242 



THE ORGANS 







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Fig. 143- 



Fig. 144. 



L ' '■^•— " '"*'^J 



vrs.: 



■•^r- 6 











.- i' 



o 



Fig. 145. Fig.' 146. 



Figs. 143, 144, 145, 146. — Four Stages in the Development of a Tooth (from lower 

 jaw of sheep embryo). (Bohm-Davidofif.) Fig. 143, Beginning of enamel organ show- 

 ing connection with epithelium of mouth; Fig. 144, Later stage showing same with first 

 trace of papilla; Fig. 145, Later stage showing papilla well formed, the ditTerentiation 

 of the enamel pulp and of the inner and outer enamel cells can be seen; odontoblast 

 appearing along periphery of the papilla; Fig. 146, shows also beginning enamel organ of 

 permanent tooth; Figs. 143, 144, 145, X no, Fig. 146, X40. a, Epithelium of mouth; h, 

 its basal layer; c, superficial cells of enamel organ; d, enamel pulp; p, dental papilla; s, 

 enamel cells; 0, odontoblasts; S, enamel organ of permanent tooth just beginning to 

 differentiate; v, remains of enamel ledge of milk tooth: u. surrounding connective tissue. 



