ORIGIN AND DEVELOPMENT OF THE TEETH. 249 



FIG. 71; A 



B Mr. Goodsir's obser- 



vations on this sub- 

 ject being the most 

 minute and accurate, 

 we will very briefly 

 state the result of the 

 facts he has commu- 

 nicated. 



His observations 

 began in an embryo 

 as early as the sixth 

 week. At this pe- 

 riod the superior 

 maxillary bone, 

 within its external 

 alveolar margin, 

 presents a deep, nar- 

 row groove. This he 

 calls the primitive dental groove, the mucous membrane 

 lines it. In the seventh week, appears upon its floor a 



'* y- * 



FIG. 71, A represents the origin and progress of the temporary with the 

 corresponding permanent teeth, after Mr. Goodsir. a Mucous membrane, 

 b Mucous membrane containing a granular mass, c Primitive dental groove. 

 d Papilla on the floor of the groove, e Papilla enclosed in a follicle. / Pa- 

 pilla assuming the shape of a pulp, opercula forming, and reserve cavity seen. 

 g Papilla become a pulp and the follicle a sac, from the opercula closing- 

 h Secondary groove adherent except behind the inner operculum, where a 

 closed cavity of reserve is left for the pulp and the sac of the permanent 

 tooth, i Deposition of tooth substance commencing, j Cavity of reserve re- 



