THE STRUCTURE OF THE ELEMENTARY TISSUES. 



77 



the enamel germ and the inclination outward of the deeper part (fig. 

 78, B,/')> which is now inclined at an angle with the upper portion or 

 neck (/), and has become bulbous. After this there is an increased de- 

 velopment at certain points corresponding to the situations of the future 

 milk-teeth. The enamel germ, or common enamel germ, as it may be 

 called, becomes divided at its deeper portion, or extended by further 



Fig. 77. 



Fig. 77. Thin section of the enamel and a part of the dentine, a, Cuticular pellicle of the 

 enamel (Nasmyth's membrane); 6. enamel fibivs, or columns with fissures between them and 

 cross striae; c, larger cavities in the enamel, communicating with the extremities of some of 

 the dentinal tubuli (d). X 350. (Kolliker.) 



Fig. 78. Section of the upper jaw of a foetal sheep. A. 1, Common enamel germ dipping down 

 into the mucous membrane; 2, palatine process of jaw; 3, rete Malpighi. B. Section similar to A, 

 but passing through one of the special enamel germs here becoming flask-shaped; c, c', epithelium 

 of mouth; /, neck; /', body of special enamel germ. C. A later stage; c, outline of epithelium of 

 gum; /, neck of enamel germ: /', enamel organ; p, papilla; s, dental sac forming; fp, the enamel 

 germ of permanent tooth; m, bone of jaw; v, vessels cut across. (Waldeyer and Kolliker.) Copied 

 from Quain's Anatomy. 



growth, into a number of special enamel germs corresponding to each 

 of the above-mentioned milk-teeth, and connected to the common germ 

 by a narrow neck. Each tooth is thus placed in its own special recess in 

 the embryonic jaw (tig. 78, B, //'). 



