618 THE TEETH. 



Where a gradual change takes place, the dentinal canalieuli show irregular, 

 mainly spindle-shaped, enlargements, which stand in the direction of the den- 

 tinal canalieuli themselves, or run obliquely through the basis-substance of 

 the cementum. The distal end of such a spindle is, as a rule, in connection 

 with a regular lacuna of the cementum, or with an analogous formation of a 

 neighboring dental canaliculus. Many of the latter simply pass into the light, 

 delicate net-work characteristic of the basis-substance of cementum. The 

 dentinal fiber is in direct union with the bioplasson, which fills the spindle- 

 shaped spaces, or it is lost to sight upon entering the net-work of the basis- 

 substance of the cementum. (See Fig. 264.) 



FIG. 264. TRANSITION OF DENTINE INTO CEMENTUM, 

 WITHOUT A MARKED BOUNDARY. 



C, branching cement-corpuscle ; JP, spindle-shaped cement-corpuscle, both in direct con- 

 nection with dentinal fibers, F, which bifurcate within the canalieuli of the dentine, D. 

 Magnified 1200 diameters. 



Where a boundary with bay-like excavations is present between dentine 

 and cementum, spindle-shaped enlargements of the dentinal canalieuli may be 

 seen, much smaller than in the former instance. The majority of the dentinal 

 canalieuli, however, reach the boundary of the cementum after repeated 

 bifurcations, by which both the calibers of the canalieuli and their central 

 fibers are gradually diminished in size. A connection of the dentinal fibers 

 with the coarser offshoots of the cement-corpuscles is often observed. The 

 light net-work of the basis-substance of the dentine always passes into that of 

 the cementum. Not very rarely, also, on the bottom of a bay-like excavation, 

 partly nucleated plastids are present, into which the dentinal fibers inosculate. 

 The connection between these and the coarser offshoots of the cement-cor- 



