An expert in plant toxicology has found traces of a rare plant poison in the stomach of Russian whistleblower Alexander Perepilichny, who collapsed and died outside his Surrey home in 2012 after warning that he had received death threats from the Kremlin.
The extremely poisonous species of gelsemium detected is known as “heartbreak grass”. Such an evocative name is bound to whet the imaginations of many the world over – poisons fascinate us all, especially when they have their roots in the natural world. Just think of the endless cases in literature, from Shakespeare’s Romeo and Juliet to Agatha Christie’s And Then There Were None. And a new exhibition centred on the allure of poisons has just opened in London.
No less than Sir Arthur Conan Doyle, the author of the Sherlock Holmes whodunnits, experimented with heartbreak grass. In a letter to the British Medical Journal sent on September 20, 1879, Conan Doyle recounted how a neuralgia led him to consume a tincture of gelsenium. He then decided to self-experiment on himself to see how much he could take without overdosing. He suffered from dizziness and severe diarrhoea as a result.
So what makes poisons so captivating? It could be the instinctive knowledge that we could all experience poisoning. Many of us will have spent several unpleasant hours courtesy of some contaminated food (usually meat); many of us will have had side-effects from prescription or recreational drugs; many of us will have reacted strongly to the bite of a mosquito or the sting of a wasp. All these afflictions are cases of poisoning: cases where our body cannot cope with an external substance.
The dose makes the poison
Conversely, we know that many poisons can heal when taken in the right amount: “the dose makes the poison,” as the adage goes. Although that aphorism is often attributed to Paracelsus (16th-century CE), the principles behind it were empirically observed well before, perhaps even from the beginnings of humanity. Animals can instinctively differentiate between poisonous and non-poisonous plants (although there is of course no foolproof method – individuals will die in the process), and humans are no different from other mammals in that respect.
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The botanical writings of the philosopher Theophrastus of Eresus (fourth century BCE) represent an important step in the theoretical definition of poisons. Theophrastus tells us that edible plants tend to be sweet to the taste; whereas poisonous and medicinal ones tend to be bitter. So the bitter taste of wormwood (Artemisia spp.) is indicative of its medicinal qualities when taken in the right amount and its poisonous ones when taken in excess. There are, however, exceptions to the “bitter taste” rule – dangerous exceptions such as mandrake root (Mandragora officinarum L.), whose taste is sweet. In small amounts mandrake can be used medicinally but in larger quantities it kills.
Then again, humans and other animals can build a resistance to some poisons by habituating themselves to them, that is, by taking increasingly large amounts of that poison daily. In the ancient Greek and Roman world, cow’s milk was primarily used as a purge, a means to empty the stomach and bowels. In other words, cow’s milk was a poison, albeit not a lethal one. Today, in the Western world, most people can drink relatively large amounts of cow’s milk without adverse effect, although the proportion of people who are – or claim to be – lactose intolerant is not negligible.
Another substance often used as a purge in Greek and Roman antiquity was hellebore. Theophrastus tells us the story of a drug-seller who boasted about his ability to eat sprigs of hellebore without being purged. Then came along a shepherd who turned the drug-seller into ridicule by publicly ingesting an entire bunch of hellebore sprigs.
The poison master
In French, the technical word for habituation to poison is “mithridatisation”, which is derived from the name of an ancient king: Mithradates VI of Pontus (134-63 BCE). He was one of the fiercest enemies of Rome, and no less than three wars – the Mithridatic Wars – were waged against him. There are several stories of alleged poisoning in Mithradates’s family; in particular, his father died in circumstances that are not entirely clear.
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Mithradates lived in dangerous times when dynastic killings, often by means of poison, were common. And so in preparation for his probable eventual poisoning, he started to take small doses of poison every day. At the same time, he worked on developing an antidote that would protect him. The success of that enterprise depended on gaining as much knowledge as possible about poisons and antidotes. The king therefore surrounded himself with famous physicians who informed him about the latest pharmacological discoveries. He also gathered plant knowledge from all his subjects. The story goes that he mastered well over ten languages and addressed all his subjects in their native tongue, thus gaining invaluable expertise from them.
Eventually, the king developed a particularly successful antidote. It was so effective that, when Mithradates was finally defeated by the Romans, and when he tried to take his life by ingesting poison, he failed to die, even though all his family members had succumbed to the effects of the deadly substance. Finally, the king asked one of his servants to kill him with a sword. How the mighty fall!
The Roman general who defeated Mithradates took hold of his specimen collections and writings and brought them to Rome. There they were translated into Latin, and the antidote of Mithradates, allegedly following the original recipe created by the deadly king, became one of the bestselling drugs of all time: Mithridatium, a remedy that allegedly treated all cases of poisoning and cured many diseases beside.
Laurence Totelin has received funding from the Wellcome Trust.
Authors: The Conversation