356 -1 Manual of Veterinary Physiology. 



elasticity on which so largely depends the natural shape 

 and usefulness of the foot becomes impaired, or even 

 destroyed. A museum specimen of a foot will very clearly 

 illustrate our meaning. In its dried condition it is so 

 brittle that, if dropped, it will occasionally fracture like a 

 piece of glass ; place the foot in water for a few days, and 

 it comes out as fresh and elastic as though it had just been 

 removed instead of being probably 20 years old. All the 

 horn has done is to imbibe water, which has entered the 

 minute canals by capillary attraction, and the brittle 

 substance now becomes yielding and elastic. 



We can see how necessary elasticity is in the foot, 

 when we consider the concussion to which it is exposed 

 during work, and which would inevitably lead to its de- 

 struction by fracture or otherwise unless this provision 

 were present. Clinically we are perfectly acquainted with 

 the fractures which do occur in the wall of the hoof from 

 violence. 



One of our main objects in shoeing should be to protect 

 the wall from unnecessary interference ; the removal of the 

 varnish layer of the wall, and the cutting across of some 

 thousands of horn-fibres by the unnecessary use of the rasp, 

 lead to considerable destruction. Even, however, in the 

 most brittle foot that portion of horn nearest to the vascular 

 structures still maintains its elasticity. 



Here is an analysis of the horn of the foot : 



100-oon 100-OQO 10000 



The frog contains the largest amount of moisture, and the 

 wall the least. 



The salts are small, and consist of sodium, magnesium, 

 iron, and silica. 



The foot may be regarded as a duplicate structure, one 

 being a complete counterpart of, and fitting into the other. 



