330 



DISEASES OF THE FEET. 



be said to be forced to expand when the foot is on the ground, 

 and that they actively assist contraction when the weight, which 

 forces the sensitive frog upwards and outwards, is removed from 

 tlie foot. 



It must not be understood that I am advocating the theory 

 that the foot expands upon its inferior surface ; that supposition 

 is now entirely disregarded ; but no one can deny, what is ap- 

 parent to the most ordinary observer, that the foot expands at 

 the coronet and heels ; not the horny foot, but the soft parts of 

 the heels and coronet. To prevent undue expansion of these, 

 the lateral cartilages are placed as elastic sides. 



Ossification of the Lateral Cartilages. — As already stated, side- 



TiG. 58 shows ossification of the lateral cartilages, with 

 fracture of the altered structure upon one side, at its junc- 

 tion with the pedal bone. 



bones are commonly met with in heavy draught horses ; indeed, 

 a great majority of this class is found so affected by the time the 

 animal is six or seven years old ; and this seems to arise from 

 the over-expansion of the cartilages caused by the great weight 

 of the animal. The process of ossification is very often a slow 

 one, unaccompanied by any acute inflammatory action, giving 

 the animal no pain, and causing no lameness. 



The causes of ossification of these cartilages are — hereditary 

 tendency, and shoeing with high calkins. It is generally ad- 

 mitted that the predisposition to side-bones is hereditary, and 



