1558 



HUMAN ANATOMY. 



dental ledge becomes more and more attenuated until finally it is broken ; its remains 

 appear for some time as nests or islands of epithelial cells embedded within the young 

 connective tissue of the alveolar border. 



The Dental Papilla. This structure first appears shortly after the beginning 

 expansion of the club-shaped developing enamel-organ as a condensation of the meso- 



FIG. 1317. 



Dental ledge 



Thickened 

 oral epithelium 



Mesoblast 



Mesoblast 



&S*p2 



Oral epithelium. 



Mesoblast 



9E53&sf&Sm& 



.:X-:' - ' 

 I :?.>>' X^ >s.V > ..>.; 



D 



i!vlM_ 



^ : ' ' , , ;,;. ^ 1^ Outer layer 



' ' ' ' ' ' of c-name! 



; '.. '.;,, "ixan 



Inner layer 



of enamel- 

 organ 



Dental . 



papilla 







ES(LQjf^SK^ I'jMi.lille laver 



IVntal 

 papilla 



i Kpillu-lial 

 .'.' sheath 





Frontal sections, showing four early stages of tooth-development. A, B, X 100; C, D, X 60. 



1.1.i->t Ix-ncath ilx- epithelial iiionuvtli. The papilla consists for a time of a close 

 -ati.ui ..(' small, round, proliferating r-lls ; with the diftVivntiation of the layers 

 of the enaiiK-1 oi-Maii, the elements occupying the periphery of the dental papilla 

 I.e. ..me elon-ate<l and arian-ed as a continuous row of cylindrical cells over the api- 

 cal portion ol the papilla beneath the capping enamel-or^an. These cylindrical meso- 

 hlaMic cells are the t>t/,>n/,i/n'<i<;fs, the active agents in the formation of the dentine. 



