rooT-ROT. 377 



somewhat the structure of the substance of the frog in the 

 foot of the horse, and performing, at the same time, analo- 

 gous functions. > The. whole, hoof, too, is secreted from the 

 vascular tissue underneath. 



" Now this diversity of structure is for particular purposes. 

 The crust, like that in the hoof of the horse, being harder 

 and tougher than the sole, keeps up a sharp edge on the 

 outer margin, and is mainly intended to resist the wear-andr 

 tear to which the foot of the animal is exposed. The soft 

 • pasturage on which the . sheep is occasionally put presents 

 little, if any, of that rough friction to which the feet of the 

 animal is naturally intended to be exposed. The crust, 

 therefore, grows unrestrained, until it either laps over the 

 sole,Jike the loose sole of an old shoe, and serves to retain 

 and accumulate the earth and filth, or is broken off in de- 

 tached parts ; in some cases exposing the quick, or opening 

 new ppres, into which particles of earth or sand force their 

 way, until, reaching the quick, an inflammation is set up, 

 which, in its progress, alters or destroys the whole foot. 



" The finest and richest old pastures and lawns are particu- 

 larly liable to this disease, and so are soft, marshy, and lux- 

 uriant meadows. It exists to a greater or less extent in 

 every situation that has a tendency to increase the growth 

 of the hoofs without wearing them away. 



" Sheep that are brought from an upland range of pasture 

 are more particularly subject to it. This is very easily ac- 

 counted for. By means of the exercise which the animal 

 was compelled to take on account of the scantier production 

 of the upland pasture, and also in consequence of the greater 

 hardness oi the ground, the hoof was worn down as .fast as 

 it grew ; but on its new and moist habitation, the hoofs not 

 only continued to grow, but the rapidity of that growth was 

 much increased, while the salutary friction which kept the 

 extension of the foot within bounds was altogether removed. 

 When the nails of the fingers or toes of the human being 

 exceed their proper length, they give him so much uneasi- 

 ness as to induce him to pare them, or if he neglects this 

 operation they break. He can pare them after they have 

 been broken, and the inconvenience soon ceases, and the 

 wound heals. When, however, the hoof of the sheep ex- 

 ceeds its natural length and thickness, that animal has no 

 power to pare them down, but there long continues a woun,d, 

 irritated and induced to spread, by the exposure of its sur- 

 32* 



