Subtitles section Play video Print subtitles Blood. It's pretty simple, right? It's the red junk that comes out when you fall down. It's what vampires eat when they're feeling like Count Snackula. It's one of about five bodily fluids that can change the MPAA rating of a movie. Running low? Head to your local hospital and have them top you off. Okay, so that's not actually how blood works and before you go in for a transfusion, there's a whole lot of science to be done, because even the slightest mistake in this relatively routine procedure can lead to a violent, horrifying death. We know this, because we got to where we are today with a lot of trial and error by doctors and unfortunate patients in the past. The history of transfusion, according to the American Red Cross, actually goes all the way back to the 17th century, with British physician William Harvey first describing blood circulation in 1628. By 1665, another Englishman by the name of Richard Lower was managing to keep dogs alive via infusions of fresh blood, and a year later, a fellow named Jean Baptiste Denis conducted the first human blood transfusion. And then things went off the rails. Lower experimented with giving people transfusions of sheep's blood. When Denis tried it, though, the patient died, and in 1670, France banned blood transfusions a ban that would remain in place for more than two centuries. In the 1800's, though, doctors in England began using blood transfusions again, and by the 1870's doctors in America were injecting people with milk yes, milk as a replacement for blood. Within a few years, though, they replaced milk with saline, which was a lot better, but still not as good as, you know, actual blood. That all sounds crazy now, but thanks in part to those experiments, Austrian physician Karl Landsteiner discovered the first three blood groups A, B, and O in 1901. In 1907, American professor Ludvig Hektoen suggested that matching blood types might increase the odds of transfusion recipients surviving longer, and the first matched transfusion was performed later that year. Matching blood types was a pretty enormous win for the medical community, and there's a good reason we've never doubled back on the practice. Passing the wrong brand of blood between patients is, as it turns out, about as healthy as jamming 2% into their arteries like they did 150 years ago. Here are the bare bones basics, as presented by the helpful folks at the Australian Academy of Science: everybody has a blood type, which indicates what sorts of antibodies are in their blood. Antibodies are special proteins that work as your body's pit bosses, identifying problem customers like bacteria and viruses that make it into the works. A person with type A blood possesses antibodies which target specific antigens, a person with type B blood has a different set of antibodies. If these antibodies notice something that doesn't look right, they go on the attack lickety split including any foreign blood cells that show up with the wrong set of antigens attached, which is why getting the wrong type blood is a really big problem. "If hemolysis occurs in the blood or the serum, her red blood cells will explode. She will die." Yes, that's right: explode! See, when this happens, donor blood is rejected by the body in a pretty dramatic way. The recipient's immune system will attack the outsider blood, exploding the proteins in the foreign blood and sending the remains into the kidneys to be separated from the rest of the gang. And the human kidney, while remarkable, isn't set up to handle the sudden rush of dead blood cells that occurs when a large transfusion goes wrong. Worst case scenario, they'll shut down entirely. With that in mind, there's almost always a blood shortage at your local hospital, with rare blood types frequently in short supply. Want to do your good deed for the day? Get in contact with a blood bank and squirt out a pint for your fellow humans. Check out one of our newest videos right here! Plus, even more Grunge videos about your favorite stuff are coming soon. Subscribe to our YouTube channel and hit the bell so you don't miss a single one.