GENERATION OF ANIMALS, IV. x. 



Still, this is not the reason for it ; only, this is what 

 in fact normally occurs. The larger and more per- 

 fect of the blooded animals do certainly live a long 

 time, but not all the larger ones are also longer-lived. 

 Man is the longest-lived of them all except the 

 elephant, so far as we have any rehable experience ; 

 but human beings are smaller than the lophouroi " and 

 many others. The reason why any animal is long- 

 lived really is that its " blend " is about the same in 

 comparison with the air which is around it,* and 

 there are other contributory factors inherent in its 

 nature, which Mill be mentioned later on.*^ The 

 reason for the various times of gestation is the size 

 of the creatures which are generated. It is not 

 easy for any large structure, be it an animal or 

 anything else, almost, to reach its perfection in a 

 short time. Hence horses and kindred animals, 

 though they live a shorter time than men, have 

 a longer time of gestation : in horses birth occurs 

 at the end of a year, in the others, generally, after 

 ten months. And for the same reason it takes a 

 long time in elephants, whose gestation lasts two 

 years owing to their excessive size. 



•* In all cases, as we should expect, the times of Periods of 

 gestation and formation * and of lifespan aim. ac- gov^il^ 

 cording to nature/ at being measured by " periods." by cosmic 

 By a " period '" I mean day and night and month and ^*" *' 



** The following important paragraph is not fully intel- 

 ligible \*'ithout reference to Aristotle's theory of the universe 

 and of movement. A collection of pa,ssages from other 

 treatises relevant to this will be found in App. A and App. B 

 § 11, which will provide the best commentary on the present 

 passage. ' Or " birth." 



' But Nature cannot always succeed in her aim ; see 

 (78 a 5 below. 



477 



