Guest Post by Laura Cooper
Poison hemlock (Conium maculatum) is one of the most notorious of poisonous plants. It’s best known as the poison that killed the philosopher Socrates, and may even be indirectly responsible for the deaths of quail eaters, but even this species has been used as a medicine.
Conium maculatum is in the family Apiaceae. Many species in this family resemble hemlock as they possess white flowers in umbels, branches of the stem which form a flat surface, and pinnate leaves, resemble parsely (Petroselinum crispum) and wild carrot (Daucus carota). This has lead to foragers accidentally poisoning themselves, but most are put off by the “mousy” or foetid odour and bitter taste. This and red spots that appear on the base of the plant in spring, traditionally gained when the plant grew at the base of Christ’s cross, are key identification features. It is a common “weed” globally, and was introduced as an ornamental to North America.
A vivid account of hemlock poisoning is given in Plato’s Phaedo, where his teacher Socrates is sentenced to death by consuming a “poison” known to be C. maculatum. After being given the poison, Socrates “walked about until […] his legs began to fail, and then he lay on his back […] the man who gave him the poison […] pressed his foot hard, and asked him if he could feel; and he said, No; […] and so upwards and upwards, and showed us that he was cold and stiff. And he […] said: When the poison reaches the heart, that will be the end. […] in a minute or two […] his eyes were set, and Crito closed his eyes and mouth.” The execution is an apt one for a philosopher, as he retained conscience throughout. However, the description may be idealised to preserve the dignity of Plato’s old teacher, as most hemlock poisonings involve vomiting and seizures in addition to the creeping paralysis.
Hemlock kills by a cocktail of similar chemicals, including γ-coniceine and coniine. Coniine affecting the nicotinic receptors on neurons first to stimulate the nervous system, causing seizures, vomiting and tachycardia. Later it may inhibit the central nervous system, causing brachycardia and paralysis.
One of the most sinister ways of being poisoned by a plant is the rare condition coturnism. It is caused by eating quail, Coturnix coturnix, killed in the Mediterranean whilst migrating north from Africa in the spring (but not when returning in the autumn). It is widely reported that this is due to the quail consuming the seeds of C. maculatum, but there is conflicting evidence. According to E. F. Jelliffe, hemlock drops seed in late summer and autumn, meaning quail migrating north in the spring cannot have eaten this seed. Therefore, the cause of coturnism is still a mystery.
But despite it’s notoriety, C. maculatum features in medieval household remedies. It’s powers of sedation are utilized in a recipe for an anesthetic known as dwale. The recipe involves boiling pig bile, three spoonfuls each of of hemlock juice, opium and henbane, bryony, lettuce and vinegar and adding this to half a gallon of wine. Drinking this would apparently allow a person to fall asleep and be “safely cut”, after which vinegar and salt to the face would revive them. Though the mixture seems effective at knocking a person out, it is questionable that the vinegar would be enough to revive them. However, there is no scientific evidence that “root of hemlock, digged i’ th’ dark” that the witches in Macbeth add to their potion contributed to Macbeth’s false imperviousness.