CHAPTER III 



DEVELOPMENT AND CALCIFICATION OF THE 

 ENAMEL 



1. The Enamel Organ of Mammalia 



As explained in Chapter I, the enamel is developed from 

 the deeper layers of the epithelium of the mouth. It is thus 

 of ectodermic origin, and the several layers of cells into 

 which this involution becomes differentiated are collectively 

 spoken of as ' the enamel organ ' (fig. 68). 



This enamel organ commences as a bud-like process, 

 which grows downwards into the sub -epithelial tissue, and 



FIG. 68. Diagram showing the enamel organ and its connexions 

 before the commencement of calcification, e. Epithelium of mouth 

 m. Malpighian layer ; c. connective tissue ; n. neck of enamel organ 

 ex. external epithelium ; 5. stellate reticulum ; i. stratum intermedium 

 a. ameloblasts ; p. pulp ; b. bone ; t. commencing tooth-sac. 



is formed by an invagination of the Malpighian layer of the 

 oral epithelium. 



The rounded end of the bud becomes indented from beneath, 

 and the sides of this indentation grow round the mesodermic 

 connective tissue which afterwards forms the dentine papilla. 

 It thus comes to have a bell shape, the connecting band 

 with the epithelium of the mouth forming the handle. 



The cells constituting the walls or sides of this inflection, 



