ON DENTAL EXOSTOSIS. 39 



seen, very great, causing the end of the fang to be as 

 large as the crown, and extending quite to the neck of 

 the tooth. Upon making a section of a tooth thus 

 encrusted, the extent of the hypertrophied mass 

 can be easily distinguished by its colour and texture 

 from the fang upon which it is deposited ; but in 

 stumps its deposition is very uneven, sometimes 

 one side is encrusted, while the other retains its 

 natural appearance; or it exists only as nodules 

 scattered here and there, distinguishable from the 

 original structure by their pearly whiteness. A 

 very common appearance, and one which is frequently 

 ascribed to absorption, is a nipple-like projection of 

 the apex of the fang (Fig. 3, Plate Y). That 

 this is not due to any removal of substance is 

 shown by submitting a thin section of such a stump 

 to a low magnifying power, when it will be seen 

 that the nipple-like portion is still covered with its 

 natural layer of cement, but that an additional 

 deposit has taken place over the rest of the stump, 

 gradually diminishing and blending with the nor- 

 mal tissue towards the carious end, and terminating 

 abruptly in the opposite direction in an elevated 

 thickened border (Plate VII). A thin section of an 

 exostosed fang submitted to a low magnifying 

 power shows that the deposit has taken place layer . 

 by layer, their boundaries being defined by irregular 

 wavy lines, running almost parallel with the border 

 of the dentine (Plates VI. and VII). The limit of 

 the original layer of cementum is usually marked by 



