134 A MANUAL OF DENTAL ANATOMY. 



ENAMEL ORGAN. 



The enamel organ, as has already been stated, forms a 

 cap-like investment to the dentine bulb, and it is itself 

 thickest over the apex of the latter, thinning down some- 

 what as it approaches the base. 



It is entirely surrounded by an epithelial layer, which 

 upon the inner surface applied to the dentine bulb consists 

 of much elongated columnar cells, and takes the name of 

 internal epithelium of the enamel organ, and upon its outer 

 surface the name of external epitlielium of the enamel organ. 

 The greater bulk of the enamel organ consists of a stellate 

 tissue, which passes gradually through the medium of a 

 layer of rounded cells, the stratum intermedium, into the 

 enamel cells, or internal epithelium. The essential portion 

 of the enamel organ is this layer of " enamel cells," which 

 by their calcification give rise to the enamel, and in lower 

 animals, such as most if not all reptiles, the whole enamel 

 organ is represented by little else than this layer of " enamel 

 cells." 



The cells of the internal epithelium (enamel cells) form 

 an exceedingly regular and perfect columnar epithelium, 

 the individual cells becoming by result of their mutual 

 apposition very symmetrical hexagons. 



They are four or five times as long as they are broad, and 

 the nucleus, which is large and oval, occupies that end 

 which is farthest from the dentine. It is said by Waldeyer 

 that the sides of the cells only are invested by membrane, 

 the protoplasm being without investment at its two ends. 



Towards the base of the dentine germ, where the internal 

 epithelium merges into the external epithelium, the cells are 

 not so much .elongated, and they then pass gradually into 

 the cubical form of these latter cells. At their attached 

 extremities the enamel cells are prolonged into processes 

 which are continuous with the cells of the stratum inter- 



