Today I am welcoming Atropa belladonna, also known as belladonna, nightshade, deadly nightshade, or tasty black berries if you like eating poison. They belong to the Solanaceae, or nightshade family, which also includes tomatoes, potatoes, and aubergines, as well as the much less deadly black nightshade. Fun fact: for a long time, people wouldn't eat tomatoes because they were thought to be poisonous.
As the name "deadly nightshade" implies, the plant is very dangerous for human consumption. However, its Latin name doesn't quite say the same. Linnaeus (commonly referred to as the father of modern taxonomy) named it Atropa, after one of the three fates from Greek mythology who was responsible for ending someone's life - not too surprising. However, the name belladonna comes from the Italian word for beautiful woman.
Why? Well, during the Renaissance, women would put the juice of these berries in their eyes to dilate their pupils and "make the eyes appear more seductive" in the words of Wikipedia. Interestingly enough, the dangerous side of it was known far before that, since Ancient Rome at least. While being used as a poison, it also features in multiple folk medicines. It would appear the stories of radium, arsenic, and Botox are coming back. Interestingly enough, the berries aren't the most toxic part of the plant and are purportedly quite sweet, which makes sense if you think about how many fruiting plants have evolved to spread. The root is the most dangerous part to consume, and to me it looks like the berries are only poisonous because the entire plant is quite poisonous.
Now, let's delve into why nightshade actually dilated their pupils.
The group of toxins found in nightshade but also much of the Solanaceae family in general is known to cause hallucinations. If you're familiar with Agatha Christie, you might recognize one of these: atropine. It's the murder weapon in the short story "The Thumbmark of St. Peter" and was (and can be) found in eyedrops. Atropine messes with smooth muscles and the parasympathetic nervous systems, and dropping it in your eyes dilates the pupils by preventing the iris from contracting. It's commonly used in optometry for this property. Unfortunately for someone who consumes it, smooth muscles are responsible for your involuntary functions, such as heart rate. As you can imagine, a heart that no longer contracts is not good at keeping someone alive. Anything controlled by smooth muscle(s) including breathing can be affected, and dizziness, slurred speech, headache, delirium, and headaches are common. The problem is the heart is one of those organs you really want to keep functional. Fortunately, if you catch it in time, atropine poisoning can be treated. This is especially useful if you think about how many children might mistake deadly nightshade for tasty berries, especially if they are sweet.
A nice mnemonic for atropine poisoning is "hot as a hare, blind as a bat, dry as a bone, red as a beet, and mad as a hatter" which I think is quite fun and a succinct summary of the dangers of atropine - minus death, of course.
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