Controversy over the location of the veins to be opened erupted in the sixteenth century. Many publications appeared arguing the positive and negative aspects of bleeding from a vein on the same side (derivative--from the Latin _derivatio_ from the verb _derivare_, "to draw away," "to divert") or the opposite side (revulsion--from the Latin _revulsio_, "drawing in a contrary direction") of the disordered part of the body. This debate mirrored a broader struggle over whether to practice medicine on principles growing out of medieval medical views or out of classical Greek doctrines that had recently been revived and brought into prominence. The medieval practice was based on the Moslem medical writers who emphasized revulsion (bleeding from a site located as far from the ailment as possible).[15] This position was attacked in 1514 by Pierre Brissot (1478-1522), a Paris physician, who stressed the importance of bleeding near the locus of the disease (derivative bleeding). He was declared a medical heretic by the Paris Faculty of Medicine and derivative bleeding was forbidden by an act of the French parliament. In 1518, Brissot was exiled to Spain and Portugal. In 1539, the celebrated anatomist, Andreas Vesalius, continued the controversy with his famous _Venesection Letter_, which came to the support of Brissot.[16] Only with the gradual awareness of the implications of the circulation of the blood (discovered in 1628) did discussion of the distinction between derivative and revulsive bloodletting become passe.[17] Long after the circulation of the blood was established, surgical treatises such as those of Lorenz Heister (1719) recommended removing blood from specific parts of the body--such as particular veins in the arm, hand, foot, forehead, temples, inner corners of the eye, neck, and under the tongue. In the nineteenth century this practice was still challenged in the literature as a meaningless procedure.[18] (Figure 2.) _How Much Blood to Take_ According to Galen, safety dictated that the first bloodletting be kept to a minimum, if possible. Second, third, or further bleedings could be taken if the condition and the patient's progress seemed to indicate they would be of value. The amount of blood to be taken at one time varied widely.[19] Galen appears to have been the first to note the amount of blood that could be withdrawn: the greatest quantity he mentions is one pound and a half and the smallest is seven ounces. Avicenna (980-1037) believed that ordinarily there were 25 pounds of blood in a man and that a man could bleed at the nose 20 pounds and not die.[20]