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Guess what? Blood vessels contain blood. That may seem obvious now, but 3,000 years ago, people thought vessels carried air or even urine.
Everything we know was built on ideas that came before us. There’s a saying: “If we achieve greatness, it is because we stand on the shoulders of giants.” The “giants” of heart medicine are doctors and scientists who worked at different times over the past 10,000 years. 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. They wrote that the heart, not the brain, was the center of thought.
▲ Imhotep (about 2700–2670 B.C.) was an Egyptian pyramid engineer. He was also an astronomer and did other things. 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 to study the heart, because dissecting humans was forbidden. Even so, a Greek named Alcmaeon of Croton (about 500 B.C.) was the first known person to do it anyway. He figured out that the brain, not the heart, did the thinking. 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 believed that air flowed through blood vessels. The word artery means “air carrier.” Herophilus set most people straight, though the “air carrier” theory stuck around for a while longer.
▲ Galen (about A.D. 130–199) was a doctor for great Roman emperors. For 1,400 years, other doctors used his two books on medicine to train. Too bad the books were mostly wrong. 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 they’ll get well. That’s what many people thought, up to the nineteenth century. Many doctors thought bloodletting was a great cure. They’d cut open a patient’s vein or use leeches. Leeches are slimy creatures that attach to skin and suck out the “bad blood.” Of course, “treatments” like these just made people sicker—if they didn’t kill them.
Check It Out!
Pretend you’re an ancient doctor. Looking at the outside of your body, can you explain how things work? For example, why does bruised skin go from black and blue to yellow and green and then to normal again?
A bruise means blood vessels just under the skin are broken. The blood is red, but it doesn’t stay that way for long. It loses its oxygen and turns dark purple (or “black and blue”). Slowly, the body breaks down the loose blood. It gets rid of hemoglobin (red coloring matter), and that turns the bruise from purple to yellow or green. When all the blood has been broken down, the bruise goes away.
▲ Leonardo da Vinci (1452–1519 was a scientist, artist, and inventor. He took apart dead bodies to see how they worked and drew the first accurate diagrams of the heart.
▲ Andreas Vesalius (1514–1564) learned the position of organs from inaccurate diagrams like this one. He later corrected them and most of Galen’s wrong ideas. Then Vesalius published a new, more accurate anatomy book.
▲ William Harvey (1578–1657) learned how the circulatory system really works: Blood does not come from food. Arteries pass blood to the veins in the outer parts of the body. Veins carry blood toward the heart. In other words, the circulatory system is circular. Harvey’s discoveries are among the biggest advances in all medicine, not just heart medicine. Before his work, heart science was in the Dark Ages, but he led the way toward modern heart science.
Try This!
Next time you have chicken or turkey for dinner, ask an adult to help you dissect the bird’s heart (if it’s included). Rinse the heart and set it on a plate. Look for the yellow globs. That’s fat. Does the muscle feel tough or soft, and how many tubes go in and out of it? Now 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. But if you rinse the liver and slice it in half, it looks the same all over. When you’re done, throw out the organs and wash your hands with soap and hot water.
