The Foot. 060 



Let us observe how perfectly horn of various degrees of 

 moisure, viz., of varying degrees of toughness and elasticity, 

 is provided for in the foot. 



1. The anterior part of the wall is longer than the 

 posterior, therefore the anterior is tougher than the pos- 

 terior, for the reason that the horn is much older at the 

 extremity of the toe than at the heel, and it is further 

 away from the coronet, and therefore contains less moisture. 



2. The wall at the heel is some months younger than at 

 the toe ; it is thinner, and contains more moisture, there- 

 fore it is more elastic, but not so tough. 



^' b''c' dJ e' / 

 Fig. 47.— Diagram illustrating the Age of the Wall. 



a, b, c, d, e,f, are circles drawn around the hoof parallel to the coronet : 

 in this way we ascertain that the age of the wall at a is the same 

 as the heel at a', the age of the wall at d corresponds with the age 

 of the quarter at d'. Every portion of the ground surface of the 

 wall is of a different age, being oldest and hardest at f, and 

 youngest and most elastic at a'. 



The age of the wall is, therefore, an important factor in 

 the wear of the foot. The horn of the quarter is older 

 than the horn of the heel, and the horn of the toe older 

 than that of the quarter. This excellent provision for 

 wear admits of that considerable friction between the 

 ground and the toe which occurs during progression, and 

 allows of the expansion of the younger and moister horn of 

 the posterior part. I am not aware that this explanation 

 of the different ages of the wall has ever before had atten- 

 tion directed to it. 



The expansion of the wall is aided by the lateral car- 

 tilages, which carry outwards the sensitive lamina?, and so 



