54 



CELL DIFFERENTIATION AND THE ELEMENTARY TISSUES 



cavity. The relation of these processes to the tubules in which they lie is 

 precisely similar to that of the processes of the bone corpuscles to the canalic- 



Dentine. 



Enamel. 



Cement. 



Periosteum of 

 alveolus. 



Cement. J 



Lower jaw bone. 



FIG. 62. Premolar Tooth and Surrounding Bone of Cat. 



ali of bone. The outer portion of the dentine, underlying the cement and 

 the enamel, figure 63, 6, c, contains cells like bone corpuscles. 



FIG. 63. Section of a Portion of the Dentine and Cement from the Middle of the Root 

 of an Incisor Tooth, a, Dental tubuli ramifying and terminating, some of them in the 

 interglobular spaces b and c, which somewhat resemble bone lacunse; d, inner layer of the 

 cement with numerous closely set canaliculi; e, outer layer of cement;/, lacunae; g, canalic- 

 uli. X 350. (Kolliker.) 



Enamel. The enamel, which is by far the hardest portion of a tooth, 

 is composed chemically of the same elements that enter into the composition 



