It is often referred to as the river of life. The biological tie that binds-or divides-with equanimity.

The story of blood, and our beliefs about it, flows through the veins of human history: Mystery. Mythology. Morality. Even in our time, blood presents us with a paradox-it can save lives or hold the seeds of their destruction. A blessing or a biohazard. With World Health Day 2000 calling attention to the adequacy and safety of the blood supply, it is a good time to reflect on the conflicts about the nature of blood, a debate nearly as ancient as humanity itself.

Historians tell us, for example, that Mayan rulers anointed altars with their own blood as a royal intervention for the continuation of the cosmos. Bishop Diego de Landa, 16th century colonial missionary, wrote of the bloodletting rites of the Mayas of the Yucatan peninsula in Relación de las cosas de Yucatán: "They make sacrifices of their own blood, sometimes cutting the edges [of their ears] in pieces, and thus they left them as a sign [of their devotion]. Other times they pierced their cheeks, other times the lower lips; again they scarify parts of the body; or again they perforate their tongues in a slanting direction from side to side, passing pieces of straw through the holes, with horrible suffering; … they always anointed the face of the demon [their idols] with the blood of these."

In ancient Rome, the blood of warriors held the general population in thrall. Spectators vied to drink the blood of fallen gladiators as a cure for maladies as far-ranging as epilepsy-or even cowardice.

Bloodletting

The practice of venesection, or surgical bleeding, was performed throughout the world for thousands of years. The ancient Chinese were a notable exception: they pricked and punctured their patients to elicit energy, not blood. It was a curious paradox, then, for medical practitioners of virtually every other civilization to have no doubt that purposeful bleeding was beneficial, even as they understood that hemorrhaging definitely was not.

The oldest-known written account about the application of leeches was written by a Greek in the Late Hellenistic period, Nicander, who died in Alexandria around 135 B.C. He described blood-sucking worms being applied to places on the body containing excess blood, where they remained until they fell off, gorged. Over a millennium earlier, the tomb of the scribe Userhat, of Egypt's 18th Dynasty (1567-1308 B.C.) was embellished with a wall painting depicting a medical expert applying a leech to a patient.

The advanced Inca civilization was also no stranger to bloodletting. "They considered bleeding and purges to be beneficial," wrote "El Inca" Garcilaso de la Vega, son of a Spanish conquistador and an Incan princess. "They bled both arms and legs, not from the vein that was most likely to be effective in the case of this or that illness, but from the one that seemed to them to be nearest the point of the patient's suffering. When they had a headache, they bled their foreheads, at the spot where the eyebrows meet. Their lancet was made of a silex blade, fastened in the fork of a small, split stick, the tip of which they placed over the vein, then struck the other end of the stick with a flick of the finger." Published in 1608, Garcilaso's Royal Commentaries provided the last glimpse of the legendary Inca civilization.

Meanwhile, bloodletting had grown into a meticulous pseudo-science during the Renaissance in Western Europe. Phlebotomy tables illustrated the relationship of every part of the human body to the signs of the zodiac. Bloodletting was permissible only at specific times for specific parts of the body. In treating patients, many doctors hoarded "cheat sheets" to keep the stars in proper anatomical alignment.

Yet despite centuries of evidence that intentional bleeding rarely did any patient any good, physicians continued the practice until the beginning of the 20th century, even in the United States, where country doctors might recommend a seasonal bleed to maintain good health.

The Renaissance and Transfusions

During the late 1500s in the Italian city of Padua, Galileo's lectures on mathematics were wildly popular with medical students, inspiring one-William Harvey-to apply the master's laws of motion and mechanics to the mystery of how blood circulated through the body. The puzzle was solved with the development of tools for measuring the amount of blood moving through the arteries, thus revealing the function of the heart.

This new concept of circulation led members of the European medical community to envision the possibility of treating disease internally, using the bloodstream as a carrier for therapy, including not only drugs, but transfused blood, as well. Richard Lower, a physiologist and successful practitioner in Cornwall, England, began a series of experiments transfusing blood from one dog to another. His initial efforts-in which he connected the slit jugular vein of both animals with a reed-failed. Eventually, however, Lower succeeded, once he began transfusing the more gentle-flowing vein in the recipient with blood spurting strongly (literally pumping) from the donor's artery. His discovery would be-come the basis for transfusion protocol that continued for centuries.

