CONNECTIVE TISSUES TEETH. 



77 



epithelium dips into the subjacent mucous tissue, presenting on section the 

 form of a short tubular gland (Fig. 38), but really constituting an epithelial 

 fold along the whole length of the jaw. As this fold deepens and enlarges 

 a projection of the mucous tissue takes place in the opposite direction. 

 (Fig. 39/.) This projection or papilla is the dentine germ. By its growth it 



FIG. 38. 



FIG. 39. 



FIG. 38. Vertical section of the Upper Jaw of a Foetal Sheep, about 2% inches long, showing the 

 enamel germ, with the semilunar rudiments of the dentine germ and dental sac in transverse section. 

 1, Dental groove ; 2, palatal process, magnified 50 diam. 



FIG. 39. a, Epithelium. &, younger layer of Epithelium, c, inferior layer of the Epithelium, e, 

 enamel organ. /, dentine germ or papilla, g and h, inner and outer layers of the sacculus that is 

 about to form. 



assumes the form of a club-shaped mass, and the enamel organ invests it like 

 a cap. (Fig. 40.) The first papilla appears at the end of the seventh week, 



FIG. 40. 



Vertical section of the Lower Jaw of a Human Fo3tus, measuring about four inches in length, mag- 

 nified 25 diam.: 1, dental groove; 2, remains of the enamel germ; 3, enamel organ, presenting epi- 

 thelium on both its outer and inner surface, i. e., where it lines the sacculus and where it covers the 

 papilla; 4, enamel germ of the permanent tooth; 6, dentine germ ; 6, section of inferior maxilla; 7, 

 Meckel's cartilage. The dental sacculus will be observed to present a number of fine papillse opposite 

 the dental papilla. 



and is the germ of the anterior temporary molars ; at the eighth week that 

 for the canine tooth appears ; at the ninth those for the central and lateral in- 



