256 THE DIGESTIVE SYSTEM 



fine fibres pass to the periphery and form a network of terminal 

 fibrils which end among the odontoblasts. Boll,* though suggest- 

 ing that the terminal nerve fibrils enter the dentinal canals, was yet 

 unable to demonstrate the theory. More recent observers (Eet- 

 zius,f et als.) have likewise been unable to recognize any nerve 

 fibrils beyond the layer of odontoblasts. Boll's theory of nerve 

 fibrils within the dentinal canals, therefore, still lacks satisfactory 

 confirmation. 



Dentine. The dentine surrounds the entire pulp cavity except 

 at the opening of the root canal. It is a fine calcareous substance 

 which resembles bone in that it consists of a fibrous matrix and is 

 infiltrated with lime salts. The matrix is a fine fibrous network 

 of dense connective tissue, the majority of whose fibres are dis- 

 posed in a longitudinal direction. The meshes of the matrix are 

 almost completely filled by a deposit of calcareous salts which 

 gives the dentine its bony consistence. 



Here and there, especially toward its peripheral border and 

 near the apex of the tooth, the dentinal matrix fails to become 

 calcified. Such uncalcified areas, interglobular spaces, are en- 

 croached upon by the rounded or globular margins of the adjacent 

 calcified matrix which forms the so-called dental globules. 



The dentine is everywhere permeated by a system of canaliculi, 

 the dentinal tubules or canals, which extend in a radial manner 

 from the pulp cavity outward to the cementum and enamel. 



b c 



FIG. 215. FROM A SECTION OF A HUMAN TOOTH WHICH HAD BEEN GROUND TO EXTREME 



THINNESS. 

 a, dentine ; b, granular layer of Thomes ; c, enamel. Photo, x 150. 



Their course is characteristically curved, resembling the letter /. 



The cavity of the dentinal tubules is partially occupied by the 



dentinal processes of the odontoblasts, an arrangement which may 



* Arch. f. mik. Anat., 1868. f Biol. Untersuch., 1894, N. F., vol. vi. 



