TEETH OF QUADRAMANA. ^ 133 



the Rat, the 3Iarmot, and the Porcupine, present 

 examples of this structure, among the omnivorous 

 rodentia : and the Hare, the Rabbit, and the Squirrel, 

 among those which are principally herbivorous. 



The Quadrumana, or Monkey tribes, approach 

 nearest to the human structure in the conformation 

 of their teeth, which appear formed for a mixed 

 kind of food ; but are especially adapted to the 

 consumption of the more esculent fruits. The other 

 orders of Mammalia exhibit intermediate grada- 

 tions in the structure of their teeth to those above 

 described, corresponding to greater varieties in the 

 nature of their food. Thus the teeth and jaws 

 of the HycBua are formed more especially for break- 

 ing down bones, and in so doing exert prodigious 

 force ; and those of the Sea Otter have rounded 

 eminences, which peculiarly fit them for breaking 

 sheels. 



The teeth, though composed of the same che- 

 mical ingredients as the ordinary bones, differ from 

 them by having a greater density and compactness 

 of texture ; whence they derive that extraordinary 

 degree of hardness which they require for the 

 performance of their peculiar office. The sub- 

 stances of which they are composed are of three 

 different kinds; the first, which is the basis of the 

 rest, constituting the solid nucleus of the tooth, has 

 been considered as the part most analogous in its 

 nature to bone ; but from its much greater density, 

 and from some peculiarities in the mode of its for- 

 mation, the name of ivory has been generally given 

 to it.* Its earthy ingredient consists almost en- 



* It has also been termed dentine. Owen's Odontography, p. 9. 



