224 



STRUCTURE OF DENTINE. 



The dentine or ivory which surrounds the pulp-cavity and the canal of the fang (fig. 163) is 



very firm, elastic, and brittle. Dentine, like the matrix 



of bone, when treated in a certain way, presents a fibrillar 



structure. It is permeated by innumerable long, tortuous, 



Enamel. 



Dentine. 



Pulp 

 Cavity. 



Cement. 



Fig. 163. Fig. 164. 



Fig. 163. Longitudinal section of an incisor tooth. Fig. 164. Transverse section of dentine. 

 The light rings are the walls of the dentinal tubules ; the dark centres with the light points 

 are the fibres of Tomes lying in the tubules. Fig. 165. Interglobular spaces in dentine. 



wavy tubes the dentinal tubules each of which communicates with the pulp-cavity by means 

 of a fine opening, and passes more or less horizontally outwards as far as the outer layers of the 



dentine. The tubules are bounded by 

 an extremely resistant, thin, cuticular 

 membrane, which strongly resists the 

 action of chjemical reagents. These 



Fig. 166. Fig. 167. 



Fig. 166. Section of a tooth between the dentine and enamel, a, enamel ; c, dentinal tubules ; 

 B, enamel prisms highly magnified ; C, transverse sections of enamel prisms. Fig. 167. 

 Transverse section of the fang, a, cement with bone-corpuscles ; b, dentine with tubules ; 

 c, boundary between both, 



tubules are filled completely by soft fibres, the "fibres of Tomes," which are merely greatly 

 elongated and branched processes of the odontoblasts of the pulp. 



