388 DISEASES OF THE HOUSE'S FOOT 



necrosis ensues. It may also result from the extension of 

 inflammatory afi'ections of the structures adjoining it, as, 

 for instance, the spread of the infective material in severe 

 tread, or the encroaches made by pus in cases of quittor, 

 suppurating corn, or complicated sand-crack. 



When the necrosed portion of bone is small, and is 

 free from infective properties, it is quite possible that it 

 may, as is the case with small spots of necrosis in softer 

 tissues, be removed by a process of absorption. It must 

 be remembered, however, that where the necrosis has 

 occurred as a result of septic invasion this cannot be looked 

 for, for in every case such reparative changes are worked 

 solely by healthy tissue. If the tissues around the necrosis 

 are engaged in dealing with organismal invasion and the 

 poisonous products thus poured into their working area, 

 their state of health is so weakened that they are unable to 

 successfully combat with the two conditions simultaneously. 

 As a consequence, the necrotic piece of bone persists, and 

 acts as a permanent source of irritation. 



It must be remembered, too, that if the dead portion of 

 bone — even though it be free from septic matter — is very 

 large, that it may itself act as a continual irritant, in which 

 case it again persists, and cannot by natural means be 

 removed. 



In our cases necrosis of bone may be met with in punc- 

 tured foot, in severe cases of tread, in cases of complicated 

 crack, and in suppurating corn. It is met with, too, in 

 navicular disease, in the extension of irritating discharges 

 in cases of quittor, and in cases of chronic laminitis where 

 the solar margin of the os pedis has penetrated the sole. 

 In this latter case the protruding portion of bone is quickly 

 denuded of its periosteum. Its blood-supply is destroyed, 

 and necrosis follows. 



TreatDicnt. — In simple cases of periostitis, those caused 

 by a blow but free from an actual wound, the most bene- 

 ficial treatment is the continued application of cold by 

 means of a hose-pipe or by swabs. If by these means we 

 are successful in holding the inflammatory phenomena in 



