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CHAP. I. What a Medicine is, and how it differeth from nourishment.
WEE define a medicine to bee, That which hath power to change the bo∣dy according to one or more qualities; and that such as cannot bee changed into our nature: contrary whereto we terme that nourishment which may be converted into the substance of our bodies. But we define them by the word power, because they have not an absolute nature, but as by relation and depending upon the condition of the bodies by whom they are taken. For that which is medicine to one, is meat to another, and that which is meat to this, is medicine to that. Thus for example, Hellebore is nourishment to the Quaile, but a medicine to man: Hemlocke is nourishment to a Sterling, but poison to a Goose: the Ferula is food to an Asse, but poison to other cattell. Now this di∣versity is to be attributed to the different natures of creatures.
It is recorded in history, that the same by long use may happen in men. They re∣port that a maide was presented to Alexander the great, who, nourished with Napel∣lus, and other poisons, had by long use made them familiar to her, so that the very breath she breathed was deadly to the by-standers. Therefore it ought to seeme no marvaile, if it at any time happen, that medicines turne into the nature and nourish∣ment of our bodies: for we commonly may see birds and swine feed upon serpents and toads without any harme: and lastly,