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 w'ound 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. 



(h) 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 w'Ound 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 



