DEVELOPMENT OF THE TEETH 



155 



free from the oral epithelium (Fig. 161). The anlages of the first permanent 

 molars appear at seventeen weeks (180 mm. C H), those of the second molars at 



er;f^r'»n,-v.;i-.r. 



Tip of luHi^iie 



Submaxillary duct 

 Sublingual duct 



rpidermis of lip 



Enamel organ of tooth 



Dental papill 



Meckel's cartilc 

 Bone of mandible 



Pig. 163. — Parasagittal section through the mandible and tongue of a 65 mm. human fetus showing 

 the position of the anlage of the first incisor tooth. X 14. 



six weeks after birth, while the anlages of the third permanent molars or wisdom 

 teeth are not found until the fifth year. The permanent dentition of thirty-two 

 teeth is then complete. 



Enamel pulp—^\ 



Inner enamel layer 

 (ameloblasls ) 



Enamel prisms 



Dentine and 

 dentinal fibers 



Odontoblasts 



Dental pulp—-- 



Fig. 164. — Section through a portion of the crown of a developing tooth showing the various layers 



(after Tourneux in Heisler). 



The internal cells of the enamel organs are at first compact, but later by the 

 development of an intercellular matrix the cells separate, forming a reticulum 

 resembling mesenchjone, termed the enamel pulp (Fig. 162). The outer enamel 



