GENERATION OF ANIMALS, IV. ii. 



the animals face north or south while they are 

 copulating <* : such a small thing thrown in on one 

 side or the other (so they say) acts as the cause of 

 heat and cold, and these in turn act as the cause 

 of generation. 



Male and female, then, differ generally with regard importance 

 to each other in respect of the generation of male and ^^^e-pia. 

 female offspring on account of the causes which have 

 been stated. At the same time, they must stand in 

 a right proportional relationship to one another,^ 

 since everj^thing that is formed either by art or by 

 nature exists in virtue of some due proportion. Now 

 if " the hot " is too powerful it dries up fluid things ; 

 if it is very deficient it fails to make them " set " ; 

 what it must have in relation to the object which 

 is being fashioned, is the mean proportional, and 

 unless it has that, the case will be the same as what 

 happens when you are cooking : if there is too much 

 fire it burns up your meat, if there is too little it \\ill 

 not cook it — either way what you are trying to pro- 

 duce fails to reach completion. The same applies to 

 the mixture of the male and the female : they require 

 the right proportional relationship, and that is the 

 reason why it happens that many couples fail to effect 

 generation with one another, but if they change 

 partners they succeed ; and also that these opposi- 

 tions occur sometimes in young people, sometimes 

 among those who are older, both with regard to 

 failure and success in generation and also vriih regard 

 to the generation of male and female offspring. 

 •^ Also, one country differs from another in these Effect of 

 respects, and one water from another, on account of '^^""^*^^- 

 the same causes, for the quality of the nourishment 

 especially and of the bodily condition of a person 



399 



