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from the pharmacist. In 1947, when the book was written, this compound was likely to have been dispensed as a solution of 260mg of atropine sulfate dissolved in one ounce (approximately 30ml) of water. This would be enough to kill an adult man if given in a single dose, but the prescription would be expected to last for a month if used daily for both eyes. The daily dose would be approximately 4mg per drop, roughly the level at which toxic symptoms might start to appear. The atropine sulfate obtained by the poisoner in The Cretan Bull would have been mixed with the cream, which wouldn’t have changed its appearance, apart from perhaps making it a little runny. Poirot suggests that the atropine sulfate was extracted from the medicine before being added to the cream. Extracting the atropine sulfate, or concentrating it, could easily be achieved by evaporating the water from the eyedrops to leave a solid residue. Face creams,or cold creams, are a mixture of oils in water, and if the poison was added as solid atropine sulfate it would dissolve in the water already present in the cream.
    It is difficult to establish the dose Hugh must have been receiving, as we do not know how big the tub of cream was, or how much he used per day. Hugh must have been exposed to a larger daily dose than that designed to treat his father’s eye condition in order to experience toxic effects. The amount of atropine sulfate absorbed through intact skin is usually very low, but the abrasive effect of shaving would have made the chemical far easier to absorb when the cream was applied to broken skin. As the poison took effect a rash appeared on Hugh’s face, which would have allowed even more atropine sulfate to be absorbed – and probably caused him to apply yet more of the tainted face cream. Poirot’s intervention and prevention of further poisoning saves Hugh’s life; from what we know of this chemical, we can expect that he would go on to make a full recovery, and marry his betrothed, Miss Diana Maberley.
    Notes
    25 The same effect is achieved by candlelight, because the pupil opens to allow more light into the eye to compensate for low light levels, hence the romance of a candle-lit dinner.
    26 Entitled Murder in Three Acts in the United States.
    27 Adding an acid to the alkali atropine will make the corresponding salt. For example, by adding hydrochloric acid, atropine chloride is formed.
    28 This is responsible for controlling automatic functions outside conscious control, such as the heart rate, salivation and certain reflex actions, such as coughing.
    29 Although l -hyoscyamine, one of the ‘hands’ of atropine, is increasingly used, probably because it has fewer side effects.
    30 Miosis is an excessive constriction of the pupil that can be caused by several medical conditions.
    31 This short story is part of a collection entitled The Thirteen Problems . This was called The Tuesday Club Murders in the United States.
    32 Hopefully in judiciously small quantities, to stop the pathologist from succumbing to the same poison. This is no longer considered a reliable method of identification.
    33 Mainly because Hitler couldn’t believe that the Allies didn’t have their own similar, but larger, stockpiles; the Allies did indeed have their own versions of organophosphorus-based chemical weapons, but again they were never used.

Sparkling Cyanide
    The Strongest Poison ever known
    Came from Caesar’s Laurel Crown…
    William Blake, Auguries of Innocence
    CYANIDE makes an appearance in no less than ten Agatha Christie novels and four short stories, where she uses it to bump off 18 characters. Christie had her murderers administer the poison in inventive and effective ways, including by injection, in drinks, in smelling salts and even in a cigarette. Her descriptions of the poison, the symptoms displayed by the victims and the possible sources of cyanide exhibit a high degree of accuracy. Rather than cataloguing the murders one after another,