A is for Arsenic (35 page)

Strychnine would become a popular choice for Christie, and it makes an appearance in four further novels and five short stories, killing a total of five characters. Christie really makes the most of this poison in
The Mysterious Affair at Styles
, and she takes every opportunity to show off her extensive chemical knowledge.

The strychnine story

Strychnine is a plant alkaloid, an odourless solid with a very bitter taste. It forms long, thin, colourless crystals that are poorly soluble in water (1g dissolves in almost 6.5 litres). The compound is obtained from the plants of the genus
Strychnos
. There are many
Strychnos
species, which grow in the warm regions of Africa, America and Asia, and several of them contain strychnine, but the compound is most abundant in
Strychnos nux-vomica
, a tree native to India. Strychnine is found in the large, disc-like seeds of the plant,
⁹⁰
and it can be extracted relatively easily.

In regions where the plants are native, the poisonous properties of strychnine have been known for centuries, and extracts of the plants have been used as pesticides. In India strychnine is still used in ‘hudar' capsules to elevate blood pressure, whereby the seeds are soaked in water or milk beforehand to reduce the toxicity; taking strychnine might put your body under sufficient stress to raise blood pressure, but this is a consequence of the symptoms, rather than a
direct result of the action of the compound (there are other, more reliable, ways of controlling blood pressure).
Strychnos nux-vomica
also crops up in homeopathic remedies today, though the extremely high dilutions used in homeopathy mean that anyone taking these remedies is unlikely to be poisoned. Strychnine's use in conventional medicine was on the wane by the time that Christie wrote
The Mysterious Affair at Styles
in 1916, and by a few years later it had disappeared completely.

Strychnine can be inhaled or injected but it was normally administered orally, whether for criminal or medical intent. To improve the solubility of strychnine in water it was usually converted to a salt. This does not affect the toxicity of the compound, but it does make it easier to administer. When swallowed, strychnine salt is not absorbed from the acidic environment of the stomach, but is readily taken into the body through the walls of the small intestines. Once it has passed into the bloodstream strychnine can be easily distributed throughout the body. The target site for strychnine is, as so often in toxicology, a receptor in the nervous system.

How strychnine kills

Strychnine acts on the central nervous system (CNS), the network of nerve cells that send, receive and coordinate messages around the body. Signals that control voluntary movements are sent along motor neurons. These are cells that form a fine strand, the axon, just a few micrometres (a millionth of a metre) across. An axon extends out from the main body of the cell carrying electrical signals, and can be more than a metre long. Motor neurons stretch from the spinal cord out to the extremities of our body. The junctions between motor neurons are known as synapses. Chemical signals, or neurotransmitters, are released from the end of one neuron; they cross the gap and bind to a receptor on the next neuron, triggering a pulse of electric charge to transmit the signal further. The signal will terminate at a muscle, where
neurotransmitters cross a synapse to cause the contraction of the muscle fibre.

At rest, the inside of a nerve cell is more negatively charged than the outside; it is a switch in this polarity that is the source of the electrical signal passing down the axon. The neurotransmitter that crosses the synapse to trigger the electrical pulse in the connecting nerve is acetylcholine; another chemical, glycine, is released to counteract this effect. When glycine binds to receptors on a nerve it increases the flow of negative charge into the cell, making it more difficult for the nerve to produce a signal. This is an important control measure (like a system of brakes), ensuring that the nerve does not fire at the slightest provocation.

Strychnine binds to the glycine receptor three times more effectively than glycine does. By blocking the glycine receptors, the moderating effect of glycine is effectively switched off; the nerve will now fire at the smallest trigger (the brakes are disabled, and the system careers out of control). The muscles
connected to the motor neurons will contract fully, and for extended periods, at the slightest stimulation.

A motor neuron. The switch is polarity inside the cell is the cause of the electrical signal that passes along the length of the axon.

In humans the muscles of the back tend to be stronger than those on the front of the body; strychnine causes its victims to arch their backs, with the whole body resting only on the back of the head and the heels. In some cases the muscle spasms affect the stomach muscles and throw the victim forwards into a curled position or, if the side muscles are affected, rapid side-to-side convulsions can be seen. When
all
the muscles are affected, the arms are held rigidly at the side of the body, with the muscles in the face contorted to give the victim a sardonic grin, and the eyes bulging and flitting from side to side.

Although the primary effects of strychnine are on the motor neurons, the compound also affects the neurons in the cortex of the brain. The victim is conscious throughout; their senses and awareness of their situation are heightened by the strychnine increasing the sensitivity of the nerve endings in the brain. In the roster of truly appalling poisons, strychnine must rank close to the top of the list.

Symptoms appear between 15 and 30 minutes after strychnine's ingestion. They start with a tingling and twitching in the muscles. There may also be nausea and vomiting. As the symptoms progress, the muscle spasms become more violent, and eventually waves of muscle spasms bring the whole body into convulsion. Attacks of convulsions are interspersed with periods of relative calm. Victims often have a very red complexion because their muscles are working so hard, burning up oxygen at an incredible rate. For the victim this is exhausting, and the sufferer rarely survives more than five such attacks, with death occurring between one and three hours after ingestion of the poison. Death is caused by asphyxiation, as the muscles controlling breathing are affected.

Is there an antidote?

