THE DEOTI^E-GERM TOOTH-SHAPED. 43 



and around them the connective tissue condenses and 

 gives rise to the walls of the follicle. It will therefore 

 be seen that the enamel-organ is a dependency of the 

 epithelium, and the dentine-organ a production of the 

 mucous derma. 



"Formation of the Dentine, Enamel, and Cement. 

 As before said, the germ of the dentine has exactly the 

 form of the future tooth; consequently the dentine 

 which arises from its periphery presents the shape of 

 a tooth also. The dentine and enamel are developed 

 by the modification of the elements situated at the 

 surface of their germs. The dentine is constituted of 

 the cells of the germ, which send out ramifying and 

 communicating prolongations the dentinal fibers 

 and by an intercellular substance, which is impreg- 

 nated with calcareous matter, and which, being molded 

 around the fibers, forms canaliculi. The enamel is 

 derived from the deep cells of its germ, which are 

 elongated and prism-shaped, and are calcified in be- 

 coming applied to the surface of the dentine. The 

 cement is developed at the expense of the walls of the 

 follicle, according to the mode of ossification of the 

 connective tissue. 



"Eruption. As the dentine is formed, the tooth 

 increases in length and presses the enamel-germ up- 

 ward. The latter, constantly compressed, becomes 

 atrophied, and finally disappears when the tooth has 

 reached the summit of the follicle. In the same way 

 the young organ pierces the dental follicle and gum 

 and makes its eruption externally. 



"Such is the mode of the development of the tem- 

 porary teeth, and the permanent ones are formed in the 

 same manner. During the development of the germ 

 of the temporary tooth, a bud is seen detaching itself 



