Foxgloves, ‘naughtie humours’, and xanthopsia

At last, my foxgloves have come into flower! I have been waiting since the middle of last summer, when I first thought up the idea of painting the Poison Flower Fairies.

Foxglove in my garden (with a few wallflowers behind it.)
Foxglove in my garden (with a few wallflowers behind it.)

Digitalis Purpurea, to give them their scientific name (regardless of the fact that many of them are not in fact purple), are famously poisonous, famously useful in medicine, and were gone and over for the year, before I thought of this little painting series. So were the opium poppies.

So I have had to wait a full cycle for the next year’s flowers. Meanwhile I have had plenty of time to look up interesting things about Foxgloves, with particular regard to their toxicity.

Digitalin is the name of the toxin extracted from foxgloves. I say toxin, of course like lots of poisonous things, in the correct dose it is a very useful thing, and has very valuable medical properties.

According to The university of Bristol’s ‘Molecule of the Month‘, digitalin has been used for the treatment of cardiac conditions since its discovery by a Scottish doctor, William Withering, in 1775. Apparently, he tracked this down as the constituent of a gypsy remedy, used on a patient who was beyond his help. Having discovered the use of this plant, he had amazing success with it and by the age of 46 he’d become the richest doctor outside of London.

William Withering did not discover the medical potency of the plant, it’s been known (according to Molecule of the Month) since at least the Dark Ages. But I did a little further digging into this story and found, curtsey of, the entire text of Withering’s ‘An Account of the Foxglove, and some of it’s Medical Uses with practical remarks on Dropsy and other Diseases‘. (Preface dated 1785) This historical book has been photographed in its entirety, rather than simply typed out, which makes it at once a lot more real, and a little hard to read.

Title page from William Withering's book on Foxgloves. Image courtesy Missouri Botanical Garden,
Title page from William Withering’s book on Foxgloves. Image courtesy Missouri Botanical Garden,

Interestingly, by Dr Withering’s own admission, he did not start using it for the treatment of cardiac complaints, he speaks of its use as a diuretic, to treat dropsy (an ‘outdated term for a variety of conditions associated with the accumulation of fluid’:, and mentions in the introduction its use as a treatment of wounds, ulcers, consumption and ‘scrophulous tumours’.

[This latter is also curiously referred to as ‘The King’s Evil’ because (as I now also discover) of the belief, and practice since the time of Edward the Confessor (1003/4-1066), that this condition could be cured by the touch of the rightful king of England. Sadly, English monarchs seem to have stopped this practice with the end of the reign of Queen Anne (died 1714), though the last French monarch to do this was King Charles X in 1825.(]

There is a great deal of detail in Dr Withering’s book, in now charmingly antiquated English, and I thought I would quote you just a little snippet of it:

‘Doctor Baylies, physician to his Prussian Majesty, informed me, when at Berlin, that he employed it with great success in caries, and obstinate sore legs.
Dyspnoea Pituitosa Sauvages i. 657. – “Boiled in water, or wine, and drunken doth cut and consume the thicke toughness of grosse, and slimie flegme, and naughtie humours. The same, or boiled with honied water or sugar, doth scoure and clense the brest, ripeneth and bringeth foorth tough and clammie flegme, It openeth also the stoppage of the liver spleene and milt, and of the inwarde parts” ‘

…I love ‘obstinate sore legs’ and ‘naughtie humours’, though I hope I haven’t just put you off your breakfast!

Page xviii from William Withering's book on Foxgloves. Image courtesy Missouri Botanical Garden,
Page xviii from William Withering’s book on Foxgloves. Image courtesy Missouri Botanical Garden,

Anyway to cut a long book very short, it appears from Dr Withering’s own writings that the ‘gypsy’ was in fact an ‘old woman of Shropshire, who had sometimes made cures after the more regular practitioners had failed’ and that the cure was a ‘family receipt for the cure of the dropsy’ that Dr Withering came upon in 1775. And in fact, though I have not read through the entire book, it seems largely concerned with dropsy and diuretics and not at all about cardiac complaints, though a medical friend of mine tells me that ‘dropsy’ would be an indication of cardiac problems too: perhaps Dr Withering thought this was to obvious to mention!

Illustration from William Withering's book on Foxgloves. Image courtesy Missouri Botanical Garden,
Illustration from William Withering’s book on Foxgloves. Image courtesy Missouri Botanical Garden,

One last word from Dr Withering I wanted to add: his reasons for, reluctantly, writing the book in the first place: ‘The use of the Foxglove is getting abroad, and is is better the world should derive some instruction, however imperfect, from my experience, than that the lives of men should be hazarded by its unguarded exhibition, or that a medicine of so much efficacy should be condemned and rejected as dangerous and unmanageable’. It would appear we do have William Withering to thank for lifting Foxgloves into the spotlight of medical practice, if not necessarily for it’s original discovery.

Digitalin is actually a mixture of molecules. For cardiac medicine, two of the important things that can be extracted from Digitalin are Digitoxin and Digoxin…. and now here, I came upon another interesting story. They work by ‘increasing the intensity of the heart muscle contractions but diminishing the rate’  (, but Digoxin can also cause a rare side effect in long-term use, called Xanthopsia.

Xanthopsia is a disturbance in colour vision, such that the person suffering from it sees the world as if through a yellow filter, possibly also with coronas around lights. There is a curious theory regarding the Dutch painter Van Gough and Digitalin: He was treated by a doctor Paul-Ferdinand Gachet, apparently well known for his writings on the careful use of Digitalin as a treatment for various medical complaints, and he may have treated Van Gough with this as treatment for mania and / or epilepsy. Van Gough made paintings of his doctor twice, and in each case he is depicted holding a foxglove. The theory is that this may account for the predominance of the colour yellow and the haloes around lights in Van Gough’s paintings. There’s a substantial article on the subject here:

Portrait of Dr Gachet by Vincen Van Gough
Portrait of Dr Gachet by Vincen Van Gough, image from:

I was quite taken by this theory when I first heard it, because it brought my meanderings through poison plants right back to painting again. Unfortunately the balance of opinion is that it is an engaging theory backed up by little evidence, and it may as easily be that Van Gough just liked yellow. However, one thing occurs to me: if Van Gough saw the world as through a yellow filter, then surely all of his paints would look more yellow already, so he wouldn’t need to paint more yellow, to get the same effect?

The Night Cafe by Vincent Van Gough
The Night Cafe by Vincent Van Gough:

All the same, I feel that the flower Fairy of the Foxglove could do with a pair of yellow-tinged spectacles. And on that note, I conclude the things I found out about foxgloves, and shall think about actually getting on with some painting of them…

(By the way, some of the sources refer to the extract as ‘Digitalin’ and some as ‘Digitalis’ – I have picked the former as distinct from the actual plant.)

Close-up of Foxglove flowers (some more from my garden)
Close-up of Foxglove flowers (some more from my garden)


  1. […] As I said in the first post about this painting, she has an old-fashioned stethoscope, because of the plant’s remarkable potency as a heart-drug. What I didn’t explain were the yellow glasses. This is an allusion to a curious side-effect that has been known to occur in long-term usage of the plant as a drug: a disturbance of the vision called Xanthopsia, where the sufferer sees the world as if through a yellow veil. I posted some time last year about the use of foxgloves, including a curious theory about foxgloves and van Gough’s yellow paintings: […]

  2. […] If you’d like to read more, I posted a lengthy piece on my blog, which will also explain why she is wearing yellow-tinted glasses: […]

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