140 



CHORDATE ANATOMY 



growth lines 



in enamel 



pulp chamber 



growth lines 



in dentine 



root canal 



oral epithelium 



osteoblasts 



of periosteum 

 of alveolus 



connective- 

 tissue fibers 



cementoblasts 

 ( from 

 dental sac) 



bone of 

 mandible 



blood vessels 

 and nerves 



Fig. 127. — Schematic diagram showing the topography of a tooth and its relations 

 to the bone of the jaw. The numbered zones indicate empirically the sequence of 

 deposition of the dentine and enamel. The so-called growth lines in the dentine and 

 enamel follow the general contours indicated by the dotted lines in the figure but are 

 much more numerous. (From Patten's "Embryology of the Pig.") 



/DENTINE CANAL 



ODONTOBLASTS 



Fig. 128. — Diagrams illustrating the difference in the secretion of dentine, .4; and 

 of bone, B. The functional polarization of the odontoblasts and osteoblasts is, how- 

 ever, similar. (Redrawn after Braus.) 



