HARVEYS PARADOXICAL INFLUENCE: THERAPY BY LEECH AND LANCET

12 May

Harvey’s work opened up new fields of research and ignited violent controversies, but it certainly did not threaten the livelihood of phle- botomists. While provoking new arguments about the selection of ap- propriate sites for venesection, the discovery of the circulation seemed to stimulate interest in bloodletting and other forms of depletion therapy. Not even Harvey seemed to worry about the compatibility, or incompatibility, of therapeutic bloodletting and the concept of a closed, continuous circulation. Indeed, Harvey defended venesection as a major therapeutic tool for the relief of diseases caused by pleth- ora. Long after accepting Harvey’s theory, physicians praised the health-promoting virtues of bloodletting with as much (if not more) enthusiasm as Galen. In addition to prescribing the amount of blood to be taken, doctors had to select the optimum site for bleeding. Long-standing arguments about site selection became ever more creative as knowledge of the circulatory system increased. Many physicians insisted on using distant sites on the side opposite the lesion. Others chose a site close to the source of corruption in order to remove putrid blood and attract good blood for repair of the diseased area. Proper site selection was supposed to determine whether the primary effect of bloodletting would be evacuation (removal of blood), derivation (acceleration of the blood column upstream of the wound), or revulsion (acceleration of the blood column downstream of the wound). Debates about the relative effects of revulsion and derivation are at the heart of Franc¸ois Quesnay’s (1694–1774) physiocratic system, the first so-called scientific approach to economics. (The term physiocracy refers to the idea that society should allow natural economic laws to prevail.) The debate between Quesnay, Professor of Surgery and physician to Louis XV, and the physician Jean Baptiste Silva (1682–1742) began with conflicting ideas about medical issues involved in bloodletting and culminated in rationalizations of social and economic theories. Bleeding was recommended in the treatment of inflammation, fevers, a multitude of disease states, and hemorrhage. Patients too weak for the lancet were candidates for milder methods, such as cupping and leeching. Well into the nineteenth century, no apothecary shop could be considered complete without a bowl of live leeches, ready to do battle with afflictions as varied as epilepsy, hemorrhoids, obesity, tuberculosis, and headaches (for very stubborn headaches leeches were applied inside the nostrils). Enthusiasm for leeching reached its peak during the first half of the nineteenth century. By this time, leeches had to be imported because the medicinal leech, Hirudo medicinalis, had been hunted almost to extinction throughout Western Europe. Franc¸ois Victor Joseph

Bloodletting instruments

Bloodletting  instruments   as  depicted  in  a  1666  text   by  Johann   Schultes (1595–1645).

Broussais (1722–1838), an influential French physician, was the undis- puted champion of medical leeching. Broussais believed that almost all diseases were caused by an inflammation of the digestive tract that could be relieved by leeching. Perhaps the most bizarre use of leeches was the case of a young woman who attempted to commit suicide with the aid of fifty leeches. Leeches live by sucking blood and will generally attach themselves to almost any available animal, be it fish, frog, or human. On the posi- tive side, leeches are excellent fish bait and they probably control the snail population in lakes and ponds. Moreover, unlike snails (the vector of schistosomiasis, also known as bilharzia or snail fever), leeches do not play a significant role as intermediate hosts of human parasites.

The leech became a favorite experimental animal among neurobiologists, who considered its ganglion a thing of beauty. In comparison to other medical procedures, leeching had the virtue of being essentially painless. The amount of blood taken was controlled by prescribing the appropriate number of leeches. In the 1980s, plastic and reconstructive surgeons rediscovered the usefulness leeching; the anticoagulant action of leech saliva improves local blood flow and thus aids healing. Leeches were also used as a means of draining blood clots from donor skin flaps in order to increase adhesion to the recipient site. Leeches simply drop off the skin once they are full of blood. The success of leech therapy created a new era of leechmania as scientists gathered together in 1990 to present papers celebrating the Biomedical Horizons of the Leech. Researchers reported that leeches produce a remarkable array of enzymes, anticoagulants, antibiotics, and anesthetics. More- over, patients, especially children, become fascinated by these living medical instruments. In the not too distant future, the best of the leech products will probably appear as pure and very expensive drugs, synthe- sized by the powerful new techniques of molecular biology and patented by innovative pharmaceutical companies.

For hundreds of years after the death of Galen, physicians warned their patients about the dangers posed by a plethora of blood. If a plethora of blood caused disease, bloodletting was the obvious remedy. Spontaneous hemorrhages and venesection were, therefore, as natural and helpful to the maintenance of life as the menstrual purgation was in healthy women. Bleeding was a perfectly rational means of treatment within this theoretical framework. To explain the persistence of blood- letting, physicians have tried to find modern explanations for the success stories of their predecessors. For example, in patients with congestive heart failure, bleeding might provide some relief because hypervolemia (an excess of blood) is a component of this condition. But well into the nineteenth century, many physicians believed that a ‘‘useless abundance of blood’’ was a principal cause of all disease.

