PARTS OF ANIMALS, I. i. 



represent the truth or do not. I mean, for instance, 

 should we take each single species severally by turn 

 (such as Man, or Lion, or Ox, or whatever it may 

 be), and define what we have to say about it, in and 

 by itself ; or should we first establish as our basis the 

 attributes that are common to all of them because 

 of some common character which they possess ? — there 

 being many attributes which are identical though 

 they occur in many groups which differ among them- 

 selves, e.g. sleep, respiration, growth, decay, death, 

 together ^^^th those other remaining affections and 

 conditions which are of a similar kind. I raise this, 

 for at present discussion of these matters is an obscure 

 business, lacking any definite scheme. However, 

 thus much is plain, that even if we discuss them 

 species by species, we shall be giving the same de- 

 scriptions many times over for many different animals, 

 since every one of the attributes I mentioned occurs 

 in horses and dogs and human beings alike. Thus, 

 if our description proceeds by taking the attributes 

 for every species, we shall be obliged to describe the 

 same ones many times over, namely, those Avhich 

 although they occur in different species of animals are 

 themselves identical and present no difference what- 

 ever. \^ery likely, too, there are other attributes, 

 which, though they come under the same general 

 head, exhibit specific differences ; — for example, the 

 locomotion of animals : of which there are plainly 

 more species than one — e.g. flight, swimming, walk- 

 ing, creeping. 



Therefore we must make up our minds about 

 the method of our investigation and decide whether 

 we will consider first what the whole group has in 



55 



