DIGESTIVE SYSTEM. 159 



the dentinal tubules, and extending through the 

 tubule to the outer surface of the dentin, where they 

 completely fill the granular spaces already described 

 as the granular layer of Tomes. It is generally 

 believed that these processes may transmit im- 

 pressions to the sensory nerves of the pulp. (2) 

 Each odontoblast shows lateral processes, minute 

 but blunt, that interlock with like processes from 

 adjacent cells. (3) Usually a single process pro- 

 jects from the basal end into the pulp. 



The odontoblasts are dentin-forming cells and 

 superintend the formation and calcification of 

 primary and secondary dentin. 



2. The layer of Weil represents a layer of connec- 

 tive-tissue cells forming a thin zone just beneath the 

 odontoblasts. In thin sections this appears as a 

 thin layer about half as thick as that of the odonto- 

 blasts. 



3. Underneath the layer of Weil the connective- 

 tissue cells are numerous and closely packed. To- 

 ward the center of the pulp they become loosely but 

 uniformly scattered. The cells are small, have a 

 single deep-staining nucleus, and the cytoplasm 

 stretching out into slender processes in many direc- 

 tions, forming stellate cells ; or in two directions to 

 form spindle cells. 



The connective-tissue fibrils of the pulp are similar 

 to those of white fibrous connective tissue, sometimes 

 resembling the reticular variety. The vascular con- 

 dition of the pulp makes it an organ of nourishment 

 for the dentin as well as the mature tooth. 



Cementum. The cementum covers the dentin in 



