7 o 



HISTOLOGY. 



flattened elements. It is in close relation with the surrounding vascular 

 mesenchyma, but no blood vessels penetrate it. The enamel pulp is at 

 first a compact mass of ectodermal cells, but by peripheral vacuolization 

 or by the enlargement of intercellular spaces it forms a network con- 

 siderably resembling mucous connective tissue (Fig. 79). Its slender 

 fibers have been considered as elongated intercellular bridges. The inner 

 enamel cells form a single layer of cylindrical cells separated from the 

 enamel pulp by a cuticular plate, yet connecting with the pulp cells by 

 bridges. Beginning at the summit of the crown the inner enamel cells 



Thickened 5 



oral 

 epithelium. 



Outer enamel cells. 

 Enamel pulp. 



Inner enamel cells 



Free edge of 

 the dental ridge. 



Papilla. 



vK - '...'./^W^Tyv 

 ^*W '-:=:,: 



FIG. 78. FROM A CROSS SECTION OF THE UPPER JAW OP A HUMAN EMBRYO 

 FIVE MONTHS OLD. X 42. 



produce cuticular basal plates which become long and slender, and later, 

 calcified. They extend from the enamel cells toward the dental papilla. 

 These are the enamel prisms, and the cells which produce them are called 

 adamantoblasts [ameloblasts]. The formation of enamel prisms spreads 

 from the summit over the sides of the crown and neck, but although the 

 root is enveloped in the enamel organ, no prisms are formed there. The 

 inner enamel cells of the root flatten and by disappearance of the enamel 



