GEXERATIOX OF ANIMALS, IV. ii. 



which are in their prime ; the reason being that in 

 the young their heat is not yet perfected, in the older, 

 it is faihng. Also, parents which are more fluid of 

 body and feminine tend to produce females : this is 

 true also of fluid semen as opposed to that which has 

 " set " : all these things are due to a deficiency of 

 natural heat. 



Also, the fact that when the wind is in the north " 

 male offspring tend to be engendered rather than 

 when it is in the south (is due to the same cause : 

 animals' bodies are more fluid ^ when the wind is in 

 the south) so that they are more abundant in residue 

 as well. And the more residue there is, the more 

 difficulty they have in concocting it ; hence the 

 semen of the males and the menstrual discharge of 

 the women is more fluid. 



Also, the fact that the menstrual discharge in the 

 natural course tends to take place when the moon 

 is waning '^ is due to the same cause. That time of 

 month is colder and more fluid on account of the 

 waning and failure of the moon (since the- moon 

 makes a summer and \\inter in the course of a month 

 just as the sun does in the course of the whole year. 

 [This is not due to its turning at the tropics ; no, 

 the one occurs when the moon's light is increasing, 

 the other when it is waning.'*]). Also, shepherds 

 say that it makes a difference so far as the gen- 

 eration of males and females is concerned not 

 only whether copulation occurs when the wind 

 is in the north or in the south, but also whether 



that whereas summer and winter result from the " turnings " 

 of the sun, viz., the solstices, the " summer " and " winter " 

 of the moon are not due to the moon's " turnings," but to its 

 waxings and wanings, which are completely independent of 

 its " turnings." 



