166 DISEASES OF THE BONES AND ARTICULATIONS. 



bone, more or less deep, as the case may be, the injury being 

 inflicted upon a part of the bone other than its articular end ; 

 whilst caries is confined to the extremities of the loncj bones 

 and cancellated structure of the short and irregular bones ; and 

 when not caused by external injury, is unaccompanied by the 

 formation of pus. Of this we have many examples in navicular 

 disease, bone-spavin, ring-bone, &c. 



Professor Spence says, that " The peculiar obstinacy of a 

 truly carious surface arises from the fact that a large part of it 

 is really dead." This, in my opinion, is necrosis, and when the 

 necrosis occurs in our patients, it is always accompanied by sup- 

 puration. I shall, therefore, distinguish these two terminations 

 of ostitis, when not caused by external injury, as — 1st. Caries or 

 removal of degenerated bone tissue by absorption without sup- 

 puration, commonly found to exist in the articular ends of the 

 bones; and, 2d. ^N'ecrosis, or death of a bone, or a portion of 

 bone, accompanied by suppuration; the dead bone being removed 

 by expulsion or surgical interference. 



Caries may arise from traumatic or idiopathic inflammation 

 of the synovial membrane, or from ostitis commencing in the 

 cancellated structure of the bone, and it may be defined as a 

 slow absorptive process by which the bone becomes eroded and 

 cribriform in appearance, the absorption extending to a distance, 

 the bone converted into a brittle mass, and the surrounding 

 parts more vascular and swollen than in the normal state. Or the 

 destructive process is limited, by a deposition of bony material 

 within the cancellated structure of the bone, rendering it of an 

 ivory-like appearance when cut into, and increasing its density 

 and weight. — (See Fig. 20, page 152.) 



Caries commences in the interior of a bone, and makes its 

 way outwards; the bone acquires a red hue; its articular sur- 

 face becomes soft; its laminal layer and articular cartilage are 

 removed, exposing the cancellated structure, from which vascu- 

 lar processes shoot out in the form of red teat-like granulations; 

 the surface of the opposing bone — forming the articulation — 

 becomes similarly diseased, the granulations from the one bone 

 coalesce with those from the other, and form a vascular connec- 

 tion between the interior of both bones. In this manner the 

 process of anchylosis is commenced. 



When caries is situated in a bone over which a tendon plays. 



