

FIG. 42. 





fr* 



FIG. 44. 



FIG. 45. 



FIGS. 42-45. Four stages in the development of a tooth in a sheep embryo 

 (from the lower jaw) (Bohm and Davidoff). FIG. 42, anlage of the enamel-germ 

 connected with the oral epithelium by the enamel-edge ; FIG. 43, first trace of the 

 dentinal papilla ; FIG. 44, advanced stage with larger papilla and differentiating 

 enamel-pulp; FIG. 45, budding from the enamel-edge of the anlage of the enamel- 

 germ, which later goes to form the enamel of a permanent tooth ; at the periphery 

 of the papilla the odontoblasts are beginning to differentiate. FIGS. 42, 43, and 44, 

 X HO; FIG. 45, X 40. a, a, a, a, Epithelium of the oral cavity ; 6, 6, 6, 6, its basal 

 layer ; c, c, c, the superficial cells of the enamel-organ ; <?, d, d, d, enamel-pulp ; 

 p, p, p, dentinal papilla ; s, s, enamel-forming elements (enamel-cells) ; o, odonto- 

 blasts ; S, enamel-germ of the permanent tooth ; v, part of the enamel-edge of a 

 temporary tooth ; u, surrounding connective tissue. 



52 



