DISEASES OF BONES 209 



It is especially frequent in the shin-bones of young race-horses, where 

 it is commonly known among trainers and stablemen as " sore shins ". 



Periostitis may be acute or subacute. In the former case it soon 

 spreads to the bone, and may cause portions to die and to slough. In 

 the latter, which is the more common form of tlie disease in the horse, 

 the action is of a more formative kind, and usually results in the thicken- 

 ing of the periosteum and the formation of new bone. 



Two factors are concerned in this destructive process: — 1. Exudation 

 is thrown out from the vessels within the bone into the minute canals 

 which they traverse. This continuing, the vessels are pressed upon by 

 the exuded matter, and the circulation of blood being thereby interfered 

 with the nutrition of the bone suffers accordingly. 



2. Exudation also takes place from the vessels beneath the periosteum, 

 lifting the membrane away from the bone, with the result that a portion 

 of the latter dies, partly from want of the nourishment which the vessels 

 of the periosteum afford to it, and partly also from pressure on the vessels 

 of the bone itself by the matter exuded around them. 



Separation of the dead piece of bone from the living must in such 

 circumstances take place. During this process abscesses form over the 

 site of the injury, and pus (matter) is discharged by one or more openings 

 in the skin. 



Symptoms. — Acute pain, great heat, and lameness are early svmptoms 

 of the disease. Pressure over the part causes sudden withdrawal of the 

 limb. Swelling soon appears — at first firm, then less resisting, and ulti- 

 mately fluctuating. An abscess forms and breaks, and finally the dead 

 bone, if not removed by an operation, ci'umbles away and escapes in small 

 particles with the pus. 



Treatment. — Perfect rest is the first requirement in these cases. An 

 incision should be made through the periosteum as soon as the disease is 

 found to exist. This will afford an opportunity for the escape of matter as 

 it is formed, and prevent any serious separation of the membrane from the 

 bone by its accumulation beneath it. Where this has already taken place 

 it is desirable to make a bold opening, and after irrigating the wound 

 freely with antiseptic solution continue the treatment on the principles 

 laid down for dealing with wounds on the antiseptic system. It should 

 not be overlooked to remove any dead piece of bone that may exist, as 

 soon as it is sufficiently detached to be taken away. 



Acute periostitis is only of seldom occurrence, and perhaps the most 

 common examples are those which occur in the lower jaw as the result 

 of injury inflicted by the bit. Occasionally it is seen in the bones of 

 the extremities after severe blows. 



VuL. U. 48 



