154 



THE ESSENTIALS OF HISTOLOGY. 



A B 



FIG. 178. 



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



(Waldeyer.) 



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

 by a horseshoe-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 I>ASSI_\<; 



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



(Kolliker.) 



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 HAVING INDENTED THE ENAMEL-GERM, WHICH HAS AT THE SAME 

 TIME GROWN PARTLY ROUND IT. (Kolliker.) 



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

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

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



