310 



THE TEETH. 



Tliis laminfited structm-e is an indication of the dej^osition of dentinal substance 

 in successive sti^ata in the process of formation of the tooth — the laminae con-e- 

 sponding ■svith the shape of the px^lp-surface at successive stages of the process. 

 Not unfrequently lines, varying in number and breadth, are seen in sections of 

 the fully-formed tooth, conforming in dii'ection with the lamination just spoken 



Fi?. 210. 



Fig. 211. 



:l 1 I ! I I M 



1 f f'l^ M 





Fig. 210.— Vertical Section of the UrpER Part of an Incisor Tooth (from Kolliker). 

 Magnified 7 Diameters. 



a, the pulp-cavity ; b, dentine ; c, arched incremental lines ; </, cement ; c, enamel 

 -with hands indicating the direction of the ranges of fibres ; /, coloured lines of the 

 enamel. 



Fig. 211. — A Sjiall Portion of the Dentine with Interglobular Spaces (from 

 Kolliker). 350 Diameters. 



h, the tubules ; c, portion of incremental line formed liy the interglobular si^accs, ■which 

 are here filled up by a transparent material. 



of (fig. 210. r). They are caused by imperfect calcification of the dentine, which 

 shows little cavities bounded by, and therefore receiving their figure from, minute 

 nodules or globules of dentine, and hence named i/ifr/v/lohnlnr .tjMct'.s (fig. 211. c). 

 The lines themselves may be tenned '• incremental"' lines (Salter), as they repre- 

 sent stages of deposition of the dentine. The tenn " contour lines," which has 

 Ijeen applied to tliem, is inapjjroi^riate, inasmuch as they inter.sect the contour 

 of the tooth. The interglobular spaces, and the globules siu-rounding them, vary 

 in size within wide limits. A layer, in which they are very fine — ffrtiniilfirltij/rrot 

 Purkinje (fig. 208, 2) — is not uncommonly found towai'ds the sui-face of the fang 

 beneath the cement, and sometimes in the crown lieneath the enamel : and it may 

 be noticed that the more superficial of the incremental lines are continued 

 into this layer (see fig. 201). 



