788 



THE TEETH. 



fore across the direction of the tubules. In these lamellse the sections of 

 the tubules appeared as round or oval apertures, the lamellae having the 

 same relation to the tubules as those of true bone to the canaliculi. The 

 same tendency to lamination may be exhibited by boiling a longitudinal 

 section of tooth with caustic potash, after which it presents closely set, short, 

 and regular fissures, lying at right angles to the tubules, throughout the 

 extent of the dentine. (Cleland.) 



Fu. 546. 



~e 



Fig. 546. VERTICAL SECTION OP THE UPPER 

 PART OF AN INCISOR TOOTH (from Kol- 

 liker). f 



a, the pulp-cavity ; b, dentine or tubular 

 substance ; c, arched contour lines with inter- 

 globular spaces ; d, cement ; e, cuamel with 

 an indication of the direction of the columns ; 

 /, coloured lines of the enamel. 



Fig. 547. A SMALL PORTION OP THE DENTINE 

 WITH INTEHGLOBULAR SPACES (from K61- 

 liker). 3 f 



6, the tubules ; c, the interglobular spaces 

 filled with air. 



A laminated structure of a more distinct description has been observed 

 in the dentine of the crown, giving rise to the appearances in longitudinal 

 sections termed contour lines. Czermak states that transverse sections of 

 the tooth present concentric lines resembling the year-rings of wood : and 

 Salter has shown that decalcified specimens readily break up in these lines ; 

 the crowns of the teeth consisting of a series of superimposed hollow 

 cones : the intervals between their strata, in longitudinal sections, appearing 

 as contour markings, in transverse sections as annular lines ; in both cases 

 corresponding with the surface of the pulp, as it existed during the forma- 

 tion of the tooth. The contour markings, when examined with the micro- 

 scope, are seen to be caused by irregularities of the intertubular tissue, 

 which, opposite these marks, presents the appearance of spaces or clefts 

 bounded by globular masses of the ordinary tubular and dense substance. 

 These globules vary in size from -^oth to TQ^TTO^ f an * ncn 5 tne largest 

 being in the crown, the smallest in the fang. The tubuli pass through these 

 globules, and appear to be continuous in direction across the interspaces 

 from one globule to another. 



