ON DENTAL EXOSTOSIS. 45 



seen particularly abundant in the middle of the 

 " coagulable lymph," of an oval or elliptical shape, 

 transparent, homogeneous, and furnished usually 

 with two nuclei (Fig. 5«, Plate IV). Then they may 

 be seen with faintly granular contents and larger 

 nuclei ; and lastly, their interior seems stuffed with 

 a more opaque and denser substance, disposed in 

 large granules, among which the nuclei cannot posi- 

 tively be pointed out (Figs. 5^ and 6, Plate IV). 



When a fang to which these masses of so-called 

 coagulated lymph has been allowed to dry ; or still 

 better, if a section be made, it is at once evident 

 that the spots to which they were attached is the 

 seat of a preternatural deposit of cementum ; and a 

 thin transparent slice submitted to microscopic 

 examination shows the extra cemental deposit as I 

 have above described it, and also the fibrous matrix 

 stiU adherent to its margin, in spite of the rough 

 usage to which it has been subjected in preparing 

 the section. 



Having now investigated the structure of the 

 soft and hard tissues in a tooth subject to exostosis, 

 I think we may reasonably infer the following his- 

 tory of its formation : — Inflammation, excited by 

 some casual or persistent irritation, is set up in the 

 periosteum of the fang, and its usual products 

 effused into the fibrous tissue of which it is formed. 

 These products consist of plasma, or blastema, and 

 exudation corpuscles ; and from these are produced 

 cells, some of which undergo a transformation into 



