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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Saturday 5th November 2011

Time for another dip into the archives of the Royal Society’s Philosophical Transactions. 30th October On the last visit, I wrote about Oenanthe crocata, hemlock water dropwort, but forgot to discuss one aspect of the stories of that plant. I’ll correct that today.

Not that hemlock is the subject for this item. Instead it is an evergreen shrub that many people have in the garden without ever considering that it is poisonous. Prunus laurocerasus, cherry laurel, is in the same genus as plums, cherries, peaches and other well-known fruits so discovering it can kill may be surprise.

On the plant page in the A to Z section of this website, I give some details of its use, during the 19th century to intentionally cause harm, both murder and suicide, but, according to the Philosophical Transactions, its ability to poison was not appreciated until the early part of the 18th century and, even then, its power was disputed.

Prunus laurocerasus, cherry laurel

Prunus laurocerasus, cherry laurel

In 1731 a Dr Madden of Dublin wrote to the secretary of the Royal Society to tell of two fatal poisonings caused by laurel water. Dr Madden explains that water distilled from the leaves of Prunus laurocerasus has the smell of almonds and is used by cooks as a way of imparting that flavour to their baking. He also says it is common to prepare a drink made up of one part laurel water to four parts brandy.

The poisonings occurred in September 1728, when a servant was given a bottle of laurel water by her mistress. She passed it to her mother, Anne Boyle, who, in turn, gave it to her sister, Frances Eaton, who ran a shop. It would seem that somewhere along that chain any knowledge of the need to dilute it was lost and Frances poured a glass, about two ounces, for Mary Whaley, a customer who drank two-thirds of it straight. Frances finished it off.

About fifteen minutes later, and in a different shop, Mary complained of a stomach ache and then lost the power of speech. She was taken home where she died within the hour but without any vomiting or purging or convulsions. Frances summoned Anne to tell her what had happened but Anne claimed it could not be the laurel water and drank about five spoonfuls to prove it was harmless. She very soon died without exhibiting any symptoms of poisoning.

Frances felt no ill effects from what she had drunk but made herself vomit, as a precaution. She suffered no poisoning. By the time Dr Madden heard of what had happened Mary Whaley had been buried. He unsuccessfully tried to get agreement from Anne’s family to cut her open for examination. News of these two deaths brought word to Dr Madden of an incident in Kilkenny, four years earlier, where a young man mistook laurel water for another beverage and drank a whole bottle, dying within minutes.

As a result of these cases, Dr Madden conducted a number of experiments on dogs using various doses and delivery methods. Though not reported in the three human poisonings, the dogs frequently exhibited convulsions that Dr Madden likened to epilepsy. He performed post mortem examinations on the dead animals and concluded the poison created a muscle pressure that prevented blood in the veins being returned to the heart.

Prunus laurocerasus, cherry laurel

Prunus laurocerasus, cherry laurel

He also experimented with water distilled from the leaves of Taxus baccata (yew), Buxus sempervirens (box) and Laurus nobilis (bay or laurel) but produced no ill effects with these.

There is a note in the journal, following Dr Madden’s letter, saying that a Dr Rutty, also of Dublin, had contacted the Royal Society to say that a number of people had conducted similar experiments on dogs and some of these had involved trying to find an antidote. It was found that milk proved to be effective but Dr Rutty could not recall details of the quantities of poison and antidote used.

There appears to have been some disagreement about the danger posed by laurel water with some people saying they had used it in place of black cherry water with no problems. Partly as a result of these disagreements, a later edition of the journal reports on a series of tests on dogs conducted, by the secretary to the society, in August 1731 where different strengths of laurel water were prepared. Dr Mortimer concludes that small doses of low strength laurel water may not be instantly fatal but, he believes, long-term use must be ‘unwholesome’. He mentions a case, without giving details, where a married couple who daily drank brandy with Prunus laurocerasus berries infused in it had, after several years, lost the power of speech and died.

The final mention of laurel water is a short letter from Dr Rutty, written in 1732 but appearing in the journal for 1739-41, expressing concern that people are still claiming that laurel water is harmless. He says that an 18-year old girl died within minutes of drinking less than two spoonfuls of laurel water.

It does seem, however, that laurel water went out of favour as a flavouring and that, by the 19th century, it was well-understood to be a source of hydrocyanic acid and was used, in at least one instance, as a murder weapon.

Today, however, it doesn’t seem to rank that highly in the public consciousness about poisonous plants. Very few people think of it as a concern in the garden and, certainly, I’ve never heard of anyone removing cherry laurel in the way that you hear of people removing a laburnum tree ‘because of the children’. Yet, I can’t point to a single fatal poisoning from laburnum.

And that’s what I meant to discuss when I wrote about Oenanthe crocata at the end of October. Do poisonous plants have fashions so that public awareness of them is not related to their actual harm caused? Like the cherry laurel, hemlock water dropwort is not a plant many people readily call to mind when asked to name potential killer plants.