388 DISEASES OF THE HORSE’S FOOT 
necrosis ensues. It may also result from the extension of 
inflammatory affections 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. 
Treatment.—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 
