ENAMEL 



55 



of dentine and bone, but the animal matter amounts only to about 2 or 3 

 per cent. It contains a larger proportion of inorganic matter and is harder 

 than any other tissue in the body. 



Structure. Enamel is composed of fine hexagonal fibers, figures 64, 65. 



FIG. 64. 



FIG. 64. Thin Section of the Enamel and a Part of the Dentine, a, Cuticular pellicle 

 of the enamel (Nasmyth's membrane); b, enamel fibers, 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. 65. Section of the Upper Jaw of a Fetal Sheep. A. i, Common enamel germ 

 dipping down into the mucous membrane; 2, palatine process of jaw; 3, rete Malpighi. 

 (Waldeyer.) 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. (Rose.) C. A later stage; c, outline of epithelium of gum; /, neck of enamel 

 germ; /', enamel organ; p, papilla; s, dental sac forming;/^, the enamel, germ of perma- 

 nent tooth; m, bone of jaw; v, vessels cut across. (Kolliker.) Copied from Quain's 

 " Anatomy." 



These are set on end vertical to the surface of the dentine, and fit into cor- 

 responding depressions in the same. 



Like the dentine tubules, they are disposed in wavy and parallel curves. 



