DEVELOPMENT OF THE TEETH 



129 



FIG. 155. 

 A. SECTION ACROSS THE UPPER JAW OF A FCETAL SHEEP. (3 centimeters long.) 



1, common enamel-germ dipping down into the mucous membrane where it is half surrounded 

 by a semilunar-shaped more dense-looking tissue, the germ of the dentine and dental sac ; 

 2, palatine process of the maxilla. 



B. SECTION SIMILAR TO THAT SHOWN IN THE PREVIOUS FIGURE, BUT PASSING 



THROUGH ONE OF THE SPECIAL ENAMEL-GERMS HERE BECOMING FLASK-SHAPED. 



c, c', epithelium of mouth ; /, neck ; f, body of special enamel-germ. 



C AND D. SECTIONS AT LATER STAGES THAN A AND B, THE PAPILLA HAVING BE- 

 COME FORMED AND INDENTED THE ENAMEL-GERM, WHICH HAS AT THE SAME TIME 

 GROWN PARTLY ROUND IT. 



c, epithelium of gum, sketched in outline ; /, neck of enamel-germ ; /', enamel-organ ; e, its 

 deeper columnar cells ; a', projections into the corium ; p, papilla ; s, dental sac forming. 

 In D, the enamel-germ (/ of the corresponding permanent tooth has become formed. 



K 



