act by reason of these restraints, becomes altered In struc- 

 ture ; and the continued operation of the same causes in 

 the end circumscribes the elasticity to those parts alone, 

 where no nails have been driven ; giving rise to a train of 

 consequences, destructive to the soundness of the foot, and 

 fatal to the usefulness of the horse. 



Before I proceed further in my description, it is desirable, 

 that I should define the exact sense in which I have em- 

 ployed the term elastic throughout this work ; because by 

 the general, and somewhat careless way in which the term 

 is used, it is apt to convey a meaning, that is very nearly 

 the reverse of its true and legitimate signification, and is 

 calculated to lead to an exaggerated notion of the extent, to 

 which the elastic portions of the horse's foot are affected by 

 the weight, and movements of the horse. 



The elasticity of a substance does not consist in a ready 

 yielding to the ap^Dhcation of external force, but in its pos- 

 sessing such a jDOwer of resistance to tliat force, as shall 

 enable it to retract with a bound, and regain its former 

 perfect, shape and jaosition, the instant the opposing force 

 is withdrawn. 



Indian rubber lias been sometimes erroneously supposed to 

 represent a perfect type of elasticity ; but the quality of 

 the elasticity of Indian rubber would furnish a very inade- 

 quate standard, whereby to judge of the quality of the 

 elasticity, which is possessed by the component parts of the 

 horse's foot. The difference between them may be described 

 thus ; in Indian rubber the power of yielding to external 

 force is considerably greater, than the power of retracting, 