The mastery of animal-to-animal transfusions (mixing the blood of lambs, oxen, and dogs) paved the way for attempts at human transfusion (with animal's blood) on both sides of the English Channel. On 15 June 1667, Dr. Jean-Baptiste Denis transfused eight ounces of lamb's blood into a feverish young man who had been bled repeatedly by his own doctors. The boy recovered, encouraging Denis to con-tinue his human experiments; in one infamous case, he transfused a patient on two separate occasions with calf's blood, unaware that the heat and symptoms of shock exhibited by the patient were due to the incompatibility of animal and human blood. (Animal blood contains proteins that are attacked by antibodies in the human blood, thereby destroying the incoming red cells and oxidizing the resulting toxic hemoglobin.)

Back across the Channel, 12 ounces of sheep's blood were injected into the bloodstream of Arthur Coga, a clergyman, on 23 Novem-ber 1667. Samuel Pepys, the British diarist and bon vivant, met the patient in a tavern a week later. "[Although] he speaks well," Pepys observed, perhaps another transfusion was necessary, as Coga still appeared "crack'd a little in the head. . . ."

As the human experiments continued in England and France, politics and professional jealousy seized upon every setback, engendering protests on moral as well as scientific grounds. Backed by a trio of Denis's rivals, the wife of a deceased patient sued the doctor for malpractice. Although he was exonerated, the French Parliament banned all transfusions involving human beings, as did the English shortly thereafter. When two men died from transfusions in Rome, the Pope banned the practice through- out Europe, as well.

Some 150 years after the Pope's decree, in 1818, London obstetrician James Blundell attempted a human-to-human transfusion. The patient died. But Blundell, unable to squelch his horror at the high mortality rate suffered by birthing mothers due to hemorrhages, persisted in finding a remedy. Out of 10 attempted transfusions over the next 11 years, five patients survived. While these results from such a small sample would be deemed wholly inadequate by today's standards, they were sufficient to encourage Blundell and others to reconsider the possibilities of human blood transfusion. Making a clinical case for blood transfusions progressed at a snail's pace. William Halsted, a U.S. surgeon renowned for his then-radical advocacy of sterile surgical conditions, spurred progress in 1881 when he performed an emergency transfusion of his own blood to his sister after she suffered a massive postpartum hemorrhage. It revived her almost immediately.

Over the next few years, Halsted pioneered the emergency treatment of hemorrhage by intravenous infusion of salt solution, an extraordinarily effective technique to stave bleeding that inexplicably was ignored and forgotten for almost a hundred years.

This creeping advancement in treatment did nothing, however, to shed light on the complexities of blood itself. The crimson fluid remained an enigma to the scien-tific and medical communities, an elixir with a structural code that had to be cracked before the next advances in medicine could be made.

Blood Groups and Other Breakthroughs

Blood surrendered one of its most vital secrets in 1901, when a methodical Viennese pathologist, Karl Landsteiner, discovered the human ABO blood group system. Landsteiner con-cluded that normal human blood existed in several varieties, each of which was perceived as foreign by the others; hence, the need for transfusion from a donor whose blood bore the same type as the recipient. However, it took several years for blood typing to become standard procedure. In 1930, Landsteiner was awarded the Nobel Prize for Physiology or Medicine. (Working with Alex Wiener, Philip Levine, and R. E. Stetson, he went on to discover the Rh blood group in 1940.)

With the technical means for blood transfusion becoming more scientifically accurate, attention turned to collecting blood in much larger quantities. The first blood bank was established in a Leningrad hospital in 1932. Five years later, the first hospital laboratory to preserve and store donor blood was created in the United States at the Cook County Hospital in Chicago, Illinois. Within the next few years, hospital and community blood banks began to appear in major cities across North America.

The timing was propitious. World War II introduced a new medical challenge: massive civilian casualties. In Great Britain alone, the Luftwaffe's blitzkrieg killed 60,000 and left nearly a quarter million more injured. Nationwide blood transfusion services were created and, by necessity, blood donation centers were set up to stockpile blood and plasma. This availability of a comparatively copious amount of supplies was a significant boost to medical progress far beyond the war years. And with a greater demand came a closer look at what a donor's bloodstream contained and how these elements might render the blood usable, or harmful.

