CHAPTER X 

 THE ATTACHMENT OF TEETH 



WHILE the general study of the attachment of teeth may 

 be better considered in works on dental anatomy, the 

 microscopic structure of the teeth and bone and their con- 

 necting tissues concerned in the different modes of attach- 

 ment render it necessary to dwell somewhat on the different 

 methods by which the union of the teeth with the jaws is 

 brought about. 



Our knowledge of the forms of attachment, especially in 

 fish, is chiefly due to C. S. Tomes, who was the first to 

 describe the existence of a special bone of attachment in 

 reptiles and fish. 



The various modes of attachment of teeth may be classified 

 as follows : 



1. Fibrous attachment. 



2. Attachment by an elastic hinge. 



3. Anchylosis. 



4. Socketing or gomphosis. 



(1) Attachment by Fibrous Membrane. This form is seen 

 in the Sharks and Rays. 



The class Plagiostomi, to which these forms belong, is 

 characterized by a cartilaginous skeleton. The teeth of the 

 Sharks have no direct attachment to the jaw, but are 

 attached to the mucous membrane by strong fibrous bands 

 which envelop the spurs or processes at the base of the 

 tooth and firmly bind it down to the tough fibrous mem- 

 brane covering the jaws. A sliding movement of this fibrous 

 mucous membrane takes place over the jaws as the teeth 

 come into use, the membrane with its attached rows of 

 teeth rolling, as it were, over the rounded margin of the jaw 

 and thus bringing the functional rows of teeth successively 

 into an upright position. As the movement progresses the 

 teeth of the front row are cast off, or shed, and the next row 

 of teeth take their place. 



That this forward movement of the whole fibrous mem- 



