308 MICROSCOPIC ANATOMY OF THE TEETH 



between and among the fibrous elements of the membrane, 

 and the osteoblasts, probably derived from them, are in 

 contact with the bone and the cement. Calcified bodies are 

 often found in the peripdontal membrane, the so-called 

 ' epithelial pearls ', which appear to be due to calcification 

 in the cell nests or epithelial remnants (fig. 200). 



Large multinucleated cells, the osteoclasts, are often 

 seen in the situation where absorption of the cement is 

 in progress. Under the influence of these different cells, 



FIG. 200. A so-called epithelial pearl in the periodontal 

 membrane, c. Cement ; d. dentine. ( x 150.) 



absorption and re-deposition of cement is often seen to be 

 taking place at the surface of the tissue as above described. 

 The periodontal membrane is derived from the connec- 

 tive tissue of the capsule, which, as described in the chapter 

 on development, extends around the dentine papilla ; the 

 connective-tissue fibres which it contains penetrate the 

 cement which is deposited around them, and they thus 

 become involved in the calcified tissue, as are the penetrating 

 fibres of Sharpey in bone, with which they are strictly 

 analogous. As in bone, it is doubtful if they are fully calcified, 

 and the occurrence of caries in the cement where the micro- 



