GENERATION OF ANIMALS, II. ii. 



Later, when it has lost its heat by evaporation 

 and the air has cooled, it becomes fluid and dark, 

 because the water and whatever tiny quantity of 

 earthy matter it may contain stay behind in the 

 semen as it soUdifies, just as happens ^^•ith phlegma.^ 

 Semen, then, is a compound of pneuma and water 

 (pneuma being hot air), and that is why it is fluid in 

 its nature ; it is made of water. Ktesias of Knidos ^ 

 is obviously mistaken in his statement about the 

 semen of elephants : he says that it gets so hard 

 when it sohdifies that it becomes Uke amber. It does 

 not. It is, of course, true that one semen must of 

 necessity be earthier than another, and the earthiest 

 v^ill be in those animals which, for their bodily bulk, 

 contain a large amount of earthy matter ; but semen 

 is thick and white because there is pneuma mixed with 

 it. WTiat is more, it is white in all cases. Herodotus '^ 

 is incorrect when he says that the semen of Ethiopians 

 is black, as though everything about a person with a 

 black skin were bound to be black — and this too in 

 spite of their teeth being white, as he could see for 

 himself. The cause of the whiteness of semen is that 

 it is foam,<* and foam is white, the whitest being that 



Apollonia ; see Vindicianus, § 1 (Diets, Vorsokr.^ 64 B 6) 

 Alexander Amator veri ( = $tAaAijffijs) . . . libro primo De 

 semine spumam sanguinis eius essentiam dixit Diogenis 

 placitis consentiens : and cf. § 3. See Jaeger's discussion 

 of the subject in l>iokles von Karystos, 198-:311. Cf. also 

 Hippocrates, it. yovfji ktX. 1 (vii. -tvO Littre) d-noKpiveTai airo rod 

 vypov a<f>pf.6vTos to laxvporarov. In modern times a similar 

 idea has been put forward, e.g., by Butschli (UnterKnrhnngen 

 iiber mtkroskopi.<sche Schiiume vnd das Protoplasma, Leipzig, 

 1893), who " thought of protoplasm as a foam, or rather as 

 an emulsion composed of two liquids, one in the form of drop- 

 lets, the other as lamellae [i.e., films) between the droplets " 

 (Heilbrunn, An Outline of General Physiology, 1938, p. 25). 



163 



