156 



LAMENESS OF THE HORSE 



alteration in the shape of the foot is brought about by pressure 

 on the pad, which widens and in consequence presses on the bars. 

 The pressure received by the pad is also transmitted to the plan- 

 tar cushion, which likewise flattens and spreads under pressure. 

 Both of these factors force the cartilages slightly outwards. 

 When the posterior Avail recoils the cartilages are carried back 

 to their original position. Should the elastic cartilage under 

 pathological conditions become converted into bone, its functions 

 are destroyed, and lameness may occur. 



Etiolog-y and Occurrence.— The causes of ossification of these 

 cartilages are several. No doubt there exists a predisposition 

 to this condition for it is of such frequent occurrence in heavy 



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Fig. 31 — Ring!)one and .sidebone. 



draft types of horses. Concussion plays an important role and, 

 according to Holler's^ theory, which is sound, high heel calks 

 prevent the frog from contacting the ground, and as weight is 

 placed upon the foot "the lateral cartilages are subjected to a 

 continuous inward and downward dragging strain." 



The condition affects the cartilages of the fore feet more fre- 

 quently than those of the hind and the outer cartilage is more 

 often ossified than is the inner. This fact may be accounted for 

 by its more exposed position ; it is also frequently injured by 



'Moller's Regional Veterinary Surgery, by Dollar, page 630. 



