DISEASES OF THE BONES 383 
has been partially passed over by the wheel of a waggon. 
It may be, too, that in a case of ‘nail-bound’ a great deal 
of the pain and lameness is due to a simple periostitis 
caused by pressure of the bulged inner-layer of horn upon 
the sensitive structures. 
Simple acute periostitis may also occur in cases where 
an actual wound is in existence, but where such wound, 
fortunately, remains aseptic. We may thus have this con- 
dition accompanying ordinary cases of pricked foot, of treads 
in the anterior region of the coronet, and of accidental 
injuries of other kinds. 
In simple acute periostitis the membrane is thicker and 
redder than normal, and is easily stripped from the bone. 
As it is pulled off it is noticed that there are numerous 
fibril-like processes hanging to its inner surface, and which 
draw out from the substance of the bone. These are simply 
the vessels (bloodvessels and nerves) which, loosened by the 
inflammatory exudate, are readily detached and drawn from 
the Haversian canals into which they normally run. In 
addition to its increased redness, the membrane has a swollen 
and gelatinous appearance owing to its infiltration with the 
inflammatory discharges. Simple acute periostitis may and 
often does end in resolution. On the other hand, it may 
end in suppuration or may become chronic. If the latter, 
then the osteoblasts of the innermost layer become active, 
and abnormal deposits of bone are the result. 
(b) Suppurative Periostitis—This condition simply in- 
dicates that the inflammation is complicated by the presence 
of pus organisms. It is, therefore, a common termination 
of the simple acute form attending the infliction of a wound. 
The wound becomes contaminated, and the case of simple 
periostitis is soon changed into the suppurative form. Once 
having gained entrance to the wound, the pus increases in 
quantity, and slowly runs between the membrane and the 
bone. This, however, it does not do to any large extent, 
showing rather a tendency to penetrate the outer fibrous 
layer and gain the outside of the membrane. 
Suppurative periostitis is met with in foot cases, commonly 
