The four humors were black bile, red or yellow bile, blood and phlegm. The ancients believed that these substances ruled our personalities as well as our bodies. They divided all the possible character types into these four — melancholic, choleric, sanguine and phlegmatic — depending on which substance dominated that particular person.

Treatments for disease were designed to restore the balance among the humors, but what worked for one person might not work for another, which helped let practitioners off the hook if a "cure" didn't work. Purges like enemas and emetics were popular, and physicians often advised changes to a patient's diet or routine. Blood-letting was an especially durable cure for just about anything.

During labor, for example, "some women were bled to unconsciousness to counter delivery pains" or any other complications large or small, according to Peter Conrad's The Sociology of Health and Illness.

The acceptance of the germ theory finally put an end to humoral theory in mainstream medical thought.

Until then, a donor had to be on-site at the time of a blood transfusion.

Bernard Fantus

Dr. Fantus also coined the term "blood bank," in an article in the Journal of the American Medical Association that year that set out the hospital's methodology in clear, understandable terms.

Other institutions swiftly developed their own blood-storage facilities, and helped themselves to Fantus's catchy term as well.

Cook County's blood-storage innovation came at a critical time, just a few years before the start of World War II, when blood donated by people thousands of miles from the battlefronts would make the difference between life and death for a great many injured Allied soldiers.

Even early in the 20th century, a few minutes into any transfusion, blood would begin to clump together in the tube that was carrying it from donor to recipient, and the technician would have to start over. Letting blood sit in a container for any length of time was out of the question.

Richard Lewisohn

A number of researchers were working on the problem. The Belgian physician Albert Hustin, and the Argentinian doctor Luis Agote, both hit on the anticoagulant properties of sodium citrate in 1914, but the bad news was that the common compound was toxic in blood.

Dr. Richard Lewisohn of New York's Mount Sinai Hospital solved that problem with exhaustive experiments.  The German-born Lewisohn, who had trained at the excellent University of Freiburg, discovered the concentration at which sodium citrate could keep blood liquid without poisoning the transfusion recipient.

At first, it looked as if sodium citrate had a worrisome set of side effects, but Lewisohn proved that those were caused by infectious agents in poorly cleaned equipment. In the end, he showed that a diluted sodium citrate concentrate in blood, deployed with meticuously maintained needles and tubes, worked just about perfectly. In fact, it is still used.

Once the medical profession accepted Lewisohn's elegant solution to the clotting conundrum — and that took years — blood transfusions were transformed from a traumatic undertaking to the routine procedure they are today.

In 1916, just in time for World War I, researchers determined that sodium citrate allowed blood to be stored outside the body for up to two weeks.

That began to solve the mystery of why some people who received blood transfusions were fine, while others became ill and often died.

Landsteiner subsequently discovered three of the four genetically determined blood groups or types, O, A and B. A couple of years later, Alfred von Decastello and Adriano Sturli, Landsteiner's colleagues in Vienna, identified a fourth blood group, AB. While about 30 blood types have been discovered, the original four essentially cover everyone.

In 1910, at the Heidelberg Institute for Experimental Cancer Research in Germany, Ludwig Hirszfeld and Emil von Dungern demonstrated that blood type is an inherited trait.

In the speech he made when he accepted the Nobel Prize in 1930 for his work, Landsteiner described the mystery blood presented, and how he and his fellow researchers unraveled its secrets.

In 1922, Landsteiner moved to the Rockefeller Institute of Medical Research in New York, where he discovered an extremely powerful blood antigen he called "the Rh factor."

Today, hospital personnel make sure they know a mother's blood type in case she needs a transfusion. She will also be tested for her Rh factor because it can pose a danger to her baby's well being.

His book, Blood: The Epic History of Medicine and Commerce, and the PBS documentary series it inspired, Red Gold, cover the waterfront on this vital component of life, and our relationship to it.

The PBS website has a great discussion guide that sums up the topic impressively, and includes a timeline of important developments in our evolving relationship with blood.

Even before we understood its function, humans invested blood with value and meaning. As Starr writes in an essay in the guide:

Blood: It’s strange that this most familiar of substances has always been so laden with feeling, so heavily freighted with mystery and symbolism. Consider the vocabulary: blood of our fathers; blood of Christ; the nation’s blood; lifeblood; blood brothers, blood sacrament, blood libel.…The history of blood involves not only medicine, but also culture and religion. It is a story of change — how a mysterious liquid became a global commodity and reflected the soul of each society that used it.

The men were all members of the Experimental Philosophy Club in Oxford, England, and admirers of the work of Francis Bacon, who advocated first-hand investigations into the natural world, rather than accepting long-held orthodoxies.

At the time, it was thought that the blood was impervious to anything that came from the outside world. Using a prototypical syringe made of a quill and a bladder, Wren and Boyle injected dogs with opium and other drugs, and showed that the dogs were affected — that they reacted to the opium, for example, by falling asleep.

These experiments inflamed the scientific community, and no end of creatures were injected with every kind of fluid, from urine to milk, sometimes with fatal results.

