GENERATION OF ANIMALS, V. viii. 



speech. But why are the front teeth formed first 

 and the molars afterwards ? And why are the molars 

 not shed, whereas the front teeth are, and ^row 

 again ? We must take it to be appropriate to 

 examine the cause of these things in a treatise on 

 Generation. 



Now Democritus has treated of these matters, but 

 his treatment is not correct, because he assigns a 

 cause to apply generally although he has not under- 

 taken an exhaustive investigation of the facts. He 

 says that the reason why animals shed their teeth is 

 that they are formed prematurely, since it is when 

 animals are in their prime or thereabouts that they 

 grow their teeth according to nature. Suckling is the 

 cause he names for their being formed prematurely. 

 Still, the pig suckles, yet does not shed its teeth " ; 

 and so do all the animals with sharp interfitting 

 teeth,* but some of them (e.g., the lion '^) do not shed 

 any teeth except the canine ones. Democritus, then, 

 made this mistake because he made a general state- 

 ment without investigating the facts in all cases ; 

 but this is precisely what we ought to do, because 

 whenever anyone makes a general statement it must 

 apply to all cases. Now the assumption we make — 

 and it is an assumption founded upon what we observe 

 — is that Nature neither defaults nor does anything 

 idly in respect of the things that are possible in every 

 case ; and further, if an animal is going to get any 

 nourishment after the period of its suckling is over, 

 it must of necessity possess instruments with which 

 to deal with its nourishment. So that if this took 

 place, as Democritus says, about the time of maturity, 

 Nature would be defaulting in one of the things which 

 it is possible for her to do, and we should have Nature 



555 



