52 ii. i6. 



distinctly formed nostrils, nothing in fact which can be called 

 nostrils except from a functional point of view. A bird at any. 

 rate has nothing which can properly be called a nose. For its 

 so-called beak is a substitute for jaws. The reason for this 

 is to be found in the natural conformation of birds. For they 

 are winged bipeds ; and this makes it necessary that their head 

 and neck shall be of light weight ; just as it makes it necessary 

 that their breast-bone shall be narrowed. The beak therefore 

 with which they are provided is formed of a bone-like substance, 

 in order that it may serve as a weapon as well as for nutritive 

 purposes, but is made of narrow dimensions to suit the small 

 size of the head. In this beak are placed the olfactory passages. 

 But there are no nostrils ; for such could not possibly be placed 

 there. 



As for those animals that have no respiration,^ it has already 

 been explained why it is that they are without nostrils, and 

 perceive odours either through gills, or through a blow-hole,^ 

 or, if they are insects, by the hypozoma ; ^^ and how their power 

 of smelling depends, like their motions, upon the innate spirit '^ 

 of their bodies, which in all of them is implanted by nature 

 and not introduced from without. 



Under the nostrils are the lips, in such sanguineous animals, 

 that is, as have teeth. For in birds, as already has been said, 

 the purposes of nutrition and defence are fulfilled by a bone- 

 like beak, which forms a compound substitute for teeth and lips. 

 For supposing that one were to cut off a man's lips, unite his 

 upper teeth together, and similarly his under ones, and then 

 were to lengthen out the two separate pieces thus formed, flat- 

 tening them on either side and making them project forwards, 

 supposing I say this to be done, we should at once have a bird- 

 like beak. 



The use of the lips in all animals except man is to preserve 

 and guard the teeth ; and thus it is that the distinctness with 

 which the lips are formed is in direct proportion to the degree 

 of nicety and perfection with which the teeth are fashioned. In 

 man the lips are soft and flesh-like and capable of separating 

 from each other. Their purpose, as in other animals, is to guard 

 the teeth, but they are more especially intended to serve a higher 

 office, contributing in common with other parts to man's faculty 

 of speech. For just as nature has made man's tongue unlike 

 650 b. 



