THE DENTINE. 





"When dentine is fractured, it 

 presents a fibrous appearance ; the 

 fibres radiating from the centre to 

 the circumference of the latter. 

 The tubuli, of course, determine 

 their direction; they being merely 

 columns of the solid intertubular 

 substance. 



B. The tubuli of the dentine 

 commence on the internal surface 

 of the dentine, in contact with the 

 pulp. Their general direction is 

 upwards and outwards in the lower 

 teeth, downwards and outwards in 

 the upper. They average T ^^^ 

 of an inch in diameter at their com- 

 mencement, but divide into many 

 smaller subdivisions, separating at 

 acute angles from the main trunk, 

 and at last terminate in the outer 

 surface of the dentine in contact 

 with the enamel or the cementum, 

 as the case may be. (Fig. 232.) 

 The tubuli have a distinct and ap- 

 parently very thick wall, occupy- 

 ing two thirds of the diameter of 

 the whole tube. This appearance 

 is, however, due to the numerous 

 short curves in the tubes, about to 

 be described. They are naturally 

 filled with a clear fluid, for the 

 nourishment of the teeth, and 

 which does not contain salts of 

 lime, as is sometimes stated. 

 Hoppe finds that the walls of the 

 tubuli do not contain gelatine. 



Each tubule presents two or 

 three large curvatures and very 

 many small ones sometimes even 

 2000 within 1 line. (Retzius.) Se- 



Fig. 232. 



V js 



Dentinal tubuli from the fang. a. Inter- 

 nal surface of the dentine, with scattered ca- 

 nals, b. Their divisions, c. Terminations 

 with loops, d. Granular layer, consisting of 

 small dentinal globules at the boundary of the 

 dentine, e. Bone lacuna, one anastomosing 

 with dentinal canals. Magnified 350 diame- 

 ters. (Killiker.) 



