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The Insane Root

The Insane Root, passage from Gerard's Herbal
We left Macbeth and Banquo confronting the witches and their prophecies.
When they depart, we get the following exchange:
Banquo: “The earth hath bubbles as the water has, and these are of them, wither are they vanished?”
Macbeth: “Into the air; and what seemed corporal melted as breath into the wind, would they had stayed?.” “Were such things here as we do speak about?,” asks Banquo. “Or have we eaten on the insane root that takes the reason prisoner?”
Macbeth: “Your children shall be kings.”
Banquo: “You shall be king.”
Macbeth: “And Thane of Cawdor too; went it not so?” And soon after this, a messenger comes with the news that Macbeth has been named the Thane of Cawdor because the Thane of Cawdor has proved a traitor, he’s fought on the enemy’s side in the war and Macbeth has been given his title. We don’t quite know how Shakespeare staged the vanishing of the witches, maybe it was an effect with a trapdoor. Clearly there’s an idea of an instant disappearance, adding to their mysterious, magical, otherworldly quality. But the interesting line that I want to focus on, is when Banquo says, “Have we eaten on the insane root that takes the reason prisoner?”
They’ve already said to the witches, are you real or are you fantastical? Is this reality or is this something that comes from the imagination? And it would seem that in this line, Banquo is taking that idea further. The idea of the reason being taken prisoner. The idea of an irrational sight. But what does he mean by the insane root? A root, some kind of root vegetable, some kind of plant. Well, what this phrase takes us to, is the absolute centrality of plants, and customs and associations around plants and vegetable life in Shakespeare’s time. What I’ve got out now is called “Gerard’s Herbal”.
It’s the largest, and most beautiful, most comprehensive example of a Herbal, an account of all the plants available in Shakespeare’s time and what their qualities are. For each plant, Gerard has a picture, he gives the name and the Latin name, then he tells you the kind of place that the plant grows, the time of year that it flowers, the various different names of it, the temperature - the idea of whether plants are hot or cold. Rather strange idea to us but it’s related to the so-called Theory of the Humors, which we’ll talk about some more a little bit later - and then, crucially, Gerard lists, what he calls, the virtues of each plant.
And what he means by the virtues is, the things that can be done with the plant. Medicine, at this time, was fundamentally herbal medicine. What doctors did, was they gathered plants, they mixed them up. They worked with people called Apothecaries, whose job it was to create drugs, as we would now say. But these were all based on mixtures of plants, and on lore, associations of plants, legends about plants, but also the experience of how people reacted to different plant concoctions. This wisdom was handed down the ages and remained remarkably unchanged for many, many centuries. Now, scholars debate precisely what plant is being referred to by the insane root.
Some scholars think it’s a plant called hemlock, but the majority - and I incline to this view - think that what Banquo is referring to here is a plant called henbane, and, in particular , a kind of henbane known as black henbane. This is something that Gerard says can be used - certain parts of it can be used - in mitigating pain,
but he gives this warning: “The leaves, seed and juice taken inwardly causeth an unquiet sleep like unto the sleep of drunkenness, which continueth long, and is deadly to the party.” In a sense, what Banquo is saying, is have we inadvertently overdosed on henbane and are now having some kind of really bad trip, some kind of vision of this terrible thing, these witches that don’t really exist.
The idea that the mind might be disturbed and that a doctor, or a practitioner of herbal medicine, might not be able to help, is something that recurs deeply throughout the course of Macbeth. The insane root is only the first of a number of references to medicine and mental disturbance in the play.
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Shakespeare and his World

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