DEVELOPMENT OF THE HOOF. 423 



marked by ridges, or waves, running in rings around the hoof, 

 and sometimes causing ridges, or grooves, running up and 

 down the hoof. 



The sole is produced by the villi which bestud the under 

 surface of the sensitive sole, which will be hereafter described. 

 It is produced in the same way that the wall is. Its fibers, or 

 tubes, take an oblique direction forward, following the same 

 slant of the wall of the foot. Its fibers are finer, and it is 

 softer and more elastic than the wall. 



The frog is also secreted by the villi of the sensitive fi'og, 

 (yet to be explained), in the same way that the sole is secreted 

 by the villi of the sensitive sole. The fibers of the frog pass 

 in an oblique direction corresponding with the direction of the 

 fibers of the wall at the quarters. It is not so dense as the 

 wall, and consequently possesses much greater elasticity. Its 

 fibers are much finer, and the hollow of the tubes compara- 

 tivelv much o-reater. 



These tubes are not empty, but, like the inside of the hairs, 

 are filled with a secretion of gelatinous (jelly-like) matter, like 

 a pith. This renders the horny substance tough and elastic, 

 and imparts to it that property which distinguishes it as living 

 horn. If a piece of hoof is cut across, these piths can be seen, 

 like little white spots. 



Disease may interrupt the development of the hoof, or some 

 forms of disease increase it. Heat and dryness render it litird 

 and brittle. ^Moisture softens it and renders it more elastic, 

 but, at the same time, renders it weaker and less resisting. 



The liormj lamellce are generally said to be secreted from the 

 sensitiv^c lamellae ; but of the correctness of this I entertain 

 some doubt. They appear to me to be a secretion from the 

 lower edge of the outer part of the membrane lining the side 

 of the coronary substance, which lies in contact with the exca- 

 vation in the upper border of the wall. I have never demon- 

 strated this, but think I have seen their origin in this, in the 



