iS6 



THE DISSECTION OF PIG EMBRYOS 



cells, at first cuboidal, flatten out and later form a fibrous layer. The" inner 

 enamel cells bound the cup-shaped concavity of the enamel organ. Over the 

 crown of the tooth these cells, the ameloblasts, become slender and columnar in 



Dental sac 



Outer layer Innei layer 



\ _ 



0»/fj enamel cells 



\ " ^Lmm i pulp 



\ 'I ,>\ Inner enamel cells 

 imiloblasts) 



— Enamel 



Dental papilla (fiilure pulp) 

 Blood V 



Den! n 



Odontoblasts 



Epithelial sheath 



Bony I al nil f j i — 



Fig. 165.— rLongitudinal section of a deciduous tooth of a newborn dog. X 42. The white 

 spaces between the inner enamel cells and the enamel are artificied and due to shrinkage (Lewis 

 and Stohr). 



form, producing the enamel layer of the tooth along their basal ends (Fig. 164). 

 The enamel is laid down first an an uncalcified fibrillar layer which later becomes 

 calcified in the form of enamel prisms one for each ameloblast. The enamel is 

 formed first at the apex of the crown of the tooth and extends downward toward 



