176 



DISEASES OF THE BONES AXD ARTICULATIONS. 



ABSCESS IN THE SUBSTANCE OF A BONE. 



The formation of abscess in the substance of a bone is of rare 

 occurrence, and I have only witnessed one marked case of it. 

 The bone is now in my possession, and the two figures represent 

 its external and internal appearances. 



Yui. 27. Fig. 28. 



Fig. 27. — External view of humerus of a horse, v.n.th central abscess. 



Fig. 28. — Internal view of i<ame bone. At a is a well-defined a' 

 containing inspissated pus ; b shows the dilated condition of the medul- 

 lary canal, the cavity being originally filled with pus. 



An abscess may form within the cancellated structure, which 

 is hollowed out, as in the illustration, and is generally situated 

 near the articular extremity of a long bone. The same amount 

 of iullammation necessary to produce pus in the cancelli, would, 

 if situated in the compact tissue, cause necrosis. It is accom- 

 panied by thickening of the outer shell of the bone, as in 

 necrosis. The diagnosis of internal abscess will be very diffi- 

 cult, on account of the depth of its seat. The enlarged bone, 

 with pain, will be our only guides until the pus has pierced 



