294 THE CRUST OR WALL OF THE HOOP. 



THE CRUST OR WALL OF THE HOOF. 



The crust, or ivall, is that portion which is seen when the foot is 

 placed on the ground, and reaches from the termination of the hair 

 to the ground. It is deepest in front, where it is called the toe, 

 measuring there about three inches and a half in depth, (see Fig 

 48,) shallower at the sides, which are denominated the quarters, 

 and of least extent behind, where it is seldom more than an inch 

 and a half in height, and is termed the heel. The crust in the 

 healthy foot presents a flat and narrow surface to the ground, 

 ascending obliquely backAvards, and possessing different degrees 

 of obliquity in different horses. In a sound hoof the proper 

 degree of obliquity is calculated at forty-five degrees, or the 

 fourth part of a semicircle, at the front of the foot. When the 

 obliquity is greater than this, it indicates undue flatness of the 

 solo, and the crust is said to have "fallen in." If the obliquity 

 is very much increased, the sole projects, and is said too be pum- 

 iced or convex. 



If the foot is more upright, or forms a greater angle than forty- 

 five degrees, it indicates much contraction, and a sole too concave ; 

 and this difference of obliquity is often so great, that the convex- 

 ity 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 where 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 accom- 

 panied by too great slanting of the pastern, and disposition to 

 sprain 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 membranous substance, and extending 

 from the coronet to the base of the hoof. It differs materially 

 in its texture, its elasticity, its growth, and its occasional brit- 

 tleness according to the state in which it is kept, and the cir- 

 cumstances that are acting upon it. 



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

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

 inflammation in the teet, and that to such a degree, as to produce 

 an unequal growth of horn, and probably to leave some injurioug 



