70 



TITE CONNECTIVE TISSUES 



[CH. V. 



without doubt, have to do also with its nutrition. These prolonga- 

 tions from the tooth-pulp are processes of the dentine-cells or odonto- 

 Uasts, the columnar cells lining the pulp-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 canaliculi of bone. 

 The outer portion of the dentine, underlying the cement, and the 

 enamel to a much lesser degree, forms a more or less distinct layer 

 termed the granular or inter globular layer (fig. 95). It is characterised 



FIG. 95. Section of a portion of the dentine and cement from the middle of the root of an incisor tooth, 

 a, Dentinal tubules ramifying and terminating, some of them in the interglobular spaces b and c ; d, 

 inner layer of the cement with numerous closely set canaliculi ; e, outer layer of cement ; /, lacuna} ; 

 g, canaliculi. x 350. (Kolliker.) 



by the presence of a number of irregular minute cavities. The 

 explanation of these will be seen when we study the development of 

 a tooth. 



Enamel. 



Enamel is by far the hardest tissue in the body ; it is composed of 

 the same inorganic compounds that enter into the composition of 



FIG. 96. Enamel prisms. A, fragments and single prisms of the transversely-striated enamel, isolated 

 by the action of hydrochloric acid. B, surface of a small fragment of enamel, showing the hexa- 

 gonal ends of the fibres with darker centres, x 350. (Kolliker.) 



