DIGESTIVE SYSTEM. 163 



teeth, these supporting fibers will be cut off and the 

 gingivus drops down and no longer fills the inter- 

 proximal space. 



In the alveolar portion the principal fibers not 

 only spread out and radiate like a fan, but are in- 

 clined downward from their attachment in the ce- 

 mentum to their anchorage in the bony wall of the 

 alveolus. Some of these fibers are tangential to the 

 cementum and thus support the tooth against a 

 rotary strain. The principal fibers thus perform a 

 physical function and firmly bind the tooth to the 

 adjacent hard and soft tissues. At the alveolar 

 border and at the apex of the root they are so ar- 

 ranged as to support the tooth against lateral 

 strain, while in the rest of the alveolar portion the 

 tangential fibers are particularly numerous and sup- 

 port the tooth against any rotary force which may 

 result from the mastication of food. At the gingivus 

 line the fibers blend with the submucosa and bind 

 the gum closely to the neck of the tooth. At the 

 apex of the root the secondary loose variety becomes 

 continuous with the connective tissue of the tooth 

 pulp. 



The cellular elements of the peridental membrane 

 are the fibroblasts, cementoblasts, osteoblasts, osteo- 

 clasts y and epithelial cells, which have been called the 

 glands of the peridental membrane. All these cells 

 are interposed between the bundles of supporting 

 fibers already described. 



i. The fibroblasts are spindle-shaped connective- 

 tissue cells arranged in radiating rows between the 

 fibers. They are numerous in young teeth and 



