190 



THE STEUCTUEE OF THE HOESE 



adapted to the purpose it has to fulfil. The different 

 varieties of the horny tissue of which it is composed and 

 their complex arrangement recall those of the different 

 constituents of the grinding surface of the molar teeth. 

 The wall or crust completely encircling the front and 

 sides, and reflected inwards and forwards almost to the 

 centre, being composed of a harder and more resisting 

 material than the rest, like the enamel of the teeth, 

 always stands out more prominently than the other 

 structures, and therefore bears the principal weight. 

 The sole is more or less concave, being less dense and 

 its surface exfoliating more readily than the other parts. 

 The projections formed by the elastic plantar cushion, 

 covered by the horny frog and its backward prolonga- 

 tions, when these parts are left in their natural con- 

 dition, also bear much of the weight, and aid in pre- 

 venting the tendency to slip which a uniformly smooth 

 surface would have, though the ease with which they 

 as well as the sole yield to the paring-knife offers a 

 temptation which farriers seem rarely able to resist. In 

 the horse's foot, as it should be, a large part of the 

 under surface comes in contact with the ground, and 

 there is nothing like those deep cavities, which only 

 serve for the lodgment of dirt, or the impaction of 

 stones, seen in the same foot as just returned from 

 the shoeing forge. 



In a state of nature, when the animal is free to 



