NOTES ON SHOEING OF HORSES. 7 



7. The strength and toudmess of the crust Effect of 



o o rasjiing the 



de^Dends on the maintenance of its structure whole crust. 

 and uninjured. Any fihng or rasping, as it is 

 called, destroys its gluey superficial layer, and as 

 a natural consequence the nutritive and adhesive 

 oily material between the fibres evaporates. If the 

 rasping be continued, the coats of the outer fibres 

 become injured, and the oily material contained 

 in them also dries up. Further rasping may cut 

 through and destroy the fibres themselves. 



The crust or horn, when deprived of its moisture, 

 not only becomes dry, but also shrinks and contracts. 

 Again the pressure on the sensitive parts of the foot 

 caused by this contraction produces heat, which 

 reacting on the crust dries up whatever little 

 moisture may be left in it, and produces increased 

 dryness, brittleness, and still further contraction. 



The disposition of horn to contract under the 

 influence of heat and want of moisture may be very 

 readily demonstrated by exposing a small piece to 

 heat. If a whole hoof be exposed to this action, 

 it will be found that the first effect is to cause the 

 heels to curl in, and then gradually the quarters, 

 and indeed all parts, contract. In the Hving foot 

 the injurious effects of heat and dryness are per- 

 fectly similar. 



8. Nature, it may be said, can and does reproduce JJ^^^J"™*^^ 

 fresh oily material and moisture in lieu of that which "«* ^«- 



*^ stoieu. 



