A drop of blood can zip around your bloodstream in a minute or less.
So can poisons (snake venom, chemicals) and germs (viruses and bacteria). Every hour of every day, invaders surge through your blood vessels. Every hour of every day, your white blood cells and organs such as your liver and spleen battle them.
When a body is healthy, cells and organs easily knock out invaders. But sometimes even the best defenses aren’t strong enough to keep your own blood from harming or even killing you. Poisons can outnumber defenders, and germs can actually trick your cells into ignoring them. What kinds of invaders are in your bloodstream, and what happens when your defenses don’t work? What else can go wrong with your blood?
