422 PLANTAR SYSTEM. 



description of horn. Sainbel ascribes all this to " a relaxation of 

 the fibres composing the hoof: in which case, the diameters of 

 the vessels are increased, the porosities are multiplied, and the 

 fluids abound in them in too great quantities; consequently this 

 kind of foot is soft, tender, and sensible." Small feet, on the con- 

 trary, in general possess a close woven horn, thick in substance, 

 and consequently prove strong : they are rather oval than circular 

 in figure, with great depth of substance, and are found to be of a 

 durable nature. ** In feet of this description," says Sainbel, 

 " from the too close union and too close tension of their fibres, the 

 vessels destined to conduct the nutritious fluid are contracted and 

 obliterated ; whence proceeds that dryness of the part which 

 renders the horn brittle and liable to spUt*." 



Division. — To the common observer the hoof appears to con- 

 sist of one entire or indivisible case; but the anatomist finds, by 

 subjecting it to maceration, or coction, or even to putrefaction, 

 that it resolves itself into three separate pieces : still, so long as 

 the hoof maintains its integrity, such is the force of cohesion 

 existing between these three parts, that we as easily rend it in 

 any other place as dissever one of its jointures. These consti- 

 tuent parts are the iva/l, the sole, and the frog. 



The Wall. 



The wall or crust is the part of the hoof which is visible while 

 the foot stands upon the ground. It forms a circular boundary 

 wall or fence inclosing the internal structures. On taking up the 

 foot, we find the wall prominent all round beyond the other parts, 

 making the first impression upon the ground, and evidently 

 taking the largest share of bearing. It is the part to which the 

 shoe is nailed. It is, in fact, the most important division of the 

 hoof; appearing to form (in the words of Mr. Clark) " the 

 basis or first principle in the mechanism of the hoof, the other 

 parts being all subordinate to this." 



Situation and Relations. — The wall takes its beginning at the 

 coronet, from the terminating circular border of the skin, with 

 which it is intimately united ; their line of union being concealed 

 by a row of overhanging hairs. From the coronet the wall 

 descends in an oblique direction to the bottom of the foot, where 

 it embraces the sole, and terminates in a circular projecting 

 border. The anterior and lateral parts of the hoof are Ibrmed 

 entirely by the wall ; but at the posterior part, instead of the 

 heels of the wall being continued one into the other so as to com- 

 plete the circle, they become inflected, first downward, afterwards 

 forward and inward, and are elongated in the latter direction 

 * Saiiibcl's Lcctutes on the Elements ol Farrierv. 



