326 THE EXTERIOR OF THE HORSE 



peripheral border expands more and presses against the wall, whose 

 thin and narrow extremities are thus feebly separated from each other. 



The frog is depressed to the same degree ; its median lacuna 

 enlarges; its branches are forced outward and press against the bars 

 propped against them after the manner of two springs. 



Finally, the wall reacts in an opposite direction to the simultaneous 

 pressure of the lateral cartilages, the sole, and the frog. Its superior 

 border and its quarters expand. 



The elasticity of the hoof is manifested, therefore, by a slight 

 movement of separation and approximation of its heels, whose ampli- 

 tude is the greater in proportion as the frog is larger and more related 

 {frog pressure) to the ground, conditions always realized in a state of 

 nature (Figs. 97 and 99). 



Hence rational shoeing should never be an obstacle to the opening 

 of the posterior cleft of the foot at the moment of the contact and to 

 its closing during the elevation. 



The farrier, when paring the foot, must imitate the natural usage 

 and respect that which nature spares : it strongly rounds and shortens 

 the toe, and the mammae a little less ; it affects the sole only at its 

 anterior circumference, without weakening too much its union with 

 the wall ; it rounds more outwardly than inwardly the sharp border 

 of the latter ; removes from the sole, the frog, and the bars only that 

 which is eliminated spontaneously. The foot which has undergone 

 natural usage has been adapted to locomotion, and bears flatly from 

 the mammae to the heels.^ 



Preservation of the Form of the Hoof — The hoof, in a 

 state of nature, the Cotnmission dliygiene hippique^ also says, preserves 

 its form and its qualities under the following conditions : 



1st. Its elasticity is complete when the frog is in full relation with 

 the ground. 



2d. Its constant use maintains a proper length and a regular 



axis. 



3d. The sole has all its thickness, all its strength, and prevents 



contraction of the heels. 



4th. The hairs of the coronet cover and protect the cutidure ; the 

 varnish of the wall (periople) protects the horn against alterations of 

 dryness and humidity. 



5th. Finally, the moisture of the soil, the dew, and the freshness 



1 Manuel de mar^chalerie, r6dig6 par les soins de la Commission d'hygiene hippique, p. 105, 

 Paris, 1876. 



2 Loc. cit., p. 55. 



