But since they are unequally desiccative—for in this consists their asperity—they are likewise terrene; for every watery substance permeates the body evenly, and when removed it easily coalesces; but what is terrene when removed does not readily coalesce again. And the peculiarity of the sensation, if you will recollect the impression, will testify to the same effect; for the passage of acid juices, in the organs of sensation, appears quick; but that of sour, slow; and acids exert their actions more on the deep-seated parts, whereas sour substances act more superficially. When you wish to ascertain the action of a truly sour substance, if that which is made trial of appear at the same time sour and pungent, I would recommend you to lay that species aside, and to have recourse to something which is sour without being pungent, and neither acid, sweet, nor bitter, but as much as possible having no one quality or power mixed up with its astringency; for it is useless and foolish to make trial of such a medicine, as it cannot be ascertained whether it be by its astringency, or by any of the qualities mixed with it, or by a combination of both, that the substance which is made trial of exerts its action. Therefore, chalcitis, misy, copperas, the flakes of copper, sori, and, in addition to them, the armeniacum pictorium (Armenian pigment), mercury, and other astringent substances which are also at the same time pungent, act by both their properties upon the bodies to which they are applied; but we are not thereby informed whether they burn by their astringency or by their acrimony; for such substances, when taken into the body, being composed of gross particles, and rather hot in their powers, having become ignited in the course of time, according to the change which they undergo in the body of the animal, ulcerate and burn the parts about the stomach like heated stones or irons; and owing to their weight they are incapable of being distributed over the body. It is better, therefore, after much observation, to look out for something that is purely astringent, and when you have found such a substance, make haste to try it in the manner you have formerly heard described; such as having tasted the flowers of the wild pomegranate, galls, or the flowers of the cultivated pomegranate, hypocistis, acacia, sumach, or the like, if the substance appear intensely sour, and it is manifest that it contains no other quality, you must prove the action of astringency from it. A sour substance then is terrene and cold, and its quality may necessarily be removed in three ways; either by being heated, or moistened, or by undergoing both these changes at the same time. If only heated, it will neither become more humid nor softer; but becoming harder it will have acquired sweetness, as is the case with acorns and chesnuts, as they are called. But if only moistened, and if the humidity is of a thick nature and watery, it becomes austere; for