"Not only does a liquid become thick which is made of water and earthy matter, but also one made of water and spirits; even as foam thickens and whitens; and the smaller and less conspicuous the bubbles are, the whiter and stiffer does the mass appear. Oil, too, is affected in the same way; for it becomes thick when mixed with spirits, so that, as it whitens, it thickens; what is watery within it being separated by the heat, and becoming spirits.... For the reasons aforesaid the semen, too, is stiff and white as it issues from within, since it contains much hot spirits due to the interior heat. But after the exit of the semen, when its heat has exhaled and its air has cooled, it liquefies and darkens. For in drying semen, as in phlegm, the water remains and perhaps some little earthy matter. The semen then is a combination of spirits and water, the spirits being hot air; so the semen, being derived from water, is naturally liquid.... The cause of the whiteness of the semen is that the generative medium (ἡ γονή) is foam, and that foam is white.... It seems not to have escaped even the ancients that the nature of semen is foamy; at all events they named from this property (δυνάμεως) the goddess who rules coition." (Aristotle: On the Generation of Animals, 735_b_, 8-16; 735_b_, 32 to 736_a_, 2; 736_a_, 13-14 and _a_, 18-21.) A very ancient poem, ascribed to Hesiod, relates the myth of Aphrodite and says that she was so called by gods and men "because she was produced in foam." (Theogony, l. 197-198.) The "air" ἀήρ o f one of the foregoing passages from Aristotle is of course not atmospheric air, but something aëriform produced by heat, as the context shows. In the same treatise he speaks of the presence, within the early embryo which has never breathed, of spirits (πνεῦμα) due to heat and moisture, "the one active, the other passive." (On the Generation of Animals, 741_b_, 37 to 742_a_, 16.) [321] The Latin translation quoted by Harvey renders the Greek words "ὀυδὲ φαίνεται συνιστάμενον πυρουμένοις ὀύτ' [ἐν] ὑγροῖς ὀύτ ἐν ξηροῖς ὀυθέν" (737a, 1-3) by the misleading words "_neque constitui quidquam densis vel humidis vel siccis videntur_." Therefore, in translating this passage into English, it has seemed necessary to make it intelligible by giving to the word "πυρουμένοις" its proper meaning, rather than by rendering literally the earlier translator's ill-chosen Latin word "_densis_." [322] The Latin quoted by Harvey, viz.: "_qui semine continetur_," scarcely gives the force of the original Greek "ἡ διὰ τοῦ σπέρματος" (737_a_, 3-4), which Greek words, rather than the Latin, are rendered in the present English translation.