To let blood by the incision of a vein is not new: but to practise this in almost every distemper is new. Again, to bleed younger people, and women, that are not pregnant, is of ancient use. But to attempt the same in children and old people, and in pregnant women, is not an old practice. For indeed the ancients judged, that the first and last stages of life were not able to bear this kind of remedy; and they were persuaded, that a pregnant woman, who had been thus treated, would miscarry. But afterwards experience proved, that none of these rules were universal, and that some other circumstances were rather to be regarded, by which the intention of the physician was to be directed. For the material point is not, what the age may be, or what is contained within the body, but what degree of strength there is. Upon this account if a young man is valetudinary, or a woman not with child be weak, bleeding is bad: for the remaining strength, is by this evacuation destroyed. Whereas to a stout boy, and a robust old man, and a strong pregnant woman, it may be used with safety. ’Tis true an unskilful physician may be greatly deceived in such patients: because there is commonly less strength at these times of life. And a pregnant woman stands in need of strength after her cure, to support not only herself, but her fœtus also. But whatever requires either attention of mind, or prudence, is not to be immediately rejected: since the excellency of the art here consists, not in numbering the years, nor in regarding conception alone, but in considering the strength, and collecting from thence, whether there will be left sufficient to support either a boy, or an old man, or two bodies at once in one woman. There is a difference also between bodies strong, and corpulent: and those, that are slender, and infirm. In the slender, blood more abounds, but in those of a fuller habit, flesh. Wherefore the first bear this evacuation more easily: and he, that is over fat, is soonest distressed by it. For this reason the strength of the body is to be estimated rather by the state of the vessels, than from its appearance.