Safe Blood

The idea of "safe" blood has been part of the blood donation schematic for only a few decades. Safe blood is defined as that containing no viruses, parasites, recreational drugs, alcohol, chemical substances, or other extraneous factors that might cause danger or disease to the recipient. Today, there are nine tests to detect infectious diseases in donated blood; all should be conducted on each unit. Tests for hepatitis B and syphilis were in place before 1985. Since then, tests for HIV, human T-lymphotrophic virus, and the hepatitis C virus have been added.

The transmission by transfusion of infectious diseases, such as malaria, leishmaniasis, babesiosis, and Chagas' disease, has diminished greatly over the years in countries utilizing a multi-tiered blood donor screening system that includes questioning of donors, donor deferral, and sound testing procedures.

Still, less than 30 percent of the world's public health systems are able to provide a safe and adequate blood supply. In the Western Hemi-sphere, fewer than half of the 35 member countries of the Pan Ame-rican Health Organization (PAHO), the World Health Organization's Regional Office for the Americas, report screening 100 percent of all blood samples for hepatitis B and C and HIV. According to a recent PAHO report, "annually, around 50,000 units are transfused that have not been screened for HIV and HBV (hepatitis B virus), and around 1,500,000 that have not been screened for HCV (hepatitis C virus)."

Recent advancements in medical technology have created the latest source of blood donors: newborns. Cord blood-blood left in the baby's umbilical cord after the cord has been cut-is rich in stem cells, the building blocks of blood and the immune system, and can be banked by families as a safeguard against possible future illness. The blood is collected immediately following the baby's delivery and frozen for storage, making the stem cells available to family members for the treatment of a variety of cancers and blood diseases, if the need arises.

Garcilaso de la Vega might not have thought this such a great step forward. At the dawn of the 17th century, he wrote, "When a child was born, the umbilical cord was not cut close to the belly, but a piece about as long as one's finger was left hanging. Then when this little gut became detached, it was carefully preserved and given to the child to suck, in case of some illness."

Today, in many Western Hemisphere countries, voluntary blood donation is as much a matter of personal pride as it is civic responsibility. Yet while the International Red Cross suggests that a country can maintain its optimum blood supply with only 5 percent of the population donating, no country in the Americas currently meets that goal.

World Health Day 2000 focuses on a safe and adequate blood supply for the new millennium. In a statement at the 7 April launch of PAHO's regional blood safety initiative, the Organization's Direc-tor, Dr. George A. O. Alleyne said: "Our objectives in the international observance of World Health Day are to increase the awareness of safe blood issues in the Americas and to encourage voluntary donations of blood, thorough testing and screening of donated blood, and appropriate use of blood for transfusions."

Noting that "the risk of transfusion-transmitted infections is higher when blood products come from paid or replacement donors, rather than volunteer and repeat donors," he said: "We must meet the challenge of promoting voluntary blood donation through mass communication and improving the care of potential donors in blood banks. We want people in the countries to understand and accept blood donation as a desirable, altruistic act, and health workers to discourage replacement donation and retain and educate volunteer donors. People who want to donate blood should be able to do it in comfortable, clean, attractive facilities."

The ministers of health of the Americas have adopted the goal of ensuring that all blood for transfusions is screened against infection by hepatitis B and C, syphilis, Trypanosoma cruzi (the parasite that causes Chagas disease), and HIV. They have resolved to give higher priority in their national health policies to the safety of blood for transfusion and to promote the development of national blood programs and transfusion services, based on the voluntary, repeated donation of blood and on quality assurance.

"Our goal for World Health Day, and for every day," Alleyne said, "is to intensify efforts to have more volunteers donate blood and reduce the numbers of replacement donors and paid donors. We cannot limit the observance to only one day: blood is needed every day, so we must ensure the safety of blood and blood products, and raise awareness of the need for systematic blood screening. There is no reason for anyone in the Americas to contract a disease transmitted by blood transfusion if we all do our part."

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Wendy Wilson is a Washington, D.C.-based freelance writer specializing in documentaries in the fields of history, science, health, and nature.