OSTITIS. 151 



OSTITIS, OR INFLAMMATION OF BONE, 



May be acute or chronic. It may involve the wliole substance 

 and extent of a bone, or it may be confined to a portion of it 

 (circumscribed inflammation). The causes are external injury, 

 concussion, and hereditary tendency. 



Acute inflammation of bone, involving the shaft, is found to 

 affect young race-horses in the disease termed " sore shins." 

 This disease usually involves the periosteum and external 

 layer of the bone only; and such cases terminate by a 

 deposition being thrown out between the periosteum and the 

 bone, which, becoming organized, forms a permanent thicken- 

 ing, depending more or less upon the degree of the diseased 

 action; but in rare cases the whole of the bone is affected, 

 and the inflammation is of such an acute nature that the 

 vitality of the bone is destroyed; the exudation blocking up 

 the Haversian canals and canaliculi, and thus arresting the 

 nutritive functions. The dense structure of the bone does not 

 permit the blood-vessels to relieve themselves by pouring out 

 their liquid contents, as in the softer tissues, and the part dies 

 by the pressure on its vessels, even when the diseased action is 

 not sufficiently active to produce this death of the bone. Ac- 

 cording to Goodsir, the first changes that occur in the bone are 

 to be distinguished within the Haversian canals. These dilate 

 or become opened up ; and the result of this is the conversion 

 of the contiguous canals into one cavity, and the consequent 

 removal or absorption of all the osseous texture of the part. 



Concurrent with this softening and opening up of the 

 bony texture, an external swelling makes its appearance ; the 

 vessels of the periosteum and contiguous soft parts, becoming 

 involved, throw out a deposit upon the surface of the bone. 

 This exudate, as a rule, becomes converted into bone, leaving 

 the parts permanently altered in shape and appearance ; or it 

 may become absorbed before it is ossified, and the parts regain 

 their former condition. 



The results of inflammation of bone, where resolution does 

 not take place, are either an increased condensation or an 

 abnormal rarefaction. Of both these forms we have good in- 

 stances in most cases of ostitis, whether occurring in the 

 navicular or other bones. (See figures of Navicular Bones.) 



