iii. I. 57 



BOOK III. 



(Ch. I J We have next to consider the teeth, and with these 

 the mouth, that is the cavity which they enclose and form. The 

 teeth have one invariable office, namely the reduction of the food ; 

 but besides this general function they have other special ones, 

 and these differ in different groups. Thus in some animals the 

 teeth serve as weapons ; but this with a distinction. For there 

 are offensive weapons and there are defensive weapons ; and while 

 in some animals, as the wild carnivora, the teeth answer both 

 purposes, in many others, both wild and domesticated, they serve 

 only for defence.^ In man the teeth are admirably constructed 

 for their general function, the front ones being sharp, so as to cut 

 the food into bits, and the hinder ones broad and flat, so as to 

 grind it to a pulp ; while between these and separating them 

 are^^he dog-teeth, which, in accordance with the rule that the 

 mean partakes of both extremes, share in the characters of those 

 on either side, being broad in one part but sharp in another.^ 

 Similar distinctions of shape are presented by the teeth of other 

 animals, with the exception of those whose teeth are one and 

 all of the sharp kind. In man, however, the number and the 

 character of the teeth have been mainly determined by the require- 

 ments of speech. For the front teeth of man contribute in many 

 ways to the formation of letter-sounds. 



In some animals, however, the teeth, as already said, serve 

 merely for the reduction of food. When, besides this, they serve 

 as offensive and defensive weapons, they may either be formed 

 into tusks, as for instance is the case in swine, or may be sharp- 

 pointed and interlock with those of the opposite jaw, in which 

 661b. 



