- 

 tinuous with the coronary substance. The structure of the horn which 

 forms these three divisions varies a good deal. In the crust it is fibrous, 

 somewhat resembling whalebone in this respect, but not quite so hard ; 

 these bristly fibres are united by a gelatinous substance, but they are 

 arranged so as to lie in straight lines descending from the coronary circle 

 to the ground. The wall may, therefore, be considered as composed of hairs 

 agglutinated together, and each secreted by one of the villi, which are so 

 thickly sj^read over the surface of the coronary circle. The solo is also 



