You get cut. You bleed.
That’s about as much as ancient Sumerians knew about blood. Sumerians lived around 5000 B.C., long before microscopes and modern medicine. Most of what they knew (or thought they knew) came from observing the outer body.
About 3000 B.C., an Egyptian genius named Imhotep made a big breakthrough. He realized that blood moves. He also figured out that the heart is the organ that makes blood move. It’s a simple idea, but it took scientists another 5,000 years before they could explain the circulatory system in detail. Today’s scientists are still questing for answers about blood.