Richard Lower, an Oxford-trained doctor and protege of Wren and Boyle's, in 1665 decided to see what happened when he injected a dog with blood from another dog, connecting the two vein-to-vein. The experiment failed. The blood just pooled up in the connecting tube, Douglas Starr relates in his book, Blood: An Epic History of Medicine and Commerce.

Then, Lower tried tapping an artery in the donor dog, and this time the experiment worked. The stronger pressure from the arterial blood made for a successful transfusion, leading Lower to reason that "one Animal may live with the blood of another," Starr writes. Lower's experiments set off a frenzy for transfusions in England and, soon, in France.

Jean-Baptiste Denis, one of the French King Louis XIV's doctors, thought he might cure violent people of their rages by transfusing them with the blood of gentle animals like calves and sheep. At the time, people believed that blood contained a sterotypical set of characteristics of the creature that possessed it. For a while, it looked like Denis had had a stroke of genius, as one violent character in particular seemed for awhile utterly transformed.

Lower was furious, accusing Denis of stealing his work. Meanwhile, some human transfusion subjects began to die (blood being much more complicated than these men understood), including some high-profile patients of Denis. The French Parliament banned transfusions in 1670, followed by the British Parliament and eventually the pope.

That was the end of transfusions in Europe until the early 19th century.

Still, Starr writes, these early researchers "cracked the wall of humoral medicine, showing that the body was ruled not by vague humors but by chemicals, vessels and pumps."

Aeons ago, life on earth consisted of single cells suspended in the primordial sea. They took their nourishment directly from the surrounding waters, and excreted their waste products to be carried away, automatically, by the currents.

As more complicated animals evolved, the sea became private and internal in the form of blood, but it retained the original salts and the chemically useful pH, or acid-alkaline balance, of roughly neutral. When the first creatures slithered onto land, they took that inner sea with them.

The balances have changed slightly in the millions of years since then, but the individual cells of the human body are as dependent on the blood’s constancy as the first cells were on the never-changing sea.

From Shock-Trauma (1980), by Jon  Franklin and Alan Doelp

How much blood we have depends on how big we are — blood accounts for about 8 percent of body weight, on average about five quarts (roughly five liters). More than half of blood is plasma, a yellowish fluid that itself is mostly water.

Plasma carries all the things the cells need when it begins its journey out from the heart. The bulk of its cargo is the 25 trillion red blood cells filled with oxygen, but it also carries infection-fighting white blood cells and platelets that will clot the blood when needed, as well as vitamins, electrolytes, hormones and other materials.

Animals that use a protein called hemoglobin to store oxygen have bright red blood when it's fully oxygenated, because hemoglobin contains iron. (Spider blood, for example, contains copper-rich hemocyanin, and is blue when oxygenated.)

Red blood cells are manufactured in bone marrow, and circulate in the blood for about four months. They look like fat plates, flat but curved, a shape that allows them to squeeze into capillaries. They have no nucleus, devoting as much space as they can to hemoglobin.

One entire circulation of the blood through the body of the average resting adult, given that five quarts of blood, takes about one minute. Without the life-giving oxygen it carries, the most vulnerable cells, including those in the brain, would begin to die within about five minutes, and organs would start shutting down just a few minutes later.

Image from Wikimedia Commons

The human heart

The heart is at the center of the circulatory system, a hollow organ composed of muscle and connective tissue. In humans, the heart has four chambers — two atria or "entrances," and two ventricles or "bellies" — and weighs less than a pound.

The heart beats optimally about 70 times a minute throughout our lives, beginning within three weeks after conception, for a total of about 3 billion pulses in a lifetime of  80 years.

The heart pumps blood to the lungs, where it picks up its cargo of oxygen, and then on to the rest of the body.  Valves in the heart and the blood vessels ensure that blood travels in one direction only, away from the heart in the arteries, and toward the heart in the veins.

Red blood cells travel single-file through the capillaries, the fine vessels that connect the arteries and the veins, to deliver oxygen and other nutrients to the cells. Here the blood takes on waste, especially carbon dioxide, which it will deposit in the lungs for expulsion into the air.

A septum in the middle of heart keeps waste-filled blood returning from its journey through the body separate from oxygenated blood fresh the lungs.

Here in the heart, over and over, the journey begins again.

Image from http://commons.wikimedia.org

The final classic symptom of amniotic fluid embolism is disseminated intravascular coagulation (DIC). When I suffered an AFE during the birth of my younger daughter, I was nothing but classic.

I hemorrhaged to the point where all the blood ran out of my body three times over. I didn't die from this event because I received a total of 87 units of blood and blood products — whole blood, plasma, cryoprecipitate and extra clotting factor.

I am alive to tell our birth story because thoughtful strangers had donated their blood, a large stockpile of blood was five minutes away when I needed it, and because a whole raft of people had done the work over centuries to figure out how to make someone else's blood work in my body.

And, by 1997, the blood supply had been made safe again, after a horrific tainting with the HIV/AIDS virus.

The bill for my daughter's birth, including two surgeries (a Caesarean section and separate hysterectomy performed to stop the bleeding), a stint for the baby in the high-risk nursery, a night for me in the intensive-care unit and an additional four days in the hospital, was $100,000 all those years ago.

Blood accounted for $13,000, more than 10 percent of the total.

Blood was a major factor in giving our birth story a happy ending. Fascinating!