206 



A MANUAL OF DENTAL ANATOMY. 



injuring the hinge, the tooth will stay in any position into 



which it is put. 



FIG. 88 1 . 



The points most noteworthy are, (i.) that hinged teeth have 

 arisen independently in three families of fish widely removed 

 from one another, and (ii.) that, whilst the general object of 

 mobility and elastic resiliency is attained in all, it is by a 

 different mechanism, and by the least modification possible 

 of the existing fixed teeth of the family. 



( 1 ) Hinged tooth of Pike. a. Dentine. 5. Elastic rods, formed of un- 

 calcified trabeculae which might have become bone. c. Hinge, not itself 

 elastic, d. Bone of attachment, e. Bone of body of jaw. 



