Giving talks about poisons often results in being asked some worrying questions. I’ve been asked a few times recently about the plot of Strong Poison by Dorothy L. Sayers and if it is a plausible way of using arsenic to kill. What the questioners planned to do with the information in Sayers’s novel I didn’t dare ask.
In any case, I had to confess that I hadn’t actually read this classic work of crime fiction and had no idea about the feasibility of the plot. Recently, I decided to plug this embarrassing gap in my knowledge.
Arsenic is almost a by-word for poisoning; its easy availability from the 19th century to well into the 20th century, and symptoms resembling gastric conditions or food poisoning, made it a popular choice with poisoners. It is the almost too obvious choice for the murder mystery writer and so it is surprising that Sayers, an inventive plotter, would pick something so commonplace. It certainly gave Sayers the opportunity to show off her comprehensive knowledge of the poison, from details of how to obtain it, administer it and detect it, to name dropping real-life arsenic poisoners. But much of this would have been known toher readers: Sayers’s new take on an old poison is what makes her novel a classic.
The central mystery of Strong Poison is how two people can sit down for a meal and eat exactly the same things but one of them dies of arsenic poisoning while the other is unaffected. Sayers has been criticised for her detailed explanations of everything from advertising to campanology, and sometimes it might seem as if she is merely showing off her knowledge rather than advancing the plot, but it is the detail that makes Strong Poison a success. Every aspect of the deadly meal is gone into: who ate what, who drank what, who was present, and if any poison could have been surreptitiously slipped into one plate of food but not the other. But there are no chinks in the armour, no moment unaccounted for; if one person ate poison during the meal then so did the other person. How can arsenic kill one person but not another?
The key to the whole mystery comes to Sayers’s amateur detective, Lord Peter Wimsey, when he reading A Shropshire Lad, by A. E. Houseman in conjunction with three other more technical tomes. Although Sayers does not explicitly tell the reader which poem Wimsey has been reading, a later reference to Mithridates seems to indicate that one poem in the collection had particularly caught the detective’s attention: Terence, This is Stupid Stuff. The last verse tells of King Mithridates, who was terrified of being poisoned. To protect himself, Mithridates devised a concoction of over fifty toxins which he sampled daily to develop a tolerance to all poisons.
They put arsenic in his meat
And stared aghast to watch him eat;
They poured strychnine in his cup
And shook to see him drink it up:
They shook, they stared as white’s their shirt:
Them it was their poison hurt.
—I tell the tale that I heard told.
Mithridates, he died old.
Had one of the two characters eating Sayers’s poisoned meal been inspired by the Persian king and been dosing himself with small amounts of arsenic to give him immunity? Much of Mithridates’s life is the stuff of legend but added to more contemporary accounts of ‘arsenic-eaters’ a credible hypothesis begins to take shape.
In the middle of the 19th century stories emerged of people in Styria eating arsenic for their health. They claimed small lumps of arsenic, crushed between their teeth and swallowed, improved their complexion, made their hair strong and glossy and helped them breathe easier at high altitude or when doing strenuous work. Witnesses testified to their flawless “peaches and cream” complexions and apparent excellent health of the arsenic-eaters and the fad spread throughout Europe and beyond.
One interesting side-effect of an arsenic habit appeared to be immunity to arsenic’s poisonous effects. Volunteers were wheeled out in front of large crowds to consume huge doses of arsenic, well above a lethal amount, with no ill effects. The trick was not to drink any liquids. In Sayers’s novel the scientific explanation for this miraculous resilience was attributed to the body dealing with dissolved and solid arsenic differently. Unfortunately, though credible by 1930s standards, this is not exactly how the science works.
The Styrian arsenic-eaters were swallowing relatively large lumps of arsenic that would be difficult for the body to break up and dissolve in a way that could be absorbed easily into the body. Much of what they ate would have been excreted intact. Their apparent tolerance was an illusion. Had they eaten powdered or dissolved arsenic in the same quantities they would have suffered the same effects as anyone else, violent vomiting and diarrhoea and intense pain followed by death approximately three days later.
The small quantities that were absorbed into the body gave only the appearance of health. Bugs and bacteria that would cause skin blemishes were poisoned by the arsenic, clearing up the complexion. Over time, however, the arsenic would accumulate in the body resulting in poisoning. The first signs might be a slight discolouration to the skin which can develop into scaly brown callouses. Later, the hair may begin to fall out. Skin, hair and nails contain large amounts of sulfur to which arsenic bonds extremely strongly.
Enzymes in the body also contain sulfur and if arsenic bonds at these atoms it can disrupt the function of the enzyme. The effect this produces on the body depends entirely on which enzymes are being disrupted. Long term health effects of an arsenic habit can include high blood pressure, pains in the legs and stomach and cancer. The long-term prognosis for arsenic-eaters is not good.
Sayers’s science was spot-on by 1930s standards but the science has progressed. Reassuringly, the plot of Strong Poison isn’t a practical way of poisoning someone, let alone getting away with it. There is no way of developing a tolerance to arsenic through eating small regular doses. Eating the same amount of arsenic added to the same meal is most likely to kill either all or none of the people that eat it. It’s not a risk worth taking.
