NAVICULAR DISEASE. 



343 



variety of changes, both within its interior and upon its articular 

 suiface ; in one instance, to the deposition of small calcareous 



!FiG. 61 represents longitudinal sections of four navicular bones, sawn 

 through their middle as near as possible. 



1. Healthy bone. Cancelli in their natural condition, with distinct 

 spaces (areolae) between the bony trabeculas. 



2. Early stage of ostitis. The bone presents almost an ivory-like 

 appearance, from exudation (and ossification of the exudate) into the 

 areolar spaces, rendering the bone ahnost solid. 



3. Second stage. Showing rarefaction of the bony tissue, and expan- 

 sion of the areolae ; the inflammatory new formation has been absorbed ; 

 the cancelli are enlarged, and cavities are formed (indicated by the dark 

 spots) by absorption of the bony trabeculse. The exterior of this bone 

 shows no signs of disease. 



4. In this figure both the processes, viz., consolidation and rarefaction, 

 are going on. In the centre and to the left hand, dark spots (foraminse) 

 are seen, indicating the destructive (rarefactive) process ; whilst to the right, 

 and indeed ahnost surrounding the cavities, the bone presents the ivory-like 

 appearance, the natural areolae being filled with bony matter. 2 and 4 

 represent changes that are consonant with those of rheumatoid disease. 



Spots upon and within the cartilage (see No. 2, Fig. 62) 



