BOOK III 



The subject which follows naturally after our pre\'ious Teeth- 

 remarks is that of the Teeth. We shall also speak 

 about the Mouth, for this is bounded by the teeth 

 and is really formed by them. 



In the lower animals teeth have one common 

 function, namely, mastication ; but they have addi- 

 tional functions in different groups of animals. In 

 some they are present to serve as weapons, offensive 

 and defensive, for there are animals which have 

 them both for offence and defence (e.g. the wild 

 carnivora) ; others (including many animals both 

 wild and domesticated) have them for purposes of 

 assistance. 



Human teeth too are admirably adapted for the 

 common purpose that all teeth subserve : the front 

 ones are sharp, to bite up the food ; the molars 

 are broad and flat, to grind it small ; and on the 

 border between the two are the dog-teeth whose 

 nature is intermediate between the two : and just as 

 a mean shares the nature of both its extremes, so 

 the dog-teeth are broad in one part and sharp in 

 another. Thus the provision is similar to that of 

 the other animals, except those whose teeth are 

 all sharp ; but in man even these sharp teeth, in 

 respect of character and number, are adapted 

 chiefly for the purposes of speech, since the 



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