72 HORSES AND ROADS. 



of elasticity, expansion, and contraction to obviate 

 all danger from concussion. 



As regards wear and tear there is nothing to 

 fear ; for, as ' Kangaroo ' wrote in the < Field,' ' it 

 is impossible for a horse to become footsore in the 

 frog, sole, or heel of his foot, as a result of travel- 

 ling barefoot.' The horn of which the frog is formed 

 differs from the horn of the sole in nature; and 

 both of them are unlike the horn of the wall, of 

 which latter the description by Mr. Douglas has 

 already been given. The same authority says of the 

 frog : ' In structure the horn of the frog may be 

 compared to horsehair in the compressed state as 

 used for stuffing sofas ; and, if we can imagine this 

 hair to be mixed with a fatty adhesive substance, we 

 shall form a fair idea what the tough elastic frog 

 resembles when under microscopic inspection.' ' The 

 frog is only a continuation of the coronet; and, 

 from its wedge-like form, and nearly total insen- 

 sibility to feeling, proves that it is meant to take a 

 bearing upon the ground, where it is useful to the 

 animal either in action or repose ; in the former it 

 acts as a buffer, preventing concussion, whilst its hold 

 upon the smoothest surfaces prevents slipping.' Of 

 the sole he says : 4 Over its surface there is no glazy- 

 gluey layer to preserve its moisture, as in the crust ; 

 while its fibres, stretched like strings, layer over 

 layer, are as unlike the woolly, oily, substance of the 

 frog as the horn of the crust differs from the bones 

 which it covers. In one respect the sole resembles 

 the frog ; which is, that the outer layer of fibres in 



