434 



HORSE-SHOEING 



outer layer of the wall is the hardest, and thus most capable of resisting 

 wear. It protects the deeper layers, and by j^reventing evaporation keeps 

 them tough and pliant. The evil of rasping is that the exposed horn soon 

 becomes hard, and a repetition or excess of the process renders the hoof 

 brittle. 



When the under surface of the foot is examined, the sole, frog, and bars 

 are seen. 



The sole forms the larger portion of the floor of the hoof. It is con- 

 cave, and hrmly attached to the border of the wall. On a smooth, level 



surface only the outer portion 

 of the sole — that wliich is 

 immediately connected with 

 the wall — takes a direct 

 bearing. But the sole sus- 

 tains its share of the weight 

 of the horse just as an arch 

 supports weight although 

 resting only on its abut- 

 ment. 



The frog is the promi- 

 nent triangular -shaped mass 

 of horn situated at the back 

 part of the under surface of 

 the hoof It extends forward 

 to a point reaching more than 

 half-way to the toe. Its 

 prominent surfiice is broken 

 by a depression which should be shallow, but which is too often a 

 narrow, deep fissure. On each side of the frog is a space separating it 

 from the bars. This space permits lateral yielding when weight is placed 

 upon the frog. It must not be supposed that the frog is an extra thick 

 mass of horn resting on a level sensitive foot. Its prominent parts and 

 its depressions follow exactly a similar formation of the sensitive structure 

 under it, and the whole should be left in its full strength. The form of 

 this division of the hoof sua;s[ests its use, which is to form a catch when 

 the foot comes to the ground, and so increase the security of foothold. 

 The structure of the frog is a tough elastic horn, and as the back of the 

 foot comes to the ground first during progression, the frog is well con- 

 stituted to break concussion. 



The bars are the ridges of horn which run on each side of the frog 

 forwards from the heels. They are formed by a turniug-in of the wall at 



Fig. 625.- 



-The Wall of the Foot: Hoof showing 

 Insensitive Laminae, &c. 



A, Peiipolic horn-band. B, Coronary groove, c, Insensitive 

 laminiB. D, Horny sole. E, Horny frog. 



