396 THE CKtIST OR ^ALL OF THE HOOF. 



difference of obliquity is often so great, that the convexity or concavity of 

 the sole may be affirmed without the trouble of raising the foot for the 

 purpose of examination. 



It is of some importance to observe whether the depth of the crust 

 appears rapidly or slowly to decrease from the front to the heel. If the 

 decrease is little, and even at the heel the crust is high and deep, this 

 indicates a foot liable to contraction, sand-crack, thrush, and inflammation. 

 The pasterns are upright, the paces of that horse are not pleasant. On 

 the other hand, if the crust rapidly diminishes in depth, and the heels are 

 low, this is accompanied by too great slanting of the pastern, and disposi- 

 tion to S23rain in the back sinew. The foot, generally, is liable to be weak 

 and flat, and bruised, and there is more tendency to the frequent, but 

 obscure lameness, of which there will presently be occasion to treat — 

 the navicular-joint disease. 



The crust is composed of numerous horny fibres, connected together by 

 an elastic adhesive substance, and extending from the coronet to the base 

 of the hoof. Perhaps as good an idea of its structure as can be obtained, 

 is, supposing it to consist of a number of hairs or bristles connected 

 together by a strong glue. It differs materially in its texture, its elasticity, 

 its growth, and its occasional fragility, according to the state in which it 

 is kept, and the circumstances that are acting upon it. 



The exterior wall of the hoof should be smooth and level. Protu- 

 berances or rings round the crust indicate that the horse has had inflam- 

 mation in the feet, and that to such a degi-ee as to produce an ujiequal 

 growth of horn, and probably to leave some injurious consequences in the 

 internal part of the foot. If there is a depression or hollow in the front 

 of the foot, it betrays a sinking of the coflin-bone, and a flat or pumiced 

 sole. If there is a hollow at the quarters, it is the worst symptom of bad 

 contraction. 



The thickness of the crust, in the front of the foot, is rather more than 

 half an inch ; it becomes gradually thinner towards the quarters and 

 heels, but this often varies to a considerable extent. In some hoofs, it is 

 not more than half the above thickness. If however there is not, in the 

 majority of horses, more than half an inch for nail-hold at the tv»e, and 

 not so much at the quarters, it will not appear surprising that these horses 

 are occasionally wounded in shoeing, and especially as some of them are 

 very unmanageable while undergoing this process. 



While the crust becomes thinner towards both quarters, it is more so at 

 the inner quarter than at the outer, because more weight is thrown upon 

 it than upon the outer. It is more under the horse. It is under the iinier 

 splint-bone, on which so much more of the weight . rests than on the 

 outer ; and, being thinner, it is able to expand more. Its elasticity is 

 called more into play, and concussion and injury are avoided. Wlien the 

 expansion of the quarters is prevented by their being nailed to an 

 unbending shoe, the inner quarter suffers most. Corns are oftenest found 

 there ; contraction begins there ; sand-crack is seated there. Nature 

 meant that this should be the most yielding part, in order to obviate 

 concussion, because on it the weight is principally thrown, and therefore 

 when its power of yielding is taken away it must be the first to sufi'er. 



A careful observer will likewise perceive that the inner quarter is 

 higher than the outer. While it is thin to yield to the shock, its increased 

 surface gives it sufficient strength. 



On account of its thinness, and the additional weight which it bears, 

 the inner heel wears away quicker than the outer ; a circumstance that 

 should never be forgotten by the smith. His object is to give a plane and 

 level bearing to the whole of the crust. To accomphsh this, it will be 



