Henbane

Henbane is Hyoscyamus niger, and it is poisonous. That is not a caution attached to an otherwise useful plant; it is the central fact about it.

The active constituents are the tropane alkaloids, principally hyoscyamine, scopolamine and atropine, which are potent anticholinergics. They block the action of acetylcholine at muscarinic receptors, and the resulting syndrome is characteristic and severe: dilated pupils and loss of near focus, dry mouth and skin, flushing, racing heart, retention of urine, high fever, and a delirium marked by vivid hallucinations that the affected person cannot distinguish from perception. The classical mnemonic in emergency medicine runs blind as a bat, dry as a bone, red as a beet, mad as a hatter, hot as a hare. Deaths occur, and children have been poisoned by eating the seed capsules.

The plant is unmistakable at close range and easy to overlook at a distance: sticky, hairy, greyish, with dull cream flowers netted in purple veins and a dark purple throat, and a strong unpleasant smell when bruised. It grows on disturbed ground, middens and old walls.

Henbane belongs to the Solanaceae, the nightshade family, alongside belladonna, datura and mandrake, and alongside the potato, tomato and pepper. The family is one of the most pharmacologically consequential in the world, and its toxic members are toxic by the same chemistry that makes them medically interesting. Hyoscine, still in clinical use, is a henbane alkaloid.

The delirium is the feature that matters most for the plant's history. Unlike the hallucinations produced by other classes of drug, anticholinergic delirium is not recognised as unreal by the person experiencing it: conversations are held with people who are not present, and the memory afterwards is fragmentary or absent. That is a specific and well-documented clinical picture, and it is directly relevant to what the plant was later said to do.

Culpeper gives henbane to Saturn, and it is the least strained attribution in his book. Saturn in the planetary scheme is cold, heavy, deadening and associated with death; henbane is a narcotic poison. The signature and the fact agree for once, and Culpeper says so without his usual argument.

The plant's more famous association is with the flying ointment of the witch trials, a fatty preparation of tropane-bearing plants, most often given as henbane, belladonna and mandrake, said to have been rubbed on the body or on a staff and to have produced the sensation of flight. The pharmacology here is sound in principle: tropane alkaloids are absorbed through skin, and scopolamine delirium characteristically involves sensations of flying and falling and encounters with figures that seem entirely real. Several twentieth-century researchers tested such preparations on themselves and reported exactly that.

What is much weaker is the historical claim that this was a widespread practice rather than a widespread accusation. The ointment recipes come overwhelmingly from demonological literature written by prosecutors and from confessions extracted under torture, which is precisely the class of evidence that manufactures whatever it is looking for. Ronald Hutton and others have argued that the ointment is better understood as an element of the learned stereotype of the witch than as a reconstructable folk technique. The chemistry would work. Whether anyone was actually doing it, at scale, is not established.

Henbane has a long documented medical history in exactly the role its chemistry suggests: as a soporific and a pain-deadener, used when there was nothing better, by people who knew it could kill.

Dioscorides describes it in the De Materia Medica in the first century, distinguishing the black, yellow and white forms and warning that the black produces madness and sleep. Arabic and medieval European medicine used it in the soporific sponge, a preparation of henbane, opium and mandrake soaked into a sponge and held to the face of a patient before surgery. That is a genuine and serious pre-modern anaesthetic tradition, and its problem was always the same: the margin between a dose that dulls and a dose that kills is narrow, and neither the concentration in the plant nor the dose delivered could be controlled.

Henbane also has a documented use in brewing. Before hops became standard, gruit ales in parts of northern Europe were bittered with mixtures of herbs, and henbane is named among them. The German Bilsenkraut is preserved in the place name Pilsen in one popular etymology, which is disputed and should not be relied on.

The English name is straightforward and grim: bane of hens, from the plant's reputation for killing poultry. Old English forms are attested from well before the Norman conquest, and henbane is among the plants named in Anglo-Saxon medical writing.

Henbane has a documented criminal history to match. Hawley Harvey Crippen was convicted in 1910 of poisoning his wife with hyoscine, in a case that turned on some of the earliest forensic toxicology admitted in an English court, and that was the first murder investigation in which a suspect was apprehended by wireless telegraph. Shakespeare's hebona or hebenon, poured in the ear of Hamlet's father, is often identified with henbane, though the identification is disputed and yew and ebony have also been proposed.