20 THE CANADIA2T HOBSE 



In the first place, the wound must be freely opened, and the 

 parts touched with dilute hydrochloric acid several times 

 a day. Mineral and vegetable tonics must be given. Where 

 practicable, as on the withers, the diseased portion should 

 be cut off with a fine saw. Occurring in a joint, we must 

 endeavour to produce anchylosis of the joint. 



NECEOSIS OF BONE. 



Necrosis is generally defined to be the entire death or morti- 

 fication of a bone. It differs from caries, in which the bone 

 is discharged in particles ; whereas in necrosis not unfre- 

 quently the whole bone dies and becomes encased in a new 

 bone of exactly the same -shape, which is perforated by 

 numerous holes, through which the old bone exfoliates. 



Causes. — In man it not unfrequently arises from consti- 

 tutional causes — scrofula, &c. ; but in the lower animals it 

 generally arises from local causes, mechanical injuries, exten- 

 sive destruction of the surrounding soft parts, especially if it 

 involves the artery supplying nourishment to the bone. In 

 young, thorough-bred horses, we are familiar with it from 

 sore shins, which arises from the animal being put in train- 

 ing too young. The concussion sets up inflammation of the 

 periosteum, which may be followed by caries, but more com- 

 monly necrosis of the cannon bone. 



Symptoms. — The external appearances do not differ very 

 materially from caries. We have sinuses penetrating the 

 bone, from which there is a copious discharge of most offen- 

 sive smelling matter, in which is occasionally discharged 

 pieces of dead bone, which have escaped through the holes 

 in the new bone : this is called the process of exfoliation. 

 It is easily distinguished from caries by the surface of the 

 bone not being worm-eaten, but smooth, and studded with 



