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Blood vessels contain blood. That may seem completely obvious to you now, but 3,000 years ago, people thought vessels carried air and maybe even urine.
Everything we know today is the sum of ideas that came before us. There’s a saying that goes, “If we achieve greatness, it is because we stand on the shoulders of giants.” The “giants” of heart medicine were doctors and scientists who worked over the past 10,000 years to unlock this organ’s mysteries. Some of their ideas were silly or wrong, but their discoveries made modern medicine possible.
▲ Sumerians (about 5000 B.C.) believed the liver created blood and that the heart was the center of thought.
▲ Imhotep (about 2700–2670 B.C.) was an Egyptian pyramid engineer, astronomer, and more. As a doctor, he learned that blood circulates and that the heart pumps it in pulses.
▲ Early doctors couldn’t just open a dead body and peek inside to study the heart, because dissecting humans was forbidden. A Greek named Alcmaeon of Croton (about 500 B.C.) was the first person to do it anyway, as far as we know. He figured out that the brain was where thinking happened (not the heart, as had been thought). He also saw that blood vessels came in two kinds: veins and arteries.
▲ Herophilus was a doctor in ancient Greece (about 300 B.C.). Many Greeks thought that air flowed through blood vessels (the word artery means “air carrier”). Herophilus corrected that mistake, but the “air carrier” theory lingered among some scholars.
▲ Galen (about A.D. 130–199) was a doctor for great Roman emperors. Other doctors used his two books on medicine to train for 1,400 years, which is too bad, because the books were full of errors. For one thing, Galen saw the heart as an oven for keeping blood warm. He thought blood flowed from one half of the heart to the other through tiny holes. He also wrote that the body made blood directly out of the food you ate.
▲ Sick people have bad blood, so just get rid of the bad blood, and the sick will get well. That’s what many people thought, up to the nineteenth century. Many doctors thought bloodletting was a great cure. They would cut open a patient’s vein or use leeches, slimy creatures that attach to skin and suck out the “bad blood.” Of course, these “treatments” just made people sicker—or killed them.
Check It Out!
Pretend you’re an ancient doctor and you have to explain how the body functions, just by looking at the outside of it. For example, why does a bruise go from black and blue to yellow and green before it returns to normal again? Can you come up with a reason?
We bruise when blood vessels just beneath the skin are broken. The blood starts out red, but it doesn’t stay that way for long, because it loses its oxygen and turns dark purple (or “black and blue”). Little by little, the body breaks down the loose blood. It gets rid of hemoglobin (red coloring matter), which makes the bruise turn from purple to yellow or green. When all of the blood has been broken down, the bruise disappears.
▲ Leonardo da Vinci (1452–1519)—scientist, artist, and inventor—drew the first accurate diagrams of the heart. He dissected (took apart) dead bodies to do it.
▲ Andreas Vesalius (1514–1564) first learned the position of organs from inaccurate textbook diagrams such as this one. He later put these mistaken pictures and most of Galen’s faulty medicine to rest. He published a new, more accurate anatomy text.
▲ William Harvey (1578–1657) learned how the circulatory system really works. For starters, blood does not come from food. Arteries pass blood to the veins in the outer parts of the body, and veins carry blood toward the heart. (In other words, the circulatory system is circular.) Harvey’s discoveries were huge steps forward for all medicine, not just heart science. He took the field out of the Dark Ages and ushered in the modern era of heart science.
Try This!
Next time you have chicken or turkey for dinner, ask an adult to help you dissect the chicken or turkey heart (if it’s included). Rinse the heart and set it on a plate. Look for the yellow globs of fat. Does the muscle feel tough or soft, and how many tubes go in and out of the heart? Compare the heart to the liver. The heart has mechanical, or moving, parts, and if you slice it in half you’ll see the chambers, tubes, and valves. Rinse the liver and slice it in half, and you’ll see that it looks the same all over. When you’re done, throw out the organs and wash your hands with soap and hot water.
