THE CRUST OF THE HOOF. 281 



it than upon the outer. • It is more under the horse ; it is under the inner 

 splint-bone, on which so much more of the weig-ht rests than on the outer, 

 and, beino' thinner, it is able to expand more ; its elasticity is called more 

 into'play,^and concussion and injury are avoided. When 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 

 beo-ins 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 was principally thrown, and therefore when its power of yielding 

 is taken away it must be the tirst to suffer. 



A careful observer will likewise perceive that the inner quarter is a little 

 hi'J-her 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 w^eight 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 plain and level bearing to the whole of the crust. To accompUsh 

 this, it will be often scarcely necessary to remove anything from the 

 inner heel, for it is already removed by the wear of the foot. If he 

 forgets this, as he too often seems to do, and takes off with his knife or 

 his buttress an equal portion all round, he leaves the inner and weaker 

 quarter lower than the outer; he throws an uneven bearing upon it; and 

 produces corns and sand-cracks and splints, which a 

 little care and common sense might have avoided. 

 The crust does not vary much in thickness, (see a, page 

 249, and h in the accompanying cut,) until near the 

 top, at the coronet, or union of the horn of the foot 

 with the skin of the pasterns where {w, page 249) it 

 rapidly gets thin. It is in a manner scooped and 

 hollowed out. It likewise changes its colour and its 

 consistence, and seems almost hke a continuation of 

 the skin, but easily separable from it by maceration, or 

 disease. This thin part is called the coronary ring, j?, p. 249 ; and it 

 receives within it, or covers, a thickened and bulbous prolongation of the 

 skin, called the coronary ligament, (see 6 in the accompanying cut.) This 

 requires a better name, for it has not a portion of ligamentous structure 

 in it. This prolongation of the skin is thickly supplied with blood-vessels. 

 It is almost a mesh of blood-vessels connected together by fibrous 

 texture, and many of these vessels are employed in secreting or forming 

 the crust or wall of the foot. Nature has enabled the sensible laminse of 

 the coffin bone c, which will be described presently, to secrete some horn, 

 in order to afford an immediate defence for itself when the crust is 

 wounded or taken away. Of this we have proof, when in sand-crack, or 

 quittor, we are compelled to remove a portion of the crust. A pellicle of 

 horn, or of firm hard substance resembling it, soon covers the wound ; 

 but the crust is principally formed from this coronary hgament. Hence it 

 is, that in sand-crack, quittor, and other diseases in which strips of the 

 crust are destroyed, it is so long in being renewed, or growing down. It 

 must proceed from the coronary ligament, and so gradually creep down 

 the foot with the natural growth or lengthening of the horn, of which, as 

 in the human nail, a supply is slowly given to answer to the wear and 

 tear of the part. 



Below the coronary ligament is a thin strip of horny matter, which 

 has been traced from the frog, and has been supposed by some to be 

 connected with the support or action of the frog, but which is evidently 