Vigorous therapeutics, including copious bleeding and massive doses of drugs, formed the basis of the so-called heroic school of American medicine, best exemplified by the death of George Washington in 1799. Under the supervision of three distinguished physicians, Washington was bled, purged, and blistered until he died, about 48 hours after complaining of a sore throat. Across the Atlantic, the eminent Edinburgh surgeon John Brown (1810–1882) treated his own sore throat by applying 6 leeches and a mustard plaster to his neck, 12 leeches behind his ears, and, for good measure, removing 16 ounces of blood by venesection. Questioning the validity of bloodletting required a large dose of skepticism and courage. Jan Baptista van Helmont (1579–1644), physician and chemical philosopher, was one of the rare individuals who dared to protest against the ‘‘bloody Moloch’’ presiding over medi- cine. Van Helmont claimed that bloodletting was a dangerous waste of the patient’s vital strength. Not only did he reject bloodletting as a medical treatment, he denied the doctrine that plethora was the cause of disease.

In answer to attacks on his position launched by orthodox physicians, van Helmont proposed putting the question to a clinical test. To demonstrate that bloodletting was not beneficial, van Helmont suggested taking two hundred to five hundred randomly chosen poor people and dividing them into two groups by casting lots. He would cure his allotment of patients without phlebotomy, while his critics could treat the other half with as much bloodletting as they thought appropriate. The number of funerals in each group would be the mea- sure of success, or failure. Such tests of bloodletting were not carried out until the nineteenth century, when the French physician Pierre Charles Alexandre Louis (1787–1872) used his ‘‘numerical system’’—the collection of facts from studies of large numbers of hospitalized patients—to evaluate thera- peutic methods. Louis’s statistical studies of the efficacy of venesection had little impact on the popularity of bloodletting. Critics of the numerical system charged Louis’s followers with excessive zeal in the art of diagnosis, and negligence in treating the sick.

Many doctors believed that Louis’s attempt to evaluate the efficacy of bloodletting was a rash, reckless rejection of the wisdom of the ages. Even admirers of the numerical system were reluctant to modify their therapeutic habits and were skeptical of applying facts obtained in Parisian hospi- tals to other environments. Louis’s studies indicated that bloodletting did not affect the course of pneumonia, a condition in which vene- section was thought to be particularly beneficial. Some physicians argued that Louis’s data actually proved that venesection was ineffec- tive when performed too conservatively. The controversy inspired tests of multiple bleedings in rapid succession in the treatment of endocarditis, polyarthritis, pneumonia, typhoid fever, and other diseases.

Anecdotal evidence of patient survival, not statistical data, was taken as proof of efficacy. Unconvinced by skeptics or statistics, most physicians continued to believe that bleeding was one of the most powerful therapeutic methods in their time-honored and rational system. Only a learned physi- cian could judge whether to bleed from veins or arteries, by leech, lancet, or cupping. Advocates of bloodletting argued that more patients were lost through timidity than through the loss of blood. Two hundred years after Harvey discovered the circulation of the blood, medical authorities were still instructing their students to treat hemorrhage by bleeding to syncope (fainting, or collapse), because venesection encouraged coagulation of the blood and arrested hemorrhage. Some doctors have suggested that bloodletting may have remained so widely used in the treatment of human and animal disease, at least in part, because it was actually effective against a wide spectrum of disorders.

One hypothesis for the therapeutic value of bloodletting is that iron-binding proteins are part of the body’s defense mechanism for coping with infection and neoplasia. Low levels of iron stores seem to correlate with reduced mortality from some infectious diseases, whereas excess iron apparently promotes the growth of certain patho- gens and exacerbates the inflammatory response. Modern medicine recognizes the value of venesection as a way to treat certain iron- overload disorders. Of course, severe iron-deficiency anemia is dan- gerous to health, but it is unclear what the optimum iron levels might be under different physiological conditions and microbial challenges. It is generally assumed that the practice of therapeutic bloodletting became extinct by the end of the nineteenth century, but according to the 1923 edition of Sir William Osler’s Principles and Practice of Medi- cine—the ‘‘Bible’’ of medicine for generations of American doctors— after a period of relative neglect, bleeding was returning to favor in the treatment of cardiac insufficiency and pneumonia.

Indeed, a renais- sance of bloodletting had begun about 1900, particularly for pneu- monia, rheumatic fever, cerebral hemorrhages, arterial aneurysms, and epileptic seizures that were thought to be correlated with men- struation. Bloodletting was said to be effective in relieving pain and dif- ficulty in breathing, and it was important in treating fevers, because it lowered body temperature. Other than doing nothing, which was gener- ally anathema to doctors and patients, the practitioner had few alter- natives to offer a febrile patient. From a practical point of view, bleeding convinced doctor, patient, and family that something important, something supported by hundreds of years of learned medical tradition, was being done. Those who have observed the quiet prevailing among blood donors might also consider the fact that a quiet patient, especially one brought to a state close to fainting, will get more rest and be less of a nuisance to caretakers than a restless, delirious, and demanding one.

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