HORSESHOEING. 59 



sole, and frog as hollow cylinders or tubes, though they are not always 

 hollow, but are often filled with loosely adjusted, crumbling, broken- 

 down horn-cells. The dark edges of the openings (a) consist of thick 

 layei-s of horn-cells (tube-walls). The entire structure is called a 

 horn-tube, and the lighter-colored masses of horn (Fig. 41, 6) between 

 the tubes are known as intertubular horn. 



With the exception of the homy leaves of the wall and 

 bars, all the horn of the hoof is composed of hom-tubes and 

 intertubular horn. 



The lioni-tubes of the wall, sole, and frog always run down- 

 ward and forward parallel to the direction of the wall at the 

 toe, — that is, in a direction parallel with the inclination of the 

 hoof as a whole. Although the' wall, sole, and frog differ from 

 one another considerably vnth respect to the size and numl^er 

 of the hom-tubes, the quality of the intertubular horn, and the 

 thickness and strength of the horn-cells, these differences are 

 only of subordinate interest or importance to the horseshoer; 

 but he who desires to learn more of this matter is referred to 

 the work of Leisering & Hartmann, " Der Fuss des Pferdes in 

 Riicksicht auf Bau, Verrichtungen und Hufljesehlag," eighth 

 edition, Dresden, 1893. This book also treats of the variations 

 in the quality of hoofs, which is very important for the prac- 

 tical horseshoer to know. It, furthermore, considers the solidity 

 and strength of the horn of the different parts of the hoof. 



With respect to solidity, two kinds of horn are distinguished, 

 — namely, hard and soft horn. The periople, the white line, 

 and the frog are soft horn structures ; the middle layer of the 

 wall and the sole are hard or solid horn. The wall, however, 

 is somewhat harder and more tenacious than the sole, for the 

 latter passes off in more or less large flakes (exfoliates) or 

 crumbles away on its lower surface, at least in shod feet, while 

 no such spontaneous shortening occurs in the wall. 



Soft horn differs from hard horn in that its horn-cells never 

 become hard and horn-like. It is very elastic, absorbs water 

 quickly, and as readily dries out and becomes very hard and 



