GENERATION OF ANIMALS, II. iii. 



semen is a residue of the nourishment that is under- 

 going change." It remains, then, that Reason alone 

 enters in, as an additional factor, from outside, and 

 that it alone is divine, because physical activity has 

 nothing whatever to do with the activity of Reason.* 

 Now so far as we can see, the faculty of Soul of 

 every kind has to do with some physical substance 

 which is different from the so-called " elements " and 

 more divine than they are ; and as the varieties of 

 Soul differ from one another in the scale of value, so 

 do the various substances concerned with them differ 

 in their nature. In all cases the semen contains 

 within itself that which causes it to be fertile — what 

 is known as " hot " substance,*^ which is not fire nor 

 any similar substance, but the pneuma which is en- 

 closed within the semen or foam-like stuff,'* and the 

 natural substance which is in the pneuma ; and this 

 substance is analogous to the element which belongs 

 to the stars.® That is why fire does not generate 

 any animal,^ and we find no animal taking shape either 

 in fluid or solid substances while they are under the 

 influence of fire ; whereas the heat of the sun ' does 

 effect generation, and so does the heat of animals, 



ible, and divine (269 a 31 flF., 270 a \2 fF., 270 b 10 ff.)- Aris- 

 totle claims that it was va^ely recognized by the ancients, as 

 is suggested by the name (aither) they gave to " the upper- 

 most place " (270 b 16 if.) : d-rro rov 9eiv del tov dlSiov ■)(p6vov 

 Be/xevoi T^v iirojwfjiiav avTu>. {Cf. Hippocrates, tt. aapKcov 2 

 (viii. 584 Littre) SoKeei 8e pot o KaX4oy.ev depfiov, dOdvaTov re 

 ttvai . . . rovTO ovv . . . i^e\(Lpnqo€v els Trjv dvarraTOj irepi- 

 t^prfv Kal avTO /xot So/cc'ct aldepa toIs TroAatois elpfjadax.) Its 

 motion is circular ; so is that of the stars, which are com- 

 posed of it (289 a 15). It is not found in the sublunary 

 regions, but pneuma is its " counterpart " (see Introd. §§ 70 if., 

 App. A §§ 7 if., and B). ' But see 761 b 15 flF., and note. 

 » See App. A §§ 7 ff., B §§ 7-17. 



171 



