DIGESTIVE SYSTEM. 



171 



Epithelium. 



the dental ridge. Early in the third month this 

 dental ridge pro- 

 duces lateral proc- 

 esses along its lin- 

 gual side, one for 

 each deciduous 

 tooth. These epi- 

 thelial processes or 

 sacs are known as 

 enamel organs and 

 develop directly into 

 the tooth enamel. 

 A little later, during 

 the third month, a 

 second set of proc- 

 esses comes from the 

 lingual side of the 

 dental ridge and in 

 like manner forms 

 the enamel organs of 

 the permanent set of 

 teeth. 



The origin of the 

 dentin is closely 

 associated with the 

 enamel organs but 

 comes from the con- 

 nective tissue under- 

 lying these organs. 

 This connective tis- 

 sue forms dental 



Germ for per- 

 manent tooth. 



Enamel. 

 Enamel cells. 

 Dentin. 



Odontoblasts. 



Pulp. 



Fig. 124. Diagram illustrating the de- 

 velopment of a tooth. 



