422 XAYIX ox THE HOESE. 



descends in plates from the coronet to the lower border of the 

 wall. This growth of horn progresses until the horny wall is 

 fully formed. 



The growth of the horny wall has progressed considerably 

 before the horn of the bottom commences to be formed. It 

 commences to form beneath the temporary bottom, and, by the 

 time of birth, the sole, frog, and bars will be formed, but cov- 

 ered by the thick substance of the temporary bottom. But 

 this soon becomes' loose in its texture, and breaks off, so that 

 in a few days the sole and frog are visible. This cover is for 

 the purpose of preventing the hoof from hurting the dam. In 

 the description of the wall I have already spoken of the upper 

 border being as if shaved out for the purpose of receiving the 

 coronary substance, which will hereafter be more fully de- 

 scribed ; but its office must here be spoken of. On the side 

 which lies in contact with the wall there are an infinite num- 

 ber of little points, or mouths, of vessels, called villi. These 

 villi have the power of changing the blood, or parts of it, with 

 which the coronary substance is abundantly supplied, into a 

 peculiar, soft, gluey matter, which becomes changed into true 

 horn as it dries. This gluey matter is poured out from the 

 villi in the form of fine, tube-like hairs, and M'liich descend 

 fi'om the point of their origin in perfectly straight lines to the 

 lower border of the crust, or wall. They are quite soft near 

 their origin, but get harder as they descend. Hence we see 

 that the crust of the horse's foot is made up of a vast number 

 of little tubes, with their sides firmly glued together, so as to 

 present the dense structure it appears to be. These little tubes, 

 or fibers, of horn are arranged in layers, or growths, giving the 

 appearance of a grain to the horn. The coronary frog-band 

 spoken of protects the horn at its origin until it descends far 

 enough to become sufficiently hard to not need this protection. 

 When, from age, heat, exposure, or disease, this coronary frog- 

 band embraces the soft horn beneath it too tightly, it causes 

 the horn to pass out below it, not smooth, as it should be, but 



