

DEVELOPMENT OF THE TEETH. 483 



responds to eachof the dentinal germs. Each enamel organ is 

 thus composed of a strongly developed portion that surmounts 

 the dentine germ like a cap, and a narrow cord of cells extend- 

 ing to the epithelium of the mouth the neck of the enamel 

 organ, which represents the remains of the primitive enamel 

 germ (see fig. 101). The neck of the enamel organ disappears 

 at a later period, whilst the two dental ridges coalesce with 

 one another above. The rudiments of the teeth are thus sur- 

 rounded on all sides by the loose connective tissue of the wall 

 of the jaw. 



Histological changes of a very remarkable character occur in 

 the enamel organ, coincidently with the morphological changes 

 that have been described above. The marginal cylindrical 

 cells, where they are in immediate contact with the dentine, 

 appearing as an epithelium covering it, become remarkably elon- 

 gated, and form very regular six-sided prismatic bodies in fact, 

 the most beautiful and regular columnar epithelium found in 

 any part of the animal body (see figs. 102 and 103). The sides 

 of the cells present a distinct limiting membrane; but the 

 protoplasm has no investment at the two extremities. At the 

 base of the dentine germ, where it becomes continuous with 

 the lateral walls of the enamel club, the cells become pro- 

 gressively shorter, until at last they assume a cubical form, and 

 thus coat the portion of the internal surface of the enamel organ, 

 or rather of the dental sacculus, which is turned away from the 

 dentine germ. In accordance with Kolliker (47), we desig- 

 nate the elongated cylinder cells as the internal or enamel 

 epithelium, and the remaining marginal cells as the external 

 epithelium of the enamel organ. As far as the external epithe- 

 lium reaches, the adjoining connective tissue exhibits tolerably 

 regularly formed conical and vascular papillae, which project 

 into the epithelium, and correspond to the papillae found in 

 the remaining portions of the oral mucous membrane (see 

 fig. 101.) 



The complete continuity and concatenation of all these structures is 

 most satisfactorily proved by a recent statement made by Dursy (67), 

 which I am able to corroborate, that especially towards the neck of 

 the enamel germ, similar papillary structures are present, which here 

 pass without interruption into the papillae of the gum. It is only 



