338 DISEASES OF THE HORSE'S FOOT 



probing is seen to lead direct to the position in which we 

 know the cartilage to be, we know of no precise means by 

 which the existence of this condition may be diagnosed. 

 When free from other complications, the horse with his 

 foot in this state may travel fairly sound. This is so when 

 the necrosis is situated in the posterior half of the cartilage, 

 in which case the irritation set up by the disease is confined 

 to the comparatively non-sensitive tissues of the cartilage 

 itself and the fibrous mass of the plantar cushion. When 

 attacking the anterior half of the cartilage, the close con- 

 tiguity of the joint renders the disease of a more serious 

 nature. It is then that we have acute pain, and with it 

 extreme lameness, for in this position it is more than likely 

 that we have involved either the synovial membrane of the 

 articulation or the tops of the sensitive laminae. It will be 

 remembered that here the synovial membrane protrudes as 

 a small sac between the antero- and postero-lateral liga- 

 ments of the joint. More or less easily then it is bound to 

 come into intimate contact with the septic matter attending 

 the necrosis of the cartilage, and so share in the inflam- 

 matory processes, afterwards communicating them to the 

 interior of the articulation. 



With necrosis of the lateral cartilage is always swelling 

 and thickening of the skin and subcutaneous structures of 

 the coronet. This is the greater the longer the disease has 

 been in existence. Upon the swelling is seen the mouth of 

 the fistula, or it may be the mouths of several, and from 

 them all a discharge of pus. 



The mouth of each fistula is generally filled with a 

 mulberry-like granulation tissue, standing above the level 

 of the skin, and bleeding easily if touched. The exuding 

 pus is thin and pale gray in appearance, gritty to the 

 touch, and generally free from pronounced smell. At 

 other times its colour is reddened with contained blood, 

 and floating in it are tiny particles of a pale-green sub- 

 stance, which when picked up and rubbed between the 

 fingers are seen to be small fragments of the diseased 

 cartilage. 



