GENERATION OF ANIMALS, II. vi. 



an excellent device to suit the case, in making the 

 failure of the teeth coincide ^^ith the time of old age 

 and the close of life. If life went on for 10,000 or 

 even 1000 years, the teeth would have had to be quite 

 enormous to begin with, and they would have had to 

 grow afresh many times over ; not even continuous 

 growth would have sufficed to prevent them being 

 ground do'svn and becoming useless for their work. 

 We have now described the purpose for the sake of 

 jvhich the teeth grow. And yet as a matter of fact 

 the teeth do not possess the same nature as the rest 

 of the bones, because the bones, without exception, 

 are all formed during the first stage of the embryo's 

 construction, whereas the teeth are formed later ; 

 and that, too, is why a fresh set of teeth is able to 

 grow after the old ones have fallen out : although 

 they are in touch with the bones, they are not all of 

 a piece ^vith them. Still, they are formed out of the 

 nourishment which is distributed to the bones (which 

 is why they possess the same nature), and at a time 

 when the bones have already attained their full 

 complement. All the animals except man already 

 have their teeth (or the counterpart of teeth) when 

 they are born — unless it be that something unnatural 

 occurs — because when they are released from their 

 process of formation they are more fully perfected 

 than man ; man however when born has no teeth — 

 unless something unnatural occurs. We shall explain 

 later on '^ why some of the teeth are formed and fall 

 out and why some do not fall out. 



The reason why man's body is more naked than 

 that of any single one of the other animals, and why 

 he has the smallest nails in proportion to his size, is 

 this. Parts of this sort * are made of residue ; now 



237 



