Yet neither Hippocrates nor any of the other physicians or philosophers whom I mentioned a short while ago thought it right to omit this; they say that when the heat which exists naturally in every animal is well blended and moderately moist it generates blood; for this reason they also say that the blood is a _virtually_ warm and moist humour, and similarly also that yellow bile is warm and dry, even though for the most part it appears moist. (For in them the _apparently_ dry would seem to differ from the _virtually_ dry.) Who does not know that brine and sea-water preserve meat and keep it uncorrupted,[277] whilst all other water--the drinkable kind--readily spoils and rots it? And who does not know that when yellow bile is contained in large quantity in the stomach, we are troubled with an unquenchable thirst, and that when we vomit this up, we at once become much freer from thirst than if we had drunk very large quantities of fluid? Therefore this humour has been very properly termed warm, and also virtually dry. And, similarly, _phlegm_ has been called cold and moist; for about this also clear proofs have been given by Hippocrates and the other Ancients. Prodicus[278] also, when in his book "On the Nature of Man" he gives the name "phlegm" (from the verb [Greek: pephlechthai]) to that element in the humours which has been burned or, as it were, over-roasted, while using a different terminology, still keeps to the fact just as the others do; this man's innovations in nomenclature have also been amply done justice to by Plato.[279] Thus, the white-coloured substance which everyone else calls _phlegm_, and which Prodicus calls _blenna_ [mucus],[280] is the well-known cold, moist humour which collects mostly in old people and in those who have been chilled[281] in some way, and not even a lunatic could say that this was anything else than cold and moist. If, then, there is a warm and moist humour, and another which is warm and dry, and yet another which is moist and cold, is there none which is virtually _cold and dry_? Is the fourth combination of temperaments, which exists in all other things, non-existent in the humours alone? No; the _black bile_ is such a humour. This, according to intelligent physicians and philosophers, tends to be in excess, as regards seasons, mainly in the fall of the year, and, as regards ages, mainly after the prime of life. And, similarly, also they say that there are cold and dry modes of life, regions, constitutions, and diseases. Nature, they suppose, is not defective in this single combination like the three other combinations, it extends everywhere.