274 OUTLINES OP EQUINE ANATOMY. 



separated into minor parts, we generally see it as a horny 

 box presenting an opening above. It is composed of epi- 

 thelial cells, being (as before observed) merely epidermis 

 so modified as to form the substance commonly known as 

 horn. Horn consists of tubular processes similar to hairs 

 united by softer epithelial cells, the latter forming a matrix 

 for the fibres and, by fixing them firmly together giving the 

 horn its consistency. The horn of the hoof presents two 

 parts with different characters. The horny frog is much 

 softer in consistency and more elastic than the remainder 

 of the hoof, and resembles in nature and structure (as 

 pointed out by Professor Gamgee) the foot pad of the dog. 

 It owes its peculiarities to the delicacy of its horn fibres, 

 which are finer than those of most other parts of the hoof, 

 and which are produced by the delicate papillae of the sen- 

 sitive frog. The hoof consists of several parts agglutinated 

 together in the same manner though less firmly than the 

 individual fibres. These are the wall (with the bars), sole, 

 and frog. The frog and the sole are separable by mace- 

 ration, but the bars are mere reflections forward and 

 inwards of the wall, and therefore remain firmly fixed to 

 that part. The Wall is all that portion of the hoof which 

 is visible from before and from the sides when the foot 

 rests upon its plantar surface. It is artificially divided into 

 six parts, three on each side. The anterior or toe centrally 

 lies in connection with its fellow, externally is continuous 

 with the quarter or middle part at its anterior part, while 

 the posterior margin of the quarter is continuous with the 

 heel, from the posterior margin of which the bars run in a 

 direction forwards and inwards for about two inches, being 

 separated from the frog by the commissures, terminating 

 anteriorly in a point. In all jjarts the fibres of the hoof run 

 obliquely downwards and forvmrds. The toe and the pos- 

 terior margin of the heel have the same direction, the 

 latter being not half so high as the former in a well-foi-med 

 hoof ; their superior extremities are connected by a thin 

 ridge running obliquely downwards and backwards, their 

 inferior margin is horizontal. The internal surface of the 

 wall superiorly presents a concave surface extending 

 obliquely downwards and backwards about half an inch in 

 depth, growing broader posteriorly in becoming inflected 

 forwards to form the crust of the bars which blend with the 

 horny sole anteriorly. It presents a number of deep small 