The effects of strychnine on the body are so dramatic that death usually occurs rapidly, so any treatment has to be given quickly. There is no specific antidote for strychnine, but there
are ways of alleviating the symptoms. Morphine can be given for pain relief and sedation, but it is most important to treat the convulsions. Muscle relaxants will stop these, allowing the body to process and excrete strychnine without adverse effects.
⁹¹
Today there is a choice of anti-convulsion drugs, because of their application in surgical procedures as well as in emergency treatment. Diazepam (also known as Valium) would be the preferred choice when treating strychnine poisoning, with the patient being supported with artificial respiration to maintain breathing. Diazepam was not available until 1963, so the choices available in 1920 would have been more limited. Other barbiturates would have been accessible, though, and these would have been the recommended treatment for strychnine poisoning at the time.

There is one compound that is a very effective muscle relaxant, and its ability to counteract the effects of strychnine has been known since 1850. Curiously, it is found in a plant of the same genus,
Strychnos
. The infamous arrow poison, curare, is an extract of
Strychnos toxifera.
It contains the alkaloid
d
-tubocurarine (so named because it was extracted from a tube used to store arrow poison).
d
-tubocurarine works in a similar way to strychnine, by blocking neurotransmitter receptors in motor neurons, but in this case the neurotransmitter in question is acetylcholine rather than glycine. The binding of acetylcholine to its receptor is the signal for the nerve to fire. When the acetylcholine receptor is blocked the nerve cannot fire, and the muscles relax (so this is the direct opposite of strychnine's blocking of glycine receptors). An account of the use of
d
-tubocurarine in anaesthetic practice was first published
in 1942, though it did not become standard practice in Britain until the 1950s.

Activated charcoal can also be administered to prevent further absorption of strychnine into the body. Administering activated charcoal is now a standard procedure when dealing with patients who have overdosed on a wide range of compounds, but the procedure has been recognised since the 1830s. In 1831, in a dramatic demonstration in front of his colleagues at the French Academy of Medicine, the pharmacist P. F. Touery swallowed ten times the lethal dose of strychnine mixed with charcoal. He and his colleagues waited several hours for signs of poisoning to develop but none were observed.
⁹²

Some real-life cases

Strychnine has been used many times in poisonings; it is listed third in the top ten poisons by number of criminal cases, behind only arsenic and cyanide. It has been used in some highly creative ways, with cunning often required to disguise the taste or to ensure that the victim swallows the lethal dose in one gulp.

One real-life case of murder with strychnine bears some striking resemblances to the method used in
The Mysterious Affair at Styles
. This happened in 1924, four years after the publication of the novel. It involved a wireless operator, Jean-Pierre Vaquier, who had travelled to England in pursuit of Mrs Mabel Jones, with whom he had fallen desperately in love. The couple had met and begun an affair in France, where Mrs Jones was convalescing after an illness. Mabel returned to England and to her husband, Alfred, the proprietor of the Blue Anchor Hotel in Byfleet, Surrey, who had stayed in England while his wife was recuperating.

When Vaquier arrived in England he went to stay at the Blue Anchor Hotel, and the affair continued under Alfred's
roof. Alfred was in the habit of drinking a little more than was good for him, so he regularly took bromide powders to counteract the effects of alcohol. He would take a dose of these powders from a blue bottle kept on a shelf in the hotel bar each morning, and dissolve it in a glass of water.
⁹³
One morning he added a dose from the blue bottle to a glass of water as normal, but he remarked that the powders did not fizz as they normally did. He drank down the mixture in one gulp regardless, and exclaimed how bitter it was.

Mabel Jones looked in the blue bottle and saw some long crystals amongst the usual powder. She tasted the crystals, and noticed the bitter flavour. She gave her husband some salt water to make him sick, and some tea with soda to try to counteract the effects of whatever it was he had swallowed. It was to no avail. Soon after, Alfred complained of numbness and of feeling cold. He went to bed and a doctor was called. By the time the doctor had arrived Alfred was in the midst of agonising convulsions. At 11.30 a.m., an hour and a half after drinking the poison, he was dead.

The circumstantial evidence against Vaquier was pretty strong. He certainly had a motive to dispose of Alfred, and he also had an opportunity, although no one saw him add strychnine to the blue bottle of bromide powders. When the bottle was recovered by police it had been washed out, but tests on the residual water inside the bottle confirmed the presence of strychnine. Vaquier had purchased strychnine, among other compounds, under the pretext of using it for wireless experiments. He had signed the poison register, but used a false name. A wireless expert was called to testify at the trial, and he confirmed that there were no known applications of strychnine in this field. Vaquier was found guilty and hanged; it is not recorded if Jean-Pierre Vaquier was a fan of Agatha Christie novels.

Christie cannot be blamed for the popularity of strychnine in murders anyway. There had been plenty of cases to inspire
would-be poisoners and murder-mystery writers before
The Mysterious Affair at Styles
was published. The most famous of these is probably that of Dr Thomas Neill Cream, a medical doctor who, in 1892, murdered four women. Cream had already served a sentence for one murder and was a suspect in the investigation into another, with both of these occurring in the United States. On his release he travelled to England, and within weeks of arriving in London began poisoning prostitutes. After meeting each of his victims he persuaded them to swallow a pill, which he said would improve their complexion. The pills in fact contained a lethal dose of strychnine, and the women died in agony hours later.