FOEM OF THE HEALTHY FOOT. 735 



jected by contact with the ground, when the animal roams about 

 under natural conditions, the horn of the wall is endowed with the 

 property of growing to a practically indefinite length ; though the 

 horn of the sole and frog will not increase beyond a useful limit. 

 The thickness of the sole is regulated naturally by its outer layers 

 of horn exfoliating (flaking off), when the sole has reached its 

 proper thickness. The frog cannot, under ordinary conditions, 

 grow too long ; firstly, because its outer layers, also, flake off ; and, 

 secondly, because it will stop increasing, as soon as it is relieved of 

 pressure by reason of the more rapid growth of the wall. As we 

 require, when shoeing, to utilise the whole of the weight-bearing 

 surface at our disposal, as well as to preserve the horn-secreting 

 membrane from injury ; we may conclude that the sound parts of 

 the frog and of the arched portion of the sole should be left 

 untouched by the knife or other instrument, and that the wall and 

 bars should be kept sufficiently " short," to allow the frog and 

 outer portion of the sole, also, to support weight. 



Fig. 189. — Lowering hoof all round. Fig. 190, — Lowering toe. 



Form of the Healthy Foot. 



1st. The frog is large (Fig. 49, p. 167) and comes well down 

 on the ground, sO' as to act as a buffer in diminishing the effects 

 of concussion, and also, by its form and nature, to prevent the 

 animal from slipping. 



2nd. The sole is thick, strong and arched. 



3rd. On level ground, the weight-bearing surface of the foot 

 is composed of the frog, wall, bars, and the outer portion of the 

 sole. 



4th. The slope of the fore foot, viewed in profile, will as a rule 

 be about 50°; and that of the hind feet will be from 55° to 60°. 

 This difference in obliquity between the hoofs of the different 

 extremities, is due to the fact, that the hind feet are chiefly 

 required for propelling the animal, and the fore feet for supporting 

 his weight ; hence, the wear of the former, at the toes, is greater 



