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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Sunday 1st January 2012

I’ve been catching up with the Royal Institution Christmas Lectures broadcast over three evenings on BBC Four. I’ve watched this annual lecture series, off and on, for about as long as it has been televised though I did miss most of them when, for a time, they were broadcast on a commercial station so had the apparently mandatory ‘coming up in the next part’ before each advert break.

Happily, they are back on the BBC and free from the interference of TV ‘language’. Or, rather, almost free because I can’t help noticing that the BBC and the listings magazine I have refers to them as the ‘Christmas Lectures’ whereas the lecturer, correctly, welcomed the audience to the ‘Christmas Lectures for Children’.

I can only assume that someone at the BBC decided that an 8pm broadcast for something with ‘for Children’ in the title wasn’t a good plan. But, it is being for children that gives there programmes their special nature. The lecturer has to address the subject in a way that will engage the interest of children from about eleven upwards and stimulate their interest in science.

This year’s lecturer was Professor Bruce Hood and his subject was the human brain. He began the first lecture by showing a real human brain, donated by someone who wanted to try and be useful even after death, and finished the final lecture with some examples of how the brain filters the information it presents to us consciously.

The lectures involved a number of re-enactments of experiments that led to important discoveries about how the brain develops and grows and works and Prof Hood went to the trouble of explaining that these experiments had been conducted under properly controlled conditions but, even so, the more chaotic situation of a lecture room full of children was able to reproduce the results.

There was quite a lot about the importance of the eyes in social relationships with the professor demonstrating that we can tell the difference between a real smile and one that is false because of the difference in the eyes even though we aren’t consciously aware that we have looked at the eyes when we looked at a smiling face.

He also used a fancy camera set up to show that a volunteer asked to look at a section of the audience looked first at their eyes, again without conscious effort.

But, the reason for writing about this here, is that the Prof. Hood also showed two apparently identical photos of his own face, side by side, and asked the audience which seemed more friendly. When the overwhelming majority picked the right-hand photograph he explained that it has been digitally enhance to make his pupils appear more dilated and said that research had shown that humans respond more to dilated pupils.

Now, I know these were science lectures but I rather wish he had taken a few seconds to explore the history of this effect and, as a result, perhaps have engaged the attention of students of history or art and shown that not all mysteries are to do with scientific discoveries yet to be made.

Atropa belladonna, deadly nightshade

Atropa belladonna, deadly nightshade

Atropa belladonna, deadly nightshade, contains atropine a substance that causes the pupils of the eye to become dilated. It will have this effect if ingested but it is more often used topically by putting a couple of drops directly into the eye to cause the dilation without the other effects such as hallucinations. The name ‘belladonna’, meaning ‘beautiful lady’ is said to come from the practice of women in Venetian society using it to make themselves more attractive to potential husbands. It is sometimes said that the name comes from the idea that the plant would come to live as a beautiful temptress but that story seems to be one of Mrs Grieve’s many inventions in her ‘A Modern Herbal’.

So the fact that Venetian women knew that dilated pupils added to their attractiveness long before anyone had studied this in a lab shows that history can still be fascinating and mysterious. How was this discovered? When?

I said it also had the power to excite interest in art and art history. That is because of what is, probably, the most famous portrait ever painted, Leonardo da Vinci’s ‘Mona Lisa’. If you are lucky enough to be visiting Paris make sure, during the very short time you get to look at the painting, that you look closely at the eyes. If you are not visiting Paris, try and find a really high quality image online and you should be able to see that the model, believed by many to be Lisa Gherardini, wife of Francesco del Giocondo has dilated pupils.

What Prof Hood didn’t stress, this was after all a lecture to children, was that dilated pupils seem to be an indication of, at least, sexual interest and may indicate actual physical arousal.

So, the Mona Lisa’s dilated pupils throw up three questions. Did Leonardo realise that painting his model with dilated pupils would enhance the attractiveness of the finished work? Did the model know that dilated pupils would make her more attractive and, therefore, used some juice from Atropa belladonna before this important sitting?

Or, was she actually sexually aroused by the presence of the painter leading to her pupils, naturally, betraying her state? We’ll never know but it shows that an apparently lifeless painting from the 16th century still has secrets to fascinate young minds. 


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