Peter Niebyl, who has traced the rationale for bloodletting from the time of Hippocrates to the seventeenth century, concluded that bloodletting was practiced more to remove excess good blood rather than to eliminate inherently bad blood or foreign matter. Generally, venesection was regarded as an equivalent to a reduction of food, since according to ancient physiological theory, food was converted to blood.[9]
Figure 1.—Chart of elements, seasons, and humors.
Galen defined the criteria for bloodletting in terms of extent, intensity, and severity of the disease, whether the disease was “incipient,” “present,” or “prospective,” and on the maturity and strength of the patient.[10] Only a skilled physician would thus know when it was proper to bleed a patient. Venesection could be extremely dangerous if not correctly administered, but in the hands of a good physician, venesection was regarded by Galen as a more accurate treatment than drugs. While one could measure with great accuracy the dosages of such drugs as emetics, diuretics, and purgatives, Galen argued that their action on the body was directed by chance and could not easily be observed by the physician.[11] However, the effects of bloodletting were readily observed. One could note the change in the color of the blood removed, the complexion of the patient, and the point at which the patient was about to become unconscious, and know precisely when to stop the bleeding.
Galen discussed in great detail the selection of veins to open and the number of times blood might be withdrawn.[12] In choosing the vein to open, its location in respect to the disease was important. Galen recommended that bleeding be done from a blood vessel on the same side of the body as the disease. For example, he explained that blood from the right elbow be removed to stop a nosebleed from the right nostril.[13] Celsus had argued for withdrawing blood near the site of the disease for “bloodletting draws blood out of the nearest place first, and thereupon blood from more distant parts follows so long as the letting out of blood is continued.”[14]
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 passé.[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]