Arsenic is one of the oldest and most well-known poisons in the world. It changed political dynasties and spawned the science of toxicology. It also might be responsible for two different movie monsters.
Arsenic is such a famous poison that it earned an affectionate little nickname — "inheritance powder" was what you slipped into dear old dad's drink if he was taking a long time to die and you wanted the house already. It was used by the Borgias to bump off their rivals and become the most powerful family in Rome. Many people speculate that it was behind the death of Napoleon. It was common enough, and enough of a threat, that its identification in bodily tissues was one of the first triumphs of toxicology in the 1800s.
That didn't stop the poisoners. Because arsenic was in everything from rat poison to paint colors to beauty products, it was easy to show that it was in a dead body, but impossible to prove than any single person had actually administered it. In fact, when Claire Boothe Luce was ambassador to Italy in the 1950s, she was accidentally poisoned when arsenic-filled paint flecks from the embassy dining room dropped into her food.
How did this deadly poison inspire two different monsters? Through a little process called arsenic mummification. Adenosine triphosphate, or ATP, is the fuel used for most cell activities. ATP helps cells with cell respiration, with making new structures and cytoplasm, and keeps muscle cells active. Arsenic stops the production of ATP. When it's administered in small doses over a long period of time, it causes creeping paralysis and confusion as muscle and nerve cells stop working. When it comes in a big dose, it causes massive cell death, leading to muscle cramps, diarrhea, and shock as cells die in droves and people start hemorrhaging.
It's not a pretty death, but once a person is cleaned up, they stay remarkably well-preserved. One of the reasons why early scientists were able to identify arsenic as a poison is it doesn't leave body tissues. It also doesn't allow tissues to fall apart; most of the bacteria that break down a body after death are poisoned by the arsenic right along with all the other cells. Since all the existing bacteria are dead, no new bacteria can move in, and arsenic remains throughout the body, it is uncannily preserved after death — a process known as arsenic mummification.
It's this arsenic mummification that inspired the earliest-known mummies. Thousands of years before the pyramids, people along Chile's pacific coast were mummifying their dead — especially the young dead. Scientists wondered where they got the idea, until they found natural arsenic in the water supply. The arsenic caused a high rate of miscarriage, still birth, and death among the young, who were most vulnerable to the effects. Bodies poisoned by arsenic would have been preserved naturally, leading the people to further and further refine the process of mummification. So seven thousand years ago, the first mummies sprang from a specific, and natural, poison.
Some people speculate that arsenic mummification also lead to the first zombie legends. A person is murdered by arsenic, and so dies with a legitimate grudge. Their corpse simply doesn't decay. It takes on a greenish cast, mold grows on the skin, but the body stays lifelike, even after years in the grave. This might be where the legends of the living dead come from. If a corpse is exhumed, and looks like it's been taking the air every night while the other bodies around it decay, it's not crazy to think that something supernatural might be going on.
[Via Speakeasy Science, The Scientific Study of Mummies, Dartmouth]