things; for sour things seem to propel inwards the part which they touch, everywhere equally squeezing, constricting, and contracting, as it were; but the austere seem to penetrate deeply, and to induce a rough and unequable sensation, so that by drying they expel the humidity of the parts of sensation. Thus, between sour and austere juices, there is a certain peculiar difference of sensation not easily to be described, but which everybody must understand from what has been said. Every sour substance, then, when free from all other qualities, I have upon trial always found to be cold; but every sweet substance is hot, and does not greatly exceed the heat in us; and as we are delighted, more especially if we are cold, with the touch of warm water, until it expand the parts congealed by the cold, and as it heats us, and does not dissolve nor break the continuity of the parts, it is very pleasant and useful; so all sweet food is hot, and yet it is not possessed of such a degree of heat as to be unpleasant, but remains within the limits of those things which expand, soften, and are demulcent: for all nutritive food is allied to, and agrees with, the whole substance of the bodies which it nourishes; it requires, therefore, to be moderately hot, so as to agree with the bodies which are nourished; and hence one kind of food and medicine does not agree with all men; for according to his peculiar substance and affection is every one delighted and benefited. And such being the nature of things those kinds of food which are less sweet are less hot, and their heat is proportionate to their sweetness; but these things, when they get to an immoderate degree of heat, are no longer sweet, but appear bitter, such as honey which is old and much boiled, and so also with all other sweet things; for such things as without boiling or preparation are allied to the temperaments of the bodies which they nourish, appear already sweet; but all such as are not allied appear unsavoury until prepared, for those which are hot require to be corrected by cold, and those which are sufficiently cold by the mixture of calefacient food and by heat. In like manner such things as are terrene and drier than proper, are to be corrected by humidity; and those things which are humid and watery, by drying; that which is sweet therefore, in addition to being more or less hot, is necessarily more or less humid. But when this bitterness arises from being over-roasted, as in lime and ashes, it is necessarily rendered dry and hot. For this reason every bitter thing is of such a nature as to prove detergent, and is calculated to break down and to cut viscid and thick humours, and such are ashes and natron; but that bitter sap is dry and terrene, may be collected from the circumstance, that bitter things are of all others the least prone to putrefaction, and do not engender worms nor other animals such as are usually formed in roots,