

Fig. 188. 



Fig. 189. 



Figs. 186-189. ^ our stages in the development of a tooth in a sheep embryo (from 

 the lower jaw) ; Fig. 186, Anlage of the enamel germ connected with the oral epithelium 

 by the enamel ledge ; Fig. 187, first trace of the dentinal papilla ; Fig. 1 88, advanced 

 stage with larger papilla and differentiating enamel pulp ; Fig. 189, budding from the 

 enamel ledge 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. 1 86, 187, and 188, X IIQ 5 Fi g- l8 9> X 4- <* a > a > a -> Epithelium 

 of the oral cavity ; ^, 3, b, b, its basal layer; c, c, c, the superficial cells of the enamel 

 organ ; d, d, d, d, enamel pulp; /, />, /, dentinal papilla ; .r, j, enamel-forming elements 

 (enamel cells) ; o, odontoblasts ; S, enamel germ of the permanent tooth ; v, part of the 

 enamel ledge of a temporary tooth ; u, surrounding connective tissue. 



245 



