Halloween is upon us. The sweltering summer is slowly waning, the humidity is inching downward, and the first hint of cooler weather is creeping in. Those annoying little creatures (children) have returned to school, football and hockey are underway (finally!), and pumpkins are popping up all around town.So to usher in the spooky season and to get everyone in the mood, we’re going to explore the history of one of our most essential bodily fluids. Join me as we take a bloody journey through time…
Long before human dissection was an accepted practice, the inner workings of the body were a mystery. Can you imagine the perplexity of our ancients as they sustained bloody injuries, yet had no idea what that red fluid was, how it was made, or what purpose it served within the body? It’s no wonder they ascribed spiritual and magical explanations to bodily functions…
Although the Egyptians didn’t understand blood’s basis, they, like many throughout history, thought the secret to curing illness was to bleed the patient. The practice of bloodletting persisted for over four thousand years and was believed to rid the body of impurities. It was also believed to restore balance of the “humors,” the four elements, according to Hippocrates, that made up the body: blood, phlegm (a personal favorite), and black and yellow bile. Our first president’s death was hastened, thanks to this ancient treatment.
It wasn’t until the dissections of Galen almost two thousand years after the Egyptians that we began to understand the body's plumbing (although he worked solely on apes). Galen recognized the fact that arteries and veins carried blood and that the blood circulated via vessels. But he mistakenly believed blood formed in the liver and passed from one side of the heart to the other. Hey, you can’t win 'em all.By the 1500s, scientists and physicians concurred that the heart was involved in circulation (video!), although the exact mechanism still escaped them. Spaniard Michael Servetus refuted Galen’s theory about the flow of blood through the heart and, although he was correct about circulation, he was later burned at the stake for criticizing the Holy Trinity.
In 1628, the British physician William Harvey correctly explained the role of the beating heart in his oh-so-popular text, Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus. A real page-turner…Thirty years later, the up-and-coming Dutchman, Jan Swammerdam, (only twenty-one at the time!) was the first to describe red blood cells. I consider his discovery one of the truly missed nomenclature opportunities in science. Think how much more colorful biology would be if our circulatory system relied on "swammerdams" to oxygenate the body!
By the late 1600s, the concept of blood transfusion was still a work in progress. The first to attempt it was Parisian Jean-Baptiste Denis, and the experiments soon spread to England. Unfortunately, they chose to transfuse their patients with the blood of animals and after multiple failed attempts, the practice was kicked to the curb where it languished for almost 150 years. Finally, by the mid-1800s, docs had worked out the kinks, mainly by sticking to species-specific blood. They found human-to-human worked best, although even transfusions between peeps had problems. Sometimes the blood would clump, and it wasn’t until blood groups were identified that the mystery was finally solved.In 1901, Karl Landsteiner identified three different types of blood: A, B, and O, and received a Nobel Prize for his efforts. A year later, Decastello and Sturli added a fourth type - AB, and the modern era of hematology was underway.
Today, we know an awful lot about blood. It is comprised of several crucial components. Red cells contain a protein called hemoglobin, which binds with oxygen, enabling blood to transport that essential gas throughout the body. White cells fight off infection, platelets form lifesaving clots, and plasma is the fluid in which the other components are suspended. Together, these constituents make up one of the most important fluids in the body.The average adult contains about five liters. Blood is oxygenated in the lungs, pumped out by the heart, and circulated via the arteries. Veins return the oxygen-depleted blood to the heart, where it is then pumped back into the lungs, returned to the heart, and the cycle starts all over again (although within the pulmonary circulation, the roles of the veins and arteries are reversed).
So as Halloween draws near, take a moment to appreciate the blood coursing through your veins. Place your finger against your carotid artery and relish the beautiful beat of your heart, knowing that with every pulse, every throb, that life-sustaining liquid is delivering its fragile cargo to your hungry tissues. I’ll leave you with the lovely words of Georg Büchner:
“The death clock is ticking slowly in our breast, and each drop of blood measures its time...”
Here's a great read on the history of transfusion:
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