PLANTAR SYSTEM. 435 



The Sole, as well as the wall, is fibrous in its structure; 

 but its fibres appear to be of a finer quality, and, in course, are 

 very much shorter: they, however, take an oblique direction, from 

 behind forwards, following the same degree of slope as those of 

 the wall. They issue from the villi penetratiug the superior 

 surface. To the fineness of its fibres, combined with the relative 

 magnitude of the tubular canals, and consequent relative pro- 

 portions of horny and gelatinous substances, may be ascribed the 

 comparative softness and elasticity of the sole. 



The Frog, however, displays these qualities in such a remark- 

 able degree as to appear, in fact, to be composed of quite another 

 kind of horn; though, on examination, we find it to evince the 

 same fibrous structure, the only perceivable differences being 

 the comparative fineness of the fibres and their proportion- 

 ably greater tubularity : their direction is oblique, correspondent 

 with those of the wall. 



Production of the Hoof. 



The wall is produced by the coronary substance, a sensitive and 

 glandular part we shall have occasion soon to examine. Its villi, 

 by some peculiar, mysterious, secretory process, convert the blood 

 circulating through them into a soft pulpy gelatinous matter, which 

 by exposure becomes hard horn, descending from the villous point 

 that produced it, in the form of a tubular fibre, down to the sole. 

 The fibres are united together at their very origin, but their 

 tubes or canals diminish, the lower they descend ; which accounts 

 for the porous or honeycomb-like structure of the interior of the 

 coronary border and the comparative solidity of the parts below. 

 The outer layers or strata of fibres are found to be more compact 

 and of closer texture than the inner; which arises, in part, from 

 the villi producing them being removed to a greater distance, 

 and to the comparative smallness of their canals, and which, con- 

 sequently, the sooner become obliterated. The use of Mr. 

 Clark's coronary frog-band becomes now more apparent, serving, 

 as it evidently does, to cover and protect these external fibres 

 until they grow sufficiently firm and solid of themselves to bear 

 exposure and resist casualties. 



The sensitive laminae make no additiop to the substance or 

 thickness of the wall: they simply produce the horny lamellae 

 arranged along its interior; as one proof of which, the wall 

 measures as much in thickness at the place where it quits the 

 coronet as it does at any point lower down. Other demon- 

 strations of this fact come every day before such practitioners as 

 have to treat canker, quittor, sandcrack, and other diseases of 

 the feet. 



The Hokny Sole is a pioductiou from the villi of the sen- 



