THE TEETH. 



631 



aliculi run in bundles and in a slightly irregular, wavy course. Then we see a 

 broad portion of fully developed dentine, the canalieuli of which do not reach 

 the cementum, but beneath the latter are replaced by a coarsely granular net- 

 work. On the outer surface appears the relatively narrow layer of cementum 

 of a lamellated structure. Higher magnifying powers of the microscope give 

 an insight into the minute structure of the dentine and cementum. In the 

 layer of dentine the terminations 

 of the dentinal fibers are seen PC- 

 bifurcated, and leading toward 

 the light reticulum, in which we 

 assume the presence of living 

 matter. The lamellated cemen- 

 tum is provided with a number 

 of curved spindles, which in their 

 general direction correspond to 

 the course of the dentinal fibers, 

 while the basis-substance be- 

 tween the spindles appears finely 

 granular. On that portion of the 

 cementum of the root which is 

 provided with cement corpus- 

 cles a distinct boundary be- 

 tween dentine and cementum 

 is wanting. (See Fig. 272.) In 

 this tooth, therefore, the cement- 

 layer is replaced by a regularly 

 developed layer of dentine, the 

 former being very thin, and, with 

 the exception of a limited por- 

 tion, devoid of cement-corpus- 

 cles. 



In the crown a conical por- 

 tion, the blunt lower end of 

 which binds the pulp-cavity, 

 exhibits a structure which 

 doubtless has all the essential 

 properties of dentine, though in 



FIG. 271. EOOT OF AN ANOMALOUS 

 CANINE TOOTH. 



D, primary dentine ; LD, secondary dentine, com- 

 posed of two zones ; JP, pulp ; C, cementum ; PC, 

 pericemeutum. Magnified 300 diameters. 



a considerably more irregular 

 arrangement than ordinary den- 

 tine. The regular dentine ter- 

 minates almost abruptly all 

 around the cone of the irregular 

 dentine. On the apex of the 

 latter, large, irregularly shaped, branching spaces are visible, all of which 

 contain partly nucleated bioplasson formations. (See Fig. 273.) The spaces, 

 and respectively their tenants, are mainly pear-shaped, with their bases 

 directed toward the regular dentine, with their elongations passing into the 

 irregular dentine. From the broad bases arise numerous conical offshoots, 

 by means of which a direct communication is established with the dentinai 

 fibers of the regular dentine, while other offshoots inosculate with analogous 

 formations on the ape*, thus producing a coarse net- work. From the pointed 



