ANATOMY OF THE FOOT. 223 



blood-vessel, and produces what is called a corn, but which 

 is, in fact, a bruise. 



The horny frog occupies the greater part of the trian- 

 gular space between the bars, and extends from the hinder- 

 most part of the foot to the centre of the sole, just over 

 the point where the bars meet ; but is united to them only 

 at their upper edge : the sides remain unattached and 

 separate, and form the channels called the "Commissures." 



If we carefully observe the form and size of the frog 

 in the foot of a colt of from four to five years old, at its 

 first shoeing, and then note the changes which it under- 

 goes as the shoeings are repeated, we shall soon be con- 

 vinced that a visible departure from a state of health and 

 nature is taking place. At first it will be found large and 

 full, with considerable elasticity; the cleft oval inform, 

 open, and expanding, with a continuous, well-defined, and 

 somewhat elevated boundary ; the bulbs at the heels fully 

 developed, plump and rounded ; and the whole mass oc- 

 cupying about one-sixth of the circumference of the foot. 

 By degrees the fulness and elasticity will be observed to 

 have diminished ; the bulbs at the heels will shrink, and 

 lose their plumpness ; the cleft will become narrower, 

 its oval form disappear, the back part of its boundary 

 give way, and it will dwindle into a narrow crack, ex- 

 tended back between the wasted, or perhaps obliterated 

 bulbs, presenting only the miserable remains of a frog, 

 such as may be seen in the feet of most horses long accus- 

 tomed to be shod. 



The bones proper to the foot are three in number, — viz., 

 the coffin bone, the navicular bone, and part of the coro- 

 net bone : they are contained within the hoof, and combine 

 to form the cofiin joint ; but the smallest of them, the na- 

 vicular bone, is of far more importance as connected with 

 our subject of shoeing, than either of the others ; for upon 



