In letting of blood three main circumstances are to be considered, "Who, how much, when." That is, that it be done to such a one as may endure it, or to whom it may belong, that he be of a competent age, not too young, nor too old, overweak, fat, or lean, sore laboured, but to such as have need, are full of bad blood, noxious humours, and may be eased by it.
The quantity depends upon the party's habit of body, as he is strong or weak, full or empty, may spare more or less.
In the morning is the fittest time: some doubt whether it be best fasting, or full, whether the moon's motion or aspect of planets be to be observed; some affirm, some deny, some grant in acute, but not in chronic diseases, whether before or after physic. 'Tis Heurnius' aphorism a phlebotomia auspicandum esse curiationem, non a pharmacia, you must begin with bloodletting and not physic; some except this peculiar malady. But what do I? Horatius Augenius, a physician of Padua, hath lately writ 17 books of this subject, Jobertus, &c.
Particular kinds of bloodletting in use are three, first is that opening a vein in the arm with a sharp knife, or in the head, knees, or any other parts, as shall be thought fit.
Cupping-glasses with or without scarification, ocyssime compescunt, saith Fernelius, they work presently, and are applied to several parts, to divert humours, aches, winds, &c.
Horse-leeches are much used in melancholy, applied especially to the haemorrhoids. Horatius Augenius, lib. 10. cap. 10. Platerus de mentis alienat. cap. 3. Altomarus, Piso, and many others, prefer them before any evacuations in this kind.
Cauteries, or searing with hot irons, combustions, borings, lancings, which, because they are terrible, Dropax and Sinapismus are invented by plasters to raise blisters, and eating medicines of pitch, mustard-seed, and the like.
Issues still to be kept open, made as the former, and applied in and to several parts, have their use here on divers occasions, as shall be shown.