“There are differences in the particular actions of medicines, arising from each of them being to a certain degree hot, or cold, or dry, or humid, or consisting of subtile or of gross particles, but the degree in which each of them is possessed of the above-mentioned properties cannot be truly and accurately determined. We have endeavoured, however, to define them in such a manner as will be sufficient for all practical purposes, laying it down that there is one class of medicines possessed of a similar temperament to our bodies, when they have received a certain principle of change and aliation from the heat in them, and that there is another which is of a hotter temperament than we. Of this temperament I have thought it right to make four orders, the first being imperceptible to the senses, and only to be inferred from reflection; the second being perceptible to the senses; the third strongly heating but not burning; and the fourth, or last, caustic. In like manner of frigorific or cooling things, the first order requires reflection to demonstrate its coldness: the second consists of such things as are perceptibly cold; the third is perceptibly cold, but does not occasion mortification; the fourth produces mortification. So it is in like manner with humectating and desiccant articles. Let such an order of degrees be laid down to render clearer the course of instruction, rose oil or the rose itself being placed in the first order of cooling things; the juice of roses in the second, and in the third and fourth those things which are extremely cold, such as cicuta, meconium, mandragora, and hyoscyamus. In regard to hot things, dill and fenugreek belong to the first order; those which are next to them, to the second; and so of the third and fourth, until we come to the caustic. In like manner, respecting moistening and desiccant medicines, beginning with those of a moderate degree, we may arrange them until we come to their extremes. Such knowledge is of no small importance for the purpose of medical instruction. One ought also to exercise the sense of taste, and remember the peculiar qualities of juices; as, for example, that such a substance when applied to the tongue dries strongly, contracts, and roughens it to a considerable depth, such as unripe wild pears, cornels, and the like; every such thing that is intensely austere is called sour. Such things, as when applied to the tongue, do not constringe and contract it like astringents, but, on the contrary, appear to be detergent and cleansing, are called salt. Such things as are more detergent and also rougher in a painful degree, are called bitter. Those things which are biting and corrosive with a strong heat, are called acrid; and such as are biting without heat, are called acid, and these have the power of causing a fermentation when poured upon earth. Of those which lubricate, fill, remove asperities, and, as it were, erosions of the tongue, such as do so with sensible delight, are