Blood Basics: Test Your Human Body IQ

Blood is a specialized body fluid with four main ingredients. Plasma is the liquid part. It makes up a little over half of our blood. It's 92% water. The rest of our blood is made of red and white blood cells and platelets. Dr. Re-Write Explanation

When founding father George Washington came down with a sore throat and had trouble breathing, his doctors took blood from his body. This was a common way to treat ills in those days. In all, they drained about five pints -- about half of his blood -- in less than a day. The president didn't recover.

When a Japanese matchmaker asks, "What's your type?" she may not mean tall, dark, and handsome, but A, B, O, or AB. Many Japanese believe your blood group says a lot about your personality. Type A blood is a sign you are hard-working, neat, and sensitive. People with type O are thought to be independent, logical self-starters.

Blood tests are used to tell if you are sick. Too few red blood cells may mean you have anemia. Too many white ones can be a sign of infection. Blood tests can help diagnose many other illnesses. Doctors also use blood tests to be sure that a medical illness is not causing the symptoms of depression or another mental illness. Now, researchers are suggesting that certain chemicals in the blood may be signs or "markers" that a person may be depressed or even thinking about suicide. These results give hope for better ways to test for, treat, and prevent mental illness.

A theory called "geographic progression" shows that if vampires had been around in the year 1600, as rumored, there wouldn't have been enough blood to go around. As legend goes, vampires don't just "vantto suck your blood," they needit. Every time they kill to stay alive, it's minus one for humans, plus one for vampires. At that rate, we would have been wiped out in less than 3 years, leaving vampires bloodthirsty.

Spending long stretches of time without moving your legs can cause "deep-vein thrombosis," or blood clots in the legs. Flights of 8 hours or longer are the worst. To lower your risk, stand, stretch, and walk a bit when the seat belt sign isn't lit. Go for roomier exit rows if you have a choice.

A study shows people with the rarest blood type, AB, are most likely to have thinking and memory problems. If you have type AB blood, you may want to forget about this finding in favor of doing things that can help keep your memory sharp, such as controlling blood pressure, cholesterol, and blood sugar.

A British doctor named William Harvey first discovered the circulation of blood in 1628. Thirty-seven years later, the first known transfusion was done by physician Richard Lower. He treated a sick dog by giving him blood from other dogs. The first human blood transfusion was done by Frenchman Jean Baptiste Denis 2 years later.

Actually, it's quite the opposite. In Middle Eastern culture, blood brothers -- warriors who share blood they shed in battle -- are even closer than biological brothers. An earlier expression is that blood is "far stronger than the water of the womb." Historians think wealthy Englishmen may have bent the meaning to stress the importance of bloodlines and keep money in the family.